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

[vsnet-grb-info 38721] GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
by GCN Circulars 11 Jun '25

11 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40682 SUBJECT: GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst DATE: 25/06/11 03:32:59 GMT FROM: Hao Zhou at Purple Mountain Observatory, CAS <haozhou(a)pmo.ac.cn> Yun Wang, Hao Zhou, Zhi-Ping Jin, Yi-Zhong Fan (PMO,CAS): We report a possible sub-threshold detection of GRB 250610B by the Fermi Gamma-ray Burst Monitor (GBM). The burst was initially detected by SVOM/ECLAIRs (Saccardi et al., GCN 40671) at T0 = 2025-06-10 16:32:58 UTC. The reported position is R.A., Dec. 200.1831, 31.1028 degrees. Based on the poshist file, the GBM NaI detector with the smallest incident angle to the burst direction was nb. We used the GBM Time-Tagged Event (TTE) data to extract the spectrum over the interval from T0–10 s to T0+80 s. The background was estimated from two intervals: T0–200 s to T0–100 s and T0+300 s to T0+400 s. We fitted the spectrum with a cutoff power-law model (dN/dE ~ (E^-alpha)*exp(-E/Ec)), obtaining alpha ~ -0.6 and a peak energy Ep=(2-alpha)*Ec ~ 55 keV. The energy flux in the 1–10000 keV band is estimated to be ~ 5.72e-9 erg/cm^2/s. The spectrum can be fitted with a blackbody model, yielding a temperature of kT ~13 keV and providing a better goodness of fit than a cutoff power-law model. This is a test using RapidGBM (https://github.com/0neyun/RapidGBM) and the results presented here should be considered preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/40682. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38720] GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
by GCN Circulars 11 Jun '25

11 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40681 SUBJECT: GRB 250610B: EP-FXT follow-up observation and afterglow counterpart DATE: 25/06/11 02:44:20 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. F. Liang, Y. L. Hua (PMO, CAS), X. P. Xu, H. W. Pan(NAO, CAS), A. Saccardi, J. Rodriguez, N. Dagoneau (CEA), C. Van Hove (IJCLab) report on behalf of the Einstein Probe and SVOM team We performed a follow-up observation of GRB 250610B (detected through offline search of SVOM/ECLAIRs, Saccardi et al, GCN #40671; followed by Swift/XRT, Evans et al. GCN #40679), with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation began at 2025-06-10T17:04:27 (T-TGRB ~ 1.9ks), and the exposure time is about 5.8 ks. Only 1 uncatalogued source was detected both by FXTA and FXTB in the 90% localization error circle provided by SVOM/ECLAIRs (with a radius of 3.22 arcmin centered at RA, DEC = 200.1831 deg, +31.1028 deg), as listed below (the FXT flux is taken from FXTB module). ------------------------------------------------------------------------------------------------- Source name | RA | DEC | Estimated Flux | SNR | Dist from SVOM/ECLAIRs | | deg | deg | (erg/s/cm^2) | | offset (in arcmin) | EPF_J132043.1+310615 | 200.1795 | 31.1043 | 2.8(+/-0.2) x 10^-12 | 5.9 | 0.21 | ------------------------------------------------------------------------------------------------- Note: * EPF_J132043.1+310615 was also detected by Swift/XRT (GCN #40679) in a ~2.0 ks observation, with a mean flux of ~3.9(+/-0.3)e-12 erg/s/cm^2, the position of this source is also associated with the Optical counterpart detected by SVOM/VT (Li et al. GCN #40678). The above observation was made with the EP-FXT instrument. 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). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES. View this GCN Circular online at https://gcn.nasa.gov/circulars/40681. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38719] Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
by GCN Circulars 11 Jun '25

11 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40680 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB DATE: 25/06/11 00:48:18 GMT FROM: sumanbala2210(a)gmail.com S. Bala (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 771286888/250610932 at 22:21:23.29 UT on 10 June 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/40680. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38718] GRB 250610B: Swift-XRT counterpart detection
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40679 SUBJECT: GRB 250610B: Swift-XRT counterpart detection DATE: 25/06/10 23:55:14 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 250610B, collecting 2.0 ks of Photon Counting (PC) mode data between T0+2.8 ks and T0+8.9 ks after the trigger. A likely counterpart has been found consistent with the optical detection (GCN Circ. 40676, 40677 and 40678). The details of this source are: Source 1 (SWIFT J132043.2+310614): ================================== RA (J2000.0): 200.1802 = 13h 20m 43.25s Dec (J2000.0): +31.1040 = +31d 06' 14.4" Error: 3.7 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 4.3 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.1084 +/- 0.0084 ct s^-1 Mean flux: (3.91 +/- 0.30)e-12 erg cm^-2 s^-1 Peak rate: 0.134 +/- 0.022 ct s^-1 Peak flux: (4.85 +/- 0.81)e-12 erg cm^-2 s^-1 ECF: 3.61e-11 erg cm^-2 ct^-1, assuming NH=1.44e+20 cm^-2, gamma=1.78; determined from a spectral fit. XMM UL: 2.4e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is 3.0-sigma above this 3-sigma upper limit. There is no evidence for fading. 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. This circular is an officicial product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40679. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38717] GRB 250610B: SVOM/VT optical counterpart
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40678 SUBJECT: GRB 250610B: SVOM/VT optical counterpart DATE: 25/06/10 23:35:24 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), A. Saccardi, J. Rodriguez, N. Dagoneau (CEA), C. Van Hove (IJCLab) report on behalf of the SVOM mission team. SVOM performed a Target of Opportunity observation of GRB 250610B detected by SVOM/Eclairs (Saccardi et al., GCN 40671). SVOM/VT began observing the field at 2025-06-10 17:04:26 UTC, 0.52 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. An uncatalogued source, compared to legacy survey, is found using VT X-band data, within the error box of Swift/XRT1 at R.A., Dec 200.179739, 31.10496 degrees: RA (J2000) = 13:20:43.1 Dec (J2000) = +31:06:17.9 with an uncertainty of 0.5 arcsec. The source is detected in both VT_R and VT_B, and was fading by 0.3 mag in 2 orbits, the magnitudes are: Mid-time after the burst | exposure time (s) | band | mag (AB) | mag err --------------------|-------------------|------|----------|-------- 1.234 hour | 70 | VT_B | 20.7 ｜ 0.1 1.234 hour | 70 | VT_R | 20.3 ｜ 0.1 This position and the brightness is consistent with the reports (Schneider et al., GCN 40676, Gompertz et al., GCN 40677) 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. The Burst Advocate (BA) on shift for this alert is Andrea Saccardi(a)cea.fr. View this GCN Circular online at https://gcn.nasa.gov/circulars/40678. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38716] GRB 250610B: LT detection of the optical counterpart
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40677 SUBJECT: GRB 250610B: LT detection of the optical counterpart DATE: 25/06/10 23:30:06 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk> B. P. Gompertz (U. Birmingham), Dimple (U. Birmingham), A. Martin-Carrillo (UCD) and G. Corcoran (UCD) report on behalf of a larger collaboration: We initiated follow-up observations of GRB 250610B (Saccardi et al., GCN 40671) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 22:24:56 UT, ~5.85 hr after the SVOM/ECLAIRs trigger, and consisted of 7x120 s and 10x120 s exposures in the SDSS g and i filters, respectively. We detect the optical counterpart (Schneider et al., GCN 40676) with AB magnitudes of g = 21.38 ± 0.11 and i = 21.02 ± 0.06. Magnitudes are calibrated against nearby Pan-STARRS stars and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40677. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38715] GRB 250610B: optical counterpart candidate
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40676 SUBJECT: GRB 250610B: optical counterpart candidate DATE: 25/06/10 23:26:37 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> B. Schneider (LAM), A. de Ugarte Postigo (LAM), C. Adami (LAM/Pytheas/AMU), J.P Troncin (Pytheas/OHP), A. Martin-Carrillo (UCD), S. Basa (LAM/OHP/Pytheas/AMU), E. Le Floc'h (CEA/Irfu), report on behalf of a larger collaboration: We observed the field of the GRB 250610B (Saccardi et al., GCN 40671) using the T120cm telescope at Observatoire de Haute-Provence (France). We obtained 30 minutes of exposure in the r-band starting at 20:31:03.29 UT on 2025-06-10 (3.97 hr after the trigger). In the stacked image, we detected a new source at RA, DEC (J2000) 200.1796, +31.1047, not visible in the Legacy Survey and consistent with the XRT error: RA(J2000) = 13:20:43.11 DEC(J2000) = +31:06:16.8 with an uncertainty of 0.5 arcsec. The preliminary magnitude derived for that source is: r = 20.96 +/- 0.15 mag (AB) The photometric calibration was performed using nearby stars from the SDSS catalog and the magnitude is not corrected for Galactic extinction. We acknowledge the excellent support from Observatoire de Haute-Provence and in particular the students and professors from the summer camp OHP 2025. View this GCN Circular online at https://gcn.nasa.gov/circulars/40676. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38714] GRB 250610C: Fermi GBM Final Real-time Localization
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40675 SUBJECT: GRB 250610C: Fermi GBM Final Real-time Localization DATE: 25/06/10 23:21:44 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 23:11:04 UT on 10 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250610C (trigger 771289869.772446 / 250610966). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 26.8, Dec = 59.7 (J2000 degrees, equivalent to J2000 01h 47m, 59d 42'), with a statistical uncertainty of 2.5 degrees. The angle from the Fermi LAT boresight is 64.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250610966/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250610966/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250610966/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40675. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38713] GRB 250610B: GOTO optical upper limit
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40674 SUBJECT: GRB 250610B: GOTO optical upper limit DATE: 25/06/10 21:43:38 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk> B. P. Gompertz, D. O’Neill, D. Steeghs, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, A. Kumar, B. Godson, D. K. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022; Dyer et al. 2024) in response to the SVOM/ECLAIRS detected GRB 250610B (Saccardi et al., GCN 40671). Targeted observations were performed with GOTO-North centred at 2025-06-10 21:13:20 UT (+4.66h post trigger). Observations consisted of 4x90s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. We detect no new sources within the ECLAIRS localisation region down to a 3-sigma limiting magnitude of L > 19.92 AB mag. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/40674. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38712] EP250610a: Global MASTER-Net observations report
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40673 SUBJECT: EP250610a: Global MASTER-Net observations report DATE: 25/06/10 19:36:20 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 EP250610a ( EP Team et al., GCN 40660) errorbox 972 sec after notice time and 9094 sec after trigger time at 2025-06-10 06:57:24 UT, with upper limit up to 17.6 mag. The observations began at zenith distance = 82 deg. The sun altitude is -57.2 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP250610a errorbox 44872 sec after notice time and 52993 sec after trigger time at 2025-06-10 19:09:03 UT, with upper limit up to 17.4 mag. The observations began at zenith distance = 15 deg. The sun altitude is -18.3 deg. The galactic latitude b = 42 deg., longitude l = 61 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2898181 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 9229 | 2025-06-10 06:57:24 | MASTER-OAFA | (16h 33m 32.66s , +38d 48m 08.6s) | C | 270 | 17.6 | Coadd 53024 | 2025-06-10 19:09:03 | MASTER-Kislovodsk | (16h 31m 32.68s , +38d 50m 44.6s) | C | 60 | 17.0 | 53210 | 2025-06-10 19:12:09 | MASTER-Kislovodsk | (16h 31m 34.53s , +38d 48m 49.2s) | C | 60 | 17.4 | 53547 | 2025-06-10 19:17:46 | MASTER-Kislovodsk | (16h 31m 41.01s , +38d 50m 51.7s) | C | 60 | 17.1 | 53720 | 2025-06-10 19:20:40 | MASTER-Kislovodsk | (16h 31m 35.46s , +38d 50m 56.6s) | C | 60 | 16.0 | 53893 | 2025-06-10 19:23:32 | MASTER-Kislovodsk | (16h 31m 32.13s , +38d 48m 59.5s) | C | 60 | 17.0 | 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/40673. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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