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

[vsnet-grb-info 39823] The EP-WXT trigger EP250908a/01709240652 is not a real source
by GCN Circulars 09 Sep '25

09 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41757 SUBJECT: The EP-WXT trigger EP250908a/01709240652 is not a real source DATE: 25/09/09 03:14:28 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> C. Zhou (HUST), Y. H. Cheng (SWIFAR, YNU), S. L. Wang (YNU), T. Y. Liu, H. Q. Cheng, C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe (EP) team The EP-WXT trigger EP250908a/01709240652 at the time of 2025-09-08T15:43:42 is not a real source based on ground data analysis. View this GCN Circular online at https://gcn.nasa.gov/circulars/41757. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39822] EP250908c: Global MASTER-Net observations report
by GCN Circulars 09 Sep '25

09 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41756 SUBJECT: EP250908c: Global MASTER-Net observations report DATE: 25/09/09 03:01:15 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) was pointed to the EP250908c ( EP Team et al., GCN 41754) errorbox 385 sec after trigger time at 2025-09-08 23:57:19 UT, with upper limit up to 19.4 mag. The observations began at zenith distance = 66 deg. The sun altitude is -21.0 deg. The galactic latitude b = -67 deg., longitude l = 309 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2987645 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 426 | 2025-09-08 23:57:19 | MASTER-OAFA | (00h 32m 33.78s , -50d 34m 25.0s) | C | 80 | 19.4 | 517 | 2025-09-08 23:58:46 | MASTER-OAFA | (00h 32m 33.61s , -50d 34m 21.6s) | C | 90 | 19.4 | 623 | 2025-09-09 00:00:22 | MASTER-OAFA | (00h 32m 33.35s , -50d 34m 18.6s) | C | 110 | 19.4 | 704 | 2025-09-09 00:02:17 | MASTER-OAFA | (00h 32m 33.16s , -50d 34m 16.5s) | C | 40 | 19.0 | 750 | 2025-09-09 00:03:03 | MASTER-OAFA | (00h 32m 33.01s , -50d 34m 15.4s) | C | 40 | 19.0 | 795 | 2025-09-09 00:03:49 | MASTER-OAFA | (00h 32m 32.90s , -50d 34m 14.1s) | C | 40 | 19.0 | 842 | 2025-09-09 00:04:35 | MASTER-OAFA | (00h 32m 32.81s , -50d 34m 12.7s) | C | 40 | 18.9 | 887 | 2025-09-09 00:05:20 | MASTER-OAFA | (00h 32m 32.71s , -50d 34m 11.3s) | C | 40 | 19.0 | 932 | 2025-09-09 00:06:06 | MASTER-OAFA | (00h 32m 32.57s , -50d 34m 10.1s) | C | 40 | 19.0 | 978 | 2025-09-09 00:06:51 | MASTER-OAFA | (00h 32m 32.42s , -50d 34m 09.1s) | C | 40 | 19.0 | 1023 | 2025-09-09 00:07:37 | MASTER-OAFA | (00h 32m 32.31s , -50d 34m 08.0s) | C | 40 | 18.9 | 1069 | 2025-09-09 00:08:23 | MASTER-OAFA | (00h 32m 32.23s , -50d 34m 06.6s) | C | 40 | 18.9 | 1116 | 2025-09-09 00:09:09 | MASTER-OAFA | (00h 32m 32.14s , -50d 34m 05.4s) | C | 40 | 18.9 | 1161 | 2025-09-09 00:09:55 | MASTER-OAFA | (00h 32m 32.02s , -50d 34m 04.0s) | C | 40 | 18.9 | 1207 | 2025-09-09 00:10:40 | MASTER-OAFA | (00h 32m 31.90s , -50d 34m 03.0s) | C | 40 | 19.0 | 1253 | 2025-09-09 00:11:26 | MASTER-OAFA | (00h 32m 31.80s , -50d 34m 01.9s) | C | 40 | 19.0 | 1298 | 2025-09-09 00:12:12 | MASTER-OAFA | (00h 32m 31.67s , -50d 34m 01.1s) | C | 40 | 18.9 | 1344 | 2025-09-09 00:12:57 | MASTER-OAFA | (00h 32m 31.57s , -50d 33m 59.7s) | C | 40 | 18.9 | 1390 | 2025-09-09 00:13:43 | MASTER-OAFA | (00h 32m 31.45s , -50d 33m 58.3s) | C | 40 | 19.0 | 1436 | 2025-09-09 00:14:29 | MASTER-OAFA | (00h 32m 31.33s , -50d 33m 57.1s) | C | 40 | 18.9 | 1481 | 2025-09-09 00:15:15 | MASTER-OAFA | (00h 32m 31.23s , -50d 33m 56.1s) | C | 40 | 19.0 | 1528 | 2025-09-09 00:16:01 | MASTER-OAFA | (00h 32m 31.11s , -50d 33m 54.9s) | C | 40 | 18.9 | 1573 | 2025-09-09 00:16:46 | MASTER-OAFA | (00h 32m 31.00s , -50d 33m 53.6s) | C | 40 | 18.9 | 1618 | 2025-09-09 00:17:32 | MASTER-OAFA | (00h 32m 30.90s , -50d 33m 52.2s) | C | 40 | 18.8 | 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/41756. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39821] Fermi GRB 250909A: Global MASTER-Net observations report
by GCN Circulars 09 Sep '25

09 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41755 SUBJECT: Fermi GRB 250909A: Global MASTER-Net observations report DATE: 25/09/09 02:45:32 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-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 250909A ( Fermi GBM team, GCN 41753) errorbox 31 sec after notice time and 68 sec after trigger time at 2025-09-09 02:34:37 UT, with upper limit up to 15.3 mag. Observations started at twilight. The observations began at zenith distance = 17 deg. The sun altitude is -7.8 deg. The galactic latitude b = 1 deg., longitude l = 168 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2987637 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 74 | 2025-09-09 02:34:37 | MASTER-Tavrida | (05h 35m 20.66s , +41d 15m 12.7s) | C | 10 | 14.4 | 91 | 2025-09-09 02:34:50 | MASTER-Tavrida | (05h 35m 20.96s , +41d 15m 12.4s) | C | 20 | 15.1 | 124 | 2025-09-09 02:35:22 | MASTER-Tavrida | (05h 23m 43.51s , +41d 45m 12.1s) | C | 20 | 15.2 | 154 | 2025-09-09 02:35:22 | MASTER-Tavrida | (05h 23m 43.50s , +41d 45m 12.1s) | C | 80 | 15.3 | Coadd 199 | 2025-09-09 02:35:22 | MASTER-Tavrida | (05h 23m 43.51s , +41d 45m 12.2s) | C | 170 | 15.3 | Coadd 152 | 2025-09-09 02:35:45 | MASTER-Tavrida | (05h 23m 43.26s , +41d 45m 11.6s) | C | 30 | 15.0 | 184 | 2025-09-09 02:36:17 | MASTER-Tavrida | (05h 23m 43.04s , +41d 45m 10.9s) | C | 30 | 14.6 | 221 | 2025-09-09 02:36:50 | MASTER-Tavrida | (05h 23m 42.76s , +41d 45m 10.4s) | C | 40 | 15.1 | 276 | 2025-09-09 02:36:50 | MASTER-Tavrida | (05h 23m 42.74s , +41d 45m 10.4s) | C | 150 | 14.7 | Coadd 269 | 2025-09-09 02:37:32 | MASTER-Tavrida | (05h 23m 42.35s , +41d 45m 09.7s) | C | 50 | 15.1 | 327 | 2025-09-09 02:38:25 | MASTER-Tavrida | (05h 23m 41.85s , +41d 45m 08.4s) | C | 60 | 14.7 | 395 | 2025-09-09 02:39:28 | MASTER-Tavrida | (05h 23m 41.29s , +41d 45m 06.9s) | C | 70 | 14.5 | 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/41755. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39820] EP250908c: Einstein Probe detection of an X-ray transient
by GCN Circulars 09 Sep '25

09 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41754 SUBJECT: EP250908c: Einstein Probe detection of an X-ray transient DATE: 25/09/09 02:45:12 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> M. H. Zhang, M. J. Liu (NAO, CAS), Y.-H. I. Yin (NJU), X. X. Sun, T. Y. Liu, H. Y. Ren, H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250908c. The transient triggered EP-WXT (ID: 01709240659) at 2025-09-08T23:50:54 (UTC). The WXT position of the source is R.A. = 8.226 deg, DEC = -50.447 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 8.2170 deg, DEC = -50.4633 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. 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/41754. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39819] GRB 250909A: Fermi GBM Final Real-time Localization
by GCN Circulars 09 Sep '25

09 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41753 SUBJECT: GRB 250909A: Fermi GBM Final Real-time Localization DATE: 25/09/09 02:43:59 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 02:33:28 UT on 9 Sep 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250909A (trigger 779078013.882702 / 250909107). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 78.8, Dec = 39.5 (J2000 degrees, equivalent to J2000 05h 15m, 39d 30'), with a statistical uncertainty of 3.3 degrees. The angle from the Fermi LAT boresight is 85.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250909107/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250909107/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250909107/… View this GCN Circular online at https://gcn.nasa.gov/circulars/41753. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39818] EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
by GCN Circulars 09 Sep '25

09 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41752 SUBJECT: EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation DATE: 25/09/09 02:42:35 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (NJU), M. H. Zhang, M. J. Liu, X. X. Sun, T. Y. Liu, H. Y. Ren, H. Sun (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 EP250908b. The transient triggered EP-WXT (ID: 01709240653) at 2025-09-08T18:26:19 (UTC). The WXT position of the source is R.A. = 297.534 deg, DEC = -57.505 deg (J2000) with an uncertainty of 2.5 arcmin in radius (90% C.L. statistical and systematic). The WXT data shows that the event started at T0=2025-09-08T18:26:08 (UTC) and lasted for about 13 s before the interruption of the autonomous follow-up. The WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a hydrogen column density of 1.59 x 10^21 cm^-2 and a photon index of 1.14 (-0.45/+0.45). The derived peak unabsorbed 0.5-4 keV flux is 8.14 (-1.60/+2.00) x 10^-9 erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously about 164s after T0. On-ground analysis of the FXT data found a fading uncatalogued source at R.A. = 297.4784, DEC = -57.4938 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), within the WXT error circle. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a hydrogen column density of 1.59 (-0.76/+0.76) x 10^21 cm^-2 and a photon index of 2.02 (-0.23/+0.23). The derived average unabsorbed 0.5-10 keV flux is 1.10 (-0.09/+0.09) x 10^-12 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. 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/41752. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39817] EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
by GCN Circulars 08 Sep '25

08 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41751 SUBJECT: EP#01709240652 (possibly EP250908a): FTW optical and NIR observations DATE: 25/09/08 23:54:00 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann(a)physik.lmu.de> Malte Busmann (LMU), Xander Hall (Carnegie Mellon U.), Brendan O’Connor (Carnegie Mellon U.), Daniel Gruen (LMU), and Antonella Palmese (Carnegie Mellon U.) report: We observed the 90% localization of EP/WXT trigger 01709240652 (possibly EP250908a) for 10 x 180 s in the r, i, and J-band simultaneously with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW). Our observations started at 2025-09-08T21:33:56 (0.23 days after trigger). We performed difference imaging with i-band templates from PS1 and J-band templates from UKIDSS. We do not detect any new sources in the difference images. The mean 3-sigma depth of our J band difference is J > 20.4 AB mag, calibrated against the 2MASS catalog and not corrected for Galactic extinction. We thank Michael Schmidt from the Wendelstein Observatory for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/41751. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39816] LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
by GCN Circulars 08 Sep '25

08 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41750 SUBJECT: LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate DATE: 25/09/08 15:54:52 GMT FROM: Mayara Hilgert Pacheco at LIGO <mayara.pacheco(a)inpe.br> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250908y during real-time processing of data from LIGO Hanford Observatory (H1) and Virgo Observatory (V1) at 2025-09-08 14:34:28.958 UTC (GPS time: 1441377286.958). The candidate was found by the GstLAL [1] analysis pipeline. S250908y is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.1e-10 Hz, or about one in 1e2 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250908y The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass (HasNS) is <1%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [2] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. The source chirp mass falls with highest probability in the bin (5.5, 11.0) solar masses, assuming the candidate is astrophysical in origin. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [3], distributed via GCN and SCiMMA notices about 45 minutes after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [3], distributed via GCN and SCiMMA notices about 50 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is 11002 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1280 +/- 403 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. PRD 109, 042008 (2024) doi:10.1103/PhysRevD.109.042008 [2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [3] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/41750. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39815] GRB 250907A: GECAM-B detection
by GCN Circulars 08 Sep '25

08 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41749 SUBJECT: GRB 250907A: GECAM-B detection DATE: 25/09/08 15:18:41 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by a bright long burst GRB 250907A at 2025-09-07T22:00:52.850 UTC (denoted as T0), which is also detected by Konus-Wind. According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 36.5 +0.5/-3.0 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb250907A.png GECAM-B localized this burst to the following position (J2000): Ra: 337.2 deg Dec: -9.0 deg Err: 1.3 deg (1-sigma, statistical only) The time-averaged spectrum from T0-5 s to T0+40 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.08 +0.14/-0.12 and the cutoff energy, parameterized as Epeak, is 535 +192/-129 keV. The event fluence (10-1000 keV) in this time interval is (7.57 +0.51/-0.61)E-05 erg/cm^2. The 'Amati' relation diagram of GRB 250907A is shown at: https://www.bursthub.cn//admin/static/gecambgrb250907A_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/41749. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39814] GRB 250905A: Swift-BAT refined analysis
by GCN Circulars 08 Sep '25

08 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41748 SUBJECT: GRB 250905A: Swift-BAT refined analysis DATE: 25/09/08 15:16:06 GMT FROM: D. R. Sadaula at NASA GSFC <dev.r.sadaula(a)nasa.gov> T. Parsotan (GSFC), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250905A (trigger #1347265) (Brivio, et al., GCN Circ. 41714). The BAT ground-calculated position is RA, Dec = 232.943, 0.789 deg which is RA(J2000) = 15h 31m 46.3s Dec(J2000) = +00d 47' 19.6" with an uncertainty of 3.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 74%. The BAT light curve showed a complex structure with multiple peaks. The burst lasted about 70 sec. T90 (15-350 keV) is 48.00 +- 50.60 sec (estimated error including systematics). The time-averaged spectrum from T-15.10 to T+64.89 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.65 +- 0.67. The fluence in the 15-150 keV band is 4.1 +- 1.4 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+8.40 sec in the 15-150 keV band is 0.27 +- 0.16 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1347265 View this GCN Circular online at https://gcn.nasa.gov/circulars/41748. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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