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[vsnet-grb-info 41891] Fermi-LAT Gamma-ray Observations of IceCube-260217A
by GCN Circulars 18 Feb '26

18 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43781 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-260217A DATE: 26/02/18 21:17:41 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC260217A neutrino event (GCN 43768) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 26-02-17 at 05:55:24.52 UTC (T0) with J2000 position RA = 75.89 (+0.52, -0.56) deg, Decl. = 14.63 (+0.45, -0.43 ) deg 90% PSF containment (J2000). No cataloged gamma-ray sources are found within the 90% IC260217A localization error (4FGL-DR4; The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC260217A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC260217A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 2.0e-10 ph cm^-2 s^-1 for ~17-years (2008-08-04 / T0), <5.5e-09 (<1.7e-07) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this analysis, the Fermi-LAT contact person is L. Pfeiffer (leonard.pfeiffer at uni-wuerzburg.de). 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/43781. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41890] GRB 260217A: Fermi GBM Final Localization
by GCN Circulars 18 Feb '26

18 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43780 SUBJECT: GRB 260217A: Fermi GBM Final Localization DATE: 26/02/18 11:43:01 GMT FROM: Cuán de Barra at UCD <cuan.debarra(a)ucdconnect.ie> The Fermi GBM team reports the detection of a likely LONG GRB At 09:18:12.01 UT on 17 February 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260217A (trigger 793012697/260217388). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 278.43, Dec = -5.30 (J2000 degrees, equivalent to J2000 18h 34m, -5d 18'), with a statistical uncertainty of 11.59 degrees. The angle from the Fermi LAT boresight is 91 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260217388/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260217388/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260217388/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43780. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41889] GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
by GCN Circulars 18 Feb '26

18 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43779 SUBJECT: GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search DATE: 26/02/18 09:25:40 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> H. Yang, M. Brunet, O. Godet, J.-L. Atteia (IRAP) report on behalf of the SVOM team: The SVOM/ECLAIRs telescope detected GRB 260214B/EP260214b (EP team, GCN 43744), starting at 2026-02-14T22:03:41.16 UTC (T0), through an offline targeted search with the event-by-event data downloaded through the X-band ground station. The burst was detected within several timescales and energy ranges. The best detection is obtained by the image trigger with a signal-to-noise ratio (SNR) of 7.06 within 4-90 keV over a time window of 6 seconds starting at T0. This event was not detected onboard because it was too faint. The localization of the source is RA, Dec = 191.147, 23.990 degrees: RA (J2000) = 12h44m35s Dec (J2000) = 23d59m24s with a 90% C.L. radius of 12.5 arcmin (including systematic error of 6 arcmin added in quadrature). This position is consistent with that measured by EP/WXT, with an angular separation of 10 arcmin. The time-averaged spectrum from T0 to T0+6 s in the energy range 4-90 keV is best fitted by a broken powerlaw, with a break energy of 8.2+/-0.9 keV, a second photon index of 1.9+0.4/-0.3, while the first photon index is not well constrained. If the first photon index is fixed to 0.7, as measured by EP/WXT, the fit yields a break energy of 10+3/-2 keV and a second photon index of 1.7+0.4/-0.3. With this model, the total energy flux in the 4-120 keV is (2.6+/-0.8)e-8 erg/cm^2/s. Assuming a redshift of z=1.208 (E. Le Floch et al., GCN 43749) and a standard cosmology with H_0 = 67.3 km/s/Mpc and Omega_M = 0.315 (Planck Collaboration, 2014), we estimate the following rest-frame parameters: the isotropic energy release E_iso is (2.7+/-0.8)e51 erg, and the rest-frame peak energy of the time-averaged spectrum Ep,z is 22+7/-4 keV. With these estimates, GRB 260214B/EP260214b is consistent with the distribution of Type II (long) GRBs on the Amati relation reported by Willingale et al. 2017, although it lies toward the lower end of the Ep,z and E_iso ranges. All quoted errors are at the 68% confidence level. 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. ECLAIRs was developed jointly by APC, CEA, CNES, and IRAP. The SVOM/ECLAIRs point of contact for this event is : Hui Yang (hui.yang(a)irap.omp.eu) Please contact him by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/43779. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41888] sb26021801: SVOM detection of a long faint X-ray transient
by GCN Circulars 18 Feb '26

18 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43778 SUBJECT: sb26021801: SVOM detection of a long faint X-ray transient DATE: 26/02/18 07:15:55 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Wenjin TAN (IHEP), Chao WU (NAOC), Wenjin XIE (NAOC), Hatsune GOTO (Kanazawa Univ.), Pierre MAGGI (ObAS) , report on behalf of the SVOM mission team: At 2026-02-18T05:15:18 UTC (T0), SVOM/ECLAIRs triggered and located an X-ray transient (SVOM burst-id sb26021801). 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 1 alert. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 8.29 in the 5-20 keV energy band over a time window of 1310.72 seconds starting at 2026-02-18T04:53:28. The localization of the best alert is R.A., Dec. 194.8408, 27.9434 degrees: R.A. (J2000) = 12h59m21.80s Dec. (J2000) = 27d56m36.21s with a 90% confidence level (C.L.) radius of 9.50 arcmin (including systematic error of 2 arcmin added in quadrature). The Coma Cluster (ACO 1656) and its Brightest Central Galaxy NGC 4874 are within the trigger error circle and may be the source triggering the ECLAIRs telescope. Due to the detection significance being below the slew threshold, no immediate slew was performed on this burst. 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. 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 Wenjun Tan: tanwj(a)ihep.ac.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/43778. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41887] The EP-WXT trigger 01709258455 is likely a flaring star
by GCN Circulars 18 Feb '26

18 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43777 SUBJECT: The EP-WXT trigger 01709258455 is likely a flaring star DATE: 26/02/18 02:52:19 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> X. X. Sun (NAO, CAS), Y. L. Wang (NAO, CAS; ICE, CSIC-IEEC), Y.Q. Zhao(USTC,PRIC), and H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709258455 at the time of 2026-02-17T21:46:05, is likely a stellar flare associated with RX J0920.0+3052. 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 5.2e30 erg/s. 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/43777. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41886] EP-WXT 01709258455: NOT optical upper limits
by GCN Circulars 18 Feb '26

18 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43776 SUBJECT: EP-WXT 01709258455: NOT optical upper limits DATE: 26/02/18 00:20:32 GMT FROM: javisansie(a)gmail.com J. Quirola-Vasquez (Radboud), G. Corcoran (UCD), J. Sanchez-Sierras (Radboud), A. Martin-Carrillo (UCD) and P. G. Jonker (Radboud) report on behalf of a larger collaboration: We observed the field of the Einstein Probe trigger WXT 01709258455, using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were triggered using the recently implemented automatic “rapid response mode” (RRM) and were obtained in the SDSS r (5x180 s) and z (9x150 s) bands, starting on 2026-02-17 at 21:56:02 UT (9.94 min after the WXT trigger). We carried out subtraction in both bands using Pan-STARRS archival images as templates. The subtractions were performed using the ZOGY algorithm (Zackay et al. 2016), as implemented in PyZOGY (Guevel et al. 2021). We do not find any new, uncatalogued sources within the EP-WXT uncertainty region. From the stacked images we obtain the following 3-sigma upper limits: r > 23.8 z > 22.0 These limits are in the AB system, were calibrated using nearby stars from the Pan-STARRS catalog and are not corrected for Galactic extinction. We note the presence of an M-class dwarf with ROSAT X-ray emission within the error region. We cannot discard whether this trigger can be attributed to a stellar flare, because we cannot measure its brightness due to the source being saturated in our images. View this GCN Circular online at https://gcn.nasa.gov/circulars/43776. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41885] EP260214b: Mondy optical observations
by GCN Circulars 17 Feb '26

17 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43775 SUBJECT: EP260214b: Mondy optical observations DATE: 26/02/17 17:29:43 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 EP260214b (Yang et al., GCNs 43744, 43760) with the AZT-33IK 1.5m telescope of the Mondy observatory starting on 2026-02-16 (UT) 19:44:56 and taking several 120-seconds frames in the R band. The optical counterpart (He et al., GCN 43745; Watson et al., GCN 43747; Pérez-Fournon et al., GCN 43750; Russeil et al., GCN 43752; Li et al., GCN 43755; Vijaykumar et al., GCN 43757; Becerra et al., GCN 43758; Aryan et al., GCN 43762; Bochenek & Perley, GCN 43764; Kar et al., GCN 43774) at a redshift z = 1.208 (Le Floch et al., GCN 43749) is detected in the stacked frame. Preliminary photometry and observational details are the following: Date UT start t-T0 Exp. Filter Obj. Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2026-02-16 19:44:56 1.93455 45*120 R 21.67 0.16 23.0 Mondy/AZT-33IK The photometry is based on nearby SDSS stars (R-magnitudes obtained using the 2005 Lupton transformation equations) and is not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43775. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41884] EP260214b: 1.3m DFOT optical upper limit
by GCN Circulars 17 Feb '26

17 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43774 SUBJECT: EP260214b: 1.3m DFOT optical upper limit DATE: 26/02/17 17:26:03 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 EP260214b detected by EP/WXT (Yang et al., GCN 43744) 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 2026-02-17 at 00:15:22 UT, approximately 50.82 hours after the trigger. We obtained multiple exposures of 300 s each in the R filter. A total of 15 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 EP/WXT (Yang et al., GCN 43760) as reported by He et al. (GCN 43745). This is consistent with the non-detection reported by Aryan et al. (GCN 43762). We derive the following 3-sigma upper limit from the stacked image: Date (UT) Start Time T_start–T0 (hr) Filter Exposure Magnitude ---------------------------------------------------------------------------------- 2026-02-17 00:15:22 ~50.82 R 300 s × 15 > 22.40 The non-detection is consistent with the detection and fading behavior reported by Watson et al. (GCN 43747), Floch et al. (GCN 43749), Pérez-Fournon et al. (GCN 43750), Russeil et al. (GCN 43752), Li et al. (GCN 43755), Becerra et al. (GCN 43758), as well as with the upper limit reported by Vijaykumar et al. (GCN 43757). The reported magnitude is not corrected for Galactic extinction. Photometric calibration was performed using standard stars from the Pan-Starrs catalogue. View this GCN Circular online at https://gcn.nasa.gov/circulars/43774. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41883] EP260210a: Mondy optical upper limits
by GCN Circulars 17 Feb '26

17 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43773 SUBJECT: EP260210a: Mondy optical upper limits DATE: 26/02/17 15:04:00 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), E. Klunko (ISTP), N. Pankov (IKI), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We observed the field of the fast X-ray transient EP260210a (Shi et al. GCN 43681) with the AZT-33IK 1.5m telescope of the Mondy observatory on Feb. 10 and 14 taking several 120-seconds frames in the R band. In the refined EP-FXT error circle (Yang et al., GCN 43696) we do not detect any new optical source in the stacked frames of our data. All catalogued sources located inside the refined EP-FXT error circle are detected in our stacked frames and do not exhibit any significant variations between the two epochs. In particular, the only one galaxy is presented within the refined EP-FXT error circle at coordinates of (J2000) 11:19:19.81 +45:23:43.8 in the SDSS catalogue. Preliminary photometry of the galaxy and observational details are the following: Date UT start t-T0 Exp. Filter SDSS_galaxy UL Site/Telescope (mid,days) (n*s) (3sigma) 2026-02-10 15:18:13 0.22584 30*120 R 20.29+/-0.05 22.7 Mondy/AZT-33IK 2026-02-14 20:08:59 4.42816 30*120 R 20.31+/-0.06 22.4 Mondy/AZT-33IK The photometry is based on nearby SDSS stars (R-magnitudes obtained using the 2005 Lupton transformation equations) and is not corrected for Galactic extinction. Our results are consistent with other published observations (Kang et al., GCN 43683; Fortin et al., GCN 43684; Li et al., GCN 43687; Aryan et al., GCN 43692; Lipunov et al., GCN 43697). View this GCN Circular online at https://gcn.nasa.gov/circulars/43773. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41882] Konus-Wind detection of GRB 260212A
by GCN Circulars 17 Feb '26

17 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43772 SUBJECT: Konus-Wind detection of GRB 260212A DATE: 26/02/17 14:55:21 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 260212A (Fermi-GBM detection: The Fermi GBM team, GCN 43716; Neights and Meegan GCN 43740; Glowbug detection: Cheung et al., GCN 43719; SVOM-GRM detection: Zhang et al., GCN 43727; GECAM-B detection: Zhang et al., GCN 43736; AstroSat-CZTI detection: Salunke et al., GCN 43741; IPN triangulation: Kozyrev et al., GCN 43769) triggered Konus-Wind (KW) at T0=64149.637 s UT (17:49:09.637). The burst light curve shows multiple emission pulses in the interval from ~T0-0.5 s to ~T0+11 s. The emission is seen up to ~2 MeV. We also note a much weaker emission bump around T0+25 s, which is visible only below 80 keV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260212_T64149/ As observed by Konus-Wind, the burst had the fluence of (6.81 ± 0.55)x10^-6 erg/cm^2 and the 64-ms peak energy flux, measured from T0 + 0.640 s, of (4.98 ± 0.40)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst (measured from T0 to T0+16.640 s) is best fitted in the 20 keV - 15 MeV range by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.16 (-0.10, + 0.10) and Ep = 115(-7,+9) keV, chi^2 = 97/93 dof. Fitting this spectrum by a Band GRB function yields the same values of alpha and Ep, and only an upper limit on the high energy photon index beta of -2.7 The spectrum near the peak count rate (measured from T0 to T0+8.448 s) is best fitted in the 20 keV - 15 MeV range by a CPL model with alpha = -0.86 (-0.11, + 0.12)and Ep = 108(-8,+10) keV, chi^2 = 94/78 dof. Fitting this spectrum by a Band function yields the same values of alpha and Ep, and only an upper limit on the high energy photon index beta of -3.2 All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary View this GCN Circular online at https://gcn.nasa.gov/circulars/43772. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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