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

[vsnet-grb-info 41193] GRB 251214B: Swift-XRT refined Analysis
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43112 SUBJECT: GRB 251214B: Swift-XRT refined Analysis DATE: 25/12/15 09:28:13 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), S. Campana (INAF-OAB), S. Lanava (PSU), S. Dichiara (PSU) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 5.9 ks of XRT data for GRB 251214B, from 46 s to 28.7 ks after the trigger. The data comprise 8 s in Windowed Timing (WT) mode (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=0.72 (+0.14, -0.17), followed by a break at T+418 s to an alpha of 1.33 (+0.10, -0.08). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.82 (+0.19, -0.18). The best-fitting absorption column is 1.6 (+0.7, -0.6) x 10^21 cm^-2, in excess of the Galactic value of 4.0 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 3.9 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.6 (+0.7, -0.6) x 10^21 cm^-2 Galactic foreground: 4.0 x 10^20 cm^-2 Excess significance: 3.5 sigma Photon index: 1.82 (+0.19, -0.18) If the light curve continues to decay with a power-law decay index of 1.33, the count rate at T+24 hours will be 1.6 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.3 x 10^-14 (7.8 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01423875. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43112. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41192] GRB 251213A: SVOM/GRM observation
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43111 SUBJECT: GRB 251213A: SVOM/GRM observation DATE: 25/12/15 09:24:16 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Wen-Jun Tan, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Ulysse Jacob (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a burst GRB 251213A (SVOM trigger reference: sb25121302) at 2025-12-13T12:30:05.000 UTC (T0), which is also detected by GRID, GECAM-B (Wang et al., GCN#43106) and AstroSat (Harsha K. H. et al., GCN#43108). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a T90 of 36.5 +1.0/-1.0 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251213A.png In addition, the position of this burst, as determined by GECAM-B (RA= 296.5, DEC= -11.9, ERR=5.6), is located at about 102 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-5 to T0+45 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.95 +0.10/-0.09 and the cutoff energy, parameterized as Epeak, is 453 +63/-50 keV. The event fluence (10-1000 keV) in this time interval is (5.58 +0.18/-0.19)E-05 erg/cm^2. The 1s peak spectrum, measured from T0+5.0 to T0+6.0 s, is also best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.09 +0.14/-0.12 and the cutoff energy, parameterized as Epeak, is 800 +286/-182 keV. The flux (10-1000 keV) in this time interval is (3.31 +0.13/-0.14)E-06 erg/cm^2/s. The localization of GRB 251213A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251213A_amati.png And the localization in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251213A_yonetoku.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/43111. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41191] EP251214a: KAIT optical upper limit
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43110 SUBJECT: EP251214a: KAIT optical upper limit DATE: 25/12/15 07:28:01 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of EP251214a (Yin et al., GCN 43087; 43102) starting at 08:58, Dec 14 UT, about 6.52 hours after the burst. A set of 129x60s clear (roughly R) filter images were obtained. In our coadd image, we did not detect any new source within the EP-WXT error circle (Yin et al., GCN 43087) down to a limiting mag of 21.6 mag (Vega) at a mid-time of 8.88 hours after the burst. Our result is consistent with the upper limit reported by other groups (Basa et al., GCN 43092; Lipunov et al., GCN 43099). View this GCN Circular online at https://gcn.nasa.gov/circulars/43110. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41190] GRB 251214D: AstroSat CZTI detection of a long burst
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43109 SUBJECT: GRB 251214D: AstroSat CZTI detection of a long burst DATE: 25/12/15 06:49:33 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> A. Arya (IITB), A. Goyal (IITB), M. Tembhurnikar (IUCAA), S. Salunke (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 a long-duration GRB 251214D. The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-12-14 21:24:21.50 UTC. The measured peak count rate associated with the burst is 71 (+34, -11) counts/s above the background in the combined data of all quadrants, with a total of 576 (+192, -210) counts. The local mean background count rate was 264 (+3, -3) counts/s. Using cumulative rates, we measure a T90 of 16 (+3, -7) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-12-14 21:24:21.75 UTC. The measured peak count rate associated with the burst is 231 (+68, -36) counts/s above the background in the combined data of all quadrants, with a total of 1844 (+413, -469) counts. The local mean background count rate was 1211 (+7, -7) counts/s. We measure a T90 of 20 (+2, -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/43109. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41189] GRB 251213A: AstroSat CZTI detection
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43108 SUBJECT: GRB 251213A: AstroSat CZTI detection DATE: 25/12/15 06:37:41 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> Harsha K. H. (IUCAA), S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), A. Arya (IITB), A. Goyal (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 251213A which was also detected by GECAM-B (Wang et. al., GCN Circ. 43106). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-12-13 12:30:11.00 UTC. The measured peak count rate associated with the burst is 48 (+18, -9) counts/s above the background in the combined data of three quadrants (out of four), with a total of 617 (+188, -211) counts. The local mean background count rate was 187 (+1, -2) counts/s. Using cumulative rates, we measure a T90 of 39 (+1, -14) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-12-13 12:30:12.01 UTC. The measured peak count rate associated with the burst is 265 (+71, -15) counts/s above the background in the combined data of all quadrants, with a total of 3624 (+653, -519) counts. The local mean background count rate was 1137 (+4, -6) counts/s. We measure a T90 of 36 (+1, -2) 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/43108. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41188] GRB 251214A: AstroSat CZTI detection
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43107 SUBJECT: GRB 251214A: AstroSat CZTI detection DATE: 25/12/15 06:13:10 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> A. Goyal (IITB), A. Arya (IITB), M. Tembhurnikar (IUCAA), S. Salunke (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 251214A which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 43086). We detect only the brighter shorter-duration part of the burst as seen in the GBM lightcurve because the source location was at an angle of 110 deg from the pointing axis of AstroSat CZTI. The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-12-14 00:11:15.25 UTC. The measured peak count rate associated with the burst is 274 (+153, -45) counts/s above the background in the combined data of all quadrants, with a total of 134 (+124, -33) counts. The local mean background count rate was 269 (+5, -23) counts/s. Using cumulative rates, we measure a T90 of 1.4 (+0.2, -1.0) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-12-14 00:11:14.91 UTC. The measured peak count rate associated with the burst is 347 (+66, -71) counts/s above the background in the combined data of all quadrants, with a total of 418 (+226, -230) counts. The local mean background count rate was 1283 (+6, -7) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 for our detection. 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/43107. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41187] GRB 251213A: GECAM-B detection
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43106 SUBJECT: GRB 251213A: GECAM-B detection DATE: 25/12/15 06:05:28 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 in-flight by GRB 251213A, at 2025-12-13T12:30:05.050 UTC (denoted as T0), which is also detected by SVOM/GRM and GRID. According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a precursor followed by multi-pulses with a duration (T90) of 34.6 +1.0/-1.0 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251213A.png GECAM-B localized this burst to the following position (J2000): Ra: 296.5 deg Dec: -11.9 deg Err: 5.6 deg (1-sigma, statistical only) We note that the non-detection by Fermi/GBM suggests that the error box can be further constrained in the future. 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/43106. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41186] GRB 251214B: Swift/UVOT Detection
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43105 SUBJECT: GRB 251214B: Swift/UVOT Detection DATE: 25/12/15 05:01:50 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> N.P.M. Kuin (MSSL/UCL) and R. Eyles-Ferris (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251214B 64 s after the BAT trigger (Eyles-Ferris et al., GCN Circ. 43089). A source consistent with the XRT position Evans et al. GCN Circ. 43098) is detected in the initial UVOT exposures. There were early reports of the optical afterglow from Zhe Kang et al. (GCN Circ. 43093) and S.Y. Fu et al. (GCN Circ. 43097). The preliminary UVOT position is: RA (J2000) = 22:00:50.53 = 330.21053 (deg.) Dec (J2000) = -09:09:46.4 = -9.16290 (deg.) with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 64 214 147 17.21 +/- 0.03 v 606 800 39 17.09 +/- 0.17 b 532 724 39 18.08 +/- 0.17 u 277 527 246 17.76 +/- 0.08 w1 655 1472 97 >18.9 m2 630 1447 97 >20.3 w2 582 5213 136 >19.6 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/43105. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41185] GRB 251215A: Fermi GBM Final Real-time Localization
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43104 SUBJECT: GRB 251215A: Fermi GBM Final Real-time Localization DATE: 25/12/15 04:31:53 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 04:21:21 UT on 15 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251215A (trigger 787465286.567966 / 251215181). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 112.8, Dec = -43.7 (J2000 degrees, equivalent to J2000 07h 31m, -43d 42'), with a statistical uncertainty of 7.6 degrees. The angle from the Fermi LAT boresight is 31.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251215181/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251215181/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251215181/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43104. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41184] GRB 251214B: COLIBRÍ observations of the afterglow
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43103 SUBJECT: GRB 251214B: COLIBRÍ observations of the afterglow DATE: 25/12/15 04:27:56 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Benjamin Schneider (LAM), Stéphane Basa (UAR Pytheas), Camila Angulo (UNAM), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), 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), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Nikos Mandarakas (LAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the Fermi/Swift GRB 251214B (Fermi GBM Team, GCN Circ. 43088; Eyles-Ferris et al., GCN Circ. 43089) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-12-15 01:33 to 03:22 UTC (from 16.52 to 18.34 hours after the Swift/BAT trigger) and obtained 28, 28, 28, and 84 minutes of simultaneous exposure in the g, r, i, and z filters, respectively. The data were reduced, coadded, and analyzed with the ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In our stacked images, at the position of the afterglow (Eyles-Ferris et al., GCN Circ. 43089; Kang et al., GCN Circ. 43093; Gress et al., GCN Circ. 43095; Fu et al., GCN Circ. 43097; and Gupta et al., GCN Circ 43100) we detect the a source with preliminary magnitudes of: g = 22.97 +/- 0.21 r = 22.05 +/- 0.12 i = 21.52 +/- 0.12 z = 20.97 +/- 0.08 We note the presence of a bright galaxy coincident with the afterglow in Legacy Survey observations (Dey et al. 2019) with g = 23.70 +/- 0.11, r = 22.37 +/- 0.06, i = 21.62 +/- 0.06, z = 21.12 +/- 0.04, and a photometric redshift of z = 0.70 +/- 0.07. We suggest this might be the host galaxy. Its low redshift is consistent with the detection of the afterglow in g by Kang et al. (GCN Circ. 43093) and in our observations. Our observations include light from both the afterglow and this galaxy, and the afterglow is only clearly detected above the galaxy in g. The fading in g between the observations of Kang et al. (GCN Circ. 43093) and our observations implies a temporal power-law index of 1.08 or steeper. 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/43103. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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