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

[vsnet-grb-info 38550] GRB 250520A: 10 GHz VLA radio source
by GCN Circulars 22 May '25

22 May '25

TITLE: GCN CIRCULAR NUMBER: 40518 SUBJECT: GRB 250520A: 10 GHz VLA radio source DATE: 25/05/22 02:15:16 GMT FROM: Genevieve Schroeder at Cornell University <genevieveschroeder(a)u.northwestern.edu> G. Schroeder (Cornell), J. Rastinejad, W. Fong (Northwestern), T. Laskar (Utah) report: We observed the location of the short-duration GRB 250520A (Eyles-Ferris et al., GCN 40491; SVOM/GRM Team, GCN 40495; Tembhurnikar et al., GCN 40497; Frederiks et al., GCN 40512) with the Karl G. Jansky Very Large Array (VLA) in D->C configuration under program 25A-063 (PI Schroeder) at a mid time of 2025 May 21 at 09:22 UT (1.28 days post-burst) for 1.25 hours at a mean frequency of 10 GHz. In preliminary analysis, we detect a 4-sigma radio source with a flux density of ~18 microJy at the position: RA(J2000) = 18:49:08.57 Dec(J2000) = -11:52:07.7 with an uncertainty of ~0.8" in each coordinate. This position is consistent with the X-ray position (Goad et al., GCN 40494) but offset (~2") from the optical source reported by Xin et al. (GCN 40500), which has not yet shown any evidence for fading (Yang et al., GCN 40511). At the position of the radio source, we do not detect any optical emission in Gemini i-band imaging (Rastinejad et al., GCN 40504). Further observations are planned to assess the variability of the radio source and its connection, if any, to GRB 250520A. We thank the VLA staff for quickly approving and executing these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/40518. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38549] GRB 250521B: Swift ToO observations
by GCN Circulars 21 May '25

21 May '25

TITLE: GCN CIRCULAR NUMBER: 40517 SUBJECT: GRB 250521B: Swift ToO observations DATE: 25/05/21 23:45:15 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the SVOM/ECLAIRs-detected event GRB 250521B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021830 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the SVOM/ECLAIRs event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40517. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38548] GRB 250521D: Fermi GBM Final Real-time Localization
by GCN Circulars 21 May '25

21 May '25

TITLE: GCN CIRCULAR NUMBER: 40516 SUBJECT: GRB 250521D: Fermi GBM Final Real-time Localization DATE: 25/05/21 22:32:26 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 22:21:56 UT on 21 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250521D (trigger 769558921.008874 / 250521932). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 281.6, Dec = 21.3 (J2000 degrees, equivalent to J2000 18h 46m, 21d 18'), with a statistical uncertainty of 2.6 degrees. The angle from the Fermi LAT boresight is 65.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250521932/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250521932/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250521932/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40516. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38547] GRB 250521C: Fermi GBM Final Localization
by GCN Circulars 21 May '25

21 May '25

TITLE: GCN CIRCULAR NUMBER: 40515 SUBJECT: GRB 250521C: Fermi GBM Final Localization DATE: 25/05/21 18:36:09 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> The Fermi GBM team reports the detection of a likely SHORT GRB "At 13:31:01.20 UT on 21 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250521C (trigger 769527066/250521563). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 105.00, Dec = 65.63 (J2000 degrees, equivalent to J2000 7h 0m, +65d 37'), with a statistical uncertainty of 16.05 degrees. The angle from the Fermi LAT boresight is 91 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250521563/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250521563/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250521563/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/40515. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38546] GRB 250521A: DDOTI Optical Upper Limit
by GCN Circulars 21 May '25

21 May '25

TITLE: GCN CIRCULAR NUMBER: 40514 SUBJECT: GRB 250521A: DDOTI Optical Upper Limit DATE: 25/05/21 17:03:34 GMT FROM: sahil.atri(a)students.uniroma2.eu Sahil Atri (U Roma), Rosa L. Becerra (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 observed the field of the GRB 250521A detected by Fermi/GBM (Fermi GBM Team, GCN 40508) 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 2025-05-21 UTC. DDOTI observed the Fermi/GBM error region, covering about 93% of the error region (Fermi GBM Team, GCN Circ. 40508). DDOTI observed the field of GRB 250521A from 04:41 UTC to 11:25 UTC (from T+0.2 h to T+ 6.7 h after the trigger) and obtained a total exposure of 2.5 hours, alternating with other scientific programs. Comparing our observations to the USNO-B1 and Pan-STARRS PS1 DR2 catalogues, we detect no uncatalogued fading sources within the observed field to a 10-sigma limiting AB magnitude of: w > 20.91 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/40514. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38545] GRB 250521B: SVOM detection of a burst through offline search
by GCN Circulars 21 May '25

21 May '25

TITLE: GCN CIRCULAR NUMBER: 40513 SUBJECT: GRB 250521B: SVOM detection of a burst through offline search DATE: 25/05/21 16:50:38 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Foisseau, C. Lachaud (APC), M. Brunet (IRAP), N. Dagoneau (CEA) report on behalf of the SVOM team: The SVOM/ECLAIRs telescope detected a transient source, labelled GRB 250521B, starting at 2025-05-21T04:19:17.8 UTC (Tb), through an offline search with the event-by-event data downloaded through the X-band ground station. The burst was detected within several energy ranges in a 5.12 seconds timescale. The best detection is obtained by the image trigger with a signal-to-noise ratio of 7.2 within 8-50 keV over a time window of 5.12 seconds starting at Tb. The lightcurve consists of a single pulse lasting around 5s. The localization of the source is RA, Dec = 200.822, 1.766 degrees: RA (J2000) = 13h23m17.3s Dec (J2000) = 01d45m57.6s with a 90% C.L. radius of 12.2 arcmin (including systematic error of 6 arcmin added in quadrature). We note that no bright X-ray sources are found in the error box. The Space 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. ECLAIRs was developed jointly by APC, CEA, CNES, and IRAP. The SVOM point of contact for this event is : A. Foisseau : foisseau(a)apc.in2p3.fr Please contact him by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/40513. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38544] Konus-Wind detection of GRB 250520A (short/hard)
by GCN Circulars 21 May '25

21 May '25

TITLE: GCN CIRCULAR NUMBER: 40512 SUBJECT: Konus-Wind detection of GRB 250520A (short/hard) DATE: 25/05/21 14:42:50 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The short GRB 250520A (Swift detection: Eyles-Ferris et al., GCN 40491; SVOM/GRM observation: Wang et al., GCN 40495) triggered Konus-Wind (KW) at T0=9741.866 s UT (02:42:21.866). The burst light curve shows a single pulse, which starts at ~T0-0.07 s and has a duration of ~0.26 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250520_T09741/ As observed by Konus-Wind, the burst had the total fluence of (3.38 ± 0.75)x10^-6 erg/cm^2 and a 16-ms peak energy flux, measured from T0-0.032, of (3.49 ± 0.81)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst (measured from T0 to T0+0.192 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.48 (-0.27,+0.41), the high energy photon index beta = -2.51 (-1.99,+0.47), the peak energy Ep = 671 (-211,+247) keV, chi2 = 37/27 dof. The spectrum near the peak count rate (measured from T0 to T0+0.064 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.67 (-0.27,+0.46), the high energy photon index beta = -2.39 (-7.61,+0.53), the peak energy Ep = 1099 (-505,+876) keV, chi2 = 11/17 dof. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/40512. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38543] GRB 250520A: VLT/FORS2 Optical Observation
by GCN Circulars 21 May '25

21 May '25

TITLE: GCN CIRCULAR NUMBER: 40511 SUBJECT: GRB 250520A: VLT/FORS2 Optical Observation DATE: 25/05/21 14:13:02 GMT FROM: Yu-Han Yang at University of Rome Tor Vergata <yyang(a)roma2.infn.it> 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 250520A (Eyles-Ferris et al., GCN 40491) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began 27.8 hours after the trigger and were carried out in the R filter with an average airmass of ~1. We detect the source previously reported as a candidate from SVOM/VT (Xin et al., GCN 40500) with a preliminary magnitude of R~23 AB mag, calibrated using nearby stars from the Pan-STARRS DR2 (Flewelling et al., 2020, ApJS, 251, 7), uncorrected for Galactic extinction. Compared to the magnitude reported by SVOM/VT (Xin et al., GCN 40500), we find no evidence of fading. No other source is detected within the XRT error circle (Goad et al. GCN 40494) down to R>24.6 (3-sigma). 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/40511. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38542] GRB 250502A: Tautenburg observations
by GCN Circulars 21 May '25

21 May '25

TITLE: GCN CIRCULAR NUMBER: 40510 SUBJECT: GRB 250502A: Tautenburg observations DATE: 25/05/21 14:09:26 GMT FROM: Sylvio Klose at TLS Tautenburg <klose(a)tls-tautenburg.de> K. Kritik, L. Berthel, T. Ranganathan, J. Kahl, S. Schmidl (all FSU Jena), M. Hartmann, B. Stecklum, S. Klose (all Tautenburg) report: We observed the field of GRB 250502A (Wang et. al., GCN 40313) with the 1.3m Schmidt telescope using the prime focus CCD camera. Observations started on May 2, 2025, at 22:18:13 UT, about 13.5 hrs after the SVOM trigger, at a mean airmass of 2.2. The optical transient first reported by Rakotondrainibe et. al. (GCN 40315) was clearly detected. Based on 40 min of exposure, at a midtime of 22:38 UT, we measure a preliminary r-band magnitude (AB) of 20.88 +/- 0.20 mag, calibrated against Pan-STARRS DR1. We apologize for the late submission of this circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/40510. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38541] GRB 250520A: Swift/UVOT Upper Limits
by GCN Circulars 21 May '25

21 May '25

TITLE: GCN CIRCULAR NUMBER: 40509 SUBJECT: GRB 250520A: Swift/UVOT Upper Limits DATE: 25/05/21 13:02:53 GMT FROM: Samantha Oates at University of Birmingham <samantha.oates(a)alumni.ucl.ac.uk> S. R. Oates (Lancaster U.) and R. A. J. Eyles-Ferris (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250520A 127 s after the BAT trigger (Eyles-Ferris et al., GCN Circ. 40491). No optical afterglow consistent with the enhanced XRT position (Goad et al., GCN Circ. 40494) or the SVOM/VT optical candidate (Xin et al., GCN Circ. 40500) 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/3sigUL white 149 298 147 >20.9 white 149 1373 392 >21.3 v 127 1251 110 >18.9 b 481 1349 97 >19.7 u 456 1324 97 >19.3 uvw1 432 1300 97 >19.1 uvm2 407 1275 78 >18.6 uvw2 358 1394 112 >19.2 We caution that the photometry may not be accurate, as the source region used to determine the optical/UV limits, is on an area of the UVOT detector with low sensitivity. The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.754 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40509. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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