September 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 40013] GRB 250920C: NIR observations with WINTER
by GCN Circulars 22 Sep '25

22 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41947 SUBJECT: GRB 250920C: NIR observations with WINTER DATE: 25/09/22 22:40:56 GMT FROM: Geoffrey Mo at Caltech / Carnegie Observatories <gmo(a)mit.edu> Geoffrey Mo (Caltech/Carnegie), Tomas Ahumada (Caltech), Viraj Karambelkar (Columbia), Benjamin Schneider (LAM), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of GRB 250920C (Fermi GBM Team, GCN 41903; Gupta et al., GCN 41904; Mailyan et al., GCN 41917; Goad et al., GCN 41922; Gupta et al., GCN 41924; SVOM Team, GCN 41929; Evans et al., GCN 41935) 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 2025-09-21T08:59:42.591 UTC in the J band (~17.5 hours 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 (Wortley et al., GCN 41907; Strausbaugh et al., GCN 41911; Ghosh et al., GCN 41913; Lipunov et al., GCN 41916; Kuin et al., GCN 41920; Mohan et al., GCN 41925; Sanchez-Ramirez et al., GCN 41928; Guiffreda et al., GCN 41943). We obtain the following 5-sigma upper limit: J ~ 19.0 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/41947. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40012] GRB 250920B: NIR observations with WINTER
by GCN Circulars 22 Sep '25

22 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41946 SUBJECT: GRB 250920B: NIR observations with WINTER DATE: 25/09/22 22:39:42 GMT FROM: Geoffrey Mo at Caltech / Carnegie Observatories <gmo(a)mit.edu> Geoffrey Mo (Caltech/Carnegie), Tomas Ahumada (Caltech), Viraj Karambelkar (Columbia), Benjamin Schneider (LAM), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of GRB 250920B (Fermi GBM team, GCN 41897; Gupta et al., GCN 41898; Page et al., GCN 41909; Evans et al., GCN 41910; Sonawane et al., GCN 41919; Sakamoto et al., GCN 41923; Cheung et al., GCN 41937) 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 2025-09-21T02:30:43.439 UTC in the J band (~17.7 hours 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 candidate location (Lipunov et al., GCN 41901; Wu et al., GCN 41908; Hall et al., GCN 41914; Kuin et al., GCN 41915; Pankov et al., GCN 41931; Reguitti et al., GCN 41932). We obtain the following 5-sigma upper limit: J ~ 18.9 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/41946. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40011] Fermi trigger No 780156732: Global MASTER-Net observations report
by GCN Circulars 22 Sep '25

22 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41945 SUBJECT: Fermi trigger No 780156732: Global MASTER-Net observations report DATE: 25/09/22 21:31:17 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB250921.59 (trigger No 780156732,20h 24m 04.08s , +00d 33m 00.0s, R=33.5) errorbox 42698 sec after notice time and 42707 sec after trigger time at 2025-09-22 02:03:54 UT, with upper limit up to 20.3 mag. The observations began at zenith distance = 26 deg. The sun altitude is -44.3 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB250921.59 errorbox 1 days 6573 sec after notice time and 1 days 6582 sec after trigger time at 2025-09-22 16:01:50 UT, with upper limit up to 17.7 mag. Observations started at twilight. The observations began at zenith distance = 38 deg. The sun altitude is -10.5 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB250921.59 errorbox 1 days 17595 sec after notice time and 1 days 17604 sec after trigger time at 2025-09-22 19:05:31 UT, with upper limit up to 19.4 mag. The observations began at zenith distance = 43 deg. The sun altitude is -32.0 deg. The galactic latitude b = -21 deg., longitude l = 45 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2996777 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 42737 | 2025-09-22 02:03:54 | MASTER-OAFA | (19h 50m 28.63s , -19d 46m 33.6s) | C | 60 | 19.6 | 42813 | 2025-09-22 02:05:10 | MASTER-OAFA | (19h 59m 04.47s , -19d 46m 40.4s) | C | 60 | 19.9 | 42985 | 2025-09-22 02:08:02 | MASTER-OAFA | (19h 50m 31.65s , -19d 46m 10.8s) | C | 60 | 19.6 | 43060 | 2025-09-22 02:09:17 | MASTER-OAFA | (19h 59m 05.00s , -19d 44m 57.1s) | C | 60 | 19.8 | 43229 | 2025-09-22 02:12:06 | MASTER-OAFA | (19h 50m 28.14s , -19d 44m 25.3s) | C | 60 | 19.6 | 43305 | 2025-09-22 02:13:22 | MASTER-OAFA | (19h 53m 08.47s , -17d 52m 34.7s) | C | 60 | 19.7 | 43381 | 2025-09-22 02:14:38 | MASTER-OAFA | (20h 01m 37.51s , -17d 52m 26.1s) | C | 60 | 19.9 | 43457 | 2025-09-22 02:15:54 | MASTER-OAFA | (19h 53m 11.41s , -17d 50m 53.1s) | C | 60 | 19.7 | 43532 | 2025-09-22 02:17:09 | MASTER-OAFA | (20h 01m 35.40s , -17d 52m 38.4s) | C | 60 | 19.9 | 43608 | 2025-09-22 02:18:25 | MASTER-OAFA | (19h 53m 15.09s , -17d 50m 57.3s) | C | 60 | 19.8 | 43692 | 2025-09-22 02:19:49 | MASTER-OAFA | (21h 04m 54.78s , -14d 06m 56.2s) | C | 60 | 20.2 | 43767 | 2025-09-22 02:21:05 | MASTER-OAFA | (21h 13m 04.77s , -14d 08m 17.9s) | C | 60 | 20.0 | 43843 | 2025-09-22 02:22:20 | MASTER-OAFA | (21h 04m 55.21s , -14d 07m 38.0s) | C | 60 | 20.1 | 43920 | 2025-09-22 02:23:37 | MASTER-OAFA | (21h 13m 07.40s , -14d 06m 29.2s) | C | 60 | 20.0 | 43996 | 2025-09-22 02:24:53 | MASTER-OAFA | (21h 04m 52.78s , -14d 07m 39.7s) | C | 60 | 20.1 | 44074 | 2025-09-22 02:26:12 | MASTER-OAFA | (21h 11m 50.89s , -23d 36m 50.4s) | C | 60 | 20.2 | 44150 | 2025-09-22 02:27:27 | MASTER-OAFA | (21h 20m 32.85s , -23d 36m 14.1s) | C | 60 | 20.1 | 44226 | 2025-09-22 02:28:44 | MASTER-OAFA | (21h 11m 57.12s , -23d 36m 47.6s) | C | 60 | 20.1 | 44302 | 2025-09-22 02:30:00 | MASTER-OAFA | (21h 20m 33.70s , -23d 38m 10.5s) | C | 60 | 20.1 | 44377 | 2025-09-22 02:31:15 | MASTER-OAFA | (21h 11m 56.17s , -23d 37m 33.3s) | C | 60 | 20.1 | 45719 | 2025-09-22 02:53:36 | MASTER-OAFA | (21h 41m 12.76s , -29d 09m 13.2s) | C | 60 | 20.2 | 45873 | 2025-09-22 02:56:10 | MASTER-OAFA | (21h 41m 10.27s , -29d 08m 40.6s) | C | 60 | 20.3 | 46022 | 2025-09-22 02:58:40 | MASTER-OAFA | (21h 41m 16.52s , -29d 08m 42.0s) | C | 60 | 20.3 | 49433 | 2025-09-22 03:55:30 | MASTER-OAFA | (21h 20m 37.25s , -23d 35m 53.7s) | C | 60 | 20.1 | 49589 | 2025-09-22 03:58:07 | MASTER-OAFA | (21h 20m 36.58s , -23d 36m 52.5s) | C | 60 | 20.0 | 49744 | 2025-09-22 04:00:42 | MASTER-OAFA | (21h 20m 40.36s , -23d 35m 16.2s) | C | 60 | 20.1 | 49907 | 2025-09-22 04:03:24 | MASTER-OAFA | (21h 41m 27.25s , -29d 17m 23.8s) | C | 60 | 20.2 | 49982 | 2025-09-22 04:04:39 | MASTER-OAFA | (21h 41m 21.20s , -29d 18m 22.1s) | C | 60 | 20.1 | 50059 | 2025-09-22 04:05:56 | MASTER-OAFA | (21h 41m 20.91s , -29d 17m 20.7s) | C | 60 | 20.2 | 93012 | 2025-09-22 16:01:50 | MASTER-Kislovodsk | (19h 09m 53.50s , +05d 21m 18.7s) | C | 60 | 16.7 | 93012 | 2025-09-22 16:01:50 | MASTER-Kislovodsk | (19h 10m 08.91s , +04d 56m 58.0s) | C | 60 | 16.9 | 96648 | 2025-09-22 17:02:26 | MASTER-Kislovodsk | (19h 11m 04.53s , +05d 11m 24.6s) | C | 60 | 16.9 | 96648 | 2025-09-22 17:02:26 | MASTER-Kislovodsk | (19h 10m 54.81s , +05d 34m 26.2s) | C | 60 | 17.7 | 104034 | 2025-09-22 19:05:31 | MASTER-SAAO | (22h 42m 26.01s , -01d 06m 41.5s) | C | 60 | 19.2 | 104034 | 2025-09-22 19:05:31 | MASTER-SAAO | (22h 40m 35.17s , -00d 51m 17.4s) | C | 60 | 19.3 | 104131 | 2025-09-22 19:07:08 | MASTER-SAAO | (22h 42m 35.06s , +00d 47m 13.4s) | C | 60 | 19.4 | 104131 | 2025-09-22 19:07:08 | MASTER-SAAO | (22h 40m 44.35s , +01d 02m 37.1s) | C | 60 | 19.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/41945. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40010] GRB 250922B: Fermi GBM Final Real-time Localization
by GCN Circulars 22 Sep '25

22 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41944 SUBJECT: GRB 250922B: Fermi GBM Final Real-time Localization DATE: 25/09/22 21:24:08 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 SHORT GRB At 21:13:25 UT on 22 Sep 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250922B (trigger 780268410.863384 / 250922884). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 48.7, Dec = 30.7 (J2000 degrees, equivalent to J2000 03h 14m, 30d 41'), with a statistical uncertainty of 13.4 degrees. The angle from the Fermi LAT boresight is 90.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250922884/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250922884/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250922884/… View this GCN Circular online at https://gcn.nasa.gov/circulars/41944. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40009] GRB 250920C: PRIME near-infrared detection
by GCN Circulars 22 Sep '25

22 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41943 SUBJECT: GRB 250920C: PRIME near-infrared detection DATE: 25/09/22 20:28:38 GMT FROM: O. Guiffreda at UMD <oriogui(a)umd.edu> O. Guiffreda (UMD), J. Durbak (UMD), A. S. Kutyrev (NASA/GSFC), N. Passaleva (U Rome), M. El Kabir (U Rome), E. Troja (U Rome), S. B. Cenko (NASA/GSFC) Following the Fermi GBM (GCN 41903) and Swift BAT (GCN 41904), we observed the transient field in Z, Y, J and H filters with PRIME ~7 hours after the initial Fermi and Swift detection. At the position of the optical counterpart reported by GOTO (GCN 41907), we detect an uncatalogued source in all aforementioned bands. Using nearby 2MASS and PanSTARRS stars for preliminary calibration we derive the following magnitudes and limits, not corrected for Galactic extinction: |Filter | Mag(AB) | |-------|---------------| |Z | 19.7 +/- 0.10 | |Y | 19.7 +/- 0.07 | |J | 18.8 +/- 0.10 | |H | 18.0 +/- 0.07 | PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023, Durbak et al. 2024). We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/41943. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40008] Konus-Wind detection of GRB 250920B
by GCN Circulars 22 Sep '25

22 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41942 SUBJECT: Konus-Wind detection of GRB 250920B DATE: 25/09/22 18:37:52 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 long-duration GRB 250920B (Fermi-GBM detection: The Fermi GBM team, GCN 41897; Sonawane and Meegan, GCN 41919; Swift-BAT detection: Gupta et al., GCN 41898; Sakamoto et al., GCN 41923; Glowbug detection: Cheung et al., GCN 41937) triggered Konus-Wind at T0=31587.304 s UT (08:46:27.304). The burst light curve shows a multipeaked structure which starts at ~T0-3.0 s and has a total duration of ~141 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250920_T31587/ As observed by Konus-Wind, the burst had the total fluence of 3.80(-0.78,+0.93)x10^-5 erg/cm2, and the 64-ms peak flux, measured from T0+6.368 s, of 6.72(-1.17,+1.16)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+131.328 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 = -1.41(-0.10,+0.11), the high energy photon index beta = -2.41(-7.59,+0.35), the peak energy Ep = 310(-69,+94) keV (chi2 = 94/97 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+8.448 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 = -1.06(-0.10,+0.10), the high energy photon index beta = -2.33(-0.38,+0.18), the peak energy Ep = 296(-38,+52) keV (chi2 = 87/81 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/41942. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40007] Konus-Wind detection of GRB 250920A
by GCN Circulars 22 Sep '25

22 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41941 SUBJECT: Konus-Wind detection of GRB 250920A DATE: 25/09/22 18:33:59 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 250920A (Ferm-GBM detection: The Fermi GBM team, GCN 41895; Sonawane and Smith, GCN 41918; BALROG localization: Preis and Greiner, GCN 41896 AstroSat-CZTI detection: Harsha et al., GCN 41899; SVOM-GRM detection: Wang et al., GCN 41912; NuSTAR-detection: Waratkar et al., GCN 41926; IPN triangulation: Kozyrev et al., GCN 41940) triggered Konus-Wind at T0=10444.538 s UT (02:54:04.538). The burst light curve shows a multipeaked structure which starts at ~T0-1.1 s and has a total duration of ~12.5 s. The emission is seen up to ~15 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250920_T10444/ There are no data for the ~18-70 keV band in the triggered mode. As observed by Konus-Wind, the burst had the total fluence of 4.52(-0.15,+0.15)x10^-5 erg/cm2, and the 64-ms peak flux, measured from T0+1.984 s, of 4.06(-0.28,+0.28)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+18.432 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 = -0.84(-0.05,+0.05), the high energy photon index beta = -2.61(-0.09,+0.08), the peak energy Ep = 162(-6,+6) keV (chi2 = 106/97 dof). The spectrum near the maximum count rate (measured from T0+1.792 to T0+2.048 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 = -0.58(-0.09,+0.09), the high energy photon index beta = -2.46(-0.14,+0.11), the peak energy Ep = 332(-27,+31) keV (chi2 = 44/46 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/41941. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40006] IPN triangulation of GRB 250920A (long/bright)
by GCN Circulars 22 Sep '25

22 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41940 SUBJECT: IPN triangulation of GRB 250920A (long/bright) DATE: 25/09/22 16:39:14 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, 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 bright, long-duration GRB 250920A (Ferm-GBM detection: The Fermi GBM team, GCN 41895; Sonawane and Smith, GCN 41918; BALROG localization: Preis and Greiner, GCN 41896 AstroSat-CZTI detection: Harsha et al., GCN 41899; SVOM-GRM detection: Wang et al., GCN 41912; NuSTAR-detection: Waratkar et al., GCN 41926) was detected by Fermi (GBM trigger 780029651), SVOM (GRM), AstroSat (CZTI), NuSTAR, Konus-Wind, and Mars-Odyssey (HEND), at about 10447 s UT (02:54:07). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 176.909 (11h 47m 38s) +54.466 (+54d 27' 56") Corners: 177.868 (11h 51m 28s) +54.769 (+54d 46' 07") 177.751 (11h 51m 00s) +54.775 (+54d 46' 28") 175.963 (11h 43m 51s) +54.152 (+54d 09' 06") 176.079 (11h 44m 19s) +54.148 (+54d 08' 54") --------------------------------------------- The error box area is 168 sq. arcmin, and its maximum dimension is 1.27 deg (the minimum one is 2.3 arcmin). The Sun distance was 53 deg. This localization may be improved. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250920_T10444/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/41940. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40005] Konus-Wind detection of GRB 250911A
by GCN Circulars 22 Sep '25

22 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41939 SUBJECT: Konus-Wind detection of GRB 250911A DATE: 25/09/22 16:37:08 GMT FROM: Valentina Panteleeva at Ioffe Institute <panteleevav228(a)gmail.com> V. Panteleeva, 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 250911A (Swift-BAT detection: Klingler et al., GCN 41781; Palmer et al., GCN 41812; GECAM-B detection: Zhang et al., GCN 41813; Insight-HXMT detection: Wang et al., GCN 41827) triggered Konus-Wind at T0=05370.240 s UT (01:29:30.240). The burst light curve shows a multipeaked structure which starts at ~T0-2.3 s and has a total duration of ~57 s. The weak precursor that triggered Swift-BAT is seen at ~T0-100 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250911_T05370/ As observed by Konus-Wind, the burst had the total fluence of 4.54(-0.29,+0.30)x10^-5 erg/cm2, and the 64-ms peak flux, measured from T0+1.440 s, of 5.15(-0.88,+0.90)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+41.216 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 = -0.85(-0.11,+0.12), the high energy photon index beta = -2.58(-0.19,+0.14), the peak energy Ep = 196(-13,+14) keV (chi2 = 102/97 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+8.448 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 = -0.92(-0.11,+0.12), the high energy photon index beta = -2.44(-0.19,+0.14), the peak energy Ep = 257(-25,+26) keV (chi2 = 88/84 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/41939. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40004] GRB 250916A: Swift/UVOT Detection
by GCN Circulars 22 Sep '25

22 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41938 SUBJECT: GRB 250916A: Swift/UVOT Detection DATE: 25/09/22 15:32:00 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk> A. A. Breeveld (UCL-MSSL) and R. Caputo (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of the Fermi/GBM detected burst GRB 250916A 102120s after the trigger (Fermi GBM team, GCN Circ. 41839). The optical counterpart detected by Belkin et al., GCN Circ. 41847; Mohan et al., GCN Circ. 41858; Moskvitin et al., GCN Circ. 41859; Burkhonov et al., GCN Circ. 41860; de Ugarte Postigo et al., GCN Circ. 41863; Moskvitin et al., GCN Circ. 41870; Zheng and Filippenko, GCN Circ. 41873; Pankov et al., GCN Circ. 41892; Hall et al., GCN Circ. 41921 and Moskvitin et al., GCN Circ. 41934, is detected in the initial white and u-band UVOT exposures. Preliminary magnitudes and upper limit using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag u 102120 107275 968 20.5 ± 0.2 white 102446 102767 316 21.1 ± 0.3 v 102774 103051 273 >19.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.051 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/41938. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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