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[vsnet-grb-info 41881] GRB 260208A: AbAO and Terskol optical upper limits
by GCN Circulars 17 Feb '26

17 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43771 SUBJECT: GRB 260208A: AbAO and Terskol optical upper limits DATE: 26/02/17 14:19:08 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), R. Ya. Inasaridze (AbAO), I. Sokolov (INASAN, KIAM), A. Pozanenko (IKI), N. Pankov (IKI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 260208A (Fermi GBM team, GCN 43635; Sonawane et al. 2026, GCN 43642; Longo et al. 2026, GCN 43645; Dichiara et al. 2026, GCN 43652; Luo et al. 2026, GCN 43658; Mukherjee & Meegan, GCN 43673; Waratkar & Grefenstette, GCN 43674; Cheung et al., GCN 43675) at z = 2.36 (Dimple et al., GCN 43662) with the 0.7-meter AS-32 telescope of Abastumani Observatory (AbAO) and with the 2-meter Zeiss-2000 telescope of the Terskol observatory on Feb. 10 taking several R-filter exposures. We do not detect the optical counterpart (Lipunov et al., GCN 43640; Wortley et al., GCN 43641; Dichiara et al., GCN 43652; Ma et al., GCN 43655; Ahumada et al., GCN 43657; Dimple et al., GCN 43661; Magnani et al., GCN 43664; Gupta et al., GCN 43665; Volnova et al., GCN 43666, 43770; Pérez-Fournon et al., GCN 43694; Kuin & Cenko, GCN 43702) in the stacked frames of both telescopes. 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) 2026-02-10 21:58:14 2.77172 65*120 R n/d n/d 20.4 AbAO/AS-32 2026-02-10 23:52:31 2.81612 21*150 R n/d n/d 21.2 Terskol/Zeiss-2000 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/43771. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41880] GRB 260208A: continued Mondy optical observations
by GCN Circulars 17 Feb '26

17 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43770 SUBJECT: GRB 260208A: continued Mondy optical observations DATE: 26/02/17 14:07:31 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 GRB 260208A (Fermi GBM team, GCN 43635; Sonawane et al. 2026, GCN 43642; Longo et al. 2026, GCN 43645; Dichiara et al. 2026, GCN 43652; Luo et al. 2026, GCN 43658; Mukherjee & Meegan, GCN 43673; Waratkar & Grefenstette, GCN 43674; Cheung et al., GCN 43675) at z = 2.36 (Dimple et al., GCN 43662) with the AZT-33IK 1.5m telescope of the Mondy observatory on Feb. 9 and 10 taking several 120-seconds frames in the R band. The optical counterpart (Lipunov et al., GCN 43640; Wortley et al., GCN 43641; Dichiara et al., GCN 43652; Ma et al., GCN 43655; Ahumada et al., GCN 43657; Dimple et al., GCN 43661; Magnani et al., GCN 43664; Gupta et al., GCN 43665; Volnova et al., GCN 43666; Pérez-Fournon et al., GCN 43694; Kuin & Cenko, GCN 43702) is detected in the stacked frame from Feb. 09, and is not detected on the next day. 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) 2026-02-09 17:00:51 1.51973 35*120 R 21.58 0.10 22.6 Mondy/AZT-33IK 2026-02-10 17:58:12 2.55608 30*120 R n/d n/d 22.6 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/43770. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41879] IPN triangulation of GRB 260212A
by GCN Circulars 17 Feb '26

17 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43769 SUBJECT: IPN triangulation of GRB 260212A DATE: 26/02/17 12:10:47 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi-GBM team, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, A. Tohuvavohu, and J. DeLaunay on behalf of the Swift-BAT team, and W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The long-duration GRB 260212A (Ferm-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) was detected by Fermi (GBM trigger 792611353), Swift (BAT), Konus-Wind, Glowbug, SVOM (GRM), GECAM-B, Astrosat (CZTI), and Mars-Odyssey (HEND) at about 64148 s UT (17:49:08) The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 224.837 (14h 59m 21s) +74.800 (+74d 47' 59") Corners: 225.022 (15h 00m 05s) +76.212 (+76d 12' 45") 224.790 (14h 59m 09s) +73.505 (+73d 30' 18") 224.644 (14h 58m 35s) +73.384 (+73d 23' 04") 224.855 (14h 59m 25s) +76.092 (+76d 05' 30") --------------------------------------------- The error box area is 372 sq. arcmin, and its maximum dimension is 2.830 deg (the minimum one is 2.3 arcmin). The Sun distance was 106 deg. This localization may be improved. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB260212_T64149/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/43769. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41878] IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 17 Feb '26

17 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43768 SUBJECT: IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 26/02/17 11:46:06 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 26-02-17 at 05:55:24.52 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_BRONZE alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 2.768 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert, more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 26-02-17 Time: 05:55:24.52 UT RA: 75.89 (+0.52/-0.56 deg 90% PSF containment) J2000 Dec: 14.63 (+0.45/-0.43 deg 90% PSF containment) J2000 No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of this event. As announced in GCN Circular 43419, IceCube alert notices for high-energy track alerts are now also streamed via Kafka. IceCube Gold/Bronze track alerts are available on the Kafka topic 'gcn.notices.icecube.gold_bronze_track_alerts'. The probability distribution of the true neutrino direction, allowing the extraction of precise 90% containment regions around the best-fit direction, is now available for revised reconstruction of high-energy track alerts. Additional information is available at https://gcn.nasa.gov/missions/icecube. The initial automated alert was not distributed through the classical GCN notice system, and the cause is currently under investigation. Meanwhile, the Kafka notification was streamed with an approximate delay of 30 minutes due to a temporary technical issue. As a result, the initial GCN schema (“record_number” = 0) streamed via Kafka contains some errors (this is not the case for the GCN schema (“record_number” = 1), corresponding to the updated reconstruction, which is sent along with this circular). Specifically: The fields “ra_dec_error” and “far” were sent as strings instead of numerical values. record_number was sent as 1, but it should have been 0. The field “p_astro” was sent as a percentage (30.722) instead of a decimal fraction; the correct value is 0.31. 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/43768. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41877] GRB 260213A: GECAM-B observation of a short burst
by GCN Circulars 17 Feb '26

17 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43767 SUBJECT: GRB 260213A: GECAM-B observation of a short burst DATE: 26/02/17 08:42:41 GMT FROM: Xinghao Luo at IHEP <2952704891(a)qq.com> Xing-Hao Luo, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 260213A, at 2026-02-13T08:23:49.800 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43722). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 1.5 +/-0.7 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260213A.png The 'Amati' relation diagram of GRB 260213A is shown at: https://www.bursthub.cn//admin/static/gecambgrb260213A_amati.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/43767. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41876] GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB
by GCN Circulars 17 Feb '26

17 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43766 SUBJECT: GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB DATE: 26/02/17 04:23:20 GMT FROM: Boyan A. Hristov at UAH <boyan.a.hristov(a)nasa.gov> B. Hristov (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 792969362/260216886 at 21:15:57.07 UT on 16 February 2026, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to distant particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/43766. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41875] GRB 260216A: Fermi GBM Final Real-time Localization
by GCN Circulars 16 Feb '26

16 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43765 SUBJECT: GRB 260216A: Fermi GBM Final Real-time Localization DATE: 26/02/16 21:26:38 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 21:15:57 UT on 16 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260216A (trigger 792969362.07265 / 260216886). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 292.5, Dec = -25.0 (J2000 degrees, equivalent to J2000 19h 30m, -25d 00'), with a statistical uncertainty of 12.6 degrees. The angle from the Fermi LAT boresight is 127.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260216886/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260216886/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260216886/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43765. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41874] EP260214b: Liverpool Telescope optical observations
by GCN Circulars 16 Feb '26

16 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43764 SUBJECT: EP260214b: Liverpool Telescope optical observations DATE: 26/02/16 14:12:34 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 EP 260214b (Yang et al., GCN 43744; Yang et al., GCN 43760) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 5x100s exposures in SDSS g filter and 6x100s in SDSS r and i, starting at 2026-02-16 02:51:39.908 UT, approximately 28.8 hours after trigger. Some exposures were discarded prior to stacking due to poor seeing. They were subtracted from PanSTARRS reference images using PSF matching with the use of PSFEx. We report detections in stacked images in all filters at the position first reported by He et al., GCN 43745 and Watson et al., GCN 43747. MJD (mid) T_mid-T_0 Filter Mag. (AB) 61087.12195 28.86 h g 22.45 ± 0.27 61087.13116 29.08 h r 22.22 ± 0.33 61087.13913 29.27 h i 21.75 ± 0.24 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/43764. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41873] GRB 260206A: probable hard X-ray burst from 4U 0513-40
by GCN Circulars 16 Feb '26

16 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43763 SUBJECT: GRB 260206A: probable hard X-ray burst from 4U 0513-40 DATE: 26/02/16 11:32:52 GMT FROM: Hitoshi Negoro at Nihon University/MAXI team <negoro.hitoshi(a)nihon-u.ac.jp> H. Negoro, M. Nakajima (Nihon U.), J.A. Kennea (PSU), T. Mihara (RIKEN) This is a cross-posting of ATel 17682. In Swift-XRT followup observations of GRB 260206A detected with the MAXI-GSC (GCN Circ. 43624), the XRT marginally detected a faint, uncatalogued X-ray source near the center of the MAXI error region (Lenava et al. GCN Circ. 43630). The XRT also detected a bright known X-ray source, LSXPS J051406.5-400237, of which a count rate was 7.3 +/- 0.3 cts/s, approximately 70% higher than the mean count rate (Source 1: Evans et al. GCN Circ. 43625). We analyzed the GSC energy spectrum of the burst, and found that a power-law model gave a better fit to the spectrum than a blackbody model. This is because many hard X-ray photons were detected above 10 keV. We fixed the equivalent hydrogen column density to 3.84e20 (obtained with the nH Calculator at NASA/HEASARC for the direction of 4U 0513-40), and obtained a photon index of 1.7 (+0.7, -0.6 at 90% confidence interval) and a blackbody temperature of 1.5 (+0.6, - 0.4) keV in each fit. The burst exhibited a double-peaked-like structure with an e-folding decay time of 5.8 +/- 1.0 sec at 2-20 keV without any collimator response correction. The peak X-ray flux is around 1.22e-8 erg/cm2/s at 2-10 keV, which corresponds to 2.2e38 erg/s if the source is in the globular cluster NGC 1851 hosting 4U 0513-40 (aka X0512-401) (12.2 kpc away). MAXI detected more than ten X-ray bursts with a variety of time profiles originating from the direction of NGC 1851. These strongly suggest that this hard energetic burst also came from 4U 0513-40 (or ABK A, see Homer et al. 2001, ApJ, L155), within the error circle of LSXPS J051406.5-400237, though 4U 0513-40 is just outside the MAXI error box if we take account of the systematic uncertainty of the localization, 0.1 deg (GCN Circ. 43624). View this GCN Circular online at https://gcn.nasa.gov/circulars/43763. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41872] EP260214b: Optical upper limit with Kinder observations
by GCN Circulars 16 Feb '26

16 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43762 SUBJECT: EP260214b: Optical upper limit with Kinder observations DATE: 26/02/16 10:28:20 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> A. Aryan, C.-S. Lin, T.-W. Chen (all NCU), A. K. H. Kong (NTHU), J. H. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), Y.-H. Lee, A. Sankar.K, M.-H. Lee, C.-H. Lai, Y.-C. Pan, C.-C. Ngeow, W.-J. Hou, H.-Y. Hsiao, H.-C. Lin, J.-K. Guo (all NCU), S. Yang, Z. N. Wang, L. L. Fan, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz, and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP260214b (Yang et al., GCN 43744 & GCN 43760) using the 1m LOT at the Lulin observatory, as part of the Kinder collaboration (Chen & Yang et al. 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The first LOT epoch of observations in r-band started at 14:34 UTC on the 15th of February 2026 (MJD 61086.607), 16.50 hr after the EP-WXT trigger. We utilized the astroalign (Beroiz et al. 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al. 2022, ApJ, 935, 167) packages to align and stack the individual frames. We used the Python-based AutoPhOT package (Brennan & Fraser 2022, A&A, 667, A62) to perform template subtraction with the DESI Legacy Survey (Dey et al. 2019, AJ 157, 168) DR10 image using the 'SFFT' (Hu et al. 2022, ApJ, 936, 157) algorithm. In the stacked frame or the difference image, we did not detect the proposed optical counterpart reported by He et al. (GCN 43745). Moreover, we used AutoPhOT to perform PSF photometry. The details of the observations and the measured 3-sigma upper limits (in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass LOT | r | 61086.607 | 16.50 | 300 * 6 | >22.2 | 1".76 | 1.85 The non-detection in our observations is consistent with (detection) reports 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), and also with the upper limit reported by Vijaykumar et al. (GCN 43757). The presented magnitude is calibrated using the field stars from the Pan-Starrs catalog and is not corrected for the expected Galactic foreground extinction of A_r = 0.04 mag in the direction of the transient (Schlafly & Finkbeiner 2011). The methodology, details on the Lulin observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein-Probe mission are presented in Aryan et al. 2025, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69. View this GCN Circular online at https://gcn.nasa.gov/circulars/43762. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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