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

[vsnet-grb-info 39793] EP250905a: Global MASTER-Net observations report
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41727 SUBJECT: EP250905a: Global MASTER-Net observations report DATE: 25/09/05 18:09:28 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP250905a ( EP Team et al., GCN 41725) errorbox 18309 sec after notice time and 24012 sec after trigger time at 2025-09-05 17:52:01 UT, with upper limit up to 17.2 mag. The observations began at zenith distance = 51 deg. The sun altitude is -23.2 deg. The galactic latitude b = -25 deg., longitude l = 116 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2985447 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 24043 | 2025-09-05 17:52:01 | MASTER-Kislovodsk | (00h 16m 34.13s , +37d 41m 06.2s) | C | 60 | 17.2 | 24633 | 2025-09-05 18:01:52 | MASTER-Kislovodsk | (00h 16m 32.36s , +37d 38m 50.7s) | C | 60 | 17.2 | 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/41727. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39792] GRB 250901A - SVOM/ECLAIRs refined analysis
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41726 SUBJECT: GRB 250901A - SVOM/ECLAIRs refined analysis DATE: 25/09/05 13:34:45 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Tais Maiolino (LUPM), Frédéric Piron (LUPM), Claire Guépin-Detrigne (LUPM) Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 250901A (SVOM burst-id sb25090101). The burst that triggered ECLAIRs (GCN #41634) consists of a single pulse structure with a duration of T90 = 16 +1/-3 s in the 4-120 keV energy band. The time-averaged spectrum from T0-8 s to T0+10 s (T0 = 2025-09-01T18:14:22.916) in the energy range 5-120 keV is best fitted by a power-law model with photon index -1.15 +/- 0.09. With this model, the 4-120 keV fluence is (1.4 +/- 0.1) e-06 erg/cm^2. All the quoted errors are at the 68% confidence level. We note that the calibration of SVOM/ECLAIRs is undergoing thus these results are preliminary The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Tais Maiolino (LUPM) (tais.maiolino at lupm.in2p3.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/41726. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39791] EP250905a: Einstein Probe detection of an X-ray transient
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41725 SUBJECT: EP250905a: Einstein Probe detection of an X-ray transient DATE: 25/09/05 12:44:26 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.H. Cheng (SWIFAR,YNU), Y. Wang (PMO), R. D. Liang, W. D. Zhang (NAOC) 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 EP250905a. The transient triggered EP-WXT (ID: 01709201261) at 2025-09-05T11:11:49 (UTC). The WXT position of the source is R.A. = 4.441 deg, DEC = 37.493 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. = 4.4517 deg, DEC = 37.4728 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 are 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/41725. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39790] GRB 250905B: Fermi GBM Final Localization
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41724 SUBJECT: GRB 250905B: Fermi GBM Final Localization DATE: 25/09/05 11:17:13 GMT FROM: A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca(a)unitn.it> The Fermi GBM team reports the detection of a likely LONG GRB "At 08:14:40.87 UT on 05 September 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250905B (trigger 778752885/250905344). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 123.82, Dec = -19.65 (J2000 degrees, equivalent to J2000 8h 15m, -19d 38'), with a statistical uncertainty of 11.91 degrees. The angle from the Fermi LAT boresight is 90 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250905344/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250905344/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250905344/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/41724. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39789] GRB250904A: Liverpool Telescope upper limits
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41723 SUBJECT: GRB250904A: Liverpool Telescope upper limits DATE: 25/09/05 11:14:38 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek and D. A. Perley (LJMU) report: We observed the field of GRB250904A (Salvaggio et al., GCN 41704) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 4x120s exposures in the SDSS i’ filter starting at 2025-09-05 05:47:54 UT, approximately 12.2 hours after the trigger. We do not detect the reported optical counterpart (Fu et al., GCN 41709; Oates et al., GCN 41721) or any new source near the XRT position (Evans et al., GCN 41706; Goad et al., GCN 41711). The 3-sigma limiting magnitude on the stacked images is i > 22.4 mag. View this GCN Circular online at https://gcn.nasa.gov/circulars/41723. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39788] GRB 250905A: Enhanced Swift-XRT position
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41722 SUBJECT: GRB 250905A: Enhanced Swift-XRT position DATE: 25/09/05 10:52:49 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 233 s of XRT Photon Counting mode data and 1 UVOT images for GRB 250905A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 233.00557, +0.79370 which is equivalent to: RA (J2000): 15h 32m 01.34s Dec (J2000): +00d 47' 37.3" with an uncertainty of 2.5 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41722. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39787] GRB 250904A: Swift/UVOT Detection
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41721 SUBJECT: GRB 250904A: Swift/UVOT Detection DATE: 25/09/05 10:09:45 GMT FROM: Samantha Oates at University of Birmingham <samantha.oates(a)alumni.ucl.ac.uk> S. R. Oates (Lancaster Uni.) and C. Salvaggio (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250904A 86 s after the BAT trigger (Salvaggio et al., GCN Circ. 41704). A source consistent with the XRT position (Goad et al., GCN Circ. 41711) is detected in white and marginally in u. Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag/3sigUL white (FC) 86 235 147 20.23+\-0.36 u (FC) 298 441 141 19.14+\-0.41 (2.7 sigma) white 4990 10603 1097 20.60+\-0.16 v 5401 5601 197 >19.5 b 4786 6421 393 >20.4 u 6016 6215 197 >19.6 uvw1 5811 6011 197 >19.5 uvm2 5606 5806 197 >19.4 uvw2 5196 10942 524 >20.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.284 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/41721. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39786] GRB 250903A: Swift/UVOT detection
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41720 SUBJECT: GRB 250903A: Swift/UVOT detection DATE: 25/09/05 09:51:33 GMT FROM: s.shilling(a)lancaster.ac.uk S. P. R. Shilling (Lancaster U.) reports on behalf of the Swift/UVOT team: Swift/UVOT has performed follow-up observations of the SVOM/ECLAIRs-detected source GRB 250903A. Swift/UVOT observed the field of GRB 250903A (Maiolino et al., GCN 41677) for 2.3 ks in the U-band starting at 20:57:46 UT, 3.5 hours after the detection by SVOM/ECLAIRs. A source consistent with the TRT optical counterpart position (An et al., GCN 41679), within the SVOM/ECLAIRs error circle, is detected and is fading. The preliminary detection magnitude reported below is calculated using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373). Filter T_start(s) T_stop(s) Exp(s) Mag u 12770 24862 2330 19.71 +/- 0.11 View this GCN Circular online at https://gcn.nasa.gov/circulars/41720. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39785] GRB 250904A: Swift-XRT refined Analysis
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41719 SUBJECT: GRB 250904A: Swift-XRT refined Analysis DATE: 25/09/05 09:20:44 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne (U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , S. Lanava (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 7.0 ks of XRT data for GRB 250904A, from 66 s to 45.6 ks after the trigger. The data comprise 9 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a power-law decay with a decay index of alpha=0.85 (+0.05, -0.04). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.05 (+0.27, -0.25). The best-fitting absorption column is 4.4 (+1.4, -1.0) x 10^21 cm^-2, consistent with the Galactic value of 3.3 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.0 x 10^-11 (6.5 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 4.4 (+1.4, -1.0) x 10^21 cm^-2 Galactic foreground: 3.3 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 2.05 (+0.27, -0.25) If the light curve continues to decay with a power-law decay index of 0.85, the count rate at T+24 hours will be 7.0 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x 10^-13 (4.5 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01347179. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41719. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39784] LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41718 SUBJECT: LIGO/Virgo/KAGRA S250904cv: Updated Sky localization DATE: 25/09/05 08:02:39 GMT FROM: Michael J. Williams at University of Portsmouth <michael.williams(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) data around the time of the compact binary merger (CBC) candidate S250904cv (GCN Circular 41700). 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/S250904cv For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 980 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1806 +/- 595 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/41718. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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