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

[vsnet-grb-info 40580] SVOM trigger sb25102702/GRB 251027A is not a GRB
by GCN Circulars 28 Oct '25

28 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42495 SUBJECT: SVOM trigger sb25102702/GRB 251027A is not a GRB DATE: 25/10/28 00:05:44 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Y. H.Cheng (YNU), Y. F. Liang (PMO), M. Brunet (IRAP), D. Turpin (CEA), report on behalf of the SVOM mission team: At 2025-10-27T09:38:17 SVOM issued an alert with burst-id: sb25102702. The following circular(s) have been published regarding this event: GCN 42471, 42480, 42481, 42486. After reprocessing the data with the full telemetry, this trigger is no longer considered as an astrophysical source but is due to coding noise from the Crab in the field of view. We apologize for any inconvenience this may have caused. The Burst Advocate (BA) on shift for this alert is Yehao Cheng: yhcheng(a)mail.ynu.edu.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/42495. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40579] IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42494 SUBJECT: IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/10/27 22:10:59 GMT FROM: Yuhua Yao at IceCube/UW-Madison <yyao255(a)icecube.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-251025A (https://gcn.nasa.gov/circulars/42436) in a time range of 1000 seconds centered on the alert event time (2025-10-25 13:39:33.261 UTC to 2025-10-25 13:56:13.261 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-251025A. We report a p-value of 1.00 in this time window. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.4e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251025A 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 (2025-10-24 13:47:53.261 UTC to 2025-10-26 13:47:53.261 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.6e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251025A 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/42494. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40578] GRB 251025B: Swift-XRT confirmation of fading
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42493 SUBJECT: GRB 251025B: Swift-XRT confirmation of fading DATE: 25/10/27 20:42:45 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 reobserved the X-ray afterglow of GRB 251025B (Hussein et al., GCN Circ. 42437, Beardmore et al., GCN Circ. 42245), gathering a further 2.6 ks of exposure from T0+131 ks to T0+154 ks. The X-ray source is detected but has faded significantly, from 0.30 +/- 0.02 ct/sec to 0.009 (+0.003, -0.002) ct/sec (0.3-10 keV), further confirming its identity as the afterglow of this GRB. The best-fitting power-law decay index is 0.95 (+0.15, -0.12). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42493. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40577] GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42492 SUBJECT: GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations DATE: 25/10/27 20:37:15 GMT FROM: soroush shakeri at Iranian National Observatory (INO) - Isfahan University of Technology (IUT) <soroush.physic(a)gmail.com> **Authors: INO340 Transient Follow-up Team** (H. G. Khosroshahi (INO), S. Shakeri (IUT/INO), H. Altafi (INO/IUT), S. Karimi Mianrudi (IUT), Parisa Hashemi (IUT), H. Torkzadeh (IUT), Reza Rezaei (SUT) and Yu Wang (ICRANet). We report optical follow-up observations of the long-duration **GRB 251013C**, detected by the Fermi/GBM team (GCN [42221](https://gcn.nasa.gov/circulars/42221?view=index&query=GRB+251013C&st…) at 2025-10-13 17:39:41 UT, and subsequently observed by SVOM and Swift/XRT. We observed the field of GRB 251013C with **3.4 m Telescope of Iranian National Observatory** ([INO340](https://ino.org.ir/en/)) by using SDSS g, r, and i filters on 2025 October 13, 15, and 16 (UT). We detected the source at the following position R.A. (J2000.0): 23 03 16 Dec.(J2000.0): -00 12 21 Our first observation was done at 20:36:20 UT on October 13, corresponding to ~10,578 s after the trigger of the Fermi/GBM, and the observation extended to ~2.17 days post-trigger. Photometric calibration was carried out using nearby reference stars from Pan-STARRS and SDSS catalogs. The afterglow shows a consistent fading trend typical of long GRB afterglows and a slight brightening in the second day, with magnitudes decreasing from i = 16.3 ± 0.018 → 21.61 ± 0.34, r = 16.63 ±0.20 → 21.99 ± 0.25, and g = 16.75 ± 0.017→ 22.44 ± 0.16. The deepest stacked images (exp:500s) from the third night reached g = 22.44 ± 0.16 mag. The optical images [ GRB 251013C - Filter-r - 13 Oct](https://www.dropbox.com/scl/fi/5104th21jqrydd9box07q/grb251013C13oct.j… [GRB 251013C - Filter-r - 15 Oct](https://www.dropbox.com/scl/fi/dx9iwokwdc2k2s2bqjz2z/grb251013C15oct.j… **We thank the INO340 technical and scientific staff**, M. Bidar, A. Javadi, A. Farhang, H. Shalchian, R. Shomali, R. Ravanmehr, H. Jenab, S. M. Mohajer, H. Sadeghi, M. Rostamian, A. Behnam, A. Karimzadeh, T. Shokatpour, R. Mirzaei, H. Alirezaei, S. Masoudieh. View this GCN Circular online at https://gcn.nasa.gov/circulars/42492. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40576] GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42491 SUBJECT: GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf DATE: 25/10/27 20:04:15 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne (U. Leicester), C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/GBM-detected burst GRB 251026B, collecting 2.0 ks of Photon Counting (PC) mode data between T0+116.7 ks and T0+122.7 ks, centred on the tentative GOTO optical counterpart candidate (GCN Circ. 42470). No X-ray sources have been detected consistent with the estimated 3-sigma GOTO error region (0.8 arcsec). The 3-sigma upper limit in the field ranges from ~0.004 to ~0.005 ct s^-1, corresponding to a 0.3-10 keV observed flux of 1.7e-13 to 2.1e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum). The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021872. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42491. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40575] GRB 251025C: Glowbug gamma-ray detection
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42490 SUBJECT: GRB 251025C: Glowbug gamma-ray detection DATE: 25/10/27 19:37:00 GMT FROM: richard.s.woolf.civ(a)us.navy.mil R. Woolf, C.C. Cheung, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 251025C, which was also detected by Fermi GBM (GCN 42449), CALET (GCN 42467), and AstroSat CZTI (GCN 42469). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-25 23:08:38.104 with a duration of 22.5 s and a total significance of about 46.8 sigma. The light curve comprises an initial fast rise/decay component in the T0 to T0+5s window, followed by secondary emission with slow exponential decay extending to T0+22.5s. Note that data from ~T0 to T0+1.5s and ~T0+3s to T0+5.5s suffered from deadtime in various detectors. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS, and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42490. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40574] Fermi-LAT Gamma-ray Observations of IceCube-251025A
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42489 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-251025A DATE: 25/10/27 17:51:55 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 IC251025A neutrino event (GCN 42436) 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 25-10-25 at 13:47:53.26 UTC (T0) with J2000 position RA = 145.63 (+0.88, -0.88) deg, Decl. = 15.06 (+0.65, -0.62) deg 90% PSF containment (J2000). No cataloged gamma-ray sources are found within the 90% IC251025A 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 IC251025A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC251025A best-fit position, the >100 MeV flux upper limit (95% confidence) is <2.8e-10 ph cm^-2 s^-1 for ~17-years (2008-08-04 / T0), <2.8e-09 (<4.6e-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/42489. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40573] GRB 251023B: Swift-UVOT Upper Limits
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42488 SUBJECT: GRB 251023B: Swift-UVOT Upper Limits DATE: 25/10/27 17:38:43 GMT FROM: noelklin(a)umbc.edu Swift-UVOT has performed follow-up observations of the EP-detected burst GRB 251023B (Wu et al. GCN 42415), collecting 1.7 ks of observations between T0+6.6 ks and T0+26.9 ks. No source was detected in the UVOT data at the position of the optical afterglow (Mandarakas et al., 42404; He at al., GCN 42418; Adami et al., 42421; Méndez et al. 42424). 3-sigma upper limits (AB) using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) are: Filter T_start(s) T_stop(s) Exp(s) Mag U 6573 26943 1737 >21.92 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.416 in the direction of the burst (Schlegel et al. 1998). We note that in the first snapshot (1531.80 s worth of data), the optical afterglow's position landed on a UVOT detector patch of small scale sensitivity inhomogeneity. In the U-band this can cause a source's flux to appear 5-16% lower than it actually is. The above limits are not corrected for this. See https://swift.gsfc.nasa.gov/analysis/uvot_digest/sss_check.html for more information. View this GCN Circular online at https://gcn.nasa.gov/circulars/42488. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40572] Konus-Wind detection of GRB 251022A
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42487 SUBJECT: Konus-Wind detection of GRB 251022A DATE: 25/10/27 17:16:14 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: The long GRB 251022A (Fermi-GBM detection: The Fermi GBM team, GCN 42380; Mukherjee & Meegan, GCN 42410; Fermi-LAT detection: Di Lalla et al., GCN 42384; SVOM/GRM observation: Ren et al., GCN 42484) triggered Konus-Wind (KW) at T0=81287.312 s UT (22:34:47.312). The burst consists of multiple emission pulses in the interval from T0-35 s to T0+90; the total duration of the burst is ~125 s. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB251022_T81287/ As observed by Konus-Wind, the burst had a fluence of (4.14 ± 0.71)x10^-5 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 23.168 s, of (1.09 ± 0.36)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+90.368 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -1.37 (-0.08,+0.07), the high energy photon index beta = -2.06 (-0.22,+0.13), the peak energy Ep = 178 (-38,+80) keV, chi2 = 96/97 dof. The spectrum near the peak count rate (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.71 (-0.42,+0.80), the high energy photon index beta = -2.13 (-0.84,+0.24), the peak energy Ep = 161 (-56,+84) keV, chi2 = 91/97 dof. 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/42487. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40571] GRB 251027A: Swift-XRT observations
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42486 SUBJECT: GRB 251027A: Swift-XRT observations DATE: 25/10/27 16:36:26 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected source GRB 251027A, collecting 1.6 ks of Photon Counting (PC) mode data between T0+4.5 ks and T0+12 ks after the trigger. We have detected 2 sources. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 2 uncatalogued X-ray sources * 0 known X-ray sources Uncatalogued X-ray sources -------------------------- Source 1 (SWIFT J062052.1+114644): ================================== RA (J2000.0): 95.2175 = 06 20 52.20 Dec (J2000.0): +11.7792 = +11 46 45.1 Error: 7.5 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 5.8 arcmin from the SVOM/ECLAIRs position. Mean rate: (5.4 [+2.7, -2.0])e-3 ct s^-1 Mean flux: (1.90 [+0.95, -0.72])e-10 erg cm^-2 s^-1 Peak rate: (5.4 [+2.7, -2.0])e-3 ct s^-1 Peak flux: (1.90 [+0.95, -0.72])e-10 erg cm^-2 s^-1 ECF: 3.52e-08 erg cm^-2 ct^-1 assuming NH=1.86e+24 cm^-2, gamma=-3.00 determined from a spectral fit. XMM UL: 2.1e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is 2.2-sigma above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `NVSS J062052+114645' is 0.1" away. There are 4 2MASS objects within the source's 3-sigma error radius. Source 3 (SWIFT J062105.2+112959): ================================== RA (J2000.0): 95.2720 = 06 21 05.28 Dec (J2000.0): +11.4998 = +11 29 59.3 Error: 8.8 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 12.3 arcmin from the SVOM/ECLAIRs position. Mean rate: (5.7 [+3.5, -2.5])e-3 ct s^-1 Mean flux: (2.4 [+1.5, -1.1])e-13 erg cm^-2 s^-1 Peak rate: (5.7 [+3.5, -2.5])e-3 ct s^-1 Peak flux: (2.4 [+1.5, -1.1])e-13 erg cm^-2 s^-1 XMM UL: 3.3e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. There are 5 2MASS objects within the source's 3-sigma error radius. All fluxes are 0.3-10 keV, observed. 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-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/SVOM/SVOM_FIELD00046. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42486. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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