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[vsnet-grb-info 40370] Konus-Wind detection of GRB 251007A
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42297 SUBJECT: Konus-Wind detection of GRB 251007A DATE: 25/10/15 17:55:01 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 251007A (Swift-BAT detection: Ambrosi et al., GCN 42146; Laha et al., GCN 42186; Glowbug detection: Cheung et al., GCN 42151; CALET-GBM detection: Yoshida et al., GCN 42156; AstroSat CZTI detection: Salunke et al., GCN 42167; Insight-HXMT detection: Wang et al., GCN 42183; SVOM/GRM detection: Yu et al., GCN 42184) triggered Konus-Wind at T0=70671.956 s UT (19:37:51.956). The burst light curve shows a multipeaked structure which starts at ~T0-44.6 s and has a total duration of ~66.4 s. The emission is seen up to ~4 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB251007_T70671/ As observed by Konus-Wind, the burst had a fluence of 3.89(-0.15,+0.16)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+0.656 s, of 7.08(-0.94,+0.95)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+24.832 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.09(-0.06,+0.06) and Ep = 395(-27,+31) keV (chi2 = 108/98 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.6 (chi2 = 108/97 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+8.448 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model with alpha = -1.20(-0.07,+0.07) and Ep = 436(-41,+50) keV (chi2 = 98/81 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.4 (chi2 = 96/80 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/42297. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40369] Fermi Gamma-ray Burst Monitor trigger 782237334/251015673 is not a GRB
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42296 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 782237334/251015673 is not a GRB DATE: 25/10/15 17:53:14 GMT FROM: Suman Bala at USRA <sumanbala2210(a)gmail.com> S. Bala (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 782237334/251015673 at 16:08:49.43 UT on 15 October 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to distant particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/42296. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40368] GRB 251013C, GCN Circular 42267, errata corrige
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42295 SUBJECT: GRB 251013C, GCN Circular 42267, errata corrige DATE: 25/10/15 17:50:14 GMT FROM: I. Peretto at MarSEC (Marana Space Explorer Center) <ricerca(a)marsec.org> Ivo Peretto (MarSEC, Marana Space Explorer Center, Marana Di Crespadoro, VI, Italy) Member of: UAI/SSV - Unione Astrofili Italiani/Sezione Stelle Variabili, GRB section. AAVSO (American Association Variable Stars Observers). We report our photometry analysis: HJD Rc Mag Err ------------------------------------- 2460962.4676701734 17.581 0.09 Reference: https://www.marsec.org/ The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42295. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40367] GRB 251013C: detection of a radio counterpart at 15.5GHz
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42294 SUBJECT: GRB 251013C: detection of a radio counterpart at 15.5GHz DATE: 25/10/15 16:27:02 GMT FROM: Lauren Rhodes at McGill <lauren.rhodes(a)mcgill.ca> Lauren Rhodes (McGill/TSI), Andrew Hughes (Oxford), Rob Fender (Oxford), Dave Green (Cambridge), Dave Titterington (Cambridge) report: We observed the field of the afterglow candidate GRB 251013C (GCN 42221) with the Arcminute Microkelvin Imager Large-Array (AMI-LA) at 15.5 GHz beginning at UT 19:27:08.0 on 14-Oct-2025 for a total of 4 hours. The flux standard 3c286 was used to calibrate the bandpass response and flux scale of the AMI-LA and J2320+0513 was used as an interleaved complex gain calibrator. We detected a point source with a peak flux density of 0.34 +/- 0.08 mJy/beam with a position of RA = 23h03m20.5+/- 0.2s Dec = -00d12'26+/- 9" Further observations are planned. We thank the staff at the Mullard Radio Astronomy Observatory for carrying out these observations and operating the AMI-LA. View this GCN Circular online at https://gcn.nasa.gov/circulars/42294. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40366] GRB 251015A: Fermi GBM Final Real-time Localization
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42293 SUBJECT: GRB 251015A: Fermi GBM Final Real-time Localization DATE: 25/10/15 16:19:34 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 16:08:49 UT on 15 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251015A (trigger 782237334.425736 / 251015673). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 355.1, Dec = -56.1 (J2000 degrees, equivalent to J2000 23h 40m, -56d 06'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 167.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251015673/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251015673/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251015673/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42293. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40365] GRB 251013C: SVOM/ECLAIRs refined analysis
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42292 SUBJECT: GRB 251013C: SVOM/ECLAIRs refined analysis DATE: 25/10/15 15:52:54 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> H. Yang, M. Brunet, O. Godet (IRAP), B. Hubert (CEA), F. Piron (LUPM), N. A. Rakotondrainibe, C. Adami (LAM) Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 251013C (SVOM burst-id sb2525101311, GCN 42222) detected at T0 = 2025-10-13T17:39:42, which was also detected by SVOM/GRM and Fermi/GBM (GCN 42221). The burst that triggered ECLAIRs consists of a single peak, with a typical fast-rising and exponential-decay profile, starting at T0-0.4 s and lasting about 30 s in the 4-120 keV energy band. The time-averaged spectrum from the peak (T0-0.4 s to T0+30 s) in the 4-120 keV energy range is well fitted by a power-law model with a photon index of 1.59 +/-0.03. With this model, the total 4-120 keV fluence is (1.95 + 0.02/-0.03)e-06 erg/cm^2 . All the quoted errors are at the 68% confidence level. The Space-based multi-band astronomical 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 CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Hui Yang (IRAP) (hui.yang(a)irap.omp.eu) View this GCN Circular online at https://gcn.nasa.gov/circulars/42292. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40364] GRB 251013D: Swift-XRT observations
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42291 SUBJECT: GRB 251013D: Swift-XRT observations DATE: 25/10/15 14:47:57 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> D.N. Burrows (PSU), S. Lanava (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), S. Campana (INAF-OAB), S. Dichiara (PSU) 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 and Swift/BAT-GUANO detected burst GRB 251013D, collecting 4.9 ks of Photon Counting (PC) mode data between T0+71.0 ks and T0+83.7 ks. Two uncatalogued X-ray sources have been detected within the estimated 3-sigma BAT-GUANO error region (394 arcsec), however none of them is above the RASS limit or shows definitive signs of fading. Therefore, at the present time we cannot identify which, if any, is the afterglow. Details of these sources are given below: Source 1: RA (J2000.0): 46.8919 = 03h 07m 34.05s Dec (J2000.0): +8.7859 = +08d 47' 09.2" Error: 5.6 arcsec (radius, 90% conf.) Count-rate: (3.42 [+1.17, -0.97])e-3 ct s^-1 Distance: 37 arcsec from Fermi/GBM position. Flux: (1.83 [+1.3, -1.1])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 2: RA (J2000.0): 46.9703 = 03h 07m 52.86s Dec (J2000.0): +8.8156 = +08d 48' 56.0" Error: 6.0 arcsec (radius, 90% conf.) Count-rate: (2.00 [+0.95, -0.74])e-3 ct s^-1 Distance: 331 arcsec from Fermi/GBM position. Flux: (3.4 [+6.2, -1.8])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV) Two uncatalogued sources were also detected too far from the GRB position to be likely afterglow candidates. 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/00021861. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42291. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40363] Swift Trigger 1404295: possible GRB 251015A
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42290 SUBJECT: Swift Trigger 1404295: possible GRB 251015A DATE: 25/10/15 14:44:43 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> N. J. Klingler (GSFC/UMBC/CRESSTII), R. Brivio (INAF-OAB), S. Dichiara (PSU), M. Ferro (INAF-OAB), R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL), A. Mei (INAF-OAB), K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sbarrato (INAF-OAB) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 14:17:23 UT, the Swift Burst Alert Telescope (BAT) triggered and located a possible GRB 251015A (trigger=1404295). Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 245.007, -54.853 which is RA(J2000) = 16h 20m 02s Dec(J2000) = -54d 51' 10" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 10 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 14:19:31.3 UT, 127.6 seconds after the BAT trigger. No source was detected in 877 s of promptly downlinked data. We are waiting for the full dataset to detect and localise the XRT counterpart. UVOT took a finding chart exposure of 150 seconds with the White filter starting 870 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of the BAT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. The 8'x8' region for the list of sources generated on-board covers 0.00% of the BAT error circle. No correction has been made for the large, but uncertain, extinction expected. Due to the marginal detection in the BAT image (6.53 sigma) and the lack of an XRT counterpart, we believe that this is most likely to be a noise fluctuation, but might be a GRB. Analysis of the complete downlinked dataset will be required to determine the reality of this event. Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu) Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/42290. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40362] GRB 251014B: Swift-XRT observations
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42289 SUBJECT: GRB 251014B: Swift-XRT observations DATE: 25/10/15 14:43:08 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> S. Lanava (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. D'Ai (INAF-IASFPA), S. Campana (INAF-OAB), A. Melandri (INAF-OAR), S. Dichiara (PSU), J.A. Kennea (PSU) 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, Swift/BAT-GUANO-detected burst GRB 251014B, collecting 4.5 ks of Photon Counting (PC) mode data between T0+49.9 ks and T0+73.1 ks. Three X-ray sources, of which two (Source 2 and Source 4) are uncatalogued, have been detected within the estimated 3-sigma Swift/BAT-GUANO error region (296 arcsec), however none of them is above the RASS limit or shows definitive signs of fading. Therefore, at the present time we cannot identify which, if any, is the afterglow. Details of these sources are given below: Source 2: RA (J2000.0): 14.5787 = 00h 58m 18.89s Dec (J2000.0): -35.5678 = -35d 34' 04.2" Error: 7.3 arcsec (radius, 90% conf.) Count-rate: (2.66 [+1.09, -0.87])e-3 ct s^-1 Distance: 66 arcsec from Fermi/GBM position. Flux: (6.0 [+2.5, -2.0])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 3: RA (J2000.0): 14.6936 = 00h 58m 46.46s Dec (J2000.0): -35.5767 = -35d 34' 36.2" Error: 7.9 arcsec (radius, 90% conf.) Count-rate: (1.52 [+0.90, -0.66])e-3 ct s^-1 Distance: 287 arcsec from Fermi/GBM position. Source 3 matches the position of the quasar [VV98] J005846.6-353444. Source 4: RA (J2000.0): 14.6178 = 00h 58m 28.28s Dec (J2000.0): -35.5331 = -35d 31' 59.2" Error: 6.2 arcsec (radius, 90% conf.) Count-rate: (1.87 [+0.98, -0.75])e-3 ct s^-1 Distance: 181 arcsec from Fermi/GBM position. Flux: (6.5 [+3.4, -2.6])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 4 is close to the 2MASS source J00582790-3531563 (5.4"). Another uncatalogued source (Source 1) was also detected, however this was too far from the GRB position to be the afterglow. 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/00021863. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42289. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40361] GRB 251014B: Swift/UVOT Upper Limits
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42288 SUBJECT: GRB 251014B: Swift/UVOT Upper Limits DATE: 25/10/15 14:32:04 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk> A.A. Breeveld (UCL-MSSL) and N. J. Klingler (GSFC/UMBC/CRESSTII) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251014B 49976 s after the Swift-BAT/GUANO trigger (Ronchini et al., GCN 42263). No new optical afterglow is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures binned is: Filter T_start(s) T_stop(s) Exp(s) Mag white 49976 73120 7974 >23.0 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.014 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42288. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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