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[vsnet-grb-info 40628] Fermi GRB 251103A: Global MASTER-Net observations report
by GCN Circulars 03 Nov '25

03 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42565 SUBJECT: Fermi GRB 251103A: Global MASTER-Net observations report DATE: 25/11/03 23:31:13 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-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 251103A ( Fermi GBM team, GCN 42536) errorbox 63596 sec after notice time and 63634 sec after trigger time at 2025-11-03 22:27:02 UT, with upper limit up to 17.2 mag. The observations began at zenith distance = 77 deg. The sun altitude is -58.5 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 251103A errorbox 65141 sec after notice time and 65180 sec after trigger time at 2025-11-03 22:52:48 UT, with upper limit up to 16.8 mag. The observations began at zenith distance = 70 deg. The sun altitude is -52.4 deg. The galactic latitude b = 48 deg., longitude l = 216 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3030951 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 63665 | 2025-11-03 22:27:02 | MASTER-Tavrida | (09h 39m 04.69s , +19d 28m 36.2s) | C | 60 | 15.8 | 63743 | 2025-11-03 22:28:21 | MASTER-Tavrida | (09h 45m 39.49s , +18d 09m 40.8s) | C | 60 | 15.6 | 63812 | 2025-11-03 22:29:30 | MASTER-Tavrida | (09h 50m 09.05s , +19d 26m 40.9s) | C | 60 | 15.9 | 63890 | 2025-11-03 22:30:48 | MASTER-Tavrida | (09h 43m 57.72s , +20d 45m 36.4s) | C | 60 | 15.8 | 63957 | 2025-11-03 22:31:54 | MASTER-Tavrida | (09h 34m 46.40s , +18d 09m 53.8s) | C | 60 | 14.9 | 64037 | 2025-11-03 22:33:15 | MASTER-Tavrida | (09h 47m 09.24s , +16d 23m 55.5s) | C | 60 | 15.6 | 64112 | 2025-11-03 22:34:29 | MASTER-Tavrida | (09h 41m 40.15s , +16d 50m 37.4s) | C | 60 | 15.8 | 64187 | 2025-11-03 22:35:45 | MASTER-Tavrida | (09h 54m 59.68s , +20d 46m 42.7s) | C | 60 | 15.6 | 64264 | 2025-11-03 22:37:02 | MASTER-Tavrida | (09h 49m 01.38s , +22d 03m 37.6s) | C | 60 | 16.1 | 64429 | 2025-11-03 22:39:47 | MASTER-Tavrida | (09h 37m 53.16s , +15d 32m 17.9s) | C | 60 | 16.0 | 64597 | 2025-11-03 22:42:34 | MASTER-Tavrida | (09h 52m 28.41s , +16d 52m 15.0s) | C | 60 | 16.0 | 64665 | 2025-11-03 22:43:42 | MASTER-Tavrida | (09h 56m 36.54s , +18d 09m 42.0s) | C | 60 | 15.9 | 64740 | 2025-11-03 22:44:58 | MASTER-Tavrida | (09h 48m 39.02s , +15d 32m 54.2s) | C | 60 | 15.9 | 64817 | 2025-11-03 22:46:15 | MASTER-Tavrida | (10h 01m 15.68s , +19d 27m 16.3s) | C | 60 | 15.9 | 64896 | 2025-11-03 22:47:34 | MASTER-Tavrida | (09h 32m 51.01s , +20d 44m 10.5s) | C | 60 | 15.9 | 65080 | 2025-11-03 22:50:38 | MASTER-Tavrida | (09h 30m 39.62s , +16d 50m 15.8s) | C | 60 | 16.2 | 65210 | 2025-11-03 22:52:48 | MASTER-Kislovodsk | (09h 45m 41.10s , +15d 52m 44.3s) | C | 60 | 15.3 | 65210 | 2025-11-03 22:52:48 | MASTER-Kislovodsk | (09h 45m 37.84s , +16d 14m 48.4s) | C | 60 | 15.3 | 65252 | 2025-11-03 22:53:30 | MASTER-Tavrida | (09h 28m 08.59s , +19d 27m 24.4s) | C | 60 | 16.0 | 65290 | 2025-11-03 22:54:08 | MASTER-Kislovodsk | (09h 45m 42.17s , +15d 53m 49.3s) | C | 60 | 15.3 | 65290 | 2025-11-03 22:54:08 | MASTER-Kislovodsk | (09h 45m 38.78s , +16d 15m 52.2s) | C | 60 | 15.2 | 65329 | 2025-11-03 22:54:47 | MASTER-Tavrida | (10h 03m 23.21s , +16d 50m 53.3s) | C | 60 | 16.0 | 65370 | 2025-11-03 22:55:27 | MASTER-Kislovodsk | (09h 45m 44.69s , +16d 14m 55.7s) | C | 60 | 14.4 | 65407 | 2025-11-03 22:56:04 | MASTER-Tavrida | (09h 59m 28.09s , +15d 33m 03.1s) | C | 60 | 16.1 | 65450 | 2025-11-03 22:56:47 | MASTER-Kislovodsk | (09h 45m 37.64s , +16d 14m 01.1s) | C | 60 | 13.0 | 65492 | 2025-11-03 22:57:30 | MASTER-Tavrida | (09h 45m 09.73s , +14d 16m 08.9s) | C | 60 | 16.0 | 65572 | 2025-11-03 22:58:49 | MASTER-Tavrida | (09h 43m 15.43s , +23d 20m 25.8s) | C | 60 | 15.9 | 65652 | 2025-11-03 23:00:09 | MASTER-Tavrida | (09h 23m 45.21s , +18d 09m 40.8s) | C | 60 | 16.3 | 65719 | 2025-11-03 23:00:47 | MASTER-Kislovodsk | (09h 45m 40.53s , +16d 14m 40.7s) | C | 120 | 12.0 | 65732 | 2025-11-03 23:01:29 | MASTER-Tavrida | (09h 55m 49.49s , +14d 15m 39.6s) | C | 60 | 16.1 | 65813 | 2025-11-03 23:02:51 | MASTER-Tavrida | (10h 07m 38.94s , +18d 09m 58.4s) | C | 60 | 15.8 | 65859 | 2025-11-03 23:03:06 | MASTER-Kislovodsk | (09h 45m 43.46s , +16d 16m 15.9s) | C | 120 | 13.2 | 65998 | 2025-11-03 23:05:26 | MASTER-Kislovodsk | (09h 45m 42.35s , +15d 53m 35.0s) | C | 120 | 13.1 | 65998 | 2025-11-03 23:05:26 | MASTER-Kislovodsk | (09h 45m 38.38s , +16d 15m 33.9s) | C | 120 | 13.8 | 66058 | 2025-11-03 23:05:26 | MASTER-Kislovodsk | (09h 45m 38.38s , +16d 15m 33.9s) | C | 240 | 14.9 | Coadd 65983 | 2025-11-03 23:05:41 | MASTER-Tavrida | (10h 00m 15.07s , +22d 04m 18.9s) | C | 60 | 15.7 | 66063 | 2025-11-03 23:07:01 | MASTER-Tavrida | (09h 34m 27.78s , +14d 15m 40.9s) | C | 60 | 15.2 | 66108 | 2025-11-03 23:07:46 | MASTER-Kislovodsk | (09h 45m 38.40s , +16d 16m 40.2s) | C | 60 | 14.3 | 66143 | 2025-11-03 23:08:21 | MASTER-Tavrida | (10h 06m 05.12s , +20d 46m 52.5s) | C | 60 | 14.8 | 66188 | 2025-11-03 23:09:05 | MASTER-Kislovodsk | (09h 45m 44.30s , +16d 15m 44.3s) | C | 60 | 14.6 | 66268 | 2025-11-03 23:10:25 | MASTER-Kislovodsk | (09h 45m 37.28s , +16d 14m 49.5s) | C | 60 | 15.0 | 66328 | 2025-11-03 23:10:25 | MASTER-Kislovodsk | (09h 45m 37.28s , +16d 14m 49.4s) | C | 180 | 16.6 | Coadd 66322 | 2025-11-03 23:11:19 | MASTER-Tavrida | (09h 27m 05.34s , +15d 31m 34.4s) | C | 60 | 16.1 | 66676 | 2025-11-03 23:17:14 | MASTER-Kislovodsk | (09h 45m 43.23s , +16d 16m 03.7s) | C | 60 | 16.3 | 66676 | 2025-11-03 23:17:14 | MASTER-Kislovodsk | (09h 45m 50.89s , +15d 54m 01.9s) | C | 60 | 16.5 | 66708 | 2025-11-03 23:17:45 | MASTER-Tavrida | (09h 26m 34.95s , +22d 02m 43.8s) | C | 60 | 16.9 | 66756 | 2025-11-03 23:18:34 | MASTER-Kislovodsk | (09h 45m 46.97s , +15d 55m 46.6s) | C | 60 | 16.7 | 66756 | 2025-11-03 23:18:34 | MASTER-Kislovodsk | (09h 45m 39.21s , +16d 17m 48.1s) | C | 60 | 16.3 | 66789 | 2025-11-03 23:19:07 | MASTER-Tavrida | (09h 54m 31.91s , +23d 22m 17.1s) | C | 60 | 17.1 | 66836 | 2025-11-03 23:19:54 | MASTER-Kislovodsk | (09h 45m 46.98s , +15d 53m 57.9s) | C | 60 | 16.7 | 66836 | 2025-11-03 23:19:54 | MASTER-Kislovodsk | (09h 45m 39.10s , +16d 15m 58.7s) | C | 60 | 16.3 | 66896 | 2025-11-03 23:19:54 | MASTER-Kislovodsk | (09h 45m 39.10s , +16d 15m 58.7s) | C | 180 | 16.8 | Coadd 66917 | 2025-11-03 23:21:14 | MASTER-Kislovodsk | (09h 45m 51.06s , +15d 55m 42.0s) | C | 60 | 16.8 | 66917 | 2025-11-03 23:21:14 | MASTER-Kislovodsk | (09h 45m 43.07s , +16d 17m 42.5s) | C | 60 | 16.5 | 66968 | 2025-11-03 23:22:05 | MASTER-Tavrida | (09h 31m 55.01s , +23d 19m 40.3s) | C | 60 | 17.2 | 66996 | 2025-11-03 23:22:34 | MASTER-Kislovodsk | (09h 45m 45.14s , +15d 55m 04.0s) | C | 60 | 16.3 | 66996 | 2025-11-03 23:22:34 | MASTER-Kislovodsk | (09h 45m 37.01s , +16d 17m 04.4s) | C | 60 | 16.1 | 67076 | 2025-11-03 23:23:54 | MASTER-Kislovodsk | (09h 45m 45.15s , +15d 56m 08.7s) | C | 60 | 16.6 | 67076 | 2025-11-03 23:23:54 | MASTER-Kislovodsk | (09h 45m 36.92s , +16d 18m 08.8s) | C | 60 | 16.3 | 67157 | 2025-11-03 23:25:14 | MASTER-Kislovodsk | (09h 45m 41.84s , +16d 17m 11.6s) | C | 60 | 16.4 | 67157 | 2025-11-03 23:25:14 | MASTER-Kislovodsk | (09h 45m 50.18s , +15d 55m 11.6s) | C | 60 | 16.5 | 67237 | 2025-11-03 23:26:34 | MASTER-Kislovodsk | (09h 45m 35.80s , +16d 16m 16.3s) | C | 60 | 16.4 | 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/42565. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40620] LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
by GCN Circulars 03 Nov '25

03 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42564 SUBJECT: LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate DATE: 25/11/03 22:36:28 GMT FROM: Dripta Bhattacharjee <dripta.bhattacharjee(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S251103f during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-11-03 22:05:26.540 UTC (GPS time: 1446242744.540). 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. S251103f is an event of interest because its false alarm rate, as estimated by the online analysis, is 4.2e-14 Hz, or about one in 1e6 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S251103f The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass (HasNS) is <1%. [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 (11.0, 22.0) solar masses, assuming the candidate is astrophysical in origin. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * amplfi.multiorder.fits,0, an initial localization generated by AMPLFI [9], distributed via GCN and SCiMMA notices about 20 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 981 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 2158 +/- 568 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/42564. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40625] EP251102a: NIR observations with WINTER
by GCN Circulars 03 Nov '25

03 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42563 SUBJECT: EP251102a: NIR observations with WINTER DATE: 25/11/03 22:02:24 GMT FROM: Geoffrey Mo at Caltech / Carnegie Observatories <gmo(a)mit.edu> Geoffrey Mo (Caltech/Carnegie), Tomas Ahumada (Caltech), Viraj Karambelkar (Columbia/CCA), 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 EP251102a (Liang et al., GCN 42548) 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 2025-11-03T10:34:56 UTC in the J band (13.2 hours after the EP 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 do not detect a source at the optical counterpart location (Schneider et al., GCN 42544; Eyles-Ferris et al., GCN 42546) after image subtraction performed relative to J-band images from the UKIRT Hemisphere survey (Dye et al., 2017). We set a 3-sigma upper limit of J ~ 19.6 mag (AB) and a 5-sigma upper limit of J ~ 19.1 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/42563. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40624] GRB 251103A: J-band detection with WINTER
by GCN Circulars 03 Nov '25

03 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42562 SUBJECT: GRB 251103A: J-band detection with WINTER DATE: 25/11/03 22:00:37 GMT FROM: Geoffrey Mo at Caltech / Carnegie Observatories <gmo(a)mit.edu> Geoffrey Mo (Caltech/Carnegie), Benjamin Schneider (LAM), Tomas Ahumada (Caltech), Viraj Karambelkar (Columbia), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of GRB 251103A (Hu et al., GCN 42534, Fermi GBM Team, GCN 42536; Osborne et al., GCN 42551; Wang et al., GCN 42552; Sonawane et al., GCN 42553) 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). Two epochs of observations were performed in the J band, beginning at 2025-11-03T10:02 UTC (+5.3 hours after the GRB trigger) and at 2025-11-03T11:39:53 UTC (+6.9 hours), each 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 source at the optical counterpart location (Schneider et al., GCN 42535; Turpin et al., GCN 42538; Gritsevich et al., GCN 42539; Izzo et al., GCN 42540; O'Neill et al., GCN 42543; Ghosh et al., GCN 42545; Schneider et al., GCN 42549; Breeveld et al., GCN 42554; Hellot et al., GCN 42559) in the first epoch, with magnitude J ~ 19.4 mag (AB). In the second epoch, we set a 3-sigma upper limit of J ~ 19.7 mag (AB) and a 5-sigma upper limit of J ~ 19.3 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/42562. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40627] Swift GRB 251103B: Global MASTER-Net observations report
by GCN Circulars 03 Nov '25

03 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42561 SUBJECT: Swift GRB 251103B: Global MASTER-Net observations report DATE: 25/11/03 21:35:01 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 251103B ( S. Lanava et al., GCN 42556) errorbox 16520 sec after notice time and 16537 sec after trigger time at 2025-11-03 21:22:14 UT, with upper limit up to 18.3 mag. The observations began at zenith distance = 70 deg. The sun altitude is -40.6 deg. The galactic latitude b = -8 deg., longitude l = 237 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3031294 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 16628 | MASTER-SAAO | C | 180 | 18.3 | 16628 | MASTER-SAAO | C | 180 | 17.4 | 16840 | MASTER-SAAO | C | 180 | 17.4 | 16840 | MASTER-SAAO | C | 180 | 18.3 | 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/42561. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40622] GRB 251103B: GROWTH-India Telescope optical upper limits
by GCN Circulars 03 Nov '25

03 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42560 SUBJECT: GRB 251103B: GROWTH-India Telescope optical upper limits DATE: 25/11/03 21:20:07 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> T. Mohan, V. Vijaykumar, V. Swain, S. Patil, A.P. Saikia, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of GRB 251103B, detected by Fermi (Fermi GBM team, GCN 42555) and Swift (Lanava et al., GCN 42556), using the 0.7m GROWTH-India Telescope (GIT). We started the observation at 2025-11-03 20:09:26 UT, i.e., 3.38 hours after the GRB trigger and obtained multiple exposures in the r' and g' filters. No optical counterpart was detected within the Swift-XRT localization region (Evans et al., GCN 42558). The photometric upper limits are as follows: | MJD (mid) | Filter | tmid-t0 (hours) | Exposure Time (sec) | Upper limit (AB) | | ------------ | ------ | ------------ | ---------------------- | ---------------- | | 60982.84498 | g' | 3.5 | 360 | 19.4 | | 60982.85227 | r' | 3.68 | 4x360 | 20.5 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/42560. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40616] GRB 251103A: Kilonova-Catcher optical afterglow detection
by GCN Circulars 03 Nov '25

03 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42559 SUBJECT: GRB 251103A: Kilonova-Catcher optical afterglow detection DATE: 25/11/03 21:17:21 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> R. Hellot, M. Freeberg (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 251103A detected by SVOM (Hu et al., GCN 42534; Wang et al., GCN 42552) and Fermi/GBM (Fermi GBM team GCN 45536) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with a TEC160FL telescope operated by M. Freeberg and a CDK17 telescope located at AITP San Pedro Chile Observatory operated by R. Hellot. Our observations started at TGRB+3.2hr and were taken with sdss ri filters. In our stacked frames, subtracted from the PanSTARRS DR2 template image, we detect the optical counterpart reported by the NOT (Schneider et al., GCN 42535), LCOGT/1m (Turpin et al., GCN 42538; Ghosh et al., GCN 42545), BOOTES-2/TELMA (Gritsevich et al., GCN 42539), GOTO (O'Neill et al., GCN 42543), SVOM/COLIBRÍ (FM-GFT) (Schneider et al., GCN 42549), Swift/UVOT (Breeveld et al., GCN 42554). We report part of our follow-up results in the table below: +---------------+-----------+--------+----------------+--------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+===========+========+================+==============+ | 3.62 | 10 x 180s | r (AB) | 18.66 +/- 0.06 | CDK17 AITP | | 4.89 | 10 x 180s | r (AB) | 19.02 +/- 0.12 | TEC160FL | | 5.46 | 10 x 180s | i (AB) | 19.33 +/- 0.28 | TEC160FL | +---------------+-----------+--------+----------------+--------------+ 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. 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/42559. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40626] GRB 251103B: Enhanced Swift-XRT position
by GCN Circulars 03 Nov '25

03 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42558 SUBJECT: GRB 251103B: Enhanced Swift-XRT position DATE: 25/11/03 20:12:14 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 1251 s of XRT Photon Counting mode data and 1 UVOT images for GRB 251103B, 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 = 105.87339, -24.87217 which is equivalent to: RA (J2000): 07h 03m 29.61s Dec (J2000): -24d 52' 19.8" with an uncertainty of 2.3 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/42558. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40614] LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
by GCN Circulars 31 Oct '25

31 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42529 SUBJECT: LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate DATE: 25/10/31 19:29:26 GMT FROM: Dripta Bhattacharjee <dripta.bhattacharjee(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S251031cq during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-10-31 18:59:15.906 UTC (GPS time: 1445972373.906). The candidate was found by the Aframe [1], cWB [2], cWB BBH [3], GstLAL [4], MBTA [5], MLy [6], and PyCBC Live [7] analysis pipelines. S251031cq is an event of interest because its false alarm rate, as estimated by the online analysis, is 7e-10 Hz, or about one in 45 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S251031cq The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass (HasNS) is <1%. [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: * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [9], distributed via GCN and SCiMMA notices about 24 seconds after the candidate event time. * bayestar.multiorder.fits,2, an initial localization generated by BAYESTAR [9], 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,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 709 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 2083 +/- 562 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Marx et al. PRD 111, 042010 (2025) doi:10.1103/PhysRevD.111.042010 [2] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [3] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [4] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. PRD 109, 042008 (2024) doi:10.1103/PhysRevD.109.042008 [5] Alléné et al. CQG 42, 105009 (2025) doi:10.1088/1361-6382/add234 [6] Skliris et al. PRD 110, 104034 (2024) doi:10.1103/PhysRevD.110.104034 [7] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [8] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [9] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/42529. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40613] GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
by GCN Circulars 31 Oct '25

31 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42528 SUBJECT: GRB 251031A: Swift/BAT-GUANO localization skymap of a burst DATE: 25/10/31 18:52:57 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Samuele Ronchini (GSSI), Aaron Tohuvavohu (Cosmic Frontier), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (Northwestern) report: Swift/BAT did not localize GRB 251031A onboard (T0: 2025-10-31T07:21:00.49 UTC, Fermi Trig 783588065) The Fermi notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 8.4 in a 16.384 s analysis time bin, starting at T0 + 8.192 s. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 8,620 deg2 and the 50% credible area is 269 deg2. The integrated probability inside the coded field of view is 1%. The NITRATES skymap is consistent with the Fermi localization reported in the final position notice (GCN 42525). The combined Fermi/GBM+NITRATES 90% credible area is 168 deg2 and the 50% credible area is 47 deg2. A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=783588097/#:~:te… The probability skymap and joint skymap files can be downloaded from the links here [skymap_fits_file](https://guano.swift.psu.edu/files/783588097/0_n_PROBMAP) [joint_skymap_fits_file](https://guano.swift.psu.edu/files/783588097/0_n_JOI… Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=783588097 GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/42528. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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