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[vsnet-grb-info 38211] GRB 250409A: Swift/UVOT Follow up
by GCN Circulars 20 Apr '25

20 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40185 SUBJECT: GRB 250409A: Swift/UVOT Follow up DATE: 25/04/20 12:39:57 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> Paul Kuin (MSSL/UCL) reports on behalf of the Swift/UVOT team: The Swift/UVOT began observations of the field of SVOM detected GRB 250419A/(SVOM burst-id sb25041901) 3790s after the SVOM ECLAIR trigger at 2025-04-19T02:29:32 (Wang et al., GCN Circ. 40168). A source consistent with the position reported by Kin Ocelotl López et al. (Colibri - GCN Circ. 40169) and Liping Xin at al. (SVOM-VT GCN Circ 40170), also reported by Weikang Zheng et al. (KAIT - GCN Circ. 40171) and Amit Kumar et al. (GCN Circ. 40172) has been detected in the initial UVOT exposures. The detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) Exp(s) Mag (Vega) u 3790 1667 17.73 +/- 0.04 u 9323 259 18.19 +/- 0.10 u 48658 1206 19.64 +/- 0.14 u 54296 1028 19.52 +/- 0.13 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.085 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40185. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38210] GRB 250416C / EP250416a: SVOM/GRM observation of a burst
by GCN Circulars 20 Apr '25

20 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40184 SUBJECT: GRB 250416C / EP250416a: SVOM/GRM observation of a burst DATE: 25/04/20 12:06:30 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Maria-Grazia Bernardini (INAF-OAB), Stéphane Schanne (CEA), Frédéric Piron (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered on-ground by GRB 250416C at 2025-04-16T17:53:48 (T0). This burst was also detected by Konus-Wind (D. Svinkin et al, GCN 40167) and EP (Zhao et al., GCN 40154; Zhou et al., GCN 40165). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 8 +4/-4 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250416C.png The time coincidence and relative counts of each detectors of GRM suggest that this GRB is associated with EP250416a. In addition, the position of this burst, which is determined by EP/FXT (GCN 40154, RA: 256.4228 deg, DEC: 25.7755 deg, Error: 20 arcsec), located at about 83 degrees from the SVOM optical axis, and was outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-10 to T0+10 s is best fitted by a power law function. The power law index is -2.04 +0.19/-0.26. The event fluence (10-1000 keV) in this time interval is (1.2 +0.3/-0.3)E-06 erg/cm^2. 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/40184. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38209] GRB 250419A: LCO optical afterglow multi-band observations
by GCN Circulars 20 Apr '25

20 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40183 SUBJECT: GRB 250419A: LCO optical afterglow multi-band observations DATE: 25/04/20 11:35:44 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), and A. López-Oramas (IAC and ULL) Following the detection of the Gamma-Ray Burst GRB 250419A by SVOM/ECLAIRs (Wang et al., GCN circ. 40168) and of the X-ray afterglow by Swift-XRT (Page et al., GCN circ. 40173), we observed the GRB field with the two Las Cumbres Observatory Global Telescope network (LCOGT) 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Siding Spring Observatory (Australia) in the SDSS u, g, r, and i filters. The observations started at 2025-04-19 11:20:00 UTC, about 8.84 hours after the SVOM trigger, with simultaneous observations in the r and i filters followed by simultaneous observations in the u and g filters. An uncatalogued source is detected in the four filters at the position of the optical afterglow reported first by Ocelotl López et al. (GCN circ. 40169), that is consistent with the Swift-XRT position (Page et al., GCN circ. 40176) and with other optical detections reported by Xin et al. (GCN circ. 40170), Zheng et al. (GCN circ. 40171), Kumar et al. (GCN circ. 40172), Thakur et al. (GRB redshift of z = 0.845, GCN circ. 40174), Lipunov et al. (GCN circ. 40179), Odeh et al. (GCN circ. 40180), Perley and Bochenek (GCN circ. 40181), and Pankov et al. (GCN circ. 40182). We measure the following magnitudes, calibrated against SDSS DR16 (Ahumada et al. 2020, ApJS, 249, 3A) stars, that are not corrected for Galactic extinction: Date | UT start | mag | error | filter | exposure time (sec) | ------------------------------------------------------------------------ 2025-04-19 11:20:00 19.15 0.07 i 300 2025-04-19 11:20:03 19.40 0.06 r 300 2025-04-19 11:45:15 20.13 0.17 u 300 2025-04-19 11:45:32 19.76 0.09 g 300 This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF). View this GCN Circular online at https://gcn.nasa.gov/circulars/40183. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38208] GRB 250419A: Mondy and AbAO Optical Observations
by GCN Circulars 20 Apr '25

20 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40182 SUBJECT: GRB 250419A: Mondy and AbAO Optical Observations DATE: 25/04/20 10:26:54 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), R. Ya. Inasaridze (AbAO) report on behalf of IKI-GRB-FuN: We observed the field of a soft long GRB 250419A detected by far by SVOM (Wang et al., GCN 40168), and Swift (Page et al., GCN 40111; Page et al., GCN 40176) at the redshhift of z = 0.845 (Thakur et al., GCN 40174) with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy), and the 0.7-meter AS-32 telescope of the Abastumani Astrophysical Observatory (AbAO). The R-band observations began on 2025-04-19 at 15:21:16 UT, i.e. ~0.55 days since trigger at Mondy. The optical counterpart (López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Thakur et al., GCN 40174; Lipunov et al., GCN 40179; Odeh et al., GCN 40180; Perley & Bochenek, GCN 40181) is detected in the stacked image from both telescopes. The preliminary photometry is as follows: Date UTstart Exptime t-T0 Filter OT Err UL Telescope (s) (mid, days) (3sigma) 2025-04-19 15:21:16 21*120 0.55052 R 19.68 0.05 22.2 AZT-33IK 2025-04-19 17:15:36 76*60 0.64172 R 19.72 0.25 20.2 AS-32 Ref. stars USNO-B1.0 RA Dec R2 202.4329 7.0165 15.18 202.3871 7.0378 16.79 The photometry is based on nearby USNO-B1.0 stars (R2 magnitudes) and has not been corrected for the Galactic extinction View this GCN Circular online at https://gcn.nasa.gov/circulars/40182. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38207] GRB 250419A: Liverpool Telescope observations
by GCN Circulars 20 Apr '25

20 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40181 SUBJECT: GRB 250419A: Liverpool Telescope observations DATE: 25/04/20 07:27:45 GMT FROM: Daniel Perley at Liverpool JMU <d.a.perley(a)ljmu.ac.uk> D. A. Perley and A. Bochenek (LJMU) report: We obtained imaging observations of the SVOM-detected GRB250419A (Wang et al., GCN 40168) with IO:O on the Liverpool Telescope on the night of 2025-04-19 between 22:02 and 22:26 UT. 6x100s exposures were acquired in both SDSS r-band and SDSS i-band. We clearly detect the optical counterpart (e.g. Ocelotl López et al., GCN 40169; Xin et al., GCN 40170) at the following magnitudes, calibrated using PanSTARRS secondary standards: MJD dt filter mag +/- unc 60784.91810 0.814 r 19.96 +/- 0.06 60784.92664 0.822 i 19.76 +/- 0.06 View this GCN Circular online at https://gcn.nasa.gov/circulars/40181. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38206] GRB 250419A: AKO Optical Afterglow Detection
by GCN Circulars 19 Apr '25

19 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40180 SUBJECT: GRB 250419A: AKO Optical Afterglow Detection DATE: 25/04/19 19:19:16 GMT FROM: Mohammad Odeh at Al Khatim Observatory M44 <mshodeh(a)gmail.com> Mohammad Odeh (Al-Khatim Observatory, AKO, operated by the International Astronomical Center in Abu Dhabi, UAE), and Shaikha Alshamsi, and Nidhal Guessoum (American University of Sharjah, UAE), report: We observed the field of GRB 250419A detected by SVOM (Wang et al., GCN 40168), using our 0.36m f/7.7 robotic telescope. The observation session began on 19 April 2025 at 15:49 UT and continued until 18:48 UT, with a midpoint at 17:18 UT, approximately 14.8 hours after the trigger. We obtained multiple 180-second exposures using the Ic filter. The optical afterglow was clearly detected at: R.A. (J2000): 13:29:37.30 Dec. (J2000): +07:02:27.7 Our detection is consistent with the results of (López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Lipunov et al., GCN 40179). The following observation was calculated using the Atlas catalogue as a reference: ---------------------------------------------------------------------------- - ObsTime (mid), Exposure (sec), Filter, Mag ---------------------------------------------------------------------------- - 2025-04-19T17:18:06Z, 57 x 180s (stacked), Ic, 18.7 +/- 0.16 ---------------------------------------------------------------------------- - The magnitude is not corrected for galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40180. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38205] GRB 250419A: MASTER optical afterglow observation
by GCN Circulars 19 Apr '25

19 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40179 SUBJECT: GRB 250419A: MASTER optical afterglow observation DATE: 25/04/19 17:43:59 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, A.Kuznetsov, G.Antipov, V.Topolev, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Chasovnikov, Ya.Kechin, V.Senik, K. Labzina, D.Vlasenko, E.Gorboskoy(Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (OAFA), A.Sosnovskij (Crao RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), R.Rebolo (The Instituto de Astrofisica de Canarias), D.Buckley (SAAO), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro AstrophysicsObservatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru,Lipunov et al., 2010, Advances in Astronomy, v. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the SVOM Alert 250419.10 (trigger No 1745029772,13h 29m 32.88s , +07d 05m 09.6s, R=0.1525, Wang et al. GCN 40168, Ocelotl López et al. GCN40169, Xin etl al. GCN40170) 3960 sec after trigger time at 2025-04-19 03:35:32 UT, with upper limit up to 19.9 mag. The observations began at zenith distance = 39 deg. The sun altitude is -66.0 deg. The galactic latitude b = 68 deg., longitude l = 330 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2847195 We obtained the following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment 3991 | 2025-04-19 03:35:32 | MASTER-OAFA | (13h 29m 02.64s , +07d 04m 50.6s) | C | 60 | 19.7 | 5446 | 2025-04-19 03:59:47 | MASTER-OAFA | (13h 28m 54.60s , +07d 03m 09.9s) | C | 60 | 19.7 | 6895 | 2025-04-19 04:23:56 | MASTER-OAFA | (13h 29m 35.13s , +07d 25m 23.4s) | C | 60 | 19.6 | 6955 | 2025-04-19 04:23:56 | MASTER-OAFA | (13h 29m 35.12s , +07d 25m 23.4s) | C | 180 | 19.9 | Coadd 8383 | 2025-04-19 04:48:45 | MASTER-OAFA | (13h 29m 28.53s , +07d 25m 00.4s) | C | 60 | 19.5 | 9666 | 2025-04-19 05:10:08 | MASTER-OAFA | (13h 29m 34.89s , +07d 26m 24.5s) | C | 60 | 19.4 | 10159 | 2025-04-19 05:18:20 | MASTER-OAFA | (13h 29m 31.07s , +07d 26m 26.7s) | C | 60 | 19.5 | Filter C is a clear (unfiltred) band. There is MASTER OT J132937.28+070227.8 since 2025-04-19 03:35:32 with m_OT=18.0 (unfiltered, Lipunov et al. 2010, 2019, 2022, 2023) up to 2025-04-19 05:18:20UT at SVOM VT position (GCN 40170 Xin et al.) The reduction will be continued View this GCN Circular online at https://gcn.nasa.gov/circulars/40179. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38204] Fermi-LAT Gamma-ray Observations of IceCube-250416A
by GCN Circulars 19 Apr '25

19 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40178 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-250416A DATE: 25/04/19 16:52:22 GMT FROM: Simone Garrappa at Weizmann Institute of Science <simone.garrappa(a)weizmann.ac.il> S. Garrappa (Weizmann Institute of Science), C. Bartolini (INFN Bari), S. Buson (DESY, Univ. of Wuerzburg) and L. Pfeiffer (Univ. of Wuerzburg) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC250416A neutrino event (GCN 40153) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 2025-04-16 at 18:32:14.97 (T0) with J2000 position RA = 83.1 (+0.57, -0.58) deg, Decl. = 15.64 (+0.49, -0.5) deg 90% PSF containment (J2000). No cataloged gamma-ray sources are found within the 90% IC250416A localization error (4FGL-DR4; The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC250416A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC250416A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 3.1 e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), < 7.2e-09 (<1.2e-07) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this source, the Fermi-LAT contact person is S. Garrappa (simone.garrappa at weizmann.ac.il). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/40178. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38203] GRB 250407A: rest-frame energetics from Konus-Wind observation
by GCN Circulars 19 Apr '25

19 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40177 SUBJECT: GRB 250407A: rest-frame energetics from Konus-Wind observation DATE: 25/04/19 14:12:21 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: Assuming the spectrum and the observer-frame energetics of the very bright GRB 250407A (GCN 40104) measured by Konus-Wind (GCN 40121); the redshift z=1.36 (Schneider et al., GCNs 40175); and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014); we estimate the burst isotropic energy release E_iso to (7.86 ± 0.20)x10^53 erg, the isotropic peak luminosity L_iso to (1.66 ± 0.06)x10^54 erg/s, the rest-frame peak energy of the time-integrated spectrum Ep,i,z to (1530 ± 110) keV, and the rest-frame peak energy at the peak of the emission Ep,p,z to (1970 ± 250) keV. With the obtained estimates, GRB 250407A is among 10 most luminous (and 50 most energetic) GRBs detected by Konus-Wind. The burst is consistent with 68% prediction bands for both 'Amati' and 'Yonetoku' relations derived for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB250407_T56895/GRB250407A_rest_frame.pdf 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/40177. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38202] GRB 250419A: Swift-XRT localisation
by GCN Circulars 19 Apr '25

19 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40176 SUBJECT: GRB 250419A: Swift-XRT localisation DATE: 25/04/19 13:15:36 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> K.L. Page, P.A. Evans (U. Leicester) and J.A. Kennea (PSU) report on behalf of the Swift-XRT team: The XRT afterglow of the SVOM/ECLAIRs-detected burst GRB 250419A, reported in GCN Circ. 40173, is located at a position of RA, Dec = 202.40554, 7.03987 which is equivalent to RA (J2000): 13h 29m 37.33s Dec (J2000): +07d 02' 23.5" with an uncertainty of 3.8 arcsec (radius, 90% confidence). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40176. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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