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[vsnet-grb-info 38871] GRB 250625A: SVOM/VT optical confirmation
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40830 SUBJECT: GRB 250625A: SVOM/VT optical confirmation DATE: 25/06/26 00:20:46 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L. P. Xin, H. L. Li, Y. L. Qiu, C. Wu, Y.N. Ma, Z. H. Yao, 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), A. Li (BNU) report on behalf of the SVOM/VT team SVOM/VT performed a Target of Opportunity observation of GRB 250625A detected by Swift-BAT（Ferro et al., GCN 40825) and Fermi-GBM (GCN #40824). The observation began at 2025-06-25T16:50:36 UTC, 45.7 minutes after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical counterpart (Moskvitin et al., GCN 40828) within the errorbox of Swift/XRT (Beardmore et al., GCN 40827) was detected in the 38*70 sec stack image with a magnitude of VT_B=22.5+/-0.15 mag in AB magnitude with a mid time of 69 min after the burst. The counterpart is also detected in VT_R band in the stack image, but it has some contaimination from the blooming light from the nearby bright source. More detailed data analysis is on going. Our photometry was not corrected for Galactic extinction. 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/40830. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38870] GRB 250620B: Fermi GBM Observation
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40829 SUBJECT: GRB 250620B: Fermi GBM Observation DATE: 25/06/25 23:57:52 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 13:22:56.94 UT on 20 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB250620B (trigger 772118581/250620558). which was also detected by Swift/BAT-GUANO (S. Ronchini et al. 2025, GCN 40800). The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position. The angle from the Fermi LAT boresight is 90 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 23 s (50-300 keV). The time-averaged spectrum from T0-2 to T0+23.6 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.3 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 430 +/- 236 keV. The event fluence (10-1000 keV) in this time interval is (2.7 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.7 s in the 10-1000 keV band is 1.9 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/40829. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38869] GRB 250625A: SAO RAS possible optical afterglow
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40828 SUBJECT: GRB 250625A: SAO RAS possible optical afterglow DATE: 25/06/25 21:47:40 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin, O. Spiridonova (SAO RAS), report on behalf of a GRB follow-up collaboration. We observed the field of the GRB 250625A (The Fermi GBM team, GCN 40824; Ferro et al., GCN 40825) with SAO RAS 1-m telescope Zeiss-1000 equipped with CCD-photometer. We obtained 6 x 300 sec. exposures in Rc band on June 25, 20:39:03--21:12:11 UT (t_mid - T0 = 4.8447 hours). Withtin the enhanced XRT error circle (Beardmore et al., GCN 40827) we detect single object with the coordinates: R.A. (J2000.0) = 17:26:02.1 Dec. (J2000.0) = +22:16:03.6 +/- 0".3 and brightness of R = 22.97 +/- 0.17, possible GRB OT. Observations are ongoing to confirm variability of the object. Preliminary photometry is based on the nearby USNO-B1.0 and has not corrected for the Galactic extinction. R.A. Dec. (2000) R2 17:26:06.4 +22:16:29.4 14.75 17:26:03.7 +22:15:09.9 15.42 17:26:10.0 +22:13:56.8 15.03 17:26:01.4 +22:18:39.0 14.59 View this GCN Circular online at https://gcn.nasa.gov/circulars/40828. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38868] GRB 250625A: Enhanced Swift-XRT position
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40827 SUBJECT: GRB 250625A: Enhanced Swift-XRT position DATE: 25/06/25 21:43:16 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 2454 s of XRT Photon Counting mode data and 3 UVOT images for GRB 250625A, 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 = 261.50887, +22.26729 which is equivalent to: RA (J2000): 17h 26m 2.13s Dec (J2000): +22d 16' 02.3" with an uncertainty of 2.3 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/40827. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38867] Fermi GRB 250625A: Global MASTER-Net observations report
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40826 SUBJECT: Fermi GRB 250625A: Global MASTER-Net observations report DATE: 25/06/25 21:15:24 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-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 250625A ( Fermi GBM team, GCN 40824) errorbox 16256 sec after notice time and 16277 sec after trigger time at 2025-06-25 20:36:14 UT, with upper limit up to 14.7 mag. The observations began at zenith distance = 22 deg. The sun altitude is -20.8 deg. The galactic latitude b = 33 deg., longitude l = 49 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2916483 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 16367 | 2025-06-25 20:36:14 | MASTER-Tavrida | (17h 25m 02.21s , +22d 17m 15.8s) | C | 180 | 14.7 | 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/40826. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38866] GRB 250625A: Swift detection of a burst
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40825 SUBJECT: GRB 250625A: Swift detection of a burst DATE: 25/06/25 16:20:37 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU), R. Gupta (NASA GSFC), J. A. Kennea (PSU), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 16:04:56 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250625A (trigger=1327910). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 261.519, +22.265 which is RA(J2000) = 17h 26m 04s Dec(J2000) = +22d 15' 55" 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 8 sec. The peak count rate was ~2200 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 16:06:56.2 UT, 119.8 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 261.50871, 22.26763 which is equivalent to: RA(J2000) = 17h 26m 02.09s Dec(J2000) = +22d 16' 03.5" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 35 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (5.47 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 8 (+10.81/-7.26) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 124 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.055. This is co-detection with Fermi/GBM (GCN #40824). Burst Advocate for this burst is M. Ferro (matteo.ferro 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/40825. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38865] GRB 250625A: Fermi GBM Final Real-time Localization
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40824 SUBJECT: GRB 250625A: Fermi GBM Final Real-time Localization DATE: 25/06/25 16:15:37 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 16:04:57 UT on 25 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250625A (trigger 772560302.510236 / 250625670). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 257.2, Dec = 27.0 (J2000 degrees, equivalent to J2000 17h 08m, 27d 00'), with a statistical uncertainty of 6.9 degrees. The angle from the Fermi LAT boresight is 28.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250625670/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250625670/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250625670/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40824. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38864] GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40823 SUBJECT: GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24 DATE: 25/06/25 15:10:36 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin, O. Spiridonova (SAO RAS), N. Pankov (HSE, IKI), E. Klunko (ISTP), A. Pozanenko (IKI) report on behalf of GRB follow-up and IKI-GRB-FuN collaborations. We observed the field of the GRB 250617B (Page et al., GCN 40760; Fermi GBM team, GCN 40763; Bala and Meegan, GCN 40766; Osborne et al., GCN 40767; Williams et al., GCN 40773; Laha et al., GCN 40812) at the redshift of z = 1.396 (Corcoran et al., GCN 40776) with the 1.5-meter AZT-33IK telescope of Mondy observatory on 2025-06-23 and with the 1-m telescope Zeiss-1000 of the SAO RAS on 2025-06-24. The OT (Page et al., GCN 40760; Moskvitin et al., GCN 40761; Jelinek et al., GCN 40762; Grossan et al., GCN 40771; Ma et al., GCN 40772; Antier et al., GCN 40775; Corcoran et al., GCN 40776; Turpin et al., GCN 40777; Siegel and Page, GCN 40778; Pankov et al., GCN 40783; Gendreau-Distler et al., GCN 40789; Calapai, GCN 40804; also detected in NIR by Schneider et al., GCN 40774) is marginally detected in AZT-33IK stacked image and clearly detected in Zeiss-1000 stacked image. Preliminary results are as following. Date UT start t-T0 Exp. Filter OT Err. UL telescope (mid, days) (s) (3 sigma) 2025-06-23 16:37:49 5.84791 45*120 R 22.9 0.4 22.7 AZT-33IK 2025-06-24 22:44:03 7.09417 12*300 Rc 23.4 0.2 23.9 Zeiss-1000 This photometry is based on the USNO-B1.0 stars given in Moskvitin et. al, (GCN 40761) and has not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40823. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38863] GRB 250620A: AstroSat CZTI detection
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40822 SUBJECT: GRB 250620A: AstroSat CZTI detection DATE: 25/06/25 11:52:12 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of GRB 250620A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 40791), Swift/BAT-GUANO (DeLaunay et al., GCN Circ. 40796), and SVOM/GRM (Wang et al., GCN Circ. 40806). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. We see only the initial short duration spike in the CZT detector data. The light curve peaks at 2025-06-20 08:05:18.89 UTC. The measured peak count rate associated with the burst is 853 (+613, -193) counts/s above the background in the combined data of three quadrants (out of four), with a total of 45 (+31, -13) counts. The local mean background count rate was 118 (+14, -102) counts/s. Using cumulative rates, we measure a T90 of 0.11 (+0.03, -0.03) s for the first spike. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. We see both episodes in Veto detectors, separated by about 10 s. The light curve, showing two burst episodes, peaks at 2025-06-20 08:05:27.70 UTC. The measured peak count rate associated with the burst is 368 (+65, -69) counts/s above the background in the combined data of all quadrants, with a total of 821 (+368, -375) counts. The local mean background count rate was 1184 (+7, -8) counts/s. We measure a T90 of 12 (+2, -10) s from the cumulative Veto light curve. The large negative uncertainty arises from the relatively weak detection of the first spike. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40822. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38862] The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40821 SUBJECT: The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580 DATE: 25/06/25 11:27:58 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO), W. X. Wang (NAO, CAS), J. H. Wu (GZHU), W. F. Wen(SZTU), W. D. Zhang(NAO, CAS), report on behalf of the Einstein Probe team: The EP-WXT trigger 01709179396 at the time of 2025-06-25T09:21:20, is likely a stellar flare associated with CSTAR 38580. The estimated flux of the flare is around 8 x 10^-11 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 3.2 x 10^31 erg/s. 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/40821. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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