March 2026 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 42240] GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
by GCN Circulars 26 Mar '26

26 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44119 SUBJECT: GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope DATE: 26/03/26 13:15:35 GMT FROM: Y.C. Kang at Peking University <yckang(a)stu.pku.edu.cn> Yacheng Kang, Qiang Wang, Ruize Shi, Zexuan Wu, Zhuokai Liu, Yiming Dong, Ziming Wang, Chenxi Bao, Fangzhou Ren, Lijing Shao, Zhuo Li, Subo Dong (PKU) report on behalf of the PKU HiTF (High-energy Transients Follow-up) group: The field of GRB 260310A (Fermi GBM Team, GCN 43951; Salunke et al., GCN 43958) was observed with the PKU 60 cm optical telescope at Xinglong Observatory, NAOC. Observations began on 2026 Mar 18, corresponding to ~8.6 days after the GRB trigger, and were conducted over a total of three epochs. In the stacked R- and I-band images, we clearly detect the optical counterpart AT2026fgk (e.g., Konno et al., GCN 43974; Hinds et al., GCN 43977; Lipunov et al., GCN 43978; Martin-Carrillo et al., GCN 43979; Moreno Méndez et al., GCN 43980; de Ugarte Postigo et al., GCN 43984; Hsu et al., GCN 43986; Malesani et al., GCN 43990; Becerra et al., GCN 43991; Li et al., GCN 43993; Stein et al., GCN 43996; Martin-Carrillo et al., GCN 44000; Watson et al., GCN 44001; Lai et al., GCN 44002; Izzo et al., GCN 44003; Brivio et al., GCN 44004; Moskvitin et al., GCN 44006; Romanov, GCN 44020; Brosio et al., GCN 44021; Pawar et al., GCN 44022; Belkin et al., GCN 44043; Li et al., GCN 44044; Gupta et al., GCN 44051; Passaleva et al., GCN 44058; Becerra et al., GCN 44059; Volnova et al., GCN 44060; Busmann et al., GCN 44061; Zheng et al., GCN 44065; Brosio et al., GCN 44067; Pankov et al. GCN 44073; Perley et al. GCN 44096; Passaleva et al. GCN 44104; Serrau et al. GCN 44112; O'Neill et al. 2026, TNS Discovery Report 294132). Preliminary photometry yields R-band magnitudes ranging from ~18.7 to ~18.9 mag and I ~ 18.5 mag, calibrated against nearby Pan-STARRS field stars and reported in the Vega system, without correction for Galactic extinction. The observation log is summarized below (T0 = 2026-03-10T04:57:10.81; GRB 260310A): | Date | Start_UT | T_mid − T0 (days) | Filter | Exposure (s) | Magnitude (Vega) | | :--------: | :---------: | :---------------: | :----: | :----------: | :--------------: | | 2026-03-18 | 20:23:26.87 | 8.66 | R | 4 * 600 | 18.66 +/- 0.03 | | 2026-03-19 | 16:22:31.97 | 9.53 | I | 15 * 600 | 18.45 +/- 0.03 | | 2026-03-19 | 18:57:02.55 | 9.63 | R | 14 * 600 | 18.90 +/- 0.03 | Further analysis and follow-up observations are ongoing. The 60 cm telescope is operated by the Department of Astronomy, School of Physics, Peking University. The PKU HiTF group is dedicated to rapid follow-up observations of high-energy transients. View this GCN Circular online at https://gcn.nasa.gov/circulars/44119. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42239] GRB 260326A: Fermi GBM Detection
by GCN Circulars 26 Mar '26

26 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44118 SUBJECT: GRB 260326A: Fermi GBM Detection DATE: 26/03/26 11:21:12 GMT FROM: Utkarsh Pathak at IIT Bombay <utkarshpathak.07(a)gmail.com> U. Pathak (IITB) and S. Bala (USRA) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 01:18:28.51 UT on 26 March 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260326A (trigger 796180713/260326054). The Fermi GBM real-time Localization is reported in GCN 44115. The angle from the Fermi LAT boresight is 76 degrees. The GBM light curve consists of two spikes from a single emission episode with a duration (T90) of about 50 s (50-300 keV). The time-averaged spectrum from T0-6.0 to T0+66.0 s is best fit by a Band function with Epeak = 275 +/- 1 keV, alpha = -1.040 +/- 0.004, and beta = -2.00 +/- 0.01. The event fluence (10-1000 keV) in this time interval is (5.37 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+7.0 s in the 10-1000 keV band is 32.6 +/- 0.4 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/44118. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42238] EP260321a: JinShan near-infrared observations
by GCN Circulars 26 Mar '26

26 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44117 SUBJECT: EP260321a: JinShan near-infrared observations DATE: 26/03/26 07:29:39 GMT FROM: liuxing(a)nao.cas.cn Lin. B. He, X. Liu (NAOC), S.Y. Fu, A.D. Zhu, L. Lei, H.Z. Wu, W.H. Lei, Y.C. Zou (HUST), J. An, S.Q. Jiang, Z.P. Zhu, D. Xu (NAOC), J.Z. Liu (XAO), Zhong-Nan Dong, Bin Ma (Sun Yat-sen University) We observed the field of EP260321a (Huang et. al, GCN 44068) using the JinShan 100C telescope, equipped with the INS Mars640 SWIR Camera, located at Altay, Xinjiang, China. Observation started at 2026-03-25 15:12:02 UT, i.e., 4.11 days post-burst, and a series of J-band frames were obtained. The optical counterpart (Lee et al., GCN 44070; Tanvir et al., GCN 44082; Moran et al., GCN 44083; Ahumada et al., GCN 44084; Liu et al., GCN 44087; de Ugarte Postigo et al., GCN 44091; Xu et al., GCN 44092; Pankov et al. GCN 44103; Corcoran et al., GCN 44105; Rastinejad et al., GCN 44107; Gao et al., GCN 44110) was detected in our stacked J-band frame with magnitude J ~ 17.2 (Vega) at a mid-time 99.3 hrs post-burst. The magnitude was calibrated with the nearby 2MASS catalog and without the Galactic extinction correction. We acknowledge the excellent support from T.Q. Chen for enabling these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44117. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42237] GRB 260325A: Fermi GBM Final Localization
by GCN Circulars 26 Mar '26

26 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44116 SUBJECT: GRB 260325A: Fermi GBM Final Localization DATE: 26/03/26 02:06:55 GMT FROM: Suman Bala at USRA <sumanbala2210(a)gmail.com> The Fermi GBM team reports the detection of a likely LONG GRB "At 23:39:37.55 UT on 25 March 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260325A (trigger 796174782/260325986). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 113.3, Dec = -59.7 (J2000 degrees, equivalent to J2000 7h 33m, -59d 43'), with a statistical uncertainty of 3.2 degrees. The angle from the Fermi LAT boresight is 134 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260325986/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260325986/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260325986/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/44116. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42236] GRB 260326A: Fermi GBM Final Real-time Localization
by GCN Circulars 26 Mar '26

26 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44115 SUBJECT: GRB 260326A: Fermi GBM Final Real-time Localization DATE: 26/03/26 01:28:58 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 01:18:28 UT on 26 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260326A (trigger 796180713.505606 / 260326054). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 97.9, Dec = 25.4 (J2000 degrees, equivalent to J2000 06h 31m, 25d 23'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 76.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260326054/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260326054/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260326054/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44115. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42235] EP260321a: Upper limits from a neutrino search with IceCube
by GCN Circulars 25 Mar '26

25 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44114 SUBJECT: EP260321a: Upper limits from a neutrino search with IceCube DATE: 26/03/25 21:30:19 GMT FROM: Sam Hori at IceCube/U Wisc-Madison <sahori(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search for track-like muon neutrino events arriving from the direction of the X-ray transient EP260321a which was first detected by Einstein Probe (https://gcn.nasa.gov/circulars/events/ep260321a#gcn-circular-44068) to investigate possible neutrino emission associated with the shock breakout scenario proposed for this event. The position of the updated localization (https://gcn.nasa.gov/circulars/events/ep260321a#gcn-circular-44075) was searched over a time window covering the time range between [-3 hours, +1 hours] from Einstein Probe detection (2026-03-21 09:23:07 UTC to 2026-03-21 13:23:07 UTC), during which time IceCube was recording good quality data. The chosen time window is motivated by the shock breakout scenario, to account for possible high-energy neutrino emission produced during the shock propagation within the stellar envelope and in the immediate aftermath of the breakout. In this case, we report a p-value of 1.0, consistent with background expectation. We accordingly derive a time-integrated muon-neutrino flux upper limit for this source of E^2 dN/dE = 2.8 x 10^-2 GeV cm^-2 at 90% CL, under the assumption of an E^-2 power law. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum have energies in the approximate energy range between 1 TeV and 6 PeV. 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. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/44114. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42234] Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
by GCN Circulars 25 Mar '26

25 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44113 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB DATE: 26/03/25 17:59:12 GMT FROM: Daniel Fernandez at University of Alabama In Huntsville (UAH) <df0062(a)uah.edu> D. Fernandez (UAH) and L. Scotton (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 796145512/260325647 at 15:31:47.56 UT on 25 March 2026, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to Local Particles due to SAA entry." View this GCN Circular online at https://gcn.nasa.gov/circulars/44113. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42233] GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
by GCN Circulars 25 Mar '26

25 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44112 SUBJECT: GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time DATE: 26/03/25 14:03:49 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> M. Serrau, M. Freeberg (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (OCA/IJCLab), M. Coughlin (UMN),S. Karpov (FZU), P. Hello (IJCLAB), M. Pillas (IAP) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 260310 detected by Fermi/GBM (Fermi GBM team, GCN 43951) and AstroSat CZTI (Salunke et al., GCN 43958) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the ODK16 telescope at Observatoire Banon La Tuilerie, France operated by M. Serrau and the TEC160FL telescope operated by M. Freeberg. Our observations started at TGRB+14.8 days and were taken with sdss-g and sdss-r filters. In our stacked frames, subtracted from the Legacy Survey DR10 template image, we detect the optical counterpart reported by GOTO (O'Neill et al. 2026, TNS Discovery Report 294132) and observed earlier (Konno et al., GCN 43974; Hinds et al., GCN 43977; Lipunov et al., GCN 43978;Martin-Carrillo et al., GCN 43979; Méndez et al., GCN 43980;de Ugarte Postigo et al., GCN 43984; Hsu et al., GCN 43986; Pursiainen et al., GCN 43990; Becerra et al., GCN 43991; Li et al., GCN 43993; Jayaraman et al., GCN 43994; Stein et al., GCN 43996;Martin-Carrillo et al., GCN 44000; Moreno Méndez et al., GCN 43980; Becerra et al., GCN 43991; Li et al., GCN 43993; Stein et al., GCN 43996; Watson et al., GCN 44001; Lai et al., GCN 44002; Izzo et al., GCN 44003; Brivio et al., GCN 44004; Moskvitin et al., GCN 44006; Romanov, GCN 44020; Brosio et al., GCN 44021; Pawar et al., GCN 44022; Belkin et al., GCN 44043; Li et al., GCN 44044; Gupta et al., GCN 44051; Becerra et al., GCN 44059; Volnova et al., GCN 44060; Busmann et al., GCN 44061; Zheng et al., GCN 44065; Brosio et al., GCN 44067; Pankov et al. GCN 44073; Perley et al. GCN 44096; Passaleva et al. GCN 44104) We report part of our follow-up results in the table below +------------------+-----------+--------+----------------+-------------+ | Tmid-TGRB (days) | Exp (s) | Filter | Magnitude | Instrument | +==================+===========+========+================+=============+ | 14.83 | 16 x 300s | r (AB) | 19.96 +/- 0.09 | ODK16 | | 15.17 | 17 x 180s | r (AB) | 19.82 +/- 0.12 | TEC160FL | +------------------+-----------+--------+----------------+-------------+ The KNC members will keep monitoring the source in the coming days. All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the sloan filters were calibrated using the PanSTARRS DR1 catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/) View this GCN Circular online at https://gcn.nasa.gov/circulars/44112. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42232] IPN triangulation of GRB 260316B
by GCN Circulars 25 Mar '26

25 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44111 SUBJECT: IPN triangulation of GRB 260316B DATE: 26/03/25 13:33:31 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. Goyal, A. Arya, M. Tembhurnikar, G. Waratkar, V. Bhalerao, D. Bhattacharya, and S. Vadawale, on behalf of the Astrosat-CZTI team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi-GBM 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 260316B (Ferm-GBM detection: The Fermi GBM team, GCN 44031; AstroSat-CZTI detection: Harsha et al., GCN 44035; SVOM-GRM detection: Zhang et al., GCN 44039; GECAM-B detection: Zhang et al., GCN 44040; CALET-GBM detection: Tamura et al., GCN 44100) was detected by Fermi (GBM trigger 795373977), Konus-Wind, Astrosat (CZTI), SVOM (GRM), GECAM-B, CALET (GBM), and Mars-Odyssey (HEND) at about 61973 s UT (17:12:53). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 345.026 (23h 00m 06s) -80.127 (-80d 07' 37") Corners: 292.551 (19h 30m 12s) -74.130 (-74d 07' 48") 293.015 (19h 32m 04s) -74.416 (-74d 24' 57") 32.817 (02h 11m 16s) -74.223 (-74d 13' 24") 32.021 (02h 08m 05s) -74.386 (-74d 23' 10") --------------------------------------------- The error box area is 1.7 sq. deg, and its maximum dimension is 24.2 deg (the minimum one is 4.3 arcmin). The Sun distance was 75 deg. This localization may be improved. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB260316_T61972/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/44111. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42231] EP260321a: J-band observations by the SYSU 80 cm infrared telescope
by GCN Circulars 25 Mar '26

25 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44110 SUBJECT: EP260321a: J-band observations by the SYSU 80 cm infrared telescope DATE: 26/03/25 09:38:42 GMT FROM: Rui-Chen Gao <ayxzxn0100(a)gmail.com> Rui-Chen Gao, Chun Chen, Duo-Le Cao, Zhong-Nan Dong, Wei-Sen Huang, Jin-Ji Li, Jia-Qi Lin, Pu Lin, Yun Shi, Hao-Nan Yang, Yan Yu, P H Thomas Tam, Rong-Feng Shen, Bin Ma (Sun Yat-sen University) report on behalf of the SYSU 80cm infrared telescope team: We observed the field of the fast X-ray transient EP260321a(Huang et. al, GCN 44068), using the Sun Yat-sen University (SYSU) 80 cm infrared telescope. Our observations were carried out on 2026 Mar 24 18:57 UT, 78.4 hours after the trigger, using stacked images in the J band. We clearly detect the source at the position of the optical counterpart (Lee et al., GCN 44070; Tanvir et al., GCN 44082; Moran et al., GCN 44083, Ahumada et al., GCN 44084, Liu et al., GCN 44087, de Ugarte Postigo et al., GCN 44091, Xu et al., GCN 44092, Pankov et al. GCN 44103, Corcoran et al., GCN 44105, Rastinejad et al., GCN 44107), and we measure J = 17.489 +/- 0.232 Vega mag. The photometry was calibrated against nearby stars from the 2MASS catalog and is reported in the Vega system, without correction for Galactic extinction. Further observations are ongoing. The SYSU 80 cm infrared telescope is operated and managed by the Department of Astronomy, Sun Yat-sen University. View this GCN Circular online at https://gcn.nasa.gov/circulars/44110. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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