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

[vsnet-grb-info 38661] GRB 250530A: SVOM/GRM analysis
by GCN Circulars 04 Jun '25

04 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40625 SUBJECT: GRB 250530A: SVOM/GRM analysis DATE: 25/06/04 03:52:55 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Chao Zheng, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: M. G. Bernardini (INAF-OAB, LUPM) Report on behalf of the SVOM team: SVOM/GRM detected the burst GRB 250530A at 2025-05-30T06:31:54.99 UTC (T0), which is also detected by SVOM/ECLAIRs (Wang et al., GCN #40576). With the event-by-event data downloaded through the X-band ground station, we conducted the standard analysis pipeline of GRB 250530A. The GRM light curve shows that this burst consists of a single pulse with a T90 of 15.0 +3.0/-4.0 s in the 15-5000 keV band, which is consistent with the result from VHF data. With the localization of ECLAIRs (RA=186.71, DEC=-2.5648), the time-averaged spectrum from T0 to T0+15 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.26 +0.18/-0.13 and the cutoff energy, parameterized as Epeak, is 707 +1140/-360 keV. The event fluence (10-1000 keV) in this time interval is (2.8 +/-0.4)E-06 erg/cm^2. Thus GRB 250530A is consistent with Type I GRBs in the 'Amati' relation diagram although the duration is much longer than 2 seconds, as shown at: https://www.bursthub.cn//admin/static/grb250530A_amati.png Further follow-up observations are encouraged. We note that the calibration of SVOM/GRM is undergoing thus these results are preliminary. Refined analysis will be reported later. 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/GRM 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/40625. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38660] GRB 250601A: PRIME J band upper limit.
by GCN Circulars 03 Jun '25

03 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40624 SUBJECT: GRB 250601A: PRIME J band upper limit. DATE: 25/06/03 22:03:13 GMT FROM: N. Passaleva at Sapienza University of Rome <niccolo.passaleva(a)uniroma1.it> N. Passaleva (U Rome), O. Guiffreda (UMD), J. Durbak (UMD), M. Elkabir (U Rome), E. Troja (U Rome), A. S. Kutyrev (NASA/GSFC), S. B. Cenko (NASA/GSFC) Following the Fermi Gamma-ray Burst Monitor (GBM) detection (GCN 40596), and the Swift/BAT-GUANO arcminute localization of same event, we observed the transient field in J filter with PRIME ~23.5 hours after the initial Fermi detection. Using nearby VISTA Hemispherical Survey (VHS) we do not detect any uncatalogued source down to J>20.3 AB (3-sigma) at the position of the candidates reported by Swift/XRT (Page et al. GCN 40604, Salvaggio et al., GCN 40606) and EP/FXT (Liu et al., GCN 40607). PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023, Durbak et al. 2024). We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/40624. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38659] Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
by GCN Circulars 03 Jun '25

03 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40623 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB DATE: 25/06/03 21:37:43 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> L. Scotton (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 770675211/250603852 at 20:26:46.25 UT on 03 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/40623. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38658] GRB 250601A: VLT/FORS2 Optical Observation
by GCN Circulars 03 Jun '25

03 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40622 SUBJECT: GRB 250601A: VLT/FORS2 Optical Observation DATE: 25/06/03 19:31:34 GMT FROM: Roberto Ricci at INAF-IRA <ricci(a)ira.inaf.it> Roberto Ricci (U Rome), Yu-Han Yang (U Rome), Rosa L. Becerra (U Rome) and Eleonora Troja (U Rome) report on behalf of the ERC BHianca team: We observed the field of GRB 250601A (Fermi GBM team GCN 40596; DeLaunay et al., GCN 40600) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began 29.8 hours after the trigger and were carried out in the R filter with an average airmass of ~2.3. Our field covers the candidates reported by Swift/XRT (Page et al. GCN 40604, Salvaggio et al., GCN 40606) and EP/FXT (Liu et al., GCN 40607). Compared with the Legacy Survey DR10 (Dey et al. 2019) catalogue, we do not detect any uncatalogued source down to R>24 AB (3-sigma). Further observations are planned. We thank the staff at the VLT for the rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/40622. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38657] GRB 250601A: Fermi GBM Observation
by GCN Circulars 03 Jun '25

03 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40621 SUBJECT: GRB 250601A: Fermi GBM Observation DATE: 25/06/03 15:42:16 GMT FROM: Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma(a)nasa.gov> V. Sharma (NASA-GSFC/UMBC) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 17:29:35 UT on 1 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250601A (trigger 770491780 / 250601729). which was also detected by Swift/BAT-GUANO (J. DeLaunay et al. 2025, GCN 40600) and Swift/XRT (K.L. Page et al. 2025, GCN 40604). The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position. The angle from the Fermi LAT boresight is 24 degrees. The GBM light curve consists of main emission episode with a duration (T90) of about 3 s (50-300 keV). The time-averaged spectrum from T0-0.5 to T0+2.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.58 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 873 +/- 142 keV. The event fluence (10-1000 keV) in this time interval is (2.7 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1 s in the 10-1000 keV band is 4.9 +/- 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/40621. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38656] GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
by GCN Circulars 03 Jun '25

03 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40620 SUBJECT: GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization DATE: 25/06/03 15:06:50 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Rosa L. Becerra (U Roma), Sahil Atri (U Roma), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report: We continued our follow-up campaign of GRB 250602A, detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 40602) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2025-06-03 UTC. DDOTI observed the Fermi/LAT error region (Holzmann Airasca et al., GCN Circ. 40611), from 03:51 UTC to 05:01 UTC (from T+24.7 h to T+ 25.9 h after the trigger), obtaining a total exposure time of 48 minutes. By comparing our observations with the USNO-B1 and Pan-STARRS PS1 DR2 catalogs, and performing image subtraction using a Pan-STARRS PS1 DR2 template, we detect no uncatalogued sources within the observed field down to a 10-sigma limiting AB magnitude of: w > 20.0 Unfortunately, the Fermi/LAT error region was not included in the field observed on the night of 2025-06-02 UTC (Atri et al., GCN Circ. 40610). This value is not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40620. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38655] GRB 250603A: Swift/UVOT Upper Limits
by GCN Circulars 03 Jun '25

03 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40619 SUBJECT: GRB 250603A: Swift/UVOT Upper Limits DATE: 25/06/03 13:14:52 GMT FROM: Samantha Oates at University of Birmingham <samantha.oates(a)alumni.ucl.ac.uk> S. R. Oates (Lancaster U.) and T. M. Parsotan (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250603A 105 s after the BAT trigger (Parsotan et al., GCN Circ. 40613). No optical afterglow consistent with the enhanced XRT position (Beardmore et al., GCN Circ. 40616) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 105 255 147 >20.4 u_FC 318 567 246 >19.7 white 105 1531 382 >21.0 v 647 5129 190 >19.0 b 573 1516 97 >19.6 u 318 1491 324 >19.8 w1 697 1467 78 >18.7 m2 672 1442 97 >18.5 w2 623 5029 294 >19.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 1.89 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40619. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38654] GRB 250603A: Swift-XRT refined Analysis
by GCN Circulars 03 Jun '25

03 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40618 SUBJECT: GRB 250603A: Swift-XRT refined Analysis DATE: 25/06/03 12:58:34 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> S. Campana (INAF-OAB), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), D.N. Burrows (PSU), M.A. Williams (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 7.3 ks of XRT data for GRB 250603A, from 92 s to 34.7 ks after the trigger. The data comprise 3 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a power-law decay with a decay index of alpha=1.17 (+0.09, -0.08). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.48 (+0.32, -0.30). The best-fitting absorption column is 1.6 (+0.5, -0.4) x 10^22 cm^-2, in excess of the Galactic value of 6.9 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 7.6 x 10^-11 (1.1 x 10^-10) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.6 (+0.5, -0.4) x 10^22 cm^-2 Galactic foreground: 6.9 x 10^21 cm^-2 Excess significance: 3.3 sigma Photon index: 1.48 (+0.32, -0.30) If the light curve continues to decay with a power-law decay index of 1.17, the count rate at T+24 hours will be 8.8 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.7 x 10^-14 (9.8 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01320335. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40618. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38653] Fermi trigger No 770638414: Global MASTER-Net observations report
by GCN Circulars 03 Jun '25

03 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40617 SUBJECT: Fermi trigger No 770638414: Global MASTER-Net observations report DATE: 25/06/03 11:32:32 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 GRB250603.43 (trigger No 770638414,19h 14m 55.20s , +26d 21m 36.0s, R=7.82) errorbox 165 sec after notice time and 195 sec after trigger time at 2025-06-03 10:16:44 UT, with upper limit up to 16.8 mag. Observations started at twilight. The observations began at zenith distance = 73 deg. The sun altitude is -14.5 deg. The galactic latitude b = 7 deg., longitude l = 59 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2890867 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 215 | 2025-06-03 10:16:44 | MASTER-OAFA | (19h 39m 27.79s , +30d 15m 05.9s) | C | 40 | 16.8 | 266 | 2025-06-03 10:17:31 | MASTER-OAFA | (19h 39m 27.74s , +30d 15m 07.5s) | C | 50 | 16.8 | 327 | 2025-06-03 10:18:27 | MASTER-OAFA | (19h 39m 27.67s , +30d 15m 08.4s) | C | 60 | 16.8 | 399 | 2025-06-03 10:19:33 | MASTER-OAFA | (19h 39m 27.58s , +30d 15m 09.3s) | C | 70 | 16.8 | 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/40617. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38652] GRB 250603A: Enhanced Swift-XRT position
by GCN Circulars 03 Jun '25

03 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40616 SUBJECT: GRB 250603A: Enhanced Swift-XRT position DATE: 25/06/03 06:07:13 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 1415 s of XRT Photon Counting mode data and 1 UVOT images for GRB 250603A, 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 = 129.93745, -39.29287 which is equivalent to: RA (J2000): 08h 39m 44.99s Dec (J2000): -39d 17' 34.3" 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/40616. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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