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[vsnet-grb-info 42051] EP260306a: Einstein Probe detection of an X-ray transient
by GCN Circulars 06 Mar '26

06 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43930 SUBJECT: EP260306a: Einstein Probe detection of an X-ray transient DATE: 26/03/06 02:47:52 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> G.L. Huang, Z.X. Li (IHEP), H. Zhou (PMO, CAS) and Z-.X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260306a. The transient triggered EP-WXT (ID: 01709258759) at 2026-03-06T01:29:20 (UTC). The WXT position of the source is R.A. = 145.955 deg, DEC = 15.685 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 145.9478 deg, DEC = 15.6963 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). The location of the reported optical counterpart (GCN 43929) is consistent with the location of the uncatalogued X-ray source detected by FXT. Further information will be updated when the telemetry data is received. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43930. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42050] The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
by GCN Circulars 06 Mar '26

06 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43929 SUBJECT: The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart DATE: 26/03/06 02:31:14 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> Wenxiong Li, Runduo Liang (NAOC), Iair Arcavi, Ido Keinan (TAU), David Sand (U of Arizona) We observed the position of the EP/WXT trigger 01709258759 with a Las Cumbres 1m telescope at McDonald Observatory, Texas, 20 mins after the Einstein Probe WXT trigger. We took 2x300s exposures in the broad optical w band. We find an uncataloged source at RA=145.9490, Dec=15.6937 within the EP/WXT error circle and measure the following preliminary photometry calibrated to the r band: MJD 61105.08 Mag 21.6 View this GCN Circular online at https://gcn.nasa.gov/circulars/43929. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42049] EP260302a: Optical afterglow rebrightening
by GCN Circulars 05 Mar '26

05 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43928 SUBJECT: EP260302a: Optical afterglow rebrightening DATE: 26/03/05 23:34:56 GMT FROM: Gregory Corcoran at University College Dublin <gregory.corcoran(a)ucdconnect.ie> G. Corcoran (UCD), L. Cotter (UCD), J. Quirola-Vasquez (Radboud), A. Martin-Carrillo (UCD), R. A. J. Eyles-Ferris (Leicester), D. B. Malesani (DAWN/NBI and Radboud), P. G. Jonker (Radboud) report on behalf of a larger collaboration: We observed the optical counterpart (Li et al., GCN 43898; Pérez-García et al., GCN 43903; Corcoran et al., GCN 43904) of the fast X-ray transient EP260302a (Zhang et al., GCN 43899; Zhang et al., GCN 43906) on two epochs. Our first observation was carried out with the Gemini South telescope located in Cerro Pachon (Chile); and the second with the LCO 1m telescope located in Sutherland (South Africa). The exposure times were 1x30 and 9x300 s, respectively, both in the SDSS r band, at mean epochs 2026-03-03 at 07:25:03 UT and 2026-03-05 at 19:05:14 UT (~7.8 and ~67.4 hr after trigger, respectively). The counterpart is clearly detected on both epochs. We measure magnitudes r = 22.06 +- 0.12 (Gemini) and r = 21.07 +/- 0.06 (LCO). Both values are calibrated against nearby stars from the SkyMapper catalog, and are not corrected for Galactic extinction. The observed fluxes imply a rebrightening by ~1 mag, which is uncommon for FXT and GRB afterglows around this epoch, and possibly indicates the emergence of an extra component (for another example, see e.g. van Dalen et al. 2025, doi:10.3847/2041-8213/adbc7e). We encourage further multiwavelength follow up of this unusual source. View this GCN Circular online at https://gcn.nasa.gov/circulars/43928. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42048] GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
by GCN Circulars 05 Mar '26

05 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43927 SUBJECT: GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation DATE: 26/03/05 19:04:24 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Saccardi (CEA/Irfu), Y. Julakanti (Univ. Leicester), D. Turpin (CEA/Irfu), J.-L. Atteia (IRAP), D. B. Malesani (DAWN/NBI and Radboud), Y. H. Cheng (SWIFAR, YNU), R. A. J. Eyles-Ferris (Univ. Leicester) report on behalf of the SVOM and Einstein Probe teams: We performed a second observation at the location of the SVOM/ECLAIRs GRB 260228A (Julakanti et al., GCN 43882) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation started on 2026-03-04 at 19:25:58 UT (3.94 days after the trigger) with a total exposure time of ~6000 s. All six sources detected by EP/FXT during the first visit (Cheng et al., GCN 43900) are detected in the second epoch data set. The brightest of them (EPF_J155124.0+262035; error radius of 10 arcsec) has faded by a factor of ~10, down to a flux of (1.92 +/- 0.47) x 10^-13 erg/s/cm^-2 (0.5-10 keV; 1-sigma uncertainty). The fading behavior of this X-ray source confirms it as the afterglow of GRB 260228A. The early deep optical limits measured by SVOM/VT (Li et al., GCN 43886), compared to the bright X-ray flux (Cheng et al., GCN 43900), suggest that this could be a dark GRB. We encourage multi-wavelength follow-up observation of this source. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43927. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42047] GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
by GCN Circulars 05 Mar '26

05 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43927 SUBJECT: GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation DATE: 26/03/05 19:04:24 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Saccardi (CEA/Irfu), Y. Julakanti (Univ. Leicester), D. Turpin (CEA/Irfu), J.-L. Atteia (IRAP), D. B. Malesani (DAWN/NBI and Radboud), Y. H. Cheng (SWIFAR, YNU), R. A. J. Eyles-Ferris (Univ. Leicester) report on behalf of the SVOM and Einstein Probe teams: We performed a second observation at the location of the SVOM/ECLAIRs GRB 260228A (Julakanti et al., GCN 43882) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation started on 2026-03-04 at 19:25:58 UT (3.94 days after the trigger) with a total exposure time of ~6000 s. All six sources detected by EP/FXT during the first visit (Cheng et al., GCN 43900) are detected in the second epoch data set. The brightest of them (EPF_J155124.0+262035; error radius of 10 arcsec) has faded by a factor of ~10, down to a flux of (1.92 +/- 0.47) x 10^-13 erg/s/cm^-2 (0.5-10 keV; 1-sigma uncertainty). The fading behavior of this X-ray source confirms it as the afterglow of GRB 260228A. The early deep optical limits measured by SVOM/VT (Li et al., GCN 43886), compared to the bright X-ray flux (Cheng et al., GCN 43900), suggest that this could be a dark GRB. We encourage multi-wavelength follow-up observation of this source. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43927. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42046] GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
by GCN Circulars 05 Mar '26

05 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43927 SUBJECT: GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation DATE: 26/03/05 19:04:24 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Saccardi (CEA/Irfu), Y. Julakanti (Univ. Leicester), D. Turpin (CEA/Irfu), J.-L. Atteia (IRAP), D. B. Malesani (DAWN/NBI and Radboud), Y. H. Cheng (SWIFAR, YNU), R. A. J. Eyles-Ferris (Univ. Leicester) report on behalf of the SVOM and Einstein Probe teams: We performed a second observation at the location of the SVOM/ECLAIRs GRB 260228A (Julakanti et al., GCN 43882) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation started on 2026-03-04 at 19:25:58 UT (3.94 days after the trigger) with a total exposure time of ~6000 s. All six sources detected by EP/FXT during the first visit (Cheng et al., GCN 43900) are detected in the second epoch data set. The brightest of them (EPF_J155124.0+262035; error radius of 10 arcsec) has faded by a factor of ~10, down to a flux of (1.92 +/- 0.47) x 10^-13 erg/s/cm^-2 (0.5-10 keV; 1-sigma uncertainty). The fading behavior of this X-ray source confirms it as the afterglow of GRB 260228A. The early deep optical limits measured by SVOM/VT (Li et al., GCN 43886), compared to the bright X-ray flux (Cheng et al., GCN 43900), suggest that this could be a dark GRB. We encourage multi-wavelength follow-up observation of this source. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43927. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42045] GRB 260303A: 1.3m DFOT optical upper limit
by GCN Circulars 05 Mar '26

05 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43926 SUBJECT: GRB 260303A: 1.3m DFOT optical upper limit DATE: 26/03/05 16:36:08 GMT FROM: Debalina Kar at ARIES <kardebalina2000(a)gmail.com> Debalina Kar, Pankaj Pawar, Anshika Gupta, Dhruv Jain and Kuntal Misra (ARIES) report: We observed the field of GRB 260303A triggered by SVOM/ECLAIRs (sb26030303, Wang et al., GCN 43901) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations began on 2026-03-03 at 14:54:29.000 UT, approximately 8.88 hours after the trigger. We obtained multiple exposures of 300 s each in the R filter . A total of 10 frames were aligned and stacked to improve the signal-to-noise ratio. In the stacked frame we do not detect any optical counterpart within the error box of SVOM/ECLAIRs (Brunet et al., GCN 43922, Wang et al., GCN 43901) as well as outside the ECLAIRs error circle as reported by Xin et al. (GCN 43916) and (Schneider et al., GCN 43902). This is consistent with the non-detection in the J band reported by Mo et al. (GCN 43915). We derive the following 3-sigma upper limit from the stacked image: Date (UT) Start Time T_start–T0 (hr) Filter Exposure Magnitude ---------------------------------------------------------------------------------- 2026-03-03 14:54:29 ~8.88 R 300 s × 10 > 20.29 The reported magnitude is not corrected for Galactic extinction. Photometric calibration was performed using standard stars from the USNO-B1.0 catalogue. View this GCN Circular online at https://gcn.nasa.gov/circulars/43926. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42044] GRB 260303A: 1.3m DFOT optical upper limit
by GCN Circulars 05 Mar '26

05 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43925 SUBJECT: GRB 260303A: 1.3m DFOT optical upper limit DATE: 26/03/05 16:34:28 GMT FROM: Debalina Kar at ARIES <kardebalina2000(a)gmail.com> Debalina Kar, Pankaj Pawar, Anshika Gupta, Dhruv Jain and Kuntal Misra (ARIES) report: We observed the field of GRB 260303A triggered by SVOM/ECLAIRs (sb26030303, Wang et al., GCN 43901) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations began on 2026-03-03 at 14:54:29.000 UT, approximately 8.88 hours after the trigger. We obtained multiple exposures of 300 s each in the R filter . A total of 10 frames were aligned and stacked to improve the signal-to-noise ratio. In the stacked frame we do not detect any optical counterpart within the error box of SVOM/ECLAIRs (Brunet et al., GCN 43922, Wang et al., GCN 43901) as well as outside the ECLAIRs error circle as reported by Xin et al. (GCN 43916) and (Schneider et al., GCN 43902). This is consistent with the non-detection in the J band reported by Mo et al. (GCN 43915). We derive the following 3-sigma upper limit from the stacked image: Date (UT) Start Time T_start–T0 (hr) Filter Exposure Magnitude ---------------------------------------------------------------------------------- 2026-03-03 14:54:29 ~8.88 R 300 s × 10 > 20.29 The reported magnitude is not corrected for Galactic extinction. Photometric calibration was performed using standard stars from the USNO-B1.0 catalogue. View this GCN Circular online at https://gcn.nasa.gov/circulars/43925. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42043] GRB 260303A: 1.3m DFOT optical upper limit
by GCN Circulars 05 Mar '26

05 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43925 SUBJECT: GRB 260303A: 1.3m DFOT optical upper limit DATE: 26/03/05 16:34:28 GMT FROM: Debalina Kar at ARIES <kardebalina2000(a)gmail.com> Debalina Kar, Pankaj Pawar, Anshika Gupta, Dhruv Jain and Kuntal Misra (ARIES) report: We observed the field of GRB 260303A triggered by SVOM/ECLAIRs (sb26030303, Wang et al., GCN 43901) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations began on 2026-03-03 at 14:54:29.000 UT, approximately 8.88 hours after the trigger. We obtained multiple exposures of 300 s each in the R filter . A total of 10 frames were aligned and stacked to improve the signal-to-noise ratio. In the stacked frame we do not detect any optical counterpart within the error box of SVOM/ECLAIRs (Brunet et al., GCN 43922, Wang et al., GCN 43901) as well as outside the ECLAIRs error circle as reported by Xin et al. (GCN 43916) and (Schneider et al., GCN 43902). This is consistent with the non-detection in the J band reported by Mo et al. (GCN 43915). We derive the following 3-sigma upper limit from the stacked image: Date (UT) Start Time T_start–T0 (hr) Filter Exposure Magnitude ---------------------------------------------------------------------------------- 2026-03-03 14:54:29 ~8.88 R 300 s × 10 > 20.29 The reported magnitude is not corrected for Galactic extinction. Photometric calibration was performed using standard stars from the USNO-B1.0 catalogue. View this GCN Circular online at https://gcn.nasa.gov/circulars/43925. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42042] EP260214b: ATCA 6 GHz observations
by GCN Circulars 05 Mar '26

05 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43924 SUBJECT: EP260214b: ATCA 6 GHz observations DATE: 26/03/05 15:31:04 GMT FROM: Giulia Gianfagna at INAF-IAPS <giulia.gianfagna(a)inaf.it> G. Gianfagna, G. Bruni, A. L. Thakur, L. Piro (INAF-IAPS) report: We observed the Fast X-ray Transient EP260214b (J Yang et al., GCN 43744, H Yang et al., GCN 43779) with the Australian Telescope Compact Array radio telescope using the 4-cm receiver. Observations were performed on March 3 2026 (at a mean epoch of ~17 days after the EP trigger) for a total of 6 hours. Data were reduced and imaged with standard CASA procedures. The final 6 GHz image has an RMS of ~15 uJy/beam. No radio emission is apparent at the position of the optical counterpart (He et al. GCN 43745, Watson et al. GCN 43747, Le Floch et al. GCN 43749, Pérez-Fournon et al. GCN 43750, Russeil et al. 43752,Li et al. GCN 43755, Vijayjumar et al. GCN 43757, Becerra et al. GCN 43758, Yang et al. GCN 43760, Aaryan et al. GCN 43762, Bochenek et al. GCN 43764, Kar et al. GCN 43774, Volnova et al. GCN 43775). The corresponding 3-sigma upper limit is thus ~50 uJy. Further ATCA observations are planned. The Australia Telescope Compact Array is part of the Australia Telescope National Facility (grid.421683.a), which is funded by the Australian Government for operation as a National Facility managed by CSIRO. We acknowledge the Gomeroi people as the traditional owners of the Observatory site. View this GCN Circular online at https://gcn.nasa.gov/circulars/43924. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42041] GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
by GCN Circulars 05 Mar '26

05 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43923 SUBJECT: GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate DATE: 26/03/05 15:06:48 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Y. N. Ma, C. Wu, Z. H. Yao, Y. L. Qiu, L. P. Xin, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed further ToO observations of GRB 260211A detected by SVOM/Eclairs and SVOM/GRM (sb26021102, Gotz et al., GCN 43705). Also there was a sub-threshold detection by Fermi GBM (Hamburg et al., GCN 43713). The observations were performed on 2026-03-03 and 2026-03-05 in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The optical counterpart (Li et al., GCN 43720, GCN 43748) was measured to have a brightness of VT_R=22.91+/-0.25 mag at 19.36 days post trigger and VT_R=22.85+/-0.25 mag at 21.31 days respectively. These measurements show that the counterpart is rebrightening, relative to the reported brightness (Li et al. GCN 43748). We suggest that it is likely the supernova associated with the burst. Further follow-up observations are encouraged. Our photometry was in AB magnitude and was not corrected for Galactic extinction. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/43923. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42040] GRB 260303A: SVOM/ECLAIRs refined analysis
by GCN Circulars 05 Mar '26

05 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43922 SUBJECT: GRB 260303A: SVOM/ECLAIRs refined analysis DATE: 26/03/05 09:11:45 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet, L. Bouchet (IRAP), Z. Wang, D. Kong(GXU) report on behalf of the SVOM/ECLAIRs team. Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of GRB 260303A (SVOM burst-id sb26030303 – GCN 43901, trigger time T0 = 2026-03-03T06:01:47 UTC). The burst that triggered ECLAIRs shows a single peak lightcurve. The burst duration is estimated to be around 14.5s (from T0-19.5s to T0-5s) in the 4-120 keV energy band through imaging. The refined burst localization is RA, Dec = 93.1458, 41.1727 degrees: RA (J2000) = 06h12m34.99s Dec (J2000) = 41d10m21.72s with a 90% C.L. radius of 9.6 arcmin (including systematic error of 6 arcmin added in quadrature). The time-averaged spectrum from T0-19.5 s to T0-5 s in the energy range 5-120 keV is best fitted by a powerlaw model with a photon index of 1.67 +0.14/-0.13. With this model, the 4-120 keV fluence is (1.19 +0.11/-0.20) e-6 erg/cm² and the 4-120 keV photon flux is 2.73 +0.16/-0.31 ph/cm²/s. All the quoted errors are at the 68% confidence level. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/43922. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42039] Fermi GRB 260305A: Global MASTER-Net observations report
by GCN Circulars 05 Mar '26

05 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43921 SUBJECT: Fermi GRB 260305A: Global MASTER-Net observations report DATE: 26/03/05 03:00:46 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 260305A ( Fermi GBM team, GCN 43920) errorbox 55 sec after notice time and 87 sec after trigger time at 2026-03-05 02:43:05 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 70 deg. The sun altitude is -22.7 deg. The galactic latitude b = 68 deg., longitude l = 57 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3169780 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 98 | 2026-03-05 02:43:05 | MASTER-SAAO | (14h 27m 04.56s , +37d 55m 52.3s) | C | 20 | 17.2 | 98 | 2026-03-05 02:43:05 | MASTER-SAAO | (14h 24m 55.60s , +38d 11m 54.7s) | C | 20 | 17.0 | 217 | 2026-03-05 02:44:55 | MASTER-SAAO | (14h 12m 08.18s , +34d 56m 29.5s) | C | 40 | 17.4 | 272 | 2026-03-05 02:44:55 | MASTER-SAAO | (14h 12m 08.18s , +34d 56m 29.4s) | C | 150 | 18.6 | 217 | 2026-03-05 02:44:55 | MASTER-SAAO | (14h 14m 11.70s , +34d 40m 22.7s) | C | 40 | 17.6 | 272 | 2026-03-05 02:44:55 | MASTER-SAAO | (14h 14m 11.71s , +34d 40m 22.8s) | C | 150 | 18.4 | 281 | 2026-03-05 02:45:54 | MASTER-SAAO | (14h 14m 11.94s , +34d 40m 26.1s) | C | 50 | 17.8 | 281 | 2026-03-05 02:45:54 | MASTER-SAAO | (14h 12m 08.41s , +34d 56m 34.1s) | C | 50 | 17.5 | 355 | 2026-03-05 02:47:03 | MASTER-SAAO | (14h 12m 08.69s , +34d 56m 39.2s) | C | 60 | 17.7 | 355 | 2026-03-05 02:47:03 | MASTER-SAAO | (14h 14m 12.16s , +34d 40m 30.0s) | C | 60 | 17.8 | 625 | 2026-03-05 02:51:33 | MASTER-SAAO | (14h 24m 26.43s , +33d 57m 36.0s) | C | 60 | 17.8 | 625 | 2026-03-05 02:51:33 | MASTER-SAAO | (14h 22m 22.92s , +34d 13m 45.5s) | C | 60 | 17.5 | 704 | 2026-03-05 02:52:52 | MASTER-SAAO | (14h 24m 26.68s , +33d 57m 40.9s) | C | 60 | 17.8 | 704 | 2026-03-05 02:52:52 | MASTER-SAAO | (14h 22m 23.24s , +34d 13m 52.3s) | C | 60 | 17.7 | 784 | 2026-03-05 02:54:11 | MASTER-SAAO | (14h 22m 23.58s , +34d 13m 57.5s) | C | 60 | 17.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43921. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42038] GRB 260305A: Fermi GBM Final Real-time Localization
by GCN Circulars 05 Mar '26

05 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43920 SUBJECT: GRB 260305A: Fermi GBM Final Real-time Localization DATE: 26/03/05 02:52:09 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 02:41:38 UT on 5 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260305A (trigger 794371303.18619 / 260305112). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 216.5, Dec = 34.0 (J2000 degrees, equivalent to J2000 14h 26m, 34d 00'), with a statistical uncertainty of 2.4 degrees. The angle from the Fermi LAT boresight is 49.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260305112/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260305112/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260305112/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43920. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42037] GCN Announcement: Retirement of GCN Classic VOEvent Brokers
by GCN Announcements 04 Mar '26

04 Mar '26

As initially announced in 2025, we are planning to retire the GCN Classic VOEvent brokers (https://gcn.gsfc.nasa.gov/voevent.html) on April 6, 2026. This impacts users who utilize the VOEvent Transfer Protocol (VTP) to receive VOEvent-format GCN Classic Notices. VOEvent-format Notices remain available via Kafka and email (https://gcn.nasa.gov/docs/notices/consuming) and we recommend users migrate from VTP to Kafka. For more details on this new feature and an archive of GCN news and announcements, see https://gcn.nasa.gov/news. For questions, issues, or bug reports, please contact us via: - Contact form: https://gcn.nasa.gov/contact - GitHub issue tracker: https://github.com/nasa-gcn/gcn.nasa.gov/issues --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42036] GRB 260303B: AstroSat CZTI detection
by GCN Circulars 04 Mar '26

04 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43919 SUBJECT: GRB 260303B: AstroSat CZTI detection DATE: 26/03/04 19:43:04 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), S. Salunke (IUCAA), A. Arya (IITB), A. Goyal (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long GRB 260303B which was also detected by Fermi GBM (Fermi GBM Team., GCN Circ. 43907), and NuSTAR (Waratkar et. al. , GCN Circ. 43914). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2026-03-03 13:24:23.50 UTC. The measured peak count rate associated with the burst is 59 (+29, -5) counts/s above the background in the combined data of two quadrants (out of four), with a total of 504 (+69, -193) counts. The local mean background count rate was 167 (+1, -5) counts/s. We measure a T90 of 11 (+1, -3) s. The source was also faintly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/43919. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42035] GRB 260304A: AstroSat CZTI detection of a long burst
by GCN Circulars 04 Mar '26

04 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43918 SUBJECT: GRB 260304A: AstroSat CZTI detection of a long burst DATE: 26/03/04 18:56:56 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> A. Arya (IITB), A. Goyal (IITB), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), S. Salunke (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 260304A which was also detected by Konus-Wind (Priv. Comm. with T0 at 07:24:53.608 UT). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-03-04 07:25:02.120 UTC. The measured peak count rate associated with the burst is 121 (+29, -16) counts/s above the background in the combined data of two quadrants (out of four), with a total of 1569 (+602, -342) counts. The local mean background count rate was 142 (+2, -3) counts/s. Using cumulative rates, we measure a T90 of 32 (+23, -9) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-03-04 07:24:50.186 UTC. The measured peak count rate associated with the burst is 298 (+72, -28) counts/s above the background in the combined data of all quadrants, with a total of 2770 (+533, -517) counts. The local mean background count rate was 1221 (+5, -4) counts/s. We measure a T90 of 31 (+3, -6) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/43918. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42034] SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
by GCN Circulars 04 Mar '26

04 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43917 SUBJECT: SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei DATE: 26/03/04 11:49:37 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Li (BNU), C. Wu (NAOC), H. Yang, L. Bouchet (IRAP), D. Turpin, D. Götz (CEA) report on behalf of the SVOM mission team: At 2026-03-04T09:44:54 UTC (T0), SVOM/ECLAIRs triggered and located a possible X-ray transient (SVOM burst-id sb26030408). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The transient was only detected by the Image Trigger (IMT), which produced a sequence of 6 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 12.50 in the [5-20] keV energy band over a time window of 655.36 seconds starting at 2026-03-04T09:42:10. The localization of the best alert is R.A., Dec. 47.1221, 40.9012 degrees: R.A. (J2000) = 3h08m29.30s Dec. (J2000) = 40d54m04.41s with a 90% confidence level (C.L.) radius of 6.48 arcmin (including systematic error of 2 arcmin added in quadrature). No immediate slew was performed on this transient. No X-ray observation could be performed by SVOM/MXT for the time being. No optical observation could be performed by SVOM/VT for the time being. We notice the presence of the bright star Beta Persei, located at 4.9 arcmin from the trigger position, which could be the origin of the trigger. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is An Li: 202221160007(a)mail.bnu.edu.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/43917. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42033] GRB 260303A: SVOM/VT optical observations
by GCN Circulars 04 Mar '26

04 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43916 SUBJECT: GRB 260303A: SVOM/VT optical observations DATE: 26/03/04 01:20:25 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L. P. Xin, Y. N. Ma, H. L. Li, C. Wu, Z. H. Yao, Y. L. Qiu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu), Ziqi Wang and Defeng Kong(GXU) report on behalf of the SVOM/VT team. SVOM/VT performed observation with auto slew to the field of GRB 260303A triggered by SVOM/ECLAIRs (sb26030303,Wang et al., GCN 43901). The observation started at 2026-03-03T06:12:27 UTC, i.e. about 9.5 minutes post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical afterglow reported (Schneider et al., GCN 43902) was clearly detected in both channels. The magnitudes we derived are: mid time (min) | exposure time (s)| band| mag (AB) -------------|-------------------|------ |-------------- 10.4 | 50 | VT_B | 19.29+/-0.05 10.4 | 50 | VT_R | 17.62+/-0.02 47.5 | 50 | VT_B | 20.48+/-0.11 47.5 | 50 | VT_R | 19.51+/-0.07 More detailed analysis is still on going. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/43916. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42032] GRB 260303A: J-band observations with WINTER
by GCN Circulars 04 Mar '26

04 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43915 SUBJECT: GRB 260303A: J-band observations with WINTER DATE: 26/03/04 00:22:14 GMT FROM: Geoffrey Mo at Caltech / Carnegie Observatories <gmo(a)mit.edu> Geoffrey Mo (Caltech/Carnegie), Benjamin Schneider (LAM), Tomas Ahumada (NOIRLab), Robert Stein (UMD), Viraj Karambelkar (Columbia), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of GRB 260303A (Wang et al., GCN 43901) in the near-infrared J band with the Palomar 1-m telescope, equipped with the 1.2-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations began at 2026-03-03T06:53:36 UTC in the J band (~52 min after the GRB trigger), consisting of 15 x 120 s exposures. The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565) We do not detect a source at the optical counterpart location (Schneider et al., GCN 43902). We obtain the following 5-sigma upper limit: J = 19.2 mag (AB). WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research. View this GCN Circular online at https://gcn.nasa.gov/circulars/43915. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42031] GRB 260303B: NuSTAR detection of prompt emission
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43914 SUBJECT: GRB 260303B: NuSTAR detection of prompt emission DATE: 26/03/03 19:20:30 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 260303B in both the NuSTAR CsI anti-coincidence shields. This GRB was identified through a blind search using the CsI shield rates. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm triggered at 2026-03-03 13:24:32.0 (with a resolution ~5-seconds). This is consistent with the detection of GRB 260303B by Fermi/GBM (Fermi GBM Team, GCN Circ. 43907). The NuSTAR CsI shield data are recorded at 1 Hz. We see a single-peak detection lasting for ~20-s, consistent with the detections of Fermi/GBM. The peak count rate is ~1500-cps with a baseline rate of ~1000-cps during this time period. We don’t see any evidence in the signal above 100 keV in the CdZnTe detectors. The GBM localization center (GCN Circ. 43907) at RA = 9.3, Dec = -26.7 implies an offset from the NuSTAR boresight of 92-deg (i.e. from the side of the instrument) and an offset from the geocenter of 159-deg. Lightcurves and analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260303B Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/43914. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42030] EP260302a: Global MASTER-Net observations report
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43913 SUBJECT: EP260302a: Global MASTER-Net observations report DATE: 26/03/03 19:18:35 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) was pointed to the EP260302a ( EP Team et al., GCN 43899) errorbox 57834 sec after notice time and 69373 sec after trigger time at 2026-03-03 18:55:35 UT, with upper limit up to 18.3 mag. The observations began at zenith distance = 38 deg. The sun altitude is -22.0 deg. The galactic latitude b = -14 deg., longitude l = 282 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3165840 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 69433 | 2026-03-03 18:55:35 | MASTER-SAAO | (08h 50m 51.10s , -66d 07m 10.9s) | C | 120 | 18.3 | 69433 | 2026-03-03 18:55:35 | MASTER-SAAO | (08h 46m 26.64s , -65d 51m 45.5s) | C | 120 | 18.1 | 69556 | 2026-03-03 18:58:07 | MASTER-SAAO | (08h 50m 47.34s , -66d 05m 34.5s) | C | 60 | 18.1 | 69556 | 2026-03-03 18:58:07 | MASTER-SAAO | (08h 46m 22.97s , -65d 50m 10.3s) | C | 60 | 18.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43913. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42029] Fermi GRB 260303B: Global MASTER-Net observations report
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43912 SUBJECT: Fermi GRB 260303B: Global MASTER-Net observations report DATE: 26/03/03 19:17:13 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 260303B ( Fermi GBM team, GCN 43907) errorbox 20103 sec after notice time and 20130 sec after trigger time at 2026-03-03 18:59:50 UT, with upper limit up to 16.5 mag. The observations began at zenith distance = 82 deg. The sun altitude is -22.8 deg. The galactic latitude b = -87 deg., longitude l = 48 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3166705 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 20160 | 2026-03-03 18:59:50 | MASTER-SAAO | (00h 37m 01.21s , -26d 50m 03.0s) | C | 60 | 16.2 | 20252 | 2026-03-03 19:01:22 | MASTER-SAAO | (00h 37m 03.97s , -26d 48m 23.8s) | C | 60 | 16.5 | 20344 | 2026-03-03 19:02:54 | MASTER-SAAO | (00h 36m 56.33s , -26d 49m 08.6s) | C | 60 | 16.4 | 20466 | 2026-03-03 19:04:26 | MASTER-SAAO | (00h 36m 55.39s , -26d 48m 01.6s) | C | 120 | 15.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43912. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42028] IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43911 SUBJECT: IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility DATE: 26/03/03 18:33:37 GMT FROM: Jannis Necker at DESY <jannis.necker(a)desy.de> Jannis Necker (Leiden University), Akshay Eranhalodi (DESY), Robert Stein (JSI), and Anna Franckowiak (Ruhr University Bochum) report, On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-260217A (Zegarelli et. al, GCN 43768) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2026-02-22 02:51 UTC, approximately 116.9 hours after event time due to bad weather. We covered 100.0% (0.7 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 30s with a typical depth of 20.5 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019) . No candidate counterparts were detected. ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; OKC, Sweden; DZA, Germany. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/43911. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42027] GRB 260228A: SVOM/ECLAIRs refined analysis
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43910 SUBJECT: GRB 260228A: SVOM/ECLAIRs refined analysis DATE: 26/03/03 15:29:58 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. G. Bernardini (INAF-OAB, LUPM), M. Brunet, J.-L. Atteia, O. Godet (IRAP), W. J. Xie (NAOC), Y. Julakanti, R. A. J. Eyles-Ferries (Leicester Univ.) report on behalf of the SVOM/ECLAIRs team: Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 260228A (SVOM burst-id 26022802). The burst that triggered ECLAIRs onboard (GCN 43882) consists of a double-peaked pulse with a duration of T90 = (18.3 -4.0/+16.0) s in the 4-120 keV energy band. Since the GRB is observed mainly below 20 keV, we also computed the duration in the 4-20 keV energy band: T90 = (22.9 -4.2/+9.4) s. The time-averaged spectrum from T0+7 s to T0+31 s (T0 = 2026-02-28T20:55:34.620) in the energy range 5-120 keV is best fitted by a broken power-law model with alpha_1 = (-1.33 -0.43/+0.34), alpha_2 = (-2.83 -0.33/+0.37) and E_break = (9.6 -0.9/+1.2) keV. With this model, the total 4-120 keV fluence is (4.27 -2.6/+0.2)E-7 erg/cm^2. All the quoted errors are at the 68% confidence level. With these parameters, the Eiso ranges from 1.6E49 erg assuming z=0.1 to 8.6E52 erg at z=10. The location of GRB 260228A in the Amati plane for different redshifts is available here: https://drive.google.com/file/d/1FfPqOo6kSt6L5QR-DGjUvxdrTwvSlPfT/view?usp=… The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Maria Grazia Bernardini (INAF-OAB, LUPM) (maria.bernardini at inaf.it) View this GCN Circular online at https://gcn.nasa.gov/circulars/43910. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42026] GRB 260225A: SVOM/ECLAIRs refined analysis
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43909 SUBJECT: GRB 260225A: SVOM/ECLAIRs refined analysis DATE: 26/03/03 14:56:16 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet, O. Godet (IRAP), W.J. Xie (NAOC), F. Daigne (IAP),Yinuo Ma (NAOC), Li Zhang (IHEP) report on behalf of the SVOM/ECLAIRs team Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of GRB 260225A (SVOM burst-id sb26022501 – GCN 43829, trigger time T0 = 2026-02-25T08:51:15 UTC). The burst that triggered ECLAIRs shows a single peak lightcurve. The burst duration before the satellite slew is estimated through imaging to be around 59 s (from T0-21 s up to T0+209 s) in the 4-120 keV energy band. Some emission below 20 keV is still seen after the slew up to T0+209 s. The time-averaged spectrum before the satellite slew, i.e. from T0-21 s to T0+38 s in the 5-120 keV energy band is best fitted by a broken power-law model with a first photon index of -1.00 +0.20/-0.16, a break energy of 21.7 +4.4/-3.9 keV and a second photon index of -2.06 +0.22/-0.28. With this model, the 4-120 keV fluence is (1.00 +0.04/-0.26)e-6 erg/cm^2. The spectral parameters indicate that this burst is likely to be an X-ray flash. All the quoted errors are at the 68% confidence level. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/43909. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42025] GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43908 SUBJECT: GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559) DATE: 26/03/03 14:05:07 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 794237065 at 13:24:20 on 03 March 2026 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 13.0 deg Decl.(2000.0) = -27.8 deg The 1 sigma statistical error radius is 1.3 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260303559/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260303559/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260303559/json View this GCN Circular online at https://gcn.nasa.gov/circulars/43908. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42024] GRB 260303B: Fermi GBM Final Real-time Localization
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43907 SUBJECT: GRB 260303B: Fermi GBM Final Real-time Localization DATE: 26/03/03 13:34:53 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 13:24:20 UT on 3 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260303B (trigger 794237065.456588 / 260303559). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 9.3, Dec = -26.7 (J2000 degrees, equivalent to J2000 00h 37m, -26d 41'), with a statistical uncertainty of 1.6 degrees. The angle from the Fermi LAT boresight is 67.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260303559/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260303559/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260303559/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43907. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42023] EP260302a: analysis of the follow-up EP-FXT observation
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43906 SUBJECT: EP260302a: analysis of the follow-up EP-FXT observation DATE: 26/03/03 11:54:52 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. J. Zhang (THU), Y. H. Cheng, D. Zhu, K. J. Zhang (YNU), H. W. Pan (NAOC) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260302a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission at 2026-03-02T23:52:58 (UTC) (Zhang et al., GCN 43899), and was followed by several telescopes (Li et al., GCN 43898, Pérez-García et al., GCN 43903, Corcoran et al., GCN 43904). The X-ray source detected by WXT exhibited a flare within the first 100 seconds of the observation. The X-ray source detected by WXT has a 0.5--4 keV flux of approximately 1.4 x 10^-10 erg s^-1 cm^-2, with an power-law index of 1.1. The NH value is fixed to galactic value (8.6 x 10^20 cm^-2). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically, starting at 2026-03-02T23:54:17(UTC), about 2 minutes after the trigger. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 132.9717 deg, Dec. = -65.9839 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The uncatalogued X-ray source revealed a decline in its light curve during the FXT observation. Its X-ray spectrum has a 0.5–10 keV flux of 1.84(+0.05/-0.04) x 10^-10 erg s^-1 cm^-2, with a power-law index of 1.46(+0.04/-0.04) and a NH value of 8.6 x 10^20 (fixed galactic value) + 5.7 (+1.5/-1.4) x 10^20 cm^-2. All errors are performed with 90% significance. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43906. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42022] EP260227a: Gemini-South optical observations
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43905 SUBJECT: EP260227a: Gemini-South optical observations DATE: 26/03/03 10:58:44 GMT FROM: Laura Cotter at University College Dublin <laura.cotter(a)ucdconnect.ie> R. A. J. Eyles-Ferris (Leicester), J. Quirola-Vasquez (Radboud), G. Corcoran (UCD), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), , A. J. Levan (Radboud), D. B. Malesani (DAWN/NBI and Radboud) report on behalf of a larger collaboration: We observed the optical counterpart of the fast X-ray transient EP260227a (Wang et al., GCN 43869) with the Gemini-South telescope equipped with the GMOS-S instrument, obtained 12x60 s exposures in the r band starting at 2026-03-03 05:52:34 UT (t_mid = 81.9 hr). In our stacked image, we detect a faint source coincident with the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al, GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris and Tanvir et al., GCN 43875; Malesani et al., GCN 43876; Eyles-Ferris et al., GCN 43877; Strausbaugh et al., GCN 43879; Bochenek et al., GCN 43880; Gassert et al., GCN 43881; Gupta et al., GCN 43884; Ma et al., GCN 43887; Eyles-Ferris et al., GCN 43888; Zhong et al., GCN 43891; Volnova et al., GCN 43894). In our preliminary photometry, we measure an AB magnitude of r = 24.80 +/- 0.33 calibrated to Pan-STARRS and not corrected for Galactic extinction. It is unclear at this stage whether this is continued transient emission or the underlying host galaxy. View this GCN Circular online at https://gcn.nasa.gov/circulars/43905. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42021] EP260302a: LCO observations
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43904 SUBJECT: EP260302a: LCO observations DATE: 26/03/03 10:57:45 GMT FROM: Laura Cotter at University College Dublin <laura.cotter(a)ucdconnect.ie> G. Corcoran (UCD), L. Cotter (UCD), J. Chacón (PUC), J. A. Quirola-Vasquez (Radboud), A. Martin-Carrillo (UCD), F. E. Bauer (UTa), P. G. Jonker (Radboud) report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP260302a (Zhang et al., GCN 43899) with the LCO 1m telescope located at the Cerro Tololo Inter-American Observatory (Chile) equipped with the SINISTRO instrument. We obtained 6 x 300 exposures in each of the r and z filters, starting on 2026-03-03 at 02:20:48 UT (~2.46 hr post the EP trigger). In our stacked images for both filters we detect the optical counterpart reported by Li et al. (GCN 43898) and Perez-Garcia et al. (GCN 43903), with the following magnitudes: r = 20.84+/-0.11 z = 20.38+/-0.14 The counterpart has faded significantly since the previous reports. These values are in the AB system and are calibrated to Pan-STARRS. These values are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43904. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42020] EP260302a: BOOTES-7 optical counterpart detection at early times
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43903 SUBJECT: EP260302a: BOOTES-7 optical counterpart detection at early times DATE: 26/03/03 08:37:18 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es> I. Pérez-García, S.-Y. Wu, E. Fernandez-García, M. D. Caballero-García, M. Gritsevich, R. Sánchez-Ramírez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), C. Pérez del Pulgar (Univ. de Málaga), Y.-D. Hu (GXU), D. R. Xiong (Yunnan Observatories of CAS), B.-B. Zhang (Nanjing Univ.) and A. Maury (Space, San Pedro de Atacama), on behalf of a larger collaboration, report: Following the detection of the fast X-ray transient EP260302a by the Einstein Probe (Zhang et al. GCN 42899), the 0.6m BOOTES-7 robotic telescope at San Pedro de Atacama (Chile) observed the fast X-ray transient location starting on Mar 3, 00:04:05 UT (11.1 min after trigger) in different optical bands. On a coadd of clear-filter images (4x60s, 00:10:26 UT, mid exposure time) we detect at early times the optical counterpart reported by LCO 1 hr after the trigger (Li et al. GCN 43898), within the EP/FXT 20 arcsec radius error circle, with 19.1 +/- 0.2 mag. We thank the staff at San Pedro de Atacama Celestial Explorations observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/43903. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42019] GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43902 SUBJECT: GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate DATE: 26/03/03 07:31:10 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> Benjamin Schneider (LAM), Rosa L. Becerra (UNAM), Jean-Grégoire Ducoin (CPPM), Jean-Luc Atteia (IRAP), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Dalya Akl (NYUAD), Camila Angulo (UNAM), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), N. A. Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Antonio de Ugarte Postigo (LAM), Ziqi Wang (GXU) and Defeng Kong (GXU) report: We imaged the field of the SVOM GRB 260303A (Wang et al., GCN Circ. 43901) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-03-03 06:02:58 to 06:24:06 UTC (from 81 seconds after the trigger or 30 seconds after the notice until to 24 minutes after the trigger) and obtained 700 seconds of simultaneous exposure in the r and z filters. The data were reduced, coadded, calibrated, and analyzed with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detect an uncatalogued source just outside the ECLAIRs error circle (Wang et al., GCN Circ. 43901) at: RA(J2000) = 06:12:45.06 = 93.1877 degrees Dec(J2000) = +41:09:04.4 = 41.1512 degrees with an uncertainty of 0.5 arcsec. The preliminary magnitudes derived for that source are: r = 18.69 +/- 0.01 z = 18.19 +/- 0.02 The source is observed to rise and then fall in both r and z. Further observations are ongoing. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43902. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42018] GRB 260303A: SVOM detection of a burst
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43901 SUBJECT: GRB 260303A: SVOM detection of a burst DATE: 26/03/03 07:17:32 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Ziqi Wang, Defeng Kong(GXU), Donghua Zhao(NAOC), Hatsune Goto(Kanazawa Univ.) report on behalf of the SVOM mission team: At 2026-03-03T06:01:47 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260303A (SVOM burst-id sb26030303). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced a sequence of 5 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 7.95 in the [5-20] keV energy band over a time window of 20.48 seconds starting at 2026-03-03T06:01:27. The localization of the best alert is R.A., Dec. 92.9479, 41.1688 degrees: R.A. (J2000) = 6h11m47.49s Dec. (J2000) = 41d10m07.61s with a 90% confidence level (C.L.) radius of 9.89 arcmin (including systematic error of 2 arcmin added in quadrature). We note that the best position (2 overlapped positions) was distant from other 3 detected positions, maybe due to Crab in FoV. The best detection in other 3 triggers are: R.A., Dec. 93.220, 41.184 degrees with 90% confidence level (C.L.) radius of 10.52'. SVOM slewed to the burst. The SVOM/MXT team is waiting for the full dataset to detect and localise the possible SVOM/MXT counterpart. VT began observing the field after the slew. The analysis of the data will be published in a future circular. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is: Ziqi Wang: ziqi.wang(a)st.gxu.edu.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/43901. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42017] GRB 260228A: EP-FXT follow-up observation
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43900 SUBJECT: GRB 260228A: EP-FXT follow-up observation DATE: 26/03/03 07:00:27 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.H.Cheng, D.Zhu, K.J.Zhang (SWIFAR, YNU), H.C.Ding, T.Wu (AHNU), C.C.Jin (NAOC) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 260228A (SVOM/sb26022802; Julakanti et al., GCN 43882) starting at 2026-02-28T22:50:15 UTC, approximately 5 minutes after the SVOM trigger, with a total exposure time of 5527 s. Six uncataloged sources are detected within the ECLAIRs error circle. Preliminary analysis on these sources is automatically conducted, and the details are listed as follows. EPF_J155124.0+262035 RA (J2000): 237.8501 Dec (J2000): 26.3431 Flux: 2.1373 x 10^-12 erg/s/cm2 (observed, 0.5-10 keV) Flux_err: 1.6673 x 10^-13 erg/s/cm2 (1 sigma) EPF_J155105.1+261820 RA (J2000): 237.7711 Dec (J2000): 26.3055 Flux: 9.6351 x 10^-14 erg/s/cm2 (observed, 0.5-10 keV) Flux_err: 1.891 x 10^-14 erg/s/cm2 (1 sigma) EPF_J155123.9+261238 RA (J2000): 237.8498 Dec (J2000): 26.2105 Flux: 7.077 x 10^-14 erg/s/cm2 (observed, 0.5-10 keV) Flux_err: 1.6973 x 10^-14 erg/s/cm2 (1 sigma) EPF_J155130.8+261248 RA (J2000): 237.8781 Dec (J2000): 26.2134 Flux: 1.231 x 10^-13 erg/s/cm2 (observed, 0.5-10 keV) Flux_err: 2.1478 x 10^-14 erg/s/cm2 (1 sigma) EPF_J155140.7+261349 RA (J2000): 237.9195 Dec (J2000): 26.2303 Flux: 1.5723 x 10^-13 erg/s/cm2 (observed, 0.5-10 keV) Flux_err: 3.1532 x 10^-14 erg/s/cm2 (1 sigma) EPF_J155148.8+262150 RA (J2000): 237.9533 Dec (J2000): 26.3640 Flux: 1.0194 x 10^-13 erg/s/cm2 (observed, 0.5-10 keV) Flux_err: 2.9166 x 10^-14 erg/s/cm2 (1 sigma) Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43900. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42016] EP260302a: Einstein Probe detection of an X-ray transient
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43899 SUBJECT: EP260302a: Einstein Probe detection of an X-ray transient DATE: 26/03/03 02:50:49 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. J. Zhang (THU), Y. H. Cheng, D. Zhu, K. J. Zhang (YNU), H. W. Pan (NAOC) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260302a. The transient triggered EP-WXT (ID: 01709258736) at 2026-03-02T23:39:22 (UTC). The WXT position of the source is R.A. = 133.015 deg, DEC = -66.007 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 132.9655 deg, DEC = -65.9859 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43899. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42015] The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43898 SUBJECT: The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart DATE: 26/03/03 02:34:27 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> Wenxiong Li (NAOC), Iair Arcavi (TAU), Ido Keinan (TAU), Runduo Liang (NAOC), David Sand (U of Arizona) We observed the position of the EP/WXT trigger 01709258736 with a Las Cumbres 1m telescope at Cerro Tololo Interamerican Observatory, Chile, 1 hour after the Einstein Probe WXT trigger. We took 2x300s exposures in each visit in the broad optical w band. We find an uncataloged source at RA=132.9739, Dec=-65.9837 within the EP/WXT error circle and measure the following preliminary photometry calibrated to the R band: MJD 61102.042 Mag 19.8 View this GCN Circular online at https://gcn.nasa.gov/circulars/43898. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42014] GRB 251130B: TERI Gamma-ray detection
by GCN Circulars 02 Mar '26

02 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43897 SUBJECT: GRB 251130B: TERI Gamma-ray detection DATE: 26/03/02 15:52:59 GMT FROM: nicholasjkirschner(a)gmail.com Nicholas Kirschner (a), Daniel Shy (b), C.C. Cheung (b), Bernard Phlips (b), Michael Streicher (c), James Mason (c), Douglas M. Groves (c), Feng Zhang (c), and Willy Kaye (c) (a) National Research Council Research Associate resident at the U.S. Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375 (b) U.S. Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375 (c) H3D, Inc., 812 Avis Dr., Ann Arbor, MI 48108, USA The cadmium zinc TElluride Radiation Imager (TERI) gamma-ray telescope [1], operating on the International Space Station, reports the detection of GRB 251130B, which was also detected by Fermi/GBM (GCN 42905, 42907), AstroSat/CZTI (GCN 42925), and Glowbug (GCN 42953). Using 1 Hz binning, and adopting T0 = 2025-11-30T15:33:18, we observe the second of the two peaks seen in the Fermi/GBM lightcurve (GCN 42905) at ~T0+78.5s with a peak excess count rate of 276 counts per second (cps) above the 201 cps baseline rate observed in nearby off-source intervals. The analysis results presented here are preliminary and currently lack a detailed response function. TERI is an Office of Naval Research funded technology demonstrator for large-volume pixelated CdZnTe detectors developed, built, and operated by the U.S. Naval Research Laboratory (NRL) in conjunction with H3D, Inc. The pixelated CdZnTe detectors have an energy range of 40 keV to 3 MeV per pixel. It was launched on 2025 April 21 aboard the Department of Defense Space Test Program STP-H10 to the ISS. On the ISS, it is located on the SOX external payload facility on the Columbus module. Analysis of TERI data at NRL is supported by the Office of Naval Research 6.1. [1] Shy, Daniel, et al. "Development of the cadmium zinc TElluride Radiation Imager." Journal of Astronomical Telescopes, Instruments, and Systems 10.4 (2024): 044009-044009 (arXiv:2408.04559). Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/43897. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42013] GRB 260208A: TERI Gamma-ray detection
by GCN Circulars 02 Mar '26

02 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43896 SUBJECT: GRB 260208A: TERI Gamma-ray detection DATE: 26/03/02 15:52:13 GMT FROM: nicholasjkirschner(a)gmail.com Nicholas Kirschner (a), Daniel Shy (b), C.C. Cheung (b), Bernard Phlips (b), Michael Streicher (c), James Mason (c), Douglas M. Groves (c), Feng Zhang (c), and Willy Kaye (c) (a) National Research Council Research Associate resident at the U.S. Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375 (b) U.S. Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375 (c) H3D, Inc., 812 Avis Dr., Ann Arbor, MI 48108, USA The cadmium zinc TElluride Radiation Imager (TERI) gamma-ray telescope [1], operating on the International Space Station, reports the detection of GRB 260208A, which was also detected by Fermi/GBM (GCN 43635, 43673), Fermi/LAT (GCN 43645), GECAM-B (GCN 43658), NuSTAR (GCN 43674), and Glowbug (GCN 43675). Using 1 Hz binning, we find a burst onset at T0 = 2026-02-08T05:07:28 and three emission peaks with excesses of 192, 165, and 130 counts per second (cps) above the 33.2 cps baseline rate observed in nearby off-source intervals, at ~T0+15.5s, 23.5s, and 35.5s, respectively. We use all counts between 40 keV and 3 MeV. The analysis results presented here are preliminary and currently lack a detailed response function. TERI is an Office of Naval Research funded technology demonstrator for large-volume pixelated CdZnTe detectors developed, built, and operated by the U.S. Naval Research Laboratory (NRL) in conjunction with H3D, Inc. The pixelated CdZnTe detectors have an energy range of 40 keV to 3 MeV per pixel. It was launched on 2025 April 21 aboard the Department of Defense Space Test Program STP-H10 to the ISS. On the ISS, it is located on the SOX external payload facility on the Columbus module. Analysis of TERI data at NRL is supported by the Office of Naval Research 6.1. [1] Shy, Daniel, et al. "Development of the cadmium zinc TElluride Radiation Imager." Journal of Astronomical Telescopes, Instruments, and Systems 10.4 (2024): 044009-044009 (arXiv:2408.04559). Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/43896. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42012] GRB 260302A: Fermi GBM Final Real-time Localization
by GCN Circulars 02 Mar '26

02 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43895 SUBJECT: GRB 260302A: Fermi GBM Final Real-time Localization DATE: 26/03/02 14:30:12 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 14:19:40 UT on 2 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260302A (trigger 794153985.446798 / 260302597). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 239.3, Dec = -61.8 (J2000 degrees, equivalent to J2000 15h 57m, -61d 47'), with a statistical uncertainty of 2.7 degrees. The angle from the Fermi LAT boresight is 20.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260302597/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260302597/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260302597/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43895. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42011] EP260227a: Mondy optical observations
by GCN Circulars 02 Mar '26

02 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43894 SUBJECT: EP260227a: Mondy optical observations DATE: 26/03/02 13:09:06 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (IKI) report on behalf of IKI-GRB-FuN: We observed the field of the fast X-ray transient EP260227a (Wang et al., GCN 43869) with the AZT-33IK 1.5m telescope of the Mondy observatory starting on 2026-02-28 (UT) 20:55:14 and taking several 90-seconds frames in the R band. The optical counterpart (Eyles-Ferris et al., GCNs 43867, 43877, 43888; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris and Tanvir, GCN 43875; Malesani et al., GCN 43876; Strausbaugh et al., GCN 43879; Bochenek et al., GCN 43880; Gassert et al., GCN 43881; Gupta et al., GCN 43884; Ma et al., GCN 43887; Zhong et al., GCN 43891) is barely detected in the stacked frame. Preliminary photometry and observational details are the following: Date UT start t-T0 Exp. Filter Obj. S/N UL(3 sigma) (mid,days) (n*s) (3sigma) 2026-02-28 20:55:14 1.05053 40*90 R 21.8 2.5 21.5 The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43894. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42010] GRB 260228A: CAHA 2.2m telescope optical upper limit
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43893 SUBJECT: GRB 260228A: CAHA 2.2m telescope optical upper limit DATE: 26/03/01 22:42:20 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct(a)iaa.es> S. Guziy (IAA-CSIC), Y.-D. Hu (GXU), M.D. Caballero-García, M. Gritsevich, I. Pérez-García, R. Sánchez-Ramírez, S-Y. Wu (IAA-CSIC), G. García-Segura (UNAM), M. Blazek, I. Vico (CAHA) and A.J. Castro-Tirado (IAA-CSIC), on behalf of a larger collaboration, report: Following the detection of GRB 260228A by SVOM/ECLAIRs (Julakanti et al., GCNC 43882), we triggered the 2.2 m CAHA telescope (+ CAFOS) at the Calar Alto Observatory (Almería, Spain). Images were obtained starting on Mar. 1 at 03:34 UT (i.e., ~6.7 hours after the trigger) in the Sloan griz bands covering the entire error region. In the co-added images (60 × 6 s), no optical transient is detected down to limiting magnitudes of 22.1 mag (r') and 21.0 (i'). This non-detection is consistent with the reports from SVOM/VT (Li et al., GCNC 43886) and SVOM/COLIBRÍ (Mandarakas et al. GCNC 43892). We thank the staff at Calar Alto Observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/43893. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42009] GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43892 SUBJECT: GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 26/03/01 17:32:00 GMT FROM: nikos.mandarakas(a)lam.fr Nikos Mandarakas (LAM), Margarita Pereyra (UNAM), Nathaniel R. Butler (ASU), Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Yashaswi Julakanti, Rob Eyles-Ferris report: We imaged the field of the SVOM GRB 260228A (Julakanti et al., GCN Circ. 43882) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-03-01 07:28 to 11:52 UTC (from 10.55 to 14.96 hours after the trigger) and obtained 120 minutes of exposure in the r filter and 129 minutes of exposure in the z filter. The data were reduced, coadded, calibrated, and analysed with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the Pan-STARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, comparing to Pan-STARRS and Legacy Survey (Dey et al. 2019) images, we do not detect any new source within the ECLAIRs uncertainty region (Julakanti et al., GCN Circ. 43882) down to the following 5-sigma limits: r > 23.3 z > 22.5 This upper limit is consistent with the one reported by Li et al. (GCN Circ. 43886). We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43892. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42008] EP260227a: Mephisto optical detection
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43891 SUBJECT: EP260227a: Mephisto optical detection DATE: 26/03/01 14:58:50 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Shiyan Zhong, Hongguang Li, Qinhao Shao, Yuan Fang, Jian Cui, Guowang Du, Yu Pan, Xingzhu Zou, Xinlei Chen, Brajesh Kumar, Jianghua Zhang, Edoardo P. Lagioia, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team: The field of EP260227a (Wang et al., GCN 43869) was observed with the 1.6-meter Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. The simultaneous observations in Mephisto u/g/i bands were started from 2026-02-27T20:20:38 (~8 minutes after the trigger). The field was again simultaneously observed in v/r/z bands (starting from 2026-02-27T20:23:47). We detected a source at the position reported by Eyles-Ferris et. al. (GCN 43867) and other groups Li et al., (GCN 43868); Fu et al, (GCN 43873); Mandarakas et al., (GCN 43874); Eyles-Ferris and Tanvir et al., (GCN 43875); Malesani et al., (GCN 43876); Eyles-Ferris et al., (GCN 43877); Strausbaugh et al., (GCN 43879); Bochenek et al., (GCN 43880); Gassert et al., (GCN 43881); Gupta et al., (GCN 43884); Ma et al., (GCN 43887) and Eyles-Ferris et al., (GCN 43888). The preliminary photometry results (without extinction correction) are listed below: Start_Time (UT) | Band | Exp(s) | Mag/LimMag(AB) --------------------|------|--------|-------------------- 2026-02-27T20:20:38 | u | 45 | >20.86 (3-sigma) 2026-02-27T20:20:38 | g | 45 | 20.58 +/- 0.32 2026-02-27T20:20:38 | i | 45 | 19.92 +/- 0.18 --------------------|------|--------|-------------------- 2026-02-27T20:23:47 | v | 45 | >20.80 (3-sigma) 2026-02-27T20:23:47 | r | 45 | 20.13 +/- 0.25 2026-02-27T20:23:47 | z | 45 | >20.28 (3-sigma) ------------------------------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The Mephisto mosaic cameras were installed in October 2025. The first light was achieved in all three channels on 10 October 2025, and these are currently in the commissioning phase. Here, we note that the current data processing pipeline is still at a preliminary stage, with flux calibration precision in each band at the level of about 5% or even higher. ------------------------------------------------------------------------------------------------- View this GCN Circular online at https://gcn.nasa.gov/circulars/43891. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42007] GRID detection of GRB 260225D
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43890 SUBJECT: GRID detection of GRB 260225D DATE: 26/03/01 13:20:06 GMT FROM: GRID Student Team at Tsinghua University <grid(a)tsinghua.edu.cn> Longhao Li, Chenyu Wang, Zirui Yang report on behalf of the GRID Collaboration: GRID reports the detection of GRB 260225D, which was also observed by Glowbug (GCN #43856) and SVOM/GRM(GCN #43885). The event triggered GRID at T0 = 2026-02-25 19:51:28.7 UTC and was detected by both GRID-09B and GRID-11B, with a weaker signal observed by GRID-11B. Temporal analysis based on GRID-09B data yields a burst duration of T90 = 1.96 ± 0.08 s in the 30–2000 keV energy range. At present, only the GRID light curve is available. No spectral analysis is reported at this stage. The GRID light curve of this event can be found at https://mirrors.tuna.tsinghua.edu.cn/GRID/data/GRID-GCN/GRB260225D/GRID_260… GRID is a student-led project to monitor the transient gamma-ray sky with multiple detectors onboard different nanosatellites in the era of multi-messenger astronomy. For more information about GRID, please refer to: https://doi.org/10.1007/s10686-019-09636-w and https://doi.org/10.1007/s10686-021-09819-4. View this GCN Circular online at https://gcn.nasa.gov/circulars/43890. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42006] EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43889 SUBJECT: EP-WXT trigger 01709258652: 50cm Telescope multi-band observations DATE: 26/03/01 13:18:28 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Yuan Fang, Hong Guang Li, Shiyan Zhong, Qinhao Shao, Jian Cui, Yu Pan, Xingzhu Zou, Xinlei Chen, Brajesh Kumar, Guowang Du, Jinghua Zhang, Xufeng Zhu, Tao Wang, Xinzhong Er, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team: The 50cm Telescope of the Yunnan University was triggered on 2026-02-26T14:42:36 (~52.6 min after the EP/WXT trigger) to observe the field of EP-WXT trigger 01709258652 (Yang et al., GCN 43849; Wu et al., GCN 43857). A sequence of g, r, i and z-band images was obtained about 51 min. The photometry of suggested flare star LP 435-538 (High Proper Motion Star; Yang et al., GCN 43849) shows a decline from 14.41 to 14.89 mag (AB, calibrated against Gaia XP) in g-band over ~47 min. The fading was relatively gradual during this observation period. These results further support the previous finding by Wu et al. (GCN 43857) that EP X-ray trigger was associated with a stellar flare. The 50cm telescope is located at the Lijiang Observatory, China and is part of 50cm array facility. The camera employs an ON Semi KAF-50100 sensor, with 8176 x 6132 pixels of size 6μm (corresponding to 0.3 arcsec projected on the sky). The telescope is utilized for a prompt monitoring of transients and also serves as the supporting facility for monitoring the Mephisto detected targets (Chen et al. 2024, Yang et al. 2024). View this GCN Circular online at https://gcn.nasa.gov/circulars/43889. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42005] EP260227a: further LCO observations
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43888 SUBJECT: EP260227a: further LCO observations DATE: 26/03/01 10:25:41 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris (Leicester), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), and J. Chacón (PUC) report on behalf of a larger collaboration: We observed the optical counterpart of the fast X-ray transient EP260227a (Wang et al., GCN 43869) with an LCO 1m telescope located at the Cerro Tololo Inter-American Observatory (Chile) equipped with the SINISTRO instrument. We obtained nine 300 s exposures in the r band from 2026-03-01 07:52:01 to 2026-03-01 08:43:10 UT (t_mid = 36.09 hr). In our stacked image, we clearly detect the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al, GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris and Tanvir et al., GCN 43875; Malesani et al., GCN 43876; Eyles-Ferris et al., GCN 43877; Strausbaugh et al., GCN 43879; Bochenek et al., GCN 43880; Gassert et al., GCN 43881; Gupta et al., GCN 43884; Ma et al., GCN 43887). We measure an AB magnitude of r = 22.82 +/- 0.28 calibrated to Pan-STARRS and not corrected for Galactic extinction. Our observations suggest there is no significant evolution since the observations of Gupta et al. (GCN 43884) ~12 hr earlier. View this GCN Circular online at https://gcn.nasa.gov/circulars/43888. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42004] EP260227a: SVOM/VT optical observation
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43887 SUBJECT: EP260227a: SVOM/VT optical observation DATE: 26/03/01 09:51:54 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, Z. H. Yao, H. L. Li, Y. L. Qiu, C. Wu, L. P. Xin, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of EP260227a detected by EP/WXT (Wang et al., GCN 43869). SVOM/VT began observing the field at 2026-02-28T07:20:51 UTC, 11.14 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X-band data available, the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris & Tanvir, GCN 43875; Malesani et al., GCN 43876; Eyles-Ferris et al., GCN 43877; Strausbaugh & Cucchiara, GCN 43879; Bochenek & Perley, GCN 43880; Gassert et al., GCN 43881; Gupta et al., GCN 43884) was detected in both VT_B and VT_R bands. The magnitudes are: mid time (h) | exposure time (s) | band | mag (AB) -------------|-------------------|------|-------------- 11.362 | 38*50 | VT_B | 21.9+-0.1 11.313 | 31*50 | VT_R | 21.3+-0.1 Our photometry was not corrected for Galactic extinction. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/43887. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42003] GRB 260228A: SVOM/VT optical upper limits
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43886 SUBJECT: GRB 260228A: SVOM/VT optical upper limits DATE: 26/03/01 08:26:45 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Z. H. Yao, C. Wu, Y. N. Ma, Y. L. Qiu, L. P. Xin, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu), A. Li (BNU), Z. M. Wang (BNU), Y. Julakanti (Univ. Leicester) and R. Eyles-Ferris (Univ. Leicester) report on behalf of the SVOM/VT team. SVOM/VT performed an observation with automatic slew to the field of GRB 260228A triggered by SVOM/ECLAIRs (sb26022802, Julakanti et al., GCN 43882). The observation started at 2026-02-28T21:50:40 UTC, i.e., about 55 minutes post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. No uncatalogued sources were detected within the ECLAIRs error box (Julakanti et al., GCN 43882), compared to the Legacy Survey catalog. The 3 sigma upper limits are derived as follows: Mid time | Band | Exposure Time | 3 sigma upper limit 1.155 hour VT_B 35*50 sec > 23.3 mag 1.169 hour VT_R 34*50 sec > 23.0 mag More detailed analysis is still ongoing. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/43886. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42002] GRB 260225D: SVOM/GRM observation
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43885 SUBJECT: GRB 260225D: SVOM/GRM observation DATE: 26/03/01 08:05:24 GMT FROM: zhangjinpeng(a)ihep.ac.cn SVOM/GRM team: Jin-Peng Zhang, Zheng-Hang Yu, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Daigne (IAP), Olivier GODET (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 260225D (SVOM trigger reference: sb26022503) at 2026-02-25T19:51:30.000 (T0), which is also detected by Konus-Wind (Trig_Time 19:51:32.84), Glowbug (C.C. Cheung et al., GCN #43856) and GRID. With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of two pulses with a T90 of 2.0 +1.0/-0.6 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260225D.png In addition, the position of this burst, according to Glowbug localization (RA = 94.7, Dec = 13.8, C.C. Cheung et al., GCN #43856), is located at about 93 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. Nevertheless, ECLAIRs detected the GRB through the shield above 50 keV. With this localization, the time-averaged spectrum from T0-2.0 to T0+4.0 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.12 +0.18/-0.15 and the cutoff energy, parameterized as Epeak, is 700 +480/-250 keV. The event fluence (10-1000 keV) in this time interval is (8.5 +0.8/-0.9)E-07 erg/cm^2. The localization of GRB 260225D in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260225D_amati.png The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Jin-Peng Zhang (IHEP) (zhangjinpeng(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43885. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42001] EP260227A: 3.6m DOT optical afterglow detection
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43884 SUBJECT: EP260227A: 3.6m DOT optical afterglow detection DATE: 26/03/01 07:52:34 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Dhruv Jain, Pankaj Pawar, Debalina Kar, and Kuntal Misra (ARIES) report: We observed the field of EP260227A detected by Einstein Probe WXT (Wang et al., GCN 43869) with the 3.6m Devasthal Optical Telescope (DOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2026-02-28 at 21:17:26 UT, i.e., ~25.08 hours after the EP/WXT trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We detect an optical counterpart in our stacked image at the position given by the Eyles-Ferris et al. (GCN 43867). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hours) Filter Exp time (s) Magnitude ================================================================== 2026-02-28 21:17:26 ~25.08 R 300s*24 22.92 +/-0.06 Our detection is consistent with Eyles-Ferris et al. (GCN 43867); Li et al. (GCN 43868); Lipunov et al. (GCN 43870); Fu et al.(GCN 43873); Mandarakas et al. (GCN 43874); Eyles-Ferris and N. R. Tanvir et al. (GCN 43875); Malesani et al. (GCN 43876); Eyles-Ferris et al. (GCN 43877); Strausbaugh et al. (GCN 43879); Bochenek et al. (GCN 43880); Gassert et al. (GCN 43881). The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/43884. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42000] GRB 260225B: SVOM/GRM observation
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43883 SUBJECT: GRB 260225B: SVOM/GRM observation DATE: 26/03/01 06:49:10 GMT FROM: yzh807926(a)163.com SVOM/GRM team: Zheng-Hang Yu, Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Daigne (IAP), Olivier GODET (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 260225B (SVOM trigger reference: sb26022502) at 2026-02-25T15:14:10.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43833). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a precursor followed by a main episode showing a single peak with a T90 of 49.0 +26.0/-20.0 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260225B.png In addition, the position of this burst, as determined by Fermi/GBM (RA= 326.4, DEC= 0.9 GCN#43833), is located at about 111 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. At the time of the trigger, ECLAIRs was not collecting data. With this localization, the time-averaged spectrum from T0-5 to T0+30 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.71 +0.17/-0.22 and the cutoff energy, parameterized as Epeak, is 747 +1525/-389 keV. The event fluence (10-1000 keV) in this time interval is (1.48 +0.12/-0.13)E-05 erg/cm^2. The 1s peak spectrum, measured from T0+4 to T0+5 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -1.54 +0.16/-0.20 and the cutoff energy, parameterized as Epeak, is 1390 +1560/-6701 keV. The flux (10-1000 keV) in this time interval is (1.86 +0.14/-0.15)E-06 erg/cm^2/s. The localization of GRB 260225B in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260225B_amati.png The localization of GRB 260225B in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260225B_yonetoku.png The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Zheng-Hang Yu(IHEP)(zhyu(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43883. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41999] GRB 260228A: SVOM detection of a burst
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43882 SUBJECT: GRB 260228A: SVOM detection of a burst DATE: 26/02/28 21:28:57 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Y. Julakanti, R. Eyles-Ferris (Univ. Leicester), S. Schanne (CEA/IRFU), H. Yang (IRAP), M.-G. Bernardini (INAF-OAB, LUPM) report on behalf of the SVOM mission team: At 2026-02-28T20:55:55 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260228A (SVOM burst-id sb26022802). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced a sequence of 7 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 10.64 in the 5-20 keV energy band over a time window of 40.96 seconds starting at 2026-02-28T20:55:34 (Tb). The localization of the best alert is R.A., Dec. 237.8312, 26.3060 degrees: R.A. (J2000) = 15h51m19.50s Dec. (J2000) = 26d18m21.48s with a 90% confidence level (C.L.) radius of 7.51 arcmin (including systematic error of 2 arcmin added in quadrature). The SVOM/ECLAIRs light curve showed a single broad peak structure in the Energy bands 5-8 and 8-20 keV only. The T90 duration computed in 5-120 keV is (16.6 -3.5/+7.2) s. SVOM slewed to the burst. No X-ray observation could be performed by SVOM/MXT for the time being because of Earth occultation. No optical observation could be performed by SVOM/VT for the time being. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Yashaswi Julakanti: skyj1(a)leicester.ac.uk. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/43882. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41998] EP260227a: FTW optical and NIR observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43881 SUBJECT: EP260227a: FTW optical and NIR observations DATE: 26/02/28 20:17:24 GMT FROM: Julius Gassert at Ludwig-Maximilians-Universität München <julius.gassert(a)campus.lmu.de> Julius Gassert (LMU/CMU), Malte Busmann (LMU), Christoph Ries (LMU), Xander J. Hall (CMU), Brendan O’Connor (CMU), Daniel Gruen (LMU), and Antonella Palmese (CMU) report: We observed the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris & Tanvir, GCN 43875; Malesani et al., GCN 43876; Eyles-Ferris et al., GCN 43877; Strausbaugh et al, GCN 43879, Bochenek et al. GCN 43880) of EP 20260227a (Wang et al., GCN 43869) with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i, and J bands for 19x 180s, starting at 2026-02-28T04:21:12 (0.34 days after the trigger). We detect the counterpart in all bands and measure an r-band magnitude of r = 21.69 +/- 0.10 AB mag The magnitude is calibrated against the PS1 catalog and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43881. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41997] EP260227a: Liverpool Telescope optical observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43880 SUBJECT: EP260227a: Liverpool Telescope optical observations DATE: 26/02/28 20:05:03 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek, D. A. Perley (LJMU) report: We observed the field of EP260227a (Wang et al., GCN 43869) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 5x120s exposures in SDSS r and i filters and 3x100s + 2x120s in SDSS z, starting at 2026-02-28 02:54:00 UT, approximately 6.69 hours after trigger. We report detections in stacked images in all filters at the position first reported by Eyles-Ferris et al. (GCN 43867) and Li et al. (GCN 43868). MJD (mid) T_mid-T_0 Filter Mag. (AB) 61099.12483 6.79 h r 21.31 ± 0.19 61099.13319 6.99 h i 21.10 ± 0.12 61099.14035 7.16 h z 20.71 ± 0.11 Our results are consistent with the slower fading of the optical counterpart as reported by and Eyles-Ferris et al. (GCN 43875), comparing to the observations of Fu et al. (GCN 43873), Mandarakas et al. (GCN 43874) and Eyles-Ferris et al. (GCN 43875). The photometry was obtained using nearby PanSTARRS secondary standards and was not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43880. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41996] EP260227a: LCOGT Optical Observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43879 SUBJECT: EP260227a: LCOGT Optical Observations DATE: 26/02/28 17:33:05 GMT FROM: Robert Strausbaugh at Eastern Illinois University <rstrausbaugh(a)eiu.edu> R. Strausbaugh (Eastern Illinois University), A. Cucchiara (NASA) report on behalf of a larger collaboration: We observed the EP260227a field (Wang et al., GCN 43869) with the LCOGT 1-meter Sinistro instrument at the Cerro Tololo Interamerican Observatory, Chile site, on February 28, from 05:39 to 06:00 UT (corresponding to 9.28 to 9.63 hours after the trigger time) with the SDSS r and i filters. We performed a series of 3x200s exposures in i-band and r-band. We marginally detect an uncatalogued sources in both bands, consistent with other optical detections (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris et al., GCN 43875; Malesani et al., GCN 43876). The following magnitudes are calculated using the PanSTARRS catalog as reference: r = 20.78 +/- 0.58 i = 21.47 +/- 0.52 These magnitudes are not corrected for galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43879. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41995] GRB 260226A: Asiago r-band upper limit
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43878 SUBJECT: GRB 260226A: Asiago r-band upper limit DATE: 26/02/28 12:43:06 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> A. Reguitti (INAF/OAPd), P. D'Avanzo (INAF/OAB), D. B. Malesani (DAWN/NBI and Radboud), L. Tomasella (INAF/OAPd) report on behalf of the CIBO collaboration: We observed the field of the bright GRB 260226A (Depalo et al., GCN 43850; Bissaldi et al., GCN 43851; Harsha et al., GCN 43846; Waratkar & Grefenstette, GCN 43854; Woolf et al.. GCN 43855; Kobayashi et al., GCN 43860; Svinkin et al., GCN 43864; Yu et al., GCN 43865) using the 67/92 Schmidt Telescope located at the Asiago observatory (Italy). Observations consisted of five r-band exposures of 240 s each, with a mid time Feb 26.766 UT (7.77 hr after the Fermi/GBM trigger). Image subtraction was carried out using the DESI Legacy survey (Dey et al. 2019, doi:10.3847/1538-3881/ab089d) as template. No new source is detected within the revised Fermi/LAT error circle (Depalo et al., GCN 43850) down to a limiting magnitude r > 20.4 AB (calibrated against nearby objects from the Pan-STARRS catalog). Our non detection is consistent with other reports from the literature (Konno et al., GCN 43852; Saikia et al., GCN 43853; Strausbaugh & Cucchiara, GCN 43858; Angulo et al., GCN 43859). View this GCN Circular online at https://gcn.nasa.gov/circulars/43878. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41994] EP260227a: Thai National Telescope observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43877 SUBJECT: EP260227a: Thai National Telescope observations DATE: 26/02/28 12:41:42 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris (Leicester), S. Littlefair (Sheffield), V. Dhillon (Sheffield), I. Pelisoli (Warwick), J. van Dalen (Radboud), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), D. Mata-Sanchez (IAC and ULL), report on behalf of a larger collaboration: We observed the position of the fast X-ray transient EP260227a (Wang et al., GCN 43869) with the 2.4m Thai National Telescope equipped with the ULTRASPEC instrument. Observations were conducted in the KG5 wideband filter which approximately covers the wavebands of the SDSS ugr filters (https://tinyurl.com/kg5filter; Hardy et al. 2017). The total exposure time was 62 minutes with a mid time of 2026-02-27 22:28:00 UT (2.52 hr after trigger). We clearly detect the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris & Tanvir, GCN 43875; Malesani et al., GCN 43876) at a magnitude m_KG5 = 23.57 +/- 0.07 (AB) calibrated to Pan-STARRS and not corrected for Galactic extinction. The faint magnitude compared to other photometry is likely attributable to the peak response of the adopted filter in the blue and the red colour of the source, broadly consistent with the DLA suggested by Malesani et al (GCN 43876). View this GCN Circular online at https://gcn.nasa.gov/circulars/43877. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41993] EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43876 SUBJECT: EP260227a: likely GTC/OSIRIS+ redshift z = 2.714 DATE: 26/02/28 12:12:32 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> D. B. Malesani (DAWN/NBI and Radboud), P. G. Jonker (Radboud), A. Martin-Carrillo (UCD), R. A. J. Eyles-Ferris (Leicester), J. van Dalen (Radboud), D. Mata-Sanchez (IAC and ULL), A. de Ugarte Postigo (LAM), N. Castro Rodríguez (GTC), A. L. Cabrera Lavers (GTC) report on behalf of a larger collaboration: We observed the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris & Tanvir, GCN 43875) of EP260227a (Wang et al., GCN 43869) using the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ spectrograph. Our observations consisted of 4 exposures of 900 s each, using grism R1000B which covers the wavelength range 3670 - 7700 Å. The observation start time was 2026-02-28 at 03:16 UT (~7.1 hr after the trigger). In the acquisition magnitude, we measure r = 21.55 +/- 0.07 AB at mid time 6.89 hr after trigger (consistent with the NOT measurement; Fu et al., GCN 43873). This value is calibrated against nearby objects from the Pan-STARRS catalog and not corrected for Galactic extinction. A faint trace is detected down to ~4000 Å, with an apparent spectral break around 4500 Å which is interpreted as due to H I and the onset of the Lyman forest. A few weak, narrow features, due to Si II 1259, Si II 1304, C II 1334, C IV 1548/1550, allow us to measure a redshift z = 2.714. View this GCN Circular online at https://gcn.nasa.gov/circulars/43876. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41992] EP260227a: Liverpool Telescope observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43875 SUBJECT: EP260227a: Liverpool Telescope observations DATE: 26/02/28 10:29:52 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris and N. R. Tanvir (Leicester) report on behalf of a larger collaboration: We observed the field of EP260227a (Wang et al., GCN 43869) with the 2m Liverpool Telescope on La Palma using the IO:O instrument. We obtained 6x150s exposures in each of the SDSS g’ r’ i’ z’ filters starting at 2026-02-28 04:25:03 UT, approximately 8.21 hours after the X-ray detection. We detect the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874) in the r’, i’ and z’ bands. We measure the following magnitudes calibrated to Pan-STARRS and not corrected for Galactic extinction. | t_mid (hours) | Filter | AB magnitude | | ------------- | ------ | ---------------- | | 8.35 | g’ | >22.28 (3-sigma) | | 8.63 | i’ | 21.12 +/- 0.08 | | 8.92 | r’ | 21.61 +/- 0.22 | | 9.21 | z’ | 20.74 +/- 0.11 | Compared to the photometry tabulated by Fu et al. (GCN 43873) and Mandarakas et al. (GCN 43874), our observations suggest the source has not faded significantly between these three epochs. View this GCN Circular online at https://gcn.nasa.gov/circulars/43875. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41991] EP260227a: COLIBRÍ optical observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43874 SUBJECT: EP260227a: COLIBRÍ optical observations DATE: 26/02/28 09:50:46 GMT FROM: nikos.mandarakas(a)lam.fr Nikos Mandarakas (LAM), Camila Angulo (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the EP260227a (Wang et al., GCN Circ. 43869) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-28 07:51:00 to 08:49:14 UTC (from 11.64 to 12.61 hours after the trigger) and obtained 44 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded, calibrated, and analysed with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detected the optical counterpart reported by Eyles-Ferris et al. (GCN 43867), Li et al. (GCN 43868), Fu et al. (GCN 43873), at a preliminary magnitude of: r = 21.4644 +/- 0.0680 z = 20.8905 +/- 0.0745 We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43874. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41990] EP260227a: NOT optical observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43873 SUBJECT: EP260227a: NOT optical observations DATE: 26/02/28 06:51:11 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> S.Y. Fu (HUST), L.B. He, Z.P. Zhu, J. An, X. Liu, S.Q. Jiang, D. Xu (NAOC), J. P. U. Fynbo (DAWN/NBI), A. L. Bouquin (NOT) report on behalf of a large collaboration: We observed the field of EP260227a (Wang et al., GCN 43869) using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. The observations started at 02:20:46 UT, 2026-02-28, i.e. 6.14 hrs after the trigger, and we obtained 3x120 s frames each in Sloan g', r' and i' bands. The previously reported optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868) was detected in our stacked frames with the following AB magnitudes: | t-mid (hrs) | filter | mag | | ----------- |--------| ------------ | | 6.21 | g' | 21.40 ± 0.20 | | 6.33 | r' | 21.50 ± 0.20 | | 6.46 | i | 21.37 ± 0.12 | calibrated using nearby Pan-STARRS1 dr2 catalog, and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43873. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41989] GRB 260225A: SVOM/VT optical continued observations and upper limit
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43872 SUBJECT: GRB 260225A: SVOM/VT optical continued observations and upper limit DATE: 26/02/28 05:02:37 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, Z. H. Yao, H. L. Li, Y. L. Qiu, C. Wu, L. P. Xin, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), L. Zhang (IHEP) report on behalf of the SVOM/VT team. SVOM/VT continued observations of GRB 260225A (sb26022501) triggered by SVOM/ECLAIRs (Ma et al., GCN 43829). With X-band data available, the optical counterpart (Ducoin et al., GCN 43837; Li et al., GCN 43838; Schneider et al., GCN 43861) within EP/FXT error box (Yang et al., GCN 43839) was detected in VT_B band. The magnitudes are: mid time (h) | exposure time (s) | band | mag (AB) -------------|-------------------|------|------------ 35.08 | 37*70 | VT_B | 23.6+/-0.3 35.04 | 27*70 | VT_R | >23.3 Our photometry was not corrected for Galactic extinction. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/43872. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41988] GRID detection of GRB 260223A
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43871 SUBJECT: GRID detection of GRB 260223A DATE: 26/02/28 04:46:33 GMT FROM: GRID Student Team at Tsinghua University <grid(a)tsinghua.edu.cn> GRID detection of GRB 260223A Longhao Li, Xinyu Liu, Chenyu Wang report on behalf of the GRID Collaboration: GRID-11B reports the detection of the long-duration GRB 260223A, which was also detected by Fermi GBM (GCN Circular 43808), MASTER-OAFA (GCN Circular 43809), BALROG (GCN Circular 43810), DDOTI (GCN Circular 43811), COLIBRÍ(GCN Circular 43812), SVOM (GCN Circular 43815), Glowbug (GCN Circular 43824) The event was triggered with GRID on 2026-02-23 at 04:11:09 UTC. The measured burst duration (T90) in the 30-2000 keV range is approximately 22.2 +/- 3.0 seconds. The GRID light curve of this event can be found at [GRID_GRB260223A_ltcv.pdf](https://mirrors.tuna.tsinghua.edu.cn/GRID/data/GRID-GCN/GRB260223A/GRID_GRB260223A_ltcv.pdf). GRID is a student-led project to monitor the transient gamma-ray sky with multiple detectors onboard different nanosatellites in the era of multi-messenger astronomy. For more information about GRID, please refer to the following references: https://doi.org/10.1007/s10686-019-09636-w and https://doi.org/10.1007/s10686-021-09819-4. View this GCN Circular online at https://gcn.nasa.gov/circulars/43871. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41987] EP260227a: Global MASTER-Net observations report
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43870 SUBJECT: EP260227a: Global MASTER-Net observations report DATE: 26/02/28 04:45:41 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) was pointed to the EP260227a ( EP Team et al., GCN 43869) errorbox 14883 sec after trigger time at 2026-02-28 00:20:32 UT, with upper limit up to 21.0 mag. The observations began at zenith distance = 42 deg. The sun altitude is -44.5 deg. The galactic latitude b = 41 deg., longitude l = 345 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3160292 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 14913 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 50m 11.27s , -11d 34m 27.7s) | C | 60 | 19.3 | 14973 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 50m 11.26s , -11d 34m 27.7s) | C | 180 | 19.8 | 15093 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 50m 11.26s , -11d 34m 27.7s) | C | 420 | 20.1 | 15693 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 50m 11.26s , -11d 34m 27.7s) | C | 1620 | 21.0 | 14913 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 48m 18.09s , -11d 18m 45.9s) | C | 60 | 19.2 | 14973 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 48m 18.09s , -11d 18m 45.9s) | C | 180 | 19.8 | 15093 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 48m 18.09s , -11d 18m 46.0s) | C | 420 | 20.0 | 15693 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 48m 17.70s , -11d 18m 51.8s) | C | 1620 | 20.7 | 15005 | 2026-02-28 00:22:04 | MASTER-SAAO | (14h 50m 17.85s , -11d 34m 01.7s) | C | 60 | 19.3 | 15005 | 2026-02-28 00:22:04 | MASTER-SAAO | (14h 48m 24.61s , -11d 18m 21.0s) | C | 60 | 19.2 | 15097 | 2026-02-28 00:23:36 | MASTER-SAAO | (14h 50m 14.69s , -11d 32m 38.3s) | C | 60 | 19.3 | 15097 | 2026-02-28 00:23:36 | MASTER-SAAO | (14h 48m 21.41s , -11d 16m 58.1s) | C | 60 | 19.2 | 15688 | 2026-02-28 00:32:56 | MASTER-SAAO | (14h 50m 10.29s , -11d 34m 21.4s) | C | 120 | 19.7 | 15688 | 2026-02-28 00:32:56 | MASTER-SAAO | (14h 48m 17.24s , -11d 18m 39.5s) | C | 120 | 19.6 | 15840 | 2026-02-28 00:35:28 | MASTER-SAAO | (14h 50m 16.17s , -11d 34m 15.7s) | C | 120 | 19.7 | 15840 | 2026-02-28 00:35:28 | MASTER-SAAO | (14h 48m 23.05s , -11d 18m 34.8s) | C | 120 | 19.6 | 15991 | 2026-02-28 00:38:00 | MASTER-SAAO | (14h 50m 14.08s , -11d 32m 35.0s) | C | 120 | 19.8 | 16111 | 2026-02-28 00:38:00 | MASTER-SAAO | (14h 50m 14.08s , -11d 32m 35.0s) | C | 360 | 20.2 | 15991 | 2026-02-28 00:38:00 | MASTER-SAAO | (14h 48m 20.90s , -11d 16m 54.7s) | C | 120 | 19.7 | 16111 | 2026-02-28 00:38:00 | MASTER-SAAO | (14h 48m 20.90s , -11d 16m 54.7s) | C | 360 | 20.1 | 16144 | 2026-02-28 00:40:32 | MASTER-SAAO | (14h 50m 14.08s , -11d 33m 59.3s) | C | 120 | 19.8 | 16144 | 2026-02-28 00:40:32 | MASTER-SAAO | (14h 48m 20.83s , -11d 18m 19.0s) | C | 120 | 19.6 | 16296 | 2026-02-28 00:43:04 | MASTER-SAAO | (14h 50m 18.07s , -11d 32m 38.9s) | C | 120 | 19.8 | 16296 | 2026-02-28 00:43:04 | MASTER-SAAO | (14h 48m 24.76s , -11d 16m 58.8s) | C | 120 | 19.7 | 16448 | 2026-02-28 00:45:36 | MASTER-SAAO | (14h 50m 11.21s , -11d 33m 12.8s) | C | 120 | 19.8 | 16688 | 2026-02-28 00:45:36 | MASTER-SAAO | (14h 50m 11.21s , -11d 33m 12.8s) | C | 600 | 20.2 | 16448 | 2026-02-28 00:45:36 | MASTER-SAAO | (14h 48m 17.86s , -11d 17m 32.5s) | C | 120 | 19.7 | 16688 | 2026-02-28 00:45:36 | MASTER-SAAO | (14h 48m 17.86s , -11d 17m 32.4s) | C | 600 | 20.2 | 16600 | 2026-02-28 00:48:08 | MASTER-SAAO | (14h 50m 10.14s , -11d 32m 11.3s) | C | 120 | 19.8 | 16600 | 2026-02-28 00:48:08 | MASTER-SAAO | (14h 48m 16.73s , -11d 16m 31.1s) | C | 120 | 19.7 | 16752 | 2026-02-28 00:50:41 | MASTER-SAAO | (14h 50m 17.32s , -11d 33m 09.5s) | C | 120 | 19.8 | 17112 | 2026-02-28 00:50:41 | MASTER-SAAO | (14h 50m 17.32s , -11d 33m 09.5s) | C | 840 | 20.2 | 16752 | 2026-02-28 00:50:41 | MASTER-SAAO | (14h 48m 23.83s , -11d 17m 29.0s) | C | 120 | 19.8 | 17112 | 2026-02-28 00:50:41 | MASTER-SAAO | (14h 48m 23.83s , -11d 17m 29.0s) | C | 840 | 20.2 | 16904 | 2026-02-28 00:53:13 | MASTER-SAAO | (14h 50m 11.91s , -11d 34m 07.5s) | C | 120 | 19.8 | 16904 | 2026-02-28 00:53:13 | MASTER-SAAO | (14h 48m 18.35s , -11d 18m 26.9s) | C | 120 | 19.8 | 17056 | 2026-02-28 00:55:45 | MASTER-SAAO | (14h 50m 17.31s , -11d 34m 04.1s) | C | 120 | 19.8 | 17176 | 2026-02-28 00:55:45 | MASTER-SAAO | (14h 50m 17.31s , -11d 34m 04.1s) | C | 360 | 20.2 | 17056 | 2026-02-28 00:55:45 | MASTER-SAAO | (14h 48m 23.70s , -11d 18m 23.5s) | C | 120 | 19.8 | 17176 | 2026-02-28 00:55:45 | MASTER-SAAO | (14h 48m 23.70s , -11d 18m 23.5s) | C | 360 | 20.1 | 17208 | 2026-02-28 00:58:17 | MASTER-SAAO | (14h 50m 14.06s , -11d 32m 19.1s) | C | 120 | 19.8 | 17208 | 2026-02-28 00:58:17 | MASTER-SAAO | (14h 48m 20.45s , -11d 16m 38.4s) | C | 120 | 19.8 | 17360 | 2026-02-28 01:00:49 | MASTER-SAAO | (14h 50m 14.01s , -11d 33m 49.8s) | C | 120 | 19.8 | 17360 | 2026-02-28 01:00:49 | MASTER-SAAO | (14h 48m 20.41s , -11d 18m 08.7s) | C | 120 | 19.8 | 17512 | 2026-02-28 01:03:21 | MASTER-SAAO | (14h 50m 17.60s , -11d 32m 08.9s) | C | 120 | 19.8 | 17632 | 2026-02-28 01:03:21 | MASTER-SAAO | (14h 50m 17.60s , -11d 32m 08.9s) | C | 360 | 20.2 | 17512 | 2026-02-28 01:03:21 | MASTER-SAAO | (14h 48m 24.04s , -11d 16m 28.0s) | C | 120 | 19.8 | 17632 | 2026-02-28 01:03:21 | MASTER-SAAO | (14h 48m 24.05s , -11d 16m 27.9s) | C | 360 | 20.2 | 17664 | 2026-02-28 01:05:53 | MASTER-SAAO | (14h 50m 10.38s , -11d 32m 57.2s) | C | 120 | 19.9 | 17664 | 2026-02-28 01:05:53 | MASTER-SAAO | (14h 48m 16.83s , -11d 17m 15.8s) | C | 120 | 19.8 | 17816 | 2026-02-28 01:08:25 | MASTER-SAAO | (14h 48m 18.27s , -11d 16m 14.0s) | C | 120 | 19.9 | 17816 | 2026-02-28 01:08:25 | MASTER-SAAO | (14h 50m 11.81s , -11d 31m 55.4s) | C | 120 | 19.8 | 17968 | 2026-02-28 01:10:57 | MASTER-SAAO | (14h 48m 22.89s , -11d 17m 11.4s) | C | 120 | 19.9 | 18208 | 2026-02-28 01:10:57 | MASTER-SAAO | (14h 48m 22.89s , -11d 17m 11.4s) | C | 600 | 20.2 | 17968 | 2026-02-28 01:10:57 | MASTER-SAAO | (14h 50m 16.48s , -11d 32m 53.2s) | C | 120 | 19.8 | 18208 | 2026-02-28 01:10:57 | MASTER-SAAO | (14h 50m 16.48s , -11d 32m 53.1s) | C | 600 | 20.3 | 18121 | 2026-02-28 01:13:29 | MASTER-SAAO | (14h 48m 16.38s , -11d 18m 08.8s) | C | 120 | 19.9 | 18121 | 2026-02-28 01:13:29 | MASTER-SAAO | (14h 50m 10.00s , -11d 33m 50.7s) | C | 120 | 19.9 | 18273 | 2026-02-28 01:16:01 | MASTER-SAAO | (14h 48m 23.93s , -11d 17m 39.4s) | C | 120 | 19.8 | 18273 | 2026-02-28 01:16:01 | MASTER-SAAO | (14h 50m 17.58s , -11d 33m 21.1s) | C | 120 | 19.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43870. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41986] EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43869 SUBJECT: EP260227a: Einstein Probe detection of an X-ray transient and refined analysis DATE: 26/02/28 04:28:28 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. Wang (PMO), H. C. Ding, T, Wu, Y. J. Yi (BNU), W. F. Wen (SZTU), Z. X. Ling(NAOC) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260227a. The transient triggered EP-WXT (ID: 01709258681) at 2026-02-27T20:12:29 (UTC). The WXT position of the source is R.A. = 223.101 deg, DEC = -11.408 deg (J2000) with an uncertainty of 2.586 arcmin in radius (90% C.L. statistical and systematic). The refined analysis of the WXT data shows that the event started at T0=2026-02-27T19:58:52 (UTC), and lasted for approximately 250 seconds. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 9.3×10^20 cm^-2 and a photon index of 0.8 (-0.6/+0.6). The derived average unabsorbed 0.5-4 keV flux is 4.1 (-1.3/+1.7) × 10^(-10) erg/s/cm^2. A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 223.1002 deg, DEC = -11.386 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 1.8 (-0.1/+0.1) × 10^21 cm^-2, and a photon index of 1.5 (-0.3/+0.3). The derived average unabsorbed 0.5-10 keV flux is 8.3 (-0.9/+1.2) ×10^(-12) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. The optical counterpart was reported by Eyles-Ferris et al. (GCN 43867) and Li et al. (GCN 43868). Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43869. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41985] The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43868 SUBJECT: The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart DATE: 26/02/28 02:12:37 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> Wenxiong Li (NAOC), Iair Arcavi (TAU), Ido Keinan (TAU), Runduo Liang (NAOC), David Sand (U of Arizona) We observed the position of the EP-WXT trigger 01709258681 (EP260227a?) with a Las Cumbres 1m telescope at Siding Spring Observatory 2.6 hours after the Einstein Probe WXT trigger and again 4 hours after the trigger. We took 2x300s exposures in each visit in the broad optical w band. We find a rapidly fading source consistent with the position reported by Eyles-Ferris et al. (GCN 43867) and measure the following preliminary photometry calibrated to the r band: Epoch 1: MJD 61098.954 Mag 20.28 ± 0.09 Epoch 2: MJD 61099.011 Mag 21.08 ± 0.10 View this GCN Circular online at https://gcn.nasa.gov/circulars/43868. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41984] EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43867 SUBJECT: EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow DATE: 26/02/27 23:33:12 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> R. A. J. Eyles-Ferris (Leicester), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), J. N. D. van Dalen (Radboud), J. Chacón (PUC), report on behalf of a larger collaboration: We observed the field of the EP/WXT trigger 01709258681 (likely EP260227a) using the Sinistro instrument on the 1-m telescope in Sutherland (South Africa), part of the LCO network. Six 300 s observations were secured in the SDSS r band, with mean time 2026 Feb 27.945 UT (2.47 hr after the WXT trigger). Comparison of our images with archival templates from the Legacy Survey reveals a new object at coordinates (J2000): RA = 14:52:19.94 Dec = -11:24:23.9 Photometry yields r = 20.18 +/- 0.04 (AB) calibrated against nearby stars from the Pan-STARRS catalog, and not corrected for Galactic extinction. We suggest this is the optical counterpart of the EP/WXT trigger 01709258681. View this GCN Circular online at https://gcn.nasa.gov/circulars/43867. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41983] IceCube cascade alert 142200_1517143 retraction
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43866 SUBJECT: IceCube cascade alert 142200_1517143 retraction DATE: 26/02/27 20:54:47 GMT FROM: Erik Blaufuss at University of Maryland, College Park <blaufuss(a)umd.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 27 Feb 26 01:26:48 UT IceCube issued a cascade alert (https://gcn.gsfc.nasa.gov/notices_amon_icecube_cascade/142200_1517143.amon) reporting the detection of a neutrino candidate event with a high probability of being of astrophysical origin. Upon further examination by the IceCube collaboration, the event was found to be likely due to unintended light emission from detector equipment. At the time of this alert, portions of the detector hardware were found to unintentionally producing light in the instrumented volume. Normally, these periods of operation should be excluded from generating alerts. We apologize for any confusion this error may have caused. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/43866. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41982] GRB 260226A: Insight-HXMT/HE detection of the very bright burst
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43865 SUBJECT: GRB 260226A: Insight-HXMT/HE detection of the very bright burst DATE: 26/02/27 16:11:28 GMT FROM: yzh807926(a)163.com Zheng-Hang Yu, Chen-Wei Wang and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2026-02-26T10:38:11.100 (T0), Insight-HXMT/HE detected the long bright burst GRB 260226A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #43840), Fermi/LAT(D. Depalo et al., GCN #43844) , AstroSat-CZTI (Harsha et al., GCN #43846), Glowbug (Woolf et al., GCN #43855), CALET-GBM (Kobayashi et al., GCN #43860), and Konus-Wind(D. Svinkin et al., GCN #43864) The Insight-HXMT/HE light curve mainly consists of two eposides with a T90 of about 76 s. The 1s peak rate, measured from T0+1.5 s, is 15858 cnts/sec. Insight-HXMT/HE detected a total of 264251 counts form this burst. However, the HE detector was suffered from saturation during the brightest peak due to the high-brightness. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260226A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmten.ihep.ac.cn/ View this GCN Circular online at https://gcn.nasa.gov/circulars/43865. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41981] Konus-Wind detection of GRB 260226A
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43864 SUBJECT: Konus-Wind detection of GRB 260226A DATE: 26/02/27 13:52:56 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, A. Tsvetkova, M. Ulanov, and T. Cline on behalf of the Konus-Wind team, report: The bright, long-duration GRB 260226A (Fermi-GBM detection: The Fermi GBM team, GCN 43840; Bissaldi eat al., GCN 43851; BALROG localization: Preis and Greiner, GCN 43843; Fermi-LAT detection: Depalo et al., GCN 43844, 43850; AstroSat-CZTI detection: Harsha et al., GCN 43846; NuSTAR-ACS detection: Waratkar et al., GCN 43854; Glowbug detection: Woolf et al., GCN 43855; CALET-GBM detection: Kobayashi et al., GCN 43860) triggered Konus-Wind at T0=38287.440 s UT (10:38:07.440). The burst light curve shows a very bright, multi-peaked emission pulse which starts at ~T0-9 s and has a duration of ~30 s. This pulse is followed by a weaker, smoothly decaying emission tail, visible up to the end of the KW triggered data record (~T0+250 s). The emission is seen up to ~20 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260226_T38287/ As observed by Konus-Wind, the burst had the total fluence of 7.27(-0.17,+0.17)x10^-4 erg/cm2, and the 64-ms peak flux, measured from T0+10.688 s, of 1.33(-0.06,+0.06)x10^-4 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+142.080 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.93(-0.02,+0.03), the high energy photon index beta = -2.33(-0.07,+0.06), the peak energy Ep = 613(-25,+26) keV (chi2 = 118/97 dof). The spectrum near the maximum count rate (measured from T0+10.240 to T0+10.752 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.64(-0.06,+0.07), the high energy photon index beta = -2.11(-0.08,+0.07), the peak energy Ep = 772(-77,+80) keV (chi2 = 48/57 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/43864. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41980] GRB 260223A: 7DT detection and Medium-band SED of Afterglow
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43863 SUBJECT: GRB 260223A: 7DT detection and Medium-band SED of Afterglow DATE: 26/02/27 12:05:22 GMT FROM: YoungPyo Hong at Seoul National University <evan77333(a)gmail.com> YoungPyo Hong (SNU ARC/SNU), Myungshin Im (SNU ARC/SNU), Donggeun Tak (SNU ARC/SNU), Hyeonho Choi (SNU ARC/SNU), Donghwan Hyun (SNU ARC/SNU), Gregory S.H. Paek (IfA, SNU ARC/SNU), Seo-Won Chang (SNU ARC/SNU), Ji Hoon Kim (SNU ARC/SNU), and Won-Hyeong Lee (SNU ARC/SNU), report on behalf of the 7 Dimensional Telescope (7DT) team: We report optical follow-up observations of GRB26023A (GCN 43808; GCN 43809), conducted with the 7-Dimensional Telescope (7DT), located in Chile. The 7DT follow-up began at 04:44:14 UTC on 2026-02-23, corresponding to T0 + 33 minutes, pointing to a region covering the target localization provided by Fermi (GCN 43808) at RA, DEC = 110.5 deg, -29.4 deg with an uncertainty of 1.7 degree. Initial observations were made with 15, units in 19 medium-band filters as well as r-band filters (20 filters in total). The following table summarizes the observations and the derived 5-sigma upper limits: Filter Mag Mag_err Exposure Date Time ---------------------------------------------------------------------------------------------------- r 19.05 0.08 300.0 2026-02-23T04:49:44.000 m400 >19.02 N/A 300.0 2026-02-23T04:44:14.000 m425 19.28 0.16 300.0 2026-02-23T04:44:31.667 m450 19.48 0.24 300.0 2026-02-23T04:44:16.667 m475 18.97 0.12 300.0 2026-02-23T04:44:15.000 m500 19.62 0.27 300.0 2026-02-23T04:44:20.667 m525 19.48 0.24 300.0 2026-02-23T04:44:23.000 m550 >19.29 N/A 300.0 2026-02-23T04:49:38.000 m575 18.95 0.14 300.0 2026-02-23T04:51:58.000 m600 18.92 0.20 300.0 2026-02-23T04:49:39.333 m625 18.79 0.22 300.0 2026-02-23T04:49:37.000 m650 18.66 0.22 300.0 2026-02-23T04:44:38.000 m675 >18.95 N/A 300.0 2026-02-23T04:44:23.000 m700 18.13 0.18 300.0 2026-02-23T04:44:18.000 m725 >18.46 N/A 300.0 2026-02-23T04:44:23.000 m750 18.23 0.22 300.0 2026-02-23T04:44:20.667 m775 17.99 0.31 300.0 2026-02-23T04:44:43.333 m800 >17.52 N/A 300.0 2026-02-23T04:44:21.667 m825 >17.41 N/A 300.0 2026-02-23T04:44:21.333 m850 >17.05 N/A 300.0 2026-02-23T04:44:21.000 ---------------------------------------------------------------------------------------------------- * Upper limits (marked with '>') are 5-sigma limits The optical counterpart was detected in most filters. Photometric flux calibration was performed using synthetic photometry based on the Gaia DR3 XP catalog (Gaia Collaboration et al. 2022) within the AB magnitude system. Note that no extinction correction has been applied. The 7-Dimensional Telescope (7DT), located in Chile and comprising 20 wide-field telescopes equipped with 40 medium-bandwidth (~25nm) filters, aims to detect optical counterparts of GW sources and conduct the 7-Dimensional Sky Survey (7DS) of the Southern Hemisphere. Further information about the 7DT is available at https://7ds.snu.ac.kr/ and http://gwuniverse.snu.ac.kr/. View this GCN Circular online at https://gcn.nasa.gov/circulars/43863. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41979] EP260214a: VLT/FORS2 optical observations
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43862 SUBJECT: EP260214a: VLT/FORS2 optical observations DATE: 26/02/27 09:53:25 GMT FROM: N. Passaleva at Sapienza University of Rome <niccolo.passaleva(a)uniroma1.it> N. Passaleva, H. Waseem, Yu-Han Yang, and Eleonora Troja (U Rome) report on behalf of the ERC BHianca team: We observed the field of EP260214a (Li et al., GCN 43742) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began 11.3 days after the EP/WXT trigger and were carried out at an average airmass ~1.3 and with an average seeing ~0.45 arcsec in the R filter. At the position of the candidate radio counterpart reported by Ricci et al. (GCN 43845) we detect a faint source (r~26 AB mag). Assuming our observations are dominated by the host galaxy light, we compute a chance alignment of Pcc~1%. We thank the staff at the VLT for the rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43862. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41978] GRB 260225A: WINTER J-band upper limit
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43861 SUBJECT: GRB 260225A: WINTER J-band upper limit DATE: 26/02/27 09:35:03 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> Benjamin Schneider (LAM), Geoffrey Mo (Caltech/Carnegie), Viraj Karambelkar (Columbia), Tomas Ahumada (NOIRLab), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of the SVOM GRB 260225A (Ma et al., GCN Circ. 43829) in the near-infrared with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations started on 2026-02-25 at 09:09:10 UT (17.92 min after the trigger) and consisted of 15 exposures of 120 s in the J-band. The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565) and analysed with STDWeb/STDPipe (Karpov 2025). The photometric calibration was performed using nearby stars from the 2MASS catalog and the magnitude is not corrected for Galactic extinction. In the stacked image, the optical counterpart reported by Ducoin et al., GCN Circ. 43839 and Li et al., GCN Circ. 43838, consistent with the uncatalogued X-ray source detected by EP/FXT position (Yang et al., GCN 43839), is not detected down to the following 3-sigma AB magnitude: J > 19.5 WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research. View this GCN Circular online at https://gcn.nasa.gov/circulars/43861. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41977] GRB 260225A: WINTER J-band upper limit
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43861 SUBJECT: GRB 260225A: WINTER J-band upper limit DATE: 26/02/27 09:35:03 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> Benjamin Schneider (LAM), Geoffrey Mo (Caltech/Carnegie), Viraj Karambelkar (Columbia), Tomas Ahumada (NOIRLab), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of the SVOM GRB 260225A (Ma et al., GCN Circ. 43829) in the near-infrared with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations started on 2026-02-25 at 09:09:10 UT (17.92 min after the trigger) and consisted of 15 exposures of 120 s in the J-band. The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565) and analysed with STDWeb/STDPipe (Karpov 2025). The photometric calibration was performed using nearby stars from the 2MASS catalog and the magnitude is not corrected for Galactic extinction. In the stacked image, the optical counterpart reported by Ducoin et al., GCN Circ. 43839 and Li et al., GCN Circ. 43838, consistent with the uncatalogued X-ray source detected by EP/FXT position (Yang et al., GCN 43839), is not detected down to the following 3-sigma AB magnitude: J > 19.5 WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research. View this GCN Circular online at https://gcn.nasa.gov/circulars/43861. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41976] GRB 260226A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43860 SUBJECT: GRB 260226A: CALET Gamma-Ray Burst Monitor detection DATE: 26/02/27 08:55:16 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> K. Kobayashi (Waseda U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The long GRB 260226A (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN Circ. 43840; BALROG localization: Preis et al., GCN Circ 43843; Fermi-LAT detection: Depalo et al., GCN Circ 43844; AstroSat CZTI detection: Harsha et al., GCN Circ 43846; Fermi-LAT refined analysis: Depalo et al., GCN Circ 43850; Fermi GBM observation: Bissaldi et al., GCN Circ 43851; NuSTAR detection: Waratkar et al., GCN Circ 43854; Glowbug gamma-ray detection: Woolf et al., GCN Circ 43855) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 10:38:04.46 UTC on 26 February 2026 (https://cgbm.calet.jp/cgbm_trigger/flight/1456137494/index.html) The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure that starts at T-3.9 sec, peaks at T+11.1 sec, and ends at T+37.0 sec. The T90 and T50 durations measured by the SGM data are 16.0 +/- 0.3 sec and 8.2 +/- 0.1 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1456137494/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/43860. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41975] GRB 260226A: COLIBRÍ optical upper limits
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43859 SUBJECT: GRB 260226A: COLIBRÍ optical upper limits DATE: 26/02/27 06:16:42 GMT FROM: Camila Angulo Valdez at UNAM <camiangulo(a)astro.unam.mx> Camila Angulo (UNAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the Fermi GRB 260226A (Fermi GBM Team, GCN Circ. 43840, Fermi LAT, GCN Circ. 43844) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-27 02:54:20 to 03:52:25 UTC (from 16.27 to 17.25 hours after the trigger) and obtained 45 minutes of simultaneous exposures in the r and z filters. The data were reduced and coadded with the ASU pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked images, comparing to LS (Dey et al. 2019), we do not detect any new source at the LAT source position (Depalo et al., GCN Circ. 43850) down to the following 5-sigma limits: r > 22.86 z > 21.99 These upper limits are consistent with the ones reported by Lipunov et al. (GCN Circ. 43847, 43848), Konno et al. (GCN Circ. 43852), Saikia et al. (GCN Circ. 43853), and Strausbaugh et al. (GCN Circ. 43858). We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43859. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41974] GRB 260226A: LCOGT Optical Upper Limit
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43858 SUBJECT: GRB 260226A: LCOGT Optical Upper Limit DATE: 26/02/27 03:17:12 GMT FROM: Robert Strausbaugh at Eastern Illinois University <rstrausbaugh(a)eiu.edu> R. Strausbaugh (Eastern Illinois University), A. Cucchiara (NASA) report on behalf of a larger collaboration: We observed the Fermi GRB 260226A field (Fermi GBM Team, GCN 43840) with the LCOGT 1-meter Sinistro instrument at the McDonald Observatory, USA site, on February 27, from 01:46 to 02:18 UT (corresponding to 15.15 to 15.68 hours after the GRB trigger time) with the SDSS r and i filters. We performed a series of 3x300s exposures in i-band and r-band. We do not detect any uncatalogued sources within the Fermi LAT error region (Depalo et al., GCN 43850) in either band. The following 5-sigma upper limits are calculated using the PanSTARRS catalog as reference: r > 21.6 i > 21.1 These magnitudes are not corrected for galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43858. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41973] EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43857 SUBJECT: EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare DATE: 26/02/27 02:06:29 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C. Wu (NAOC), Z. Kang (CHO), L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li, Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of trigger 01709258652 detected by EP/WXT (Yang et al., GCN 43849) with LATIOS on SVOM/C-GFT. Observations started at 2026-02-26T13:56:46 UTC, ~6.77 min after the trigger. A sequence of g-, r-, and i-band images was obtained over ~110 min. Photometry of the suggested flare star LP 435-538 (High Proper Motion Star; Yang et al., GCN 43849) shows a decline from ~13.8 to ~15.4 mag in g-band over ~110 min. The fading was initially fast, then slowed, and was flatter in the r and i bands. This confirms the EP X-ray trigger is associated with a stellar flare. The photometry was calibrated against nearby Pan-STARRS1 stars and no correction for Galactic dust extinction was applied. We thank the observation assistants Hong-Xv Xue and Bo-Wen Li at Jilin ob-servatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/43857. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41972] GRB 260225D: Glowbug gamma-ray detection of a likely short burst
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43856 SUBJECT: GRB 260225D: Glowbug gamma-ray detection of a likely short burst DATE: 26/02/26 20:53:48 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260225D, which was also detected by Konus-Wind (Trig_Time 19:51:32.84) and SVOM/GRM (sb26022503). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-02-25 19:51:28.768 with a duration of 1.98 s and a total significance of about 62 sigma. The light curve comprises two primary peaks at ~T0+0.2s and +1.6s. The best-fit localization is RA, Dec. (J2000, deg) = 94.7, 13.8 with a radius of 7.0 deg (95% confidence), with a highly uncertain systematic uncertainty. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/43856. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41971] GRB 260226A: Glowbug gamma-ray detection
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43855 SUBJECT: GRB 260226A: Glowbug gamma-ray detection DATE: 26/02/26 20:34:03 GMT FROM: Richard S. Woolf at US Naval Research Laboratory <richard.s.woolf.civ(a)us.navy.mil> R. Woolf, C.C. Cheung, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260226A, which was also detected by Fermi GBM (GCN 43840), Fermi LAT (GCN 43844), AstroSat CZTI (GCN 43846), NuSTAR (GCN 43854), and CALET (Trigger 1456137494). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-02-26 10:38:07.336 with a duration of 18.6s and a total significance of about 61.8 sigma. The light curve comprises three primary peaks at ~T0+6s, T0+7.5s and T0+10.5s, followed by three lesser peaks at ~T0+14s, T0+16s and T0+18s. Note that data from ~T0+9.5s to T0+11s suffered from deadtime in various detectors. Additionally, CLLB inorganic scintillation detectors [2], internal to the Glowbug shielded chassis, registered counts above background that are coincidence in time with the main Glowbug detectors. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/43855. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41970] GRB 260226A: NuSTAR detection of bright prompt emission
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43854 SUBJECT: GRB 260226A: NuSTAR detection of bright prompt emission DATE: 26/02/26 20:10:43 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of bright prompt emission from the long-duration GRB 260226A in both the NuSTAR CsI anti-coincidence shields. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm, triggered at 2026-02-26 10:38:05.0, shows a detection of GRB 260226A consistent with the detections by Fermi/GBM (Fermi GBM Team, GCN Circ. 43840) and AstroSat/CZTI (Harsha et al., GCN Circ. 43846). The NuSTAR CsI shield data are recorded at 1 Hz. We detect a single bright peak lasting for ~20-s, consistent with the bright episode from the lightcurve of Fermi/GBM. The peak count rate is ~14000-cps with a baseline rate of ~1000-cps during this time period. We also see clear evidence above 100 keV in the CdZnTe detectors, lasting for ~20-s. The Fermi/LAT localization (Depalo et al., GCN Circ. 43844) at RA = 42.05, Dec = 8.033 implies an offset from the NuSTAR boresight of 91-deg (i.e. from the side of the instrument) and an offset from the geocenter of 68-deg. Lightcurves and analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260226A Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/43854. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41969] GRB 260226A : GROWTH-India Telescope optical observations
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43853 SUBJECT: GRB 260226A : GROWTH-India Telescope optical observations DATE: 26/02/26 19:55:15 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> A.P. Saikia, V. Vijaykumar, T. Mohan, A. Devaraj, S. Patil, V. Swain, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of Fermi GRB 260226A (Fermi GBM team, GCN 43840) also detected by Fermi LAT (Depalo et al., GCN 43844, 43850), with 0.7m GROWTH-India Telescope (GIT). The observations started at 2026-02-26 14:33:34 UT, i.e 3.9 hours after the GBM trigger. We tiled the LAT localization region, observed the field at a position angle of approximately 45 degrees, and covered about 74% of the localization area. No new transients were detected within the observed region. Each exposure was taken in the r′ filter with an exposure time of 300 seconds. The photometric results are summarized below: Tile Number | Tmid - T0 (hours) | RA (deg) | Dec (deg) |Upper limit (5 sigma)(AB) | | ------------ | ------ | --------------- | ------------------------- | -------------- | | 1 | 3.95 | 42.05 | 8.033 | 19.7 | | 2 | 4.03 | 41.83 | 7.713 | 19.6 | | 3 | 4.12 | 41.83 | 7.873 | 19.9 | | 4 | 4.21 | 41.83 | 8.033 | 19.8 | | 5 | 4.30 | 41.83 | 8.193 | 19.6 | | 6 | 4.39 | 41.83 | 8.353 | 19.7 | | 7 | 4.47 | 41.94 | 7.713 | 19.6 | | 8 | 4.56 | 41.94 | 7.873 | 19.7 | | 9 | 4.65 | 41.94 | 8.033 | 19.6 | | 10 | 4.75 | 41.94 | 8.193 | 19.5 | | 11 | 4.84 | 41.94 | 8.353 | 19.6 | | 12 | 4.93 | 42.05 | 7.713 | 19.4 | | 13 | 5.02 | 42.05 | 7.873 | 19.2 | | 14 | 5.10 | 42.05 | 8.193 | 19.3 | | 15 | 5.19 | 42.05 | 8.353 | 19.2 | | 16 | 5.28 | 42.16 | 7.873 | 19.0 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Our results are consistent with other optical non-detections (Lipunov et al., GCN 43847,43848, Konno et al., 43852) The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 8' x 11' field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/43853. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41968] GRB 260226A: LAST optical upper limit
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43852 SUBJECT: GRB 260226A: LAST optical upper limit DATE: 26/02/26 19:42:00 GMT FROM: Ruslan Konno at Weizmann Institute of Science <ruslankonno(a)gmail.com> R. Konno (WIS), S. Garrappa (WIS), E. A. Zimmerman (WIS), A. Horowicz (WIS), E. O. Ofek (WIS), S. Ben-Ami (WIS), D. Polishook (WIS), O. Yaron (WIS), S. Fainer (WIS), A. Krassilchtchikov (WIS), Y. M. Shani (WIS), E. Segre (WIS), A. Gal-Yam (WIS), and S. Spitzer (WIS) report on behalf of the LAST Collaboration. We report observations of GRB 260226A, reported by Fermi-GBM (Fermi GBM Team, GCN 43840), as well as by Fermi-LAT (Depalo et al, GCN 43844) and AstroSat CZTI (Harsha et al, GCN 43846). Observations were conducted with the Large Array Survey Telescope (LAST; Ofek et al. 2023, PASP 135, 5001; Ben-Ami et al. 2023, PASP 135, 5002). Observations of GRB 260226A were taken over 10 sequential epochs in clear band (similar to the Gaia Bp band) with 4 telescopes simultaneously. The first epoch began at 2026-02-26 16:30:51UTC (T-T0 = 5.88 h). Each epoch consists of 20x20s exposures per telescope. We coadd a total of 4x120x20s (mid. T-T0=6.67 h) exposure images and perform image subtraction using a reference image of the field. We do not detect any clear new optical source up to a 5-sigma limiting magnitude of 20.15 (AB) within the error region reported in Bissaldi et al., GCN 43851. Performing image subtraction between the latest (mid. T-T0 = 7.31 h) and earliest (mid. T-T0 = 5.94 h) 20x20s exposure images also shows no source brighter than 19.4 mag decaying by more than 0.5 mag. Our results are consistent with other optical non-detections (Lipunov et al., GCN 43847,43848). LAST is a survey telescope array of the Weizmann Astrophysical Observatory (https://www.weizmann.ac.il/wao/) View this GCN Circular online at https://gcn.nasa.gov/circulars/43852. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41967] GRB 260226A: Fermi GBM observation
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43851 SUBJECT: GRB 260226A: Fermi GBM observation DATE: 26/02/26 16:21:05 GMT FROM: Elisabetta Bissaldi at Politecnico and INFN Bari <elisabetta.bissaldi(a)ba.infn.it> E. Bissaldi (Politecnico and INFN Bari), O.J. Roberts (Uni. of Galway, Ireland), P. Veres (UAH) and A. von Kienlin (MPE) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 10:39:05 UT on 26 February 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260226A (trigger 793795080/260226443), which was also detected by Fermi-LAT (Depalo et al. 2026, GCN 43844 and 43850) and AstroSat CZTI (Harsha et al. 2026, GCN 43846). The Fermi GBM on-ground location (GCN 43840) is consistent with the Fermi-LAT position. The angle from the Fermi LAT boresight is 26 degrees. The GBM light curve consists of a very bright and structured emission episode with a duration (T90) of about 82 s (50-300 keV). The time-averaged spectrum from T0 to T0+81 s is best fit by a Band function with Epeak = 723 +/- 8 keV, alpha = -0.95 +/- 0.01, and beta = -2.47 +/- 0.02. The event fluence (10-1000 keV) in this time interval is (4.54 +/- 0.01)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+19.3 s in the 10-1000 keV band is 166 +/- 2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/43851. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41966] GRB 260226A: Fermi-LAT refined analysis
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43850 SUBJECT: GRB 260226A: Fermi-LAT refined analysis DATE: 26/02/26 16:15:30 GMT FROM: Davide Depalo at Politecnico and INFN Bari <davide.depalo(a)ba.infn.it> D. Depalo (Politecnico and INFN Bari), E. Bissaldi (Politecnico and INFN Bari), A. Holzmann Airasca (UniTrento and INFN Bari), R. Gupta (NASA/GSFC), F. Longo (University and INFN, Trieste), S. Lopez (CNRS / IN2P3), R. Martinelli (University and INFN, Trieste), and J. L. Racusin (NASA/GSFC) report on behalf of the Fermi-LAT team: At 10:38:18.84 UT on Feb 26th, 2026 Fermi-LAT triggered and detected high-energy emission from GRB 260226A (Depalo et al., GCN Circular 43844), which was also detected by Fermi-GBM (trigger 793795080 / 260226443, GCN Circular 43840) and Astrosat (Harsha et al., GCN Circular 43846). The best LAT on-ground location is found to be RA, Dec = 41.93, 7.73 (J2000) with an error radius of 0.11 deg (90 % containment, statistical error only). This was 26 deg from the LAT boresight at the time of the trigger. The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance. The photon flux above 100 MeV in the time interval 0 - 1.5 ks after the GBM trigger is (1.50 ± 0.06)E-4 ph/cm2/s. The estimated photon index above 100 MeV is -3.25 ± 0.08. The highest energy photon has an energy of 1.1 GeV and occurs at 420 s after trigger time. The Fermi-LAT point of contact for this burst is Niccolò Di Lalla (niccolo.dilalla(a)stanford.edu) The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/43850. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41965] The EP-WXT trigger 01709258652 is likely a flaring star
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43849 SUBJECT: The EP-WXT trigger 01709258652 is likely a flaring star DATE: 26/02/26 16:09:54 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Guojiong Yang, Tong Zhao(Nao, CAS), Zecheng Zou(NJU) and Wenda Zhang(Nao, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709258652 at the time of 2026-02-26T13:49:59(UTC), is likely a stellar flare associated with LP 435-538. The WXT position of the source is R.A. = 190.202 deg, DEC = 19.917 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The estimated flux of the flare is around 8e-11 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 2.071e+31 erg/s. A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. An onboard alert was generated by FXT during this observation and the FXT position is R.A. = 190.1724 deg, DEC = 19.9231 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). The FXT position is consistent with the star LP 435-538. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43849. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41964] LAT GRB260226.44: Global MASTER-Net observations report
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43848 SUBJECT: LAT GRB260226.44: Global MASTER-Net observations report DATE: 26/02/26 15:44:21 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the LAT GRB260226.44 (trigger No 793795080,02h 47m 41.04s , +07d 43m 12.0s, R=0.105833) errorbox 16332 sec after trigger time at 2026-02-26 15:10:31 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 81 deg. The sun altitude is -40.1 deg. The galactic latitude b = -45 deg., longitude l = 167 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3157390 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 16337 | 2026-02-26 15:10:31 | MASTER-Tunka | (02h 46m 41.03s , +08d 13m 10.9s) | C | 10 | 16.4 | 16347 | 2026-02-26 15:10:31 | MASTER-Tunka | (02h 46m 41.03s , +08d 13m 11.0s) | C | 30 | 17.0 | Coadd 16338 | 2026-02-26 15:10:31 | MASTER-Tunka | (02h 46m 22.49s , +08d 16m 39.4s) | C | 10 | 16.0 | 16362 | 2026-02-26 15:10:56 | MASTER-Tunka | (02h 46m 34.45s , +08d 12m 33.1s) | C | 10 | 16.5 | 16363 | 2026-02-26 15:10:56 | MASTER-Tunka | (02h 46m 16.08s , +08d 15m 59.0s) | C | 10 | 15.8 | 16384 | 2026-02-26 15:11:18 | MASTER-Tunka | (02h 46m 33.55s , +08d 13m 32.1s) | C | 10 | 16.4 | 16384 | 2026-02-26 15:11:18 | MASTER-Tunka | (02h 46m 15.50s , +08d 16m 58.7s) | C | 10 | 16.0 | 16408 | 2026-02-26 15:11:41 | MASTER-Tunka | (02h 46m 40.83s , +08d 12m 31.4s) | C | 10 | 16.4 | 16408 | 2026-02-26 15:11:41 | MASTER-Tunka | (02h 46m 22.76s , +08d 15m 57.8s) | C | 10 | 15.9 | 16430 | 2026-02-26 15:12:04 | MASTER-Tunka | (02h 46m 33.93s , +08d 11m 31.6s) | C | 10 | 16.3 | 16431 | 2026-02-26 15:12:04 | MASTER-Tunka | (02h 46m 15.91s , +08d 14m 57.9s) | C | 10 | 15.8 | 16454 | 2026-02-26 15:12:27 | MASTER-Tunka | (02h 46m 40.26s , +08d 11m 42.7s) | C | 10 | 16.1 | 16454 | 2026-02-26 15:12:27 | MASTER-Tunka | (02h 46m 22.16s , +08d 15m 07.0s) | C | 10 | 15.3 | 16478 | 2026-02-26 15:12:52 | MASTER-Tunka | (02h 46m 37.35s , +08d 12m 56.4s) | C | 10 | 15.0 | 16479 | 2026-02-26 15:12:52 | MASTER-Tunka | (02h 46m 19.39s , +08d 16m 23.6s) | C | 10 | 14.8 | 16503 | 2026-02-26 15:13:17 | MASTER-Tunka | (02h 46m 37.23s , +08d 11m 26.2s) | C | 10 | 14.7 | 16503 | 2026-02-26 15:13:17 | MASTER-Tunka | (02h 46m 19.51s , +08d 14m 56.8s) | C | 10 | 14.6 | 16526 | 2026-02-26 15:13:40 | MASTER-Tunka | (02h 46m 39.73s , +08d 13m 11.3s) | C | 10 | 15.8 | 16527 | 2026-02-26 15:13:40 | MASTER-Tunka | (02h 46m 21.80s , +08d 16m 35.6s) | C | 10 | 15.2 | 16550 | 2026-02-26 15:14:03 | MASTER-Tunka | (02h 46m 33.44s , +08d 12m 29.2s) | C | 10 | 15.3 | 16550 | 2026-02-26 15:14:03 | MASTER-Tunka | (02h 46m 15.66s , +08d 15m 55.3s) | C | 10 | 14.9 | 16576 | 2026-02-26 15:14:30 | MASTER-Tunka | (02h 46m 34.78s , +08d 13m 28.4s) | C | 10 | 15.3 | 16577 | 2026-02-26 15:14:30 | MASTER-Tunka | (02h 46m 17.03s , +08d 16m 54.9s) | C | 10 | 15.1 | 16607 | 2026-02-26 15:15:01 | MASTER-Tunka | (02h 46m 40.60s , +08d 12m 25.3s) | C | 10 | 15.4 | 16607 | 2026-02-26 15:15:01 | MASTER-Tunka | (02h 46m 22.93s , +08d 15m 51.3s) | C | 10 | 14.9 | 16630 | 2026-02-26 15:15:23 | MASTER-Tunka | (02h 46m 33.66s , +08d 11m 26.0s) | C | 10 | 15.4 | 16630 | 2026-02-26 15:15:23 | MASTER-Tunka | (02h 46m 16.01s , +08d 14m 52.2s) | C | 10 | 15.1 | 16653 | 2026-02-26 15:15:46 | MASTER-Tunka | (02h 46m 41.11s , +08d 11m 47.9s) | C | 10 | 16.1 | 16653 | 2026-02-26 15:15:46 | MASTER-Tunka | (02h 46m 24.19s , +08d 15m 25.7s) | C | 10 | 14.8 | 16676 | 2026-02-26 15:16:09 | MASTER-Tunka | (02h 46m 37.35s , +08d 13m 13.3s) | C | 10 | 15.6 | 16676 | 2026-02-26 15:16:09 | MASTER-Tunka | (02h 46m 19.66s , +08d 16m 38.3s) | C | 10 | 15.2 | 16832 | 2026-02-26 15:18:43 | MASTER-Tunka | (02h 46m 34.69s , +08d 13m 32.9s) | C | 15 | 16.1 | 16832 | 2026-02-26 15:18:43 | MASTER-Tunka | (02h 46m 16.54s , +08d 16m 52.9s) | C | 15 | 15.5 | 16859 | 2026-02-26 15:19:09 | MASTER-Tunka | (02h 46m 40.75s , +08d 12m 32.7s) | C | 15 | 16.0 | 16859 | 2026-02-26 15:19:09 | MASTER-Tunka | (02h 46m 22.88s , +08d 15m 54.8s) | C | 15 | 15.4 | 16884 | 2026-02-26 15:19:37 | MASTER-Tunka | (02h 46m 35.06s , +08d 11m 32.5s) | C | 10 | 15.8 | 16884 | 2026-02-26 15:19:38 | MASTER-Tunka | (02h 46m 17.19s , +08d 14m 52.2s) | C | 10 | 15.2 | 16908 | 2026-02-26 15:20:02 | MASTER-Tunka | (02h 46m 41.38s , +08d 11m 36.4s) | C | 10 | 16.1 | 16908 | 2026-02-26 15:20:02 | MASTER-Tunka | (02h 46m 23.62s , +08d 14m 57.3s) | C | 10 | 15.4 | 16947 | 2026-02-26 15:20:41 | MASTER-Tunka | (02h 46m 38.12s , +08d 13m 07.4s) | C | 10 | 16.1 | 16947 | 2026-02-26 15:20:41 | MASTER-Tunka | (02h 46m 20.25s , +08d 16m 28.2s) | C | 10 | 15.4 | 16969 | 2026-02-26 15:21:02 | MASTER-Tunka | (02h 46m 38.11s , +08d 11m 37.5s) | C | 10 | 16.0 | 16969 | 2026-02-26 15:21:03 | MASTER-Tunka | (02h 46m 19.74s , +08d 14m 48.1s) | C | 10 | 15.5 | 16993 | 2026-02-26 15:21:26 | MASTER-Tunka | (02h 46m 40.15s , +08d 13m 08.3s) | C | 10 | 15.8 | 16993 | 2026-02-26 15:21:26 | MASTER-Tunka | (02h 46m 22.32s , +08d 16m 29.7s) | C | 10 | 15.3 | 17017 | 2026-02-26 15:21:51 | MASTER-Tunka | (02h 46m 35.71s , +08d 12m 33.0s) | C | 10 | 16.1 | 17017 | 2026-02-26 15:21:51 | MASTER-Tunka | (02h 46m 17.88s , +08d 15m 54.5s) | C | 10 | 15.4 | 17042 | 2026-02-26 15:22:16 | MASTER-Tunka | (02h 46m 35.36s , +08d 13m 30.6s) | C | 10 | 15.9 | 17042 | 2026-02-26 15:22:16 | MASTER-Tunka | (02h 46m 17.46s , +08d 16m 51.1s) | C | 10 | 15.2 | 17068 | 2026-02-26 15:22:41 | MASTER-Tunka | (02h 46m 40.47s , +08d 12m 31.9s) | C | 10 | 15.9 | 17068 | 2026-02-26 15:22:41 | MASTER-Tunka | (02h 46m 22.01s , +08d 15m 41.5s) | C | 10 | 15.5 | 17092 | 2026-02-26 15:23:05 | MASTER-Tunka | (02h 46m 35.02s , +08d 11m 33.0s) | C | 10 | 15.7 | 17092 | 2026-02-26 15:23:05 | MASTER-Tunka | (02h 46m 17.26s , +08d 14m 55.9s) | C | 10 | 15.2 | 17114 | 2026-02-26 15:23:27 | MASTER-Tunka | (02h 46m 41.21s , +08d 11m 47.1s) | C | 10 | 15.8 | 17114 | 2026-02-26 15:23:27 | MASTER-Tunka | (02h 46m 23.36s , +08d 15m 07.6s) | C | 10 | 15.5 | 17139 | 2026-02-26 15:23:52 | MASTER-Tunka | (02h 46m 38.16s , +08d 13m 22.7s) | C | 10 | 15.8 | 17139 | 2026-02-26 15:23:52 | MASTER-Tunka | (02h 46m 19.90s , +08d 16m 35.1s) | C | 10 | 15.3 | 17163 | 2026-02-26 15:24:16 | MASTER-Tunka | (02h 46m 38.13s , +08d 11m 34.8s) | C | 10 | 15.8 | 17163 | 2026-02-26 15:24:16 | MASTER-Tunka | (02h 46m 20.56s , +08d 15m 02.0s) | C | 10 | 15.3 | 17187 | 2026-02-26 15:24:40 | MASTER-Tunka | (02h 46m 41.99s , +08d 13m 24.9s) | C | 10 | 16.0 | 17187 | 2026-02-26 15:24:40 | MASTER-Tunka | (02h 46m 24.35s , +08d 16m 51.1s) | C | 10 | 15.3 | 17209 | 2026-02-26 15:25:03 | MASTER-Tunka | (02h 46m 35.05s , +08d 12m 30.7s) | C | 10 | 15.9 | 17209 | 2026-02-26 15:25:03 | MASTER-Tunka | (02h 46m 17.41s , +08d 15m 58.0s) | C | 10 | 15.2 | 17231 | 2026-02-26 15:25:25 | MASTER-Tunka | (02h 46m 34.52s , +08d 13m 31.1s) | C | 10 | 15.8 | 17231 | 2026-02-26 15:25:25 | MASTER-Tunka | (02h 46m 16.43s , +08d 16m 48.8s) | C | 10 | 15.2 | 17258 | 2026-02-26 15:25:51 | MASTER-Tunka | (02h 46m 41.61s , +08d 12m 31.5s) | C | 10 | 15.8 | 17258 | 2026-02-26 15:25:51 | MASTER-Tunka | (02h 46m 24.00s , +08d 15m 56.3s) | C | 10 | 15.3 | 17281 | 2026-02-26 15:26:14 | MASTER-Tunka | (02h 46m 34.33s , +08d 11m 30.5s) | C | 10 | 15.8 | 17281 | 2026-02-26 15:26:14 | MASTER-Tunka | (02h 46m 16.53s , +08d 14m 52.9s) | C | 10 | 15.2 | 17305 | 2026-02-26 15:26:38 | MASTER-Tunka | (02h 46m 40.80s , +08d 11m 40.7s) | C | 10 | 16.0 | 17305 | 2026-02-26 15:26:38 | MASTER-Tunka | (02h 46m 22.93s , +08d 14m 59.1s) | C | 10 | 15.2 | 17330 | 2026-02-26 15:27:03 | MASTER-Tunka | (02h 46m 37.97s , +08d 13m 22.4s) | C | 10 | 15.7 | 17330 | 2026-02-26 15:27:03 | MASTER-Tunka | (02h 46m 20.40s , +08d 16m 48.5s) | C | 10 | 15.2 | 17355 | 2026-02-26 15:27:29 | MASTER-Tunka | (02h 46m 38.21s , +08d 11m 42.8s) | C | 10 | 15.8 | 17356 | 2026-02-26 15:27:29 | MASTER-Tunka | (02h 46m 20.53s , +08d 15m 06.2s) | C | 10 | 15.2 | 17379 | 2026-02-26 15:27:52 | MASTER-Tunka | (02h 46m 40.47s , +08d 13m 29.7s) | C | 10 | 15.8 | 17379 | 2026-02-26 15:27:52 | MASTER-Tunka | (02h 46m 22.85s , +08d 16m 53.5s) | C | 10 | 15.2 | 17404 | 2026-02-26 15:28:18 | MASTER-Tunka | (02h 46m 34.36s , +08d 12m 28.4s) | C | 10 | 15.8 | 17404 | 2026-02-26 15:28:18 | MASTER-Tunka | (02h 46m 16.62s , +08d 15m 50.9s) | C | 10 | 15.2 | 17428 | 2026-02-26 15:28:41 | MASTER-Tunka | (02h 46m 35.07s , +08d 13m 27.8s) | C | 10 | 15.7 | 17428 | 2026-02-26 15:28:42 | MASTER-Tunka | (02h 46m 17.38s , +08d 16m 50.8s) | C | 10 | 15.1 | 17457 | 2026-02-26 15:29:10 | MASTER-Tunka | (02h 46m 39.98s , +08d 12m 26.4s) | C | 10 | 15.7 | 17457 | 2026-02-26 15:29:10 | MASTER-Tunka | (02h 46m 22.36s , +08d 15m 50.5s) | C | 10 | 15.1 | 17480 | 2026-02-26 15:29:33 | MASTER-Tunka | (02h 46m 34.99s , +08d 11m 25.9s) | C | 10 | 15.7 | 17480 | 2026-02-26 15:29:33 | MASTER-Tunka | (02h 46m 17.41s , +08d 14m 49.8s) | C | 10 | 15.2 | 17507 | 2026-02-26 15:30:01 | MASTER-Tunka | (02h 46m 40.94s , +08d 11m 33.4s) | C | 10 | 15.7 | 17507 | 2026-02-26 15:30:01 | MASTER-Tunka | (02h 46m 23.14s , +08d 14m 53.9s) | C | 10 | 15.1 | 17531 | 2026-02-26 15:30:24 | MASTER-Tunka | (02h 46m 37.85s , +08d 13m 16.0s) | C | 10 | 15.7 | 17531 | 2026-02-26 15:30:24 | MASTER-Tunka | (02h 46m 20.32s , +08d 16m 41.5s) | C | 10 | 15.0 | 17553 | 2026-02-26 15:30:46 | MASTER-Tunka | (02h 46m 37.93s , +08d 11m 54.6s) | C | 10 | 15.7 | 17553 | 2026-02-26 15:30:46 | MASTER-Tunka | (02h 46m 20.09s , +08d 15m 13.6s) | C | 10 | 15.0 | 17576 | 2026-02-26 15:31:10 | MASTER-Tunka | (02h 46m 40.42s , +08d 12m 54.8s) | C | 10 | 15.6 | 17576 | 2026-02-26 15:31:10 | MASTER-Tunka | (02h 46m 22.84s , +08d 16m 17.8s) | C | 10 | 14.9 | 17600 | 2026-02-26 15:31:33 | MASTER-Tunka | (02h 46m 34.70s , +08d 12m 22.5s) | C | 10 | 15.6 | 17600 | 2026-02-26 15:31:33 | MASTER-Tunka | (02h 46m 16.99s , +08d 15m 44.7s) | C | 10 | 15.1 | 17626 | 2026-02-26 15:32:00 | MASTER-Tunka | (02h 46m 35.77s , +08d 13m 23.5s) | C | 10 | 15.6 | 17626 | 2026-02-26 15:32:00 | MASTER-Tunka | (02h 46m 18.12s , +08d 16m 47.2s) | C | 10 | 15.1 | 17650 | 2026-02-26 15:32:23 | MASTER-Tunka | (02h 46m 40.81s , +08d 12m 21.6s) | C | 10 | 15.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43848. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41963] LAT GRB260226.44: Global MASTER-Net observations report
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43848 SUBJECT: LAT GRB260226.44: Global MASTER-Net observations report DATE: 26/02/26 15:44:21 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the LAT GRB260226.44 (trigger No 793795080,02h 47m 41.04s , +07d 43m 12.0s, R=0.105833) errorbox 16332 sec after trigger time at 2026-02-26 15:10:31 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 81 deg. The sun altitude is -40.1 deg. The galactic latitude b = -45 deg., longitude l = 167 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3157390 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 16337 | 2026-02-26 15:10:31 | MASTER-Tunka | (02h 46m 41.03s , +08d 13m 10.9s) | C | 10 | 16.4 | 16347 | 2026-02-26 15:10:31 | MASTER-Tunka | (02h 46m 41.03s , +08d 13m 11.0s) | C | 30 | 17.0 | Coadd 16338 | 2026-02-26 15:10:31 | MASTER-Tunka | (02h 46m 22.49s , +08d 16m 39.4s) | C | 10 | 16.0 | 16362 | 2026-02-26 15:10:56 | MASTER-Tunka | (02h 46m 34.45s , +08d 12m 33.1s) | C | 10 | 16.5 | 16363 | 2026-02-26 15:10:56 | MASTER-Tunka | (02h 46m 16.08s , +08d 15m 59.0s) | C | 10 | 15.8 | 16384 | 2026-02-26 15:11:18 | MASTER-Tunka | (02h 46m 33.55s , +08d 13m 32.1s) | C | 10 | 16.4 | 16384 | 2026-02-26 15:11:18 | MASTER-Tunka | (02h 46m 15.50s , +08d 16m 58.7s) | C | 10 | 16.0 | 16408 | 2026-02-26 15:11:41 | MASTER-Tunka | (02h 46m 40.83s , +08d 12m 31.4s) | C | 10 | 16.4 | 16408 | 2026-02-26 15:11:41 | MASTER-Tunka | (02h 46m 22.76s , +08d 15m 57.8s) | C | 10 | 15.9 | 16430 | 2026-02-26 15:12:04 | MASTER-Tunka | (02h 46m 33.93s , +08d 11m 31.6s) | C | 10 | 16.3 | 16431 | 2026-02-26 15:12:04 | MASTER-Tunka | (02h 46m 15.91s , +08d 14m 57.9s) | C | 10 | 15.8 | 16454 | 2026-02-26 15:12:27 | MASTER-Tunka | (02h 46m 40.26s , +08d 11m 42.7s) | C | 10 | 16.1 | 16454 | 2026-02-26 15:12:27 | MASTER-Tunka | (02h 46m 22.16s , +08d 15m 07.0s) | C | 10 | 15.3 | 16478 | 2026-02-26 15:12:52 | MASTER-Tunka | (02h 46m 37.35s , +08d 12m 56.4s) | C | 10 | 15.0 | 16479 | 2026-02-26 15:12:52 | MASTER-Tunka | (02h 46m 19.39s , +08d 16m 23.6s) | C | 10 | 14.8 | 16503 | 2026-02-26 15:13:17 | MASTER-Tunka | (02h 46m 37.23s , +08d 11m 26.2s) | C | 10 | 14.7 | 16503 | 2026-02-26 15:13:17 | MASTER-Tunka | (02h 46m 19.51s , +08d 14m 56.8s) | C | 10 | 14.6 | 16526 | 2026-02-26 15:13:40 | MASTER-Tunka | (02h 46m 39.73s , +08d 13m 11.3s) | C | 10 | 15.8 | 16527 | 2026-02-26 15:13:40 | MASTER-Tunka | (02h 46m 21.80s , +08d 16m 35.6s) | C | 10 | 15.2 | 16550 | 2026-02-26 15:14:03 | MASTER-Tunka | (02h 46m 33.44s , +08d 12m 29.2s) | C | 10 | 15.3 | 16550 | 2026-02-26 15:14:03 | MASTER-Tunka | (02h 46m 15.66s , +08d 15m 55.3s) | C | 10 | 14.9 | 16576 | 2026-02-26 15:14:30 | MASTER-Tunka | (02h 46m 34.78s , +08d 13m 28.4s) | C | 10 | 15.3 | 16577 | 2026-02-26 15:14:30 | MASTER-Tunka | (02h 46m 17.03s , +08d 16m 54.9s) | C | 10 | 15.1 | 16607 | 2026-02-26 15:15:01 | MASTER-Tunka | (02h 46m 40.60s , +08d 12m 25.3s) | C | 10 | 15.4 | 16607 | 2026-02-26 15:15:01 | MASTER-Tunka | (02h 46m 22.93s , +08d 15m 51.3s) | C | 10 | 14.9 | 16630 | 2026-02-26 15:15:23 | MASTER-Tunka | (02h 46m 33.66s , +08d 11m 26.0s) | C | 10 | 15.4 | 16630 | 2026-02-26 15:15:23 | MASTER-Tunka | (02h 46m 16.01s , +08d 14m 52.2s) | C | 10 | 15.1 | 16653 | 2026-02-26 15:15:46 | MASTER-Tunka | (02h 46m 41.11s , +08d 11m 47.9s) | C | 10 | 16.1 | 16653 | 2026-02-26 15:15:46 | MASTER-Tunka | (02h 46m 24.19s , +08d 15m 25.7s) | C | 10 | 14.8 | 16676 | 2026-02-26 15:16:09 | MASTER-Tunka | (02h 46m 37.35s , +08d 13m 13.3s) | C | 10 | 15.6 | 16676 | 2026-02-26 15:16:09 | MASTER-Tunka | (02h 46m 19.66s , +08d 16m 38.3s) | C | 10 | 15.2 | 16832 | 2026-02-26 15:18:43 | MASTER-Tunka | (02h 46m 34.69s , +08d 13m 32.9s) | C | 15 | 16.1 | 16832 | 2026-02-26 15:18:43 | MASTER-Tunka | (02h 46m 16.54s , +08d 16m 52.9s) | C | 15 | 15.5 | 16859 | 2026-02-26 15:19:09 | MASTER-Tunka | (02h 46m 40.75s , +08d 12m 32.7s) | C | 15 | 16.0 | 16859 | 2026-02-26 15:19:09 | MASTER-Tunka | (02h 46m 22.88s , +08d 15m 54.8s) | C | 15 | 15.4 | 16884 | 2026-02-26 15:19:37 | MASTER-Tunka | (02h 46m 35.06s , +08d 11m 32.5s) | C | 10 | 15.8 | 16884 | 2026-02-26 15:19:38 | MASTER-Tunka | (02h 46m 17.19s , +08d 14m 52.2s) | C | 10 | 15.2 | 16908 | 2026-02-26 15:20:02 | MASTER-Tunka | (02h 46m 41.38s , +08d 11m 36.4s) | C | 10 | 16.1 | 16908 | 2026-02-26 15:20:02 | MASTER-Tunka | (02h 46m 23.62s , +08d 14m 57.3s) | C | 10 | 15.4 | 16947 | 2026-02-26 15:20:41 | MASTER-Tunka | (02h 46m 38.12s , +08d 13m 07.4s) | C | 10 | 16.1 | 16947 | 2026-02-26 15:20:41 | MASTER-Tunka | (02h 46m 20.25s , +08d 16m 28.2s) | C | 10 | 15.4 | 16969 | 2026-02-26 15:21:02 | MASTER-Tunka | (02h 46m 38.11s , +08d 11m 37.5s) | C | 10 | 16.0 | 16969 | 2026-02-26 15:21:03 | MASTER-Tunka | (02h 46m 19.74s , +08d 14m 48.1s) | C | 10 | 15.5 | 16993 | 2026-02-26 15:21:26 | MASTER-Tunka | (02h 46m 40.15s , +08d 13m 08.3s) | C | 10 | 15.8 | 16993 | 2026-02-26 15:21:26 | MASTER-Tunka | (02h 46m 22.32s , +08d 16m 29.7s) | C | 10 | 15.3 | 17017 | 2026-02-26 15:21:51 | MASTER-Tunka | (02h 46m 35.71s , +08d 12m 33.0s) | C | 10 | 16.1 | 17017 | 2026-02-26 15:21:51 | MASTER-Tunka | (02h 46m 17.88s , +08d 15m 54.5s) | C | 10 | 15.4 | 17042 | 2026-02-26 15:22:16 | MASTER-Tunka | (02h 46m 35.36s , +08d 13m 30.6s) | C | 10 | 15.9 | 17042 | 2026-02-26 15:22:16 | MASTER-Tunka | (02h 46m 17.46s , +08d 16m 51.1s) | C | 10 | 15.2 | 17068 | 2026-02-26 15:22:41 | MASTER-Tunka | (02h 46m 40.47s , +08d 12m 31.9s) | C | 10 | 15.9 | 17068 | 2026-02-26 15:22:41 | MASTER-Tunka | (02h 46m 22.01s , +08d 15m 41.5s) | C | 10 | 15.5 | 17092 | 2026-02-26 15:23:05 | MASTER-Tunka | (02h 46m 35.02s , +08d 11m 33.0s) | C | 10 | 15.7 | 17092 | 2026-02-26 15:23:05 | MASTER-Tunka | (02h 46m 17.26s , +08d 14m 55.9s) | C | 10 | 15.2 | 17114 | 2026-02-26 15:23:27 | MASTER-Tunka | (02h 46m 41.21s , +08d 11m 47.1s) | C | 10 | 15.8 | 17114 | 2026-02-26 15:23:27 | MASTER-Tunka | (02h 46m 23.36s , +08d 15m 07.6s) | C | 10 | 15.5 | 17139 | 2026-02-26 15:23:52 | MASTER-Tunka | (02h 46m 38.16s , +08d 13m 22.7s) | C | 10 | 15.8 | 17139 | 2026-02-26 15:23:52 | MASTER-Tunka | (02h 46m 19.90s , +08d 16m 35.1s) | C | 10 | 15.3 | 17163 | 2026-02-26 15:24:16 | MASTER-Tunka | (02h 46m 38.13s , +08d 11m 34.8s) | C | 10 | 15.8 | 17163 | 2026-02-26 15:24:16 | MASTER-Tunka | (02h 46m 20.56s , +08d 15m 02.0s) | C | 10 | 15.3 | 17187 | 2026-02-26 15:24:40 | MASTER-Tunka | (02h 46m 41.99s , +08d 13m 24.9s) | C | 10 | 16.0 | 17187 | 2026-02-26 15:24:40 | MASTER-Tunka | (02h 46m 24.35s , +08d 16m 51.1s) | C | 10 | 15.3 | 17209 | 2026-02-26 15:25:03 | MASTER-Tunka | (02h 46m 35.05s , +08d 12m 30.7s) | C | 10 | 15.9 | 17209 | 2026-02-26 15:25:03 | MASTER-Tunka | (02h 46m 17.41s , +08d 15m 58.0s) | C | 10 | 15.2 | 17231 | 2026-02-26 15:25:25 | MASTER-Tunka | (02h 46m 34.52s , +08d 13m 31.1s) | C | 10 | 15.8 | 17231 | 2026-02-26 15:25:25 | MASTER-Tunka | (02h 46m 16.43s , +08d 16m 48.8s) | C | 10 | 15.2 | 17258 | 2026-02-26 15:25:51 | MASTER-Tunka | (02h 46m 41.61s , +08d 12m 31.5s) | C | 10 | 15.8 | 17258 | 2026-02-26 15:25:51 | MASTER-Tunka | (02h 46m 24.00s , +08d 15m 56.3s) | C | 10 | 15.3 | 17281 | 2026-02-26 15:26:14 | MASTER-Tunka | (02h 46m 34.33s , +08d 11m 30.5s) | C | 10 | 15.8 | 17281 | 2026-02-26 15:26:14 | MASTER-Tunka | (02h 46m 16.53s , +08d 14m 52.9s) | C | 10 | 15.2 | 17305 | 2026-02-26 15:26:38 | MASTER-Tunka | (02h 46m 40.80s , +08d 11m 40.7s) | C | 10 | 16.0 | 17305 | 2026-02-26 15:26:38 | MASTER-Tunka | (02h 46m 22.93s , +08d 14m 59.1s) | C | 10 | 15.2 | 17330 | 2026-02-26 15:27:03 | MASTER-Tunka | (02h 46m 37.97s , +08d 13m 22.4s) | C | 10 | 15.7 | 17330 | 2026-02-26 15:27:03 | MASTER-Tunka | (02h 46m 20.40s , +08d 16m 48.5s) | C | 10 | 15.2 | 17355 | 2026-02-26 15:27:29 | MASTER-Tunka | (02h 46m 38.21s , +08d 11m 42.8s) | C | 10 | 15.8 | 17356 | 2026-02-26 15:27:29 | MASTER-Tunka | (02h 46m 20.53s , +08d 15m 06.2s) | C | 10 | 15.2 | 17379 | 2026-02-26 15:27:52 | MASTER-Tunka | (02h 46m 40.47s , +08d 13m 29.7s) | C | 10 | 15.8 | 17379 | 2026-02-26 15:27:52 | MASTER-Tunka | (02h 46m 22.85s , +08d 16m 53.5s) | C | 10 | 15.2 | 17404 | 2026-02-26 15:28:18 | MASTER-Tunka | (02h 46m 34.36s , +08d 12m 28.4s) | C | 10 | 15.8 | 17404 | 2026-02-26 15:28:18 | MASTER-Tunka | (02h 46m 16.62s , +08d 15m 50.9s) | C | 10 | 15.2 | 17428 | 2026-02-26 15:28:41 | MASTER-Tunka | (02h 46m 35.07s , +08d 13m 27.8s) | C | 10 | 15.7 | 17428 | 2026-02-26 15:28:42 | MASTER-Tunka | (02h 46m 17.38s , +08d 16m 50.8s) | C | 10 | 15.1 | 17457 | 2026-02-26 15:29:10 | MASTER-Tunka | (02h 46m 39.98s , +08d 12m 26.4s) | C | 10 | 15.7 | 17457 | 2026-02-26 15:29:10 | MASTER-Tunka | (02h 46m 22.36s , +08d 15m 50.5s) | C | 10 | 15.1 | 17480 | 2026-02-26 15:29:33 | MASTER-Tunka | (02h 46m 34.99s , +08d 11m 25.9s) | C | 10 | 15.7 | 17480 | 2026-02-26 15:29:33 | MASTER-Tunka | (02h 46m 17.41s , +08d 14m 49.8s) | C | 10 | 15.2 | 17507 | 2026-02-26 15:30:01 | MASTER-Tunka | (02h 46m 40.94s , +08d 11m 33.4s) | C | 10 | 15.7 | 17507 | 2026-02-26 15:30:01 | MASTER-Tunka | (02h 46m 23.14s , +08d 14m 53.9s) | C | 10 | 15.1 | 17531 | 2026-02-26 15:30:24 | MASTER-Tunka | (02h 46m 37.85s , +08d 13m 16.0s) | C | 10 | 15.7 | 17531 | 2026-02-26 15:30:24 | MASTER-Tunka | (02h 46m 20.32s , +08d 16m 41.5s) | C | 10 | 15.0 | 17553 | 2026-02-26 15:30:46 | MASTER-Tunka | (02h 46m 37.93s , +08d 11m 54.6s) | C | 10 | 15.7 | 17553 | 2026-02-26 15:30:46 | MASTER-Tunka | (02h 46m 20.09s , +08d 15m 13.6s) | C | 10 | 15.0 | 17576 | 2026-02-26 15:31:10 | MASTER-Tunka | (02h 46m 40.42s , +08d 12m 54.8s) | C | 10 | 15.6 | 17576 | 2026-02-26 15:31:10 | MASTER-Tunka | (02h 46m 22.84s , +08d 16m 17.8s) | C | 10 | 14.9 | 17600 | 2026-02-26 15:31:33 | MASTER-Tunka | (02h 46m 34.70s , +08d 12m 22.5s) | C | 10 | 15.6 | 17600 | 2026-02-26 15:31:33 | MASTER-Tunka | (02h 46m 16.99s , +08d 15m 44.7s) | C | 10 | 15.1 | 17626 | 2026-02-26 15:32:00 | MASTER-Tunka | (02h 46m 35.77s , +08d 13m 23.5s) | C | 10 | 15.6 | 17626 | 2026-02-26 15:32:00 | MASTER-Tunka | (02h 46m 18.12s , +08d 16m 47.2s) | C | 10 | 15.1 | 17650 | 2026-02-26 15:32:23 | MASTER-Tunka | (02h 46m 40.81s , +08d 12m 21.6s) | C | 10 | 15.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43848. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41962] LAT GRB260226.44: Global MASTER-Net observations report
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43848 SUBJECT: LAT GRB260226.44: Global MASTER-Net observations report DATE: 26/02/26 15:44:21 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the LAT GRB260226.44 (trigger No 793795080,02h 47m 41.04s , +07d 43m 12.0s, R=0.105833) errorbox 16332 sec after trigger time at 2026-02-26 15:10:31 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 81 deg. The sun altitude is -40.1 deg. The galactic latitude b = -45 deg., longitude l = 167 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3157390 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 16337 | 2026-02-26 15:10:31 | MASTER-Tunka | (02h 46m 41.03s , +08d 13m 10.9s) | C | 10 | 16.4 | 16347 | 2026-02-26 15:10:31 | MASTER-Tunka | (02h 46m 41.03s , +08d 13m 11.0s) | C | 30 | 17.0 | Coadd 16338 | 2026-02-26 15:10:31 | MASTER-Tunka | (02h 46m 22.49s , +08d 16m 39.4s) | C | 10 | 16.0 | 16362 | 2026-02-26 15:10:56 | MASTER-Tunka | (02h 46m 34.45s , +08d 12m 33.1s) | C | 10 | 16.5 | 16363 | 2026-02-26 15:10:56 | MASTER-Tunka | (02h 46m 16.08s , +08d 15m 59.0s) | C | 10 | 15.8 | 16384 | 2026-02-26 15:11:18 | MASTER-Tunka | (02h 46m 33.55s , +08d 13m 32.1s) | C | 10 | 16.4 | 16384 | 2026-02-26 15:11:18 | MASTER-Tunka | (02h 46m 15.50s , +08d 16m 58.7s) | C | 10 | 16.0 | 16408 | 2026-02-26 15:11:41 | MASTER-Tunka | (02h 46m 40.83s , +08d 12m 31.4s) | C | 10 | 16.4 | 16408 | 2026-02-26 15:11:41 | MASTER-Tunka | (02h 46m 22.76s , +08d 15m 57.8s) | C | 10 | 15.9 | 16430 | 2026-02-26 15:12:04 | MASTER-Tunka | (02h 46m 33.93s , +08d 11m 31.6s) | C | 10 | 16.3 | 16431 | 2026-02-26 15:12:04 | MASTER-Tunka | (02h 46m 15.91s , +08d 14m 57.9s) | C | 10 | 15.8 | 16454 | 2026-02-26 15:12:27 | MASTER-Tunka | (02h 46m 40.26s , +08d 11m 42.7s) | C | 10 | 16.1 | 16454 | 2026-02-26 15:12:27 | MASTER-Tunka | (02h 46m 22.16s , +08d 15m 07.0s) | C | 10 | 15.3 | 16478 | 2026-02-26 15:12:52 | MASTER-Tunka | (02h 46m 37.35s , +08d 12m 56.4s) | C | 10 | 15.0 | 16479 | 2026-02-26 15:12:52 | MASTER-Tunka | (02h 46m 19.39s , +08d 16m 23.6s) | C | 10 | 14.8 | 16503 | 2026-02-26 15:13:17 | MASTER-Tunka | (02h 46m 37.23s , +08d 11m 26.2s) | C | 10 | 14.7 | 16503 | 2026-02-26 15:13:17 | MASTER-Tunka | (02h 46m 19.51s , +08d 14m 56.8s) | C | 10 | 14.6 | 16526 | 2026-02-26 15:13:40 | MASTER-Tunka | (02h 46m 39.73s , +08d 13m 11.3s) | C | 10 | 15.8 | 16527 | 2026-02-26 15:13:40 | MASTER-Tunka | (02h 46m 21.80s , +08d 16m 35.6s) | C | 10 | 15.2 | 16550 | 2026-02-26 15:14:03 | MASTER-Tunka | (02h 46m 33.44s , +08d 12m 29.2s) | C | 10 | 15.3 | 16550 | 2026-02-26 15:14:03 | MASTER-Tunka | (02h 46m 15.66s , +08d 15m 55.3s) | C | 10 | 14.9 | 16576 | 2026-02-26 15:14:30 | MASTER-Tunka | (02h 46m 34.78s , +08d 13m 28.4s) | C | 10 | 15.3 | 16577 | 2026-02-26 15:14:30 | MASTER-Tunka | (02h 46m 17.03s , +08d 16m 54.9s) | C | 10 | 15.1 | 16607 | 2026-02-26 15:15:01 | MASTER-Tunka | (02h 46m 40.60s , +08d 12m 25.3s) | C | 10 | 15.4 | 16607 | 2026-02-26 15:15:01 | MASTER-Tunka | (02h 46m 22.93s , +08d 15m 51.3s) | C | 10 | 14.9 | 16630 | 2026-02-26 15:15:23 | MASTER-Tunka | (02h 46m 33.66s , +08d 11m 26.0s) | C | 10 | 15.4 | 16630 | 2026-02-26 15:15:23 | MASTER-Tunka | (02h 46m 16.01s , +08d 14m 52.2s) | C | 10 | 15.1 | 16653 | 2026-02-26 15:15:46 | MASTER-Tunka | (02h 46m 41.11s , +08d 11m 47.9s) | C | 10 | 16.1 | 16653 | 2026-02-26 15:15:46 | MASTER-Tunka | (02h 46m 24.19s , +08d 15m 25.7s) | C | 10 | 14.8 | 16676 | 2026-02-26 15:16:09 | MASTER-Tunka | (02h 46m 37.35s , +08d 13m 13.3s) | C | 10 | 15.6 | 16676 | 2026-02-26 15:16:09 | MASTER-Tunka | (02h 46m 19.66s , +08d 16m 38.3s) | C | 10 | 15.2 | 16832 | 2026-02-26 15:18:43 | MASTER-Tunka | (02h 46m 34.69s , +08d 13m 32.9s) | C | 15 | 16.1 | 16832 | 2026-02-26 15:18:43 | MASTER-Tunka | (02h 46m 16.54s , +08d 16m 52.9s) | C | 15 | 15.5 | 16859 | 2026-02-26 15:19:09 | MASTER-Tunka | (02h 46m 40.75s , +08d 12m 32.7s) | C | 15 | 16.0 | 16859 | 2026-02-26 15:19:09 | MASTER-Tunka | (02h 46m 22.88s , +08d 15m 54.8s) | C | 15 | 15.4 | 16884 | 2026-02-26 15:19:37 | MASTER-Tunka | (02h 46m 35.06s , +08d 11m 32.5s) | C | 10 | 15.8 | 16884 | 2026-02-26 15:19:38 | MASTER-Tunka | (02h 46m 17.19s , +08d 14m 52.2s) | C | 10 | 15.2 | 16908 | 2026-02-26 15:20:02 | MASTER-Tunka | (02h 46m 41.38s , +08d 11m 36.4s) | C | 10 | 16.1 | 16908 | 2026-02-26 15:20:02 | MASTER-Tunka | (02h 46m 23.62s , +08d 14m 57.3s) | C | 10 | 15.4 | 16947 | 2026-02-26 15:20:41 | MASTER-Tunka | (02h 46m 38.12s , +08d 13m 07.4s) | C | 10 | 16.1 | 16947 | 2026-02-26 15:20:41 | MASTER-Tunka | (02h 46m 20.25s , +08d 16m 28.2s) | C | 10 | 15.4 | 16969 | 2026-02-26 15:21:02 | MASTER-Tunka | (02h 46m 38.11s , +08d 11m 37.5s) | C | 10 | 16.0 | 16969 | 2026-02-26 15:21:03 | MASTER-Tunka | (02h 46m 19.74s , +08d 14m 48.1s) | C | 10 | 15.5 | 16993 | 2026-02-26 15:21:26 | MASTER-Tunka | (02h 46m 40.15s , +08d 13m 08.3s) | C | 10 | 15.8 | 16993 | 2026-02-26 15:21:26 | MASTER-Tunka | (02h 46m 22.32s , +08d 16m 29.7s) | C | 10 | 15.3 | 17017 | 2026-02-26 15:21:51 | MASTER-Tunka | (02h 46m 35.71s , +08d 12m 33.0s) | C | 10 | 16.1 | 17017 | 2026-02-26 15:21:51 | MASTER-Tunka | (02h 46m 17.88s , +08d 15m 54.5s) | C | 10 | 15.4 | 17042 | 2026-02-26 15:22:16 | MASTER-Tunka | (02h 46m 35.36s , +08d 13m 30.6s) | C | 10 | 15.9 | 17042 | 2026-02-26 15:22:16 | MASTER-Tunka | (02h 46m 17.46s , +08d 16m 51.1s) | C | 10 | 15.2 | 17068 | 2026-02-26 15:22:41 | MASTER-Tunka | (02h 46m 40.47s , +08d 12m 31.9s) | C | 10 | 15.9 | 17068 | 2026-02-26 15:22:41 | MASTER-Tunka | (02h 46m 22.01s , +08d 15m 41.5s) | C | 10 | 15.5 | 17092 | 2026-02-26 15:23:05 | MASTER-Tunka | (02h 46m 35.02s , +08d 11m 33.0s) | C | 10 | 15.7 | 17092 | 2026-02-26 15:23:05 | MASTER-Tunka | (02h 46m 17.26s , +08d 14m 55.9s) | C | 10 | 15.2 | 17114 | 2026-02-26 15:23:27 | MASTER-Tunka | (02h 46m 41.21s , +08d 11m 47.1s) | C | 10 | 15.8 | 17114 | 2026-02-26 15:23:27 | MASTER-Tunka | (02h 46m 23.36s , +08d 15m 07.6s) | C | 10 | 15.5 | 17139 | 2026-02-26 15:23:52 | MASTER-Tunka | (02h 46m 38.16s , +08d 13m 22.7s) | C | 10 | 15.8 | 17139 | 2026-02-26 15:23:52 | MASTER-Tunka | (02h 46m 19.90s , +08d 16m 35.1s) | C | 10 | 15.3 | 17163 | 2026-02-26 15:24:16 | MASTER-Tunka | (02h 46m 38.13s , +08d 11m 34.8s) | C | 10 | 15.8 | 17163 | 2026-02-26 15:24:16 | MASTER-Tunka | (02h 46m 20.56s , +08d 15m 02.0s) | C | 10 | 15.3 | 17187 | 2026-02-26 15:24:40 | MASTER-Tunka | (02h 46m 41.99s , +08d 13m 24.9s) | C | 10 | 16.0 | 17187 | 2026-02-26 15:24:40 | MASTER-Tunka | (02h 46m 24.35s , +08d 16m 51.1s) | C | 10 | 15.3 | 17209 | 2026-02-26 15:25:03 | MASTER-Tunka | (02h 46m 35.05s , +08d 12m 30.7s) | C | 10 | 15.9 | 17209 | 2026-02-26 15:25:03 | MASTER-Tunka | (02h 46m 17.41s , +08d 15m 58.0s) | C | 10 | 15.2 | 17231 | 2026-02-26 15:25:25 | MASTER-Tunka | (02h 46m 34.52s , +08d 13m 31.1s) | C | 10 | 15.8 | 17231 | 2026-02-26 15:25:25 | MASTER-Tunka | (02h 46m 16.43s , +08d 16m 48.8s) | C | 10 | 15.2 | 17258 | 2026-02-26 15:25:51 | MASTER-Tunka | (02h 46m 41.61s , +08d 12m 31.5s) | C | 10 | 15.8 | 17258 | 2026-02-26 15:25:51 | MASTER-Tunka | (02h 46m 24.00s , +08d 15m 56.3s) | C | 10 | 15.3 | 17281 | 2026-02-26 15:26:14 | MASTER-Tunka | (02h 46m 34.33s , +08d 11m 30.5s) | C | 10 | 15.8 | 17281 | 2026-02-26 15:26:14 | MASTER-Tunka | (02h 46m 16.53s , +08d 14m 52.9s) | C | 10 | 15.2 | 17305 | 2026-02-26 15:26:38 | MASTER-Tunka | (02h 46m 40.80s , +08d 11m 40.7s) | C | 10 | 16.0 | 17305 | 2026-02-26 15:26:38 | MASTER-Tunka | (02h 46m 22.93s , +08d 14m 59.1s) | C | 10 | 15.2 | 17330 | 2026-02-26 15:27:03 | MASTER-Tunka | (02h 46m 37.97s , +08d 13m 22.4s) | C | 10 | 15.7 | 17330 | 2026-02-26 15:27:03 | MASTER-Tunka | (02h 46m 20.40s , +08d 16m 48.5s) | C | 10 | 15.2 | 17355 | 2026-02-26 15:27:29 | MASTER-Tunka | (02h 46m 38.21s , +08d 11m 42.8s) | C | 10 | 15.8 | 17356 | 2026-02-26 15:27:29 | MASTER-Tunka | (02h 46m 20.53s , +08d 15m 06.2s) | C | 10 | 15.2 | 17379 | 2026-02-26 15:27:52 | MASTER-Tunka | (02h 46m 40.47s , +08d 13m 29.7s) | C | 10 | 15.8 | 17379 | 2026-02-26 15:27:52 | MASTER-Tunka | (02h 46m 22.85s , +08d 16m 53.5s) | C | 10 | 15.2 | 17404 | 2026-02-26 15:28:18 | MASTER-Tunka | (02h 46m 34.36s , +08d 12m 28.4s) | C | 10 | 15.8 | 17404 | 2026-02-26 15:28:18 | MASTER-Tunka | (02h 46m 16.62s , +08d 15m 50.9s) | C | 10 | 15.2 | 17428 | 2026-02-26 15:28:41 | MASTER-Tunka | (02h 46m 35.07s , +08d 13m 27.8s) | C | 10 | 15.7 | 17428 | 2026-02-26 15:28:42 | MASTER-Tunka | (02h 46m 17.38s , +08d 16m 50.8s) | C | 10 | 15.1 | 17457 | 2026-02-26 15:29:10 | MASTER-Tunka | (02h 46m 39.98s , +08d 12m 26.4s) | C | 10 | 15.7 | 17457 | 2026-02-26 15:29:10 | MASTER-Tunka | (02h 46m 22.36s , +08d 15m 50.5s) | C | 10 | 15.1 | 17480 | 2026-02-26 15:29:33 | MASTER-Tunka | (02h 46m 34.99s , +08d 11m 25.9s) | C | 10 | 15.7 | 17480 | 2026-02-26 15:29:33 | MASTER-Tunka | (02h 46m 17.41s , +08d 14m 49.8s) | C | 10 | 15.2 | 17507 | 2026-02-26 15:30:01 | MASTER-Tunka | (02h 46m 40.94s , +08d 11m 33.4s) | C | 10 | 15.7 | 17507 | 2026-02-26 15:30:01 | MASTER-Tunka | (02h 46m 23.14s , +08d 14m 53.9s) | C | 10 | 15.1 | 17531 | 2026-02-26 15:30:24 | MASTER-Tunka | (02h 46m 37.85s , +08d 13m 16.0s) | C | 10 | 15.7 | 17531 | 2026-02-26 15:30:24 | MASTER-Tunka | (02h 46m 20.32s , +08d 16m 41.5s) | C | 10 | 15.0 | 17553 | 2026-02-26 15:30:46 | MASTER-Tunka | (02h 46m 37.93s , +08d 11m 54.6s) | C | 10 | 15.7 | 17553 | 2026-02-26 15:30:46 | MASTER-Tunka | (02h 46m 20.09s , +08d 15m 13.6s) | C | 10 | 15.0 | 17576 | 2026-02-26 15:31:10 | MASTER-Tunka | (02h 46m 40.42s , +08d 12m 54.8s) | C | 10 | 15.6 | 17576 | 2026-02-26 15:31:10 | MASTER-Tunka | (02h 46m 22.84s , +08d 16m 17.8s) | C | 10 | 14.9 | 17600 | 2026-02-26 15:31:33 | MASTER-Tunka | (02h 46m 34.70s , +08d 12m 22.5s) | C | 10 | 15.6 | 17600 | 2026-02-26 15:31:33 | MASTER-Tunka | (02h 46m 16.99s , +08d 15m 44.7s) | C | 10 | 15.1 | 17626 | 2026-02-26 15:32:00 | MASTER-Tunka | (02h 46m 35.77s , +08d 13m 23.5s) | C | 10 | 15.6 | 17626 | 2026-02-26 15:32:00 | MASTER-Tunka | (02h 46m 18.12s , +08d 16m 47.2s) | C | 10 | 15.1 | 17650 | 2026-02-26 15:32:23 | MASTER-Tunka | (02h 46m 40.81s , +08d 12m 21.6s) | C | 10 | 15.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43848. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41961] Fermi GRB 260226A: Global MASTER-Net observations report
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43847 SUBJECT: Fermi GRB 260226A: Global MASTER-Net observations report DATE: 26/02/26 15:31:16 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 260226A ( Fermi GBM team, GCN 43840) errorbox 11103 sec after notice time and 11134 sec after trigger time at 2026-02-26 13:43:30 UT, with upper limit up to 19.1 mag. The observations began at zenith distance = 59 deg. The sun altitude is -28.9 deg. The galactic latitude b = -36 deg., longitude l = 164 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3156987 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 11139 | 2026-02-26 13:43:30 | MASTER-Tunka | (02h 58m 57.34s , +16d 00m 41.9s) | C | 10 | 18.0 | 11139 | 2026-02-26 13:43:30 | MASTER-Tunka | (02h 59m 23.46s , +15d 56m 15.9s) | C | 10 | 17.9 | 11149 | 2026-02-26 13:43:30 | MASTER-Tunka | (02h 59m 23.46s , +15d 56m 15.9s) | C | 30 | 18.8 | Coadd 11163 | 2026-02-26 13:43:54 | MASTER-Tunka | (02h 58m 52.12s , +15d 59m 40.3s) | C | 10 | 18.0 | 11163 | 2026-02-26 13:43:54 | MASTER-Tunka | (02h 59m 18.19s , +15d 55m 14.9s) | C | 10 | 17.9 | 11187 | 2026-02-26 13:44:17 | MASTER-Tunka | (02h 59m 23.99s , +15d 55m 25.8s) | C | 10 | 17.9 | 11187 | 2026-02-26 13:44:17 | MASTER-Tunka | (02h 58m 57.93s , +15d 59m 51.0s) | C | 10 | 18.1 | 11212 | 2026-02-26 13:44:42 | MASTER-Tunka | (02h 58m 54.73s , +16d 01m 23.4s) | C | 10 | 18.0 | 11212 | 2026-02-26 13:44:42 | MASTER-Tunka | (02h 59m 20.78s , +15d 56m 58.6s) | C | 10 | 17.9 | 11222 | 2026-02-26 13:44:42 | MASTER-Tunka | (02h 59m 20.78s , +15d 56m 58.6s) | C | 30 | 18.7 | Coadd 11236 | 2026-02-26 13:45:07 | MASTER-Tunka | (02h 58m 54.78s , +15d 59m 58.2s) | C | 10 | 17.9 | 11236 | 2026-02-26 13:45:07 | MASTER-Tunka | (02h 59m 20.82s , +15d 55m 33.4s) | C | 10 | 18.0 | 11261 | 2026-02-26 13:45:31 | MASTER-Tunka | (02h 58m 57.44s , +16d 01m 12.6s) | C | 10 | 18.0 | 11261 | 2026-02-26 13:45:31 | MASTER-Tunka | (02h 59m 23.48s , +15d 56m 47.9s) | C | 10 | 17.9 | 11284 | 2026-02-26 13:45:55 | MASTER-Tunka | (02h 58m 52.43s , +16d 00m 36.6s) | C | 10 | 17.9 | 11284 | 2026-02-26 13:45:55 | MASTER-Tunka | (02h 59m 18.47s , +15d 56m 12.1s) | C | 10 | 18.0 | 11294 | 2026-02-26 13:45:55 | MASTER-Tunka | (02h 59m 18.47s , +15d 56m 12.1s) | C | 30 | 18.8 | Coadd 11307 | 2026-02-26 13:46:17 | MASTER-Tunka | (02h 58m 51.55s , +16d 01m 36.1s) | C | 10 | 18.0 | 11307 | 2026-02-26 13:46:17 | MASTER-Tunka | (02h 59m 17.60s , +15d 57m 11.6s) | C | 10 | 17.9 | 11329 | 2026-02-26 13:46:40 | MASTER-Tunka | (02h 58m 58.52s , +16d 00m 35.7s) | C | 10 | 17.9 | 11329 | 2026-02-26 13:46:40 | MASTER-Tunka | (02h 59m 24.56s , +15d 56m 11.1s) | C | 10 | 17.9 | 11352 | 2026-02-26 13:47:03 | MASTER-Tunka | (02h 59m 18.76s , +15d 55m 10.5s) | C | 10 | 17.9 | 11362 | 2026-02-26 13:47:03 | MASTER-Tunka | (02h 59m 18.77s , +15d 55m 10.4s) | C | 30 | 18.7 | Coadd 11353 | 2026-02-26 13:47:03 | MASTER-Tunka | (02h 58m 52.73s , +15d 59m 34.6s) | C | 10 | 18.0 | 11374 | 2026-02-26 13:47:25 | MASTER-Tunka | (02h 58m 57.05s , +15d 59m 57.9s) | C | 10 | 17.9 | 11374 | 2026-02-26 13:47:25 | MASTER-Tunka | (02h 59m 23.10s , +15d 55m 33.8s) | C | 10 | 17.9 | 11400 | 2026-02-26 13:47:50 | MASTER-Tunka | (02h 58m 55.01s , +16d 01m 17.3s) | C | 10 | 17.9 | 11400 | 2026-02-26 13:47:50 | MASTER-Tunka | (02h 59m 21.06s , +15d 56m 53.3s) | C | 10 | 17.9 | 11426 | 2026-02-26 13:48:13 | MASTER-Tunka | (02h 58m 55.07s , +15d 59m 57.3s) | C | 15 | 18.2 | 11426 | 2026-02-26 13:48:13 | MASTER-Tunka | (02h 59m 21.10s , +15d 55m 33.2s) | C | 15 | 18.2 | 11441 | 2026-02-26 13:48:13 | MASTER-Tunka | (02h 59m 21.10s , +15d 55m 33.2s) | C | 45 | 19.0 | Coadd 11453 | 2026-02-26 13:48:41 | MASTER-Tunka | (02h 58m 58.09s , +16d 01m 14.6s) | C | 15 | 18.1 | 11453 | 2026-02-26 13:48:41 | MASTER-Tunka | (02h 59m 24.14s , +15d 56m 50.8s) | C | 15 | 18.1 | 11481 | 2026-02-26 13:49:08 | MASTER-Tunka | (02h 58m 51.32s , +16d 00m 32.0s) | C | 15 | 18.1 | 11481 | 2026-02-26 13:49:08 | MASTER-Tunka | (02h 59m 17.36s , +15d 56m 08.1s) | C | 15 | 18.1 | 11514 | 2026-02-26 13:49:41 | MASTER-Tunka | (02h 58m 51.83s , +16d 01m 31.0s) | C | 15 | 18.1 | 11514 | 2026-02-26 13:49:42 | MASTER-Tunka | (02h 59m 17.88s , +15d 57m 07.4s) | C | 15 | 18.1 | 11529 | 2026-02-26 13:49:42 | MASTER-Tunka | (02h 59m 17.88s , +15d 57m 07.5s) | C | 45 | 18.9 | Coadd 11542 | 2026-02-26 13:50:09 | MASTER-Tunka | (02h 58m 57.84s , +16d 00m 30.9s) | C | 15 | 18.2 | 11542 | 2026-02-26 13:50:09 | MASTER-Tunka | (02h 59m 23.88s , +15d 56m 07.4s) | C | 15 | 18.1 | 11574 | 2026-02-26 13:50:41 | MASTER-Tunka | (02h 58m 51.31s , +15d 59m 30.1s) | C | 15 | 18.2 | 11574 | 2026-02-26 13:50:41 | MASTER-Tunka | (02h 59m 17.33s , +15d 55m 06.6s) | C | 15 | 18.2 | 11604 | 2026-02-26 13:51:11 | MASTER-Tunka | (02h 58m 58.44s , +15d 59m 43.7s) | C | 15 | 18.1 | 11604 | 2026-02-26 13:51:11 | MASTER-Tunka | (02h 59m 24.49s , +15d 55m 20.3s) | C | 15 | 18.1 | 11619 | 2026-02-26 13:51:11 | MASTER-Tunka | (02h 59m 24.49s , +15d 55m 20.2s) | C | 45 | 19.0 | Coadd 11633 | 2026-02-26 13:51:40 | MASTER-Tunka | (02h 58m 55.34s , +16d 01m 27.4s) | C | 15 | 18.1 | 11633 | 2026-02-26 13:51:40 | MASTER-Tunka | (02h 59m 21.38s , +15d 57m 04.2s) | C | 15 | 18.1 | 11662 | 2026-02-26 13:52:09 | MASTER-Tunka | (02h 58m 55.45s , +15d 59m 35.4s) | C | 15 | 18.2 | 11662 | 2026-02-26 13:52:09 | MASTER-Tunka | (02h 59m 21.45s , +15d 55m 12.6s) | C | 15 | 18.1 | 11691 | 2026-02-26 13:52:38 | MASTER-Tunka | (02h 58m 57.68s , +16d 00m 59.7s) | C | 15 | 18.2 | 11691 | 2026-02-26 13:52:38 | MASTER-Tunka | (02h 59m 23.70s , +15d 56m 36.7s) | C | 15 | 18.1 | 11706 | 2026-02-26 13:52:38 | MASTER-Tunka | (02h 59m 23.70s , +15d 56m 36.7s) | C | 45 | 19.1 | Coadd 11721 | 2026-02-26 13:53:08 | MASTER-Tunka | (02h 58m 52.55s , +16d 00m 26.7s) | C | 15 | 18.2 | 11721 | 2026-02-26 13:53:08 | MASTER-Tunka | (02h 59m 18.55s , +15d 56m 04.1s) | C | 15 | 18.1 | 11751 | 2026-02-26 13:53:38 | MASTER-Tunka | (02h 58m 53.33s , +16d 01m 26.5s) | C | 15 | 18.1 | 11751 | 2026-02-26 13:53:38 | MASTER-Tunka | (02h 59m 19.32s , +15d 57m 03.9s) | C | 15 | 18.1 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43847. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41960] GRB 260226A: AstroSat CZTI detection of bright long burst
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43846 SUBJECT: GRB 260226A: AstroSat CZTI detection of bright long burst DATE: 26/02/26 15:00:12 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> Harsha K. H. (IUCAA), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), U. Pathak (IITB), A. Arya (IITB), A. Goyal (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long, bright GRB 260226A which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 43840), Fermi LAT (Depalo et. al. , GCN Circ. 43844) and Calet (via Trigger Notices, Trig Num. 1456137494). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. Due to the extremely bright nature of the GRB, all four quadrants of CZT detectors were saturated. The strongest non-saturated peak of the lightcurve occurs at 2026-02-26 10:38:22.65 UTC. This affects the total counts and peak counts reported. The measured peak count rate associated with the burst is 2464 (+267, -180) counts/s above the background in the combined data of three quadrants (out of four), with a total of 6666 (+247, -284) counts. We caution that these numbers are impacted by the data loss from saturation. The local mean background count rate was 258 (+1, -5) counts/s. Using cumulative rates, we measure a T90 of 21 (+1, -1) s. In the preliminary analysis, we find 4947 Compton events associated with this event. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-02-26 10:38:15.33 UTC. The veto detector does not show any signs of saturation. The measured peak count rate associated with the burst is 16447 (+216, -227) counts/s above the background in the combined data of all quadrants, with a total of 139460 (+832, -794) counts. The local mean background count rate was 1425 (+4, -6) counts/s. We measure a T90 of 19 (+1, -1) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/43846. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41959] EP260214a: VLA 6 GHz detection
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43845 SUBJECT: EP260214a: VLA 6 GHz detection DATE: 26/02/26 14:15:11 GMT FROM: Roberto Ricci at INAF-IRA <ricci(a)ira.inaf.it> R. Ricci, M. Yadav, Y.-H. Yang, N. Passaleva and E. Troja (U Rome) report: We observed the Einstein Probe event EP260214a detected by EP/WXT (A. Li et al. GCN 43742) with Very Large Array in C-band at the centre frequency of 6 GHz with a bandwidth of 4 GHz on Feb 21st 2026, 6.6 days after the trigger. Within the EP/FXT error circle (A. Li et al., GCN 43751) we detect a possible radio counterpart at RA, Dec (J2000) = 13:24:55.401, -29:02:32.97 with a flux density of about 60 uJy. No source is visible at this position in our deep VLT/HAWKI image (N. Passaleva et al. GCN 43756). However, we note that the candidate counterpart lies 8.8” away from a bright galaxy (r=19.62 AB mag), corresponding to a chance alignment of Pcc~4% (Bloom et al. 2002). Assuming a photometric redshift of z=0.18±0.15 (PRLS, Zhou et al. 2021), this corresponds to a projected physical offset of 27 (+15, -22) kpc. Further observations to assess the variability of the candidate radio counterpart are planned. We thank the VLA staff for executing the observations View this GCN Circular online at https://gcn.nasa.gov/circulars/43845. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41958] GRB 260226A: Fermi-LAT detection of a bright burst
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43844 SUBJECT: GRB 260226A: Fermi-LAT detection of a bright burst DATE: 26/02/26 13:34:45 GMT FROM: Davide Depalo at Politecnico and INFN Bari <davide.depalo(a)ba.infn.it> D. Depalo (Politecnico and INFN Bari), E. Bissaldi (Politecnico and INFN Bari), S. Zhu (DESY), R. Gupta (NASA/GSFC), J. L. Racusin (NASA/GSFC), F. Longo (Univ and INFN Trieste) report on behalf of the Fermi-LAT Collaboration: At 10:38:18.84 UT on Feb 26, 2026, Fermi-LAT triggered on high-energy emission from GRB 260226A, also detected by GBM (trigger 793795080.95811 / 260226443, GCN Circular 43840) at 10:37:55 UT. Note that this is a rare onboard detection seeded by LAT, independent of the GBM trigger, which is why the trigger times differ. LAT-seeded alerts have a very high threshold and this is only the second GRB to have passed this alert after GRB 090510. The onboard location is RA, Dec 42.050, +8.033 with an approximate error radius of 0.5 deg (90% containment, systematic error only). This was 17 deg from the LAT boresight at the time of the trigger. We anticipate providing a refined location within the next 12 hours when the LAT science data for this burst are downlinked and processed. The Fermi-LAT point of contact for this burst is Niccolò Di Lalla (niccolo.dilalla(a)stanford.edu) The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/43844. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41957] GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43843 SUBJECT: GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443) DATE: 26/02/26 13:23:46 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 793795080 at 10:37:55 on 26 Feb. 2026 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 43.6 deg Decl.(2000.0) = 9.6 deg The 1 sigma statistical error radius is 0.2 deg. We estimate an additional systematic error of 2 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260226443/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260226443/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260226443/json View this GCN Circular online at https://gcn.nasa.gov/circulars/43843. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41956] EP260224a: LCO optical upper limits
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43842 SUBJECT: EP260224a: LCO optical upper limits DATE: 26/02/26 12:00:50 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris (Leicester), A. van Hoof (Radboud), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), and A. J. Levan (Radboud) report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP260224a (Yang et al., GCN 43828) using LCO 1m telescopes located at the Cerro Tololo Inter-American Observatory (Chile) and the South African Astronomical Observatory (South Africa) equipped with the SINISTRO instrument. A series of 6x300 s exposures were taken in each of the SDSS-r and SDSS-z filters, starting at 2026-02-26 03:25:00 UT (32.4 hr after the trigger) and 2026-02-25 23:23:55 UT (30.3 hr after the trigger) respectively. We performed subtractions on our stacked images using a template image from the KMTNet Synoptic Survey of the Southern Sky (Kim et al. 2016, doi:10.5303/JKAS.2016.49.1.37) and compared the stacks and template manually. No new source is detected within or at the border of the EP/WXT uncertainty region (Yang et al., GCN 43828). From the stacked images, we obtain the following 3-sigma upper limits:  r > 23.6 z > 21.6 These upper limits are in AB magnitudes, calibrated using nearby stars from the SkyMapper catalog, and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43842. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41955] GRB260225A: SVOM/ECLAIRs refined position
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43841 SUBJECT: GRB260225A: SVOM/ECLAIRs refined position DATE: 26/02/26 11:19:51 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet, O. Godet (IRAP), on behalf of the ECLAIRs team report: Using the event-by-event data downloaded through the X-band ground station, we were able to improve the ECLAIRs position of GRB 260204A (SVOM burst-id sb26022501, Ma et al., GCN 43829) as: R.A., Dec.: 204.7191, 44.6194 degrees: R.A. (J2000) = 13h38m52.58s Dec. (J2000) = 44d37m09.84s with a 90% confidence level (C.L.) radius of 7.1 arcmin. Within this refined position, a counterpart has been detected in optical by SVOM/COLIBRÍ (Ducoin et al., GCN 43837) and SVOM/VT (Li et al., GCN 43838) as well as in X-rays by EP/FXT (Yang et al., GCN 43839). The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. MXT was developed jointly by CEA, CNES, University of Leicester, IJCLab and MPE. ECLAIRs was developed jointly by CNES, IRAP, APC and CEA. The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/43841. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41954] GRB 260226A: Fermi GBM Final Real-time Localization
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43840 SUBJECT: GRB 260226A: Fermi GBM Final Real-time Localization DATE: 26/02/26 10:48:46 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 10:37:55 UT on 26 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260226A (trigger 793795080.95811 / 260226443). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 45.3, Dec = 15.7 (J2000 degrees, equivalent to J2000 03h 01m, 15d 41'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 17.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260226443/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260226443/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260226443/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43840. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41953] GRB 260225A: EP-FXT follow-up observation
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43839 SUBJECT: GRB 260225A: EP-FXT follow-up observation DATE: 26/02/26 04:07:27 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Guojiong Yang(NAO, CAS), Jiaying Cao(IHEP), Wenfeng Wen(SZTU) and Haiwu Pan (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 260225A (SVOM/sb26022501; Ma et al., GCN 43829) starting at 2026-02-25T09:26:28 UTC, approximately 35 minutes after the SVOM trigger, with a total exposure time of 6090 s. At the optical position reported by Basa et al. (GCN Circ. 43837), an uncatalogued X-ray source (EPF_J133924.5+443450; RA, Dec = 204.852, 44.5806, J2000) is detected, with a 90% confidence positional uncertainty of 2.1 arcsec (statistical only). The spectrum can be well fitted with an absorbed power-law model, with the Galactic hydrogen column density. The best-fit photon index is about 1.56. The corresponding unabsorbed flux in the 0.5–10 keV band is 1.89×10^-12 erg cm^-2 s^-1 Flux_err: 2.3 × 10^-13 erg cm^-2 s^-1 (1σ) Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43839. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41952] GRB 260225A: SVOM/VT optical observation
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43838 SUBJECT: GRB 260225A: SVOM/VT optical observation DATE: 26/02/26 03:29:53 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), D. Turpin (CEA) and L. Zhang (IHEP) report on behalf of the SVOM/VT team. Following the report of the optical counterpart (Ducoin et al., GCN 43837) by SVOM/COLIBRÍ (Basa et al., GCN 43830), we reanalyzed SVOM/VT Xband data (Li et al., GCN 43834) for GRB 260225A (Ma et al., GCN 43829). The source was detected by SVOM/VT in both channels. The measurements in AB magnitude are derived as follows: Mid time | Band | Exposure Time | Magnitude 1.13 hours VT_B 52*50 sec 22.09 +/- 0.16 mag 1.07 hours VT_R 41*50 sec 22.00 +/- 0.20 mag Our photometry was not corrected for Galactic extinction. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/43838. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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