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

[vsnet-grb-info 39847] GRB 250911A: Swift detection of a burst
by GCN Circulars 11 Sep '25

11 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41781 SUBJECT: GRB 250911A: Swift detection of a burst DATE: 25/09/11 01:43:39 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> N. J. Klingler (GSFC/UMBC/CRESSTII), S. Dichiara (PSU), R. Gupta (NASA GSFC), A. Y. Lien (U Tampa) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: At 01:27:46 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250911A (trigger=1348587). Due to an observing constraint Swift did not immediately slew to the burst. The BAT on-board calculated location is RA, Dec 263.762, -16.844 which is RA(J2000) = 17h 35m 03s Dec(J2000) = -16d 50' 36" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 20 sec. The peak count rate was ~1200 counts/sec (15-350 keV), at ~3 sec after the trigger. Due to an observing constraint, Swift will not slew until T0+50 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu) Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/41781. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39846] LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
by GCN Circulars 10 Sep '25

10 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41780 SUBJECT: LIGO/Virgo/KAGRA S250906ca: Updated Sky localization DATE: 25/09/10 19:56:00 GMT FROM: natalie.williams(a)uni-potsdam.de The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250906ca (GCN Circular 41745). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN and SCiMMA notices, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250906ca For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 516 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1121 +/- 266 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] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040 View this GCN Circular online at https://gcn.nasa.gov/circulars/41780. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39845] GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
by GCN Circulars 10 Sep '25

10 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41779 SUBJECT: GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786) DATE: 25/09/10 19:25:58 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 779223130 at 18:52:05 on 10 Sept. 2025 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 74.2 deg Decl.(2000.0) = -47.5 deg The 1 sigma statistical error radius is 3.6 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB250910786/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB250910786/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB250910786/json View this GCN Circular online at https://gcn.nasa.gov/circulars/41779. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39844] GRB 250910B: Fermi GBM Final Real-time Localization
by GCN Circulars 10 Sep '25

10 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41778 SUBJECT: GRB 250910B: Fermi GBM Final Real-time Localization DATE: 25/09/10 19:02:42 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 18:52:05 UT on 10 Sep 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250910B (trigger 779223130.045678 / 250910786). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 80.2, Dec = -46.4 (J2000 degrees, equivalent to J2000 05h 20m, -46d 23'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 35.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250910786/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250910786/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250910786/… View this GCN Circular online at https://gcn.nasa.gov/circulars/41778. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39843] GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
by GCN Circulars 10 Sep '25

10 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41777 SUBJECT: GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations DATE: 25/09/10 11:26:08 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> M. Garnichey (LUX-Paris Obs.), V. D'Elia (ASI-SSDC), B. Schneider (LAM), A. J. Levan (Radboud U.), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), A. L. Thakur (INAF-IAPS), S. D. Vergani (LUX-Paris Obs.) report on behalf the Stargate collaboration: We observed the field of GRB 250910A / EP250910a (Ma et al., GCN 41769; Götz et al. GCN 41770; Wu et al., GCN 41772; Li et al., GCN 41774; Liu et al., GCN 41776) using the ESO VLT UT4 (Yepun) equipped with the HAWK-I NIR camera. We obtained 15 min imaging in the J band, beginning on 2025-09-10 at 08:28 UT (5.2 hr post-trigger). Within the 20"-radius EP/FXT error circle (Liu et al., GCN 41776), several objects are visible in the stack of our data. All have an archival optical counterpart in the Legacy Survey (and they are thus not high-redshift candidates). Any of these sources could in principle contain an afterglow contribution, but a new template image is required to isolate any transient flux that might be present in our image. Further observations are planned with HAWK-I. We acknowledge excellent support from the ESO observing staff in Paranal, in particular Julien Drevon. View this GCN Circular online at https://gcn.nasa.gov/circulars/41777. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39842] EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
by GCN Circulars 10 Sep '25

10 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41776 SUBJECT: EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient DATE: 25/09/10 09:08:42 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Q. C. Liu (THU), H. N. Yang, H. W. Pan (NAO,CAS) on behalf of the Einstein Probe team: We report on the detection of a fast X-ray transient, designated EP250910a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient event started at 2025-09-10T03:16:04 (UTC). The position of the source is R.A. = 39.797 deg, DEC = -39.686 deg (J2000) with an uncertainty of 2.1 arcmin in radius (90% C.L. statistical and systematic). The trigger time and position of this X-ray transient are consistent with that of GRB 250910A (GCN 41769, GCN 41770). The 0.5-4 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 1.74 x 10^20 cm^-2 and a photon index of 0.8 (+0.3/-0.3) during the flare. The estimated unabsorbed 0.5-4 keV flux of the flare is 1.2 (+0.3/-0.2) x 10^(-9) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. The transient event lasts for 160 seconds. A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 39.8048 deg, DEC = -39.6966 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). 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/41776. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39841] GRB 250909B: AstroSat CZTI detection of a long burst
by GCN Circulars 10 Sep '25

10 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41775 SUBJECT: GRB 250909B: AstroSat CZTI detection of a long burst DATE: 25/09/10 08:58:31 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), S. Salunke (IUCAA), A. Arya (IITB), A. Goyal (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long and bright GRB 250909B which was also detected by Konus-Wind (IPN notices). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-09-09 17:49:11.50 UTC. The measured peak count rate associated with the burst is 701 (+50, -52) counts/s above the background in the combined data of all quadrants, with a total of 3971 (+218, -234) counts. The local mean background count rate was 282 (+4, -4) counts/s. Using cumulative rates, we measure a T90 of 10.1 (+0.9, -0.4) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-09-09 17:49:10.32 UTC. The measured peak count rate associated with the burst is 1432 (+86, -93) counts/s above the background in the combined data of all quadrants, with a total of 5850 (+337, -369) counts. The local mean background count rate was 1344 (+7, -8) counts/s. We measure a T90 of 9.4 (+0.5, -0.3) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/41775. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39840] GRB 250910A: SVOM/VT optical upper limit
by GCN Circulars 10 Sep '25

10 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41774 SUBJECT: GRB 250910A: SVOM/VT optical upper limit DATE: 25/09/10 08:53:25 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> H. L. Li, Y. N. Ma, Z. H. Yao, L. P. Xin, Y. L. Qiu, C. Wu, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei, D. H. Zhao (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM performed an automatic slew on the burst triggered by SVOM/ECLAIRs (Ma et al., GCN 41769). SVOM/VT began observing the field at 2025-09-10T04:00:48 UTC, 0.739 hours after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. No credible candidate was detected in our single or stacked images at the SVOM/MXT position (Götz et al., GCN 41770), the three sigma limits are: mid-time | exposure time (s) | band | upper limit (AB) ---------|-------------------|------|----------------- 1.08h | 16*50 | VT_B | 22.8 1.08h | 16*50 | VT_R | 23.3 Our results are consistent with LCO (Wu et al., GCN 41772). The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/41774. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39839] EP250908C: GROND observation of the fading optical counterpart
by GCN Circulars 10 Sep '25

10 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41773 SUBJECT: EP250908C: GROND observation of the fading optical counterpart DATE: 25/09/10 08:48:05 GMT FROM: Arne Rau at MPE <arau(a)mpe.mpg.de> Arne Rau (MPE) reports: We observed the position of EP250908C (Zhang et al., GCN 41754) using the Gamma-Ray burst Optical Near-infrared Detector (GROND, Greiner et al. 2008) mounted to the MPG 2.2m telescope at ESO’s La Silla Observatory on 2025-09-10 07:24 UT, i.e. 31.5 hours after the Einstein Probe trigger. The candidate optical counterpart reported by Malesani et al. (GCN 41760) was detected with r’= 23.0+/-0.2 i’ = 22.8+/-0.2 indicating clear fading. The magnitudes are in the AB magnitude system and calibrated against nearby SkyMapper sources. We acknowledge the excellent support of the 2.2m staff, in particular Angel Hempel. View this GCN Circular online at https://gcn.nasa.gov/circulars/41773. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39838] GRB 250910A: LCO optical upper limit
by GCN Circulars 10 Sep '25

10 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41772 SUBJECT: GRB 250910A: LCO optical upper limit DATE: 25/09/10 07:43:10 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C. Wu (NAOC), A. Saccardi (CEA/Irfu), L. P. Xin (NAOC), J. T. Palmerio (CEA/Irfu), B. Cordier (CEA/Irfu), Y. N. Ma (NAOC), D. Zhao (NAOC) report on behalf of the SVOM mission team: We observed the field of the GRB 250910A detected by SVOM/ECLAIRs (Ma et al., GCN 41769) with the LCO 1m telescope at Cerro Tololo Interamerican Observatory equipped with the Sinistro instrument. Our observation started on 2025-09-10 at 05:03:46 UT (~1.79 hr after the trigger) and we obtained 3x200 s exposures using the SDSS r filter. In the stacked image, we did not detect any new optical source at the SVOM/MXT position (Götz et al., GCN 41770). We derived the following upper limit r > 20.8 mag (5-sigma) calibrated using nearby stars from the UCAC4 catalog and not corrected for Galactic extinction. This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/41772. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0