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

[vsnet-grb-info 39686] EP250831a: Global MASTER-Net observations report
by GCN Circulars 31 Aug '25

31 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41621 SUBJECT: EP250831a: Global MASTER-Net observations report DATE: 25/08/31 21:09:50 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 EP250831a ( EP Team et al., GCN 41619) errorbox 21491 sec after notice time and 40170 sec after trigger time at 2025-08-31 20:58:42 UT, with upper limit up to 18.8 mag. The observations began at zenith distance = 70 deg. The sun altitude is -56.9 deg. The galactic latitude b = -63 deg., longitude l = 239 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2980777 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 40201 | 2025-08-31 20:58:42 | MASTER-SAAO | (02h 50m 10.03s , -36d 31m 25.6s) | C | 60 | 18.8 | 40201 | 2025-08-31 20:58:42 | MASTER-SAAO | (02h 48m 03.66s , -36d 15m 35.6s) | C | 60 | 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/41621. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39685] IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 31 Aug '25

31 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41620 SUBJECT: IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/08/31 20:44:36 GMT FROM: Erik Blaufuss at University of Maryland, College Park <blaufuss(a)umd.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2025-08-31 18:00:45.82 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_Bronze alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 2.14 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/141300_5972385.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2025-08-31 Time: 18:00:45.82 UT RA: 105.64 (+0.51, -0.48 deg 90% PSF containment) J2000 Dec: 5.04 (+0.61, -0.50 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event. 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 View this GCN Circular online at https://gcn.nasa.gov/circulars/41620. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39684] EP250831a: EP-WXT detection of a fast X-ray transient
by GCN Circulars 31 Aug '25

31 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41619 SUBJECT: EP250831a: EP-WXT detection of a fast X-ray transient DATE: 25/08/31 15:00:03 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J.Yang (ZZU), X. Tian (GXU), D. Y. Li, Y. Liu (NAO, CAS) report 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 EP250831a (trigger ID: 11916651030). The WXT position of the source is R.A. = 42.951 deg, DEC = -36.175 deg (J2000) with an uncertainty of 2.9 arcmin in radius (90% C.L. statistical and systematic). The transient started at 2025-08-31T09:49:12 (UTC) and lasted for about 300 seconds seen from the WXT light curve. The 0.5-4 keV spectrum can be fitted with an absorbed powerlaw model with Galactic hydrogen column density fixed to 1.9x10^20 cm^-2 and a photon index of 1.07(-0.49, +0.52). The average unabsorbed 0.5-4 keV flux is approximately 1.4 x 10^-10 erg/s/cm^2. The peak flux is estimated to be 6.8 x 10^-10 erg/s/cm^2. Follow-up observations with the Follow-up X-ray Telescope (FXT) on board EP have been scheduled, and further information will be updated when the telemetry data 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/41619. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39683] GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
by GCN Circulars 31 Aug '25

31 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41618 SUBJECT: GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61 DATE: 25/08/31 13:56:49 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> W.J. Xie, L. Lan, L.P. Xin (NAOC), Francesco Magnani (CPPM), D. B. Malesani (DAWN/NBI and Radboud) report on behalf of the SVOM mission team: At 2025-08-31T09:29:33 UTC SVOM issued an alert with burst-id sb25083102, which was previously referred to as GRB 250831A (Xie et al., GCN 41614). We found that there are several X-ray sources within the error box of ECLAIRs, including the high proper motion star G 272-61 (distance: 2.7 pc). This source was also noticed by Wu et al., (GCN 41615) in VT and Magnani et al. (GCN 41616) in COLIBRÍ (FM-GFT) images. Considering the proper motion of the source and the distance from the MXT localization (Xie et al., GCN 41614) and the XRT position (Evans et al., GCN 41617), we proposed that this SVOM trigger originated from an X-ray outburst of this star, and not an extragalactic GRB. We apologize for any inconvenience this may have caused. 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. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is: Wenjin XIE (xiewj(a)bao.ac.cn) Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/41618. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39682] GRB 250831A: Swift-XRT counterpart detection
by GCN Circulars 31 Aug '25

31 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41617 SUBJECT: GRB 250831A: Swift-XRT counterpart detection DATE: 25/08/31 13:40:52 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected source GRB 250831A (trigger sb25083102), collecting 1.5 ks of Photon Counting (PC) mode data between T0+3.0 ks and T0+4.7 ks after the trigger. A likely counterpart has been found. The details of this source are: Source 1 (SWIFT J013907.0-175644): ================================== RA (J2000.0): 24.7795 = 01 39 07.08 Dec (J2000.0): -17.9457 = -17 56 44.5 Error: 3.5 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 3.4 arcmin from the SVOM/ECLAIRs position. Mean rate: 5.60 +/- 0.16 ct s^-1 Mean flux: (1.571 +/- 0.046)e-10 erg cm^-2 s^-1 Peak rate: 9.9 +/- 2.2 ct s^-1 Peak flux: (2.78 +/- 0.61)e-10 erg cm^-2 s^-1 ECF: 2.81e-11 erg cm^-2 ct^-1 assuming NH=1.22e+21 cm^-2, gamma=2.40 determined from a spectral fit. LSXPS UL: 6.6e-03 ct/sec, (0.3-10 keV) so the source is 4.6-sigma above this 3-sigma upper limit. There is no evidence for fading. GCN Circs. 41615 and 41616 noted that the high-proper-motion M-dwarf binary star system G 272-61 was within the SVOM field of view; with a proper motion of ~3.3 arcsec yr^-1, its position appears consistent with this XRT source. We have detected a total of 3 sources. These have been automatically classified as follows: * 1 likely counterpart * 0 candidate counterparts * 1 uncatalogued X-ray source * 1 known X-ray source Uncatalogued X-ray sources -------------------------- Source 2 (SWIFT J013909.3-175732): ================================== RA (J2000.0): 24.7888 = 01 39 09.31 Dec (J2000.0): -17.9590 = -17 57 32.4 Error: 5.4 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 3.2 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.242 +/- 0.015 ct s^-1 Mean flux: (6.73 +/- 0.42)e-12 erg cm^-2 s^-1 Peak rate: 0.392 +/- 0.082 ct s^-1 Peak flux: (1.09 +/- 0.23)e-11 erg cm^-2 s^-1 ECF: 2.78e-11 erg cm^-2 ct^-1 assuming NH=8.33e+20 cm^-2, gamma=2.42 determined from a spectral fit. LSXPS UL: 5.7e-04 ct/sec, (0.3-10 keV) so the source is 4.8-sigma above this 3-sigma upper limit. There is no evidence for fading. Known X-ray sources ------------------- Source 3 (SWIFT J013932.8-175532): ================================== RA (J2000.0): 24.8869 = 01 39 32.86 Dec (J2000.0): -17.9257 = -17 55 32.5 Error: 8.1 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 2.9 arcmin from the SVOM/ECLAIRs position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-2.2 +/- -2.2)e-24 erg cm^-2 s^-1 Peak rate: (3.0 [+2.2, -1.6])e-3 ct s^-1 Peak flux: (6.6 [+4.9, -3.7])e-27 erg cm^-2 s^-1 ECF: 2.24e-24 erg cm^-2 ct^-1 assuming NH=3.77e+20 cm^-2, gamma=98.61 determined from a spectral fit. This matches a catalogued X-ray source LSXPS J013933.3-175540 in the LSXPS catalogue. Details: Separation: 10.3" from the XRT source Cat Rate: 9.9e-04 +/- 2.4e-04 ct s^-1 Cat Flux: 2.2e-27 +/- 5.5e-28 erg cm^-2 s^-1 (0.3-10 keV) so the source is 1.0-sigma above the catalogued flux. There is no evidence for fading. A SIMBAD object `SDSS J013934.38-175541.9' is 23.8" away. There are 2 2MASS objects within the source's 3-sigma error radius. All fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/SVOM/SVOM_FIELD00032. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41617. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39681] GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 31 Aug '25

31 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41616 SUBJECT: GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 25/08/31 12:59:04 GMT FROM: Francesco at Aix-Marseille Université, CPPM/CNRS <francesco.magnani.work(a)gmail.com> Francesco Magnani (CPPM), Alan M. Watson (UNAM), Benjamin Schneider (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Antonio de Ugarte Postigo (LAM), W.J. Xie, L. Lan (NAOC): We imaged the field of the SVOM GRB 250831A (W.J. Xie et al., GCN Circ. 41614) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-08-31T09:37:56 to 2025-08-31T11:43:45 UTC (from 8.4 to 134.2 minutes after the trigger) and obtained 88 minutes of exposure in the i and z filters. The data were reduced and coadded with the COLIBRÍ pipeline and analyzed 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 at the MXT source position (W.J. Xie et al., GCN Circ. 41614) down to the following 5-sigma limit: i > 23.5 We notice the presence of a bright star, G 272-61, within the MXT field of view (position in agreement with a proper motion of approximately 3.3 arcsec / year). 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/41616. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39680] GRB 250831A: SVOM/VT upper limit with VHF data
by GCN Circulars 31 Aug '25

31 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41615 SUBJECT: GRB 250831A: SVOM/VT upper limit with VHF data DATE: 25/08/31 11:12:25 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> C. Wu, L.P. Xin, Y. L. Qiu, H.L. Li, Z.H. Yao, Y.N. Ma, X.H. Han, J. Wang, W.J. Xie, Y. Xu, H.B. Cai, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM team. SVOM/VT performed an automatic slew on the burst triggered by SVOM/ECLAIRs (Xie et al., GCN 41614). SVOM/VT began observing the field automatically at 2025-08-31T09:35:46.00 UTC, 523 seconds after the T0, with the slew of the platform triggered on-board, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With downlinked VHF data, no any uncatalogued sources were found in stacked images within the errorbox of SVOM/MXT (Xie et al., GCN 41614) compared to Legacy survey. The 3 sigma limit in AB magnitude was derived as follows: --------------------------------------------------------- (T-T0)_mid exptime Band upperlim (3sigma) 523 sec 300 sec VT_R 21.5 mag We noticed that there is a very bright cataloged M type binary (G 272-61) near the MXT position, which is saturated in VT images. Its position is RA=24.75605 and D.E.=-17.95056 in J2000. More follow-ups are encouraged to investigate the nature of the burst. 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/41615. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39679] GRB 250831A: SVOM detection of a soft burst
by GCN Circulars 31 Aug '25

31 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41614 SUBJECT: GRB 250831A: SVOM detection of a soft burst DATE: 25/08/31 10:30:46 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> W.J. Xie, L. Lan (NAOC), S. Guillot, O. Godet (IRAP), M. Moita (CEA), L. Zhang (IHEP) report on behalf of the SVOM mission team: At 2025-08-31T09:29:33 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 250831A (SVOM burst-id sb25083102). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced a sequence of 3 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 9.21 in the [5-20] keV energy band over a time window of 163.84 seconds starting at 2025-08-31T09:28:52. The localization of the best alert is R.A., Dec. 24.8358, -17.9289 degrees (J2000) with a 90% confidence level (C.L.) radius of 8.60 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. SVOM/MXT began observing the field at 2025-08-31T09:33:53 UTC, 260 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 24.7771, -17.9379 degrees: R.A. (J2000) = 1h39m07.44s Dec. (J2000) = -17d56m31.2s with a 90% C.L. radius of 28.7 arcseconds (systematic and statistical). This location is 3.39 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the data will be published in a future circular. 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. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is : Wenjin XIE (xiewj(a)bao.ac.cn) Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/41614. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39678] GRB 250830B: Swift-XRT observations
by GCN Circulars 31 Aug '25

31 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41613 SUBJECT: GRB 250830B: Swift-XRT observations DATE: 25/08/31 04:57:05 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), S. Lanava (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the MAXI-detected burst GRB 250830B, collecting 2.4 ks of Photon Counting (PC) mode data between T0+11.0 ks and T0+50.8 ks. This event also triggered Einstein Probe around 25 s after MAXI, and was separately designated EP250830a. One uncatalogued X-ray source has been detected within the estimated 3-sigma EP error region (296 arcsec), also consistent with the MAXI error region; it is below the RASS limit and shows no definitive signs of fading. Therefore, at the present time we cannot confirm this as the afterglow. Details of this source are given below: Source 1: RA (J2000.0): 105.7399 = 07h 02m 57.59s Dec (J2000.0): -64.8525 = -64d 51' 09.1" Error: 3.7 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: 0.0323 +/- 0.0046 ct s^-1 Distance: 134 arcsec from EP position. Flux: (1.74 +/- 0.25)e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV) A further uncatalogued X-ray source was also detected, however this was too far from the EP position to be the afterglow. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021858. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41613. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39677] EP250830a: Global MASTER-Net observations report
by GCN Circulars 30 Aug '25

30 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41612 SUBJECT: EP250830a: Global MASTER-Net observations report DATE: 25/08/30 14:27:21 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 EP250830a ( EP Team et al., GCN 41611) errorbox 9623 sec after trigger time at 2025-08-30 06:37:32 UT, with upper limit up to 20.1 mag. The observations began at zenith distance = 65 deg. The sun altitude is -54.1 deg. The galactic latitude b = -23 deg., longitude l = 275 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2980099 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 9644 | 2025-08-30 06:37:32 | MASTER-OAFA | (07h 03m 18.97s , -64d 47m 00.0s) | C | 40 | 19.3 | 9684 | 2025-08-30 06:37:32 | MASTER-OAFA | (07h 03m 18.97s , -64d 46m 60.0s) | C | 120 | 20.1 | Coadd 9690 | 2025-08-30 06:38:18 | MASTER-OAFA | (07h 03m 18.83s , -64d 46m 58.5s) | C | 40 | 19.3 | 9735 | 2025-08-30 06:39:04 | MASTER-OAFA | (07h 03m 18.65s , -64d 46m 56.6s) | C | 40 | 19.3 | 9781 | 2025-08-30 06:39:50 | MASTER-OAFA | (07h 03m 18.51s , -64d 46m 55.0s) | C | 40 | 19.3 | 9821 | 2025-08-30 06:39:50 | MASTER-OAFA | (07h 03m 18.52s , -64d 46m 54.9s) | C | 120 | 20.1 | Coadd 9827 | 2025-08-30 06:40:35 | MASTER-OAFA | (07h 03m 18.38s , -64d 46m 53.5s) | C | 40 | 19.3 | 9872 | 2025-08-30 06:41:21 | MASTER-OAFA | (07h 03m 18.20s , -64d 46m 52.4s) | C | 40 | 19.3 | 9918 | 2025-08-30 06:42:07 | MASTER-OAFA | (07h 03m 18.10s , -64d 46m 51.1s) | C | 40 | 19.4 | 9964 | 2025-08-30 06:42:52 | MASTER-OAFA | (07h 03m 17.96s , -64d 46m 49.8s) | C | 40 | 19.4 | 10010 | 2025-08-30 06:43:38 | MASTER-OAFA | (07h 03m 17.75s , -64d 46m 48.2s) | C | 40 | 19.3 | 10056 | 2025-08-30 06:44:24 | MASTER-OAFA | (07h 03m 17.57s , -64d 46m 46.8s) | C | 40 | 19.3 | 10101 | 2025-08-30 06:45:10 | MASTER-OAFA | (07h 03m 17.44s , -64d 46m 45.6s) | C | 40 | 16.0 | 10147 | 2025-08-30 06:45:56 | MASTER-OAFA | (07h 03m 17.20s , -64d 46m 44.0s) | C | 40 | 19.1 | 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/41612. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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