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

[vsnet-grb-info 40452] GRB 250911A: MAXI/GSC detection
by GCN Circulars 22 Oct '25

22 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42376 SUBJECT: GRB 250911A: MAXI/GSC detection DATE: 25/10/22 05:22:50 GMT FROM: Hitoshi Negoro at Nihon University/MAXI team <negoro.hitoshi(a)nihon-u.ac.jp> H. Negoro (Nihon U.), T. Mihara (RIKEN), M. Serino (AGU), M. Nakajima, K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, Y. Kawakubo, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, C. Kang, T. Nakamoto, M. Uenishi, T. Usuki, S. Yatsuzuka (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), and S. Yamada (Tohoku U), We report on the detection of GRB 250911A by MAXI (Swift-BAT: GCN 41781, 41812, COLIBRI: GCN 41782, Swift-XRT: GCN 41783, 41784, 41804, Swift-UVOT: 41800, MASTER: GCN 41806, GECAM-B: GCN 41813, Insight-HXMT: GCN 41827, Konus-Wind: GCN 41939). MAXI detected the burst for approximately 40 seconds, centered at around 01:29:46 on September 11, 2025. The period coincides with the main peak of the burst detected by Swift, HXMT, and Konus-Wind. The 4-10 keV X-ray flux averaged over the scan was 2041 ± 83 mCrab. The MAXI light curve is shown at https://maxi.riken.jp/grbs/250911a/ GRB 250911A was about 0.8 degrees away from the bright NS-LMXB GX 9+9. Due to the X-ray photon confusion from GX 9+9, we were unable to obtain firm upper limits or flux in the previous transit at 23:57 UT on September 10 and the next transit at 03:02 UT. Some software problem during the burst partly causes the late notice. View this GCN Circular online at https://gcn.nasa.gov/circulars/42376. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40451] LIGO/Virgo/KAGRA S251021u: Updated Sky localization
by GCN Circulars 21 Oct '25

21 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42375 SUBJECT: LIGO/Virgo/KAGRA S251021u: Updated Sky localization DATE: 25/10/21 16:18:24 GMT FROM: mattia.emma.2022(a)live.rhul.ac.uk The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) data around the time of the compact binary merger (CBC) candidate S251021u (GCN Circular 42373). 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/S251021u For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 3859 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 5884 +/- 2089 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/42375. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40450] GRB 251016A: SVOM/ECLAIRs refined analysis
by GCN Circulars 21 Oct '25

21 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42374 SUBJECT: GRB 251016A: SVOM/ECLAIRs refined analysis DATE: 25/10/21 11:52:34 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet, O. Godet, S. Guillot (IRAP), B. Hubert (CEA), S.Basa, S.Boissier (LAM) Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 251016A (SVOM burst-id sb2525101602, GCN 42308) detected at T0 = 2025-10-16T14:59:20, which was also detected by SVOM/GRM, Fermi/GBM (GCN 42309), CALET/GBM (GCN 42321), Glowbug (GCN 42313), AstroSat/CZTI (GCN 42327) and HXMT/HE (GCN 42359). The burst that triggered ECLAIRs consists of a single short peak, with a duration of T90 = 0.69 +0.09/-0.19 s in the 4-120 keV energy band. The time-averaged spectrum from the peak (T0-0.4 s to T0+0.4 s) in the 5-120 keV energy range is well fitted by a power-law model with a photon index of 1.00 +/-0.16, which is consistent with the results found by Smith at al. 2025 (GCN 42365). With this model, the total 4-120 keV fluence is (3.01 +0.27/-0.94) e-07 erg/cm^2 . All the quoted errors are at the 68% confidence level. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at irap.omp.eu). View this GCN Circular online at https://gcn.nasa.gov/circulars/42374. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40449] LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
by GCN Circulars 21 Oct '25

21 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42373 SUBJECT: LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate DATE: 25/10/21 03:49:52 GMT FROM: alvinli(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 S251021u during real-time processing of data from LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at 2025-10-21 03:22:15.181 UTC (GPS time: 1445052153.181). The candidate was found by the Aframe [1], cWB [2], cWB BBH [3], GstLAL [4], MBTA [5], PyCBC Live [6], and SPIIR [7] analysis pipelines. S251021u is an event of interest because its false alarm rate, as estimated by the online analysis, is 2.2e-09 Hz, or about one in 14 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S251021u 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%. [8] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [8] 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 (44.0, 88.0) 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: * amplfi.multiorder.fits,0, an initial localization generated by AMPLFI [9], distributed via GCN and SCiMMA notices about 25 seconds after the candidate event time. * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [10], distributed via GCN and SCiMMA notices about 4 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,0. For the bayestar.multiorder.fits,0 sky map, the 90% credible region is 3742 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 7164 +/- 2185 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] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [7] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [8] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [9] Chatterjee et al. MLST 5, 045030 (2024) doi:10.1088/2632-2153/ad8982 [10] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/42373. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40448] LIGO/Virgo/KAGRA S251018bi: Updated Sky localization
by GCN Circulars 20 Oct '25

20 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42372 SUBJECT: LIGO/Virgo/KAGRA S251018bi: Updated Sky localization DATE: 25/10/20 19:58:14 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 S251018bi (GCN Circular 42357). 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/S251018bi For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 883 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 4502 +/- 1313 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/42372. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40447] Fermi-LAT gamma-ray observations of IceCube-251018A
by GCN Circulars 19 Oct '25

19 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42371 SUBJECT: Fermi-LAT gamma-ray observations of IceCube-251018A DATE: 25/10/19 23:49:18 GMT FROM: Simone Garrappa at Weizmann Institute of Science <simone.garrappa(a)weizmann.ac.il> S. Garrappa (Weizmann Institute of Science), L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and C.Bartolini (Univ. of Trento & INFN Bari) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the IC251018A high-energy neutrino event (GCN 42351) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 25-10-18 at 05:05:42.97 UT (T0) with J2000 position RA = 321.11 (+3.09/-2.94) deg, Decl. = +41.31 (+2.46/-3.51) deg (90% PSF containment). There are three catalogued gamma-ray sources (4FGL-DR4; The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546) located within the 90% IC251018A localization region. These are: 4FGL J2118.3+4055: unassociated,at 1.2 deg distance from the best-fit neutrino position; 4FGL J2120.5+4331: unassociated, at 2.3 deg distance from the best-fit neutrino position; 4FGL J2136.5+4259: associated with the blazar of uncertain type TXS 2134+428, at 2.8 deg from the best-fit neutrino position; Based on a preliminary analysis of the LAT data over the timescale of one day and one month prior T0, these objects are not significantly detected at gamma-rays. We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) at the IC251018A bestfit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC251018A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 8.4 e-10 ph cm^-2 s^-1 for ~17-years (2008-08-04 / T0), < 7.4e-09 (<5.9e-08) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. In the analysis of the ~17-years integrated LAT data (100 MeV - 1 TeV), a 5 sigma new excess of gamma rays, Fermi J2125.8+3940 was detected 1.65 deg offset from the best-fit IC251018A position and within the 90% confidence localization of the direction of the neutrino. Assuming a power-law spectrum, the best-fit localization is (J2000) RA = 321.46 deg, Dec = +39.69 deg (6 arcmin 99% containment, 3 arcmin 68% containment). The gamma-ray best-fit spectral parameters are flux = (8 +/- 3)e-10 ph cm^-2 s^-1 and index = 1.84+/-0.12. In a preliminary analysis of the LAT data over 1-day and 1-month prior T0, Fermi J2125.8+3940 is not significantly detected in the LAT data. All values include the statistical uncertainty only. The statistical significance is calculated following the prescription adopted in the 4FGL (Abdollahi et al. 2020, ApJS, 247, 33). Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this region will continue. For these observations the Fermi-LAT contact person is S. Garrappa (simone.garrappa at weizmann.ac.il). The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/42371. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40446] GRB 251017A : RAPAS follow-up observations
by GCN Circulars 19 Oct '25

19 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42370 SUBJECT: GRB 251017A : RAPAS follow-up observations DATE: 25/10/19 21:33:07 GMT FROM: Thierry Midavaine at SAF - RAPAS <thierrymidavaine(a)sfr.fr> Thierry Midavaine on behalf of the RAPAS network reports (#5) : Pascal André, David Fardin, Patrick Martinez [1], Christian Pantacchini [2], Jean-Marie Lopez, Cyril Cavadore [3], Lisa Maris [4] observed the field of Gamma-Ray Burst GRB 251017A (R. Gupta et al. GCN 42322, I. Perez-Garcia GCN 42323) using : [1] ADAGIO N 820mm telescope f=3.1m at Belesta Observatory (IAU A05) equipped with a Moravian C3 CMOS camera, [2] N308 mm telescope f=1.1m equipped with a Moravian g3 KAI11000 CCD camera, [3] Société Astronomique de Montpellier N 500mm telescope f=2.2m at Observatoire des Pises (IAU 122) equipped with an ASI6200MMPro CMOS camera, [4] SC 280mm f=1.8m equipped with an ATIK4000 CCD camera. [1][2][3][4] are equipped with RAPAS filters meeting the Gaia G, Gbp, Grp photometric bands. The FITS files are reduced with the Gaia photometric catalog in respective G, Gbp and Grp bands. The afterglow is detected at RA(J2000) = 22h 21m 36.22s ; Dec(J2000) = +07° 02’ 23.6” ; ± 0.5’’ in G and Grp bands [1] RA(J2000) = 22h 21m 36.956s; Dec(J2000) = +07° 02’ 21.90” in G band [3] At this RA Dec location the GRB is above the respective upper limit magnitude Gbp for [1], G for [2] and [4], Gbp and Grp for [3] MJD (mid) Gaia band exp(s) mag.(Gaia) upperlim RAPAS station 60965.81618 G 1200 22.5 ± 0.3 [3] 60965.82986 G 4500 20.24 [4] 60965.83819 G 3600 22.0 ± 0.3 [1] 60965.83819 Gbp 600 21 [1] 60965.83819 Grp 600 >20.00 [1] 60965.89722 G [2] Acknowledgements : RAPAS ( https://gemini.obspm.fr/20220101-rapas/ ) is a ProAm collaboration created by T. Midavaine (SAF), W. Thuillot (LTE, Obs. de Paris-PSL) and M. Dennefeld (IAP/CNRS and Sorbonne Univ.) and funded by the Paris Observatory under API ProAm of the Scientific Council. It aims at homogenizing observing procedures and filters, and is delivering to a network of french amateur observatories a set of 3 filters which have been chosen to meet the Gaia G, Gbp and Grp spectral bands. This network produces data on astrophysical alerts delivered by various Alert systems (Gaia Alerts, Atlas, ZTF, etc…) and collected by Astro-COLIBRI ( https://astro-colibri.science ). This network is similarly progressing towards an homogeneous spectroscopic equipment to deliver SED. View this GCN Circular online at https://gcn.nasa.gov/circulars/42370. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40445] IceCube-251018A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 19 Oct '25

19 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42369 SUBJECT: IceCube-251018A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/10/19 18:45:31 GMT FROM: Yuhua Yao at IceCube/UW-Madison <yyao255(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-251018A (https://gcn.nasa.gov/circulars/42352) in a time range of 1000 seconds centered on the alert event time (2025-10-18 04:57:22.970 UTC to 2025-10-18 05:14:02.970 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-251018A. We report a p-value of 1.00 in this time window. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.5e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251018A in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 2e+02 GeV and 6e+04 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-10-17 05:05:42.970 UTC to 2025-10-19 05:05:42.970 UTC). In this case, we report a p-value of 0.02, consistent with no significant excess of track events. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, ranges from 1.7e-01 to 1.8e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251018A in a 2 day time window. 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. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/42369. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[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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[vsnet-grb-info 40434] IceCube Alert 251018.21: Global MASTER-Net observations report
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42358 SUBJECT: IceCube Alert 251018.21: Global MASTER-Net observations report DATE: 25/10/18 16:39:32 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the IceCube Alert 251018.21 (trigger No 22018019,21h 25m 13.92s , +39d 11m 09.6s, R=2.69) errorbox 39638 sec after notice time and 39688 sec after trigger time at 2025-10-18 16:07:11 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 8 deg. The sun altitude is -19.7 deg. The galactic latitude b = -8 deg., longitude l = 86 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3017315 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 22029 | 2025-10-18 11:12:21 | MASTER- | (21h 25m 26.91s , +38d 32m 19.1s) | C | 60 | 18.7 | Coadd 22142 | 2025-10-18 11:14:15 | MASTER- | (21h 34m 49.32s , +38d 32m 13.7s) | C | 60 | 18.4 | Coadd 22136 | 2025-10-18 11:14:33 | MASTER- | (21h 24m 42.35s , +40d 38m 41.0s) | C | 10 | 18.2 | 22149 | 2025-10-18 11:14:47 | MASTER- | (21h 24m 42.32s , +40d 38m 40.6s) | C | 10 | 18.3 | 22163 | 2025-10-18 11:15:00 | MASTER- | (21h 24m 42.33s , +40d 38m 40.8s) | C | 10 | 18.3 | 22176 | 2025-10-18 11:15:13 | MASTER- | (21h 24m 42.36s , +40d 38m 40.0s) | C | 10 | 18.3 | 22189 | 2025-10-18 11:15:27 | MASTER- | (21h 24m 42.37s , +40d 38m 39.1s) | C | 10 | 18.3 | 22203 | 2025-10-18 11:15:40 | MASTER- | (21h 24m 42.39s , +40d 38m 39.0s) | C | 10 | 18.3 | 22216 | 2025-10-18 11:15:54 | MASTER- | (21h 24m 42.42s , +40d 38m 38.2s) | C | 10 | 18.3 | 22230 | 2025-10-18 11:16:07 | MASTER- | (21h 24m 42.40s , +40d 38m 37.6s) | C | 10 | 18.2 | 22244 | 2025-10-18 11:16:21 | MASTER- | (21h 24m 42.40s , +40d 38m 37.0s) | C | 10 | 18.2 | 22266 | 2025-10-18 11:16:43 | MASTER- | (21h 24m 42.40s , +40d 38m 36.1s) | C | 10 | 18.4 | 22280 | 2025-10-18 11:16:58 | MASTER- | (21h 24m 42.41s , +40d 38m 35.3s) | C | 10 | 18.4 | 22294 | 2025-10-18 11:17:11 | MASTER- | (21h 24m 42.40s , +40d 38m 34.7s) | C | 10 | 18.4 | 22307 | 2025-10-18 11:17:25 | MASTER- | (21h 24m 42.46s , +40d 38m 34.3s) | C | 10 | 18.3 | 22324 | 2025-10-18 11:17:38 | MASTER- | (21h 24m 42.44s , +40d 38m 34.3s) | C | 15 | 18.7 | 22342 | 2025-10-18 11:17:57 | MASTER- | (21h 24m 42.43s , +40d 38m 32.8s) | C | 15 | 18.7 | 22361 | 2025-10-18 11:18:16 | MASTER- | (21h 24m 42.47s , +40d 38m 32.7s) | C | 15 | 18.7 | 22380 | 2025-10-18 11:18:34 | MASTER- | (21h 24m 42.47s , +40d 38m 31.2s) | C | 15 | 18.7 | 22398 | 2025-10-18 11:18:52 | MASTER- | (21h 24m 42.73s , +40d 38m 28.8s) | C | 15 | 17.7 | 22417 | 2025-10-18 11:19:11 | MASTER- | (21h 24m 42.65s , +40d 38m 27.9s) | C | 15 | 17.4 | 22987 | 2025-10-18 11:28:20 | MASTER- | (21h 31m 15.12s , +40d 24m 56.9s) | C | 60 | 19.3 | Coadd 23065 | 2025-10-18 11:29:38 | MASTER- | (21h 20m 28.77s , +36d 38m 22.6s) | C | 60 | 19.3 | Coadd 23238 | 2025-10-18 11:32:30 | MASTER- | (21h 24m 47.36s , +40d 38m 33.7s) | C | 60 | 19.4 | Coadd 23395 | 2025-10-18 11:35:08 | MASTER- | (21h 24m 39.85s , +40d 38m 56.5s) | C | 60 | 19.6 | Coadd 23440 | 2025-10-18 11:35:53 | MASTER- | (21h 26m 55.46s , +34d 43m 11.4s) | C | 60 | 19.6 | 23514 | 2025-10-18 11:37:06 | MASTER- | (21h 24m 38.44s , +40d 36m 49.8s) | C | 60 | 19.6 | 23586 | 2025-10-18 11:38:19 | MASTER- | (21h 31m 14.78s , +40d 24m 32.2s) | C | 60 | 19.6 | 23659 | 2025-10-18 11:39:32 | MASTER- | (21h 20m 28.45s , +36d 37m 54.8s) | C | 60 | 19.4 | 23810 | 2025-10-18 11:42:03 | MASTER- | (21h 24m 45.36s , +40d 38m 28.6s) | C | 60 | 19.6 | 23959 | 2025-10-18 11:44:31 | MASTER- | (21h 24m 41.51s , +40d 38m 32.1s) | C | 60 | 19.6 | 24033 | 2025-10-18 11:45:46 | MASTER- | (21h 39m 37.95s , +36d 37m 01.8s) | C | 60 | 19.9 | 24113 | 2025-10-18 11:47:06 | MASTER- | (21h 26m 55.34s , +34d 43m 32.1s) | C | 60 | 19.6 | 24186 | 2025-10-18 11:48:19 | MASTER- | (21h 24m 38.56s , +40d 37m 23.4s) | C | 60 | 19.6 | 24261 | 2025-10-18 11:49:34 | MASTER- | (21h 31m 08.05s , +40d 25m 50.0s) | C | 60 | 19.6 | 24335 | 2025-10-18 11:50:47 | MASTER- | (21h 20m 31.98s , +36d 36m 32.3s) | C | 60 | 19.4 | 24673 | 2025-10-18 11:56:25 | MASTER- | (21h 38m 44.90s , +37d 40m 08.5s) | C | 60 | 19.7 | 24746 | 2025-10-18 11:57:39 | MASTER- | (21h 26m 06.59s , +35d 44m 31.8s) | C | 60 | 19.6 | 24911 | 2025-10-18 12:00:24 | MASTER- | (21h 30m 14.16s , +41d 26m 28.4s) | C | 60 | 19.5 | 24992 | 2025-10-18 12:01:44 | MASTER- | (21h 19m 42.75s , +37d 38m 24.3s) | C | 60 | 19.5 | 25296 | 2025-10-18 12:06:48 | MASTER- | (21h 38m 47.62s , +37d 39m 00.3s) | C | 60 | 19.9 | 25372 | 2025-10-18 12:08:04 | MASTER- | (21h 26m 09.90s , +35d 45m 43.2s) | C | 60 | 19.7 | 25618 | 2025-10-18 12:12:11 | MASTER- | (21h 30m 14.23s , +41d 26m 02.8s) | C | 60 | 19.5 | 25692 | 2025-10-18 12:13:25 | MASTER- | (21h 19m 42.14s , +37d 37m 52.9s) | C | 60 | 19.5 | 25916 | 2025-10-18 12:17:08 | MASTER- | (21h 38m 41.75s , +37d 38m 43.9s) | C | 60 | 19.9 | 25989 | 2025-10-18 12:18:21 | MASTER- | (21h 26m 04.07s , +35d 45m 22.4s) | C | 60 | 19.6 | 26238 | 2025-10-18 12:22:30 | MASTER- | (21h 30m 15.89s , +41d 26m 02.0s) | C | 60 | 19.6 | 26312 | 2025-10-18 12:23:45 | MASTER- | (21h 19m 42.33s , +37d 38m 56.0s) | C | 60 | 19.5 | 26642 | 2025-10-18 12:29:15 | MASTER- | (21h 38m 40.69s , +37d 39m 18.2s) | C | 60 | 20.0 | 26716 | 2025-10-18 12:30:28 | MASTER- | (21h 26m 03.39s , +35d 42m 50.9s) | C | 60 | 19.6 | 27298 | 2025-10-18 12:40:11 | MASTER- | (21h 38m 41.77s , +37d 38m 45.3s) | C | 60 | 19.9 | 39779 | 2025-10-18 16:07:11 | MASTER-Kislovodsk | (21h 23m 12.87s , +39d 31m 52.3s) | C | 180 | 18.3 | 39959 | 2025-10-18 16:07:11 | MASTER-Kislovodsk | (21h 23m 12.87s , +39d 31m 52.2s) | C | 540 | 18.6 | Coadd 39779 | 2025-10-18 16:07:11 | MASTER-Kislovodsk | (21h 28m 59.97s , +39d 09m 35.7s) | C | 180 | 18.7 | 39919 | 2025-10-18 16:10:31 | MASTER-Kislovodsk | (21h 29m 03.89s , +41d 25m 46.0s) | C | 60 | 17.5 | 39919 | 2025-10-18 16:10:31 | MASTER-Kislovodsk | (21h 35m 00.82s , +41d 03m 22.0s) | C | 60 | 18.1 | 40059 | 2025-10-18 16:11:51 | MASTER-Kislovodsk | (21h 23m 12.96s , +39d 29m 49.4s) | C | 180 | 18.2 | 40059 | 2025-10-18 16:11:51 | MASTER-Kislovodsk | (21h 29m 00.21s , +39d 07m 33.0s) | C | 180 | 18.6 | 40199 | 2025-10-18 16:15:11 | MASTER-Kislovodsk | (21h 32m 40.41s , +39d 30m 38.4s) | C | 60 | 17.3 | 40199 | 2025-10-18 16:15:11 | MASTER-Kislovodsk | (21h 38m 27.62s , +39d 08m 21.8s) | C | 60 | 17.9 | 40339 | 2025-10-18 16:16:31 | MASTER-Kislovodsk | (21h 23m 15.28s , +39d 31m 25.2s) | C | 180 | 18.2 | 40339 | 2025-10-18 16:16:31 | MASTER-Kislovodsk | (21h 29m 02.86s , +39d 09m 10.0s) | C | 180 | 18.5 | 40706 | 2025-10-18 16:23:38 | MASTER-Kislovodsk | (21h 28m 41.27s , +41d 26m 54.8s) | C | 60 | 17.8 | 40706 | 2025-10-18 16:23:39 | MASTER-Kislovodsk | (21h 34m 56.99s , +41d 04m 17.1s) | C | 60 | 18.4 | 40846 | 2025-10-18 16:24:59 | MASTER-Kislovodsk | (21h 22m 51.36s , +39d 31m 08.1s) | C | 180 | 18.3 | 40846 | 2025-10-18 16:24:59 | MASTER-Kislovodsk | (21h 28m 56.82s , +39d 08m 19.4s) | C | 180 | 18.7 | 40986 | 2025-10-18 16:28:18 | MASTER-Kislovodsk | (21h 32m 12.06s , +39d 32m 51.9s) | C | 60 | 17.7 | 40986 | 2025-10-18 16:28:18 | MASTER-Kislovodsk | (21h 38m 17.80s , +39d 09m 55.3s) | C | 60 | 18.2 | 41126 | 2025-10-18 16:29:38 | MASTER-Kislovodsk | (21h 22m 59.40s , +39d 31m 04.5s) | C | 180 | 18.6 | 41126 | 2025-10-18 16:29:38 | MASTER-Kislovodsk | (21h 29m 05.14s , +39d 07m 57.1s) | C | 180 | 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/42358. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40433] LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42357 SUBJECT: LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate DATE: 25/10/18 16:05:11 GMT FROM: shoki.iwaguchi(a)ligo.org The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S251018bi during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-10-18 15:25:47.021 UTC (GPS time: 1444836365.021). The candidate was found by the Aframe [1], cWB [2], cWB BBH [3], GstLAL [4], MBTA [5], PyCBC Live [6], and SPIIR [7] analysis pipelines. S251018bi 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/S251018bi 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%. [8] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [8] 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: * amplfi.multiorder.fits,0, an initial localization generated by AMPLFI [9], distributed via GCN and SCiMMA notices about 23 seconds after the candidate event time. * bayestar.multiorder.fits,0, 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,0. For the bayestar.multiorder.fits,0 sky map, the 90% credible region is 1463 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 5450 +/- 1489 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] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [7] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [8] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [9] Chatterjee et al. MLST 5, 045030 (2024) doi:10.1088/2632-2153/ad8982 [10] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/42357. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40432] GRB 251016A: Swift-XRT afterglow detection
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42356 SUBJECT: GRB 251016A: Swift-XRT afterglow detection DATE: 25/10/18 13:49:20 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , 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) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of GRB 251016A. We searched for X-ray sources in 3.5 ks of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 5.6 ks, obtained between T0+6.6 ks and T0+107.3 ks. Thirty-two uncatalogued X-ray sources are detected, of which one ("Source 1") is fading with >3-sigma significance, and is therefore likely the GRB afterglow. Using 1190 s of PC mode data and 2 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 = 266.30279, -39.56008 which is equivalent to: RA (J2000): 17h 45m 12.67s Dec(J2000): -39d 33' 36.3" with an uncertainty of 3.2 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=4.53 (+0.08, -3.08). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.4 (+1.0, -0.6). The best-fitting absorption column is 4.8 (+8.8, -0.9) x 10^21 cm^-2, consistent with the Galactic value of 3.9 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 6.4 x 10^-11 (8.0 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 4.8 (+8.8, -0.9) x 10^21 cm^-2 Galactic foreground: 3.9 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 1.4 (+1.0, -0.6) The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/03000141. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/SVOM/SVOM_FIELD00042. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42356. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40431] GRB 251017A: Swift/UVOT Detection
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42355 SUBJECT: GRB 251017A: Swift/UVOT Detection DATE: 25/10/18 12:06:08 GMT FROM: s.shilling(a)lancaster.ac.uk S. P. R. Shilling (Lancaster U.) and R. Gupta (NASA GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251017A 98 s after the BAT trigger (Gupta et al., GCN Circ. 42322). A source consistent with the enhanced XRT position (Goad et al., GCN Circ. 42326) is detected in the initial UVOT exposures. 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 121 270 147 20.09 +/- 0.22 v 98 1234 109 >18.8 b 588 5138 83 >19.6 u 333 5126 501 >20.3 w1 712 4921 255 >18.5 w2 811 1384 58 >20.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.108 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42355. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40430] GRB 251016A: Swift/UVOT Detection
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42354 SUBJECT: GRB 251016A: Swift/UVOT Detection DATE: 25/10/18 12:05:09 GMT FROM: s.shilling(a)lancaster.ac.uk S.P.R. Shilling (Lancaster U.) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251016A, detected by SVOM/ECLAIRs (Basa et al., GCN Circ. 42308) and Fermi/GBM (Fermi GBM team, GCN Circ. 42309), 6.66 ks after the SVOM/ECLAIRs trigger. A source is detected in the optical by the Swift/UVOT at a position that is consistent with the likely X-ray counterpart detected by the Swift/XRT (Source 1: Evans et al., GCN Circ. 42311). Preliminary detections and upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the images are: Filter T_start(ks) T_stop(ks) Exp(s) Mag u 6.66 12.6 491.7 19.13 +/- 0.26 b 6.91 12.7 296.0 18.70 +/- 0.18 v 7.42 7.67 245.8 17.52 +/- 0.15 w1 12.1 12.4 245.8 >18.93 w2 7.17 7.42 245.8 >19.05 m2 7.68 7.85 168.3 >18.66 The magnitudes reported here are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42354. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40429] GRB 251018A: Swift/UVOT Detection
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42353 SUBJECT: GRB 251018A: Swift/UVOT Detection DATE: 25/10/18 11:57:31 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> N.P.M. Kuin (MSSL-UCL) and R. Gupta (NASA GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251018A 84 s after the BAT trigger (Gupta et al., GCN Circ. 42343). A source consistent with the XRT position is detected in the initial UVOT exposures. 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 84 128 44 17.98 +/- 0.08 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.101 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42353. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40428] IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42352 SUBJECT: IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/10/18 11:11:12 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-10-18 at 05:05:42.97 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 0.2566 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/141495_22018019.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-10-18 Time: 05:05:42.97 UT RA: 321.11 (+3.09/-2.94 deg 90% PSF containment) J2000 Dec: 41.31 (+2.46/-3.51 deg 90% PSF containment) J2000 Two gamma-ray sources listed in the Fermi 4FGL-DR4 catalog are located within the 90% uncertainty region of the event, both with no clear multi-wavelength counterpart and classification: 4FGL J2118.3+4055 and 4FGL J2120.5+433, situated 1.3 deg and 2.3 deg away from the best-fit direction of our alert, respectively. We encourage follow-up observations by both ground- and space-based instruments to help identify a possible astrophysical counterpart to the candidate neutrino. 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/42352. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40427] IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42351 SUBJECT: IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/10/18 11:10:28 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-10-18 at 05:05:42.97 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 0.2566 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/141495_22018019.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-10-18 Time: 05:05:42.97 UT RA: 321.11 (+3.09/-2.94 deg 90% PSF containment) J2000 Dec: 41.31 (+2.46/-3.51 deg 90% PSF containment) J2000 Two gamma-ray sources listed in the Fermi 4FGL-DR4 catalog are located within the 90% uncertainty region of the event, both with no clear multi-wavelength counterpart and classification: 4FGL J2118.3+4055 and 4FGL J2120.5+433, situated 1.3 deg and 2.3 deg away from the best-fit direction of our alert, respectively. We encourage follow-up observations by both ground- and space-based instruments to help identify a possible astrophysical counterpart to the candidate neutrino. 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/42351. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40426] GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42350 SUBJECT: GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327 DATE: 25/10/18 10:50:11 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> L. Izzo (INAF/OACn & DARK/NBI), A. Saccardi (CEA/Irfu), M. Garnichey (LUX-Paris Obs.), M. Ferro (INAF-OABr), A. Martin-Carrillo (UCD), D. B. Malesani (DAWN/NBI and Radboud), N. R. Tanvir (U. Leicester), A. L. Thakur (INAF-IAPS), G. Corcoran (UCD), report on behalf of the Stargate collaboration: We observed the optical afterglow (Perez-Garcia et al., GCN 42323; Antier et al., GCN 42325; Goad et al., GCN 42326; Sasada et al., GCN 42329; Lipunov et al., GCN 42330; Fu et al., GCN 42331; Mo et al., GCN 42336; Adami et al., GCN 42339; Xin et al., GCN 42341) of GRB 251017A (Gupta et al., GCN 42322; Woolf et al., GCN 42335), using the ESO VLT UT4 (Yepun) equipped with the MUSE spectrograph. The mid time of our observation was 2025 Oct 18 01:14:28 UT (16.56 hr after the GRB trigger), and consisted of 8 exposures of 700 s each. We extracted a 1D spectrum centered on the afterglow emission, using an aperture radius of 0.6 arcsec. In the reduced spectrum, which covers the wavelength range 4750 - 9330 AA, we detect a clear continuum and a trough due to Lya absorption visible at ~6470 AA. From the identification of several absorption features as due to Si II, Si II*, O I, O I*, CII, C II*, Si IV, C IV, Fe II, Al II, we infer a common redshift of z=4.327 for the GRB. We note that our spectroscopic redshift measurement is consistent with the photometric redshift value provided by Angulo et al. (GCN 42348). We acknowledge expert support from the observing staff in Paranal, in particular Robert de Rosa, Miguel Lopez, Thallis Pessi and Julien Drevon. The analysis of this spectrum was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495) View this GCN Circular online at https://gcn.nasa.gov/circulars/42350. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40425] GRB 251016A: VLT/FORS2 Optical Observation
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42349 SUBJECT: GRB 251016A: VLT/FORS2 Optical Observation DATE: 25/10/18 09:53:25 GMT FROM: Roberto Ricci at INAF-IRA <ricci(a)ira.inaf.it> Roberto Ricci (U Rome), Niccolo Passaleva ( U Rome) and Eleonora Troja (U Rome) report: We observed the field of the short duration GRB 251016A 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) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations started on Oct 16th, 2025 at 23:45 UT (~9 hours after the SVOM trigger) and were carried out in the I_BESS filter with an average airmass of ~1.3. The GRB lies within a very crowded region at low Galactic latitude. Several optical sources are detected within the localization of Swift/XRT Source #1 (Evans et al., GCN 42311). Objects brighter than 24 AB mag have counterparts in the GAIA DR3 catalogue (Babusiaux et al., 2023), however several fainter (>24 AB mag) sources remain unmatched. Further observations are planned to determine variability. 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/42349. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40424] GRB 251017A: COLIBRÍ photometric redshift
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42348 SUBJECT: GRB 251017A: COLIBRÍ photometric redshift DATE: 25/10/18 09:05:51 GMT FROM: Ny Avo Rakotondrainibe at LAM <nyavo.rakotobe(a)gmail.com> Camila Angulo (UNAM), Ny Avo Rakotondrainibe (LAM), Alan M. Watson (UNAM), Sarah Antier (IJCLAB), Dalya Akl (NYUAD), Enrique Moreno Méndez (UNAM), Noémie Globus (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), 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: COLIBRÍ performed follow-up observations of the Swift Swift GRB 251017A (Gupta et al., GCN Circ. 42322) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-10-18 02:20 to 03:20 UTC (from 17.65 h to 18.65 h after the trigger) and obtained 60 minutes of exposure in the g/r/i/z/y 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. After correcting for the Galactic foreground extinction corresponding to a reddening of E(B-V) = 0.092 mag (Schlafly & Finkbeiner 2011) and fitting a power-law model to the grizy-bands using the SMC extinction curve, we derive a photometric redshift of z = 4.34+0.15-0.42 (1-sigma c.l.). 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/42348. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40423] GRB 251017A: Swift-XRT refined Analysis
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42347 SUBJECT: GRB 251017A: Swift-XRT refined Analysis DATE: 25/10/18 08:54:16 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M. Capalbi (INAF-OAR) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 5.3 ks of XRT data for GRB 251017A, from 96 s to 39.9 ks after the trigger. The data comprise 75 s in Windowed Timing (WT) mode (the first 11 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The late-time light curve (from T0+4.7 ks) can be modelled with a power-law decay with a decay index of alpha=1.1 (+0.4, -0.3). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.67 (+/-0.15). The best-fitting absorption column is 1.4 (+/-0.5) x 10^21 cm^-2, consistent with the Galactic value of 8.9 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.09 (+0.22, -0.21) and a best-fitting absorption column of 1.9 (+0.8, -0.7) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.9 (+0.8, -0.7) x 10^21 cm^-2 Galactic foreground: 8.9 x 10^20 cm^-2 Excess significance: 2.5 sigma Photon index: 2.09 (+0.22, -0.21) If the light curve continues to decay with a power-law decay index of 1.1, the count rate at T+24 hours will be 7.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.5 x 10^-13 (3.5 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/01404904. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42347. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40422] GRB 251018A: MASTER OT detection
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42346 SUBJECT: GRB 251018A: MASTER OT detection DATE: 25/10/18 07:51:23 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V. Lipunov, I.Panchenko, A.Kuznetsov, G.Antipov, P.Balanutsa, E.Gorbovskoy, K.Zhirkov, N.Tiurina, A.Sankovich, Ya.Kechin, Yu. Tselik, M.Shilova, A.Chasovnikov, V.Topolev, V.Senik, D.Vlasenko, V.Shumkov, K.Vetrov, P.Rudominskaya (Lomonosov MSU, SAI, Moscow), 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.Sosnovskij (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 MASTER Global Robotic Net [1-4] started Fermi (GCN 42342) and Swift GRB 251018A (Gupta et al. GCN 42343, Trigger time 2025-10-18 03:12:02UT) 105s after notice time (141s after trigger time) at 2025-10-18 03:14:24 UT (Lipunov et al. GCN 42344, cover map and OT https://master.sai.msu.ru/site/master2/observ.php?id=3017251 There is MASTER OT J184810.01-370141.6,detected since first image (03:14:24) with m_OT=16.5 at 2025-10-18 03:16:46 (unfiltered, automatically calculated) This OT was discovered by Swift-UVOT (Gupta et al. GCN 42343) and observed by TRT (S.Y.Fu et al. GCN 42345) at the same time. Observation and reduction will be continued. [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/42346. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40421] GRB 251018A: TRT optical afterglow detection
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42345 SUBJECT: GRB 251018A: TRT optical afterglow detection DATE: 25/10/18 07:07:26 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> S.Y. Fu (HUST), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), Z.P. Zhu, L.B. He, X. Liu, J. An, S.Q. Jiang, D. Xu (NAOC) report on behalf of a large collaboration: We observed the field of GRB 251018A (Gupta et al., GCN 423243) using the 0.7-m telescope of the Thai Robotic Telescope (TRT) network, located at Cerro Tololo Inter-American Observatory, Chile. Observations started at 2025-10-17 03:14:29.2 UT, i. e., 147 s after the trigger, and a series frames in the Sloan r filter were obtained. An uncatalogued and varying optical transient (OT) is clearly detected at the Swift-UVOT position (Gupta et al., GCN 42343), with r = 17.96 +/-0.03 (AB) at ~ 865 s post-burst, calibrated with nearby SKYMAPPER-DR2 catalog and without the Galactic extinction correction. We thus confirm that the OT is indeed the optical afterglow of the burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/42345. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40420] Swift GRB 251018A: Global MASTER-Net observations report
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42344 SUBJECT: Swift GRB 251018A: Global MASTER-Net observations report DATE: 25/10/18 03:28:45 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) was pointed to the Swift GRB 251018A ( R. Gupta et al., GCN 42343) errorbox 105 sec after notice time and 141 sec after trigger time at 2025-10-18 03:14:24 UT, with upper limit up to 18.4 mag. The observations began at zenith distance = 68 deg. The sun altitude is -46.5 deg. The galactic latitude b = -16 deg., longitude l = 359 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3017251 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 147 | MASTER-OAFA | C | 10 | 17.8 | 168 | MASTER-OAFA | C | 20 | 18.3 | 194 | MASTER-OAFA | C | 20 | 18.2 | 225 | MASTER-OAFA | C | 30 | 18.4 | 263 | MASTER-OAFA | C | 30 | 18.4 | 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/42344. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40419] GRB 251018A: Swift detection of a burst with an optical counterpart
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42343 SUBJECT: GRB 251018A: Swift detection of a burst with an optical counterpart DATE: 25/10/18 03:25:45 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> R. Gupta (NASA GSFC), R. Brivio (INAF-OAB), S. Dichiara (PSU), M. Ferro (INAF-OAB), D. M. Palmer (LANL), T. Sbarrato (INAF-OAB) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 03:12:02 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 251018A (trigger=1405083). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 282.071, -37.028 which is RA(J2000) = 18h 48m 17s Dec(J2000) = -37d 01' 41" 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 60 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 03:13:16.7 UT, 74.4 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 282.0433, -37.0265 which is equivalent to: RA(J2000) = 18h 48m 10.39s Dec(J2000) = -37d 01' 35.4" with an uncertainty of 6.3 arcseconds (radius, 90% containment). This location is 79 arcseconds from the BAT onboard position, within the BAT error circle. The initial flux in the 2.5 s image was 5.19e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 83 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 18:48:10.04 = 282.04183 DEC(J2000) = -37:01:42.2 = -37.02840 with a 90%-confidence error radius of about 0.62 arc sec. This position is 8.0 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.96 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.100. 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/42343. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40418] GRB 251018A: Fermi GBM Final Real-time Localization
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42342 SUBJECT: GRB 251018A: Fermi GBM Final Real-time Localization DATE: 25/10/18 03:19:29 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 03:12:00 UT on 18 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251018A (trigger 782449925.633958 / 251018133). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 294.7, Dec = -40.3 (J2000 degrees, equivalent to J2000 19h 38m, -40d 17'), with a statistical uncertainty of 6.8 degrees. The angle from the Fermi LAT boresight is 36.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251018133/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251018133/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251018133/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42342. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40417] GRB 251017A: SVOM/VT optical observation
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42341 SUBJECT: GRB 251017A: SVOM/VT optical observation DATE: 25/10/18 02:40:22 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L. P. Xin, H. L. Li, Y. N. Ma, 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 GRB 251017A detected by Swift/BAT (Gupta et al., GCN 42322) and Glowbug (Woolf et al., GCN 42335;), starting at 2025-10-17T09:17:19 UTC, 37 min after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical counterpart (Perez-Garcia et al., GCN 42323; Antier et al., GCN 42325; Goad et al., GCN 42326; Sasada et al., GCN 42329; Lipunov et al., GCN 42330; Fu et al., GCN 42331; Mo et al., GCN 42336, Adami et al. GCN 42339) is detected in both channels. Mid-time | exposure time (s) | band | Magnitude (AB) ---------|-------------------|------|----------------- 3.96 h | 27*70 | VT_B | 22.57+/-0.14 3.96 h | 27*70 | VT_R | 20.30+/-0.05 Given the red color from the VT data, it is likely a medium/high redshift burst with a redshift > 4. Our photometry was in AB magnitude and not corrected for Galactic extinction. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre 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/42341. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40416] GRB 251011A: Fermi GBM Observation
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42340 SUBJECT: GRB 251011A: Fermi GBM Observation DATE: 25/10/18 02:27:15 GMT FROM: rhamburg(a)usra.edu R. Hamburg (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 03:41:40.09 UT on 11 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251011A (trigger 781846905/251011154), which was also detected by AstroSat (Tembhurnikar et al. 2025, GCN 42199), Insight-HMXT (Wang et al. 2025, GCN 42210), and Swift-BAT/GUANO (DeLaunay et al. 2025, GCN 42245). The Fermi GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 62 degrees. The GBM light curve consists of a multi-peaked structure with a duration (T90) of about 4.9 s (50-300 keV). The time-averaged spectrum from T0-0.7 to T0+4.9 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.76 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 136 +/- 1 keV. The event fluence (10-1000 keV) in this time interval is (3.26 +/- 0.07)E-06 ergs/cm^2 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.8 s in the 10-1000 keV band is 11.5 +/- 0.3 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak = 125 +/- 1 keV, alpha = -0.69 +/- 0.01 and beta = -2.70 +/- 0.04. 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/42340. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40415] GRB 251017A: OHP/T193 i-band observations
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42339 SUBJECT: GRB 251017A: OHP/T193 i-band observations DATE: 25/10/17 22:08:45 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> C. Adami (LAM/Pytheas/AMU), N.A. Rakotondrainibe (LAM), E. Le Floc'h (CEA/Irfu), S. Basa (Pytheas/OHP/LAM), B. Schneider (LAM), report on behalf of the MISTRAL GRB collaboration: We carried out observations of the GRB 251017A (Gupta et al., GCN 42322; Perez-Garcia et al., GCN 42323; Antier et al., GCN 42325; Goad et al., GCN 42326; Sasada et al., GCN 42329; Lipunov et al., GCN 42330; Fu et al., GCN 42331; Woolf et al., GCN 42335; Mo et al., GCN 42336) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 3 exposures of 3min and 2 exposures of 10min in the i-band at a mid time of 2025-10-17 19:52:19UT, corresponding to T-T0 = 11.19 hr. The afterglow is detected and we measured the following preliminary magnitude: i’ = 21.39+/-0.32 mag (AB) 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 Yoann Degot-longhi and the SOPHIE observers H. Bouy View this GCN Circular online at https://gcn.nasa.gov/circulars/42339. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40414] GRB 251013C: OHP/T193 third epoch optical observations and detected rebrightening
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42338 SUBJECT: GRB 251013C: OHP/T193 third epoch optical observations and detected rebrightening DATE: 25/10/17 21:44:41 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> C. Adami (LAM/Pytheas/AMU), N.A. Rakotondrainibe (LAM), E. Le Floc'h (CEA/Irfu), S. Basa (Pytheas/OHP/LAM), B. Schneider (LAM), report on behalf of the MISTRAL GRB collaboration: We carried out further observations of the GRB 251013C optical, NIR, and radio 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 ; Laskar et al., GCN 42243; 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; Adami et al., GCN 42276; Globus et al., GCN 42279; Abidkhanov et al., 42283; Rhodes et al., GCN 42294; Siegel et al., GCN 42298; Leonini et al., GCN 42301; Christy et al., GCN 42312; Moreno Méndez et al., GCN 42318; He et al., GCN 42319; Pavoni et al., GCN 42333; Bochenek et al., GCN 42334) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 4 exposures of 10min in the r-band at a mid time of 2025-10-17 19:05:33UT, corresponding to T-T0 = 97.43 hr. The afterglow is well detected and we measured the following preliminary magnitude: r’ = 20.74+/-0.06 mag (AB) This clearly shows a rebrightening as compared to our second epoch observations (r’ = 21.29 +/- 0.07), consistently with the results of Moreno Méndez et al. (GCN 42318). 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 Yoann Degot-longhi and the SOPHIE observers H. Bouy View this GCN Circular online at https://gcn.nasa.gov/circulars/42338. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40413] LIGO/Virgo/KAGRA S251017di: Retraction of GW compact binary merger candidate
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42337 SUBJECT: LIGO/Virgo/KAGRA S251017di: Retraction of GW compact binary merger candidate DATE: 25/10/17 21:38:45 GMT FROM: shoki.iwaguchi(a)ligo.org The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: The trigger S251017di is no longer considered to be a candidate of interest. This candidate was initially identified by one or more early-warning analyses by matching partial signal templates to the data. Analysis of additional data up to the putative merger time, with full signal templates, did not make a significant detection, indicating that the initial candidate was likely due to transient noise. View this GCN Circular online at https://gcn.nasa.gov/circulars/42337. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40412] GRB 251017A: J-band detection with WINTER
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42336 SUBJECT: GRB 251017A: J-band detection with WINTER DATE: 25/10/17 21:17:36 GMT FROM: Geoffrey Mo at Caltech / Carnegie Observatories <gmo(a)mit.edu> Geoffrey Mo (Caltech/Carnegie), Tomas Ahumada (Caltech), Viraj Karambelkar (Columbia), Benjamin Schneider (LAM), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of GRB 251017A (Gupta et al., GCN 42322; Goad et al., GCN 42326; Woolf et al., GCN 42335) in the near-infrared J band with the Palomar 1-m telescope, equipped with the 1.2-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations began at 2025-10-17T09:01:23 UTC in the J band (~21 minutes after the GRB trigger), consisting of 15 x 120 s exposures. The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565) We detect a clear source at the optical counterpart location (Gupta et al., GCN 42322; Perez-Garcia et al., GCN 42323; Antier et al., GCN 42325; Sasada et al., GCN 42329; Lipunov et al., GCN 42330; Fu et al., GCN 42331), with magnitude J ~ 18.7 mag (AB). WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research. View this GCN Circular online at https://gcn.nasa.gov/circulars/42336. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40411] GRB 251017A: Glowbug gamma-ray detection
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42335 SUBJECT: GRB 251017A: Glowbug gamma-ray detection DATE: 25/10/17 21:06:38 GMT FROM: richard.s.woolf.civ(a)us.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 251017A, which was also detected by Swift/BAT (GCN 42322). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-17 08:40:42.816 with a duration of 8.2 s and a total significance of about 11.9 sigma. The light curve comprises two primary peaks. 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/42335. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40410] GRB 251013C: Liverpool Telescope observations
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42334 SUBJECT: GRB 251013C: Liverpool Telescope observations DATE: 25/10/17 21:03:54 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek and D. A. Perley (LJMU) report: We observed the field of GRB 251013C (Fermi GBM team, GCN 42221; Rakotondrainibe et al., GCN 42222) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 60s exposures in the SDSS ugriz filters, starting on 2025-10-14 01:46:49, about 8.1h after Fermi trigger. We report detections in all bands, at the position of the optical afterglow first reported by Palmerio et al., GCN 42223: MJD (start) T_mid-T_0 Filter Mag. (AB) 60962.07711 8.20 h u 19.07 ± 0.10 60962.07418 8.13 h g 18.62 ± 0.04 60962.07517 8.15 h r 18.36 ± 0.02 60962.07614 8.17 h i 18.14 ± 0.03 60962.07877 8.24 h z 18.00 ± 0.03 The photometry for griz filters was calibrated using nearby PanSTARRS secondary standards, while u-band photometry was calibrated using the SDSS catalogue. The photometry is not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42334. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40409] GRB 251013C: Leavitt Observatory optical photometry
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42333 SUBJECT: GRB 251013C: Leavitt Observatory optical photometry DATE: 25/10/17 20:56:44 GMT FROM: leavittob(a)gmail.com E. Pavoni, L. Moretti (Leavitt Observatory, Italy) Members of: GRB/UAI - Gamma Ray Burst Section of Unione Astrofili Italiani 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 performed a follow-up observation of the field of GRB 251013C (Fermi GBM team, GCN 42221; Rakotondrainibe et al., GCN 42222) using our 250mm f/8 Ritchey-Chrétien telescope (Leavitt Observatory, Manciano, Italy). Observations began on 2025-10-13 at 19:09:11 UT (≈ 1.5 hours after the trigger) and ended at 22:19:55 UT. A series of images in Rc and Ic filter (Johnson-Cousins system) was obtained under good weather conditions. We clearly detected a bright afterglow positionally consistent with the source reported in previous circulars. The OT coordinates are: RA (J2000) = 23:03:20.55 Dec(J2000) = -00:12:35.12 (±2 arcsec on both axes) Photometry was performed using nearby stars from the Pan-STARRS catalog (magnitudes converted using Lupton (2005) equations) and analysed with AstroImageJ (2017AJ....153...77C). The following magnitudes were measured (not corrected for Galactic extinction): HJD at mid-exposure Filter Mag. Mag. err. 2460962.30386029 Rc 15.38 0.01 2460962.30725948 Rc 15.51 0.01 2460962.30996796 Rc 15.67 0.01 2460962.31258558 Rc 15.73 0.02 2460962.31556121 Rc 15.74 0.02 2460962.31806558 Rc 15.76 0.02 2460962.32017580 Rc 15.86 0.02 2460962.32228375 Rc 15.84 0.02 2460962.32439216 Rc 15.84 0.02 2460962.32650057 Rc 15.89 0.02 2460962.32860895 Rc 15.90 0.02 2460962.33071795 Rc 15.92 0.02 2460962.33282552 Rc 15.97 0.02 2460962.33493454 Rc 15.96 0.02 2460962.33704239 Rc 16.04 0.02 2460962.33915074 Rc 16.12 0.02 2460962.34126105 Rc 16.12 0.02 2460962.34337272 Rc 16.19 0.02 2460962.34548188 Rc 16.27 0.02 2460962.34759218 Rc 16.29 0.02 2460962.35500912 Rc 16.33 0.02 2460962.35926398 Rc 16.34 0.02 2460962.36351931 Rc 16.37 0.02 2460962.36777694 Rc 16.41 0.02 2460962.37203488 Rc 16.56 0.03 2460962.37629036 Rc 16.46 0.03 2460962.38920934 Rc 16.64 0.03 2460962.39346447 Rc 16.54 0.03 2460962.39772065 Rc 16.69 0.03 2460962.40623373 Rc 16.80 0.04 2460962.41049247 Rc 16.75 0.03 2460962.41474858 Rc 16.93 0.04 2460962.41900117 Rc 16.82 0.04 2460962.42325452 Rc 16.72 0.04 2460962.42750818 Rc 17.11 0.05 2460962.35287059 Ic 15.94 0.03 2460962.35712512 Ic 15.95 0.03 2460962.36138024 Ic 15.92 0.03 2460962.36563799 Ic 15.86 0.03 2460962.36989563 Ic 16.05 0.04 2460962.37415044 Ic 16.25 0.04 2460962.38706915 Ic 16.14 0.04 2460962.39132719 Ic 16.19 0.04 2460962.39558282 Ic 16.33 0.05 2460962.39983877 Ic 16.23 0.05 2460962.40409469 Ic 16.37 0.05 2460962.40835283 Ic 16.40 0.05 2460962.41261135 Ic 16.43 0.06 2460962.41686396 Ic 16.24 0.05 2460962.42111700 Ic 16.42 0.06 2460962.42537095 Ic 16.49 0.06 2460962.42997457 Ic 16.68 0.07 2460962.43422909 Ic 16.63 0.07 This message may be cited. Reference: https://leavittobservatory.altervista.org View this GCN Circular online at https://gcn.nasa.gov/circulars/42333. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40408] Fermi GRB 251016B: Global MASTER-Net observations report
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42332 SUBJECT: Fermi GRB 251016B: Global MASTER-Net observations report DATE: 25/10/17 20:01:03 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 251016B ( Fermi GBM team, GCN 42316) errorbox 64428 sec after notice time and 64463 sec after trigger time at 2025-10-17 17:53:24 UT, with upper limit up to 18.4 mag. The observations began at zenith distance = 75 deg. The sun altitude is -38.0 deg. The galactic latitude b = 57 deg., longitude l = 131 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3016439 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 64493 | 2025-10-17 17:53:24 | MASTER-Kislovodsk | (12h 10m 29.71s , +59d 47m 44.4s) | C | 60 | 17.9 | 64493 | 2025-10-17 17:53:24 | MASTER-Kislovodsk | (12h 02m 34.87s , +60d 07m 45.3s) | C | 60 | 18.2 | 64573 | 2025-10-17 17:54:44 | MASTER-Kislovodsk | (11h 59m 57.83s , +57d 53m 49.9s) | C | 60 | 17.7 | 64653 | 2025-10-17 17:56:03 | MASTER-Kislovodsk | (12h 28m 38.77s , +57d 56m 06.7s) | C | 60 | 17.7 | 64653 | 2025-10-17 17:56:03 | MASTER-Kislovodsk | (12h 21m 10.62s , +58d 16m 11.0s) | C | 60 | 17.9 | 64733 | 2025-10-17 17:57:23 | MASTER-Kislovodsk | (12h 23m 18.88s , +61d 41m 55.2s) | C | 60 | 17.6 | 64733 | 2025-10-17 17:57:23 | MASTER-Kislovodsk | (12h 14m 53.21s , +62d 01m 54.8s) | C | 60 | 18.2 | 64976 | 2025-10-17 18:01:26 | MASTER-Kislovodsk | (12h 32m 54.86s , +60d 10m 17.7s) | C | 60 | 18.2 | 65135 | 2025-10-17 18:04:06 | MASTER-Kislovodsk | (12h 10m 31.27s , +59d 47m 15.5s) | C | 60 | 17.9 | 65135 | 2025-10-17 18:04:06 | MASTER-Kislovodsk | (12h 02m 38.29s , +60d 07m 24.6s) | C | 60 | 18.4 | 65216 | 2025-10-17 18:05:26 | MASTER-Kislovodsk | (12h 00m 00.77s , +57d 53m 08.9s) | C | 60 | 17.6 | 65296 | 2025-10-17 18:06:46 | MASTER-Kislovodsk | (12h 28m 41.30s , +57d 55m 38.0s) | C | 60 | 17.6 | 65296 | 2025-10-17 18:06:46 | MASTER-Kislovodsk | (12h 21m 14.36s , +58d 15m 48.0s) | C | 60 | 18.0 | 65781 | 2025-10-17 18:14:51 | MASTER-Kislovodsk | (12h 23m 20.47s , +61d 42m 21.0s) | C | 60 | 17.6 | 65781 | 2025-10-17 18:14:52 | MASTER-Kislovodsk | (12h 14m 56.78s , +62d 02m 32.5s) | C | 60 | 18.1 | 66021 | 2025-10-17 18:18:52 | MASTER-Kislovodsk | (12h 33m 02.17s , +60d 07m 57.4s) | C | 60 | 18.1 | 66181 | 2025-10-17 18:21:31 | MASTER-Kislovodsk | (12h 10m 40.13s , +59d 48m 37.0s) | C | 60 | 17.9 | 66181 | 2025-10-17 18:21:31 | MASTER-Kislovodsk | (12h 02m 49.68s , +60d 08m 56.5s) | C | 60 | 18.3 | 66261 | 2025-10-17 18:22:51 | MASTER-Kislovodsk | (12h 00m 02.22s , +57d 53m 04.0s) | C | 60 | 17.6 | 66341 | 2025-10-17 18:24:11 | MASTER-Kislovodsk | (12h 28m 46.58s , +57d 54m 54.8s) | C | 60 | 17.6 | 66341 | 2025-10-17 18:24:12 | MASTER-Kislovodsk | (12h 21m 22.73s , +58d 15m 14.6s) | C | 60 | 17.9 | 66632 | 2025-10-17 18:29:02 | MASTER-Kislovodsk | (12h 23m 25.23s , +61d 42m 58.9s) | C | 60 | 17.7 | 66632 | 2025-10-17 18:29:02 | MASTER-Kislovodsk | (12h 15m 03.72s , +62d 03m 15.8s) | C | 60 | 18.1 | 67078 | 2025-10-17 18:36:28 | MASTER-Kislovodsk | (12h 33m 12.10s , +60d 09m 22.3s) | C | 60 | 18.1 | 67237 | 2025-10-17 18:39:07 | MASTER-Kislovodsk | (12h 10m 48.06s , +59d 48m 19.7s) | C | 60 | 17.9 | 67237 | 2025-10-17 18:39:08 | MASTER-Kislovodsk | (12h 02m 58.20s , +60d 08m 43.5s) | C | 60 | 18.1 | 67317 | 2025-10-17 18:40:27 | MASTER-Kislovodsk | (12h 00m 05.23s , +57d 53m 23.6s) | C | 60 | 17.6 | 67397 | 2025-10-17 18:41:47 | MASTER-Kislovodsk | (12h 28m 47.12s , +57d 54m 50.5s) | C | 60 | 17.6 | 67397 | 2025-10-17 18:41:47 | MASTER-Kislovodsk | (12h 21m 23.71s , +58d 15m 15.1s) | C | 60 | 18.0 | 67687 | 2025-10-17 18:46:37 | MASTER-Kislovodsk | (12h 23m 27.68s , +61d 40m 36.8s) | C | 60 | 17.6 | 67687 | 2025-10-17 18:46:37 | MASTER-Kislovodsk | (12h 15m 10.60s , +62d 00m 56.4s) | C | 60 | 18.1 | 67926 | 2025-10-17 18:50:37 | MASTER-Kislovodsk | (12h 33m 18.29s , +60d 07m 34.3s) | C | 60 | 18.1 | 68293 | 2025-10-17 18:56:43 | MASTER-Kislovodsk | (12h 10m 54.87s , +59d 48m 17.3s) | C | 60 | 17.9 | 68293 | 2025-10-17 18:56:43 | MASTER-Kislovodsk | (12h 02m 59.73s , +60d 08m 46.1s) | C | 60 | 18.2 | 68373 | 2025-10-17 18:58:03 | MASTER-Kislovodsk | (12h 00m 24.20s , +57d 53m 11.7s) | C | 60 | 17.6 | 68452 | 2025-10-17 18:59:23 | MASTER-Kislovodsk | (12h 28m 56.85s , +57d 52m 31.8s) | C | 60 | 17.6 | 68453 | 2025-10-17 18:59:23 | MASTER-Kislovodsk | (12h 21m 29.31s , +58d 13m 01.5s) | C | 60 | 17.9 | 68753 | 2025-10-17 19:04:23 | MASTER-Kislovodsk | (12h 23m 37.61s , +61d 41m 55.7s) | C | 60 | 17.6 | 68754 | 2025-10-17 19:04:24 | MASTER-Kislovodsk | (12h 15m 21.05s , +62d 02m 17.0s) | C | 60 | 18.1 | 68994 | 2025-10-17 19:08:25 | MASTER-Kislovodsk | (12h 33m 21.64s , +60d 08m 01.0s) | C | 60 | 18.1 | 69157 | 2025-10-17 19:11:08 | MASTER-Kislovodsk | (12h 10m 49.35s , +59d 47m 14.2s) | C | 60 | 17.6 | 69157 | 2025-10-17 19:11:08 | MASTER-Kislovodsk | (12h 03m 11.06s , +60d 07m 42.8s) | C | 60 | 18.2 | 69445 | 2025-10-17 19:15:56 | MASTER-Kislovodsk | (12h 00m 15.93s , +57d 52m 23.4s) | C | 60 | 17.6 | 69525 | 2025-10-17 19:17:15 | MASTER-Kislovodsk | (12h 28m 54.84s , +57d 54m 20.9s) | C | 60 | 17.5 | 69525 | 2025-10-17 19:17:15 | MASTER-Kislovodsk | (12h 21m 39.39s , +58d 14m 53.4s) | C | 60 | 18.1 | 69815 | 2025-10-17 19:22:05 | MASTER-Kislovodsk | (12h 23m 48.31s , +61d 42m 05.7s) | C | 60 | 17.6 | 69815 | 2025-10-17 19:22:05 | MASTER-Kislovodsk | (12h 15m 32.13s , +62d 02m 32.5s) | C | 60 | 18.0 | 69975 | 2025-10-17 19:24:45 | MASTER-Kislovodsk | (11h 58m 36.13s , +61d 27m 27.6s) | C | 60 | 17.9 | 70055 | 2025-10-17 19:26:05 | MASTER-Kislovodsk | (12h 33m 35.77s , +60d 07m 51.8s) | C | 60 | 17.9 | 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/42332. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40407] GRB 251017A: JinShan observations of the optical afterglow
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42331 SUBJECT: GRB 251017A: JinShan observations of the optical afterglow DATE: 25/10/17 18:35:37 GMT FROM: syfu(a)nao.cas.cn S.Y. Fu (HUST), L.B. He, X. Liu, J. An, S.Q. Jiang, Z.P. Zhu, D. Xu (NAOC), 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 Swift GRB 251017A (Gupta et al., GCN 42322) using the 100C telescope of the JinShan project, located at Altay, Xinjiang, China. Observations started at 2025-10-17 12:50:19.42 UT, i.e., 4.16 hours after the trigger, and a series of 300s frames in r and z bands were obtained. The previously reported optical afterglow (Perez-Garcia et al., GCN 42323; Antier et al., GCN 42325; Sasada et al., GCN 42329) was clearly detected in our images with r-band magnitude r = 21.17 +- 0.06, calibrated with nearby Pan-STARRS1 DR2 catalog and without the Galactic extinction correction. 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/42331. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40406] Swift GRB 251017A: Global MASTER-Net observations report
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42330 SUBJECT: Swift GRB 251017A: Global MASTER-Net observations report DATE: 25/10/17 16:16:40 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 251017A ( R. Gupta et al., GCN 42322) errorbox 26422 sec after notice time and 26441 sec after trigger time at 2025-10-17 16:01:26 UT, with upper limit up to 17.9 mag. The observations began at zenith distance = 43 deg. The sun altitude is -18.3 deg. The galactic latitude b = -40 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=3016699 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 26532 | MASTER-Kislovodsk | C | 180 | 12.8 | 26532 | MASTER-Kislovodsk | C | 180 | 17.9 | 26731 | MASTER-Kislovodsk | C | 180 | 13.4 | 26732 | MASTER-Kislovodsk | C | 180 | 17.9 | 26931 | MASTER-Kislovodsk | C | 180 | 13.0 | 26932 | MASTER-Kislovodsk | C | 180 | 17.9 | 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/42330. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40405] GRB 251017A : MITSuME Akeno optical afterglow candidate detection
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42329 SUBJECT: GRB 251017A : MITSuME Akeno optical afterglow candidate detection DATE: 25/10/17 16:06:04 GMT FROM: Mahito Sasada at Tokyo Institute of Technology <sasada(a)hp.phys.titech.ac.jp> M. Sasada, A. Ochi, R. Kato, Y. Kubo, H. Hagio, H. Seki, S. Joshima, I. Takahashi, Y. Yatsu and N. Kawai (Science Tokyo) report on behalf of the MITSuME collaboration: We observed the field of GRB 251017A detected by Swift/BAT (Gupta et al. GCN 42322) with the optical three-color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50-cm telescope Akeno. The observation started at 2025-10-17 08:41:53 UT (69 seconds after the Swift/BAT trigger). We stacked the images with good conditions. We detected a point source in the Ic-band image at a position of the reported optical candidate (Gupta et al. GCN 42322; Perez-Garcia et al. GCN 42323; Antier et al. GCN 42325). Here we report the magnitude of the source as follows. T0+[sec] | MID-UT | T-EXP[sec] | magnitude ------------------------------------------------------------------------------------------------ 9256 | 2025-10-17 11:15:00 | 11520 | Ic=19.7+/-0.2 ------------------------------------------------------------------------------------------------ T0+ : Elapsed time after the trigger T-EXP: Total Exposure time We used the PS1 catalog for flux calibration. The catalog magnitudes in PS1 g, r and i bands were converted to our g', Rc and Ic band magnitudes following Tonry et al. (2012), Table 6. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ; https://github.com/MNiwano/Eclaire) View this GCN Circular online at https://gcn.nasa.gov/circulars/42329. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[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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[vsnet-grb-info 40394] GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42318 SUBJECT: GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart DATE: 25/10/17 04:28:39 GMT FROM: enriquemm(a)astro.unam.mx Enrique Moreno Méndez (UNAM), Sarah Antier (OCA), Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Noémie Globus (UNAM), Ny Avo Rakotondrainibe (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Camila Angulo (UNAM), 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), 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 observed from 2025-10-16 03:10 to 08:29 (57.51 to 62.83 hours after the trigger), obtaining 120 minutes of exposure in the r filter, and from 2025-10-17T03:17 to 03:28 UTC (81.64 to 81.98 hours after the trigger), obtaining 9 minutes of exposure in the r filter. 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 detect 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; López-Cámara 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; Globus et al., GCN Circ. 42279; Abidkhanov et al., GCN Circ. 42283; and Leonini et al., GCN Circ. 42301). Between our two epochs, the optical counterpart shows a rebrightening of Delta r = 0.97 +/- 0.05. Our observations show a strong and late rebrightening. 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/42318. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40393] GRB 251007B: Swift-BAT refined analysis
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42317 SUBJECT: GRB 251007B: Swift-BAT refined analysis DATE: 25/10/17 01:39:20 GMT FROM: Takanori Sakamoto at AGU <tsakamoto(a)phys.aoyama.ac.jp> C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), A. Melandri (INAF-OAR), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Because BAT triggered GRB 251007B (trigger #1402467) (Melandri, et al.GCN Circ. 42147) six minutes after GRB 251007A (Ambrosi, et al. GCN Circ. 42146), no BAT event data was generated on-board. Therefore, it is difficult to provide a detailed prompt emission analysis. According to the 1 s rate data (15-350 keV), the burst shows a double-peaked structure with a duration of ~25 sec. View this GCN Circular online at https://gcn.nasa.gov/circulars/42317. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40392] GRB 251007B: Swift-BAT refined analysis
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42317 SUBJECT: GRB 251007B: Swift-BAT refined analysis DATE: 25/10/17 01:39:20 GMT FROM: Takanori Sakamoto at AGU <tsakamoto(a)phys.aoyama.ac.jp> C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), A. Melandri (INAF-OAR), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Because BAT triggered GRB 251007B (trigger #1402467) (Melandri, et al.GCN Circ. 42147) six minutes after GRB 251007A (Ambrosi, et al. GCN Circ. 42146), no BAT event data was generated on-board. Therefore, it is difficult to provide a detailed prompt emission analysis. According to the 1 s rate data (15-350 keV), the burst shows a double-peaked structure with a duration of ~25 sec. View this GCN Circular online at https://gcn.nasa.gov/circulars/42317. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40391] GRB 251016B: Fermi GBM Final Real-time Localization
by GCN Circulars 17 Oct '25

17 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42316 SUBJECT: GRB 251016B: Fermi GBM Final Real-time Localization DATE: 25/10/17 00:10:30 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 23:59:00 UT on 16 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251016B (trigger 782351945.722452 / 251016999). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 183.6, Dec = 59.6 (J2000 degrees, equivalent to J2000 12h 14m, 59d 36'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 46.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251016999/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251016999/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251016999/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42316. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40390] GRB 251014D: Swift-BAT refined analysis
by GCN Circulars 16 Oct '25

16 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42315 SUBJECT: GRB 251014D: Swift-BAT refined analysis DATE: 25/10/16 23:04:28 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> D. M. Palmer (LANL), S. D. Barthelmy (GSFC), R. Gupta (GSFC), N. J. Klingler (GSFC/UMBC/CRESSTII) H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 251014D (trigger #1404126) (Klingler, et al., GCN Circ. 42274). The BAT ground-calculated position is RA, Dec = 323.933, -41.873 deg which is RA(J2000) = 21h 35m 43.9s Dec(J2000) = -41d 52' 23.0" with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 49%. The mask-weighted BAT light curve shows a main emission followed by weaker emission. T90 (15-350 keV) is 286.98 +- 70.09 sec (estimated error including systematics). The time-averaged spectrum from T+0.39 to T+310.10 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.74 +- 0.38. The fluence in the 15-150 keV band is 1.0 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+5.18 sec in the 15-150 keV band is 0.5 +- 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/1404126 View this GCN Circular online at https://gcn.nasa.gov/circulars/42315. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40389] GRB 251016A: BOOTES-6/DPRT optical upper limit
by GCN Circulars 16 Oct '25

16 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42314 SUBJECT: GRB 251016A: BOOTES-6/DPRT optical upper limit DATE: 25/10/16 21:13:12 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es> I. Perez-Garcia, E. Fernandez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S.-Y. Wu, 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), M. Jelinek (ASU-CAS), A. Kumar (ARIES) and C. J. Perez del Pulgar (UMA, Malaga), on behalf of a larger collaboration, report: Following the detection of GRB 251016A by Fermi/GBM (Smith et al., GCN 42309) and SVOM/ECLAIRs (Basa et al., GCN 42308), the BOOTES-6/DPRT 0.6m robotic telescope at Boyden Observatory in Maselspoort (South Africa) responded to this event starting on Oct 16, 17:35 UT (~ 2.6 h after trigger) with 60s images. No new source is detected within the Swift/XRT X-ray afterglow Source 1 position (Evans et al., GCN 42311) up to magnitude 17.14 using Gaia DR3 Gmag magnitude as reference on our first image. Further images were gathered and using ATLAS REFCAT2 as reference (Tonry et al. 2018) we get an upper limit of: | UT mid exposure | Mag limit | Filter | Exp time (sec) | | ------------------- | --------- | ------ | -------------- | | 2025-10-16 18:05:07 | 19.3 | clear | 60x7 | | 2025-10-16 18:37:07 | 17.6 | Z | 60x4 | | 2025-10-16 18:43:02 | 19.1 | g | 60x4 | | 2025-10-16 19:05:30 | 18.7 | r | 60x3 | | 2025-10-16 19:10:38 | 18.3 | i | 60x4 | We thank the staff at Boyden Observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/42314. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40388] GRB 251016A: Glowbug gamma-ray detection of a short burst
by GCN Circulars 16 Oct '25

16 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42313 SUBJECT: GRB 251016A: Glowbug gamma-ray detection of a short burst DATE: 25/10/16 21:06:59 GMT FROM: richard.s.woolf.civ(a)us.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 251016A, which was also detected by SVOM/ECLAIRs (GCN 42308), Fermi/GBM (GCN 42309), and CALET (Trigger 1444661491). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-16 14:59:18.560 with a duration of 0.64 s and a total significance of about 76 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/42313. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40387] GRB 251013C: VLA detection
by GCN Circulars 16 Oct '25

16 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42312 SUBJECT: GRB 251013C: VLA detection DATE: 25/10/16 20:08:06 GMT FROM: collinchristy(a)arizona.edu C. Christy (University of Arizona), T. Laskar (University of Utah), N. Franz (University of Arizona), 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 Karl G. Jansky Very Large Array (VLA) at multiple frequencies beginning on 2025 October 15 at 02:15 UT (1.36 days after the burst). In our preliminary analysis, we detect the radio counterpart (Laskar et al., GCN 42243; Rhodes et al., GCN 42294) at 10 GHz with a flux density of 0.111 +/- 0.012 mJy at the position: RA (J2000) = 23:03:20.56 +/- 0.03” Dec (J2000) = -0:12:37.22 +/- 0.03” This is consistent with the X-ray position (Rakotondrainibe et al., GCN 42222; Evans et al., GCN 42232), optical position (Palmerio et al., GCN 42223; Masi et al., GCN 42228), and radio position (Laskar et al., GCN 42243; Rhodes et al., GCN 42294). Further observations are planned. We thank the VLA staff for scheduling and executing these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42312. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40386] sb25101602: Swift-XRT counterpart detection
by GCN Circulars 16 Oct '25

16 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42311 SUBJECT: sb25101602: Swift-XRT counterpart detection DATE: 25/10/16 20:00:35 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 GRB251016A (sb25101602), collecting 749 s of Photon Counting (PC) mode data between T0+6.6 ks and T0+7.4 ks after the trigger. A likely counterpart has been found. The details of this source are: Source 1 (SWIFT J174512.5-393337): ================================== RA (J2000.0): 266.3024 = 17 45 12.58 Dec (J2000.0): -39.5606 = -39 33 38.2 Error: 4.6 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 4.5 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.057 +/- 0.011 ct s^-1 Mean flux: (3.41 +/- 0.64)e-12 erg cm^-2 s^-1 Peak rate: 0.072 +/- 0.019 ct s^-1 Peak flux: (4.4 +/- 1.1)e-12 erg cm^-2 s^-1 ECF: 6.02e-11 erg cm^-2 ct^-1 assuming NH=7.85e+21 cm^-2, gamma=1.55 determined from a spectral fit. XMM UL: 6.5e-13 erg cm^-2 s^-1, (0.3-10 keV) so the source is 3.2-sigma above this 3-sigma upper limit. The source may be fading, at the 1.1-sigma level. There are 2 2MASS objects within the source's 3-sigma error radius. We have detected a total of 9 sources. These have been automatically classified as follows: * 1 likely counterpart * 0 candidate counterparts * 8 uncatalogued X-ray sources * 0 known X-ray sources Uncatalogued X-ray sources -------------------------- Source 2 (SWIFT J174439.5-394550): ================================== RA (J2000.0): 266.1646 = 17 44 39.50 Dec (J2000.0): -39.7642 = -39 45 51.1 Error: 6.1 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 11.4 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0300 [+0.0096, -0.0079] ct s^-1 Mean flux: (1.29 [+0.41, -0.34])e-12 erg cm^-2 s^-1 Peak rate: 0.0300 [+0.0096, -0.0079] ct s^-1 Peak flux: (1.29 [+0.41, -0.34])e-12 erg cm^-2 s^-1 XMM UL: 7.9e-13 erg cm^-2 s^-1, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. There are 5 2MASS objects within the source's 3-sigma error radius. Source 3 (SWIFT J174431.8-393913): ================================== RA (J2000.0): 266.1326 = 17 44 31.82 Dec (J2000.0): -39.6537 = -39 39 13.3 Error: 5.9 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 5.7 arcmin from the SVOM/ECLAIRs position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-4.3 +/- -4.3)e-11 erg cm^-2 s^-1 Peak rate: 0.0123 [+0.0069, -0.0053] ct s^-1 Peak flux: (5.3 [+2.9, -2.3])e-13 erg cm^-2 s^-1 XMM UL: 1.3e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. There are 5 2MASS objects within the source's 3-sigma error radius. Source 4 (SWIFT J174456.1-392739): ================================== RA (J2000.0): 266.2340 = 17 44 56.16 Dec (J2000.0): -39.4609 = -39 27 39.2 Error: 14.0 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 7.1 arcmin from the SVOM/ECLAIRs position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-3.5 +/- -3.5)e-9 erg cm^-2 s^-1 Peak rate: (6.3 [+5.6, -4.0])e-3 ct s^-1 Peak flux: (2.2 [+1.9, -1.4])e-11 erg cm^-2 s^-1 ECF: 3.48e-09 erg cm^-2 ct^-1 assuming NH=3.52e+22 cm^-2, gamma=5.05 determined from a spectral fit. XMM UL: 1.0e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is 1.3-sigma above this 3-sigma upper limit. There is no evidence for fading. There are 34 2MASS objects within the source's 3-sigma error radius. Source 5 (SWIFT J174354.6-392827): ================================== RA (J2000.0): 265.9777 = 17 43 54.65 Dec (J2000.0): -39.4743 = -39 28 27.5 Error: 9.8 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 12.2 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0128 [+0.0066, -0.0050] ct s^-1 Mean flux: (5.5 [+2.8, -2.1])e-13 erg cm^-2 s^-1 Peak rate: 0.0128 [+0.0066, -0.0050] ct s^-1 Peak flux: (5.5 [+2.8, -2.1])e-13 erg cm^-2 s^-1 XMM UL: 7.2e-13 erg cm^-2 s^-1, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. There are 22 2MASS objects within the source's 3-sigma error radius. Source 6 (SWIFT J174500.5-394402): ================================== RA (J2000.0): 266.2523 = 17 45 00.55 Dec (J2000.0): -39.7341 = -39 44 02.8 Error: 11.1 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 9.7 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0156 [+0.0070, -0.0055] ct s^-1 Mean flux: (6.7 [+3.0, -2.4])e-13 erg cm^-2 s^-1 Peak rate: 0.0156 [+0.0070, -0.0055] ct s^-1 Peak flux: (6.7 [+3.0, -2.4])e-13 erg cm^-2 s^-1 XMM UL: 1.3e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. There are 18 2MASS objects within the source's 3-sigma error radius. Source 7 (SWIFT J174411.2-392428): ================================== RA (J2000.0): 266.0470 = 17 44 11.28 Dec (J2000.0): -39.4079 = -39 24 28.4 Error: 13.9 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 12.5 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0167 [+0.0073, -0.0057] ct s^-1 Mean flux: (7.2 [+3.2, -2.4])e-13 erg cm^-2 s^-1 Peak rate: 0.0167 [+0.0073, -0.0057] ct s^-1 Peak flux: (7.2 [+3.2, -2.4])e-13 erg cm^-2 s^-1 XMM UL: 1.1e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `OGLE BLG-DSCT-13120' is 43.9" away. There are 33 2MASS objects within the source's 3-sigma error radius. Source 8 (SWIFT J174427.1-393500): ================================== RA (J2000.0): 266.1131 = 17 44 27.14 Dec (J2000.0): -39.5835 = -39 35 00.6 Error: 11.9 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 4.3 arcmin from the SVOM/ECLAIRs position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-4.3 +/- -4.3)e-11 erg cm^-2 s^-1 Peak rate: (8.7 [+6.1, -4.5])e-3 ct s^-1 Peak flux: (3.7 [+2.6, -1.9])e-13 erg cm^-2 s^-1 XMM UL: 6.6e-13 erg cm^-2 s^-1, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. There are 28 2MASS objects within the source's 3-sigma error radius. Source 9 (SWIFT J174502.9-392734): ================================== RA (J2000.0): 266.2622 = 17 45 02.93 Dec (J2000.0): -39.4596 = -39 27 34.6 Error: 8.8 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 7.5 arcmin from the SVOM/ECLAIRs position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-4.3 +/- -4.3)e-11 erg cm^-2 s^-1 Peak rate: (8.9 [+6.4, -4.7])e-3 ct s^-1 Peak flux: (3.8 [+2.7, -2.0])e-13 erg cm^-2 s^-1 XMM UL: 7.1e-13 erg cm^-2 s^-1, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. There are 11 2MASS objects within the source's 3-sigma error radius. 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_FIELD00042. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42311. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40385] Fermi GRB 251016A: Global MASTER-Net observations report
by GCN Circulars 16 Oct '25

16 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42310 SUBJECT: Fermi GRB 251016A: Global MASTER-Net observations report DATE: 25/10/16 19:00:45 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 251016A ( Fermi GBM team, GCN 42309) errorbox 9753 sec after notice time and 9784 sec after trigger time at 2025-10-16 17:42:24 UT, with upper limit up to 16.8 mag. Observations started at twilight. The observations began at zenith distance = 38 deg. The sun altitude is -11.4 deg. The galactic latitude b = -12 deg., longitude l = 344 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3016116 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 9814 | 2025-10-16 17:42:24 | MASTER-SAAO | (17h 41m 59.48s , -48d 04m 09.1s) | C | 60 | 14.4 | 9814 | 2025-10-16 17:42:24 | MASTER-SAAO | (17h 44m 44.95s , -48d 19m 26.1s) | C | 60 | 16.5 | 9909 | 2025-10-16 17:43:58 | MASTER-SAAO | (17h 39m 01.22s , -50d 11m 14.5s) | C | 60 | 16.8 | 9909 | 2025-10-16 17:43:58 | MASTER-SAAO | (17h 36m 07.40s , -49d 55m 40.2s) | C | 60 | 15.2 | 10004 | 2025-10-16 17:45:33 | MASTER-SAAO | (17h 48m 32.79s , -46d 10m 37.6s) | C | 60 | 14.6 | 10004 | 2025-10-16 17:45:33 | MASTER-SAAO | (17h 51m 12.71s , -46d 25m 54.6s) | C | 60 | 16.6 | 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/42310. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40384] GRB 251016A: Fermi GBM Final Localization
by GCN Circulars 16 Oct '25

16 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42309 SUBJECT: GRB 251016A: Fermi GBM Final Localization DATE: 25/10/16 15:46:56 GMT FROM: Jacob Smith at Fermi-GBM Team <jrs0118(a)uah.edu> The Fermi GBM team reports the detection of a likely SHORT GRB "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). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 268.93, Dec = -48.82 (J2000 degrees, equivalent to J2000 17h 55m, -48d 49'), with a statistical uncertainty of 3.55 degrees. The angle from the Fermi LAT boresight is 33 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251016625/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251016625/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251016625/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/42309. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40383] GRB 251016A: SVOM detection of a short burst
by GCN Circulars 16 Oct '25

16 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42308 SUBJECT: GRB 251016A: SVOM detection of a short burst DATE: 25/10/16 15:30:00 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> S. Basa, S. Boissier (LAM), O. Godet, S. Guillot (IRAP), D. Turpin (CEA) At 2025-10-16T14:59:20 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251016A (SVOM burst-id sb25101602). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Count-Rate Trigger (CRT), which produced a sequence of 5 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 8.16 in the [8-120] keV energy band over a time window of 0.60 seconds starting at 2025-10-16T14:59:19. The localization of the best alert is R.A., Dec. 266.207, -39.577 degrees: R.A. (J2000) = 17h44m49.58s Dec. (J2000) = -39d34m35.95s with a 90% confidence level (C.L.) radius of 9.64 arcmin (including systematic error of 2 arcmin added in quadrature). The SVOM/ECLAIRs light curve showed a single and narrow peak. This burst also triggered SVOM/GRM at 2025-10-16T14:59:19 on a timescale of 0.10 seconds with an SNR of 37.30. This burst seems to have been detected by Fermi, but with a declination of about 10 degrees offset. The satellite did not slew due to Sun constraint. No X-ray observation could be performed by SVOM/MXT for the time being. No optical observation could be performed by SVOM/VT for the time being. 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 Stephane Basa: stephane.basa(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/42308. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40382] GRB 251014A: Swift-XRT observations
by GCN Circulars 16 Oct '25

16 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42307 SUBJECT: GRB 251014A: Swift-XRT observations DATE: 25/10/16 13:51:56 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), S. Lanava (PSU), J.P. Osborne (U. Leicester) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: We have analysed 6.2 ks of Photon Counting (PC) mode XRT data for GRB 251014A, collected between T0+101.1 ks and T0+174.7 ks. Three uncatalogued X-ray sources have been detected within the estimated 3-sigma Swift-BAT error region (296 arcsec), however none of them is above the RASS limit or shows definitive signs of fading. Therefore, at the present time we cannot identify which, if any, is the afterglow. Details of these sources are given below: Source 5: RA (J2000.0): 111.7316 = 07h 26m 55.58s Dec (J2000.0): +6.4150 = +06d 24' 53.9" Error: 6.7 arcsec (radius, 90% conf.) Count-rate: (2.33 [+0.88, -0.72])e-3 ct s^-1 Distance: 1 arcsec from Swift-BAT position. Flux: (1.11 [+0.42, -0.34])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 8: RA (J2000.0): 111.6918 = 07h 26m 46.04s Dec (J2000.0): +6.4252 = +06d 25' 30.7" Error: 6.1 arcsec (radius, 90% conf.) Count-rate: (2.25 [+0.88, -0.72])e-3 ct s^-1 Distance: 148 arcsec from Swift-BAT position. Flux: (7.1 [+2.8, -2.3])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 9: RA (J2000.0): 111.7868 = 07h 27m 08.82s Dec (J2000.0): +6.3731 = +06d 22' 23.3" Error: 5.6 arcsec (radius, 90% conf.) Count-rate: (1.42 [+0.73, -0.56])e-3 ct s^-1 Distance: 247 arcsec from Swift-BAT position. Flux: (4.8 [+2.5, -1.9])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV) Seven uncatalogued sources were also detected too far from the GRB position to be likely afterglow candidates. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/01403878. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42307. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40381] LIGO/Virgo/KAGRA S251014cn: Updated Sky localization
by GCN Circulars 16 Oct '25

16 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42306 SUBJECT: LIGO/Virgo/KAGRA S251014cn: Updated Sky localization DATE: 25/10/16 07:51:43 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) and LIGO Livingston Observatory (L1) data around the time of the compact binary merger (CBC) candidate S251014cn (GCN Circular 42255. 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/S251014cn For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 172 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 607 +/- 164 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/42306. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40380] GRB 251014B: PRIME J-band upper limit
by GCN Circulars 16 Oct '25

16 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42305 SUBJECT: GRB 251014B: PRIME J-band upper limit DATE: 25/10/16 00:42:42 GMT FROM: N. Passaleva at Sapienza University of Rome <niccolo.passaleva(a)uniroma1.it> J. Durbak (UMD), N. Passaleva (U Rome), O. Guiffreda (UMD), M. El Kabir (U Rome), E. Troja (U Rome), A. S. Kutyrev (NASA/GSFC), S. B. Cenko (NASA/GSFC) Following the Swift/BAT-GUANO (Ronchini et al., GCN 42263) detection of Fermi/GBM-detected event, we observed the transient field in J filter with PRIME. Observations started ~16 hours after the initial Fermi trigger. Using VISTA Kilo-degree Infrared Galaxy (VIKING) Survey nearby stars for preliminary calibration we do not detect any uncatalogued source down to J>21 AB (3-sigma) not corrected for galactic extinction at the position of the candidates reported by Swift/XRT (Lanava et al. GCN 42289), confirming the optical non-detection reported by Yadav et al. (GCN 42287) 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/42305. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40379] Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42304 SUBJECT: Upper limits from a search for additional neutrino events in IceCube DATE: 25/10/15 23:27:15 GMT FROM: Yuhua Yao at IceCube/UW-Madison <yyao255(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-251014A (https://gcn.nasa.gov/circulars/42277) in a time range of 1000 seconds centered on the alert event time (2025-10-14 18:24:51.580 UTC to 2025-10-14 18:41:31.580 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-251014A. We report a p-value of 1.00 in this time window. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2dN/dE evaluated at 1 TeV, is 1.4e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251014A in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 3e+02 GeV and 1e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-10-13 18:33:11.580 UTC to 2025-10-15 18:33:11.580 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.6e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251014A in a 2 day time window. 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. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/42304. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40378] IceCube Alert 251014.77: Global MASTER-Net observations report
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42303 SUBJECT: IceCube Alert 251014.77: Global MASTER-Net observations report DATE: 25/10/15 22:39:32 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 IceCube Alert 251014.77 (trigger No 75492250,00h 11m 35.28s , +02d 54m 43.2s, R=0.51) errorbox 1 days 12049 sec after notice time and 1 days 12105 sec after trigger time at 2025-10-15 21:54:57 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 36 deg. The sun altitude is -48.7 deg. The galactic latitude b = -58 deg., longitude l = 105 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3014752 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 98536 | 2025-10-15 21:54:57 | MASTER-SAAO | (00h 08m 40.80s , +02d 48m 16.0s) | C | 60 | 19.4 | 98536 | 2025-10-15 21:54:57 | MASTER-SAAO | (00h 10m 29.80s , +02d 32m 25.7s) | 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/42303. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40377] Swift GRB251015.60: Global MASTER-Net observations report
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42302 SUBJECT: Swift GRB251015.60: Global MASTER-Net observations report DATE: 25/10/15 22:02:26 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 GRB251015.60 (trigger No 1404295,16h 20m 01.68s , -54d 51m 10.8s, R=0.05) errorbox 27211 sec after notice time and 27228 sec after trigger time at 2025-10-15 21:51:12 UT, with upper limit up to 16.1 mag. The observations began at zenith distance = 83 deg. The sun altitude is -48.5 deg. The galactic latitude b = -4 deg., longitude l = 330 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3015339 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 27319 | MASTER-SAAO | C | 180 | 15.1 | 27319 | MASTER-SAAO | C | 180 | 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/42302. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40376] GRB 251013C: Kilonova-Catcher optical afterglow detection
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42301 SUBJECT: GRB 251013C: Kilonova-Catcher optical afterglow detection DATE: 25/10/15 20:35:57 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> S. Leonini, M. Freeberg, R. Hellot (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (OCA/IJCLab), M. Coughlin (UMN), S. Karpov (FZU), P. Hello (IJCLAB), M. Pillas (IAP) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 251013C detected by Fermi/GBM (Fermi GBM team, GCN 42221), SVOM/ECLAIRs and GRM (Rakotondrainibe et al., GCN 42223) and AstroSat CZTI (Arya et al., GCN 42246) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the TEC180FL, iT32 and iT72 telescopes operated by M. Freeberg, the automated and remoted 0.53m Ritchey-Chretien telescope at Montarrenti Observatory (Siena, Italy, IAU code C88) operated by S. Leonini and a CDK17 telescope located at AITP San Pedro Chile Observatory operated by R. Hellot. Our observations started at TGRB+3.0hr and were taken with Clear, sdss gri and Rc Ic filters. In our stacked frames, subtracted from the PanSTARRS DR2 template image, we detect the optical counterpart firstly reported by SVOM/VT (Palmerio et al., GCN 42223) and later confirmed by many other teams. We report part of our follow-up results in the table below: +---------------+----------+------------+----------------+------------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+==========+============+================+==================+ | 3.18 | 30 x 30s | Rc (Vega) | 16.29 +/- 0.04 | Montarrenti Obs. | | 6.47 | 5 x 300s | Rc (Vega) | 17.63 +/- 0.02 | iT72 | | 8.26 | 6 x 300s | r (AB) | 18.24 +/- 0.05 | CDK17 AITP | +---------------+----------+------------+----------------+------------------+ All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the sloan filters were calibrated using the PanSTARRS DR1 catalog. Images obtained with the Johnson-cousins filters were calibrated using the GAIA DR3 synphot catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/) View this GCN Circular online at https://gcn.nasa.gov/circulars/42301. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40375] Fermi-LAT Gamma-ray Observations of IceCube-251014A
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42300 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-251014A DATE: 25/10/15 20:30:22 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC251014A neutrino event (GCN 42277) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 25-10-14 at 18:33:11.58 UTC (T0) with J2000 position RA = 2.81 (+0.48, -0.49) deg, Decl. = 2.91 (+0.49, -0.49 ) deg 90% PSF containment (J2000). No cataloged gamma-ray sources are found within the 90% IC251014A localization error (4FGL-DR4; The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC251014A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC251014A best-fit position, the >100 MeV flux upper limit (95% confidence) is <1.9e-10 ph cm^-2 s^-1 for ~17-years (2008-08-04 / T0), <1.6e-08 (<8.0e-07) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this analysis, the Fermi-LAT contact person is L. Pfeiffer (leonard.pfeiffer at uni-wuerzburg.de). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/42300. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40374] GRB 251013D: Swift/UVOT Observations
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42299 SUBJECT: GRB 251013D: Swift/UVOT Observations DATE: 25/10/15 20:20:03 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251013D 71 ks after the Fermi/GBM trigger (GCN Circ. 42224; DeLaunay et al., GCN Circ. 42244). We detect an uncatalogued optical source near the position of XRT source #2 (Burrows et al., GCN Circ. 42291). There is no evidence of fading in the UVOT data thus far. The preliminary UVOT position is: RA (J2000) = 03:07:52.73 = 46.96971 (deg.) Dec (J2000) = +08:48:57.4 = 8.81595 (deg.) with an estimated uncertainty of 0.42 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 71081 72734 1622 20.98+/-0.16 white 76655 78444 1758 20.78+/-0.13 white 82245 83695 1423 20.68+/-0.13 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.312 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42299. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40373] 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: EDIT: This circular was submitted as the result of a system error regarding the follow up ToO observation for this GRB. The correct URL for GRB 251013C products is https://www.swift.ac.uk/xrt_products/01404126 This circular is, nonetheless, 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 40372] 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 T0-2.0 to T0+53.2 s is best fit by a Comptonized function with Epeak = 129 +/- 12 keV, alpha = -0.9 +/- 0.1. A Band function fits equally well with Epeak = 103 +/- 16 and alpha = -0.8 +/- 0.2, and beta -2.3 +/- 0.2. 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 40371] GRB 251013C: Swift/UVOT Detection
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42298 SUBJECT: GRB 251013C: Swift/UVOT Detection DATE: 25/10/15 19:54:12 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251013C 0.4 ks after the Fermi/SVOM trigger (GCN Circ. 42221, Rakotondrainibe et al., GCN Circ. 42222). A bright source consistent with the XRT position (Evans et al., GCN Circ. 42232) and optical counterpart (Palmerio et al., GCN Circ. 42223, Perez-Garcia et al., GCN Circ. 42225; Konno et al., GCN Circ. 42226; Masi et al., GCN Circ. 42228; Moskvitin, GCN Circ. 42230; Gompertz et al., GCN Circ. 42231; Garnavich, GCN Circ. 42240; Watson et al., GCN Circ. 42241) is detected in the UVOT exposures. The preliminary UVOT position is: RA (J2000) = 23:03:20.55 = 345.83562 (deg.) Dec (J2000) = -00:12:36.9 = -0.21024 (deg.) with an estimated uncertainty of 0.42 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 u 480 5581 1785 15.22+/-0.03 white 129831 141519 2753 21.66+/-0.20 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.045 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42298. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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

15 Oct '25

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

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

15 Oct '25

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

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

15 Oct '25

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

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

15 Oct '25

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

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

15 Oct '25

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

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

15 Oct '25

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

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

15 Oct '25

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

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

15 Oct '25

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

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

15 Oct '25

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

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

15 Oct '25

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

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[vsnet-grb-info 40360] GRB 251014B: VLT/FORS2 Optical Observation
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42287 SUBJECT: GRB 251014B: VLT/FORS2 Optical Observation DATE: 25/10/15 13:01:17 GMT FROM: Roberto Ricci at INAF-IRA <ricci(a)ira.inaf.it> Muskan Yadav (U Rome), Yu-Han Yang (U Rome), Roberto Ricci (U Rome), Niccolò Passaleva (U Rome), Rosa Becerra (U Rome), Eleonora Troja (U Rome), Lei Hu (Upenn) report on behalf of the ERC BHianca team: We observed the Swift-BAT/GUANO (Ronchini et al., GCN 42263) field of GRB 251014B detected by Fermi-GBM (trigger number 782110046) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations started on Oct 15th, 2025 at 05:22 UT (24.6 hours after the trigger) and were carried out in the R filter with an average airmass of ~1.06 and exposure time of 20 minutes. Image subtraction against the SkyMapper Southern Survey (SMSS) Fourth Data Release (DR4) catalog (Onken et., 2024) shows no new uncataloged sources down to a 3-sigma limiting magnitude of ~24 AB mag. Several fainter sources are visible within the XRT localization of source #2 (Evans et al., GCN 42265) within the BAT localization, however they match catalogued counterparts in the Dark Energy Survey (DES) catalogue (DR2; Abbott et al. 2021) and, without a deeper template image, we cannot assess their variability. 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/42287. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40359] GRB 251014D: Swift/UVOT Upper Limits
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42286 SUBJECT: GRB 251014D: Swift/UVOT Upper Limits DATE: 25/10/15 12:45:11 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk> A.A. Breeveld (UCL-MSSL) and N. J. Klingler (GSFC/UMBC/CRESSTII) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251014D 160 s after the BAT trigger (Klingler et al., GCN Circ. 42274). No optical afterglow consistent with the XRT position (Page et al., GCN Circ. 42284)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 160 310 147 >20.7 white 160 4287 344 >20.9 v 4498 4697 197 >19.2 b 3882 5439 317 >19.9 u 318 5312 204 >19.8 w1 4907 5107 197 >19.7 m2 4702 4902 197 >19.6 w2 4293 4493 197 >19.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.020 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42286. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40358] GRB 251014D: BOOTES-6/DPRT optical upper limit
by GCN Circulars 15 Oct '25

15 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42285 SUBJECT: GRB 251014D: BOOTES-6/DPRT optical upper limit DATE: 25/10/15 11:12:43 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct(a)iaa.es> S. Guziy, I. Perez-Garcia, E. Fernandez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S.-Y. Wu 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), M. Jelinek (ASU-CAS), A. Kumar (ARIES) and C. J. Perez del Pulgar (UMA, Malaga), on behalf of a larger collaboration, report: Following the detection of GRB 251014D by Swift/BAT (Klingler et al., GCNC 42272), the BOOTES-6/DPRT 0.6m robotic telescope at Boyden Observatory in Maselspoort (South Africa) responded to this event starting on Oct 14, 23:03 UT (~ 1.1 h after trigger) with 120s clear-filter images. No new source is detected within the Swift/XRT X-ray afterglow error box (Page et al., GCNC 42284) up to magnitude 18.3 using Gaia DR3 Gmag magnitude as reference. Further images were gathered, resulting on an upper limit of 21.0 (a coadd of 1200s on the aggregate, 1.6 post burst, at 23:30 UT). We thank the staff at Boyden Observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/42285. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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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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