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

[vsnet-grb-info 38286] EP250427a: Einstein Probe detection of a fast X-ray transient
by GCN Circulars 27 Apr '25

27 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40257 SUBJECT: EP250427a: Einstein Probe detection of a fast X-ray transient DATE: 25/04/27 09:34:46 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.Wang (PMO, CAS), D. Y. Li (NAO, CAS), Y. Q. Zhao (USTC, PRIC), J. H. Wu (GZHU), Y, Liu (NAO, CAS) behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250427a (GCN Notice ID 01709135324). The WXT position of the source is R.A. = 277.281 deg, DEC = 7.570 deg (J2000) with an uncertainty of 2.0 arcmin in radius (90% C.L. statistical and systematic). A preliminary analysis of the EP-WXT data shows that the transient began at 2025-04-27T03:38:45(UTC) (before which the satellite was in the SAA region, and the real start time might be earlier than the value reported here) and lasted for about 180s, with a peak flux of 2 x 10^-8 erg/cm^2/s. The averaged WXT spectrum can be fitted by an absorbed power law model with a photon index of 1.70 (+0.36, -0.34) and a column density of 3.92 (+0.14, -0.13) x 10^21 cm^-2. The unabsorbed 0.5-4 keV flux is about 1.96 (+0.31, -0.23) x 10^-9 erg/cm^2/s. A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed about 5 hours after the WXT detection. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 277.2746 deg, DEC = 7.5639 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. The contact TA of EP250427a is Y. Wang. Please contact him via email wangyun(a)pmo.ac.cn if needed. 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/40257. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38285] IceCube Alert 250426.74: Global MASTER-Net observations report
by GCN Circulars 27 Apr '25

27 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40256 SUBJECT: IceCube Alert 250426.74: Global MASTER-Net observations report DATE: 25/04/27 00:27:01 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-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 250426.74 (trigger No 52432631,19h 45m 04.08s , +20d 41m 27.6s, R=0.56) errorbox 23060 sec after notice time and 23122 sec after trigger time at 2025-04-27 00:10:20 UT, with upper limit up to 17.5 mag. The observations began at zenith distance = 76 deg. The sun altitude is -61.8 deg. The galactic latitude b = -2 deg., longitude l = 58 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2853923 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 23152 | 2025-04-27 00:10:20 | MASTER-SAAO | (19h 42m 54.59s , +20d 09m 14.4s) | C | 60 | 17.5 | 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/40256. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38284] GRB 250424A: Swift-BAT refined analysis
by GCN Circulars 26 Apr '25

26 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40255 SUBJECT: GRB 250424A: Swift-BAT refined analysis DATE: 25/04/26 22:48:38 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250424A (trigger #1306404) (Cenko, et al., GCN Circ. 40224). The BAT ground-calculated position is RA, Dec = 217.528, -35.025 deg which is RA(J2000) = 14h 30m 06.7s Dec(J2000) = -35d 01' 30.6" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 39%. The mask-weighted BAT light curve of the burst (began during a slew) shows a faint precursor emission followed by a bright main pulse. T90 (15-350 keV) is 19.03 +- 1.06 sec (estimated error including systematics), with the T90 starting at T0-20.76 sec due to the slew-delayed T0. The time-averaged spectrum from T-38.75 to T+262.67 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.54 +- 0.13, and Epeak of 106.5 +- 33.7 keV (chi squared 47.05 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 3.2 +- 0.1 x 10^-05 erg/cm2 and the 1-sec peak flux measured from T-15.38 sec in the 15-150 keV band is 47.0 +- 1.3 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.79 +- 0.03 (chi squared 58.54 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1306404 View this GCN Circular online at https://gcn.nasa.gov/circulars/40255. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38283] IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 26 Apr '25

26 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40254 SUBJECT: IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/04/26 19:17:00 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-04-26 at 17:44:58.16 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_BRONZE alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 2.2610 events per year due to atmospheric Backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/140843_52432631.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-04-26 Time: 17:44:58.16 UT RA: 296.37 (+0.53/-0.50 deg 90% PSF containment) J2000 Dec: 20.7 (+0.52/-0.52 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/40254. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38282] IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 26 Apr '25

26 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40253 SUBJECT: IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/04/26 19:16:27 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-04-26 at 17:44:58.16 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_BRONZE alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 2.2610 events per year due to atmospheric Backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/140843_52432631.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-04-26 Time: 17:44:58.16 UT RA: 296.37 (+0.53/-0.50 deg 90% PSF containment) J2000 Dec: 20.7 (+0.52/-0.52 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/40253. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38281] GRB 250424A: SVOM/GRM observation of a long burst
by GCN Circulars 26 Apr '25

26 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40252 SUBJECT: GRB 250424A: SVOM/GRM observation of a long burst DATE: 25/04/26 13:30:39 GMT FROM: zhangjinpeng(a)ihep.ac.cn SVOM/GRM team: Jin-Peng Zhang, Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Jean-Luc Atteia (IRAP), Olivier Godet (IRAP), Stéphane Schanne (CEA), Frédéric Daigne (IAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 250424A (SVOM trigger reference: sb25042401) at 2025-04-24T06:52:08.000 (T0). This burst was also detected by Swift (Cenko et al., GCN 40224), AstroSat CZTI (Harsha et al., GCN 40231), Konus-Wind (Ridnaia et al., GCN 40243) and EIRSAT-1 GMOD (McKenna et al., GCN 40249). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90 of 18.8 +1.0/-1.0 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250424A.png In addition, the position of this burst, as determined by Swift (Cenko et al., GCN 40224, RA: 217.50010 deg, DEC: -35.02493 deg, Error: 1.9 arcseconds), is located at about 63.7 degrees from the SVOM optical axis, and outside the ECLAIRs field of view. The time-averaged spectrum from T0-5 to T0+18 s is best fitted by Band function. The alpha is -1.14 +/- 0.06, the beta is -2.44 +/- 0.08, and the cutoff energy, parameterized as Epeak, is 89 +/- 5 keV. The event fluence (10-1000 keV) in this time interval is (6.63 +/- 0.12)E-05 erg/cm^2. With a redshift of 0.310 (Saccardi et al., GCN 40228), GRB 250424A is consistent with Type II GRBs in the 'Amati' relation diagram, as shown at: https://www.bursthub.cn//admin/static/grb250424A_amati.png 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: Jin-Peng Zhang (IHEP) (zhangjinpeng(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/40252. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38280] GRB 250424A: PRIME near-infrared detection
by GCN Circulars 26 Apr '25

26 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40251 SUBJECT: GRB 250424A: PRIME near-infrared detection DATE: 25/04/26 00:30:37 GMT FROM: O. Guiffreda at UMD <oriogui(a)umd.edu> M. Elkabir (U Rome), O. Guiffreda (UMD), J. Durbak (UMD), N. Passaleva (U Rome), E. Troja (U Rome), A. S. Kutyrev (NASA/GSFC), S. B. Cenko (NASA/GSFC) Following the Swift BAT detection (GCN 40224), we observed the transient field in J and H filters with PRIME ~12 hours after the initial Swift detection. At the position of the optical counterpart reported by Swift UVOT (GCN 40244), we detect an uncatalogued source in both J and H band. Using nearby VISTA Hemispherical Survey (VHS) for preliminary calibration we derive the following magnitudes and limits, not corrected for Galactic extinction: |Filter | Mag(AB) | |-------|---------------| |J | 18.8 +/- 0.06 | |H | 19.2 +/- 0.05 | 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/40251. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38279] GRB 250424A: WINTER J-band detection
by GCN Circulars 25 Apr '25

25 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40250 SUBJECT: GRB 250424A: WINTER J-band detection DATE: 25/04/25 20:51:47 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> Benjamin Schneider (LAM), Geoffrey Mo (MIT), Tomas Ahumada (Caltech), Viraj Karambelkar (Caltech), Danielle Frostig (CfA), Robert Stein (UMD), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the GRB 250424A (Cenko et al., GCN 40224; Harsha et al., GCN 40231; Ridnaia et al., GCN 40243) in the near-infrared with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations started on 2025-04-24 at 07:33:24 UT (40.92 min after the Swift trigger) and consisted of 15 exposures of 120 s in the J-band. In the stacked image, we detect the optical counterpart reported by Cenko et al., GCN 40224; Brivio et al., GCN 40225; Becerra et al., GCN 40226; Saccardi et al., GCN 40228; de Wet et al., GCN 40229; Ducoin et al., GCN 40230; Turpin et al., GCN 40240, Dutton et al., GCN 40241; Siegel et al., GCN 40244. The preliminary AB magnitude derived for that source is: J = 18.1 +/- 0.2 The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565) The photometric calibration was performed using nearby stars from the 2MASS catalog and the magnitude is not corrected for Galactic extinction. WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research. View this GCN Circular online at https://gcn.nasa.gov/circulars/40250. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38278] GRB 250424A: EIRSAT-1 GMOD Detection
by GCN Circulars 25 Apr '25

25 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40249 SUBJECT: GRB 250424A: EIRSAT-1 GMOD Detection DATE: 25/04/25 20:36:05 GMT FROM: Caimin McKenna at University College Dublin <caimin.mckenna(a)ucdconnect.ie> C. McKenna, P. McDermott, D. Murphy, C. de Barra, A. Ulyanov, G. Finneran, G. Corcoran, L. Cotter, A. Empey, J. Fisher, F. Gibson Kiely, J. Thompson, D. McKeown, A. Martin-Carrillo, L. Hanlon, S. McBreen, on behalf of the EIRSAT-1 team: EIRSAT-1 reports the detection of the long gamma-ray burst GRB 250424A by the Gamma-ray Module (GMOD) instrument, which was also detected by Swift-BAT (GCN [40224](https://gcn.nasa.gov/circulars/40224)) Calet/CGBM (Trigger No. 1429512582), AstroSat CZTI (GCN [40231](https://gcn.nasa.gov/circulars/40231)) and Konus-Wind (GCN [40243](https://gcn.nasa.gov/circulars/40243)) The GMOD detection was made starting at 2025-04-24 06:52:12.6 UTC. The GMOD light curve for GRB 250424A, with 1.2s binning, shows a long, smooth, single pulse, consistent with other observations. The spacecraft location at time of detection was 23.407 S, 123.088 W and an altitude of 402.9 km. The light curve for this event as measured by GMOD can be found here: https://grb.eirsat1.ie/250424A/250424A_LC_onboard_preliminary.png EIRSAT-1 is Ireland’s first satellite (Doyle et al. Proceedings of the 4th SSEA, 2022). It is a 2U CubeSat and carries onboard a number of experiments including the Gamma-Ray Module (GMOD), a novel, compact, gamma-ray detector (Murphy et al, Experimental Astronomy, 53, 961–990, 2022). GMOD consists of a 25 mm × 25 mm × 40 mm Cerium Bromide scintillator coupled to SiPMs and is designed to detect gamma-ray bursts in the ~ 60 keV - 1.5 MeV range. EIRSAT-1 was developed in University College Dublin with support from ESA’s Fly Your Satellite! programme and was launched on 1st December 2023. View this GCN Circular online at https://gcn.nasa.gov/circulars/40249. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38277] IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 25 Apr '25

25 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40248 SUBJECT: IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/04/25 14:19:46 GMT FROM: Jessie Thwaites at IceCube/U Wisc-Madison <thwaites(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-250416A (https://gcn.nasa.gov/circulars/40153) in a time range of 1000 seconds centered on the alert event time (2025-04-16 18:23:54.970 UTC to 2025-04-16 18:40:34.970 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-250416A. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-250416A is 1.4e-01 GeV cm^-2 in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 2e+02 GeV and 1e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-04-15 18:32:14.970 UTC to 2025-04-17 18:32:14.970 UTC). In this case, we report a p-value of 0.39, consistent with no significant excess of track events. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-250416A is 1.6e-01 GeV cm^-2 in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/40248. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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