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

[vsnet-grb-info 37998] GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
by GCN Circulars 31 Mar '25

31 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39979 SUBJECT: GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew DATE: 25/03/31 17:36:04 GMT FROM: Samuele Ronchini at PSU <sjs8171(a)psu.edu> Samuele Ronchini (PSU), James DeLaunay (PSU), Aaron Tohuvavohu (Caltech), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report: Swift/BAT did not localize GRB 250331D onboard (T0: 2025-03-31T05:49:17 UTC, Fermi GCN 39961). The Fermi notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The burst occurred during a Swift slew. The imaging is performed using BatAnalysis tools (Parsotan et al. 2025 [https://arxiv.org/abs/2502.00278](https://arxiv.org/abs/2502.00278)). A confident location is found for the burst with SNR of 11.6 The BAT position is RA, Dec = 48.52543, 62.30596 deg which is RA(J2000) = 03h 14m 06.10s Dec(J2000) = +62d 18’ 21.5″ with an estimated uncertainty of 5 arcmin. This position is consistent with the Ferm/GBM localization (GCN 39961). XRT and UVOT follow-up has been requested. Results of follow-up observations will be reported in future circulars. GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/39979. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37997] Konus-Wind detection of GRB 250327B
by GCN Circulars 31 Mar '25

31 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39978 SUBJECT: Konus-Wind detection of GRB 250327B DATE: 25/03/31 16:40:41 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 250327B (SVOM-ECLAIRs detection: Bouchet et al., GCN 39888) was detected by Konus-Wind (KW) in the waiting mode at T0 = T0(ECLAIRs) = 76287 s UT (21:11:27). A Bayesian block analysis of the KW waiting mode data in the 20-1200 keV band reveals a ~20 sigma count rate increase in the interval from ~T0-12 s to ~T0+424 s. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250327B/ The total burst fluence is 2.31(-0.22,+0.26)x10^-5 erg/cm^2, and the 2.944 s peak energy flux, measured from T0+85 s, is 2.43(-0.52,+0.55)x10^-7 erg/cm^2. (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst, measured from T0-12 s to T0+424 s, can be described by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.11(-0.17,+0.21) and Ep = 212(-38,+48) keV. The spectrum near the peak count rate, measured from T0+76 s to T0+91 s, can be described by a CPL model with alpha = -0.82(-0.31,+0.43) and Ep = 203(-49,+64) keV. Assuming the redshift z=3.035 (Malesani et al., GCN 39893) 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 following rest-frame parameters: the isotropic energy release E_iso is 4.78(-0.45,+0.54)x10^53 erg, the peak luminosity L_iso is 2.03(-0.44,+0.46)x10^52 erg/s, the rest-frame peak energy of the time-averaged spectrum Ep,i,z is 856(-152,+195) keV and the spectrum near the maximum count rate Ep,p,z is 818(-198,+257) keV. With the obtained estimates, GRB 250327B is inside 68% prediction band for the 'Amati' and 90% prediction band for 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/GRB250327B/GRB250327B_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/39978. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37996] GRB 250331C: Enhanced Swift-XRT position
by GCN Circulars 31 Mar '25

31 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39977 SUBJECT: GRB 250331C: Enhanced Swift-XRT position DATE: 25/03/31 16:38:10 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 1624 s of XRT Photon Counting mode data and 2 UVOT images for GRB 250331C, 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 = 80.95619, +33.06347 which is equivalent to: RA (J2000): 05h 23m 49.49s Dec (J2000): +33d 03' 48.5" with an uncertainty of 2.2 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/39977. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37995] IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 31 Mar '25

31 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39976 SUBJECT: IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/03/31 16:15:15 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-250330A (https://gcn.nasa.gov/circulars/39943) in a time range of 1000 seconds centered on the alert event time (2025-03-30 08:22:46.320 UTC to 2025-03-30 08:39:26.320 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-250330A. 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-250330A is 1.3e-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 (2025-03-29 08:31:06.320 UTC to 2025-03-31 08:31:06.320 UTC). In this case, we report a p-value of 1.00, 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-250330A is 1.5e-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/39976. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37994] LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
by GCN Circulars 31 Mar '25

31 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39975 SUBJECT: LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume DATE: 25/03/31 15:48:32 GMT FROM: David Cook at Caltech/IPAC-NED <dcook(a)ipac.caltech.edu> David O. Cook (Caltech/IPAC), Rick Ebert (Caltech/IPAC), George Helou (Caltech/IPAC), Joseph M. Mazzarella (Caltech/IPAC), Marion Schmitz (Caltech/IPAC), and Leo Singer (NASA/GSFC) On behalf of the NASA/IPAC Extragalactic Database (NED) Team. We spatially cross-matched the LVK S250331o-3-Initial sky localization with the NED Local Volume Sample (NED-LVS; Cook et al. 2023), which is a subset of NED with a redshift or redshift-independent distance less than 1000 Mpc. We find 582 galaxies within the 90% containment volume, and we list here the top 20 galaxies sorted by the joint probability of the 3D localization and the WISE W1 luminosity (an observable proxy for stellar mass). For the full or top 20 list of galaxies in the 90% volume go either to the NED Gravitational Wave Followup service at https://ned.ipac.caltech.edu/uri/NED::GWF/ or click on the following links: Full List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250331o/3 Top 20 List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250331o/3/20 The NED-GWF service provides downloadable galaxy lists and visualizations for candidate host galaxies. For each GW alert, these products are automatically generated and made available within minutes to expedite efficient electromagnetic follow-up observations. The NED top 20 list is sorted by the joint probability of the 3D localization and the WISE W1 luminosity, but users can sort on additional pre-computed prioritization metrics (star formation rate, P_3D * P_SFR; and specific star formation rate, P_3D * P_sSFR; etc.) which are available via downloading the entire galaxy list inside the event's probability volume. | objname| ra| dec|objtype| DistMpc|DistMpc_unc| m_NUV| m_NUV_unc| m_Ks| m_Ks_unc| m_W1| m_W1_unc| P_3D|P_3D_LumW1| |-------------------------|--------------|--------------|-------|-----------|-----------|------------|------------|------------|------------|------------|------------|--------|----------| |WISEA J020352.96+300418.6| 30.97068| 30.07186| G| 450.96| null| null| null| 13.417| 0.135| 10.147| 0.006|2.21e-06| 3.99e-08| |WISEA J020524.84+300356.4| 31.35354| 30.06568| G| 653.76| null| null| null| 13.537| 0.143| 12.061| 0.009|1.69e-06| 1.10e-08| | 3C 059 NED01| 31.75919| 29.51278| G| 510.64| 2.89| 18.553| 0.047| 12.531| 0.068| 11.452| 0.006|1.47e-06| 1.02e-08| |WISEA J020815.86+330236.7| 32.06612| 33.04354| G| 528.82| null| null| null| 12.409| 0.098| 12.307| 0.010|1.99e-06| 6.80e-09| |WISEA J020728.78+301402.8| 31.86992| 30.23411| G| 488.46| null| 22.228| 0.345| 12.899| 0.118| 12.205| 0.008|2.12e-06| 6.76e-09| |WISEA J021035.33+303608.5| 32.64721| 30.60238| G| 569.79| null| null| null| 12.895| 0.117| 12.315| 0.013|1.64e-06| 6.45e-09| |WISEA J020735.81+301139.9| 31.89924| 30.19442| G| 697.62| null| null| null| 13.258| 0.120| 12.206| 0.008|9.86e-07| 6.42e-09| |WISEA J020447.91+305422.6| 31.19964| 30.90630| G| 421.78| null| null| null| 12.281| 0.097| 11.835| 0.007|1.92e-06| 6.41e-09| |WISEA J021036.53+303612.4| 32.65223| 30.60347| G| 607.46| null| null| null| 13.762| 0.178| 12.435| 0.008|1.55e-06| 6.19e-09| |WISEA J020031.78+285022.0| 30.13243| 28.83945| G| 548.45| null| null| null| 13.274| 0.142| 12.152| 0.008|1.32e-06| 5.57e-09| |WISEA J020247.16+295941.4| 30.69650| 29.99484| G| 557.31| null| 20.629| 0.118| 13.505| 0.133| 12.951| 0.014|2.62e-06| 5.47e-09| |WISEA J020311.55+300127.5| 30.79816| 30.02432| G| 512.31| 0.08| null| null| 13.071| 0.101| 12.808| 0.010|2.61e-06| 5.24e-09| |WISEA J021613.00+340524.3| 34.05421| 34.09010| G| 677.00| null| null| null| 13.485| 0.160| 11.789| 0.007|5.73e-07| 5.16e-09| |WISEA J020959.78+325524.0| 32.49910| 32.92334| G| 589.92| 0.10| 21.761| 0.336| 13.738| 0.179| 13.027| 0.012|2.33e-06| 5.10e-09| |WISEA J020619.97+294730.7| 31.58324| 29.79188| G| 507.55| 0.07| null| null| 12.533| 0.104| 12.599| 0.020|2.12e-06| 5.09e-09| |WISEA J020633.75+303828.7| 31.64066| 30.64131| G| 429.37| null| null| null| 12.181| 0.101| 12.041| 0.008|1.73e-06| 4.95e-09| | VI Zw 139| 30.40470| 30.82735| G| 509.90| 0.06| null| null| 13.148| 0.120| 12.551| 0.009|1.91e-06| 4.80e-09| |WISEA J020659.62+303130.8| 31.74842| 30.52523| G| 462.52| null| 21.179| 0.192| 13.405| 0.144| 12.477| 0.009|2.02e-06| 4.49e-09| |WISEA J020919.83+314709.5| 32.33265| 31.78598| G| 656.06| 0.12| null| null| 14.209| 0.268| 13.409| 0.016|2.34e-06| 4.46e-09| |WISEA J020626.94+302913.7| 31.61227| 30.48715| G| 672.91| 0.08| null| null| 13.829| 0.091| 13.152| 0.013|1.69e-06| 4.27e-09| Table 1: Top 20 galaxies in NED-LVS that fall in the 90% probability volume for S250331o sorted by the joint probability of 3D position and WISE W1 luminosity (P_3D * P_LumW1). Galaxy is the NED preferred name. RA and Dec are the Equatorial coordinates in degrees (J2000). Objtype is the object type of the galaxy candidate. Distance is the distance to the galaxy in Mpc. m_NUV and mErr_NUV are the apparent magnitude and error from GALEX. m_Ks and mErr_Ks are the apparent magnitude and error from 2MASS. m_W1 and mErr_W1 are the apparent magnitude and error from AllWISE. P_3D is the probability that the galaxy is in the volume given the distance of GW event. P_3D_LumW1 is the joint probability within the volume weighted by the WISE1 luminosity of the galaxy (P_3D * P_LumW1). View this GCN Circular online at https://gcn.nasa.gov/circulars/39975. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37993] GRB 250331B: Enhanced Swift-XRT position
by GCN Circulars 31 Mar '25

31 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39974 SUBJECT: GRB 250331B: Enhanced Swift-XRT position DATE: 25/03/31 15:22:51 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 824 s of XRT Photon Counting mode data and 1 UVOT images for GRB 250331B, 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 = 71.37215, +43.81257 which is equivalent to: RA (J2000): 04h 45m 29.32s Dec (J2000): +43d 48' 45.2" with an uncertainty of 3.6 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/39974. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37992] GRB 250320C : SVOM detection of a burst through offline search
by GCN Circulars 31 Mar '25

31 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39973 SUBJECT: GRB 250320C : SVOM detection of a burst through offline search DATE: 25/03/31 14:25:24 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet (IRAP), S. Schanne (CEA), J. Atteia (IRAP), C. W. Wang, Y. Huang (IHEP), O. Godet (IRAP), D. Turpin (CEA) report on behalf of the SVOM team: The SVOM/ECLAIRs telescope detected a transient source, labelled GRB 250320C, starting at 2025-03-20T17:39:40.0 UTC (Tb), through an offline search with the event-by-event data downloaded through the X-band ground station. The burst was detected by several methods and within several energy ranges and timescales. The best detection is obtained by the image trigger with a signal-to-noise ratio of 7.7 within 4-120 keV over a time window of 40.96 seconds starting at 2025-03-20T17:40:39.4 UTC. The lightcurve shows a first episode, starting at Tb, composed of a single peak that lasted around 5s and a second episode 1 minute later composed of multiple peaks, that lasted around 40s. The localization of the source is RA, Dec = 170.930, 40.677 (J2000). The uncertainty on this position is 11.6 arcminutes at 90% C.L. We notice the presence of several quasars in this error box, among which the closest is SDSS J112340.66+404052.0 located at 0.5 arcmin. However the lightcurve is more suggestive of a GRB. 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: Marius Brunet (IRAP) marius.brunet(a)irap.omp.eu. 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/39973. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37991] LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
by GCN Circulars 31 Mar '25

31 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39972 SUBJECT: LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources DATE: 25/03/31 14:04:07 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans (U. Leicester), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), S.B. Cenko (NASA/GSFC), R.A.J. Eyles-Ferris (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), A.A. Breeveld (UCL-MSSL), S. Campana (INAF-OAB), J.J. Delaunay (PSU), M. De Pasquale (University of Messina), S. Dichiara (PSU), P. D’Avanzo (INAF-OAB), A. D’Aì (INAF-IASFPA) , V. D’Elia (ASI-SSDC & INAF-OAR), C. Gronwall (PSU), D. Hartmann (Clemson University), N. Klingler (NASA-GSFC / UMBC / CRESST II), N.P.M. Kuin (UCL-MSSL), S. Laha (NASA/GSFC), S.R. Oates (U. Birmingham), J.P. Osborne (U. Leicester), P. O’Brien (U. Leicester), M.J. Page (UCL-MSSL), G. Raman (PSU) S. Ronchini (PSU), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (U Tor Vergata, INAF) report on behalf of the Swift team: Swift has carried out 97 observations of the LVK error region for the GW trigger S250328ae convolved with the 2MPZ catalogue (Bilicki et al. 2014, ApJS, 210, 9), using the 'BAYESTAR' GW localisation map. As this is a 3D skymap, galaxy distances were taken into account in selecting which ones to observe. The observations currently span from 3.0 ks to 38 ks after the LVK trigger, and the XRT has covered 5.3 deg^2 on the sky (corrected for overlaps). This covers 68% of the probability in the 'ligo-skymap-from-samples' skymap, and 72% after convolving with the 2MPZ galaxy catalogue, as described by Evans et al. (2016, MNRAS, 462, 1591). We have detected 34 X-ray sources. Each source is assigned a rank of 1-4 which describes how likely it is to be related to the GW trigger, with 1 being the most likely and 4 being the least likely. The ranks are described at https://www.swift.ac.uk/ranks.php. We have found: * 0 sources of rank 1 * 0 sources of rank 2 * 34 sources of rank 3 * 0 sources of rank 4 RANK 3 sources ============== These are uncatalogued X-ray sources, however they are not brighter than previous upper limits, so do not stand out as likely counterparts to the GW trigger. | Source ID | RA | Dec | Err90 | Detection Flag | | S250328ae_X1 | 09h 37m 34.26s | +11d 00' 47.1" | 8.3" | POOR | | S250328ae_X2 | 09h 37m 40.59s | +11d 15' 09.3" | 5.4" | REASONABLE | | S250328ae_X3 | 09h 38m 01.16s | +11d 14' 02.6" | 6.5" | POOR | | S250328ae_X5 | 09h 38m 05.54s | +11d 24' 32.5" | 6.5" | POOR | | S250328ae_X6 | 09h 37m 57.28s | +11d 18' 05.4" | 6.5" | POOR | | S250328ae_X8 | 09h 38m 05.52s | +11d 19' 00.3" | 9.1" | POOR | | S250328ae_X9 | 09h 38m 34.55s | +11d 14' 28.5" | 6.4" | POOR | | S250328ae_X10 | 09h 38m 37.34s | +11d 16' 12.5" | 9.9" | POOR | | S250328ae_X11 | 09h 38m 13.89s | +11d 16' 52.4" | 9.5" | POOR | | S250328ae_X12 | 09h 37m 35.17s | +10d 47' 58.5" | 6.6" | POOR | | S250328ae_X13 | 09h 39m 29.53s | +11d 47' 43.2" | 6.0" | POOR | | S250328ae_X14 | 09h 39m 57.31s | +12d 06' 58.4" | 8.7" | POOR | | S250328ae_X15 | 09h 39m 31.81s | +12d 06' 34.6" | 7.9" | POOR | | S250328ae_X16 | 09h 40m 10.28s | +11d 53' 17.1" | 6.7" | POOR | | S250328ae_X17 | 09h 39m 48.52s | +11d 55' 48.6" | 7.4" | POOR | | S250328ae_X18 | 09h 39m 45.99s | +11d 54' 42.0" | 7.5" | POOR | | S250328ae_X19 | 09h 39m 39.79s | +11d 54' 32.3" | 6.6" | POOR | | S250328ae_X20 | 09h 39m 23.21s | +11d 57' 42.7" | 6.6" | POOR | | S250328ae_X21 | 09h 39m 41.64s | +11d 53' 24.9" | 13.1" | POOR | | S250328ae_X22 | 09h 39m 45.64s | +11d 51' 32.9" | 9.1" | POOR | | S250328ae_X23 | 09h 39m 28.69s | +11d 59' 35.2" | 8.2" | POOR | | S250328ae_X24 | 09h 39m 51.34s | +11d 52' 24.6" | 6.2" | POOR | | S250328ae_X25 | 09h 40m 08.46s | +11d 55' 52.5" | 8.9" | POOR | | S250328ae_X26 | 09h 39m 51.33s | +11d 55' 00.9" | 6.6" | POOR | | S250328ae_X27 | 09h 39m 34.55s | +12d 01' 50.9" | 7.2" | POOR | | S250328ae_X28 | 09h 40m 17.23s | +11d 54' 47.3" | 9.7" | POOR | | S250328ae_X29 | 09h 39m 31.19s | +11d 54' 35.1" | 8.4" | POOR | | S250328ae_X30 | 09h 39m 39.91s | +12d 04' 29.3" | 15.4" | POOR | | S250328ae_X31 | 09h 38m 40.15s | +11d 14' 00.3" | 5.7" | POOR | | S250328ae_X32 | 09h 38m 17.68s | +11d 19' 25.6" | 13.5" | POOR | | S250328ae_X33 | 09h 39m 18.34s | +11d 59' 40.6" | 8.9" | POOR | | S250328ae_X34 | 09h 39m 52.80s | +11d 54' 16.5" | 8.0" | POOR | | S250328ae_X35 | 09h 39m 34.91s | +12d 05' 56.6" | 9.0" | POOR | | S250328ae_X36 | 09h 39m 29.20s | +12d 02' 51.1" | 10.7" | POOR | For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2, and photon index (Gamma)=1.7, unless otherwise stated. The results of the XRT automated analysis, including details of the sources listed above, are online at https://www.swift.ac.uk/LVC/S250328ae This circular is an official product of the Swift XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39972. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37990] GRB 250329B: Swift-XRT confirmation of fading
by GCN Circulars 31 Mar '25

31 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39971 SUBJECT: GRB 250329B: Swift-XRT confirmation of fading DATE: 25/03/31 12:43:42 GMT FROM: P.A. Evans at U. Leicester <pae9(a)leicester.ac.uk> P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has carried out a second observation of GRB 250329B. The X-ray source reported by Beardmore et al. (GCN Circ. 39939) has faded, with a decay index of 1.19 (+0.47, -0.28). We therefore confirm that it is the afterglow of this GRB. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39971. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37989] GRB 250330A: VLT/FORS2 Afterglow Detection
by GCN Circulars 31 Mar '25

31 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39970 SUBJECT: GRB 250330A: VLT/FORS2 Afterglow Detection DATE: 25/03/31 12:35:19 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Rosa L. Becerra (U Rome), Yu-Han Yang (U Rome), Simone Dichiara (PSU), Muskan Yadav (U Rome), Eleonora Troja (U Rome), Lei Hu (CMU) and Roberto Ricci (U Rome) report on behalf of the ERC BHianca team: We reobserved the field of GRB 250330A (Cenko et al., GCN 39938) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began at T+19.8 hours after the trigger and were carried out in the R filter at an average seeing of 1.0" and airmass about 2.5. A comparison to our first epoch (Becerra et al., GCN 39941) reveals a fading source within the XRT enhanced position (Evans et al., GCN 39947), located at RA, Dec (J2000) = 16:51:47.01, -86:52:51.85. We estimate a preliminary magnitude of R~23.2 AB mag at 1.25 h post-trigger, calibrated using nearby stars from the SkyMapper Southern Survey (SMSS) Fourth Data Release (DR4) catalog (Onken et al., 2024) and not corrected for Galactic extinction. 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/39970. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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