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

[vsnet-grb-info 40494] GRB 251022A: Swift-XRT detection of GOTO25iym
by GCN Circulars 24 Oct '25

24 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42417 SUBJECT: GRB 251022A: Swift-XRT detection of GOTO25iym DATE: 25/10/24 08:12:16 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Capalbi (INAF-OAR), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 251022A in a series of observations tiled on the sky. The total exposure time is 4.6 ks, distributed over 4 tiles; the maximum exposure at a single sky location in the tiling was 2.5 ks. The data were collected between T0+26.7 ks and T0+71.7 ks, and are entirely in Photon Counting (PC) mode. Seven uncatalogued X-ray sources have been detected, however none of them is above the RASS limit or shows definitive signs of fading in the X-rays. Source 4 is 2.6 arcsec from the reported optical transient GOTO25iym (O'Neill et al., GCN Circ. 42386) and thus is likely the counterpart to that transient and the GRB afterglow, though we cannot at present confirm fading in X-rays. The details of this source are: Source 4: RA (J2000.0): 65.4968 = 04h 21m 59.23s Dec (J2000.0): -18.9188 = -18d 55' 07.8" Error: 4.8 arcsec (radius, 90% conf.) Count-rate: 0.0110 [+0.0026, -0.0025] ct s^-1 Distance: 1463 arcsec from Fermi/LAT position. Flux: (2.96 [+0.71, -0.67])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) The other 6 uncatalogued sources detected are enumerated below: Source 1: RA (J2000.0): 65.0135 = 04h 20m 03.25s Dec (J2000.0): -19.3306 = -19d 19' 50.1" Error: 6.3 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: 0.0173 [+0.0061, -0.0050] ct s^-1 Distance: 1247 arcsec from Fermi/LAT position. Flux: (3.5 [+1.2, -1.0])e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 2: RA (J2000.0): 65.0984 = 04h 20m 23.62s Dec (J2000.0): -19.2625 = -19d 15' 45.2" Error: 5.4 arcsec (radius, 90% conf.) Count-rate: 0.0115 [+0.0046, -0.0037] ct s^-1 Distance: 971 arcsec from Fermi/LAT position. Flux: (4.4 [+1.8, -1.4])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 5: RA (J2000.0): 65.3796 = 04h 21m 31.10s Dec (J2000.0): -18.9857 = -18d 59' 08.4" Error: 6.0 arcsec (radius, 90% conf.) Count-rate: (7.7 [+2.6, -2.1])e-3 ct s^-1 Distance: 1167 arcsec from Fermi/LAT position. Flux: (2.17 [+0.72, -0.60])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 6: RA (J2000.0): 65.5456 = 04h 22m 10.93s Dec (J2000.0): -19.1086 = -19d 06' 30.8" Error: 6.5 arcsec (radius, 90% conf.) Count-rate: (6.0 [+2.5, -2.0])e-3 ct s^-1 Distance: 917 arcsec from Fermi/LAT position. Flux: (9.1 [+3.9, -3.0])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 8: RA (J2000.0): 65.4382 = 04h 21m 45.16s Dec (J2000.0): -19.0268 = -19d 01' 36.6" Error: 7.8 arcsec (radius, 90% conf.) Count-rate: (3.2 [+1.8, -1.3])e-3 ct s^-1 Distance: 1038 arcsec from Fermi/LAT position. Flux: (6.8 [+3.9, -2.8])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 9: RA (J2000.0): 65.3956 = 04h 21m 34.95s Dec (J2000.0): -19.0576 = -19d 03' 27.4" Error: 6.3 arcsec (radius, 90% conf.) Count-rate: (3.6 [+2.1, -1.5])e-3 ct s^-1 Distance: 910 arcsec from Fermi/LAT position. Flux: (1.15 [+0.65, -0.48])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Two catalogued sources were also detected. The results of the XRT-team automatic analysis of the tiled XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00139. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42417. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40493] EP251023b: Global MASTER-Net observations report
by GCN Circulars 24 Oct '25

24 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42416 SUBJECT: EP251023b: Global MASTER-Net observations report DATE: 25/10/24 06:18:23 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 (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the EP251023b ( EP Team et al., GCN 42415) errorbox 40434 sec after trigger time at 2025-10-23 20:02:41 UT, with upper limit up to 20.1 mag. The observations began at zenith distance = 38 deg. The sun altitude is -34.7 deg. The galactic latitude b = -18 deg., longitude l = 187 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3022366 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 40494 | 2025-10-23 20:02:41 | MASTER-Tunka | (04h 53m 57.12s , +12d 53m 42.1s) | C | 120 | 16.4 | 40494 | 2025-10-23 20:02:41 | MASTER- | (04h 53m 27.18s , +12d 59m 22.7s) | C | 120 | 18.8 | 40627 | 2025-10-23 20:04:54 | MASTER- | (04h 53m 23.22s , +13d 00m 50.4s) | C | 120 | 19.8 | 40628 | 2025-10-23 20:04:54 | MASTER-Tunka | (04h 53m 53.26s , +12d 55m 10.3s) | C | 120 | 16.4 | 40761 | 2025-10-23 20:07:07 | MASTER-Tunka | (04h 53m 53.45s , +12d 53m 31.3s) | C | 120 | 16.9 | 40761 | 2025-10-23 20:07:07 | MASTER- | (04h 53m 23.36s , +12d 59m 11.7s) | C | 120 | 19.9 | 41086 | 2025-10-23 20:13:02 | MASTER-Tunka | (04h 53m 57.11s , +12d 54m 43.4s) | C | 60 | 19.7 | 41176 | 2025-10-23 20:13:02 | MASTER-Tunka | (04h 53m 57.11s , +12d 54m 43.3s) | C | 240 | 20.0 | Coadd 41086 | 2025-10-23 20:13:02 | MASTER- | (04h 53m 26.63s , +13d 00m 28.7s) | C | 60 | 19.7 | 41159 | 2025-10-23 20:14:15 | MASTER-Tunka | (04h 53m 50.19s , +12d 54m 07.5s) | C | 60 | 19.7 | 41159 | 2025-10-23 20:14:15 | MASTER- | (04h 53m 19.72s , +12d 59m 52.6s) | C | 60 | 19.7 | 41263 | 2025-10-23 20:15:30 | MASTER-Tunka | (04h 53m 51.71s , +12d 55m 04.5s) | C | 120 | 19.8 | 41263 | 2025-10-23 20:15:30 | MASTER- | (04h 53m 21.21s , +13d 00m 49.4s) | C | 120 | 19.8 | 41398 | 2025-10-23 20:17:44 | MASTER-Tunka | (04h 53m 57.01s , +12d 54m 00.3s) | C | 120 | 19.8 | 41518 | 2025-10-23 20:17:44 | MASTER-Tunka | (04h 53m 57.02s , +12d 54m 00.4s) | C | 360 | 20.0 | Coadd 41398 | 2025-10-23 20:17:44 | MASTER- | (04h 53m 26.46s , +12d 59m 45.2s) | C | 120 | 19.8 | 41530 | 2025-10-23 20:19:57 | MASTER-Tunka | (04h 53m 50.71s , +12d 52m 55.2s) | C | 120 | 19.7 | 41530 | 2025-10-23 20:19:57 | MASTER- | (04h 53m 20.15s , +12d 58m 40.0s) | C | 120 | 19.7 | 41663 | 2025-10-23 20:22:10 | MASTER-Tunka | (04h 53m 57.82s , +12d 53m 08.0s) | C | 120 | 19.7 | 41663 | 2025-10-23 20:22:10 | MASTER- | (04h 53m 27.32s , +12d 58m 52.6s) | C | 120 | 19.7 | 41796 | 2025-10-23 20:24:22 | MASTER-Tunka | (04h 53m 54.06s , +12d 54m 19.5s) | C | 120 | 19.7 | 41916 | 2025-10-23 20:24:22 | MASTER-Tunka | (04h 53m 54.06s , +12d 54m 19.5s) | C | 360 | 20.1 | Coadd 41796 | 2025-10-23 20:24:22 | MASTER- | (04h 53m 23.57s , +13d 00m 03.9s) | C | 120 | 19.6 | 41929 | 2025-10-23 20:26:35 | MASTER-Tunka | (04h 53m 54.16s , +12d 52m 58.5s) | C | 120 | 19.8 | 41929 | 2025-10-23 20:26:35 | MASTER- | (04h 53m 23.66s , +12d 58m 43.0s) | C | 120 | 19.8 | 42062 | 2025-10-23 20:28:48 | MASTER-Tunka | (04h 53m 57.79s , +12d 54m 17.4s) | C | 120 | 19.9 | 42062 | 2025-10-23 20:28:48 | MASTER- | (04h 53m 27.25s , +13d 00m 01.6s) | C | 120 | 19.9 | 42195 | 2025-10-23 20:31:02 | MASTER-Tunka | (04h 53m 52.11s , +12d 53m 34.1s) | C | 120 | 19.9 | 42315 | 2025-10-23 20:31:02 | MASTER-Tunka | (04h 53m 52.11s , +12d 53m 34.1s) | C | 360 | 20.1 | Coadd 42195 | 2025-10-23 20:31:02 | MASTER- | (04h 53m 21.54s , +12d 59m 18.5s) | C | 120 | 19.9 | 42327 | 2025-10-23 20:33:13 | MASTER-Tunka | (04h 53m 50.56s , +12d 54m 30.9s) | C | 120 | 20.0 | 42327 | 2025-10-23 20:33:13 | MASTER- | (04h 53m 19.95s , +13d 00m 15.1s) | C | 120 | 19.9 | 42460 | 2025-10-23 20:35:27 | MASTER-Tunka | (04h 53m 57.26s , +12d 53m 27.1s) | C | 120 | 19.9 | 42460 | 2025-10-23 20:35:27 | MASTER- | (04h 53m 26.58s , +12d 59m 11.0s) | C | 120 | 19.9 | 42595 | 2025-10-23 20:37:41 | MASTER-Tunka | (04h 53m 52.25s , +12d 52m 22.4s) | C | 120 | 19.9 | 42685 | 2025-10-23 20:37:41 | MASTER-Tunka | (04h 53m 52.25s , +12d 52m 22.4s) | C | 300 | 20.1 | Coadd 42595 | 2025-10-23 20:37:41 | MASTER- | (04h 53m 21.54s , +12d 58m 06.1s) | C | 120 | 19.9 | 42730 | 2025-10-23 20:39:56 | MASTER-Tunka | (04h 53m 57.37s , +12d 52m 45.8s) | C | 120 | 20.0 | 42730 | 2025-10-23 20:39:56 | MASTER- | (04h 53m 26.63s , +12d 58m 29.3s) | C | 120 | 20.0 | 42833 | 2025-10-23 20:42:09 | MASTER-Tunka | (04h 53m 54.47s , +12d 53m 48.3s) | C | 60 | 19.9 | 42833 | 2025-10-23 20:42:09 | MASTER- | (04h 53m 23.67s , +12d 59m 31.7s) | C | 60 | 19.9 | 42907 | 2025-10-23 20:43:24 | MASTER-Tunka | (04h 53m 54.53s , +12d 52m 27.5s) | C | 60 | 19.8 | 42967 | 2025-10-23 20:43:24 | MASTER-Tunka | (04h 53m 54.54s , +12d 52m 27.5s) | C | 180 | 20.0 | Coadd 42907 | 2025-10-23 20:43:24 | MASTER- | (04h 53m 23.70s , +12d 58m 10.7s) | C | 60 | 19.8 | 42980 | 2025-10-23 20:44:36 | MASTER-Tunka | (04h 53m 56.90s , +12d 54m 01.3s) | C | 60 | 19.7 | 42980 | 2025-10-23 20:44:36 | MASTER- | (04h 53m 26.04s , +12d 59m 44.2s) | C | 60 | 19.7 | 43052 | 2025-10-23 20:45:49 | MASTER-Tunka | (04h 53m 52.30s , +12d 53m 09.6s) | C | 60 | 19.5 | 43052 | 2025-10-23 20:45:49 | MASTER- | (04h 53m 21.42s , +12d 58m 52.8s) | C | 60 | 19.5 | 43134 | 2025-10-23 20:47:11 | MASTER-Tunka | (04h 53m 51.00s , +12d 54m 07.5s) | C | 60 | 19.2 | 43194 | 2025-10-23 20:47:11 | MASTER-Tunka | (04h 53m 50.99s , +12d 54m 07.5s) | C | 180 | 19.7 | Coadd 43135 | 2025-10-23 20:47:11 | MASTER- | (04h 53m 20.10s , +12d 59m 50.4s) | C | 60 | 19.1 | 43208 | 2025-10-23 20:48:25 | MASTER-Tunka | (04h 53m 58.03s , +12d 53m 05.4s) | C | 60 | 19.2 | 43208 | 2025-10-23 20:48:25 | MASTER- | (04h 53m 27.12s , +12d 58m 48.7s) | C | 60 | 19.1 | 43284 | 2025-10-23 20:49:41 | MASTER-Tunka | (04h 53m 50.96s , +12d 52m 02.9s) | C | 60 | 19.0 | 43284 | 2025-10-23 20:49:41 | MASTER- | (04h 53m 20.05s , +12d 57m 45.8s) | C | 60 | 19.0 | 43358 | 2025-10-23 20:50:54 | MASTER-Tunka | (04h 53m 58.58s , +12d 52m 08.7s) | C | 60 | 18.8 | 43418 | 2025-10-23 20:50:54 | MASTER-Tunka | (04h 53m 58.58s , +12d 52m 08.7s) | C | 180 | 19.3 | Coadd 43358 | 2025-10-23 20:50:54 | MASTER- | (04h 53m 27.65s , +12d 57m 51.3s) | C | 60 | 18.7 | 43435 | 2025-10-23 20:52:12 | MASTER-Tunka | (04h 53m 54.73s , +12d 53m 32.9s) | C | 60 | 18.7 | 43435 | 2025-10-23 20:52:12 | MASTER- | (04h 53m 23.76s , +12d 59m 15.7s) | C | 60 | 18.7 | 43507 | 2025-10-23 20:53:24 | MASTER-Tunka | (04h 53m 54.77s , +12d 52m 13.3s) | C | 60 | 18.3 | 43507 | 2025-10-23 20:53:24 | MASTER- | (04h 53m 23.79s , +12d 57m 56.2s) | C | 60 | 18.2 | 43579 | 2025-10-23 20:54:36 | MASTER-Tunka | (04h 53m 57.61s , +12d 53m 34.0s) | C | 60 | 18.7 | 43639 | 2025-10-23 20:54:36 | MASTER-Tunka | (04h 53m 57.62s , +12d 53m 34.0s) | C | 180 | 19.9 | Coadd 43579 | 2025-10-23 20:54:36 | MASTER- | (04h 53m 26.61s , +12d 59m 16.6s) | C | 60 | 18.7 | 43654 | 2025-10-23 20:55:50 | MASTER-Tunka | (04h 53m 52.49s , +12d 52m 52.2s) | C | 60 | 19.6 | 43654 | 2025-10-23 20:55:50 | MASTER- | (04h 53m 21.48s , +12d 58m 34.6s) | C | 60 | 19.5 | 43727 | 2025-10-23 20:57:04 | MASTER-Tunka | (04h 53m 51.37s , +12d 53m 50.1s) | C | 60 | 19.5 | 43727 | 2025-10-23 20:57:04 | MASTER- | (04h 53m 20.37s , +12d 59m 32.4s) | C | 60 | 19.4 | 43800 | 2025-10-23 20:58:16 | MASTER-Tunka | (04h 53m 57.11s , +12d 52m 48.1s) | C | 60 | 19.6 | 43890 | 2025-10-23 20:58:16 | MASTER-Tunka | (04h 53m 57.11s , +12d 52m 48.2s) | C | 240 | 20.0 | Coadd 43800 | 2025-10-23 20:58:16 | MASTER- | (04h 53m 26.13s , +12d 58m 30.3s) | C | 60 | 19.6 | 43873 | 2025-10-23 20:59:30 | MASTER-Tunka | (04h 53m 52.86s , +12d 51m 46.0s) | C | 60 | 19.6 | 43873 | 2025-10-23 20:59:30 | MASTER- | (04h 53m 21.87s , +12d 57m 27.9s) | C | 60 | 19.5 | 43984 | 2025-10-23 21:00:51 | MASTER-Tunka | (04h 53m 58.73s , +12d 51m 48.7s) | C | 120 | 19.2 | 43984 | 2025-10-23 21:00:51 | MASTER- | (04h 53m 27.73s , +12d 57m 30.8s) | C | 120 | 19.2 | 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/42416. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40492] EP251023b/GRB 251023B : Einstein Probe detection of a fast X-ray transient
by GCN Circulars 24 Oct '25

24 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42415 SUBJECT: EP251023b/GRB 251023B : Einstein Probe detection of a fast X-ray transient DATE: 25/10/24 05:39:45 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. Wu (NJU), D. F. Hu (PMO, CAS), H. N. Yang, T. Zhao, W. D. Zhang (NAO, CAS), on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251023b. The transient triggered EP-WXT (ID: 01709247298) at 2025-10-23T08:48:47 (UTC). The refined analysis of the WXT data shows that the event started at T0=2025-10-23T08:46:06 (UTC) and lasted for ~160 s. The WXT position of the source is R.A. = 73.502 deg, Dec. = 12.648 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 2.69 x 10^(21) cm^-2 and a photon index of 1.66（-/+0.25）. The derived average unabsorbed 0.5-4 keV flux is 3.9 (-/+0.5) x 10^(-9) erg/s/cm^2. We performed a Target-of-Opportunity observation with the Follow-up X-ray Telescope on board EP. The observation began at 2025-10-23T14:40:06 (UTC).An uncatalogued X-ray source was detected within the WXT error circle at R.A. = 73.5021 deg, Dec. = 12.6574 deg (J2000), with a positional uncertainty of 10 arcsec in radius (90% confidence level, including both statistical and systematic uncertainties). The FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with the same fixed Galactic hydrogen column density value and a photon index of 2.16 (-/+0.21). The derived average unabsorbed 0.5-10 keV flux is 2.03 (-0.29/+0.34) x 10^(-12) erg/s/cm^2. The source is spatially consistent with the counterpart reported (Kang et al. GCN 42392, Evans et al. GCN 42401, Nakahira et al. GCN 42402, Mandarakas et al. GCN 42404, Cheung et al. GCN 42407). 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/42415. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40491] GRB 251023C: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 24 Oct '25

24 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42414 SUBJECT: GRB 251023C: CALET Gamma-Ray Burst Monitor detection DATE: 25/10/24 04:00:02 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> Y. Asaoka (ICRR), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), 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 251023C (Swift/BAT-GUANO localization skymap: DeLaunay et al., GCN Circ 42412) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 16:24:24.93 UTC on 23 October 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1445271383/index.html). The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure that starts at T+1.9 sec, peaks at T+3.7 sec, and ends at T+23.4 sec. The T90 and T50 durations measured by the SGM data are 18.7 +/- 1.4 sec and 5.7 +/- 0.8 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1445271383/ 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/42414. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40490] GRB 251022A: GROWTH-India Telescope optical observations
by GCN Circulars 24 Oct '25

24 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42413 SUBJECT: GRB 251022A: GROWTH-India Telescope optical observations DATE: 25/10/24 01:01:59 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> T. Mohan, V. Swain, A.P. Saikia, 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 251022A (Fermi GBM team, GCN 42380), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2025-10-23 22:25:05 UT, i.e., 23.85 hours after the Fermi trigger. Multiple exposures were obtained in the r'-band, and we clearly detect the optical counterpart in the stacked image. The photometry result follows as: | MJD (mid) | tmid - t0 (hours) | Filter | Exposure (s) | Magnitude (AB) | | --------- | ----------------- | ------ | ------------ | -------------- | |60971.94474| 24.1 | r' | 5 x 360 | 20.89 +- 0.12 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Our magnitude is consistent with other optical observations (O’Neill et al., GCN 42386; Becerra et al., GCN 42394; Lipunov et al., GCN 42395; Mandarakas et al., GCN 42397). The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree 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/42413. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40489] GRB 251023C: Swift/BAT-GUANO localization skymap of a burst
by GCN Circulars 24 Oct '25

24 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42412 SUBJECT: GRB 251023C: Swift/BAT-GUANO localization skymap of a burst DATE: 25/10/24 00:54:24 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Samuele Ronchini (GSSI), Aaron Tohuvavohu (Caltech), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (Northwestern) report: Swift/BAT did not localize GRB 251023C onboard (T0: 2025-10-23T16:24:24.92 UTC, CALET Trig 1445271383) The CALET notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 90 seconds of BAT event-mode data from [-45,+45] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 26.0 in a 8.192 s analysis time bin, starting at T0 + 2.048 s. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 1,100 deg2 and the 50% credible area is 229 deg2. The integrated probability inside the coded field of view is <1%. A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=782929501/#:~:te… The probability skymap file can be downloaded from the link here [skymap_fits_file](https://guano.swift.psu.edu/files/782929501/0_n_PROBMAP) Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=782929501 GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/42412. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40488] EP251023a: GROWTH-India Telescope optical observations
by GCN Circulars 24 Oct '25

24 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42411 SUBJECT: EP251023a: GROWTH-India Telescope optical observations DATE: 25/10/24 00:12:04 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> T. Mohan (IITB), D. Eappachen (IIA), V. Swain (IITB), A.P. Saikia (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of EP transient EP251023a (Wu et al., GCN 42388), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2025-10-23 20:05:36 UT, i.e., 17.57 hours after the EP trigger. We obtained multiple exposures in g', r', and i' filters. We detect the optical afterglow in our stacked images, at the position reported by GOTO (Wortley et al., GCN 42387). The photometry result follows as: | MJD (mid) | tmid - t0 (hours) | Filter | Exposure (s) | Magnitude (AB) | | --------- | ----------------- | ------ | ------------ | -------------- | |60971.87998| 18.60 | r' | 5 x 360 | 20.39+-0.09 | |60971.90145| 19.12 | i' | 5 x 360 | 20.24+-0.11 | |60971.92296| 19.63 | g' | 5 x 360 | 20.88+-0.10 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Our magnitude is consistent with other optical observations (Wortley et al., GCN 42387; Li et al., GCN 42389; Liu et al., GCN 42391; Mandarakas et al., GCN 42400; Lipunov et al., GCN 42405; Selezneva et al., GCN 42406). The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree 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/42411. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40487] GRB 251022A: Fermi GBM Observation
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42410 SUBJECT: GRB 251022A: Fermi GBM Observation DATE: 25/10/23 22:45:23 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 22:34:15.26 UT on 22 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251022A (trigger 782865260/251022940) which was also detected by Fermi-LAT ( N. Di Lalla et al. 2025, GCN 42384), MASTER OT (V. Lipunov et al. 2025, GCN 42395), and Swift/BAT-GUANO (James DeLaunay et al. 2025, GCN 42409). The Fermi GBM on-ground location is consistent with the Fermi-LAT position. The angle from the Fermi LAT boresight is 36.5 degrees. The GBM light curve consists of multiple emission episodes with a duration (T90) of about 99.6 s (50-300 keV). The time-averaged spectrum from T0-1 to T0+107.5 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.88 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 154 +/- 5 keV. The event fluence (10-1000 keV) in this time interval is (2.16 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+100 s in the 10-1000 keV band is 12.4 +/- 0.3 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 138 +/- 7 keV, alpha = -0.8 +/- 0.05 and beta = -2.6 +/- 0.2. 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/42410. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40486] GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42409 SUBJECT: GRB 251022A: Swift/BAT-GUANO localization skymap of a burst DATE: 25/10/23 20:18:12 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Samuele Ronchini (GSSI), Aaron Tohuvavohu (Caltech), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (Northwestern) report: Swift/BAT did not localize GRB 251022A onboard (T0: 2025-10-22T22:34:45.26 UTC, Fermi Trig 782865260) The Fermi notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+50 s], detects the burst with a sqrt(TS) of 26.2 in a 2.048 s analysis time bin, starting at T0 + 32.560 s. The main peak was outside the typical search window of [T0-20 s, T0+20 s], so we expanded it in this case. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 2,100 deg2 and the 50% credible area is 380 deg2. The integrated probability inside the coded field of view is <1%. The NITRATES skymap is consistent with the Fermi localization reported in the final position notice (GCN 42380). The combined Fermi/GBM+NITRATES 90% credible area is 111 deg2 and the 50% credible area is 29 deg2. The NITRATES and combined Fermi/GBM+NITRATES skymaps are consistent with the Fermi/LAT (GCN 42384) and optical afterglow positions (GOTO GCN 42386, DDOTI GCN 42394, MASTER GCN 42395). A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=782865321/#:~:te… The probability skymap and joint skymap files can be downloaded from the links here [skymap_fits_file](https://guano.swift.psu.edu/files/782865321/0_n_PROBMAP) [joint_skymap_fits_file](https://guano.swift.psu.edu/files/782865321/0_n_JOI… Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=782865321 GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/42409. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40485] GRB 251023A: Glowbug gamma-ray detection
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42408 SUBJECT: GRB 251023A: Glowbug gamma-ray detection DATE: 25/10/23 20:15:38 GMT FROM: 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 251023A, which was also detected by Fermi/GBM (GCN 42385). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-23 05:57:43.480 with a duration of 4.1 s and a total significance of about 9.1 sigma. The light curve comprises a single peak. Note that data from ~T0-1s to T0+1s suffered from deadtime in various 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/42408. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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vsnet-grb-info October 2025