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[vsnet-grb-info 38399] GRB 250502A: Bassano Bresciano Observatory upper limit
by GCN Circulars 06 May '25

06 May '25

TITLE: GCN CIRCULAR NUMBER: 40370 SUBJECT: GRB 250502A: Bassano Bresciano Observatory upper limit DATE: 25/05/06 18:58:00 GMT FROM: Ulisse Quadri at Bassano Bresciano Observatory <osservatoriobassano(a)gmail.com> U.Quadri, L.Strabla and P.Madurini (Bassano Bresciano Astronomical Observatory) Members of: GRB/UAI - Gamma ray Burst section of Unione Astrofili Italiani. AAVSO - American Association of Variable Star Observers. GAC - Gruppo Astrofili Cremonesi. In a large … [View More]

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[vsnet-grb-info 38398] IceCube-250506A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 06 May '25

06 May '25

TITLE: GCN CIRCULAR NUMBER: 40369 SUBJECT: IceCube-250506A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/05/06 18:12:57 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-05-06 at 14:14:12.09 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the … [View More]

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[vsnet-grb-info 38397] IceCube Alert 250506.59: Global MASTER-Net observations report
by GCN Circulars 06 May '25

06 May '25

TITLE: GCN CIRCULAR NUMBER: 40368 SUBJECT: IceCube Alert 250506.59: Global MASTER-Net observations report DATE: 25/05/06 17:26:50 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,… [View More] 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the IceCube Alert 250506.59 (trigger No 73492707,07h 45m 48.00s , +35d 19m 26.4s, R=0.51) errorbox 9145 sec after notice time and 9189 sec after trigger time at 2025-05-06 16:47:21 UT, with upper limit up to 18.3 mag. Observations started at twilight. The observations began at zenith distance = 70 deg. The sun altitude is -11.2 deg. The galactic latitude b = 26 deg., longitude l = 185 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2862958 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 9220 | 2025-05-06 16:47:21 | MASTER-SAAO | (07h 45m 13.02s , +35d 13m 49.3s) | C | 60 | 17.2 | 9299 | 2025-05-06 16:48:41 | MASTER-SAAO | (07h 40m 43.94s , +35d 18m 38.4s) | C | 60 | 17.3 | 9378 | 2025-05-06 16:50:00 | MASTER-SAAO | (07h 50m 27.69s , +35d 17m 49.3s) | C | 60 | 17.4 | 9458 | 2025-05-06 16:51:19 | MASTER-SAAO | (07h 45m 10.27s , +35d 14m 19.7s) | C | 60 | 17.6 | 10259 | 2025-05-06 17:04:41 | MASTER-SAAO | (07h 40m 37.95s , +35d 19m 20.4s) | C | 60 | 18.2 | 10338 | 2025-05-06 17:06:00 | MASTER-SAAO | (07h 50m 33.38s , +35d 18m 23.3s) | C | 60 | 18.1 | 10418 | 2025-05-06 17:07:19 | MASTER-SAAO | (07h 45m 09.40s , +35d 12m 53.7s) | C | 60 | 18.3 | 10577 | 2025-05-06 17:09:58 | MASTER-SAAO | (07h 45m 12.90s , +35d 14m 31.9s) | C | 60 | 18.3 | 10894 | 2025-05-06 17:15:16 | MASTER-SAAO | (07h 40m 44.89s , +35d 18m 43.8s) | C | 60 | 18.2 | 10973 | 2025-05-06 17:16:35 | MASTER-SAAO | (07h 50m 27.54s , +35d 17m 46.4s) | C | 60 | 18.0 | 11053 | 2025-05-06 17:17:54 | MASTER-SAAO | (07h 45m 16.27s , +35d 13m 44.9s) | C | 60 | 18.1 | 11212 | 2025-05-06 17:20:33 | MASTER-SAAO | (07h 45m 12.65s , +35d 13m 41.6s) | C | 60 | 18.0 | 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/40368. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L… [View Less]

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[vsnet-grb-info 38396] GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
by GCN Circulars 06 May '25

06 May '25

TITLE: GCN CIRCULAR NUMBER: 40367 SUBJECT: GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis DATE: 25/05/06 16:17:44 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 250430A (Swift-BAT detection: Parsotan et al., GCN 40292; Moss et al., GCN 40356; EP-WXT detection: Wang et … [View More]al., GCN 40299) was detected by Konus-Wind (KW) in the waiting mode. A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band reveals a ~16 sigma count-rate increase in the interval from T0-0.581 s to T0+5.307 s, where T0 = T0(BAT) = 17:31:00.28 UT. The KW light curve of this burst is available at http://www.ioffe.ru/LEA/GRBs/GRB250430A/ To derive broad-band spectral parameters of this burst, we performed a joint spectral analysis of the Swift/BAT data (15-150 keV) and the KW 3-channel spectral data (20-1600 keV). A fit to the time-averaged spectrum, measured from T0-0.581 s to T0+5.307 s, by the Band GRB function results in alpha = -0.99(-0.31,+0.70), beta = -2.01(-0.39,+0.19), and Ep = 107(-44,+86) keV (chi2/dof= 57.7/59). The total burst fluence is 3.21(-0.92,+1.09)x10^-6 erg/cm^2, and the 64-ms peak energy flux, measured from T0+0.446 s, is 1.63(-0.50,+0.58)x10^-6 erg/cm^2. (both in the 20 keV - 10 MeV energy range). Assuming the redshift z=0.767 (Garnichey et al., GCN 40301) 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 5.26(-1.50,+1.78)x10^51 erg, the isotropic peak luminosity L_iso to 2.35(-0.72,+0.84)x10^51 erg/s, and the rest-frame peak spectral energy Ep,z to 189(-77,+151) keV. With the obtained estimates, GRB 250430A is inside 68% prediction bands for both the 'Amati' and the '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/GRB250430A/GRB250430A_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/40367. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L… [View Less]

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[vsnet-grb-info 38395] GRB 250506A: Xinglong 2.16m optical upper limit
by GCN Circulars 06 May '25

06 May '25

TITLE: GCN CIRCULAR NUMBER: 40366 SUBJECT: GRB 250506A: Xinglong 2.16m optical upper limit DATE: 25/05/06 16:04:35 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L. P. Xin, J. Zhen, J. Wang, H. L. Li, Y. L. Qiu, C. Wu, X. H. Han, Y. Xu, P. P. Zhang, Y. J. Xiao, L. Lan, W. J. Xie, J. S. Deng, J. Y. Wei (NAOC) report on behalf of SVOM follow-up team: We observed the field of GRB 250506A (Wang et al., GCN 40358; Maggi et al., GCN 40364; Fermi team GCN 4035). using the 2.16-… [View More]

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[vsnet-grb-info 38394] SVOM/sb25050601: EP-FXT observations
by GCN Circulars 06 May '25

06 May '25

TITLE: GCN CIRCULAR NUMBER: 40365 SUBJECT: SVOM/sb25050601: EP-FXT observations DATE: 25/05/06 15:18:15 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> M.H. Zhang, W. Chen (NAO, CAS), H. L. Peng (NNU), H.W. Pan (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation on SVOM/sb25050601 at 2025-05-06T04:26:39 (UTC), about 2 hours after the SVOM/ECLAIRs trigger (Wang et al., GCN #40358). Considering the improved ECLAIRs position (Maggi et … [View More]

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[vsnet-grb-info 38393] GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
by GCN Circulars 06 May '25

06 May '25

TITLE: GCN CIRCULAR NUMBER: 40364 SUBJECT: GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow DATE: 25/05/06 14:47:41 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> P. Maggi (ObAS), D. Götz (CEA), H. Goto (Kanazawa University/CEA), M. Moita (CEA), C. Plasse (CEA), F. Robinet (IJCLab), C. Van Hove (IJCLab) on behalf of the SVOM/MXT Team report: M. Brunet, S. Guillot (IRAP), S. Schanne (CEA) on behalf of the SVOM/ECLAIRs Team report: Using the full X … [View More]band dataset a corrected ECLAIRs position could be derived for GRB 250506A/sb25050601 (Wang et al., GCN 40358). The improved ECLAIRs position is RA=219.373, Dec=28.909 with a 90% c.l. of 6.4 arc min. The burst appeared very close to the Earth limb and only part of the burst signal was considered by the onboard processing, explaining the localization error. SVOM MXT observed the ECLAIRs error region starting at T0 = 2025-05-06T03:09:28.279 (46 min after trigger time Tb). MXT observed it during 5 orbits for a 10.9 ks effective exposure. Using the full X band dataset, we find an uncatalogued source. The source is fading with time and not detected after the fourth orbit (t+T0 > 23 ks). The best position is obtained from first orbit data (t+T0 < 2.5ks), at RA=219.267, Dec=28.8593 corresponding to: RA (J2000) = 14h37m04. Dec (J2000) = +28d51m34. with a statistical 90% C.L. radius of 32.5” to which a 35” systematic uncertainty is to be added in quadrature. The afterglow spectrum is modelled by an absorbed power law fading with time. The absorption column is NH = 3+/-1 x 1e21 /cm2 (90% C.L. uncertainties) and a photon index of 2.3 (+0.7/-0.6) in first orbit softening to 3.3 (+2.5/-1.2) in the second orbit. The average observed flux in the 0.3-8 keV band is 6.8 (+3.4/-2.2) x1e-11 erg/cm2/s during the first orbit and 1.4 (<2.7) x1e-11 erg/cm2/s during the second one. The ECLAIRs and MXT position are consistent, confirming that the MXT source is the afterglow of the GRB 250506A. This position corrects and supersedes the one reported by Wang et al. (GCN 40358). The active QSO detected by TRT (Liu et al., GCN 40360) and Swift XRT (Beardmore et al., GCN 40361) is thus unrelated to GRB 250506A. 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. MXT was developed jointly by CEA, CNES, University of Leicester, IJCLab and MPE. ECLAIRs was developed jointly by CNES, IRAP, APC and CEA. The Burst Advocate (BA) on shift for this burst is Chenwei Wang: cwwang(a)ihep.ac.cn Please contact the BA 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/40364. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L… [View Less]

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[vsnet-grb-info 38392] GRB 250506A: REM optical/NIR upper limits
by GCN Circulars 06 May '25

06 May '25

TITLE: GCN CIRCULAR NUMBER: 40363 SUBJECT: GRB 250506A: REM optical/NIR upper limits DATE: 25/05/06 14:25:25 GMT FROM: Matteo Ferro at INAF-OAB <matteo.ferro(a)inaf.it> M. Ferro, R. Brivio, P. D'Avanzo, M. G. Bernardini, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 250506A detected by SVOM/ECLAIRs (Wang et al., GCN 40358) and Fermi GBM (Fermi GBM team, GCN 40355; Sonawane et al., GCN 40362) with the REM 60 cm robotic telescope … [View More]

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[vsnet-grb-info 38391] GRB 250506A: Fermi GBM Observation
by GCN Circulars 06 May '25

06 May '25

TITLE: GCN CIRCULAR NUMBER: 40362 SUBJECT: GRB 250506A: Fermi GBM Observation DATE: 25/05/06 13:07:40 GMT FROM: Rushikesh Sonawane at IISER, TVM <rushikesh23(a)iisertvm.ac.in> R. Sonawane (IISER, TVM), S. Bala (USRA), and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 02:23:22.60 UT on 06 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250506A (trigger 768191007/250506100). which was also detected by SVOM/ECLAIRs (… [View More]

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[vsnet-grb-info 38390] GRB 250506A: Swift XRT observations and possible counterpart detection
by GCN Circulars 06 May '25

06 May '25

TITLE: GCN CIRCULAR NUMBER: 40361 SUBJECT: GRB 250506A: Swift XRT observations and possible counterpart detection DATE: 25/05/06 10:03:08 GMT FROM: P.A. Evans at U. Leicester <pae9(a)leicester.ac.uk> A.P. Beadmore, K.L. Page and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team, Swift-XRT has observed the location of the SVOM and Fermi-detected GRB 250506A (GCN Circs. 40355, 40358), gathering 1.7 ks of data between 1.5 ks and 13.7ks after the Fermi trigger. The … [View More]

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