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

[vsnet-grb-info 39332] EP 250807.979: COLIBRÍ optical upper limit
by GCN Circulars 08 Aug '25

08 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41275 SUBJECT: EP 250807.979: COLIBRÍ optical upper limit DATE: 25/08/08 06:07:18 GMT FROM: globus(a)astro.unam.mx Noémie Globus (UNAM), Francis Fortin (IRAP), Camila Angulo (UNAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (AUS), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Alvarez (UNAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the EP X-ray transient EP 250807.979 using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-08-08 04:38 to 04:57 UTC (from 5.12 to 5.44 hours after the trigger) and obtained 16 minutes of exposure in the i-band filter. The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source in the WXT uncertainty region, either in the direct image or after subtracting a Pan-STARRS DR2 template, down to the following 5-sigma limit: i > 21.67 We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/41275. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39331] GRB 250807A: SVOM/VT optical observation
by GCN Circulars 08 Aug '25

08 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41274 SUBJECT: GRB 250807A: SVOM/VT optical observation DATE: 25/08/08 03:38:37 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, Z. H. Yao, L. P. Xin, Y. L. Qiu, C. Wu, H. L. Li, 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 (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of GRB 250807A detected by Swift-BAT（Klingler et al., GCN 41262; Evans et al., GCN 41270). The observation began at 2025-08-07T11:21:39.516 UTC, 35.52 minutes after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical afterglow (Evans et al., GCN 41262) is detected in both VT_R and VT_B using VT X-band data at R.A. = 51.448126 , DEC = -47.887663 degrees: RA (J2000) = 3:25:47.55 Dec (J2000) = -47:53:15.58 with an uncertainty of 0.5 arcsec. The magnitudes are: mid time (sec) | exposure time (s) | band | mag (AB) | mag err ---------------|-------------------|------|----------|-------- 2236 | 70 | VT_B | 20.52 | 0.08 14319 | 70 | VT_B | 21.07 | 0.10 2236 | 70 | VT_R | 18.98 | 0.03 14319 | 70 | VT_R | 19.29 | 0.03 Our photometry was not corrected for Galactic extinction. During our observations, the light curves exhibit an initial brightening followed by a decay phase. 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/41274. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39330] EP250806a: Upper limit from Fermi-GBM Observations
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41273 SUBJECT: EP250806a: Upper limit from Fermi-GBM Observations DATE: 25/08/07 20:05:54 GMT FROM: mariaedvige.ravasio(a)ru.nl M. E. Ravasio and P.G. Jonker (Radboud Univ.) on behalf of the Einstein Probe Team and E. Burns (LSU) on behalf of the Fermi-GBM Team, report: Fermi-GBM had full spatial coverage of the transient EP250806a detected by EP-WXT (Yang et al., GCN 41246). There was no Fermi-GBM onboard trigger around the refined EP starting time T0=2025-08-06T09:17:30 UTC (Liang et al., GCN 41256). The GBM targeted search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [T0-50;T0+500] s, seeking signals between 64 ms and 32.768 s in duration. No signal consistent with the EP transient, both temporally and spatially, is identified, as confirmed also by visual inspection of the data. Assuming a “soft” spectral template (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7), and a duration of 8.192 s, we derive a flux upper limit of 3.7e-08 erg/cm2/s in the energy band 10-1000 keV. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/41273. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39329] GRB 250807B: Enhanced Swift-XRT position
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41272 SUBJECT: GRB 250807B: Enhanced Swift-XRT position DATE: 25/08/07 19:34:25 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 1712 s of XRT Photon Counting mode data and 5 UVOT images for GRB 250807B, 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 = 15.63710, -59.11896 which is equivalent to: RA (J2000): 01h 02m 32.90s Dec (J2000): -59d 07' 08.3" with an uncertainty of 2.4 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/41272. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39328] Swift GRB250807.65: Global MASTER-Net observations report
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41271 SUBJECT: Swift GRB250807.65: Global MASTER-Net observations report DATE: 25/08/07 18:44:25 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB250807.65 (trigger No 1340561,01h 02m 20.40s , -59d 05m 38.4s, R=0.05) errorbox 10317 sec after notice time and 10401 sec after trigger time at 2025-08-07 18:36:29 UT, with upper limit up to 17.8 mag. The observations began at zenith distance = 76 deg. The sun altitude is -32.1 deg. The galactic latitude b = -58 deg., longitude l = 300 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2963168 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 10491 | MASTER-SAAO | C | 180 | 17.1 | 10491 | MASTER-SAAO | C | 180 | 17.8 | 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/41271. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39327] GRB 250807A: Enhanced Swift-XRT position
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41270 SUBJECT: GRB 250807A: Enhanced Swift-XRT position DATE: 25/08/07 16:14:45 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 769 s of XRT Photon Counting mode data and 3 UVOT images for GRB 250807A, 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 = 51.44795, -47.88761 which is equivalent to: RA (J2000): 03h 25m 47.51s Dec (J2000): -47d 53' 15.4" with an uncertainty of 2.0 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/41270. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39326] IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41269 SUBJECT: IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/08/07 16:04:49 GMT FROM: Alicia Mand at IceCube/UW-Madison <aemand(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-Cascade 250804A (https://gcn.nasa.gov/circulars/41235) in a time range of 1000 seconds centered on the alert event time (2025-08-04 07:50:12.960 UTC to 2025-08-04 08:06:52.960 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-Cascade 250804A. We report a p-value of 1.00 in this time window. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-Cascade 250804A ranges from 1.4e-01 to 1.7e+01 GeV cm^-2 in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 3e+02 GeV and 4e+06 GeV. A subsequent search was performed, including 2 days of data centered on the alert event time (2025-08-03 07:58:32.960 UTC to 2025-08-05 07:58:32.960 UTC). In this case, we report a p-value of 0.43, consistent with no significant excess of track events. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-Cascade 250804A ranges from 1.6e-01 to 1.7e+01 GeV cm^-2 in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/41269. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39325] GRB 250807B: Swift detection of a burst with an optical counterpart.
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41268 SUBJECT: GRB 250807B: Swift detection of a burst with an optical counterpart. DATE: 25/08/07 15:59:34 GMT FROM: noelklin(a)umbc.edu N. J. Klingler (GSFC/UMBC/CRESSTII), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU), S. Dichiara (PSU), R. Gupta (NASA GSFC), S. Lanava (PSU), M. J. Moss (GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), C. Salvaggio (INAF-OAB) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 15:43:07 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250807B (trigger=1340561). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 15.585, -59.094 which is RA(J2000) = 01h 02m 21s Dec(J2000) = -59d 05' 37" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows complex activity during the slew that immediately preceded this trigger, with a total observed duration of about 100 sec. The peak count rate was ~1200 counts/sec (15-350 keV), at ~15 sec after the trigger. The XRT began observing the field at 15:45:32.3 UT, 144.5 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 15.6378, -59.1186 which is equivalent to: RA(J2000) = 01h 02m 33.07s Dec(J2000) = -59d 07' 07.0" with an uncertainty of 5.6 arcseconds (radius, 90% containment). This location is 131 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. UVOT took a finding chart exposure of 150 seconds with the White filter starting 153 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 01:02:32.98 = 15.63741 DEC(J2000) = -59:07:07.9 = -59.11887 with a 90%-confidence error radius of about 0.75 arc sec. This position is 1.2 arc sec. from the center of the XRT error circle. The estimated magnitude is 16.31 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.016. 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/41268. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39324] GRB 250805A: Kilonova-Catcher optical upper limits
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41267 SUBJECT: GRB 250805A: Kilonova-Catcher optical upper limits DATE: 25/08/07 15:27:58 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> P. Jaquiery, R. Hellot (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), M. Pillas (ULiege), S. Antier (OCA/IJCLAB) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 250805A (Ambrosi et al., GCN 41233) detected by Swift/BAT with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with a Celestron C14 telescope located at Beverly-Begg Observatory and operated by P. Jaquiery and the CDK17 telescope located at AITP San Pedro Chile Observatory operated by R. Hellot. Our observations started at T0+1.2hr. In our stacked frames, subtracted from the Legacy Survey DR10 template image, we do not detect any optical counterpart inside the Swift/XRT position (Kennea et al., GCN 41234; Beardmore et al., GCN 41238) and at the position of the optical afterglow candidate reported by the VLT/X-shooter (Izzo et al., GCN 41241) and SVOM/VT (Li et al., GCN 41242) teams. We report our follow-up results in the table below: +---------------+-----------+------------+----------------------+-------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+===========+============+======================+=============+ | 1.9 | 28 x 120s | sdssr (AB) | 18.3 (U.L., 5 sigma) | C14-BBO | | 26.1 | 5 x 600s | sdssr (AB) | 19.5 (U.L., 5 sigma) | CDK17-AITP | +---------------+-----------+------------+----------------------+-------------+ These upper limits are compatible with the magnitudes and upper limits reported by (Liu et al., GCN 41236; Izzo et al., GCN 41241; Li et al., GCN 41242; Siegel et al., GCN 41265) All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the sloan filters were calibrated using the SkyMapper DR4 catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/). View this GCN Circular online at https://gcn.nasa.gov/circulars/41267. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39323] EP250806a:SVOM/VT refined analysis
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41266 SUBJECT: EP250806a:SVOM/VT refined analysis DATE: 25/08/07 14:41:19 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L. P. Xin, H. L. Li, Y. N. Ma, Y. L. Qiu, C. Wu, Z. H. Yao, 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) report on behalf of the SVOM/VT team. After the refined analysis, the candidate reported (Xin et al., GCN 41254) was a cataloged source in Legacy survey, not an uncatalogued source, as reported by Becerra et al., (GCN 41255). No any candidates were found in VT images within EP/FXT errorbox (Yang et al., GCN 41246; Liang et al., GCN 41256), the 3 sigma limit is about VT_B~23.6 mag and VT_R~23.1 mag in AB mag at 8.19 hours after the EP/WXT trigger. The results are consistent with the reports (Fortin et al. GCN 41248; Becerra et al., GCN 41255; Lipunov et al., GCN 41258; Kumar et al., GCN 41263). 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/41266. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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