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

[vsnet-grb-info 40550] GRB 251025B: MAO/AZT-22 optical observations
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42466 SUBJECT: GRB 251025B: MAO/AZT-22 optical observations DATE: 25/10/27 03:45:44 GMT FROM: Yodgor Rajabov at UBAI <rajabov(a)astrin.uz> Y. Rajabov, B.Abidkhanov, 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 251025B (Hussein et al., GCN 42437) with the 1.5-m at Maidanak Observatory telescope AZT-22 equipped with the 4kx4k CCD SNUCAM camera (Im et al., 2010). The OT (Wu et al., GCN 42438; Gress et al., GCN 42439; Wu et al., GCN 42440; Beardmore et al., GCN 42445; Mohan et al., GCN 42447; Hernández Funget al., GCN 42450; Pereyra et al., GCN 42452; Li et al., GCN 42453; Mo et al., GCN 42459; Rakotondrainibe et al., GCN 42460) 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) 2025-10-26 19:09:36 6x300 1.19827 R 20.75 0.03 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 Gaia DR3 Synphot 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/42466. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40549] LIGO/Virgo/KAGRA S251026bn: Updated Sky localization
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42465 SUBJECT: LIGO/Virgo/KAGRA S251026bn: Updated Sky localization DATE: 25/10/27 02:40:22 GMT FROM: lucy.thomas(a)ligo.org 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 S251026bn (GCN Circular 42462). 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/S251026bn For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 744 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1202 +/- 347 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/42465. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40548] Fermi GRB 251026B: Global MASTER-Net observations report
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42464 SUBJECT: Fermi GRB 251026B: Global MASTER-Net observations report DATE: 25/10/27 01:31:39 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 251026B ( Fermi GBM team, GCN 42455) errorbox 59309 sec after notice time and 62633 sec after trigger time at 2025-10-27 00:42:47 UT, with upper limit up to 18.4 mag. The observations began at zenith distance = 68 deg. The sun altitude is -32.5 deg. The galactic latitude b = 20 deg., longitude l = 239 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3023975 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 62664 | 2025-10-27 00:42:47 | MASTER-Kislovodsk | (08h 46m 04.47s , -11d 51m 14.2s) | C | 60 | 17.9 | 62664 | 2025-10-27 00:42:47 | MASTER-Kislovodsk | (08h 50m 15.56s , -12d 14m 29.7s) | C | 60 | 18.3 | 63317 | 2025-10-27 00:53:40 | MASTER-Kislovodsk | (08h 46m 04.23s , -11d 50m 49.0s) | C | 60 | 17.8 | 63317 | 2025-10-27 00:53:40 | MASTER-Kislovodsk | (08h 50m 17.20s , -12d 14m 14.5s) | C | 60 | 18.1 | 63959 | 2025-10-27 01:04:22 | MASTER-Kislovodsk | (08h 46m 02.23s , -11d 50m 25.1s) | C | 60 | 18.2 | 63959 | 2025-10-27 01:04:22 | MASTER-Kislovodsk | (08h 50m 16.29s , -12d 13m 53.6s) | C | 60 | 18.4 | 64626 | 2025-10-27 01:15:29 | MASTER-Kislovodsk | (08h 46m 09.08s , -11d 49m 58.6s) | C | 60 | 18.2 | 64626 | 2025-10-27 01:15:29 | MASTER-Kislovodsk | (08h 50m 18.58s , -12d 13m 27.0s) | C | 60 | 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/42464. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40547] Fermi GRB 251025C: Global MASTER-Net observations report
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42463 SUBJECT: Fermi GRB 251025C: Global MASTER-Net observations report DATE: 25/10/27 01:31:01 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-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 251025C ( Fermi GBM team, GCN 42449) errorbox 1 days 5134 sec after notice time and 1 days 5165 sec after trigger time at 2025-10-27 00:34:45 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 53 deg. The sun altitude is -33.9 deg. The galactic latitude b = 58 deg., longitude l = 147 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3023716 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 91596 | 2025-10-27 00:34:45 | MASTER-Kislovodsk | (11h 18m 11.77s , +54d 29m 42.9s) | C | 60 | 18.3 | 91596 | 2025-10-27 00:34:45 | MASTER-Kislovodsk | (11h 25m 08.42s , +54d 06m 43.1s) | C | 60 | 18.5 | 91675 | 2025-10-27 00:36:05 | MASTER-Kislovodsk | (11h 31m 25.80s , +55d 59m 16.1s) | C | 60 | 18.3 | 91675 | 2025-10-27 00:36:05 | MASTER-Kislovodsk | (11h 24m 10.23s , +56d 22m 21.0s) | C | 60 | 18.1 | 91755 | 2025-10-27 00:37:25 | MASTER-Kislovodsk | (11h 20m 02.72s , +52d 12m 24.9s) | C | 60 | 18.6 | 91755 | 2025-10-27 00:37:25 | MASTER-Kislovodsk | (11h 13m 24.71s , +52d 35m 17.4s) | C | 60 | 18.6 | 91835 | 2025-10-27 00:38:45 | MASTER-Kislovodsk | (11h 44m 17.61s , +54d 29m 12.9s) | C | 60 | 18.1 | 91835 | 2025-10-27 00:38:45 | MASTER-Kislovodsk | (11h 51m 11.39s , +54d 06m 05.0s) | C | 60 | 18.3 | 91916 | 2025-10-27 00:40:05 | MASTER-Kislovodsk | (11h 38m 20.05s , +52d 33m 52.5s) | C | 60 | 18.1 | 91996 | 2025-10-27 00:41:25 | MASTER-Kislovodsk | (11h 31m 44.37s , +58d 17m 35.7s) | C | 60 | 18.1 | 91996 | 2025-10-27 00:41:25 | MASTER-Kislovodsk | (11h 39m 22.93s , +57d 54m 25.4s) | C | 60 | 18.3 | 92236 | 2025-10-27 00:45:26 | MASTER-Kislovodsk | (11h 18m 07.62s , +54d 29m 57.0s) | C | 60 | 18.3 | 92236 | 2025-10-27 00:45:26 | MASTER-Kislovodsk | (11h 25m 08.02s , +54d 06m 32.4s) | C | 60 | 18.3 | 92316 | 2025-10-27 00:46:46 | MASTER-Kislovodsk | (11h 24m 08.47s , +56d 22m 38.2s) | C | 60 | 18.1 | 92316 | 2025-10-27 00:46:46 | MASTER-Kislovodsk | (11h 31m 24.36s , +55d 59m 08.8s) | C | 60 | 18.3 | 92396 | 2025-10-27 00:48:06 | MASTER-Kislovodsk | (11h 13m 23.20s , +52d 35m 54.1s) | C | 60 | 18.6 | 92396 | 2025-10-27 00:48:06 | MASTER-Kislovodsk | (11h 20m 01.70s , +52d 12m 36.7s) | C | 60 | 18.6 | 92476 | 2025-10-27 00:49:26 | MASTER-Kislovodsk | (11h 44m 17.35s , +54d 29m 36.7s) | C | 60 | 18.0 | 92476 | 2025-10-27 00:49:26 | MASTER-Kislovodsk | (11h 51m 11.53s , +54d 06m 03.7s) | C | 60 | 18.2 | 92556 | 2025-10-27 00:50:46 | MASTER-Kislovodsk | (11h 38m 19.67s , +52d 34m 11.0s) | C | 60 | 18.2 | 92644 | 2025-10-27 00:52:13 | MASTER-Kislovodsk | (11h 31m 43.71s , +58d 18m 05.9s) | C | 60 | 18.1 | 92644 | 2025-10-27 00:52:13 | MASTER-Kislovodsk | (11h 39m 22.66s , +57d 54m 30.1s) | C | 60 | 18.3 | 92890 | 2025-10-27 00:56:20 | MASTER-Kislovodsk | (11h 18m 04.46s , +54d 30m 35.0s) | C | 60 | 18.3 | 92890 | 2025-10-27 00:56:20 | MASTER-Kislovodsk | (11h 25m 08.64s , +54d 07m 10.4s) | C | 60 | 18.3 | 92970 | 2025-10-27 00:57:40 | MASTER-Kislovodsk | (11h 24m 09.70s , +56d 23m 16.5s) | C | 60 | 18.1 | 92970 | 2025-10-27 00:57:40 | MASTER-Kislovodsk | (11h 31m 27.23s , +55d 59m 48.2s) | C | 60 | 18.1 | 93050 | 2025-10-27 00:58:59 | MASTER-Kislovodsk | (11h 13m 21.24s , +52d 36m 14.7s) | C | 60 | 18.5 | 93050 | 2025-10-27 00:58:59 | MASTER-Kislovodsk | (11h 20m 01.17s , +52d 12m 57.7s) | C | 60 | 18.4 | 93129 | 2025-10-27 01:00:19 | MASTER-Kislovodsk | (11h 44m 15.91s , +54d 29m 56.6s) | C | 60 | 18.1 | 93129 | 2025-10-27 01:00:19 | MASTER-Kislovodsk | (11h 51m 11.44s , +54d 06m 23.7s) | C | 60 | 18.2 | 93210 | 2025-10-27 01:01:40 | MASTER-Kislovodsk | (11h 38m 18.17s , +52d 35m 14.3s) | C | 60 | 18.1 | 93290 | 2025-10-27 01:02:59 | MASTER-Kislovodsk | (11h 31m 44.06s , +58d 18m 37.3s) | C | 60 | 18.2 | 93290 | 2025-10-27 01:02:59 | MASTER-Kislovodsk | (11h 39m 24.39s , +57d 55m 02.7s) | C | 60 | 18.3 | 93533 | 2025-10-27 01:07:03 | MASTER-Kislovodsk | (11h 18m 02.58s , +54d 31m 12.2s) | C | 60 | 18.2 | 93533 | 2025-10-27 01:07:03 | MASTER-Kislovodsk | (11h 25m 08.82s , +54d 07m 52.0s) | C | 60 | 18.3 | 93613 | 2025-10-27 01:08:23 | MASTER-Kislovodsk | (11h 24m 07.26s , +56d 23m 53.1s) | C | 60 | 18.1 | 93613 | 2025-10-27 01:08:23 | MASTER-Kislovodsk | (11h 31m 26.30s , +56d 00m 29.1s) | C | 60 | 18.3 | 93693 | 2025-10-27 01:09:43 | MASTER-Kislovodsk | (11h 13m 21.14s , +52d 37m 05.7s) | C | 60 | 18.6 | 93693 | 2025-10-27 01:09:43 | MASTER-Kislovodsk | (11h 20m 02.47s , +52d 13m 53.0s) | C | 60 | 18.6 | 93793 | 2025-10-27 01:11:23 | MASTER-Kislovodsk | (11h 44m 13.86s , +54d 30m 52.5s) | C | 60 | 18.1 | 93793 | 2025-10-27 01:11:23 | MASTER-Kislovodsk | (11h 51m 10.90s , +54d 07m 24.6s) | C | 60 | 18.1 | 93879 | 2025-10-27 01:12:49 | MASTER-Kislovodsk | (11h 38m 18.19s , +52d 35m 51.5s) | C | 60 | 18.1 | 93959 | 2025-10-27 01:14:09 | MASTER-Kislovodsk | (11h 31m 42.25s , +58d 19m 32.6s) | C | 60 | 18.1 | 93959 | 2025-10-27 01:14:09 | MASTER-Kislovodsk | (11h 39m 23.62s , +57d 56m 04.3s) | C | 60 | 18.4 | 94399 | 2025-10-27 01:21:29 | MASTER-Kislovodsk | (11h 17m 59.49s , +54d 30m 58.7s) | C | 60 | 18.4 | 94399 | 2025-10-27 01:21:29 | MASTER-Kislovodsk | (11h 25m 03.05s , +54d 07m 53.1s) | C | 60 | 18.3 | 94478 | 2025-10-27 01:22:48 | MASTER-Kislovodsk | (11h 24m 10.99s , +56d 25m 08.0s) | C | 60 | 18.2 | 94478 | 2025-10-27 01:22:48 | MASTER-Kislovodsk | (11h 31m 32.09s , +56d 01m 57.7s) | C | 60 | 18.3 | 94558 | 2025-10-27 01:24:08 | MASTER-Kislovodsk | (11h 13m 15.55s , +52d 39m 26.4s) | C | 60 | 18.6 | 94558 | 2025-10-27 01:24:08 | MASTER-Kislovodsk | (11h 19m 58.90s , +52d 16m 26.6s) | C | 60 | 18.5 | 94640 | 2025-10-27 01:25:30 | MASTER-Kislovodsk | (11h 44m 14.15s , +54d 30m 13.3s) | C | 60 | 18.1 | 94640 | 2025-10-27 01:25:30 | MASTER-Kislovodsk | (11h 51m 12.53s , +54d 06m 56.7s) | C | 60 | 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/42463. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40546] LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42462 SUBJECT: LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate DATE: 25/10/26 22:11:15 GMT FROM: joan-rene.merou(a)ligo.org The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S251026bn during real-time processing of data from LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at 2025-10-26 21:16:05.296 UTC (GPS time: 1445548583.296). 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. S251026bn is an event of interest because its false alarm rate, as estimated by the online analysis, is 4.8e-12 Hz, or about one in 1e4 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S251026bn 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 8%. The source chirp mass falls with highest probability in the bin (5.5, 11.0) 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,0, an initial localization generated by BAYESTAR [9], distributed via GCN and SCiMMA notices about 29 seconds after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [9], 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,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is 956 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1254 +/- 349 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] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/42462. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40545] GRB 251026A: Swift-XRT observations
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42461 SUBJECT: GRB 251026A: Swift-XRT observations DATE: 25/10/26 21:42:15 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 source GRB 251026A (SVOM burst-id sb25102605), collecting 1.7 ks of Photon Counting (PC) mode data between T0+5.8 ks and T0+12 ks after the trigger. We have detected 2 sources. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 2 uncatalogued X-ray sources * 0 known X-ray sources We note that neither source is consistent with the SVOM/MXT position given in GCN Circ. 42454. Uncatalogued X-ray sources -------------------------- Source 1 (SWIFT J044944.9+514605): ================================== RA (J2000.0): 72.4374 = 04 49 44.98 Dec (J2000.0): +51.7683 = +51 46 05.9 Error: 5.1 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 5.8 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0123 +/- 0.0033 ct s^-1 Mean flux: (4.6 +/- 1.2)e-13 erg cm^-2 s^-1 Peak rate: 0.0123 +/- 0.0033 ct s^-1 Peak flux: (4.6 +/- 1.2)e-13 erg cm^-2 s^-1 ECF: 3.75e-11 erg cm^-2 ct^-1 assuming NH=1.57e+22 cm^-2, gamma=2.98 determined from a spectral fit. XMM UL: 3.5e-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 `NVSS J044945+514603' is 7.5" away. There are 2 2MASS objects within the source's 3-sigma error radius. Source 2 (SWIFT J045052.5+515630): ================================== RA (J2000.0): 72.7189 = 04 50 52.54 Dec (J2000.0): +51.9418 = +51 56 30.5 Error: 9.7 (arcsec, radius, 90% confidence). Detect flag: REASONABLE Distance: 9.6 arcmin from the SVOM/ECLAIRs position. Mean rate: (4.0 [+2.6, -1.8])e-3 ct s^-1 Mean flux: (1.74 [+1.10, -0.78])e-13 erg cm^-2 s^-1 Peak rate: (4.0 [+2.6, -1.8])e-3 ct s^-1 Peak flux: (1.74 [+1.10, -0.78])e-13 erg cm^-2 s^-1 XMM UL: 2.3e-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. A SIMBAD object `NVSS J045052+515630' is 3.9" away. There are 6 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_FIELD00045. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42461. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40544] GRB 251026A: Swift-XRT observations
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42461 SUBJECT: GRB 251026A: Swift-XRT observations DATE: 25/10/26 21:42:15 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 source GRB 251026A (SVOM burst-id sb25102605), collecting 1.7 ks of Photon Counting (PC) mode data between T0+5.8 ks and T0+12 ks after the trigger. We have detected 2 sources. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 2 uncatalogued X-ray sources * 0 known X-ray sources We note that neither source is consistent with the SVOM/MXT position given in GCN Circ. 42454. Uncatalogued X-ray sources -------------------------- Source 1 (SWIFT J044944.9+514605): ================================== RA (J2000.0): 72.4374 = 04 49 44.98 Dec (J2000.0): +51.7683 = +51 46 05.9 Error: 5.1 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 5.8 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0123 +/- 0.0033 ct s^-1 Mean flux: (4.6 +/- 1.2)e-13 erg cm^-2 s^-1 Peak rate: 0.0123 +/- 0.0033 ct s^-1 Peak flux: (4.6 +/- 1.2)e-13 erg cm^-2 s^-1 ECF: 3.75e-11 erg cm^-2 ct^-1 assuming NH=1.57e+22 cm^-2, gamma=2.98 determined from a spectral fit. XMM UL: 3.5e-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 `NVSS J044945+514603' is 7.5" away. There are 2 2MASS objects within the source's 3-sigma error radius. Source 2 (SWIFT J045052.5+515630): ================================== RA (J2000.0): 72.7189 = 04 50 52.54 Dec (J2000.0): +51.9418 = +51 56 30.5 Error: 9.7 (arcsec, radius, 90% confidence). Detect flag: REASONABLE Distance: 9.6 arcmin from the SVOM/ECLAIRs position. Mean rate: (4.0 [+2.6, -1.8])e-3 ct s^-1 Mean flux: (1.74 [+1.10, -0.78])e-13 erg cm^-2 s^-1 Peak rate: (4.0 [+2.6, -1.8])e-3 ct s^-1 Peak flux: (1.74 [+1.10, -0.78])e-13 erg cm^-2 s^-1 XMM UL: 2.3e-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. A SIMBAD object `NVSS J045052+515630' is 3.9" away. There are 6 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_FIELD00045. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42461. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40543] GRB 251025B: OHP/T193 optical detection
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42460 SUBJECT: GRB 251025B: OHP/T193 optical detection DATE: 25/10/26 21:20:15 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> N.A. Rakotondrainibe (LAM), C. Adami (LAM/Pytheas/AMU), E. Le Floc'h (CEA/Irfu), S. basa (UAR Pytheas) report on behalf of the MISTRAL GRB collaboration We carried out observations of the GRB 251025B (Hussein et al., GCN 42437) optical and NIR afterglow (Wu et al., GCN 42438; Gress et al., GCN 42439; Wu et al., GCN 42440; Beardmore et al., GCN 42445; Mohan et al., GCN 42447; Hernández Funget al., GCN 42450; Pereyra et al., GCN 42452; Li et al., GCN 42453; Mo et al., GCN 42459) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 1 exposure of 3 min and 5 exposures of 12 min in the r-band at a midtime of 2025-10-26 20:11:53 UT corresponding to T-T0 = 29.8 hours. The afterglow is well detected in r’ and we measured the following preliminary magnitude: r’ = 20.93+/-0.07 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 Jean Balcaen and the SOPHIE observer Guillaume Hebrard. View this GCN Circular online at https://gcn.nasa.gov/circulars/42460. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40542] GRB 251025B: SVOM/VT optical observations with VHF data
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42440 SUBJECT: GRB 251025B: SVOM/VT optical observations with VHF data DATE: 25/10/25 16:47:24 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C. Wu., L.P. Xin, H.L. Li, Y. L. Qiu (NAOC), J. T. Palmerio (CEA), S. Hussein (IJCLab), M. Brunet (IRAP) report on behalf of the SVOM team. SVOM/VT performed an automatic slew on the burst triggered by SVOM/ECLAIRs (Hussein et al., GCN 42437). SVOM/VT began observing the field automatically at 2025-10-25T14:30:18 UTC, 373 seconds after the T0, with the slew of the platform triggered on-board, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. We confirm the clear detection of the source reported by Wu et al.(GCN 42438) and Gress et al.(GCN 42439) in both the VT_B and VT_R bands with the downlinked VHF data. The AB magnitudes were derived as follows: -------------------------------------------- (T-T0)_mid exptime band mag 523 sec 300 sec VT_R 18.61 +/-0.01 523 sec 300 sec VT_B 19.15 +/-0.02 We note that the color of VT_B - VT_R ~ 0.5 mag may indicate a low-to-medium redshift event, following the analysis of Wang et al. (2020, RAA). Additional follow-up observations are encouraged. 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/42440. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40541] GRB 251025B: J-band detection with WINTER
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42459 SUBJECT: GRB 251025B: J-band detection with WINTER DATE: 25/10/26 17:17:21 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 251025B (Hussein et al., GCN 42437; Beardmore et al., GCN 42445) 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 2025-10-26T04:48:17 UTC in the J band (~14.4 hours 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 (Wu et al., GCN 42438; Gress et al., GCN 42439; Wu et al., GCN 42440; Mohan et al., GCN 42447; Hernández Fung et al., GCN 42450; Pereyra et al., GCN 42452; Li et al., GCN 42453), likely during its rebrightening phase, with magnitude J ~ 20.0 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/42459. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0