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[vsnet-grb-info 40357] GRB 251014D: Swift-XRT afterglow detection
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42284 SUBJECT: GRB 251014D: Swift-XRT afterglow detection DATE: 25/10/15 10:20:16 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), S. Campana (INAF-OAB), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of GRB 251014D. We searched for X-ray sources in 2.9 ks of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 5.0 ks, obtained between T0+159.4 s and T0+22.3 ks. An uncatalogued X-ray source is detected within the estimated 3-sigma Swift-BAT error region (296 arcsec) and is fading with >3-sigma significance, and is therefore likely the GRB afterglow. Using 1351 s of PC mode data and 3 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 = 323.92080, -41.85533 which is equivalent to: RA (J2000): 21h 35m 40.99s Dec(J2000): -41d 51' 19.2" with an uncertainty of 3.4 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=1.71 (+0.12, -0.11). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.64 (+/-0.06). The best-fitting absorption column is 9.7 (+1.9, -1.8) x 10^20 cm^-2, in excess of the Galactic value of 2.1 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.1 x 10^-11 (4.6 x 10^-11) erg cm^-2 count^-1. A summary of the WT-mode spectrum is thus: Total column: 9.7 (+1.9, -1.8) x 10^20 cm^-2 Galactic foreground: 2.1 x 10^20 cm^-2 Excess significance: 6.8 sigma Photon index: 1.64 (+/-0.06) The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01404126. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/01404126. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42284. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40356] GRB 251013C: MAO/AZT-22 optical observations
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42283 SUBJECT: GRB 251013C: MAO/AZT-22 optical observations DATE: 25/10/15 09:38:38 GMT FROM: Yodgor Rajabov at UBAI <rajabov(a)astrin.uz> B.Abidkhanov, Y. Rajabov, O. Burkhonov, S. Ehgamberdiev, Y. Tillayev (UBAI), A. Shaymanov (Maidanak Observatory/UBAI) report on behalf of UBAI team. We observed the field of the GRB 251013C (Rakotondrainibe et al., GCN Circ. 42222) with the 1.5-m at Maidanak Observatory telescope AZT-22 equipped with the 4kx4k CCD SNUCAM camera (Im et al., 2010). The OT (Palmerio et al., GCN Circ. 42223; Perez-Garcia et al., GCN Circ. 42225; Konno et al., GCN Circ. 42226; Martin-Carrillo et al., GCN Circ. 42227; Masi et al., GCN Circ. 42228; Palmerio et al., GCN Circ. 42229; Moskvitin et al., GCN Circ. 42230; Gompertz et al., GCN Circ. 42231; Lipunov et al., GCN Circ. 42235; Garnavich et al., GCN Circ. 42240; Watson et al., GCN Circ. 42241; Lopez-Camara et al., GCN Circ. 42242; Zhang et al., GCN Circ. 42248; Brosio et al., GCN Circ. 42251; Reguitti et al., GCN Circ. 42253; Quintana-Ansaldo et al., Circ. GCN 42254; Maksut et al., GCN Circ. 42256; Ghosh et al., GCN Circ. 42261; Quadri et al., GCN Circ. 42262; Adami et al. GCN Circ. 42266; Peretto et al., GCN Circ. 42267; Ruocco et al., GCN Circ. 42269; Calapai, GCN Circ. 42275; Adami et al. GCN Circ. 42276; and Globus et all GCN 42279 ) is clearly detected in the individual and stacked frames. Preliminary photometry is as follows: Date UTstart Exptime t-T0 Filter OT Err. UL Site/Telescope (nxs) (mid, days) 2025-10-14 17:34:48 6x300 0.99659 R 20.96 0.04 23.10 MAO/AZT-22 All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained in Johnson Cousins filters were calibrated using the PanSTARRS DR1 catalog. The data has not corrected for the Galactic extinction. Maidanak astronomical observatory (MAO) is an observational facility of the Ulugh Beg Astronomical Institute (UBAI), Uzbekistan Academy of Sciences (http://maidanak.uz/) View this GCN Circular online at https://gcn.nasa.gov/circulars/42283. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40355] GRB 251011B: SVOM/VT optical upper limit
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42282 SUBJECT: GRB 251011B: SVOM/VT optical upper limit DATE: 25/10/15 07:42:44 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, H. L. Li, Z. H. Yao, L. P. Xin, Y. L. Qiu, C. Wu, 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, D. H. Zhao (NAOC), J. Palmerio (CEA), Y. H. Cheng (YNU), Y. Wang (PMO) report on behalf of the SVOM/VT team. SVOM performed a Target of Opportunity observation of GRB 251011B detected by Swift/BAT, Fermi/GBM, and SVOM/GRM (D'Ai et al., GCN 42197; Fermi GBM team, GCN 42196; Evans et al., GCN 42201; Mukherjee et al., GCN 42204; Sbarufatti et al., GCN 42205; Zao et al., GCN 42206). SVOM/VT began observing the field at 2025-10-11 09:06:00 UTC, 1.961 hours after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. No uncatalogued sources, compared to Legacy Survey, were detected in our single or stacked images within the error box provided by Swift/XRT position (D'Ai et al., GCN 42197; Evans et al., GCN 42201), the three sigma limits are: mid-time | exposure time | band | upper limit (AB) ----------|-----------------|-------|----------------- 2.3 h | 44*50 sec | VT_B | > 23.2 mag 2.3 h | 41*50 sec | VT_R | > 23.3 mag Our results are consistent with MASTER (Balanutsa et al., GCN 42203) and Swift/UVOT (Siegel & D'Ai, GCN 42209). 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/42282. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40354] GRB 251013C: Swift ToO observations
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42281 SUBJECT: GRB 251013C: Swift ToO observations DATE: 25/10/15 05:41:19 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the SVOM/ECLAIRs-detected event GRB 251013C. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021862 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the SVOM/ECLAIRs event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42281. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40353] GRB 251013D: Fermi GBM Observation
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42280 SUBJECT: GRB 251013D: Fermi GBM Observation DATE: 25/10/15 05:08:37 GMT FROM: Eva MP <eva.palafox(a)gmail.com> E. Palafox (INAOE) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 18:17:00.39 UT on 13 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251013D (trigger 782072225/251013762). which was also detected by Swift BAT (J. DeLaunay et al. 2025, GCN 42244). The Fermi GBM on-ground location is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 70 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 42 s (50-300 keV). The time-averaged spectrum from T0-6.1 to T0+15.4 s is best fit by a Comptonized function with Epeak = 129 +/- 12 keV, alpha = -0.9 +/- 0.1. The event fluence (10-1000 keV) in this time interval is (4.4 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+4.9 s in the 10-1000 keV band is 0.83 +/- 0.03 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/42280. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40352] GRB 251013C: SVOM/COLIBRÍ (FM-GFT) further multi-band optical observations
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42279 SUBJECT: GRB 251013C: SVOM/COLIBRÍ (FM-GFT) further multi-band optical observations DATE: 25/10/15 04:56:43 GMT FROM: globus(a)astro.unam.mx Noémie Globus (UNAM), Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Camila Angulo (UNAM), Ny Avo Rakotondrainibe (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the SVOM GRB 251013C (Rakotondrainibe et al., GCN Circ. 42222) using the DDRAGO two-channel, wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope from 2025-10-15 02:56 to 04:18 UTC (33.27 to 34.64 hours after the trigger), obtaining 32 minutes of exposure in the g filter, 32 minutes in the r filter, and 64 minutes in the z filter. The images were analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detected the optical counterpart (Palmerio et al., GCN Circ. 42223; Perez-Garcia et al., GCN Circ. 42225; Konno et al., GCN Circ. 42226; Martin-Carrillo et al., GCN Circ. 42227; Masi et al., GCN Circ. 42228; Palmerio et al., GCN Circ. 42229; Moskvitin et al., GCN Circ. 42230; Gompertz et al., GCN Circ. 42231; Lipunov et al., GCN Circ. 42235; Garnavich et al., GCN Circ. 42240; Watson et al., GCN Circ. 42241; Lopez-Camara et al., GCN Circ. 42242; Zhang et al., GCN Circ. 42248; Brosio et al., GCN Circ. 42251; Reguitti et al., GCN Circ. 42253; Quintana-Ansaldo et al., Circ. GCN 42254; Maksut et al., GCN Circ. 42256; Ghosh et al., GCN Circ. 42261; Quadri et al., GCN Circ. 42262; Adami et al. GCN Circ. 42266; Peretto et al., GCN Circ. 42267; Ruocco et al., GCN Circ. 42269; Calapai, GCN Circ. 42275; and Adami et al. GCN Circ. 42276) with preliminary magnitudes of: g = 21.59 +/- 0.04 r = 21.29 +/- 0.04 z = 20.93 +/- 0.07 We measure a g-r color of 0.30 +/- 0.06, which is consistent with the color of 0.31 +/- 0.01 at about 2 hours after the trigger reported by Palmerio et al. (GCN Circ. 42229), but significantly different to the color of -0.18 +/- 0.12 at about 28 hours after the trigger reported by Adami et al. (GCN Circ. 42276). Further observations and analysis are ongoing. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/42279. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40351] GRB 251014A: Swift-BAT refined analysis
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42278 SUBJECT: GRB 251014A: Swift-BAT refined analysis DATE: 25/10/15 01:35:52 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> M. J. Moss (GSFC), E. Ambrosi (INAF-IASFPA), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (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-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 251014A (trigger #1403878) (Ambrosi, et al., GCN Circ. 42238). The BAT ground-calculated position is RA, Dec = 111.728, 6.420 deg which is RA(J2000) = 07h 26m 54.7s Dec(J2000) = +06d 25' 10.7" with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 78%. The BAT mask-weighted light curve shows a single peaked emission with total duration of less than 2 sec. T90 (15-350 keV) is 1.56 +- 0.24 sec (estimated error including systematics). The time-averaged spectrum from T-0.07 to T+1.82 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.82 +- 0.70, and Epeak of 47.1 +- 9.2 keV (chi squared 60.50 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 2.3 +- 0.2 x 10^-07 erg/cm2 and the 1-sec peak flux measured from T-0.07 sec in the 15-150 keV band is 2.8 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.90 +- 0.13 (chi squared 69.47 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/1403878 View this GCN Circular online at https://gcn.nasa.gov/circulars/42278. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40350] IceCube-251014A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42277 SUBJECT: IceCube-251014A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/10/15 01:31:07 GMT FROM: Erik Blaufuss at University of Maryland, College Park <blaufuss(a)umd.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-10-14 at 18:33:11.58 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 2.226 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/141484_75492250.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-10-14 Time: 18:33:11.58 UT RA: 2.81 (+0.48/-0.49 deg 90% PSF containment) J2000 Dec: 2.91 (+0.49/-0.49 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/42277. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40349] GRB 251013C: OHP/T193 further optical observations and possible color evolution
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42276 SUBJECT: GRB 251013C: OHP/T193 further optical observations and possible color evolution DATE: 25/10/15 00:11:23 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> C. Adami (LAM/Pytheas/AMU), B. Schneider (LAM), E. Le Floc'h (CEA/Irfu), N.A. Rakotondrainibe (LAM), V. Buat (LAM/Pytheas/AMU), S. Basa (Pytheas/OHP/LAM), M. Dennefeld (IAP) report on behalf of the MISTRAL GRB collaboration: We carried out further observations of the GRB 251013C optical and NIR afterglow (Palmerio et al., GCN 42223 ; Perez-Garcia et al., GCN 42225 ; Konno et al., GCN 42226 ; Martin-Carrillo et al., GCN 42227 ; Masi et al., GCN 42228 ; Palmerio et al., GCN 42229 ; Moskvitin et al., GCN 42230 ; Gompertz et al., GCN 42231 ; Lipunov et al., GCN 42235 ; Garnavich, GCN42240; Watson et al., GCN 42241 ; Lopez-Camara et al., GCN 42242 ; Zhang et al., GCN 42248; Brosio et al., GCN 42251; Reguitti et al., GCN 42253 ; Quintana-Ansaldo et al., GCN 42254; Maksut et al., GCN 42256; Ghosh et al., GCN 42261 ; Quadri et al., GCN 42262 ; Adami et al. GCN 42266 ; Peretto et al., GCN 42267 ; Ruocco et al., GCN 42269 ; Calapai, GCN 42275) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 3 exposures of 10min followed by 1 exposure of 5min in the r-band, corresponding to T-T0 = 27.89 hr (mid-time). In addition, we obtained 2 exposures of 10min followed by 1 exposure of 15min in the g-band, corresponding to T-T0 = 28.71 hr (mid-time). The afterglow is well detected in the two bands and we measured the following preliminary magnitudes: g’ = 21.11 +/- 0.10 mag (AB) r’ = 21.29 +/- 0.07 mag (AB) This may suggest a color evolution compared to e.g. previous g-r values reported by Palmerio et al. (GCN 42229): 0.31 +/- 0.01 at T-T0 ~ 2.05 hr. In comparison, our preliminary values seem to indicate g’-r’ = -0.18 +/- 0.12 at T-T0 ~ 28.3 hr. The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitudes are not corrected for Galactic extinction. We used the STDWeb/STDPipe tools (Karpov 2025). We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Jean Balcaen and the SOPHIE observers J.B. Salomon and J.L. Halbwachs View this GCN Circular online at https://gcn.nasa.gov/circulars/42276. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40348] GRB 251013C: Calapai Observatory, Massa S. Giorgio (Messina), optical observation
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42275 SUBJECT: GRB 251013C: Calapai Observatory, Massa S. Giorgio (Messina), optical observation DATE: 25/10/14 23:48:43 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy <giovannicalapai(a)tiscali.it> Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We observed the field of GRB 251013C detected by SVOM (Rakotondrainibe et al., GCN 42222) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-10-13 19:01:08 UT (approximately 1.36 hours after burst) stacking 40 sets of unfiltered CCD image. The observations were carried out with clear skies and good visibility conditions. The OT was detected at the following position: RA (J2000.0) 23h 03m 20.56s Decl. (J2000.0) -00° 12' 37.00" We report our photometry analysis: HJD Exposure CR Mag Err ------------------------------------------- 2460962.295312 8x60s 15.56 0.01 2460962.301088 8x60s 15.75 0.01 2460962.306863 8x60s 15.97 0.01 2460962.312627 8x60s 16.09 0.01 2460962.318414 8x60s 16.16 0.01 2460962.324190 8x60s 16.20 0.01 2460962.329954 8x60s 16.27 0.01 2460962.335718 8x60s 16.41 0.01 2460962.341481 8x60s 16.53 0.01 2460962.347245 8x60s 16.61 0.01 2460962.353009 8x60s 16.68 0.01 2460962.358773 8x60s 16.69 0.01 2460962.364537 8x60s 16.72 0.01 2460962.370301 8x60s 16.80 0.01 2460962.376065 8x60s 16.80 0.01 2460962.381840 8x60s 16.90 0.01 2460962.387627 8x60s 16.91 0.01 2460962.393403 8x60s 17.02 0.01 2460962.399178 8x60s 17.02 0.01 2460962.404954 8x60s 17.17 0.01 2460962.410729 8x60s 17.17 0.02 2460962.416505 8x60s 17.22 0.02 2460962.422280 8x60s 17.23 0.02 2460962.428067 8x60s 17.31 0.02 2460962.433843 8x60s 17.35 0.02 2460962.439618 8x60s 17.38 0.02 2460962.445382 8x60s 17.44 0.02 2460962.451157 8x60s 17.43 0.02 2460962.456933 8x60s 17.58 0.03 2460962.462697 8x60s 17.56 0.03 2460962.468461 8x60s 17.70 0.03 2460962.474224 8x60s 17.62 0.03 2460962.479618 8x60s 17.72 0.03 2460962.485903 8x60s 17.75 0.03 2460962.491678 8x60s 17.86 0.04 2460962.497454 8x60s 18.02 0.05 2460962.503241 8x60s 18.03 0.05 2460962.509016 8x60s 17.97 0.05 2460962.514792 8x60s 17.99 0.05 2460962.521667 11x60s 18.06 0.05 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Our observations are consistent with other already reported Perez-Garcia et al. (GCN circ. 42225), Konno et al. (GCN circ. 42226), Martin-Carrillo et al. (GCN circ. 42227), Masi (GCN circ. 42228), Palmerio et al. (GCN circ. 42229), Moskvitin et al. (GCN circ. 42230), Gompertz et al. (GCN circ. 42231), Watson et al. (GCN circ. 42241), López-Cámara et al. (GCN circ. 42242), Zhang et al. (GCN circ. 42248), Brosio et al. (GCN circ. 42251), Quintana-Ansaldo et al. (GCN circ. 42254), Maksut et al. (GCN circ. 42256), Quadri et al.(GCN 42262), Adami et al.(GCN 42266), Peretto et al.(GCN 42267), Ruocco et al. (GCN 42269). The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42275. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40347] GRB 251014D: Swift detection of a burst
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42274 SUBJECT: GRB 251014D: Swift detection of a burst DATE: 25/10/14 22:50:35 GMT FROM: Simone Dichiara at Pennsylvania State University <sbd5667(a)psu.edu> N. J. Klingler (GSFC/UMBC/CRESSTII), S. Dichiara (PSU), R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL), A. Mei (INAF-OAB), C. Salvaggio (INAF-OAB) and T. Sbarrato (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 21:54:40.55 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 251014D (trigger=1404126). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 323.918, -41.839 which is RA(J2000) = 21h 35m 40s Dec(J2000) = -41d 50' 20" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve is not available because of a telemetry gap; however, the rate significance of 8.71 indicates that the event is likely real. The XRT began observing the field at 21:57:16.2 UT, 155.7 seconds after the BAT trigger. No source was detected in the 2.5-s promptly available image. We are waiting for the full dataset to detect and localise the XRT counterpart. The UVOT source list for the first white image shows no detection of a new source. Typical upper limits are 17th magnitude. Further details will become available when the full data are downloaded. 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/42274. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40346] GRB 251014A: PRIME near-infrared upper limits
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42273 SUBJECT: GRB 251014A: PRIME near-infrared upper limits DATE: 25/10/14 22:47:00 GMT FROM: Joe Durbak at UMD <gcn.joedurbak(a)gmail.com> J. Durbak (UMD), O. Guiffreda (UMD), N. Passaleva (U Rome), M. Elkabir (U Rome), A. S. Kutyrev (NASA/GSFC), E. Troja (U Rome), S. B. Cenko (NASA/GSFC) Following the Swift BAT (Ambrosi et al, GCN 42238) and Fermi GBM (Fermi GBM Team, GCN 42237) detection, we observed the transient field in J-filter with PRIME ~1 hour after Swift and Fermi detection. After comparing a previous J-band epoch observed in this location on 2024-11-17, we detect no new sources in J-band within the Swift BAT localization region. Using nearby 2MASS stars for preliminary calibration we derive a limiting magnitude >19.7 AB for the previous epoch, not corrected for Galactic extinction. Further observations are planned to obtain deeper imaging. 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/42273. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40345] GRB 251014A: PRIME near-infrared upper limits
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42273 SUBJECT: GRB 251014A: PRIME near-infrared upper limits DATE: 25/10/14 22:47:00 GMT FROM: Joe Durbak at UMD <gcn.joedurbak(a)gmail.com> J. Durbak (UMD), O. Guiffreda (UMD), N. Passaleva (U Rome), M. Elkabir (U Rome), A. S. Kutyrev (NASA/GSFC), E. Troja (U Rome), S. B. Cenko (NASA/GSFC) Following the Swift BAT (Ambrosi et al, GCN 42238) and Fermi GBM (Fermi GBM Team, GCN 42237) detection, we observed the transient field in J-filter with PRIME ~1 hour after Swift and Fermi detection. After comparing a previous J-band epoch observed in this location on 2024-11-17, we detect no new sources in J-band within the Swift BAT localization region. Using nearby 2MASS stars for preliminary calibration we derive a limiting magnitude >19.7 AB for the previous epoch, not corrected for Galactic extinction. Further observations are planned to obtain deeper imaging. 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/42273. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40344] GRB 251014A: VLT/FORS2 Optical Observation
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42270 SUBJECT: GRB 251014A: VLT/FORS2 Optical Observation DATE: 25/10/14 21:28:42 GMT FROM: Roberto Ricci at INAF-IRA <ricci(a)ira.inaf.it> Muskan Yadav (U Rome), Roberto Ricci (U Rome), Yu-Han Yang (U Rome), Rosa L. Becerra (U Rome) and Eleonora Troja (U Rome) report on behalf of the ERC BHianca team: We observed the field of GRB 251014A detected by Fermi (Fermi Team et al., GCN 42237) and Swift/BAT (Ambrosi et al., GCN 42238) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began 7.55 hours after the trigger and were carried out in the R filter with an average airmass of ~1.5. Having no reference image deep enough to compare with our science image, at this stage we are not able to determine whether there are new sources down to the limiting magnitude probed by FORS2. Further observations or an arcsec X-ray counterpart are required to make such a claim. 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/42270. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40343] GRB 251014C: Fermi GBM Final Localization
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42272 SUBJECT: GRB 251014C: Fermi GBM Final Localization DATE: 25/10/14 21:48:07 GMT FROM: Suman Bala at USRA <sumanbala2210(a)gmail.com> The Fermi GBM team reports the detection of a likely LONG GRB "At 20:45:58.96 UT on 14 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251014C (trigger 782167563/251014865). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 133.36, Dec = 14.24 (J2000 degrees, equivalent to J2000 8h 53m, +14d 14'), with a statistical uncertainty of 5.09 degrees. The angle from the Fermi LAT boresight is 84 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251014865/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251014865/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251014865/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/42272. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40342] GRB 251014A: Glowbug gamma-ray detection of a likely short burst
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42271 SUBJECT: GRB 251014A: Glowbug gamma-ray detection of a likely short burst DATE: 25/10/14 21:37:02 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.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 251014A, which was also detected by Fermi/GBM (GCN 42237, 42249) and Swift/BAT (GCN 42238). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-14 00:28:30.032 with a duration of 1.02 s and a total significance of about 9.9 sigma. The light curve is dominated by a single peak. 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/42271. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40341] GRB 250821A: VLT/FORS2 Optical Observation
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42270 SUBJECT: GRB 250821A: VLT/FORS2 Optical Observation DATE: 25/10/14 21:28:42 GMT FROM: Roberto Ricci at INAF-IRA <ricci(a)ira.inaf.it> Muskan Yadav (U Rome), Roberto Ricci (U Rome), Yu-Han Yang (U Rome), Rosa L. Becerra (U Rome) and Eleonora Troja (U Rome) report on behalf of the ERC BHianca team: We observed the field of GRB 251014A detected by Fermi (Fermi Team et al., GCN 42237) and Swift/BAT (Ambrosi et al., GCN 42238) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began 7.55 hours after the trigger and were carried out in the R filter with an average airmass of ~1.5. Having no reference image deep enough to compare with our science image, at this stage we are not able to determine whether there are new sources down to the limiting magnitude probed by FORS2. Further observations or an arcsec X-ray counterpart are required to make such a claim. 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/42270. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40340] GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42269 SUBJECT: GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart DATE: 25/10/14 20:51:20 GMT FROM: Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy - MPC Code C82 <osservatorionastroverde(a)gmail.com> Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy in a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report: Following the circular GCN 42222, in which N. A. Rakotondrainibe, C. Adami (LAM), D. Turpin, D. Götz (CEA/Irfu), H. Yang (IRAP), in which at 2025-10-13T17:39:42 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251013C (SVOM burst-id sb25101311) also detected by Fermi/GBM, I pointed at the coordinates RA(J2000)=23h 03m 22s: Dec(J2000)=-00d 12' 37" and started my observations with telescope of Nastro Verde Observatory - Sorrento (Naples), Italy. Member of: AAVSO - American Association of Variable Star Observers. GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. The observations started at 20:04:39 UT of 2025/10/13, after about 3.30 hours after the GRB trigger, with clear sky, with principal telescope SC 0.35 f/10 with focal reduced + CCD Sbig ST10 XME, using the V and Rc photometric filters. I took 20 unfiltered images of 60 sec in each filter. The images were added in groups of five to obtain a higher S/N Start End 20:04:39 UT 20:56:46 UT All images, calibrated with masterdark and masterflat have been measured with Maxim DL software I have detected a bright source at the enhanced position reported by GCNs (Konno et al. (GCN circ. 42226), Perez-Garcia et al. (GCN circ. 42225), Martin-Carrillo et al. (GCN circ. 42227), Masi (GCN circ. 42228), Palmerio et al. (GCN circ. 42229), Moskvitin et al. (GCN circ. 42230), Gompertz et al. (GCN circ. 42231), Watson et al. (GCN circ. 42241), LÃ³pez-CÃ¡mara et al. (GCN circ. 42242), Zhang et al. (GCN circ. 42248), Brosio et al. (GCN circ. 42251), Quintana-Ansaldo et al. (GCN circ. 42254), and Maksut et al. (GCN circ. 42256), U. Quadri et al.(GCN 42262), C. Adami et al.(GCN 42266), I. Peretto et al.(GCN 42267) at following position RA (J2000.0) 23 03 20.55 Dec (J2000.0) -00 12 37.0 with the following photometry: (JD) Mag Err Filter 2460962.3649074 17.259 0.101 V 2460962.3561574 16.903 0.065 V 2460962.3473842 16.697 0.041 V 2460962.3374884 16.576 0.044 V 2460962.3639930 16.5 0.044 Rc 2460962.3552430 16.43 0.039 Rc 2460962.3464815 16.281 0.027 Rc 2460962.3365625 16.114 0.023 Rc Magnitudes were estimated with the pan-STARRS cat and are derived using Lupton (2005) equations. Not corrected for galactic dust extinction.. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42269. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40339] GRB 251012A: Glowbug gamma-ray detection of a likely short burst
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42268 SUBJECT: GRB 251012A: Glowbug gamma-ray detection of a likely short burst DATE: 25/10/14 20:31:56 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, 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 251012A, which was also detected by Fermi/GBM (GCN 42207). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-12 14:46:26.104 with a duration of 0.16 s and a total significance of about 13.0 sigma. The light curve comprises a single peak. 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/42268. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40338] GRB 251013C: MarSEC, optical afterglow photometry
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42267 SUBJECT: GRB 251013C: MarSEC, optical afterglow photometry DATE: 25/10/14 19:43:03 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). In a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy) and Stefano Lora, Giovanni Furlato and Giuseppe Peretto (MarSEC, Marana Space Explorer Center, Marana di Crespadoro, VI, Italy) report: We imaged the field of GRB 251013C detected by SVOM (Rakotondrainibe et al., GCN 42222), with the robotic telescope of (IAU station 565) with the telescope 14” RC Officine Stellari of MarSEC (Marana Space Explorer Center) with CCD Moravian G2-1600-MKII. The observations with a series of 90 sec exposures, 2025-10-13T23:13:26.703'UT of midpoint of exposure, with a Ritchey-Chretien telescope D=360 mm f/8. The afterglow was clearly detected at the following position: RA(J2000) = 23h 03m 20,7s Dec(J2000) = -00d 13' 37" We report our photometry analysis: HJD Rc Mag Err ------------------------------------- 2460962.4676701734 16.813 0.08 Weather conditions were good, sqm medium 20,85 We co-added 14 exposures of 90 sec. each. Magnitudes were estimated with the pan-STARRS cat and are derived using Lupton (2005) equations and are not corrected for galactic dust extinction. Reference: https://www.marsec.org/ The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42267. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40337] GRB 251013C: OHP/T193 optical afterglow photometry and spectroscopy
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42266 SUBJECT: GRB 251013C: OHP/T193 optical afterglow photometry and spectroscopy DATE: 25/10/14 19:29:02 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> C. Adami (LAM/Pytheas/AMU), B. Schneider (LAM), E. Le Floc'h (CEA/Irfu), A. de Ugarte Postigo (LAM), S. Basa (Pytheas/OHP/LAM), F. Schüssler (CEA/Irfu), N.A. Rakotondrainibe (LAM), report on behalf of a larger collaboration: We observed the field of GRB 251013C detected by FERMI (Fermi GBM Team, GCN Circ. 42221) and SVOM/ECLAIRs (Rakotondrainibe et al., GCN Circ. 42222) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained one exposure of 3min in the r-band starting at 19:28:38 UT on 2025-10-13. The optical counterpart previously reported by different groups is well detected. Consistent with previously reported photometric measurements, the preliminary magnitude derived for that source is: r’ = 15.92 +/- 0.04 mag (AB) We also obtained a 10min spectrum roughly covering the 4800-8200A range, starting at 19:19:40 UT 2025-10-13. We detect a strong continuum but no prominent lines in our range, consistently with the redshift measured by Martin-Carrillo (GCN 42227). The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitudes are not corrected for Galactic extinction. We used the STDWeb/STDPipe tools (Karpov 2025). We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Jean Balcaen and the SOPHIE observers J.B. Salomon and J.L. Halbwachs View this GCN Circular online at https://gcn.nasa.gov/circulars/42266. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40336] GRB 251014B: Swift ToO observations
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42265 SUBJECT: GRB 251014B: Swift ToO observations DATE: 25/10/14 18:34:34 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the Fermi/GBM-detected event GRB 251014B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021863 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Fermi/GBM event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42265. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40335] GRB 251013D: LAST optical upper limit on Swift/BAT-GUANO localization
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42264 SUBJECT: GRB 251013D: LAST optical upper limit on Swift/BAT-GUANO localization DATE: 25/10/14 17:20:18 GMT FROM: Ruslan Konno at Weizmann Institute of Science <ruslankonno(a)gmail.com> R. Konno (WIS), S. Garrappa (WIS), E. A. Zimmerman (WIS), A. Horowicz (WIS), E. O. Ofek (WIS), S. Ben-Ami (WIS), D. Polishook (WIS), O. Yaron (WIS), S. Fainer (WIS), A. Krassilchtchikov (WIS), Y. M. Shani (WIS), E. Segre (WIS), A. Gal-Yam (WIS), and S. Spitzer (WIS) report on behalf of the LAST Collaboration. We report observations of GRB 251013D, detected by Fermi (Fermi GBM Team, GCN 42224). Observations were conducted with the Large Array Survey Telescope (LAST; Ofek et al. 2023, PASP 135, 5001; Ben-Ami et al. 2023, PASP 135, 5002). We observed the field of GRB 251013D using 20 divergent telescopes (each with a 7.4 deg^2 FoV) in clear band (similar to the Gaia Bp band) over several epochs. Each coadd consists of 20x20 s exposures, yielding a limiting magnitude of about 20.5 AB mag. Our observations cover about 80% of the localization region within the HEALPix FITS file glg_healpix_all_bn251013762.fit (Fermi GBM Team, GCN 42224) and include the Swift/BAT-GUANO localization (DeLaunay et al., GCN 42244). We coadded the Swift/BAT-GUANO coverage obtained between 2025-10-13 22:22:33 UTC (T − T0 = 4.09 h) and 2025-10-14 01:02:54 UTC (T − T0 = 6.77 h) for a total integration of 120 x 20 s and performed image subtraction using reference images of this field. No new source was detected within the Swift/BAT-GUANO region down to a limiting magnitude of 21.14 (AB). No source brighter than 19.44 mag (AB) with significant variability (> 0.5 mag) was observed between the start and end of the observations of the same field. LAST is a survey telescope array of the Weizmann Astrophysical Observatory (https://www.weizmann.ac.il/wao/) View this GCN Circular online at https://gcn.nasa.gov/circulars/42264. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40334] GRB 251014B: Swift/BAT-GUANO arcminute localization of a short burst
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42263 SUBJECT: GRB 251014B: Swift/BAT-GUANO arcminute localization of a short burst DATE: 25/10/14 17:05:50 GMT FROM: Samuele Ronchini at PSU <sjs8171(a)psu.edu> Samuele Ronchini (GSSI), James DeLaunay (PSU), Aaron Tohuvavohu (Caltech), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (Northwestern) report: Swift/BAT did not localize GRB 251014B onboard (T0: 2025-10-14T04:47:21.17 UTC, Fermi trigger number 782110046). 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 arcmin position of the burst is found with the newly developed pipeline BAT-GLIMPSE: Gamma-ray Localization using Imaging and Mosaic techniques for Pointing and Slew Epochs (Ronchini et. al, in prep). The pipeline makes use of the tools from BatAnalysis (Parsotan et al. 2025). The source is found with an SNR = 8.5 Independently, the BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), confirms the detection of the burst in a 2.048 s analysis time bin starting at T0 - 1.024 s with a sqrt(TS) of 19.78. An arcminute localization is found with DeltaLLHOut of 53.26 and a DeltaLLHPeak of 48.76. See Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief descriptions and interpretations of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut. The BAT position is: RA, Dec = 14.5954, -35.5802 deg which is RA(J2000) = 00h 58m 22.90s Dec(J2000) = -35d 34’ 48.7″ with an estimated uncertainty of 3 arcmin radius. More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=782110077 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/42263. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40333] GRB 251013C: Bassano Bresciano Observatory optical observations
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42262 SUBJECT: GRB 251013C: Bassano Bresciano Observatory optical observations DATE: 25/10/14 16:09:54 GMT FROM: Ulisse Quadri at Bassano Bresciano Observatory <osservatoriobassano(a)gmail.com> U.Quadri, L.Strabla and P.Madurini (Bassano Bresciano Astronomical Observatory) Members of: GRB/UAI - Gamma ray Burst section of Unione Astrofili Italiani. AAVSO - American Association of Variable Star Observers. GAC - Gruppo Astrofili Cremonesi. In a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy), report: We imaged the field of GRB 251013C detected by SVOM (Rakotondrainibe et al., GCN 42222), with the robotic telescope of (IAU station 565) Bassano Bresciano Observatory, Italy . The observations started 1h 47m after the trigger with our Newton telescope D=440 mm F/D=4.5. We co-added series of 10 exposures of 30 sec each. We clearly detect a bright afterglow reported by GCNs (Konno et al. (GCN circ. 42226), Perez-Garcia et al. (GCN circ. 42225), Martin-Carrillo et al. (GCN circ. 42227), Masi (GCN circ. 42228), Palmerio et al. (GCN circ. 42229), Moskvitin et al. (GCN circ. 42230), Gompertz et al. (GCN circ. 42231), Watson et al. (GCN circ. 42241), LÃ³pez-CÃ¡mara et al. (GCN circ. 42242), Zhang et al. (GCN circ. 42248), Brosio et al. (GCN circ. 42251), Quintana-Ansaldo et al. (GCN circ. 42254), and Maksut et al. (GCN circ. 42256)) at the following position (+/- 3 arcsec): RA (J2000.0) = 23 03 20.5 DEC(J2000.0) = -00 12 37 We report our photometry analysis: HJD CR Mag Err ----------------------------- 2460962.318647 15.63 0.01 2460962.318647 15.63 0.01 2460962.322293 15.67 0.01 2460962.325915 15.73 0.01 2460962.329549 15.72 0.01 2460962.333183 15.77 0.01 2460962.336817 15.84 0.01 2460962.340463 15.92 0.01 2460962.344097 15.98 0.01 2460962.347730 16.05 0.01 2460962.351307 16.12 0.01 2460962.355022 16.18 0.01 2460962.358656 16.24 0.01 2460962.362302 16.24 0.02 2460962.365947 16.24 0.02 2460962.369581 16.29 0.02 2460962.373227 16.31 0.01 2460962.376873 16.35 0.02 2460962.380507 16.37 0.02 2460962.384141 16.37 0.02 2460962.387775 16.43 0.02 2460962.391397 16.47 0.02 2460962.395032 16.54 0.02 2460962.398665 16.55 0.02 2460962.402299 16.56 0.02 2460962.405933 16.61 0.02 2460962.409568 16.64 0.02 2460962.413190 16.64 0.02 2460962.416824 16.68 0.02 2460962.420458 16.71 0.02 2460962.424092 16.78 0.02 2460962.427715 16.83 0.02 2460962.431349 16.83 0.03 2460962.434982 16.84 0.03 2460962.438617 16.98 0.03 2460962.442251 17.06 0.04 2460962.445885 17.03 0.05 2460962.449519 17.02 0.04 2460962.453153 17.09 0.04 2460962.456787 17.02 0.04 ----------------------------- CR magnitude is unfiltered with R zero point. Magnitudes were estimated with the pan-STARRS cat and are derived using Lupton (2005) equations. Not corrected for galactic dust extinction. Reference: http://www.osservatoriobassano.altervista.org The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42262. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40332] GRB 251013C: Early and late-time optical counterpart detection by LCO
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42261 SUBJECT: GRB 251013C: Early and late-time optical counterpart detection by LCO DATE: 25/10/14 15:45:51 GMT FROM: ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994(a)gmail.com> Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Rahul Gupta (NASA GSFC), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES) on behalf of a larger collaboration. We observed the field of the GRB 251013C triggered by Fermi (Fermi GBM team, GCN circ. 42221), and SVOM (Rakotondrainibe et al., GCN circ. 42222) in V and r filters of the 1-meter Sinistro telescope at the Las Cumbres Observatory Global Telescope (LCOGT) node located at South African Astronomical Observatory (SAAO). The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel). Observations began on October 13, 2025, starting from 2.88 hours after the GRB trigger. Further observations are still ongoing. We clearly detect the optical transient (OT) reported by GCNs (Konno et al. (GCN circ. 42226), Perez-Garcia et al. (GCN circ. 42225), Martin-Carrillo et al. (GCN circ. 42227), Masi (GCN circ. 42228), Palmerio et al. (GCN circ. 42229), Moskvitin et al. (GCN circ. 42230), Gompertz et al. (GCN circ. 42231), Watson et al. (GCN circ. 42241), López-Cámara et al. (GCN circ. 42242), Zhang et al. (GCN circ. 42248), Brosio et al. (GCN circ. 42251), Quintana-Ansaldo et al. (GCN circ. 42254), and Maksut et al. (GCN circ. 42256)). ------------------------------------------------------------------------------------------------------ |Date| |JDstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude| ------------------------------------------------------------------------------------------------------ 2025-10-13 2460962.35625 2.88 1 x 300 V V = 16.61 +/- 0.01 2025-10-14 2460963.01397 18.67 1 x 600 V V = 20.73 +/- 0.05 ------------------------------------------------------------------------------------------------------ The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42261. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40331] LIGO/Virgo/KAGRA S251014cn: NED Galaxies in the 3-Initial Localization Volume
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42260 SUBJECT: LIGO/Virgo/KAGRA S251014cn: NED Galaxies in the 3-Initial Localization Volume DATE: 25/10/14 15:45:35 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 S251014cn-3-Initial sky localization with the [NED Local Volume Sample](https://ned.ipac.caltech.edu/NED::LVS/) (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 10691 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/S251014cn/3 Top 20 List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S251014cn/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 J204706.11-222948.1| 311.77550| -22.49672| G| 727.73| 4.31| null| null| 14.677| 0.171| 9.127| 0.006|1.25e-07| 1.19e-09| |WISEA J210442.39-250658.2| 316.17666| -25.11619| G| 632.49| 0.65| null| null| 12.233| 0.093| 9.702| 0.006|1.67e-07| 7.14e-10| | [HB89] 2155-304| 329.71694| -30.22559| QSO| 546.26| 0.43| 13.401| 0.001| 10.101| 0.013| 9.233| 0.006|8.29e-08| 4.03e-10| |WISEA J203200.13-212013.9| 308.00055| -21.33721| G| 686.01| null| null| null| 13.471| 0.172| 11.048| 0.007|2.64e-07| 3.82e-10| |WISEA J195711.85-155450.4| 299.29942| -15.91401| G| 464.26| null| null| null| 13.148| 0.182| 9.223| 0.006|9.41e-08| 3.41e-10| |WISEA J210053.37-260056.2| 315.22239| -26.01562| G| 523.86| null| 20.640| 0.211| 13.660| 0.182| 10.671| 0.006|2.12e-07| 2.55e-10| |WISEA J202657.64-194510.3| 306.74020| -19.75287| G| 536.72| 0.65| null| null| 12.502| 0.088| 10.962| 0.006|2.42e-07| 2.33e-10| |WISEA J233456.39-265518.6| 353.73499| -26.92184| G| 280.74| 0.65| null| null| 11.229| 0.056| 8.467| 0.005|8.37e-08| 2.18e-10| |WISEA J195521.91-151547.2| 298.84130| -15.26312| G| 485.70| null| null| null| 13.338| 0.163| 10.223| 0.007|1.19e-07| 1.91e-10| |WISEA J211913.50-272622.9| 319.80626| -27.43970| G| 533.96| null| 21.251| 0.278| 13.385| 0.135| 11.169| 0.007|2.33e-07| 1.84e-10| |WISEA J201311.18-190314.5| 303.29661| -19.05404| G| 572.05| null| null| null| 13.451| 0.145| 11.150| 0.007|1.75e-07| 1.62e-10| |WISEA J202635.83-202306.5| 306.64930| -20.38515| G| 735.83| 0.65| null| null| 12.556| 0.102| 11.879| 0.008|2.08e-07| 1.62e-10| |WISEA J202559.97-203159.0| 306.49991| -20.53307| G| 732.69| 0.65| null| null| 12.200| 0.114| 11.897| 0.012|2.03e-07| 1.54e-10| |WISEA J214110.24-264550.3| 325.29269| -26.76397| QSO| 608.68| null| 16.698| 0.017| 11.077| 0.012| 9.482| 0.006|3.03e-08| 1.46e-10| |WISEA J204622.40-223419.0| 311.59335| -22.57195| G| 685.98| 4.31| null| null| 15.453| 0.346| 11.646| 0.007|1.74e-07| 1.46e-10| |WISEA J200050.95-154454.3| 300.21230| -15.74842| G| 688.87| null| null| null| 13.684| 0.252| 11.792| 0.008|1.90e-07| 1.41e-10| |WISEA J193249.64-101803.3| 293.20684| -10.30092| G| 410.47| 0.65| null| null| 12.248| 0.139| 9.373| 0.006|5.53e-08| 1.39e-10| |WISEA J210524.13-254016.4| 316.35056| -25.67124| G| 492.45| null| null| null| 13.568| 0.159| 11.429| 0.007|2.62e-07| 1.38e-10| |WISEA J202206.73-184638.7| 305.52808| -18.77742| G| 497.59| 0.65| 19.597| 0.097| 12.293| 0.055| 11.011| 0.007|1.75e-07| 1.38e-10| |WISEA J201415.46-192535.3| 303.56468| -19.42654| G| 602.46| null| null| null| 13.720| 0.165| 11.210| 0.007|1.39e-07| 1.35e-10| Table 1: Top 20 galaxies in NED-LVS that fall in the 90% probability volume for S251014cn 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/42260. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40330] GRB 251013C: Fermi GBM Observation
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42259 SUBJECT: GRB 251013C: Fermi GBM Observation DATE: 25/10/14 15:35:36 GMT FROM: Jacob Smith at Fermi-GBM Team <jrs0118(a)uah.edu> Jacob Smith (UAH), E. Palafox (INAOE), and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 17:39:41.94 UT on 13 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251013C (trigger 782069986/251013736), which was also detected by SVOM (N. A. Rakotondrainibe et al. 2025, GCN 42222) and Swift XRT (P.A. Evans et al. 2025, GCN 42232). The Fermi GBM on-ground location is consistent with the Swift BAT position. NOT measured a spectroscopic redshift z = 0.572 (A. Martin-Carrillo et al. 2025, GCN 42227). The angle from the Fermi LAT boresight is 60 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 12 s (50-300 keV). The time-averaged spectrum from T0-0.1 to T0+4.0 s is best fit by a simple power law function with index -1.50 +/- 0.02. A Comptonized function fits equally well with Epeak = 7291.00 +/- 4840.00 and alpha = -1.46 +/- 0.03. The event fluence (10-1000 keV) in this time interval is (2.4 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.32 s in the 10-1000 keV band is 5 +/- 0.2 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/42259. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40329] GRB 251013D: Swift ToO observations
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42258 SUBJECT: GRB 251013D: Swift ToO observations DATE: 25/10/14 15:22:30 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the Fermi/GBM-detected event GRB 251013D. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021861 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Fermi/GBM event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42258. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40328] GRB 251014A: DDOTI Upper Limit
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42257 SUBJECT: GRB 251014A: DDOTI Upper Limit DATE: 25/10/14 13:52:43 GMT FROM: Rosa Leticia Becerra Godínez at Tor Vergata, Roma <rbecerra(a)astro.unam.mx> Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Sahil Atri (U Roma), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report: We observed the field of GRB 251014A detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 42237) and Swift (Ambrosi et al., GCN Circ. 42238) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2025-10-14 UTC. DDOTI observed the Swift/BAT position (Ambrosi et al., GCN Circ. 42238) from 09:12 UTC to 12:27 UTC (from T+8.7 h to T+ 11.9 h after the trigger), obtaining a total exposure of 70 minutes, alternating with other scientific programs. Comparing our observations to the USNO-B1 and Pan-STARRS PS1 DR2 catalogues, we detect no uncatalogued fading sources within the observed field down to a 5-sigma limiting AB magnitude of: w >20.3 This value is consistent with the reported by the SAO RAS collaboration (Moskvitin et al. GCN Circ. 42250) and is not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/42257. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40327] GRB 251013C NUTTelA-TAO / BSTI Early Measurements
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42256 SUBJECT: GRB 251013C NUTTelA-TAO / BSTI Early Measurements DATE: 25/10/14 13:45:06 GMT FROM: Zhanat Maksut at Nazarbayev University <zhanat.maksut(a)nu.edu.kz> Z. Maksut (NU), B. Grossan (UCB, NU), T. Komesh (NU), D. Berdikhan (NU), M. Krugov (FAI) and E. Abdikamalov (NU) report on behalf of the Energetic Cosmos Laboratory: The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) pointed at GRB 251013C on receipt of an automated GCN SVOM/ECLAIRs position alert, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14). We started observations at UT 2025 October 13, 17:41:17, 95 s after the ECLAIRs trigger (N. A. Rakotondrainibe, et. al., GCN 42222). Observations were made in conditions that started good and deteriorated to cloudy over the night. A new and changing source consistent with the XRT position (P.A. Evans et al., GCN 42232) was detected. Note that these observations provide essentially full-time coverage until conditions deteriorated, about 3 hours of coverage. The source was off our field in g' and r' band cameras, but on the sensor with adequate margin in our Sloan i' camera. We report the following preliminary, uncorrected, selected photometric values for the optical transient: tc-t0(s) texp i'(mag) err(mag) -------- ------ ------- -------- 96 3.0 13.67 0.1 123 3.0 14.20 0.1 141 3.0 14.27 0.1 185 30.0 14.69 0.06 245 30.0 14.96 0.06 305 30.0 15.16 0.06 425 30.0 15.06 0.06 635 30.0 15.14 0.06 tc-t0 = trigger time minus image center time. Calibration was done with 5 bright Pan-STARRS catalog stars on our images (see Komesh, T. et al. 2023, MNRAS 520, 6104). We find a rapid fading to a plateau starting at ~300 s. We caution the reader that these are preliminary results, without color or other corrections, and will likely change. Please also note that times are approximate. Systematic errors are estimated from previous measurements. We welcome requests for additional data. ---------------------------------- NU = Nazarbayev University, Astana, Kazakhstan UCB = University of California, Berkeley, USA FAI = Fesenkov Astrophysical Institute, Kazakhstan This research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP26103591). The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan. View this GCN Circular online at https://gcn.nasa.gov/circulars/42256. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40326] LIGO/Virgo/KAGRA S251014cn: Identification of a GW compact binary merger candidate
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42255 SUBJECT: LIGO/Virgo/KAGRA S251014cn: Identification of a GW compact binary merger candidate DATE: 25/10/14 12:32:53 GMT FROM: Matteo Tagliazucchi at University of Bologna - INFN Bologna <matteo.tagliazucchi2(a)unibo.it> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S251014cn during real-time processing of data from LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at 2025-10-14 11:33:23.373 UTC (GPS time: 1444476821.373). The candidate was found by the Aframe [1], cWB [2], cWB BBH [3], GstLAL [4], MBTA [5], MLy [6], PyCBC Live [7], and SPIIR [8] analysis pipelines. S251014cn is an event of interest because its false alarm rate, as estimated by the online analysis, is 3.2e-10 Hz, or about one in 1e2 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S251014cn The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), BNS (<1%), or NSBH (<1%). Assuming the candidate is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass (HasNS) is <1%. [9] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [9] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. The source chirp mass falls with highest probability in the bin (11.0, 22.0) solar masses, assuming the candidate is astrophysical in origin. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [10], distributed via GCN and SCiMMA notices about 24 seconds after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [10], distributed via GCN and SCiMMA notices about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is 233 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 610 +/- 172 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Marx et al. PRD 111, 042010 (2025) doi:10.1103/PhysRevD.111.042010 [2] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [3] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [4] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. PRD 109, 042008 (2024) doi:10.1103/PhysRevD.109.042008 [5] Alléné et al. CQG 42, 105009 (2025) doi:10.1088/1361-6382/add234 [6] Skliris et al. PRD 110, 104034 (2024) doi:10.1103/PhysRevD.110.104034 [7] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [8] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [9] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [10] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/42255. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40325] GRB 251013C: ULL-ASTRO-MASTER detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42254 SUBJECT: GRB 251013C: ULL-ASTRO-MASTER detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory DATE: 25/10/14 12:02:29 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> M. Quintana-Ansaldo, J. Basurto Merino, P.G. Berdayes, A. Caballero-Almagro, A. Cerón, M. Contreras, F. Díaz-Segado, T. Ferrer-Laviña, B. Gandolfi, V. Ghiraldo, J. Hernández Fung, L. Juliá-Maroto, E. Lekaroz-Urriza, M. Manzano García, E. Mejía-Martínez, J. Prieto Polo, M. Pulido-Torres, , A. Schenone-Zanuzzi, A. Selezneva, T. Tundidor Rodríguez, E. Urquijo-Rodríguez (all ULL), M. Abdul-Masih (IAC and ULL), and I. Pérez-Fournon (IAC and ULL). Following the detection of GRB 251013C by Fermi (Fermi GBM team, GCN circ. 42221), and SVOM (Rakotondrainibe et al., GCN circ. 42222), we observed the field with the Las Cumbres Observatory (LCO) 40-cm telescope (a Planewave Delta Rho 350 telescope equipped with a CMOS QHY600 camera) located at the LCO node at Sutherland Observatory (South Africa). The observation, a single exposure of 300 sec in the SDSS r filter, started on 2025-10-13 at 18:27:18 UT, about 47 minutes after the Fermi and SVOM trigger. The optical counterpart detected by SVOM/VT (Palmerio et al., GCN circ. 42223) is clearly detected in our image with a magnitude of r = 14.84 +/- 0.02 (AB), calibrated against PanSTARRS-1 DR2 and not corrected for galactic extinction. This result confirms the rebrightening reported by Konno et al. (GCN circ. 42226). Other optical and near-IR detections have been reported by Perez-Garcia et al. (GCN circ. 42225), Martin-Carrillo et al. (GCN circ. 42227), Masi (GCN circ. 42228), Palmerio et al. (GCN circ. 42229), Moskvitin et al. (GCN circ. 42230), Gompertz et al. (GCN circ. 42231), Watson et al. (GCN circ. 42241), López-Cámara et al. (GCN circ. 42242), Zhang et al. (GCN circ. 42248), and Brosio et al. (GCN circ. 42251). A redshift of z = 0.572 has been measured by Martin-Carrillo et al. (GCN circ. 42227). GRB 251013C has also been detected by Swift-XRT (Evans et al., GCN circ. 42232), AstroSat (Arya et al., GCN circ. 42246), Einstein Probe (Wang et al., GCN circ. 42247), and ALMA Laskar et al. (GCN circ. 42243). Based on observations made with the Las Cumbres Observatory’s education network telescopes that were upgraded through generous support from the Gordon and Betty Moore Foundation (program IAC2025B-010). These observations are part of a course in Astrophysical Techniques of the Master in Astrophysics of the Astrophysics Department of the University of La Laguna in collaboration with the Instituto de Astrofísica de Canarias (La Laguna, Tenerife, Canary Islands, Spain). View this GCN Circular online at https://gcn.nasa.gov/circulars/42254. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40324] GRB 251013C: Asiago optical observations
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42253 SUBJECT: GRB 251013C: Asiago optical observations DATE: 25/10/14 11:40:21 GMT FROM: Andrea Reguitti at INAF - Osservatorio Astronomico di Padova <andreareguitti(a)gmail.com> A. Reguitti (INAF/OAPd) reports on behalf of a larger collaboration: I observed the field of GRB 251013C (Fermi GBM Team, GCN 42221; Rakotondrainibe et al., GCN 42222) using the 67/92 Schmidt Telescope located at the Asiago observatory (Italy). Observations were carried out using Sloan r and i filters. The optical counterpart (Palmerio et al., GCN 42223; Perez-Garcia et al., GCN 42225; Konno et al., GCN 42226; Martin-Carrillo et al., GCN 42227; Masi, GCN 42228; Palmerio et al., GCN 42229; Moskvitin et al., GCN 42230; Gompertz et al., GCN 42231; Garnavich, GCN 42240; Watson et al., GCN 42241; López-Cámara et al., GCN 42242; Brosio et al., GCN 42251) is clearly detected in our frames. At mean epoch 2025 Oct 13.85 UT (2.75 hr after the GRB), I measure AB magnitudes r = 16.51 +- 0.05 and i = 16.27 +- 0.04 (calibrated against magnitudes from the Pan-STARRS catalog). View this GCN Circular online at https://gcn.nasa.gov/circulars/42253. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40323] GRB 251013A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42252 SUBJECT: GRB 251013A: CALET Gamma-Ray Burst Monitor detection DATE: 25/10/14 11:06:25 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> S. Sugita, A. Yoshida, T. Sakamoto, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The GRB 251013A (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN Circ. 42213; SVOM/GRM observation: Wang et al., GCN Circ. 42218) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 08:04:04.90 UTC on 13 October 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1444377382/index.html) The burst signal was seen by only the SGM detector. The burst light curve shows a single pulse that starts at T+0.55 sec, peaks at T+1.32 sec, and ends at T+1.85 sec. The T90 and T50 durations measured by the SGM data are 1.20 +/- 0.16 sec and 0.50 +/- 0.11 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1444377382/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/42252. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40322] GRB 251013C: ABObservatory afterglow detection
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42251 SUBJECT: GRB 251013C: ABObservatory afterglow detection DATE: 25/10/14 10:53:56 GMT FROM: A. Brosio at ABObservatory Rosarno <antonino.brosio(a)gmail.com> A. Brosio (ABObservatory Rosarno), M. A. Tripodi (ABObservatory Rosarno), S. Savaglio (University of Calabria), G. Bracco, P. Cianfarra, L. Sangaletti, S. Tosi & S. Zappatore (University of Genoa), S. Benatti & M. G. Guarcello (INAF Palermo), L.Cabona, M. Rainer, F. M. Zerbi, M. Basilicata (INAF Brera), D. Ricci (INAF Padova), A. Di Dato (INAF Capodimonte), S. Masiero & A. Nastasi (GAL Hassin), D. Liguori (Osservatorio "G. Galilei" Cariati), L. Betti (Osservatorio Polifunzionale del Chianti), R. Nesci (Associazione Astronomica Antares APS di Foligno), for the NOCTIS team report We observed the field of GRB 251013C, which was detected by Fermi GBM team (GCN 42221) with the 30-cm automated telescope at ABObservatory (Rosarno, Italy) in V filter. The observations began on 2025 october 13 at 20:56:53 UT, approximately 2.38 hours after the trigger. The observation consisted of 50 exposures of 120 seconds each,with good sky conditions. The mid-exposure time was 22:12:46 UT, and the final exposure ended at 23:32:52 UT. From photometry, we detect the optical counterpart in our images at the following coordinates: R.A (J2000.0) = 23 03 19.712 Dec. (J2000.0) = -00 12 53.17 The measured magnitude at JD 2460962.37284 is: 16.86 +/- 0.06 in V band with SNR 14.98 (AB, calibrated with the GAIA DR3 on SIMBAD). We also obtained a decay curve which, during the period we monitored the object, showed a decline down to magnitude +17.848 +/-0.275 at 23:27:57 UT View this GCN Circular online at https://gcn.nasa.gov/circulars/42251. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40321] GRB 251014A: SAO RAS optical upper limit
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42250 SUBJECT: GRB 251014A: SAO RAS optical upper limit DATE: 25/10/14 10:06:03 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin, O. I. Spiridonova (SAO RAS), report on behalf of GRB follow-up team. We observed the field of the GRB 251014A (Ambrosi et al., GCN 42238; The Fermi GBM team, GCN 42237; de Barra et al., GCN 42249) with the 1-m SAO RAS telescope Zeiss-1000 equipped with the CCD-photometer. We obtained 7 x 300 sec. images in Rc band under mediocre weather conditions on 2025.10.14, 00:51:01--01:38:56 UT (t_mid - T0 = 0.77458 hours). Within our FOV (covers ~80% of northern part of Swift-BAT error circle) we do not detect any new source down to the limiting magnitude of R_lim = 21.5. The field calibrated against nearby USNO-B1.0 stars (R2 magnitudes) and not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42250. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40320] GRB 251014A: Fermi GBM Observation
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42249 SUBJECT: GRB 251014A: Fermi GBM Observation DATE: 25/10/14 09:45:29 GMT FROM: Cuán de Barra at UCD <cuan.debarra(a)ucdconnect.ie> C. de Barra (University College Dublin), J. Smith (UAH), C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 00:28:30.34 UT on 14 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251014A (trigger 782094515/251014020). which was also detected by Swift BAT (E. Ambrosi et al. 2025, GCN 42238). The Fermi GBM on-ground location is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 44 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 1.7 s (50-300 keV). The time-averaged spectrum from T0-0.2 to T0+1.7 s is best fit by a simple power law function with index -1.78 +/- 0.06. The event fluence (10-1000 keV) in this time interval is (6.2 +/- 0.5)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.32 s in the 10-1000 keV band is 6 +/- 1 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/42249. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40319] GRB 251013C: J band observations by SYSU 80cm infrared telescope
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42248 SUBJECT: GRB 251013C: J band observations by SYSU 80cm infrared telescope DATE: 25/10/14 07:17:23 GMT FROM: zhanghr33(a)mail2.sysu.edu.cn Hao-Ran Zhang, Chen Chun, Duo-Le Cao, Zhong-Nan Dong, Wei-Sen Huang, Jin-Ji Li, Jia-Qi Lin, Pu Lin, Yan Yu, Hao-Nan Yang, P H Thomas Tam, Rong-Feng Shen, Bin Ma (Sun Yat-sen University) report on behalf of the SYSU 80cm infrared telescope team: We observed the field of GRB 251013C detected by SVOM (N. A. Rakotondrainibe et al., GCN 42222) and Fermi (Fermi GBM Team, GCN 42221), using the Sun Yat-sen University 80cm infrared telescope with 20 s exposures in J band. The calculated position is R.A. = 345.8301 deg, Dec = -0.2207deg J2000, from SVOM observation. Our observations began at 2025-10-13 18:03:42 UTC, 0.41 hours after the SVOM trigger. We clearly detect an infrared counterpart at the position of the optical afterglow (J. T. Palmerio et al., GCN 42223; I. Perez-Garcia et al., GCN 42225; R. Konno et al., GCN 42226; L. A. Martin-Carrillo et al., GCN 42227; Gianluca Masi, GCN 42228; J. T. Palmerio et al., GCN 42229; A. S. Moskvitin et al., GCN 42230; B. P. Gompertz et al., GCN 42231; V.Lipunov et al., GCN 42235; P. Garnavich, GCN 42240; Alan M. Watson et al., GCN 42241; Diego López-Cámara et al., GCN 42242). The earliest detection is confirmed at 2025-10-13 18:03:42UTC (T – T0 = 0.41 h) with J mag: 13.49+/-0.14 (Vega system). Preliminary photometry shows a rise of ~0.4mag at 18:26:00UTC (T – T0 = 0.78 h), followed by a rapid decay. The photometric calibration was performed using nearby stars from the 2MASS catalog. The photometric accuracy is limited due to the cloudy weather. The SYSU 80cm infrared telescope is operated and managed by the Department of Astronomy, Sun Yat-sen University. View this GCN Circular online at https://gcn.nasa.gov/circulars/42248. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40318] GRB 251013C: EP-FXT counterpart detection
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42247 SUBJECT: GRB 251013C: EP-FXT counterpart detection DATE: 25/10/14 05:55:24 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> B.T. Wang (YNAO, CAS), H. Zhou (PMO, CAS), Z.M. Wang (BNU), P.Y. Han (HUST), R.X. Hu (WHU), D.Z. Du (ZJU), and C.C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 251013C (SVOM/sb25101311, Rakotondrainibe et al., GCN #42222, also detected by Fermi/GBM GCN #42221) at 2025-10-13T19:39:21 (UTC), about 2.0 hours after the SVOM/ECLAIRs trigger, with an exposure time of 1690 s. One uncatalogued source is detected within the ECLAIRs error circle, and the source is spatially consistent with the counterpart reported in optical and X-ray bands (Palmerio et al. GCN #42223, Perez-Garcia et al., GCN #42225, Konno et al., GCN #42226, Masi et al., GCN #42228, Palmerio et al., GCN #42229, Moskvitin et al., GCN #42230, Gompertz et al., GCN #42231, Evans et al., GCN #42232, Garnavich et al., GCN #42240, Watson et al., GCN #42241, López-Cámara et al., GCN #42242) with redshift at 0.572 (Martin-Carrillo et al., GCN #42227). Preliminary analysis on this source are automatically conducted, and details are listed as follows. Source 1: EPF_J230320.5-001237 RA (J2000): 345.8356 Dec (J2000): -0.2103 Flux: 3.75 x 10^-10 erg/s/cm2 (observed, 0.5-10 keV) Flux_err: 7.89 x 10^-12 erg/s/cm2 (1 sigma) The position uncertainty of the source is about 10 arcsec in radius (90% C.L. statistical and systematic). 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/42247. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40317] GRB 251013C: AstroSat CZTI detection
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42246 SUBJECT: GRB 251013C: AstroSat CZTI detection DATE: 25/10/14 05:53:26 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> A. Arya (IITB), U. Pathak (IITB), A. Goyal (IITB), Harsha K. H. (IUCAA), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long GRB 251013C which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 42221), and SVOM/ECLAIRs (Rakotondrainibe et. al., GCN Circ. 42222). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-10-13 17:39:42.75 UTC. The measured peak count rate associated with the burst is 87 (+43, -15) counts/s above the background in the combined data of three quadrants (out of four), with a total of 337 (+89, -97) counts. The local mean background count rate was 202 (+3, -3) counts/s. Using cumulative rates, we measure a T90 of 7.3 (+0.7, -1.1) s. We caution that there is a 0.3 s dead time in the CZTI data just after the burst, hence the actual T90 may be slightly longer. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-10-13 17:39:42.33 UTC. The measured peak count rate associated with the burst is 281 (+68, -36) counts/s above the background in the combined data of all quadrants, with a total of 1351 (+229, -274) counts. The local mean background count rate was 1171 (+6, -9) counts/s. We measure a T90 of 6.7 (+0.8, -1.8) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/42246. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40316] GRB 251011A: Swift/BAT-GUANO arcminute localization of a burst
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42245 SUBJECT: GRB 251011A: Swift/BAT-GUANO arcminute localization of a burst DATE: 25/10/14 05:15:00 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Aaron Tohuvavohu (Caltech), Jamie A. Kennea (PSU), Samuele Ronchini (GSSI), Gayathri Raman (PSU), Tyler Parsotan (GSFC), Maia Williams (Northwestern) report: Swift/BAT did not localize GRB 251011A onboard (T0: 2024-10-11T03:41:40.09 UTC, Fermi GCN 42195, AstroSat CZTI GCN 42199, Insight-HXMT GCN 42210). The Fermi/GBM 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 arcmin position of the burst is found with the newly developed pipeline BAT-GLIMPSE: Gamma-ray Localization using Imaging and Mosaic techniques for Pointing and Slew Epochs (Ronchini et. al, in prep). The pipeline makes use of the tools from BatAnalysis (Parsotan et al. 2025). A confident location is found for the burst with SNR of 23.5. The burst is detected in BAT with a duration of ~ 5 seconds. The BAT position is RA, Dec = 4.7878, +45.1894 deg which is RA(J2000) = 00h 19m 09.07s Dec(J2000) = +45d 11’ 21.84″ with an estimated uncertainty of 5 arcmin. This position is consistent with the Ferm/GBM localization (GCN 42195). 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/42245. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40315] GRB 251013D: Swift/BAT-GUANO arcminute localization of a burst
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42244 SUBJECT: GRB 251013D: Swift/BAT-GUANO arcminute localization of a burst DATE: 25/10/14 04:52:39 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Aaron Tohuvavohu (Caltech), Samuele Ronchini (GSSI), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (Northwestern) report: Swift/BAT did not localize GRB 251013D onboard (T0: 2025-10-13T18:17:00.39 UTC, Fermi Trig 782072225). 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 BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), detects the burst in a 16.384 s analysis time bin starting at T0 - 0.0 s with a sqrt(TS) of 27.6. An arcminute localization is found with DeltaLLHOut of 159 and a DeltaLLHPeak of 130. See Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief descriptions and interpretations of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut. The BAT position is RA, Dec = 46.901, 8.800 deg which is RA(J2000) = 03h 07m 36.24s Dec(J2000) = 8d 48’ 00.0″ with an estimated uncertainty of 5 arcmin radius. More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=782072256 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/42244. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40314] GRB 251013C: ALMA detection
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42243 SUBJECT: GRB 251013C: ALMA detection DATE: 25/10/14 03:51:49 GMT FROM: Tanmoy Laskar at U of Utah <tanmoylaskar(a)gmail.com> T. Laskar (University of Utah), C. Christy, N. Franz, K. D. Alexander (University of Arizona), E. Berger (Harvard University), R. Chornock (UC Berkeley), H. J. van Eerten (University of Bath), G. Farley (U. Utah), W. Fong (Northwestern University), R. Gill (UNAM), J. Granot (Open University), R. Margutti (UC Berkeley), and P. Schady (University of Bath) report: “We observed GRB 251013C (Fermi GBM team, GCN 42221; Rakotondrainibe et al., GCN 42222) with the Atacama Large Millimeter/Submillimeter Array (ALMA) at 97.5 GHz beginning on 2025 October 13 at 23:07 UT (5.5 hours after the burst). Preliminary analysis reveals a mm source with flux density of ~ 0.3 mJy at position: RA (J2000) = 23:03:20.56 Dec (J2000) = -00:12:37.21 with an uncertainty of 0.02" in each coordinate. This is consistent with the X-ray position (Rakotondrainibe et al., GCN 42222; Evans et al., GCN 42232) and optical position (Palmerio et al., GCN 42223; Masi et al., GCN 42228). Further observations are planned. We thank the NAASC staff, P2G, AoD, JAO staff, and the entire ALMA team for their help with these observations." View this GCN Circular online at https://gcn.nasa.gov/circulars/42243. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40313] GRB 251013C: SVOM/COLIBRÍ (FM-GFT) detection of the optical counterpart
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42242 SUBJECT: GRB 251013C: SVOM/COLIBRÍ (FM-GFT) detection of the optical counterpart DATE: 25/10/14 03:33:15 GMT FROM: Diego López-Cámara at Instituto de Ciencias Nucleares, UNAM <diego(a)correo.nucleares.unam.mx> Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Alan M. Watson (UNAM), Camila Angulo (UNAM), Ny Avo Rakotondrainibe (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the SVOM GRB 251013C (Rakotondrainibe et al., GCN Circ. 42222) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We obtained a 60 seconds exposure in the r filter starting at 2025-10-14 02:18 (8.65 hours after the trigger). The image was analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS catalog, is in the AB system, and is not corrected for Galactic extinction. We detected the optical counterpart, (Palmerio et al., GCN Circ. 42223; Perez-Garcia et al., GCN Circ. 42225; Konno et al., GCN Circ. 42226; Martin-Carrillo et al., GCN Circ. 42227; Masi et al., GCN Circ. 42228; Palmerio et al., GCN Circ. 42229; Moskvitin et al., GCN Circ. 42230; Gompertz et al., GCN Circ. 42231; Lipunov et al., GCN Circ. 42235; and Garnavich et al., GCN Circ. 42240; Watson et al. GCN Circ. 42241) with a preliminary magnitude of: r = 18.50 +/- 0.03 Compared to the observation reported by Garnevich (GCN Circ. 42240), our observation suggests an abrupt fading between 6.4 and 8.7 hours. Further observations and analysis are ongoing. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/42242. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40312] GRB 251013C: DDOTI detection of the optical afterglow
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42241 SUBJECT: GRB 251013C: DDOTI detection of the optical afterglow DATE: 25/10/14 03:26:13 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Rosa L. Becerra (U Roma), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report: We observed the field of GRB 251013C detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 42221) and SVOM/ECLAIRS (Rakotondrainibe et al., GCN Circ. 42222) with the DDOTI wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) from 2025-10-14 02:41 to 03:08 (8.80 to 9.45 hours after the trigger) and obtained a total of 23 minutes of exposure in the w filter. We detect the optical afterglow (Palmerio et al., GCN Circ. 42223; Perez-Garcia et al., GCN Circ. 42225; Konno et al., GCN Circ. 42226; Martin-Carrillo et al., GCN Circ. 42227; Masi et al., GCN Circ. 42228; Palmerio et al., GCN Circ. 42229; Moskvitin et al., GCN Circ. 42230; Gompertz et al., GCN Circ. 42231; Lipunov et al., GCN Circ. 42235; and Garnavich et al., GCN Circ. 42240) with a preliminary magnitude of w = 18.95 +/- 0.04 Our photometry is calibrated against the USNO-B1 and Pan-STARRS PS1 DR2 catalogues and is not corrected for Galactic extinction. Observations are continuing. We thank the staff of the Observatorio Astronómico Nacional at the Sierra de San Pedro Mártir for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/42241. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40311] GRB 20251013C: SLKT optical afterglow photometry
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42240 SUBJECT: GRB 20251013C: SLKT optical afterglow photometry DATE: 25/10/14 02:43:16 GMT FROM: Peter Garnavich at U of Notre Dame <pgarnavi(a)nd.edu> P. Garnavich (University of Notre Dame) reports: The Sarah L. Krizmanich Telescope (SLKT) obtained unfiltered observations of the SVOM/ECLAIRs source GRB 251013C (Rakotondrainibe et al., GCN 42222). Imaging was centered at 2025 October 14.002 (UT) which was 6.4 hours after the GRB trigger. Exposures totaled 320s and the afterglow was clearly detected. Compared to the nearby star at 23:03:20.64 -00:10:13.8 (2000) with a SDSS magnitude of r=14.40 mag, the afterglow had a brightness of r=17.48+/-0.06 mag. View this GCN Circular online at https://gcn.nasa.gov/circulars/42240. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40310] Swift GRB 251014A: Global MASTER-Net observations report
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42239 SUBJECT: Swift GRB 251014A: Global MASTER-Net observations report DATE: 25/10/14 00:47:01 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 Swift GRB 251014A ( E. Ambrosi et al., GCN 42238) errorbox 26 sec after notice time and 361 sec after trigger time at 2025-10-14 00:34:31 UT, with upper limit up to 18.5 mag. The observations began at zenith distance = 68 deg. The sun altitude is -39.4 deg. The galactic latitude b = 11 deg., longitude l = 212 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3014236 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 391 | MASTER-SAAO | C | 60 | 18.5 | 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/42239. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40309] GRB 251014A: Swift detection of a possibly-short burst
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42238 SUBJECT: GRB 251014A: Swift detection of a possibly-short burst DATE: 25/10/14 00:42:58 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> E. Ambrosi (INAF-IASFPA), V. D'Elia (SSDC & INAF-OAR), R. Gupta (NASA GSFC) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: At 00:28:30 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 251014A (trigger=1403878). Swift did not slew immediately due to an observation constraint. The BAT on-board calculated location is RA, Dec 111.732, +6.415 which is RA(J2000) = 07h 26m 56s Dec(J2000) = +06d 24' 54" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 1.5 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger. Due to a Moon observing constraint, Swift cannot slew to the BAT position until 21:52 UT on 2025 October 14. There will thus be no XRT or UVOT data for this trigger before this time. Burst Advocate for this burst is E. Ambrosi (elena.ambrosi AT inaf.it). 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/42238. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40308] GRB 251014A: Fermi GBM Final Real-time Localization
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42237 SUBJECT: GRB 251014A: Fermi GBM Final Real-time Localization DATE: 25/10/14 00:39:10 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 SHORT GRB At 00:28:30 UT on 14 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251014A (trigger 782094515.336852 / 251014020). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 114.7, Dec = 7.4 (J2000 degrees, equivalent to J2000 07h 38m, 7d 24'), with a statistical uncertainty of 8.3 degrees. The angle from the Fermi LAT boresight is 45.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251014020/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251014020/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251014020/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42237. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40307] Fermi trigger No 782044789: Global MASTER-Net observations report
by GCN Circulars 14 Oct '25

14 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42236 SUBJECT: Fermi trigger No 782044789: Global MASTER-Net observations report DATE: 25/10/14 00:15:33 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB251013.44 (trigger No 782044789,16h 21m 00.00s , -23d 58m 58.8s, R=50) errorbox 46947 sec after notice time and 46980 sec after trigger time at 2025-10-13 23:42:44 UT, with upper limit up to 19.5 mag. Observations started at twilight. The observations began at zenith distance = 6 deg. The sun altitude is -13.0 deg. The galactic latitude b = 18 deg., longitude l = 353 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3013722 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 47010 | 2025-10-13 23:42:44 | MASTER-OAFA | (20h 11m 08.20s , -31d 38m 07.6s) | C | 60 | 19.5 | 47086 | 2025-10-13 23:44:00 | MASTER-OAFA | (20h 11m 08.28s , -31d 39m 50.4s) | C | 60 | 19.3 | 47162 | 2025-10-13 23:45:15 | MASTER-OAFA | (20h 11m 12.39s , -31d 38m 20.4s) | C | 60 | 19.5 | 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/42236. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40306] Fermi GRB 251013C: Global MASTER-Net observations report
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42235 SUBJECT: Fermi GRB 251013C: Global MASTER-Net observations report DATE: 25/10/13 23:46:00 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 251013C ( Fermi GBM team, GCN 42221) errorbox 10000 sec after notice time and 10034 sec after trigger time at 2025-10-13 20:26:56 UT, with upper limit up to 20.4 mag. The observations began at zenith distance = 32 deg. The sun altitude is -41.1 deg. The galactic latitude b = -59 deg., longitude l = 72 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3013941 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 10064 | 2025-10-13 20:26:56 | MASTER-SAAO | (23h 02m 39.24s , -00d 30m 39.4s) | C | 60 | 18.6 | 10158 | 2025-10-13 20:28:29 | MASTER-SAAO | (23h 02m 46.41s , -00d 31m 36.1s) | C | 60 | 18.7 | 10251 | 2025-10-13 20:30:02 | MASTER-SAAO | (23h 02m 40.37s , -00d 32m 32.6s) | C | 60 | 18.9 | 10345 | 2025-10-13 20:31:37 | MASTER-SAAO | (23h 02m 47.55s , -00d 32m 05.9s) | C | 60 | 18.8 | 10441 | 2025-10-13 20:33:12 | MASTER-SAAO | (23h 02m 45.46s , -00d 30m 49.0s) | C | 60 | 18.7 | 10539 | 2025-10-13 20:34:50 | MASTER-SAAO | (23h 02m 46.25s , -00d 32m 02.3s) | C | 60 | 18.6 | 10664 | 2025-10-13 20:36:25 | MASTER-SAAO | (23h 02m 49.67s , -00d 30m 22.6s) | C | 120 | 18.9 | 10817 | 2025-10-13 20:38:58 | MASTER-SAAO | (23h 02m 45.08s , -00d 31m 17.6s) | C | 120 | 18.8 | 10980 | 2025-10-13 20:41:42 | MASTER-SAAO | (23h 02m 47.31s , -00d 30m 13.8s) | C | 120 | 19.0 | 11135 | 2025-10-13 20:44:17 | MASTER-SAAO | (23h 02m 52.66s , -00d 31m 09.8s) | C | 120 | 19.0 | 11292 | 2025-10-13 20:46:54 | MASTER-SAAO | (23h 02m 47.94s , -00d 32m 05.5s) | C | 120 | 19.2 | 11446 | 2025-10-13 20:49:27 | MASTER-SAAO | (23h 02m 55.30s , -00d 32m 00.3s) | C | 120 | 19.2 | 11630 | 2025-10-13 20:52:01 | MASTER-SAAO | (23h 02m 53.52s , -00d 30m 03.7s) | C | 180 | 19.2 | 11847 | 2025-10-13 20:55:39 | MASTER-SAAO | (23h 02m 54.71s , -00d 31m 32.8s) | C | 180 | 19.2 | 12064 | 2025-10-13 20:59:15 | MASTER-SAAO | (23h 02m 58.96s , -00d 29m 55.7s) | C | 180 | 19.4 | 12247 | 2025-10-13 21:02:48 | MASTER-SAAO | (23h 02m 53.36s , -00d 30m 39.0s) | C | 120 | 19.4 | 12399 | 2025-10-13 21:05:21 | MASTER-SAAO | (23h 02m 55.07s , -00d 29m 35.0s) | C | 120 | 19.4 | 12519 | 2025-10-13 21:05:21 | MASTER-SAAO | (23h 02m 55.07s , -00d 29m 35.0s) | C | 360 | 20.1 | Coadd 12554 | 2025-10-13 21:07:55 | MASTER-SAAO | (23h 03m 01.04s , -00d 30m 30.6s) | C | 120 | 19.4 | 12722 | 2025-10-13 21:10:43 | MASTER-SAAO | (23h 02m 55.49s , -00d 31m 25.3s) | C | 120 | 19.7 | 12875 | 2025-10-13 21:13:16 | MASTER-SAAO | (23h 03m 01.00s , -00d 31m 12.9s) | C | 120 | 19.4 | 12995 | 2025-10-13 21:13:16 | MASTER-SAAO | (23h 03m 01.00s , -00d 31m 12.9s) | C | 360 | 20.4 | Coadd 13030 | 2025-10-13 21:15:51 | MASTER-SAAO | (23h 02m 59.29s , -00d 29m 35.6s) | C | 120 | 19.7 | 13194 | 2025-10-13 21:18:36 | MASTER-SAAO | (23h 02m 59.68s , -00d 30m 53.7s) | C | 120 | 19.6 | 13347 | 2025-10-13 21:21:09 | MASTER-SAAO | (23h 03m 02.87s , -00d 29m 15.8s) | C | 120 | 19.9 | 13502 | 2025-10-13 21:23:44 | MASTER-SAAO | (23h 02m 57.06s , -00d 30m 00.8s) | C | 120 | 19.8 | 16491 | 2025-10-13 22:14:02 | MASTER-SAAO | (23h 07m 20.08s , -06d 42m 29.2s) | C | 60 | 18.9 | 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/42235. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40305] Fermi GRB 251013C: Global MASTER-Net observations report
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42235 SUBJECT: Fermi GRB 251013C: Global MASTER-Net observations report DATE: 25/10/13 23:46:00 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 251013C ( Fermi GBM team, GCN 42221) errorbox 10000 sec after notice time and 10034 sec after trigger time at 2025-10-13 20:26:56 UT, with upper limit up to 20.4 mag. The observations began at zenith distance = 32 deg. The sun altitude is -41.1 deg. The galactic latitude b = -59 deg., longitude l = 72 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3013941 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 10064 | 2025-10-13 20:26:56 | MASTER-SAAO | (23h 02m 39.24s , -00d 30m 39.4s) | C | 60 | 18.6 | 10158 | 2025-10-13 20:28:29 | MASTER-SAAO | (23h 02m 46.41s , -00d 31m 36.1s) | C | 60 | 18.7 | 10251 | 2025-10-13 20:30:02 | MASTER-SAAO | (23h 02m 40.37s , -00d 32m 32.6s) | C | 60 | 18.9 | 10345 | 2025-10-13 20:31:37 | MASTER-SAAO | (23h 02m 47.55s , -00d 32m 05.9s) | C | 60 | 18.8 | 10441 | 2025-10-13 20:33:12 | MASTER-SAAO | (23h 02m 45.46s , -00d 30m 49.0s) | C | 60 | 18.7 | 10539 | 2025-10-13 20:34:50 | MASTER-SAAO | (23h 02m 46.25s , -00d 32m 02.3s) | C | 60 | 18.6 | 10664 | 2025-10-13 20:36:25 | MASTER-SAAO | (23h 02m 49.67s , -00d 30m 22.6s) | C | 120 | 18.9 | 10817 | 2025-10-13 20:38:58 | MASTER-SAAO | (23h 02m 45.08s , -00d 31m 17.6s) | C | 120 | 18.8 | 10980 | 2025-10-13 20:41:42 | MASTER-SAAO | (23h 02m 47.31s , -00d 30m 13.8s) | C | 120 | 19.0 | 11135 | 2025-10-13 20:44:17 | MASTER-SAAO | (23h 02m 52.66s , -00d 31m 09.8s) | C | 120 | 19.0 | 11292 | 2025-10-13 20:46:54 | MASTER-SAAO | (23h 02m 47.94s , -00d 32m 05.5s) | C | 120 | 19.2 | 11446 | 2025-10-13 20:49:27 | MASTER-SAAO | (23h 02m 55.30s , -00d 32m 00.3s) | C | 120 | 19.2 | 11630 | 2025-10-13 20:52:01 | MASTER-SAAO | (23h 02m 53.52s , -00d 30m 03.7s) | C | 180 | 19.2 | 11847 | 2025-10-13 20:55:39 | MASTER-SAAO | (23h 02m 54.71s , -00d 31m 32.8s) | C | 180 | 19.2 | 12064 | 2025-10-13 20:59:15 | MASTER-SAAO | (23h 02m 58.96s , -00d 29m 55.7s) | C | 180 | 19.4 | 12247 | 2025-10-13 21:02:48 | MASTER-SAAO | (23h 02m 53.36s , -00d 30m 39.0s) | C | 120 | 19.4 | 12399 | 2025-10-13 21:05:21 | MASTER-SAAO | (23h 02m 55.07s , -00d 29m 35.0s) | C | 120 | 19.4 | 12519 | 2025-10-13 21:05:21 | MASTER-SAAO | (23h 02m 55.07s , -00d 29m 35.0s) | C | 360 | 20.1 | Coadd 12554 | 2025-10-13 21:07:55 | MASTER-SAAO | (23h 03m 01.04s , -00d 30m 30.6s) | C | 120 | 19.4 | 12722 | 2025-10-13 21:10:43 | MASTER-SAAO | (23h 02m 55.49s , -00d 31m 25.3s) | C | 120 | 19.7 | 12875 | 2025-10-13 21:13:16 | MASTER-SAAO | (23h 03m 01.00s , -00d 31m 12.9s) | C | 120 | 19.4 | 12995 | 2025-10-13 21:13:16 | MASTER-SAAO | (23h 03m 01.00s , -00d 31m 12.9s) | C | 360 | 20.4 | Coadd 13030 | 2025-10-13 21:15:51 | MASTER-SAAO | (23h 02m 59.29s , -00d 29m 35.6s) | C | 120 | 19.7 | 13194 | 2025-10-13 21:18:36 | MASTER-SAAO | (23h 02m 59.68s , -00d 30m 53.7s) | C | 120 | 19.6 | 13347 | 2025-10-13 21:21:09 | MASTER-SAAO | (23h 03m 02.87s , -00d 29m 15.8s) | C | 120 | 19.9 | 13502 | 2025-10-13 21:23:44 | MASTER-SAAO | (23h 02m 57.06s , -00d 30m 00.8s) | C | 120 | 19.8 | 16491 | 2025-10-13 22:14:02 | MASTER-SAAO | (23h 07m 20.08s , -06d 42m 29.2s) | C | 60 | 18.9 | 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/42235. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40304] Fermi GRB 251013B: Global MASTER-Net observations report
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42234 SUBJECT: Fermi GRB 251013B: Global MASTER-Net observations report DATE: 25/10/13 23:31:09 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 251013B ( Fermi GBM team, GCN 42215) errorbox 48818 sec after notice time and 48841 sec after trigger time at 2025-10-13 21:58:28 UT, with upper limit up to 19.4 mag. The observations began at zenith distance = 41 deg. The sun altitude is -49.5 deg. The galactic latitude b = -52 deg., longitude l = 97 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3013666 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 48872 | 2025-10-13 21:58:28 | MASTER-SAAO | (23h 34m 30.91s , +04d 40m 04.5s) | C | 60 | 19.4 | 48872 | 2025-10-13 21:58:29 | MASTER-SAAO | (23h 32m 43.17s , +04d 55m 22.1s) | C | 60 | 19.2 | 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/42234. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40303] Fermi GRB 251013D: Global MASTER-Net observations report
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42233 SUBJECT: Fermi GRB 251013D: Global MASTER-Net observations report DATE: 25/10/13 22:31:33 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 251013D ( Fermi GBM team, GCN 42224) errorbox 12470 sec after notice time and 12506 sec after trigger time at 2025-10-13 21:45:26 UT, with upper limit up to 19.2 mag. The observations began at zenith distance = 54 deg. The sun altitude is -48.9 deg. The galactic latitude b = -41 deg., longitude l = 167 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3013985 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 12536 | 2025-10-13 21:45:26 | MASTER-SAAO | (02h 43m 45.87s , +12d 29m 46.5s) | C | 60 | 18.9 | 12536 | 2025-10-13 21:45:26 | MASTER-SAAO | (02h 45m 35.22s , +12d 14m 30.3s) | C | 60 | 19.0 | 12729 | 2025-10-13 21:48:39 | MASTER-SAAO | (02h 42m 32.93s , +10d 34m 14.1s) | C | 60 | 19.1 | 12729 | 2025-10-13 21:48:39 | MASTER-SAAO | (02h 44m 21.71s , +10d 18m 58.2s) | C | 60 | 19.2 | 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/42233. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40302] GRB 251013C: Swift-XRT counterpart detection
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42232 SUBJECT: GRB 251013C: Swift-XRT counterpart detection DATE: 25/10/13 22:23:39 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 251013C (Rakotondrainibe et al., GCN 42222), collecting 1.8 ks of Photon Counting (PC) mode data between T0+344 s and T0+5.5 ks after the trigger. A bright, fading counterpart has been found, coincident with the VT optical, fading source reported by Palmerio et al. (GCN 42223), which has a redshift of 0.572 (Martin-Carrillo et al., GCN 42227). Thus, we can conclude that this is the XRT counterpart of GRB 251013C. The details of this source are: Source 1 (SWIFT J230320.5-001235): ================================== RA (J2000.0): 345.8358 = 23 03 20.59 Dec (J2000.0): -0.2100 = -00 12 36.0 Error: 3.5 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 3.6 arcmin from the SVOM/ECLAIRs position. Mean rate: 2.356 +/- 0.081 ct s^-1 Mean flux: (8.71 +/- 0.30)e-11 erg cm^-2 s^-1 Peak rate: 10.2 +/- 1.9 ct s^-1 Peak flux: (3.76 +/- 0.69)e-10 erg cm^-2 s^-1 ECF: 3.70e-11 erg cm^-2 ct^-1 assuming NH=6.48e+20 cm^-2, gamma=1.78 determined from a spectral fit. XMM UL: 6.3e-13 erg cm^-2 s^-1, (0.3-10 keV) so the source is 5.4-sigma above this 3-sigma upper limit. 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_FIELD00041. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42232. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40301] GRB 251013C: GOTO optical afterglow detection
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42231 SUBJECT: GRB 251013C: GOTO optical afterglow detection DATE: 25/10/13 22:14:00 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk> B. P. Gompertz, B. Godson, D. O'Neill, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. K. Galloway, V. Dhillon, G. Ramsay, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 251013C (Fermi GBM Team, GCN 42221; Rakotondrainibe et al, GCN 42222). Targeted observations were taken at 2025-10-13 21:40:06 UT (4.1h post trigger). The observations consisted of 4x45s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. We detect the optical counterpart (Palmerio et al., GCN 42223; Perez-Garcia et al., GCN 42225; Konno et al., GCN 42226; Martin-Carrillo et al., GCN 42227; Masi, GCN 42228; Palmerio et al., GCN 42229; Moskvitin et al., GCN 42230) with an AB magnitude of L = 17.11 ± 0.02 mag. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/42231. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40300] GRB 251013C: SAO RAS optical observations
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42230 SUBJECT: GRB 251013C: SAO RAS optical observations DATE: 25/10/13 21:31:40 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin, O. I. Spiridonova, V. V. Vlasyuk (SAO RAS), N. Pankov (HSE, IKI), A. Pozanenko (IKI), A. Ghosh, S. Razzaque (CAPP, University of Johannesburg), Tao An and Yuanqi Liu (Shanghai Astronomical Observatory) report on behalf of GRB follow-up collaboration and IKI-GRB-FuN. We observed the field of the GRB 251013C (The Fermi GBM team, GCN 42221; Rakotondrainibe et al., GCN 42222) with the 1-m SAO RAS telescope Zeiss-1000 equipped with the CCD-photometer. The observations started on 2025.10.13T19:47:54 UT (t_mid - T0 = 2.1369 hours). The OT (Palmerio et al., GCN 42223; Perez-Garcia et al., GCN 42225; Konno et al., GCN 42226; Martin-Carrillo et al., GCN 42227; Masi, GCN 42228; Palmerio et al, GCN 42229) is clearly detected in the individual images with the following brightness. Date UT start t-T0 Exp. Filter OT Err. (mid, d) (s) 2025.10.13 19:47:54 0.03631 300 Rc 15.84 +/- 0.01 2025.10.13 20:04:02 0.04033 100 Rc 16.05 +/- 0.01 2025.10.13 20:15:34 0.04353 100 Rc 16.21 +/- 0.01 Preliminary photometry is based on the nearby SDSS objects (magnitudes converted with Lupton 2005 equations) and has not corrected for the Galactic extinction. The observations with the 1-m telescope in BVRI filters and also with the 0.5-m telescope AS-500/2 are ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/42230. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40299] GRB 251013C: LCO optical afterglow detection
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42229 SUBJECT: GRB 251013C: LCO optical afterglow detection DATE: 25/10/13 21:13:53 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> J. T. Palmerio, D. Turpin, A. Saccardi, B. Cordier (CEA/Irfu), L. P. Xin (NAOC), C. Wu (NAOC), report on behalf of the SVOM mission team: We observed the field of GRB 251013C (SVOM/ECLAIRs and GRM, Rakotondrainibe et al. GCN 42223; Fermi/GBM, Fermi GBM team, GCN 42221) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument. Our observation started at 2025-10-13T19:27:33.084 about 1.8 hours after the SVOM/ECLAIRs T0 time. We obtained 3 series of 3x200 s exposures in the SDSS gri filters. The bright optical counterpart detected by SVOM/VT (Palmerio et al. GCN 42223), BOOTES-6 (Perez-Garcia et al., GCN 42225), LAST (Konno et al., GCN 42226), NOT (Martin-Carrillo et al., GCN 42227 and the Visual Telescope Project (Masi et al., GCN 42228) is clearly detected in our first images subtracted to the Pan-STARRS DR2 catalog image. We measure the following magnitude: g = 16.30 +/- 0.01 (AB), at Tmid-T0 = 2.1 hours r = 15.99 +/- 0.01 (AB), at Tmid-T0 = 2.0 hours i = 15.70 +/- 0.01 (AB), at Tmid-T0 =1.8 hours Further observations are planned and spectroscopic observations are encouraged. This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/42229. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40298] GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42228 SUBJECT: GRB 251013C: Optical Observations via Virtual Telescope Project, Italy DATE: 25/10/13 21:07:58 GMT FROM: Gianluca Masi at Virtual Telescope Project <gianluca(a)bellatrixobservatory.org> Gianluca Masi, Virtual Telescope Project (Italy), reports: We attempted to observe the optical counterpart of GRB 251013C (Rakotondrainibe et al., GCN 42222) with the 14” robotic unit available at the Virtual Telescope Project facility in Manciano, Italy, equipped with a KAF-3200E based CCD camera, its QE peaking (90%) in the red part of the spectrum. We collected three, 120-second unfiltered exposures, then we averaged them. The central time of the resulting stack was 13 Oct., 20:54:57 UTC, that is about 3.25 hours after the burst. We detected a bright object at the following position (J2000.0): R.A.: 23 03 20.56 Decl.: -00 13 37.1 mean residuals < 1” on both axes R= 15.9 (assuming R-mags from Gaia DR2 for the reference stars). This position is consistent with Palmerio et al. (GCN 42223)and Perez-Garcia et al., GCN 42225. View this GCN Circular online at https://gcn.nasa.gov/circulars/42228. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40297] GRB 251013C: NOT spectroscopic redshift z = 0.572
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42227 SUBJECT: GRB 251013C: NOT spectroscopic redshift z = 0.572 DATE: 25/10/13 21:02:05 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> A. Martin-Carrillo (UCD), L. Izzo (INAF/OACN and DARK/NBI), D. B. Malesani (DAWN/NBI and Radboud), G. Corcoran (UCD), B. Schneider (LAM), A. de Ugarte Postigo (LAM), A. Saccardi (CEA/Irfu), B. P. Gompertz (Birmingham), K. Valeckas (NOT and NBI) report on behalf of a larger collaboration: We observed the optical afterglow (Palmerio et al., GCN 42223; Perez-Garcia et al., GCN 42225; Konno et al., GCN 42226) of GRB 251013C (Rakotondrainibe et al., GCN 42222; Fermi GBM team, GCN 42221) with the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. A spectrum using grism #4 was secured starting on 2025-10-13 at 19:46:24 UT (2.11 hr after the GRB), under good conditions. The exposure time was 2x1200 s and the covered wavelength range is 3500-9600 AA. In a preliminary reduction of the spectra, we clearly detect a continuum over the whole covered wavelength range. From the detection of multiple absorption features, including Fe II 2600, the Mg II doublet, weak Mg I, and the Ca II doublet, we infer a redshift of z = 0.572. Photometry of the afterglow was carried out in the ugriz filters. In a 30-s r-band image, we measure r = 16.52 +/- 0.02 AB (at a time of 2.88 hr after the GRB), calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42227. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40296] GRB 251013C: LAST detection of optical counterpart
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42226 SUBJECT: GRB 251013C: LAST detection of optical counterpart DATE: 25/10/13 20:58:35 GMT FROM: Ruslan Konno at Weizmann Institute of Science <ruslankonno(a)gmail.com> R. Konno (WIS), S. Garrappa (WIS), E. A. Zimmerman (WIS), A. Horowicz (WIS), E. O. Ofek (WIS), S. Ben-Ami (WIS), D. Polishook (WIS), O. Yaron (WIS), S. Fainer (WIS), A. Krassilchtchikov (WIS), Y. M. Shani (WIS), E. Segre (WIS), A. Gal-Yam (WIS), and S. Spitzer (WIS) report on behalf of the LAST Collaboration. We report observations of GRB 251013C, detected by SVOM (Rakotondrainibe et al., GCN 42222) and Fermi (Fermi GBM Team, GCN 42221). Observations were conducted with the Large Array Survey Telescope (LAST; Ofek et al. 2023, PASP 135, 5001; Ben-Ami et al. 2023, PASP 135, 5002). We observed the field of GRB 251013C using four parallel telescopes (each with a 7.4 deg^2 FoV) in clear band (similar to the Gaia Bp band) over several epochs. Each coadd consists of 20x20 s exposures, yielding a limiting magnitude of about 20.5 AB mag. We clearly detect the optical counterpart reported by Palmerio et al. (GCN 42223) and Perez-Garcia et al. (GCN 42225). The earliest detection (20x20 s coadd) is confirmed at 2025-10-13 18:10:27 UTC (T − T0 = 0.51 h) with AB mag 16.14 +/- 0.02. Preliminary automated photometry shows a rise to 15.20 +/- 0.01 mag at 18:32:15 UTC (T − T0 = 0.87 h), followed by a power-law decay. The source remains detectable. We encourage continued multi-wavelength follow-up of this bright optical counterpart. LAST is a survey telescope array of the Weizmann Astrophysical Observatory (https://www.weizmann.ac.il/wao/) View this GCN Circular online at https://gcn.nasa.gov/circulars/42226. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40295] GRB 251013C: BOOTES-6 early optical detection
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42225 SUBJECT: GRB 251013C: BOOTES-6 early optical detection DATE: 25/10/13 19:07:16 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es> I. Perez-Garcia, S.-Y. Wu, E. Fernandez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), P. J. Meintjes and H. J. van Heerden (UFS, South Africa), A. Martin-Carrillo and L. Hanlon (UCD, Ireland), M. Gritsevich (Univ. of Helsinki) and C. J. Perez del Pulgar (UMA, Malaga), on behalf of a larger collaboration, report: Following the detection of GRB 251013C by SVOM (Rakotondrainibe et al., GCN 42222), the BOOTES-6/DPRT 0.6m robotic telescope at Boyden Observatory in Maselspoort (South Africa) responded to this high-energy event starting on Oct 13, 17:42:32 UT (i.e., 170 sec after detection). Series of images in clear filter were gathered and we detect an optical source consistent with the one reported by Palmerio et al. (GCN 42223). Using GaiaDR3 Gmag as reference we report our photometry analysis: | UT mid exposure | mag | error | filter | exposure time (sec) | | ------------------- | ----- | ----- | ------ | ------------------- | | 2025-10-13 17:43:02 | 14.42 | 0.02 | clear | 60 | | 2025-10-13 17:44:31 | 14.82 | 0.02 | clear | 60 | | 2025-10-13 17:50:23 | 14.79 | 0.03 | clear | 60 | | 2025-10-13 17:51:52 | 15.03 | 0.02 | clear | 60 | | 2025-10-13 17:57:44 | 15.77 | 0.03 | clear | 60 | | 2025-10-13 17:59:13 | 15.79 | 0.03 | clear | 60 | | 2025-10-13 18:05:04 | 16.07 | 0.03 | clear | 60 | Further analysis of the additional images is ongoing. We thank the staff at Boyden Observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/42225. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40294] GRB 251013D: Fermi GBM Final Real-time Localization
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42224 SUBJECT: GRB 251013D: Fermi GBM Final Real-time Localization DATE: 25/10/13 18:27:33 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 18:17:00 UT on 13 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251013D (trigger 782072225.388414 / 251013762). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 44.4, Dec = 10.2 (J2000 degrees, equivalent to J2000 02h 57m, 10d 11'), with a statistical uncertainty of 5.4 degrees. The angle from the Fermi LAT boresight is 73.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013762/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013762/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013762/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42224. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40293] GRB 251013C: SVOM/VT optical observation
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42223 SUBJECT: GRB 251013C: SVOM/VT optical observation DATE: 25/10/13 18:18:36 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> J. T. Palmerio (CEA/Irfu), Ny Avo Rakotondrainibe, C. Adami (LAM), H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu (NAOC) report on behalf of the SVOM/VT team: After the trigger by SVOM/ECLAIRs at 2025-10-13T17:39:42 UTC (T0), SVOM performed an automatic slew on the burst location (Rakotondrainibe et al., GCN 42222). SVOM/VT began observing the field at 2025-10-13T17:44:04, 261.08 seconds after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. From a preliminary analysis of the 1-bit subimage and source list downloaded via VHF network, at least one credible candidate is identified, the details of which are presented below. VT_ID 117: This bright candidate was flagged as a catalogued source but significantly brighter than its catalogued magnitude. The position of this candidate is R.A., Dec. 345.8356, -0.2103 degrees, corresponding to: R.A. (J2000) = 23h03m20.6s Dec. (J2000) = -0d12m37.1s with an uncertainty of 0.5 arcsec. This location is within the R90 uncertainty region of the SVOM/MXT onboard localization. The source was detected in both VT_R and VT_B. The candidate's magnitudes are: | date-obs (UTC) | mid-time | exposure | band | mag(AB) | | -------------------- | ----------- | --------- | ----- | ------------- | | 2025-10-13T17:44:04 | 6.85 min | 6*50 sec | VT_B | 15.38 ± 0.01 | | 2025-10-13T17:44:04 | 6.85 min | 6*50 sec | VT_R | 14.76 ± 0.01 | Magnitudes were not corrected for dust extinction. The VT color of the counterpart suggests it is not very high redshift or highly extinguished. 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. SVOM/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/42223. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40292] GRB 251013C: SVOM detection of a burst
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42222 SUBJECT: GRB 251013C: SVOM detection of a burst DATE: 25/10/13 18:17:34 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> N. A. Rakotondrainibe, C. Adami (LAM), D. Turpin, D. Götz (CEA/Irfu), H. Yang (IRAP) At 2025-10-13T17:39:42 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251013C (SVOM burst-id sb25101311) also detected by Fermi/GBM (Fermi GBM team GCN 42221). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 16 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 35.62 in the [8-120] keV energy band over a time window of 10.24 seconds starting at 2025-10-13T17:39:42. The SVOM/ECLAIRs light curve showed a single peak structure of a T90 duration of 17.1 (+6.9/-1.5) s. The localization of the best alert is R.A., Dec. 345.8809, -0.1698 degrees (J2000) with a 90% confidence level (C.L.) radius of 2.94 arcmin (including systematic error of 2 arcmin added in quadrature). This burst also triggered SVOM/GRM at 2025-10-13T17:39:43 on a timescale of 18 seconds with an SNR of 11. SVOM slewed to the burst. SVOM/MXT began observing the field at 2025-10-13T17:43:05 UTC, 203 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 345.8301, -0.2207 degrees: R.A. (J2000) = 23h03m19s Dec. (J2000) = -0d13m14s with a 90% C.L. radius of 69 arcseconds. This location is 4.31 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the data will be published in a future circular. 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. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Ny Avo Rakotondrainibe: ny-avo.rakotondrainibe(a)lam.fr Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/42222. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40291] GRB 251013C: Fermi GBM Final Real-time Localization
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42221 SUBJECT: GRB 251013C: Fermi GBM Final Real-time Localization DATE: 25/10/13 17:50:11 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 17:39:41 UT on 13 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251013C (trigger 782069986.941944 / 251013736). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 348.9, Dec = -6.3 (J2000 degrees, equivalent to J2000 23h 15m, -6d 17'), with a statistical uncertainty of 5.0 degrees. The angle from the Fermi LAT boresight is 65.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013736/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013736/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013736/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42221. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40290] LIGO/Virgo/KAGRA S251013x: Updated Sky localization and Source Classification
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42220 SUBJECT: LIGO/Virgo/KAGRA S251013x: Updated Sky localization and Source Classification DATE: 25/10/13 16:23:04 GMT FROM: Nihar.Gupte(a)aei.mpg.de The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S251013x (GCN Circular 42212). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN and SCiMMA notices, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S251013x For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 1361 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 3775 +/- 1200 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040 View this GCN Circular online at https://gcn.nasa.gov/circulars/42220. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40289] GRB 251013B: SVOM/GRM observation
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42219 SUBJECT: GRB 251013B: SVOM/GRM observation DATE: 25/10/13 15:20:56 GMT FROM: Yue Wang <m18509381757(a)163.com> SVOM/GRM team: Yue Wang, Chen-Wei Wang, Wen-Jun Tan, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Stéphane Schanne (CEA), Hui Yang (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered on-ground by GRB 251013B at 2025-10-13T08:24:36.250 (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #42215). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of mutli-peaks with a T90 of 55 +16/-7 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251013B.png In addition, the position of this burst, as determined by Fermi/GBM (RA=356.5, DEC=7.5, GCN #42215), is located at about 68.2 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-30 to T0+50 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.63 +0.10/-0.13 and the cutoff energy, parameterized as Epeak, is 324 +567/-129 keV. The event fluence (10-1000 keV) in this time interval is (1.08 +0.09/-0.11)E-05 erg/cm^2. The localization of GRB 251013B in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251013B_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: Yue Wang (IHEP) (yuewang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/42219. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40288] GRB 251013A: SVOM/GRM observation
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42218 SUBJECT: GRB 251013A: SVOM/GRM observation DATE: 25/10/13 15:18:58 GMT FROM: Yue Wang <m18509381757(a)163.com> SVOM/GRM team: Yue Wang, Chen-Wei Wang, Wen-Jun Tan, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Stéphane Schanne (CEA), Hui Yang (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered both in-flight by GRB 251013A (SVOM trigger reference: sb25101308) at 2025-10-13T08:04:05.800 (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #42213). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 3.5 +0.9/-0.6 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251013A.png In addition, the position of this burst, as determined by Fermi/GBM (RA=19.9, DEC=-1.6, GCN #42213), is located at about 57 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. Marginal signal seen by ECLAIRs through the shields With this localization, the time-averaged spectrum from T0-2 to T0+4 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.68 +0.13/-0.13 and the cutoff energy, parameterized as Epeak, is 142 +15/-12 keV. The event fluence (10-1000 keV) in this time interval is (2.96 +0.19/-0.17)E-06 erg/cm^2. The localization of GRB 251013A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251013A_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: Yue Wang (IHEP) (yuewang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/42218. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40287] GRB 251003A: Mondy optical upper limit
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42217 SUBJECT: GRB 251003A: Mondy optical upper limit DATE: 25/10/13 14:51:03 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), N. Pankov (HSE, IKI), E. Klunko (ISTP), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of GRB 251003A, detected by Fermi (Fermi team, GCNC 42069) and Swift (Beardmore et al., GCNC 42070), in the R-filter with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy). The observations began on 2025-10-06 13:10 UT, i.e. ~3.5 days since the trigger and consisted of 90 exposures by 80 s each. The optical source reported previously (Aceituno et al., GCN 42072; Méndez et al., GCN 42073; Strausbaugh et al., GCN 42074; Freeberg et al., GCN 42085; Sanchez-Ramirez et al., GCN 42086; Worssam et al., GCN 42094; Schneider et al., GCN 42095; Mo et al., GCN 42106; Konno et al., GCN 42126) is not detected in the stacked frame. The preliminary photometry is based on nearby USNO-B stars (R2 magnitudes) and is the following: Date UT start t-T0 Exp. Filter OT Err. UL (mid, days) (n*s) (3sigma) 2025-10-06 13:10:16 3.50116 90*80 R n/d n/d 22.0 View this GCN Circular online at https://gcn.nasa.gov/circulars/42217. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40286] MASTER OT J011025.98-583210.6 : SVOM/VT optical observation
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42216 SUBJECT: MASTER OT J011025.98-583210.6 : SVOM/VT optical observation DATE: 25/10/13 14:25:57 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, L. P. Xin, H. L. Li, Z. H. Yao, Y. L. Qiu, C. Wu, 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/VT performed a Target of Opportunity observation of MASTER OT J011025.98-583210.6 (Kechin et al., GCN 42211). SVOM/VT began observing the field at 2025-10-13T04:48:11 UTC in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X-band data, at the position of the optical transient (Kechin et al., GCN 42211) we don't detect any uncatalogued source, compared to the Legacy survey. But we noticed that there is a catalogued red source with an angular distance of 1.0 seconds from the source reported (Kechin et al., GCN 42211). The position is R.A.=01:10:26.11, DEC. = -58:32:10.49, J2000. The brightness was 20.31+/-0.07 in VT_R band, but VT_B>23 mag. The analysis showed that this source was stable during our 3.7 hours observation. Our photometry was not corrected for Galactic extinction. Given the source with red color at the position which is very near the MASTER OT J011025.98-583210.6, it is possible associated. A stellar flare from this late type star is possible. 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/42216. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40285] GRB 251013B: Fermi GBM Final Real-time Localization
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42215 SUBJECT: GRB 251013B: Fermi GBM Final Real-time Localization DATE: 25/10/13 08:33:39 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 08:24:27 UT on 13 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251013B (trigger 782036672.403254 / 251013350). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 356.5, Dec = 7.5 (J2000 degrees, equivalent to J2000 23h 45m, 7d 30'), with a statistical uncertainty of 5.7 degrees. The angle from the Fermi LAT boresight is 87.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013350/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013350/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013350/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42215. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40284] Fermi GRB 251013A: Global MASTER-Net observations report
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42214 SUBJECT: Fermi GRB 251013A: Global MASTER-Net observations report DATE: 25/10/13 08:30:31 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 251013A ( Fermi GBM team, GCN 42213) errorbox 544 sec after notice time and 582 sec after trigger time at 2025-10-13 08:13:47 UT, with upper limit up to 19.4 mag. The observations began at zenith distance = 61 deg. The sun altitude is -22.2 deg. The galactic latitude b = -63 deg., longitude l = 140 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3013630 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 642 | 2025-10-13 08:13:47 | MASTER-OAFA | (01h 20m 06.37s , -01d 28m 39.3s) | C | 120 | 19.1 | 778 | 2025-10-13 08:15:53 | MASTER-OAFA | (01h 20m 06.37s , -01d 28m 38.7s) | C | 140 | 19.3 | 940 | 2025-10-13 08:18:19 | MASTER-OAFA | (01h 20m 06.39s , -01d 28m 38.6s) | C | 170 | 19.4 | 1061 | 2025-10-13 08:21:15 | MASTER-OAFA | (01h 20m 06.42s , -01d 28m 38.7s) | C | 60 | 19.0 | 1126 | 2025-10-13 08:22:21 | MASTER-OAFA | (01h 20m 06.43s , -01d 28m 38.9s) | C | 60 | 18.9 | 1191 | 2025-10-13 08:23:26 | MASTER-OAFA | (01h 20m 06.45s , -01d 28m 38.8s) | C | 60 | 18.9 | 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/42214. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40283] GRB 251013A: Fermi GBM Final Real-time Localization
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42213 SUBJECT: GRB 251013A: Fermi GBM Final Real-time Localization DATE: 25/10/13 08:14:36 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 08:04:05 UT on 13 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251013A (trigger 782035450.15137 / 251013336). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 19.9, Dec = -1.6 (J2000 degrees, equivalent to J2000 01h 19m, -1d 36'), with a statistical uncertainty of 2.6 degrees. The angle from the Fermi LAT boresight is 95.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013336/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013336/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251013336/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42213. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40282] LIGO/Virgo/KAGRA S251013x: Identification of a GW compact binary merger candidate
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42212 SUBJECT: LIGO/Virgo/KAGRA S251013x: Identification of a GW compact binary merger candidate DATE: 25/10/13 03:31:33 GMT FROM: Kento IMAI <kent0311p(a)g.ecc.u-tokyo.ac.jp> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S251013x during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-10-13 02:44:14.281 UTC (GPS time: 1444358672.281). The candidate was found by the Aframe [1], GstLAL [2], MBTA [3], and PyCBC Live [4] analysis pipelines. S251013x is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.5e-08 Hz, or about one in 2 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S251013x The classification of the GW signal, in order of descending probability, is BBH (99%), Terrestrial (1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass (HasNS) is <1%. [5] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [5] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. The source chirp mass falls with highest probability in the bin (22.0, 44.0) solar masses, assuming the candidate is astrophysical in origin. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [6], distributed via GCN and SCiMMA notices about 30 seconds after the candidate event time. * bayestar.multiorder.fits,2, an initial localization generated by BAYESTAR [6], distributed via GCN and SCiMMA notices about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 1589 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1946 +/- 505 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Marx et al. PRD 111, 042010 (2025) doi:10.1103/PhysRevD.111.042010 [2] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. PRD 109, 042008 (2024) doi:10.1103/PhysRevD.109.042008 [3] Alléné et al. CQG 42, 105009 (2025) doi:10.1088/1361-6382/add234 [4] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [5] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [6] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/42212. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40281] GRB 251011B inspection: MASTER orphan GRB detection
by GCN Circulars 13 Oct '25

13 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42211 SUBJECT: GRB 251011B inspection: MASTER orphan GRB detection DATE: 25/10/13 00:15:06 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> Ya.Kechin, V.Lipunov, P.Balanutsa, A.Kuznetsov, G.Antipov, I.Panchenko, K.Zhirkov, E.Gorbovskoy, N.Tiurina, A.Sankovich, Ya.Kechin, M.Shilova, A.Chasovnikov, V.Topolev, V.Senik, D.Vlasenko, Yu.Tselik (Lomonosov MSU), R.Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San Juan Uni.,Argentina); D.Buckley, (SAAO, South Africa) O.Gress, N.Budnev (ISU, Irkutsk), A. Sosnovskiy (CrAO RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias, Spain), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez,J.Martinez,A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysic Observatory, Mexico) The MASTER-OAFA robotic telescope of the MASTER Global Robotic Net [1,2,3,4] started Swift GRB 251011B (Ttrigger=2025-10-11 07:08:22UT; XRT RA,Dec(2000)=00h 52m 56.33s,-62d 02'00.2" GCN 42197, GCN 42201) alert observations at 2025-10-11 07:09:27 and observed it up to sunrise (Balanutsa et al. GCN 42203). Next night MASTER automatic planner continued Fermi error-box (GCN 32196) inspection as independent alert MASTER OT J011025.98-583210.6 discovery MASTER-OAFA auto-detection system of MASTER Global Robotic Net [1,2,3,4] during Fermi GRB 251011B (GCN42204, also detected by Swift (GCN42197) and observed by MASTER in alert mode (GCN 42203)) inspection discovered OT source at (RA, Dec) = 01h 10m 25.98s -58d 32m 10.6s on 2025-10-12.16208 UT with light curve, that is typical for gamma-ray bursts optical counterpart. The OT unfiltered magnitud m=17.8 (first image) at 2025-10-12 03:53:24UT (mlim=19.3 at single image). The OT is seen in 8 images with typical GRB counterpart decay. There is no minor planet at this place. We have reference image on 2025-09-16.19346 UT with unfiltered mlim=20.3m. So as the Ttrigger for GRB 251011B was 19h earlier our discovery time (2025-10-11 07:08:22.33UT) and Swift error-box center was at 00h 52m 56.33s -62d 02' 00.2" (Swift GCN 42197, GCN 42201) MASTER OT looks not connected with just GRB 251011B, but can be the orphan one [5]. Spectral observations and deep photometry are required. [1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L [2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271 [3] Lipunov et a. 2019, ARep, vol.63, 293 [4] Lipunov V., Kornilov V., Gorbovskoy E., Tiurina N., Kuznetsov A. 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics,Lomonosov MSU PRESS, 591pp. http://www.pereplet.ru/lipunov/625.html#625 [5] Lipunov et al. 2022, MNRAS, 516, 4980 https://ui.adsabs.harvard.edu/abs/2022MNRAS.516.4980L/abstract View this GCN Circular online at https://gcn.nasa.gov/circulars/42211. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40280] GRB 251011A: Insight-HXMT detection
by GCN Circulars 12 Oct '25

12 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42210 SUBJECT: GRB 251011A: Insight-HXMT detection DATE: 25/10/12 16:37:23 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Xing-Hao Luo, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng report on behalf of the Insight-HXMT team: At 2025-10-11T03:41:40.000 (T0), Insight-HXMT/HE detected the burst GRB 251011A, which is also detected by Fermi/GBM (Fermi GBM team, GCN#42195) and AstroSat (M. Tembhurnikar et al., GCN#42199). The Insight-HXMT/HE light curve mainly consists of a single pulse with a T90 of 3.6 +1.6/-1.4 s. The 1s peak rate, measured from T0, is 788 cnts/sec. The total counts from this burst is 1444 counts. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251011A.png All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org. View this GCN Circular online at https://gcn.nasa.gov/circulars/42210. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40279] GRB 251011B: Swift/UVOT Upper Limits
by GCN Circulars 12 Oct '25

12 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42209 SUBJECT: GRB 251011B: Swift/UVOT Upper Limits DATE: 25/10/12 15:56:51 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M. H. Siegel (PSU) and A. D'Ai (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251011B 107 s after the BAT trigger (D'Ai et al., GCN Circ. 42197). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 42201) 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 first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 107 257 147 >20.9 white 107 257 147 >20.9 u 320 463 141 >20.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.017 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42209. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40278] Fermi GRB 251011A: Global MASTER-Net observations report
by GCN Circulars 12 Oct '25

12 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42208 SUBJECT: Fermi GRB 251011A: Global MASTER-Net observations report DATE: 25/10/12 15:31:51 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-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 251011A ( Fermi GBM team, GCN 42195) errorbox 1 days 37513 sec after notice time and 1 days 37548 sec after trigger time at 2025-10-12 14:07:28 UT, with upper limit up to 19.0 mag. The observations began at zenith distance = 21 deg. The sun altitude is -34.7 deg. The galactic latitude b = -19 deg., longitude l = 116 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3012037 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 123979 | 2025-10-12 14:07:28 | MASTER-Tunka | (00h 19m 58.96s , +42d 27m 50.2s) | C | 60 | 19.0 | 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/42208. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40277] GRB 251012A: Fermi GBM Final Real-time Localization
by GCN Circulars 12 Oct '25

12 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42207 SUBJECT: GRB 251012A: Fermi GBM Final Real-time Localization DATE: 25/10/12 14:56:50 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 SHORT GRB At 14:46:27 UT on 12 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251012A (trigger 781973192.204998 / 251012616). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 291.6, Dec = 7.5 (J2000 degrees, equivalent to J2000 19h 26m, 7d 30'), with a statistical uncertainty of 9.9 degrees. The angle from the Fermi LAT boresight is 59.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251012616/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251012616/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251012616/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42207. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40276] GRB 251011B: SVOM/GRM observation
by GCN Circulars 12 Oct '25

12 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42206 SUBJECT: GRB 251011B: SVOM/GRM observation DATE: 25/10/12 08:26:34 GMT FROM: xueyuan zao <zaoxueyuan(a)gmail.com> SVOM/GRM team: Xue-Yuan Zao, Zheng-Hang Yu, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Sebastien Guillot (IRAP), Stéphane Schanne (CEA), Nicolas Dagoneau Report on behalf of the SVOM team: SVOM/GRM detected the burst GRB 251011B at 2025-10-11T07:08:22.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #42196) and Swift/BAT (A. D'Ai et al., GCN #42197). With the event-by-event data downloaded through the X-band ground station, we conducted the standard analysis pipeline of GRB 251011B. The GRM light curve shows that this burst consists of a single pulse with a T90 of 48 +9/-10 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251011B.png In addition, the position of this burst, as determined by Fermi/GBM (RA= 5.3, DEC= -56.1, GCN#42196), is located at about 85.17 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-15 to T0+30 s is best fitted by a power law function. The power law index is 2.22 +0.23/-0.19. The event fluence (10-1000 keV) in this time interval is (3.56 +0.56/-0.82)E-06 erg/cm^2. 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: Xue-Yuan Zao (IHEP) (zaoxy(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/42206. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40275] GRB 251011B: Swift-XRT refined Analysis
by GCN Circulars 12 Oct '25

12 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42205 SUBJECT: GRB 251011B: Swift-XRT refined Analysis DATE: 25/10/12 07:29:18 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB), S. Lanava (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M. Ferro (INAF-OAB) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 5.1 ks of XRT data for GRB 251011B, from 85 s to 61.7 ks after the trigger. The data comprise 112 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The light curve can be modelled with an initial power-law decay with an index of alpha=3.12 (+/-0.08), followed by a break at T+579 s to an alpha of 0.57 (+0.07, -0.20). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.15 (+/-0.12). The best-fitting absorption column is 1.8 (+0.4, -0.3) x 10^21 cm^-2, in excess of the Galactic value of 1.7 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.1 x 10^-11 (4.5 x 10^-11) erg cm^-2 count^-1. A summary of the WT-mode spectrum is thus: Total column: 1.8 (+0.4, -0.3) x 10^21 cm^-2 Galactic foreground: 1.7 x 10^20 cm^-2 Excess significance: 8.4 sigma Photon index: 2.15 (+/-0.12) If the light curve continues to decay with a power-law decay index of 0.57, the count rate at T+24 hours will be 0.013 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.0 x 10^-13 (5.7 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01403191. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42205. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40274] GRB 251011B: Fermi GBM Observation
by GCN Circulars 12 Oct '25

12 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42204 SUBJECT: GRB 251011B: Fermi GBM Observation DATE: 25/10/12 00:26:55 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA), C. Meegan (UAH), U. Pathak (IIT Bombay) and L. Scotton (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 07:08:21.91 UT on 11 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251011B (trigger 781859306/251011297). which was also detected by Swift BAT (A. D'Ai et al. 2025, GCN 42197), and Swift XRT (P.A. Evans et al. 2025, GCN 42201). The Fermi GBM on-ground location is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 81.8 degrees. The GBM light curve consists of a single pulse with a duration (T90) of about 35 s (50-300 keV). The time-averaged spectrum from T0-8.0 to T0+26.5 s is best fit by a Band function with Epeak = 36 +/- 5 keV, alpha = 0.4 +/- 0.7, and beta = -2.2 +/- 0.1. The event fluence (10-1000 keV) in this time interval is (3.3 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.58 s in the 10-1000 keV band is 3 +/- 0.2 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/42204. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40273] GRB 251011B : MASTER optical observations
by GCN Circulars 11 Oct '25

11 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42203 SUBJECT: GRB 251011B : MASTER optical observations DATE: 25/10/11 23:11:20 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> P.Balanutsa, V.Lipunov, A.Kuznetsov, G.Antipov, I.Panchenko, K.Zhirkov, N.Tiurina, A.Sankovich, Ya.Kechin, M.Shilova, A.Chasovnikov, V.Topolev, V.Senik, D.Vlasenko, Yu.Tselik, E.Gorbovskoy(Lomonosov MSU), R.Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San Juan Uni.,Argentina); D.Buckley, (SAAO, South Africa) O.Gress, N.Budnev (ISU, Irkutsk), A. Sosnovskiy (CrAO RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias, Spain), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez,J.Martinez,A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysic Observatory, Mexico) The MASTER-OAFA robotic telescope of the MASTER Global Robotic Net [1,2,3,4] started GRB 251011B (Fermi GCN 42196, Swift: D'Ai et al. GCN 42197, XRT Evans et al. GCN 42201, Ttrigger=2025-10-11 07:08:22UT XRT RA,Dec(2000)=00h 52m 56.33s,-62d 02' 00.2") at 2025-10-11 07:09:27 with 10s expositions at 48 deg.altitude There is no optical counterpart on a single images Observations and reduction will be continued. Tstart(+exp), UT RADec(2000) of MASTERsquarecent. Exp,s mlim 2025-10-11 07:09:07 00h 53m 53.80s -61d 58m 00.8s 10 18.0 2025-10-11 07:09:23 00h 53m 53.92s -61d 58m 00.0s 10 18.0 2025-10-11 07:09:39 00h 53m 53.86s -61d 58m 00.6s 20 18.6 2025-10-11 07:10:05 00h 53m 53.91s -61d 58m 00.5s 20 18.9 2025-10-11 07:10:31 00h 53m 54.05s -61d 57m 59.3s 30 18.0 2025-10-11 07:11:06 00h 53m 54.18s -61d 57m 59.2s 30 18.0 2025-10-11 07:11:43 00h 53m 54.30s -61d 57m 59.1s 40 18.3 2025-10-11 07:12:29 00h 53m 54.50s -61d 57m 58.5s 50 18.8 2025-10-11 07:13:25 00h 53m 54.74s -61d 57m 58.3s 60 19.2 2025-10-11 07:14:32 00h 53m 55.02s -61d 57m 57.6s 70 19.6 2025-10-11 07:15:47 00h 53m 55.39s -61d 57m 57.1s 90 19.6 2025-10-11 07:17:23 00h 53m 55.79s -61d 57m 56.7s 110 19.6 2025-10-11 07:19:19 00h 53m 56.33s -61d 57m 55.8s 130 19.6 2025-10-11 07:21:35 00h 53m 57.00s -61d 57m 55.1s 160 19.6 up to 2025-10-11 09:17:08. [1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L [2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271 [3] Lipunov et a. 2019, ARep, vol.63, 293 [4] Lipunov V., Kornilov V., Gorbovskoy E., Tiurina N., Kuznetsov A. 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http://www.pereplet.ru/lipunov/625.html#625 View this GCN Circular online at https://gcn.nasa.gov/circulars/42203. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40272] GRB 251011C: Fermi GBM Final Real-time Localization
by GCN Circulars 11 Oct '25

11 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42202 SUBJECT: GRB 251011C: Fermi GBM Final Real-time Localization DATE: 25/10/11 22:22:00 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 22:11:20 UT on 11 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251011C (trigger 781913485.841388 / 251011925). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 164.7, Dec = -2.9 (J2000 degrees, equivalent to J2000 10h 58m, -2d 53'), with a statistical uncertainty of 4.6 degrees. The angle from the Fermi LAT boresight is 48.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011925/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011925/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011925/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42202. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40271] GRB 251011B: Enhanced Swift-XRT position
by GCN Circulars 11 Oct '25

11 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42201 SUBJECT: GRB 251011B: Enhanced Swift-XRT position DATE: 25/10/11 14:07:46 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 243 s of XRT Photon Counting mode data and 1 UVOT images for GRB 251011B, 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 = 13.23469, -62.03340 which is equivalent to: RA (J2000): 00h 52m 56.33s Dec (J2000): -62d 02' 00.2" with an uncertainty of 2.4 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at https://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/42201. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40270] GRB 251010A: AstroSat CZTI detection
by GCN Circulars 11 Oct '25

11 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42200 SUBJECT: GRB 251010A: AstroSat CZTI detection DATE: 25/10/11 12:09:34 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> A. Goyal (IITB), A. Arya (IITB), U. Pathak (IITB), S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of GRB 251010A which was also detected by Fermi GBM (GCN Circ. 42192). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed a broad peak of emission with the strongest peak at 2025-10-10 17:44:27.50 UTC. The measured peak count rate associated with the burst is 82 (+38, -8) counts/s above the background in the combined data of all quadrants, with a total of 628 (+155, -170) counts. The local mean background count rate was 292 (+3, -4) counts/s. Using cumulative rates, we measure a T90 of 9.5 (+3.1, -2.3) s. The source was also faintly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/42200. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40269] GRB 251011A: AstroSat CZTI detection
by GCN Circulars 11 Oct '25

11 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42199 SUBJECT: GRB 251011A: AstroSat CZTI detection DATE: 25/10/11 09:26:10 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), Harsha K. H. (IUCAA), A. Arya (IITB), A. Goyal (IITB), U. Pathak (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 251011A which was also detected by Fermi GBM (GCN Circ. 42195). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-10-11 03:41:37.50 UTC. The measured peak count rate associated with the burst is 200 (+32, -29) counts/s above the background in the combined data three quadrants out of four, with a total of 743 (+117, -127) counts. The local mean background count rate was 208 (+3, -3) counts/s. Using cumulative rates, we measure a T90 of 6.5 (+2.1, -1.9) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed a peak of emission at 2025-10-11 03:41:37 UTC. The measured peak count rate associated with the burst is 356 (+68, -62) counts/s above the background in the combined data of all quadrants, with a total of 952 (+242, -256) counts. The local mean background count rate was 1335 (+7, -8) counts/s. We measure a T90 of 5.9 (+2.1, -2.9) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/42199. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40268] GRB 251009B: SVOM/GRM observation of short GRB
by GCN Circulars 11 Oct '25

11 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42198 SUBJECT: GRB 251009B: SVOM/GRM observation of short GRB DATE: 25/10/11 08:12:07 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Stéphane Schanne (CEA), Jean-Luc Atteia (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered on-ground by a short burst GRB 251009B at 2025-10-09T01:51:15.350 UTC (T0), which is also detected by Insight-HXMT (Wang et al., GCN#42187), Glowbug (C.C. Cheung et al., GCN#42188). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a double spikes with a T90 of 1.2 +0.75/-0.45 s in the 15-5000 keV band, the signal mainly appears above 100 keV. No significant signal is detected by ECLAIRs, suggesting the burst is outside the ECLAIRs FoV. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251009B.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 point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/42198. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40267] GRB 251011B: Swift detection of a burst
by GCN Circulars 11 Oct '25

11 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42197 SUBJECT: GRB 251011B: Swift detection of a burst DATE: 25/10/11 07:29:21 GMT FROM: Antonino D'Ai' at INAF <antonino.dai(a)inaf.it> A. D'Ai (INAF-IASFPA), E. Ambrosi (INAF-IASFPA), V. D'Elia (SSDC & INAF-OAR), R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL), A. Melandri (INAF-OAR), K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 07:08:22.33 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 251011B (trigger=1403191). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 13.287, -62.032 which is RA(J2000) = 00h 53m 09s Dec(J2000) = -62d 01' 55" 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 150 seconds. The peak count rate was ~3000 counts/sec (15-350 keV) at ~0 sec after the trigger. The XRT began observing the field at 07:09:58.8 UT, 96.5 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 13.23523, -62.03269 which is equivalent to: RA(J2000) = 00h 52m 56.46s Dec(J2000) = -62d 01' 57.7" with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 87 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.68 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.5 (+3.47/-2.92) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 1.95e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT data are unavailable at this time. Burst Advocate for this burst is A. D'Ai (antonino.dai AT inaf.it). 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/42197. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40266] GRB 251011B: Fermi GBM Final Real-time Localization
by GCN Circulars 11 Oct '25

11 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42196 SUBJECT: GRB 251011B: Fermi GBM Final Real-time Localization DATE: 25/10/11 07:19:01 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 07:08:21 UT on 11 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251011B (trigger 781859306.91454 / 251011297). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 5.3, Dec = -56.1 (J2000 degrees, equivalent to J2000 00h 21m, -56d 06'), with a statistical uncertainty of 5.3 degrees. The angle from the Fermi LAT boresight is 78.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011297/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011297/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011297/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42196. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40265] GRB 251011A: Fermi GBM Final Real-time Localization
by GCN Circulars 11 Oct '25

11 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42195 SUBJECT: GRB 251011A: Fermi GBM Final Real-time Localization DATE: 25/10/11 03:52:08 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 03:41:40 UT on 11 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251011A (trigger 781846905.087994 / 251011154). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 2.6, Dec = 43.3 (J2000 degrees, equivalent to J2000 00h 10m, 43d 17'), with a statistical uncertainty of 2.4 degrees. The angle from the Fermi LAT boresight is 63.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011154/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011154/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011154/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42195. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40264] Fermi Gamma-ray Burst Monitor trigger 781824269/251010892 is not a GRB
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42194 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 781824269/251010892 is not a GRB DATE: 25/10/10 23:06:32 GMT FROM: rhamburg(a)usra.edu R. Hamburg (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 781824269/251010892 at 21:24:24.75 UT on 10 October 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to local particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/42194. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40263] GRB 251007B: Swift/UVOT Upper Limits
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42193 SUBJECT: GRB 251007B: Swift/UVOT Upper Limits DATE: 25/10/10 18:00:23 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> GRB 251007B: Swift/UVOT Upper Limits M. H. Siegel (PSU) and A. Melandri (INAF-OAR) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251007B 152 s after the BAT trigger (Melandri et al., GCN Circ. 42147). No optical afterglow consistent with the XRT position (Osborne et al., GCN Circ 42159) 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 first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 152 302 147 >19.8 u_FC 311 561 246 >19.1 white 152 5220 220 >19.9 v 641 4360 220 >19.2 b 567 5181 236 >20.3 u 311 4975 462 >19.5 w1 691 4770 216 >19.8 m2 665 4565 216 >19.5 w2 616 810 39 >18.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.786 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42193. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40262] GRB 251010A: Fermi GBM Final Real-time Localization
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42192 SUBJECT: GRB 251010A: Fermi GBM Final Real-time Localization DATE: 25/10/10 17:55:05 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 17:44:25 UT on 10 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251010A (trigger 781811070.725816 / 251010739). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 214.0, Dec = 56.6 (J2000 degrees, equivalent to J2000 14h 16m, 56d 36'), with a statistical uncertainty of 4.5 degrees. The angle from the Fermi LAT boresight is 103.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251010739/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251010739/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251010739/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42192. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40261] GRB251007A: Swift/UVOT Detection
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42191 SUBJECT: GRB251007A: Swift/UVOT Detection DATE: 25/10/10 17:40:49 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M. H. Siegel (PSU) and E/ Ambrosi (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251007A 79 s after the BAT trigger (Ambrosi et al., GCN Circ. 42146). A fading source consistent with the XRT position (Beardmore et al., GCN Circ. 42161) and the previously reported optical source (Wu et al., GCN Circ. 42154; Malesani et al., GCN Circ. 42158, Hu et al. GCN Circ 42174) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 08:32:42.39 = 128.17664 (deg.) Dec (J2000) = +21:48:46.3 = 21.81285 (deg.) with an estimated uncertainty of 0.45 arc sec. (radius, 90% confidence). Preliminary detections 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 white 80 229 146 18.42+/-0.08 white 17739 18156 406 >20.41 v 11939 39105 2335 >20.09 b 16827 17734 885 >20.39 u 291 418 124 19.11+/-0.36 uvm2 27913 39155 906 >20.29 uvw2 23059 34819 1506 >20.58 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.039 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42191. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40260] GRB 251009A: GECAM-B detection of a short burst
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42190 SUBJECT: GRB 251009A: GECAM-B detection of a short burst DATE: 25/10/10 16:22:21 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by the short burst GRB 251009A at 2025-10-09T15:58:56.300 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN#42179), SVOM/GRM (Wang et al., GCN#42185) and Insight-HXMT (Wang et al., GCN#42189). According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 0.14 +0.08/-0.08 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251009A.png Using the automatic on-ground localization pipeline, GECAM-B localized this burst to the following position (J2000): Ra: 103.2 deg Dec: 34.2 deg Err: 21.4 deg (1-sigma, statistical only) Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/42190. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40259] GRB 251009A: Insight-HXMT detection of a short burst
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42189 SUBJECT: GRB 251009A: Insight-HXMT detection of a short burst DATE: 25/10/10 16:17:00 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng report on behalf of the Insight-HXMT team: At 2025-10-09T15:58:56.350 (T0), Insight-HXMT/HE detected the burst GRB 251009A, which is also detected by Fermi/GBM (Fermi GBM team, GCN#42179) and SVOM/GRM (Wang et al., GCN#42185). The Insight-HXMT/HE light curve mainly consists of a single pulse with a T90 of 0.65 +0.31/-0.28 s. The total counts from this burst is 998 counts. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251009A.png All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org. View this GCN Circular online at https://gcn.nasa.gov/circulars/42189. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40258] GRB 251009B (short): Glowbug gamma-ray detection
by GCN Circulars 10 Oct '25

10 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42188 SUBJECT: GRB 251009B (short): Glowbug gamma-ray detection DATE: 25/10/10 16:14:04 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, 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 251009B, which was also detected by Insight-HXMT (GCN 41287). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-09 01:51:14.176 with a duration of 1.0 s and a total significance of about 13.1 sigma. The light curve comprises two peaks at ~T0+0.2s and ~T0+0.9s. The best-fit localization is RA, Decl. (J2000, deg) = 155.1, 24.1 with a radius of 25.3 deg (95% confidence), with a highly uncertain systematic uncertainty. 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/42188. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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