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

[vsnet-grb-info 40444] GRB 251017A: COLIBRÍ optical observations of a late plateau
by GCN Circulars 19 Oct '25

19 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42368 SUBJECT: GRB 251017A: COLIBRÍ optical observations of a late plateau DATE: 25/10/19 08:30:13 GMT FROM: Dalya Akl at New York University Abu Dhabi <dka2010(a)nyu.edu> Dalya Akl (NYUAD), Margarita Pereyra (UNAM), Noémie Globus (UNAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Sarah Antier (IJCLAB), 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), Enrique Moreno Méndez (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the Swift GRB 251017A (Gupta et al., GCN Circ. 42322) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-10-19 01:57 to 05:53 UTC (from 41.48 to 45.22 hours after the trigger) and obtained 96 minutes of simultaneous exposure in the i and z filters. The data were 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. Compared to our observations on the previous night (Angulo et al., GCN Circ. 42348), we find the optical counterpart has faded by only Delta i = 0.06 +/- 0.04 We see similar behaviour in z. These results suggest that we may be observing a late plateau. Further observations are planned and encouraged. 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/42368. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40443] IceCube-251018A: DDOTI Optical Upper Limit
by GCN Circulars 19 Oct '25

19 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42367 SUBJECT: IceCube-251018A: DDOTI Optical Upper Limit DATE: 25/10/19 07:31:09 GMT FROM: Rosa Leticia Becerra Godínez at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Rosa L. Becerra (UNAM), 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 observe the field of the IceCube-251018A (gold) event (IceCube Collaboration, GCN Circ. 42352) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on the Sierra of San Pedro Martir (http://ddoti.astroscu.unam.mx) on the night of 2025-10-19 UTC. DDOTI observed from 03:00 UTC to 06:18 UTC (from T+21.9 h to T+25.2 h after the trigger) with a total exposure of 96 min, covering the total error region reported by IceCube (IceCube Collaboration, GCN Circ 42352). Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2, we detect no uncatalogued sources within the observed field to a 10-sigma limiting AB magnitude of: w > 20.6. Further observations are planned to assess variability. This value 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/42367. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40442] GRB 251017A: Swift-BAT refined analysis
by GCN Circulars 19 Oct '25

19 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42366 SUBJECT: GRB 251017A: Swift-BAT refined analysis DATE: 25/10/19 01:53:31 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> T. Parsotan (GSFC), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-60 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 251017A (trigger #1404904) (Gupta, et al., GCN Circ. 42322). The BAT ground-calculated position is RA, Dec = 335.404, 7.048 deg which is RA(J2000) = 22h 21m 37.0s Dec(J2000) = +07d 02' 54.4" with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 93%. The mask-weighted BAT light curve shows main emission followed by weaker emission. T90 (15-350 keV) is 116.90 +- 61.91 sec (estimated error including systematics). The time-averaged spectrum from T-5.48 to T+125.08 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.40 +- 0.20. The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+6.41 sec in the 15-150 keV band is 1.3 +- 0.2 ph/cm2/sec. 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/1404904 View this GCN Circular online at https://gcn.nasa.gov/circulars/42366. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40441] GRB 251016A: Fermi GBM Observation
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42365 SUBJECT: GRB 251016A: Fermi GBM Observation DATE: 25/10/18 23:23:26 GMT FROM: Jacob Smith at Fermi-GBM Team <jrs0118(a)uah.edu> Jacob Smith (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 14:59:19.76 UT on 16 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251016A (trigger 782319564/251016625), which is was detected by SVOM/ECLAIRs (Basa et al., GCN 42308), CALET-GBM (Kawakubo et al., GCN 42321), Glowbug (Woolf et al., GCN 42313) and Astro Sat CZTI (Arya et al., GCN 42327). The Fermi GBM on-ground location is consistent with the SVOM/ECLAIRs position. The angle from the Fermi LAT boresight is 42 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 0.32 s (50-300 keV). The time-averaged spectrum from T0-0.1 to T0+0.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.83 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 1317 +/- 145 keV. The event fluence (10-1000 keV) in this time interval is (3 +/- 0.08)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.13 s in the 10-1000 keV band is 34 +/- 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/42365. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40440] GRB 251018A: Fermi GBM Observation
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42364 SUBJECT: GRB 251018A: Fermi GBM Observation DATE: 25/10/18 21:53:57 GMT FROM: Glowbug DEV <boyan.a.hristov(a)nasa.gov> B. Hristov (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 03:12:00.63 UT on 18 October 2025 , the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 251018A (trigger 782449925 / 251018133), which was also detected by the Swift/XRT (R. Gupta et al. 2025, GCN 42343) The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 42 degrees. The GBM light curve consists of multiple peaks, with a duration (T90) of about 27.1 s (50-300 keV). The time-averaged spectrum from T0-6.1 s to T0+21.5 s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -0.91 +/- 0.09 and the cutoff energy, parameterized as Epeak, is 715 +/- 162 keV. The event fluence (10-1000 keV) in this time interval is (6.8 +/- 0.3)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3 s in the 10-1000 keV band 0.95 +/- 0.04 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/42364. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40439] GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42363 SUBJECT: GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections DATE: 25/10/18 20:48:38 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es> Y.-D. Hu (GXU), I. Perez-Garcia, A. J. Castro-Tirado, E. J. Fernandez-Garcia, M. D. Caballero-Garcia, S.-Y. Wu, R. Sanchez-Ramirez, and S. Guziy (IAA-CSIC), I. M. Carrasco (SMA), M. Gritsevich (Univ. of Helsinki), C. Perez del Pulgar (Univ. of Malaga), S. Jeong (ADD, Daejeon), G. Garcia-Segura and D. Hiriart (IA-UNAM, Ensenada), W. H. Lee (UNAM, Mexico DF), D.-R. Xiong (YNAO), B.-B. Zhang (NJU), and A. Maury (Space Obs., San Pedro de Atacama) on behalf of a larger collaboration, report: Following the detection of GRB251018A by Swift (Gupta et al., GCN 42343) and Fermi (Fermi GBM team, GCN 42342), the 0.6m BOOTES-5/JGU robotic telescope at San Pedro Martir Observatory (Mexico) automatically responded to this high-energy event starting on Oct 18, 03:12:45 UT (i.e., 43 sec after detection). Series of images in clear filter were gathered and we detect an optical source. Using USNO B-1.0 as a reference, we measure an initial magnitude of 16.78 +/- 0.16 in the first 1 x 5 s stacked image. Meanwhile, the 0.6m BOOTES-7 robotic telescope at Space Observatory (San Pedro de Atacama, Chile) also automatically observed the GRB location starting on Oct. 18, 03:13:22 UT (i.e. 80 s after trigger). The afterglow is also detected with 16.04 +/- 0.11. These detections are consistent with the one reported by MASTER (Lipunov et al., GCN 42346), TRT (Fu et al., GCN 42345), and UVOT (Kuin et al., GCN 42353). Further analysis of the additional images is ongoing. We would like to thank the staff at San Pedro Martir Observatory and San Pedro de Atacama Space Observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/42363. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40438] GRB 251018A: Swift-XRT refined Analysis
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42362 SUBJECT: GRB 251018A: Swift-XRT refined Analysis DATE: 25/10/18 19:10:27 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> E. Ambrosi (INAF-IASFPA) , J.A. Kennea (PSU), D.N. Burrows (PSU), S. Lanava (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), M. Capalbi (INAF-OAR), M. Perri (SSDC & INAF-OAR) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 7.5 ks of XRT data for GRB 251018A, from 63 s to 50.2 ks after the trigger. The data comprise 259 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 a power-law decay with a decay index of alpha=1.122 (+0.031, -0.029). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.68 (+0.15, -0.14). The best-fitting absorption column is 1.4 (+0.6, -0.5) x 10^21 cm^-2, consistent with the Galactic value of 9.4 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.81 (+0.25, -0.23) and a best-fitting absorption column of 2.1 (+1.1, -0.9) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.0 x 10^-11 (5.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.1 (+1.1, -0.9) x 10^21 cm^-2 Galactic foreground: 9.4 x 10^20 cm^-2 Excess significance: 2.0 sigma Photon index: 1.81 (+0.25, -0.23) If the light curve continues to decay with a power-law decay index of 1.122, the count rate at T+24 hours will be 6.4 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.6 x 10^-13 (3.3 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/01405083. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42362. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40437] GRB 251018A: Enhanced Swift-XRT position
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42361 SUBJECT: GRB 251018A: Enhanced Swift-XRT position DATE: 25/10/18 18:58:38 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 2660 s of XRT Photon Counting mode data and 4 UVOT images for GRB 251018A, 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 = 282.04220, -37.02921 which is equivalent to: RA (J2000): 18h 48m 10.13s Dec (J2000): -37d 01' 45.2" 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/42361. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40436] Fermi trigger No 782500909: Global MASTER-Net observations report
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42360 SUBJECT: Fermi trigger No 782500909: Global MASTER-Net observations report DATE: 25/10/18 18:01:02 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 GRB251018.72 (trigger No 782500909,16h 23m 38.40s , -85d 57m 00.0s, R=3.1) errorbox 721 sec after notice time and 754 sec after trigger time at 2025-10-18 17:34:19 UT, with upper limit up to 16.1 mag. Observations started at twilight. The observations began at zenith distance = 56 deg. The sun altitude is -9.4 deg. The galactic latitude b = -25 deg., longitude l = 307 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3017672 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 785 | 2025-10-18 17:34:19 | MASTER-SAAO | (16h 29m 10.44s , -85d 56m 26.8s) | C | 60 | 15.2 | 864 | 2025-10-18 17:35:38 | MASTER-SAAO | (16h 29m 10.67s , -85d 56m 25.2s) | C | 60 | 16.1 | 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/42360. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40435] GRB 251016A: HXMT/HE detection
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42359 SUBJECT: GRB 251016A: HXMT/HE detection DATE: 25/10/18 16:40:50 GMT FROM: xueyuan zao <zaoxueyuan(a)gmail.com> Xue-Yuan Zao, Chen-Wei Wang, Zheng-Hang Yu, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng report on behalf of the Insight-HXMT team: At 2025-10-16T14:59:19.750 (T0), Insight-HXMT/HE detected the short burst GRB 251016A, which is also detected by SVOM/ECLAIRs (Basa et al., GCN 42308), FERMI-GBM (Fermi GBM team, GCN 42309), CALET-GBM (Kawakubo et al., GCN 42321), Glowbug (Woolf et al., GCN 42313) and Astro Sat CZTI (Arya et al., GCN 42327). The Insight-HXMT/HE light curve mainly consists of a single pulse with a T90 of 0.34 +/-0.06 s. The total counts from this burst is 2297 counts. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251016A.png All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 30-1000 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/42359. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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