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

[vsnet-grb-info 40404] Swift Trigger 1404295 is not a GRB
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42328 SUBJECT: Swift Trigger 1404295 is not a GRB DATE: 25/10/17 15:26:20 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> R. Gupta (NASA GSFC), N. J. Klingler (GSFC/UMBC/CRESSTII), D. M. Palmer (LANL), and T. Sbarrato (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: Using the data set from T-183 to T+963 sec from telemetry downlinks, we report further analysis of BAT trigger #1404295 (Klingler, et al., GCN Circ. 42290). This trigger is due to noise in the BAT image domain, with no significant emission detected in the mask-weighted light curve. No confirmed counterpart is found in the XRT or UVOT data within the BAT error circle, indicating that the trigger is not a real astrophysical event. View this GCN Circular online at https://gcn.nasa.gov/circulars/42328. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40403] GRB 251016A: AstroSat CZTI detection of a short burst
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42327 SUBJECT: GRB 251016A: AstroSat CZTI detection of a short burst DATE: 25/10/17 13:05:35 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> A. Goyal (IITB), A. Arya (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 a short-duration GRB 251016A which was also detected by SVOM/ECLAIRs (Basa et al., GCN Circ. 42308), Fermi GBM (Fermi GBM Team, GCN Circ. 42309), Glowbug (Woolf et al., GCN Circ. 42313) and CALET GBM (Kawakubo et al., GCN Circ. 42321). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-10-16 14:59:16.90 UTC. The measured peak count rate associated with the burst is 1142 (+782, -64) counts/s above the background in the combined data of all four quadrants, with a total of 140 (+39, -30) counts. The local mean background count rate was 264 (+14, -45) counts/s. Using cumulative rates, we measure a T90 of 0.31 (+0.04, -0.08) 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 2025-10-16 14:59:16.68 UTC. The measured peak count rate associated with the burst is 1099 (+76, -82) counts/s above the background in the combined data of all quadrants, with a total of 1056 (+117, -126) counts. The local mean background count rate was 1232 (+9, -10) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 from it. 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/42327. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40402] GRB 251017A: Enhanced Swift-XRT position
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42326 SUBJECT: GRB 251017A: Enhanced Swift-XRT position DATE: 25/10/17 12:54:56 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 1230 s of XRT Photon Counting mode data and 2 UVOT images for GRB 251017A, 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 = 335.40133, +7.04008 which is equivalent to: RA (J2000): 22h 21m 36.32s Dec (J2000): +07d 02' 24.3" with an uncertainty of 2.1 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/42326. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40401] GRB 251017A: COLIBRÍ Early Afterglow Detection
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42325 SUBJECT: GRB 251017A: COLIBRÍ Early Afterglow Detection DATE: 25/10/17 11:03:48 GMT FROM: Dalya Akl at American Uni. SHJ <dalyaakl.d(a)gmail.com> Sarah Antier (IJCLAB), Dalya Akl (NYUAD), Enrique Moreno Méndez (UNAM), Alan M. Watson (UNAM), Noémie Globus (UNAM), Ny Avo Rakotondrainibe (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), 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), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the Swift GRB 251017A (Page et al., GCN Circ. 42322) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-10-17 08:41 to 09:15 UTC (from 1 min to 35 min after the trigger) and obtained 35 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ pipeline and analysed 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 reported by Page et al., GCN Circ. 4232, at the SVOM/UVOT, with preliminary magnitudes of our first images: r = 19.90 +/- 0.17 z = 17.94 +/- 0.09 We note that the r-z color is ~2 mag. Concurrent observations were taken by BOOTES (I. Perez-Garcia et al., 42323). Further observations in g/r/i/z/y are planned. 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/42325. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40400] GRB 251016B: AstroSat CZTI detection
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42324 SUBJECT: GRB 251016B: AstroSat CZTI detection DATE: 25/10/17 10:34:55 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> Harsha K. H. (IUCAA), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), A. Arya (IITB), U. Pathak (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 bright,long GRB 251016B which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 42316). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-10-16 23:59:03.85 UTC. The measured peak count rate associated with the burst is 1394 (+217, -85) counts/s above the background in the combined data of three quadrants (out of four), with a total of 4295 (+210, -209) counts. The local mean background count rate was 214 (+6, -8) counts/s. Using cumulative rates, we measure a T90 of 5.4 (+0.8, -0.5) s. In the preliminary analysis, we find 498 Compton events associated with this event. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-10-16 23:59:02.60 UTC. The measured peak count rate associated with the burst is 1972 (+90, -100) counts/s above the background in the combined data of all quadrants, with a total of 6747 (+290, -334) counts. The local mean background count rate was 1255 (+6, -6) counts/s. We measure a T90 of 5.2 (+1.8, -0.7) 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/42324. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40399] GRB 251017A: BOOTES-5/JGT early optical afterglow detection
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42323 SUBJECT: GRB 251017A: BOOTES-5/JGT early optical afterglow detection DATE: 25/10/17 09:33:38 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es> I. Perez-Garcia, E. J. Fernandez-Garcia, G. Garcia-Segura, M. D. Caballero-Garcia, S.-Y. Wu, R. Sanchez-Ramirez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), M. Gritsevich (Univ. of Helsinki), C. Perez del Pulgar, A. Castellon (Univ. de Malaga), Y.-D. Hu (INAF-OAB, Brera), S. Jeong (ADD, Daejeon) and D. Hiriart and W. H. Lee (UNAM), on behalf of a larger collaboration, report: Following the detection of GRB 251017A by SWIFT/BAT trigger=1404904, the BOOTES-5/JG robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically responded to this event starting on 2025-10-17 08:41:17 UT (23 sec after detection). Series of 1 and 10 second images in clear filter were gathered and we detect an optical source consistent with the one reported by Gupta et al. (GCN 42322). Using GaiaDR3 Gmag as reference we report our photometry analysis: | UT mid exposure | mag | error | filter | exposure time (sec) | | ------------------- | ----- | ----- | ------ | ------------------- | | 2025-10-17 08:41:17 | >16.5 | --- | clear | 1 | | 2025-10-17 08:43:41 | 16.92 | 0.2 | clear | 1 | | 2025-10-17 08:47:57 | 17.51 | 0.08 | clear | 10 | | 2025-10-17 08:53:54 | 17.86 | 0.12 | clear | 10 | Further analysis of the additional images is ongoing. We thank the staff at Observatorio Astronomico Nacional in San Pedro Martir for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/42323. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40398] GRB 251017A: Swift detection of a burst with an optical counterpart
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42322 SUBJECT: GRB 251017A: Swift detection of a burst with an optical counterpart DATE: 25/10/17 08:54:42 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> R. Gupta (NASA GSFC), R. Brivio (INAF-OAB), S. Dichiara (PSU), R. A. J. Eyles-Ferris (U Leicester), A. Mei (INAF-OAB), K. L. Page (U Leicester), C. Salvaggio (INAF-OAB) and T. Sbarrato (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 08:40:44 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 251017A (trigger=1404904). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 335.386, +7.051 which is RA(J2000) = 22h 21m 33s Dec(J2000) = +07d 03' 02" 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 25 sec. The peak count rate was ~2136 counts/sec (15-350 keV), at ~6 sec after the trigger. The XRT began observing the field at 08:42:34.1 UT, 109.5 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 335.40109, 7.04043 which is equivalent to: RA(J2000) = 22h 21m 36.26s Dec(J2000) = +07d 02' 25.5" with an uncertainty of 4.0 arcseconds (radius, 90% containment). This location is 65 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. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (8.90 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 6.7 (+3.92/-3.27) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 2.03e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 120 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 22:21:36.24 = 335.40098 DEC(J2000) = +07:02:23.6 = 7.03990 with a 90%-confidence error radius of about 0.77 arc sec. This position is 4.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 20.42 with a 1-sigma error of about 0.21. No correction has been made for the expected extinction corresponding to E(B-V) of 0.108. Burst Advocate for this burst is R. Gupta (rahulbhu.c157 AT gmail.com) 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/42322. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40397] GRB 251016A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42321 SUBJECT: GRB 251016A: CALET Gamma-Ray Burst Monitor detection DATE: 25/10/17 07:26:43 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> Y. Kawakubo , A. Yoshida, T. Sakamoto, S. Sugita (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 short GRB 251016A (SVOM detection: Basa et al., GCN Circ. 42308; Fermi GBM Final Localization: Fermi GBM team, GCN Circ. 42309; Glowbug gamma-ray detection: Woolf et al., GCN Circ. 42313) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 14:59:19.37 UTC on 16 October 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1444661491/index.html) The burst signal was seen by all CGBM detectors. The burst light curve shows a short pulse that starts at T+0.32 sec, peaks at T+0.51 sec, and ends at T+0.69 sec. The T90 and T50 durations measured by the SGM data are 0.29 +/- 0.05 sec and 0.10+/- 0.03 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1444661491/ 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/42321. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40396] GRB 251016B: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42320 SUBJECT: GRB 251016B: CALET Gamma-Ray Burst Monitor detection DATE: 25/10/17 07:01:32 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> K. Yamaoka (Nagoya U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), 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 long GRB 251016B (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN Circ. 42316) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 23:58:57.45 UTC on 16 October 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1444693868/index.html) The burst signal was seen by all CGBM detectors. The burst light curve shows a single pulse that starts at T+3.1 sec, peaks at T+5.6 sec, and ends at T+12.6 sec. The T90 and T50 durations measured by the SGM data are 5.9 +/- 0.5 sec and 2.0 +/- 0.1 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1444693868/ 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/42320. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40395] GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42319 SUBJECT: GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart DATE: 25/10/17 05:58:17 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He, X. Liu, J. An, S.Q. Jiang, Z.P. Zhu, D. Xu (NAOC), S.Y. Fu, A.D. Zhu, L. Lei, H.Z. Wu (HUST), J.Z. Liu (XAO) report on behalf of a large collaboration: We observed the field of GRB 251013C (Fermi GBM team, GCN 42221; Rakotondrainibe et al., GCN 42222) using the 100C telescope of the JinShan project, located at Altay, Xinjiang, China. Observations started at 2025-10-16 13:23:15 UT, i. e., 2.822 days after the trigger, and a series of 300s frames in g, r, i, and z bands were obtained. The previously reported optical counterpart (e.g., Palmerio et al., GCN 42223; and many late GCNs) was clearly detected in all the four bands. Our preliminary analysis gives r = 21.04 +/- 0.06 at a median time 69 hrs post-burst. The magnitude was calibrated with nearby Pan-STARRS1 dr2 catalog and without the Galactic extinction correction, being consistent with the rebrightening reported in Méndez et al. (GCN 42318). The SED from the g/r/i/z bands is non-thermal, being consistent with the behavior of GRB optical afterglows. Also a SN1998bw-like supernova would be much fainter at this redshift (z=0.572). We acknowledge the excellent support from T.Q. Chen and J.F. Zhang for enabling these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42319. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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