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

[vsnet-grb-info 39733] EP250827b: SVOM/VT observation of AT 2025wkm
by GCN Circulars 03 Sep '25

03 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41667 SUBJECT: EP250827b: SVOM/VT observation of AT 2025wkm DATE: 25/09/03 05:04:52 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, Z. H. Yao, L. P. Xin, Y. L. Qiu, C. Wu, H. L. Li, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM performed a Target of Opportunity observation of EP250827b/AT 2025wkm (Schroeder et al., GCN 41635). SVOM/VT began observing the field at 2025-09-02T09:14:40 UTC, 6.12 days after the X-ray detection, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X-band data availible, the source consistent with AT 2025wkm (Schroeder et al., GCN 41635; Hall et al., GCN 41636; Sevilla & Ho, GCN 41639; Hall et al., GCN 41641; Eyles-Ferris & Starling, GCN 41655) was clearly detected in both VT_B and VT_R. However, the source in VT_R was contaminated by the blooming of bright star, so the magnitude of VT_B is: mid time (day) | exposure time (s) | band | mag (AB) | mag err ---------------|-------------------|------|----------|-------- 6.24 | 37*70 | VT_B | 19.81 | 0.03 Our photometry was not corrected for Galactic extinction. 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/41667. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39732] LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
by GCN Circulars 03 Sep '25

03 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41666 SUBJECT: LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data DATE: 25/09/03 04:23:58 GMT FROM: Kunal Mooley at NRAO,Caltech <kmooley(a)caltech.edu> Lauren Rhodes (McGill U.), Oleg Smirnov (Rhodes U. / SARAO), Kunal Mooley (IIT Kanpur, Caltech), Patrick Woudt (U. Cape Town) We reprocessed both MeerKAT S-band (3 GHz) datasets of the AT2025ulz (Stein et al., GCN 41414) field reported previously (Bruni et al. GCNs 41594, 41500) in the context of the subthreshold GW event S250818k (LVK Collaboration, GCNs 41437, 41440). Our reprocessing reveals that in both datasets, from Aug 28 (10 days post-GW-event) and Aug 21 (4 days post-GW-event), the source has a constant integrated flux density of ~90+/10 uJy. Thus, we do not find any evidence for radio variability. Further, the extended nature of the radio source indicates that the emission is host galaxy dominated. We caution all users of the SARAO Science Data Processor (SDP) continuum pipeline that the pipeline results must be carefully assessed before dissemination across the astronomical community. In the Aug 28 SDP images, there were large-scale artefacts, likely RFI-induced, that may be responsible for the excess flux measurement reported in GCN 41594. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. View this GCN Circular online at https://gcn.nasa.gov/circulars/41666. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39731] GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
by GCN Circulars 03 Sep '25

03 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41665 SUBJECT: GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare DATE: 25/09/03 04:11:08 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of GRB 250831A (SVOM trigger sb25083102; Xie et al., GCN 41614) starting at 09:32:33, 180 seconds after the burst. Observations were performed in 3 x 3 tiling mode, and a set of clear (roughly R) filter images were obtained. The first image covered the proposed flare star G 272-61 (Wu et al., GCN 41615; Magnani et al., GCN 41616; Xie et al., GCN 41618; Li et al., GCN 41654) was at 09:36:55, 442 seconds after the burst. Although the star was saturated in KAIT images, photometry with a large aperture clearly shows the magnitude decreased from 9.2 mag to 10.2 mag (faded by 1.0 mag) about 2 hours later. This is similar to the light curve reported by SVOM/VT, confirming this event is due to a stellar flare. View this GCN Circular online at https://gcn.nasa.gov/circulars/41665. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39730] Fermi GRB 250902B: Global MASTER-Net observations report
by GCN Circulars 03 Sep '25

03 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41664 SUBJECT: Fermi GRB 250902B: Global MASTER-Net observations report DATE: 25/09/03 03:31:08 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) started inspect of the Fermi GRB 250902B ( Fermi GBM team, GCN 41660) errorbox 18838 sec after notice time and 18874 sec after trigger time at 2025-09-03 00:00:08 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 77 deg. The sun altitude is -59.1 deg. The galactic latitude b = -20 deg., longitude l = 208 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2983003 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 18905 | 2025-09-03 00:00:08 | MASTER-SAAO | (05h 20m 30.13s , -04d 32m 16.8s) | C | 60 | 17.4 | 18905 | 2025-09-03 00:00:08 | MASTER-SAAO | (05h 22m 16.39s , -04d 47m 44.4s) | C | 60 | 13.4 | 19743 | 2025-09-03 00:14:07 | MASTER-SAAO | (05h 20m 31.93s , -04d 32m 23.9s) | C | 60 | 17.7 | 19743 | 2025-09-03 00:14:07 | MASTER-SAAO | (05h 22m 18.01s , -04d 47m 48.8s) | C | 60 | 16.7 | 19962 | 2025-09-03 00:17:46 | MASTER-SAAO | (05h 27m 44.14s , -04d 30m 25.1s) | C | 60 | 17.8 | 19962 | 2025-09-03 00:17:46 | MASTER-SAAO | (05h 29m 30.52s , -04d 45m 52.0s) | C | 60 | 16.8 | 20055 | 2025-09-03 00:19:19 | MASTER-SAAO | (05h 35m 39.60s , -04d 30m 43.8s) | C | 60 | 18.0 | 20055 | 2025-09-03 00:19:19 | MASTER-SAAO | (05h 37m 26.17s , -04d 46m 09.6s) | C | 60 | 15.7 | 20368 | 2025-09-03 00:24:32 | MASTER-SAAO | (05h 20m 25.60s , -04d 32m 23.1s) | C | 60 | 17.8 | 20368 | 2025-09-03 00:24:32 | MASTER-SAAO | (05h 22m 12.33s , -04d 47m 48.4s) | C | 60 | 17.1 | 20590 | 2025-09-03 00:28:14 | MASTER-SAAO | (05h 27m 42.05s , -04d 30m 33.7s) | C | 60 | 17.8 | 20590 | 2025-09-03 00:28:14 | MASTER-SAAO | (05h 29m 28.33s , -04d 45m 56.0s) | C | 60 | 17.1 | 20814 | 2025-09-03 00:31:58 | MASTER-SAAO | (05h 35m 47.86s , -04d 30m 20.8s) | C | 60 | 17.9 | 20814 | 2025-09-03 00:31:58 | MASTER-SAAO | (05h 37m 33.96s , -04d 45m 44.0s) | C | 60 | 16.9 | 21125 | 2025-09-03 00:37:08 | MASTER-SAAO | (05h 20m 30.36s , -04d 31m 31.8s) | C | 60 | 17.8 | 21125 | 2025-09-03 00:37:08 | MASTER-SAAO | (05h 22m 17.39s , -04d 46m 55.0s) | C | 60 | 17.4 | 21217 | 2025-09-03 00:38:41 | MASTER-SAAO | (05h 27m 38.90s , -04d 32m 11.0s) | C | 60 | 17.8 | 21218 | 2025-09-03 00:38:41 | MASTER-SAAO | (05h 29m 25.88s , -04d 47m 33.9s) | C | 60 | 17.3 | 21436 | 2025-09-03 00:42:19 | MASTER-SAAO | (05h 35m 42.83s , -04d 30m 02.1s) | C | 60 | 18.1 | 21436 | 2025-09-03 00:42:19 | MASTER-SAAO | (05h 37m 29.66s , -04d 45m 25.2s) | C | 60 | 17.6 | 21623 | 2025-09-03 00:45:27 | MASTER-SAAO | (05h 28m 42.64s , -06d 25m 09.3s) | C | 60 | 17.8 | 21623 | 2025-09-03 00:45:27 | MASTER-SAAO | (05h 30m 29.96s , -06d 40m 32.5s) | C | 60 | 17.5 | 21717 | 2025-09-03 00:47:00 | MASTER-SAAO | (05h 36m 44.94s , -06d 23m 48.0s) | C | 60 | 18.3 | 21717 | 2025-09-03 00:47:00 | MASTER-SAAO | (05h 38m 32.18s , -06d 39m 10.9s) | C | 60 | 17.8 | 21811 | 2025-09-03 00:48:35 | MASTER-SAAO | (05h 20m 28.96s , -04d 31m 31.0s) | C | 60 | 17.8 | 21811 | 2025-09-03 00:48:35 | MASTER-SAAO | (05h 22m 16.10s , -04d 46m 53.7s) | C | 60 | 17.6 | 21905 | 2025-09-03 00:50:09 | MASTER-SAAO | (05h 27m 37.83s , -04d 32m 12.9s) | C | 60 | 17.8 | 21905 | 2025-09-03 00:50:09 | MASTER-SAAO | (05h 29m 24.93s , -04d 47m 35.3s) | C | 60 | 17.6 | 22202 | 2025-09-03 00:55:06 | MASTER-SAAO | (05h 21m 31.95s , -06d 24m 31.1s) | C | 60 | 17.9 | 22202 | 2025-09-03 00:55:06 | MASTER-SAAO | (05h 23m 19.48s , -06d 39m 55.5s) | C | 60 | 17.9 | 22295 | 2025-09-03 00:56:39 | MASTER-SAAO | (05h 35m 39.88s , -04d 30m 50.9s) | C | 60 | 18.2 | 22295 | 2025-09-03 00:56:39 | MASTER-SAAO | (05h 37m 26.70s , -04d 46m 15.3s) | C | 60 | 17.9 | 22481 | 2025-09-03 00:59:44 | MASTER-SAAO | (05h 28m 48.06s , -06d 25m 09.7s) | C | 60 | 18.0 | 22481 | 2025-09-03 00:59:44 | MASTER-SAAO | (05h 30m 35.49s , -06d 40m 34.0s) | C | 60 | 17.9 | 22579 | 2025-09-03 01:01:23 | MASTER-SAAO | (05h 36m 44.70s , -06d 25m 51.1s) | C | 60 | 18.6 | 22579 | 2025-09-03 01:01:23 | MASTER-SAAO | (05h 38m 32.64s , -06d 41m 14.1s) | C | 60 | 18.4 | 22672 | 2025-09-03 01:02:56 | MASTER-SAAO | (05h 20m 30.08s , -04d 32m 05.7s) | C | 60 | 18.0 | 22672 | 2025-09-03 01:02:56 | MASTER-SAAO | (05h 22m 17.93s , -04d 47m 28.7s) | C | 60 | 18.0 | 22765 | 2025-09-03 01:04:29 | MASTER-SAAO | (05h 27m 40.12s , -04d 30m 40.7s) | C | 60 | 18.0 | 22765 | 2025-09-03 01:04:29 | MASTER-SAAO | (05h 29m 27.84s , -04d 46m 03.6s) | C | 60 | 17.9 | 23049 | 2025-09-03 01:09:13 | MASTER-SAAO | (05h 21m 26.00s , -06d 25m 32.3s) | C | 60 | 18.0 | 23049 | 2025-09-03 01:09:13 | MASTER-SAAO | (05h 23m 14.50s , -06d 40m 55.7s) | C | 60 | 18.0 | 23143 | 2025-09-03 01:10:46 | MASTER-SAAO | (05h 35m 38.42s , -04d 29m 57.8s) | C | 60 | 18.2 | 23143 | 2025-09-03 01:10:46 | MASTER-SAAO | (05h 37m 26.26s , -04d 45m 21.1s) | C | 60 | 18.3 | 23236 | 2025-09-03 01:12:19 | MASTER-SAAO | (05h 28m 47.39s , -06d 25m 15.1s) | C | 60 | 17.9 | 23236 | 2025-09-03 01:12:19 | MASTER-SAAO | (05h 30m 35.79s , -06d 40m 38.5s) | C | 60 | 17.9 | 23329 | 2025-09-03 01:13:52 | MASTER-SAAO | (05h 36m 43.44s , -06d 25m 56.1s) | C | 60 | 18.5 | 23329 | 2025-09-03 01:13:52 | MASTER-SAAO | (05h 38m 31.77s , -06d 41m 19.5s) | C | 60 | 18.6 | 23422 | 2025-09-03 01:15:26 | MASTER-SAAO | (05h 29m 30.58s , -04d 47m 30.8s) | 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/41664. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39729] Fermi-LAT Gamma-ray Observations of IceCube-250831A
by GCN Circulars 02 Sep '25

02 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41663 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-250831A DATE: 25/09/02 19:46:44 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC250831A neutrino event (GCN 41620) 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 2025-08-31 at 18:00:45.82 UTC (T0) with J2000 position RA = 105.64 (+0.51, -0.48) deg, Decl. = 5.04 (+0.61, -0.50) deg 90% PSF containment (J2000). No cataloged gamma-ray sources are found within the 90% IC250831A 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 IC250831A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC250831A best-fit position, the >100 MeV flux upper limit (95% confidence) is <2.6e-10 ph cm^-2 s^-1 for ~17-years (2008-08-04 / T0), <1.6e-08 (<7.1e-08) 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 analysis, the Fermi-LAT contact person is L. Pfeiffer (leonard.pfeiffer at uni-wuerzburg.de). 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/41663. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39728] GRB 250902A: Fermi GBM Detection
by GCN Circulars 02 Sep '25

02 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41662 SUBJECT: GRB 250902A: Fermi GBM Detection DATE: 25/09/02 19:12:27 GMT FROM: sumanbala2210(a)gmail.com S. Bala (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 01:30:00.49 UT on 02 September 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250902A (trigger 778469405/250902062). The Fermi-GBM position was reported in GCN 41648 (Fermi GBM Team 2025). The angle from the Fermi LAT boresight is 78 degrees. The GBM light curve consists of a bright pulse with a duration (T90) of about 8.4 s (50-300 keV). The time-averaged spectrum from T0-1.0 to T0+17.4 s is best fit by Band function with a Band function with Epeak = 257 +/- 13 keV, alpha = -1.25 +/- 0.02, and beta = -2.31 +/- 0.1. A power law function with an exponential high-energy cutoff fits the spectrum equally well with a with power law index = -1.28 +/- 0.01 and Epeak = 294 +/- 10 keV. The event fluence (10-1000 keV) in this time interval is (3.06 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.5 s in the 10-1000 keV band is 43.5 +/- 0.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/41662. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39727] GRB 250901A: Swift/UVOT Upper Limit
by GCN Circulars 02 Sep '25

02 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41661 SUBJECT: GRB 250901A: Swift/UVOT Upper Limit DATE: 25/09/02 18:56:52 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250901A 2.6 ks after the SVOM/ECLAIRs trigger (Piron et al., GCN Circ. 41634). We do not detect any afterglow consistent with the XRT position (Osborne et al., GCN Circ. 41645) or optical position (Xin et al., GCN Circ. 41646; Malesani et al., GCN Circ. 41649). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag u 2629 4244 1589 >21.01 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.023 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/41661. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39726] GRB 250902B: Fermi GBM Final Real-time Localization
by GCN Circulars 02 Sep '25

02 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41660 SUBJECT: GRB 250902B: Fermi GBM Final Real-time Localization DATE: 25/09/02 18:56:35 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 18:45:34 UT on 2 Sep 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250902B (trigger 778531539.099344 / 250902782). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 82.3, Dec = -5.0 (J2000 degrees, equivalent to J2000 05h 29m, -5d 00'), with a statistical uncertainty of 1.4 degrees. The angle from the Fermi LAT boresight is 20.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250902782/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250902782/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250902782/… View this GCN Circular online at https://gcn.nasa.gov/circulars/41660. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39725] IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 02 Sep '25

02 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41659 SUBJECT: IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/09/02 15:58:24 GMT FROM: Alicia Mand at IceCube/UW-Madison <aemand(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-250831A (https://gcn.nasa.gov/circulars/41620) in a time range of 1000 seconds centered on the alert event time (2025-08-31 17:52:25.820 UTC to 2025-08-31 18:09:05.820 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-250831A. We report a p-value of 1.00 in this time window. 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-250831A 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 3e+02 GeV and 1e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-08-30 18:00:45.820 UTC to 2025-09-01 18:00:45.820 UTC). In this case, we report a p-value of 0.23, 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-250831A 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/41659. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39724] GRB 250830B: Swift-XRT afterglow detection
by GCN Circulars 02 Sep '25

02 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41658 SUBJECT: GRB 250830B: Swift-XRT afterglow detection DATE: 25/09/02 14:31:53 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), S. Lanava (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has conducted further observations of the field of the MAXI-detected burst GRB 250830B. The observations now extend from T0+11.1 ks to T0+223.0 ks and have a total exposure time of 6.0 ks. . The source previously reported, "Source 1", is fading with 2.5 sigma significance and thus is believed to be the GRB afterglow. Using 2349 s of PC mode data and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 105.74037, -64.85289 which is equivalent to: RA (J2000): 07h 02m 57.69s Dec(J2000): -64d 51' 10.4" with an uncertainty of 3.0 arcsec (radius, 90% confidence). This position is 2.3 arcmin from the EP position. The light curve can be modelled with a power-law decay with a decay index of alpha=0.43 (+0.15, -0.16). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.4 (+0.8, -0.5). The best-fitting absorption column is 1.5 (+6.0, -0.4) x 10^21 cm^-2, consistent with the Galactic value of 1.1 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.4 x 10^-11 (6.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.5 (+6.0, -0.4) x 10^21 cm^-2 Galactic foreground: 1.1 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 1.4 (+0.8, -0.5) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021858. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021858. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41658. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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