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

[vsnet-grb-info 39289] GRB 250805A: Swift detection of a burst
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41233 SUBJECT: GRB 250805A: Swift detection of a burst DATE: 25/08/05 06:26:15 GMT FROM: Elena Ambrosi at INAF-IASF <elena.ambrosi(a)inaf.it> E. Ambrosi (INAF-IASFPA), S. Dichiara (PSU), R. Gupta (NASA GSFC), K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 06:09:08 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250805A (trigger=1339848). The BAT on-board calculated location is RA, Dec 24.153, -81.406 which is RA(J2000) = 01h 36m 37s Dec(J2000) = -81d 24' 22" 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 30 sec. The peak count rate was ~1800 counts/sec (15-350 keV), at ~0 sec after the trigger. Due to an observing constraint, Swift will not slew until ~ 57 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is E. Ambrosi (elena.ambrosi AT inaf.it). 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/41233. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39288] Swift GRB250805.26: Global MASTER-Net observations report
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41232 SUBJECT: Swift GRB250805.26: Global MASTER-Net observations report DATE: 25/08/05 06:16:56 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 Swift GRB250805.26 (trigger No 1339848,01h 36m 36.72s , -81d 24m 21.6s, R=0.05) errorbox 18 sec after notice time and 44 sec after trigger time at 2025-08-05 06:09:52 UT, with upper limit up to 17.9 mag. The observations began at zenith distance = 53 deg. The sun altitude is -65.4 deg. The galactic latitude b = -36 deg., longitude l = 301 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2960226 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 49 | MASTER-OAFA | C | 10 | 17.6 | 65 | MASTER-OAFA | C | 10 | 17.6 | 87 | MASTER-OAFA | C | 20 | 17.9 | 113 | MASTER-OAFA | C | 20 | 17.9 | 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/41232. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39287] GRB 250804B: Tiled Swift observations
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41231 SUBJECT: GRB 250804B: Tiled Swift observations DATE: 25/08/05 02:51:01 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a series of observations, tiled on the sky, of the IPN GRB 250804B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/xrt_products/TILED_GRB00138 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. The probability of finding serendipitous sources, unrelated to the IPN event is high: any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41231. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39286] Fermi trigger No 776041355: Global MASTER-Net observations report
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41230 SUBJECT: Fermi trigger No 776041355: Global MASTER-Net observations report DATE: 25/08/05 00:31:08 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 GRB250804.96 (trigger No 776041355,00h 05m 28.80s , -68d 42m 00.0s, R=2.88) errorbox 53 sec after notice time and 373 sec after trigger time at 2025-08-04 23:08:44 UT, with upper limit up to 19.1 mag. Observations started at twilight. The observations began at zenith distance = 72 deg. The sun altitude is -14.6 deg. The galactic latitude b = -48 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=2959916 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 409 | 2025-08-04 23:08:44 | MASTER-OAFA | (23h 51m 05.63s , -70d 19m 26.1s) | C | 70 | 16.5 | 2917 | 2025-08-04 23:50:07 | MASTER-OAFA | (00h 04m 24.18s , -68d 52m 59.9s) | C | 120 | 18.3 | 3037 | 2025-08-04 23:50:07 | MASTER-OAFA | (00h 04m 24.18s , -68d 52m 59.9s) | C | 360 | 19.1 | Coadd 3043 | 2025-08-04 23:52:13 | MASTER-OAFA | (00h 04m 23.52s , -68d 52m 56.6s) | C | 120 | 18.4 | 3169 | 2025-08-04 23:54:19 | MASTER-OAFA | (00h 04m 22.77s , -68d 52m 54.6s) | C | 120 | 18.3 | 3296 | 2025-08-04 23:56:26 | MASTER-OAFA | (00h 04m 22.14s , -68d 52m 51.8s) | C | 120 | 18.0 | 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/41230. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39285] GRB 250804B: SVOM/GRM observation of a short burst
by GCN Circulars 04 Aug '25

04 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41229 SUBJECT: GRB 250804B: SVOM/GRM observation of a short burst DATE: 25/08/04 16:01:26 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Jean-Luc Atteia, Sebastien Guillot (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 250804B (SVOM trigger reference: sb25080401) at 2025-08-04T04:44:51.600 UTC (T0). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 0.37 +0.09/-0.15 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250804B.png The SVOM/GRM on-ground localization of this burst is (J2000): RA: 36.3 deg DEC: -42.1 deg Error: 4.3 deg (1sigma, statistical only) We caution that the calibration of SVOM/GRM is undergoing and this localization is subject to systematic errors. In addition, the position of this burst, as determined by GRM, is located at about 56 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. Nonetheless, the burst is seen (via analysis of X-band data) in the ECLAIRs data above 50 keV at the T0 given by GRM, likely through the ECLAIRs shielding. With this localization, the time-averaged spectrum from T0-0.5 to T0+0.4 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.78 +0.07/-0.08 and the cutoff energy, parameterized as Epeak, is 1650 +38/-28 keV. The event fluence (10-1000 keV) in this time interval is (2.63 +/-0.13)E-06 erg/cm^2. Thus GRB 250804B is consistent with Type II GRBs in the 'Amati' relation diagram, as shown at: https://www.bursthub.cn//admin/static/grb250804B_amati.png 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/41229. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39284] GRB 250804A: Fermi GBM Final Localization
by GCN Circulars 04 Aug '25

04 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41228 SUBJECT: GRB 250804A: Fermi GBM Final Localization DATE: 25/08/04 15:33:20 GMT FROM: rhamburg(a)usra.edu The Fermi GBM team reports the detection of a likely SHORT GRB. "At 11:38:03.48 UT on 04 August 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250804A (trigger 776000288/250804485). This trigger was initially classified as Below Horizon by the flight software, but is in fact a GRB. The on-ground calculated location, using the Fermi GBM trigger data, is RA = 114.09, Dec = 42.02 (J2000 degrees, equivalent to J2000 7h 36m, +42d 1'), with a statistical uncertainty of 19.32 degrees. The angle from the Fermi LAT boresight is 44 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250804485/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250804485/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250804485/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/41228. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39283] EP250802a: additional Liverpool Telescope upper limits
by GCN Circulars 04 Aug '25

04 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41227 SUBJECT: EP250802a: additional Liverpool Telescope upper limits DATE: 25/08/04 12:15:11 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris and N. R. Tanvir (U of Leicester) report on behalf of a larger collaboration: We observed the field of the X-ray transient EP250802a (Yin et al., GCN 41221) with the 2m Liverpool Telescope using the IO:O instrument. We obtained 8x150s exposures in each of the SDSS r’ and SDSS z’ filters starting at 2025-08-03 22:17:48 UT, approximately 35.7 hours after the X-ray detection. We performed image subtraction on the stacked images using reference images from Pan-STARRS and also compared the stacked and reference images manually. Similarly to Bochanek et al. (GCN 41224), the bright stars in the error region affected our subtractions, however, no new sources are detected in either the subtractions or stacked images. Our results are consistent with Mohan et al. (GCN 41222), Lipunov et al. (GCN 41223) and Bochanek et al. (GCN 41224). At the position of the X-ray source, we derive 3-sigma upper limits of r’ > 22.44 and z’ > 21.73 with photometry calibrated to Pan-STARRS and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/41227. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39282] EP250730a: SVOM/VT optical upper limit
by GCN Circulars 04 Aug '25

04 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41226 SUBJECT: EP250730a: SVOM/VT optical upper limit DATE: 25/08/04 09:37:30 GMT FROM: zhyao(a)bao.ac.cn Z. H. Yao, H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Y. N. Ma, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), B. T. Wang (YNAO) report on behalf of the SVOM/VT team. SVOM performed a Target of Opportunity observation of EP250730a detected by EP/WXT (Wang et al., GCN 41207). SVOM/VT began observing the field at 2025-07-31T10:36:57.506 UTC, 28.5 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. No uncataloged candidates were detected in our single or stacked images within the error box provided by EP/WXT (Wang et al., GCN 41207), the three sigma limits are: mid-time (UTC) | exposure time (s) | band | upper limit (AB) --------------------|-------------------------|------|----------------- 2025-07-31T11:47:09 | 19*100 | VT_B | 23.5 2025-07-31T11:47:09 | 19*100 | VT_R | 23.0 Our results are consistent with COLIBRÍ (Magnani et al., GCN 41209) and Global MASTER-Net (Lipunov et al., GCN 41210). The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre 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/41226. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39281] Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB
by GCN Circulars 04 Aug '25

04 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41225 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB DATE: 25/08/04 05:23:28 GMT FROM: sumanbala2210(a)gmail.com S. Bala (USRA) and V. Sharma (GSFC/UMBC) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 775945985/250803856 at 20:33:00.34 UT on 03 August 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to local particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/41225. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39280] EP250802a: Liverpool Telescope optical upper limits
by GCN Circulars 04 Aug '25

04 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41224 SUBJECT: EP250802a: Liverpool Telescope optical upper limits DATE: 25/08/04 01:27:27 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 the fast X-ray transient EP250802a (Yin et al., GCN 41221) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 4x120s exposures in the SDSS r’ and i’ filters starting at 2025-08-03 21:42:37 UT, approximately 35 hours after the trigger. The images were stacked, and their background was subtracted relative to Pan-STARRS-1 using PSF matching with the help of PSFEx. We do not detect any new object at the EP/WXT error region of the transient: the 3-sigma limiting magnitudes on the stacked images are r > 22.67 mag and i > 22.33 mag, in line with Mohan et al. (GCN 41222) and Lipunov et al. (GCN 41223). However, we note that there are a few bright, saturated stars inside the error region on our images, impacting the image subtraction. View this GCN Circular online at https://gcn.nasa.gov/circulars/41224. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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