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[vsnet-grb-info 41452] EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
by GCN Circulars 09 Jan '26

09 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43360 SUBJECT: EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection DATE: 26/01/09 17:32:30 GMT FROM: mariaedvige.ravasio(a)ru.nl M. E. Ravasio (ICE-CSIC and Radboud Univ.), and P.G. Jonker (Radboud Univ.) and E. Burns (LSU), M. Hui (NASA MSFC), R. Hamburg and O. Mukherjee (USRA) report on behalf of the Fermi-GBM Team: Fermi-GBM had full spatial and temporal coverage of the transient EP260105b detected by EP-WXT (Yang et al., GCN 43340, EP Team GCN 43349). There was no Fermi-GBM onboard trigger around the EP trigger time at T0=2026-01-05T18:47:36 UTC. The GBM Targeted Search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [-50;+500] s from the EP T0. A transient was found, with the most significant signal at T0-32 s on a 16 s timescale, with a false alarm rate of 6.5e-05 Hz. The localisation is consistent with the EP one, with a spatial association probability of 96.3%. Among the three spectral templates tested, the transient was best-fit with a “normal” spectral template (Band function with Epeak = 230 keV, alpha = -1.0, beta = -2.3) for a GRB. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/43360. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41451] Swift Trigger 1434591: possible GRB 260109C
by GCN Circulars 09 Jan '26

09 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43359 SUBJECT: Swift Trigger 1434591: possible GRB 260109C DATE: 26/01/09 13:17:07 GMT FROM: P.A. Evans at U. Leicester <pae9(a)leicester.ac.uk> T. M. Parsotan (GSFC), P. A. Evans (U Leicester), R. Gupta (NASA GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), A. Mei (INAF-OAB), K. L. Page (U Leicester), C. Salvaggio (INAF-OAB) and B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 12:47:15 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 260109C (trigger=1434591). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 123.728, -35.258 which is RA(J2000) = 08h 14m 55s Dec(J2000) = -35d 15' 27" 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 15 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~10 sec after the trigger. The XRT began observing the field at 12:48:41.8 UT, 86.8 seconds after the BAT trigger. No source was detected in 1.3 ks 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 250 seconds with the U filter starting 146 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. The typical 3-sigma upper limit has been about 19.2 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. The limiting magnitude for the list of sources is expected to be about 17.7. No correction has been made for extinction. Burst Advocate for this burst is T. M. Parsotan (tyler.parsotan AT nasa.gov) 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/43359. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41450] GRB 260109B: Fermi GBM Final Real-time Localization
by GCN Circulars 09 Jan '26

09 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43358 SUBJECT: GRB 260109B: Fermi GBM Final Real-time Localization DATE: 26/01/09 08:52:04 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 08:41:22 UT on 9 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260109B (trigger 789640887.356258 / 260109362). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 197.5, Dec = -73.9 (J2000 degrees, equivalent to J2000 13h 09m, -73d 54'), with a statistical uncertainty of 13.7 degrees. The angle from the Fermi LAT boresight is 54.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260109362/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260109362/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260109362/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43358. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41449] GRB 260102A: Swift-XRT afterglow detection
by GCN Circulars 09 Jan '26

09 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43357 SUBJECT: GRB 260102A: Swift-XRT afterglow detection DATE: 26/01/09 06:45:08 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M.G. Bernardini (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-OAR) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has conducted further observations of the field of the SVOM/ECLAIRs-detected burst GRB 260102A. The observations now extend from T0+9.6 ks to T0+582.4 ks and have a total exposure time of 7.3 ks. The source previously reported, "Source 2", is fading with >3-sigma significance, and is therefore likely the GRB afterglow. Using 838 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 183.94925, +48.25058 which is equivalent to: RA (J2000): 12h 15m 47.82s Dec(J2000): +48d 15' 02.1" with an uncertainty of 6.2 arcsec (radius, 90% confidence). This position is 2.8 arcmin from the SVOM/ECLAIRs position. The source is fading with alpha >0.2. The results of the XRT-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/ToO_GRBs/00021896/Source2.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021896. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43357. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41448] GRB 260109A: Fermi GBM Final Real-time Localization
by GCN Circulars 09 Jan '26

09 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43356 SUBJECT: GRB 260109A: Fermi GBM Final Real-time Localization DATE: 26/01/09 03:55:04 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 03:44:24 UT on 9 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260109A (trigger 789623069.789512 / 260109156). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 307.3, Dec = -69.0 (J2000 degrees, equivalent to J2000 20h 29m, -69d 00'), with a statistical uncertainty of 8.0 degrees. The angle from the Fermi LAT boresight is 90.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260109156/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260109156/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260109156/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43356. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41447] GRB 260104A: Swift-BAT refined analysis
by GCN Circulars 09 Jan '26

09 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43355 SUBJECT: GRB 260104A: Swift-BAT refined analysis DATE: 26/01/09 03:01:10 GMT FROM: Tyler Parsotan at NASA GSFC <tyler.parsotan(a)nasa.gov> M. J. Moss (GSFC), S. D. Barthelmy (GSFC), R. Caputo (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 260104A (trigger #1430212) (Caputo, et al., GCN Circ. 43315). The BAT ground-calculated position is RA, Dec = 337.395, -21.291 deg which is RA(J2000) = 22h 29m 34.8s Dec(J2000) = -21d 17' 27.5" with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 99%. The mask-weighted light curve shows two pulses. T90 (15-350 keV) is 13.26 +- 2.65 sec (estimated error including systematics). The time-averaged spectrum from T-10.09 to T+5.22 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.32 +- 1.08, and Epeak of 42.5 +- 8.8 keV (chi squared 67.04 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 3.5 +- 0.5 x 10^-07 erg/cm2 and the 1-sec peak flux measured from T-0.23 sec in the 15-150 keV band is 1.3 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.85 +- 0.16 (chi squared 76.81 for 57 d.o.f.). 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/1430212 View this GCN Circular online at https://gcn.nasa.gov/circulars/43355. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41446] GRB 260101A: Swift-BAT refined analysis
by GCN Circulars 09 Jan '26

09 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43354 SUBJECT: GRB 260101A: Swift-BAT refined analysis DATE: 26/01/09 03:00:04 GMT FROM: Tyler Parsotan at NASA GSFC <tyler.parsotan(a)nasa.gov> C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), M. J. Moss (GSFC), D. M. Palmer (LANL), 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+1066 sec from the recent telemetry downlink, we report further analysis of BAT GRB 260101A (trigger #1429608) (Cenko, et al., GCN Circ. 43285). The BAT ground-calculated position is RA, Dec = 86.442, 63.583 deg which is RA(J2000) = 05h 45m 46.2s Dec(J2000) = +63d 34' 57.2" with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 78%. The mask-weighted light curve shows a complex light curve with many emission episodes. T90 (15-350 keV) is 48.00 +- 16.00 sec (estimated error including systematics). The time-averaged spectrum from T-31.26 to T+64.74 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.28 +- 0.23, and Epeak of 109.2 +- 64.4 keV (chi squared 55.17 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 4.5 +- 0.2 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T+24.24 sec in the 15-150 keV band is 4.6 +- 0.3 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.62 +- 0.06 (chi squared 62.07 for 57 d.o.f.). 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/1429608 View this GCN Circular online at https://gcn.nasa.gov/circulars/43354. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41445] Swift GRB 251230A: Global MASTER-Net OT detection
by GCN Circulars 08 Jan '26

08 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43353 SUBJECT: Swift GRB 251230A: Global MASTER-Net OT detection DATE: 26/01/08 18:03:52 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> D. Buckley (South African Astronomical Observatory), V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko, G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), O.A. Gress, N.M. Budnev, O.Ershova (Irkutsk State University, API), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich (Blagoveschensk Educational State University) MASTER-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) was pointed to the GRB 251230A ( S. Lanava et al., GCN 43252) 1908 sec after notice time and 1930 sec after trigger time at 2025-12-30 01:53:52 UT. On our first (180s exposure) set we found 1 optical transient within Swift error-box (ra=179.892 dec=11.415 r=0.05) brighter than 19.2. T-Tmid Date Time Expt. Ra Dec Mag ---------|---------------------|-------|-----------------|-----------------|------- 2020 2025-12-30 01:53:52 180 (11h 59m 35.40s , +11d 26m 18.8s) 16.4 The 5-sigma upper limit has been about 19.2mag The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp.http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43353. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41444] Fermi GRB 260107A: Global MASTER-Net observations report
by GCN Circulars 08 Jan '26

08 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43352 SUBJECT: Fermi GRB 260107A: Global MASTER-Net observations report DATE: 26/01/08 15:38:08 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 [1] located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 260107A ( Fermi GBM team, GCN 43350) errorbox 45 sec after notice time and 53 sec after trigger time at 2026-01-07 19:57:55 UT, with upper limit up to 16.7 mag. The observations began at zenith distance = 87 deg. The sun altitude is -22.6 deg. The galactic latitude b = -47 deg., longitude l = 70 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3098086 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 59 | 2026-01-07 19:57:55 | MASTER-SAAO | (22h 46m 37.28s , +02d 30m 33.7s) | C | 10 | 16.1 | 93 | 2026-01-07 19:58:24 | MASTER-SAAO | (22h 46m 36.17s , +02d 30m 45.9s) | C | 20 | 16.4 | 131 | 2026-01-07 19:59:03 | MASTER-SAAO | (22h 46m 35.02s , +02d 30m 58.5s) | C | 20 | 16.3 | 196 | 2026-01-07 19:59:57 | MASTER-SAAO | (22h 44m 44.92s , +00d 59m 56.2s) | C | 40 | 16.7 | 260 | 2026-01-07 20:00:56 | MASTER-SAAO | (22h 44m 43.40s , +01d 00m 12.6s) | C | 50 | 16.3 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43352. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41443] GRB 260102A: AbAO optical observations
by GCN Circulars 08 Jan '26

08 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43351 SUBJECT: GRB 260102A: AbAO optical observations DATE: 26/01/08 14:28:34 GMT FROM: Nicolai Pankov at IKI <colinsergesen(a)gmail.com> N. Pankov (IKI), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO), A. Volnova (IKI) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of GRB 260102A (XIE et. al, GCN 43295; Evans, GCN 43298; Bernardini et. al, GCN 43304; Yin et. al, GCN 43307; Hamburg, GCN 43308) in the R-filter with the 0.7-meter AS-32 telescope of Abastumani Observatory (AbAO). Two epochs of observations were taken, the first one began on 2026-01-02 19:21:22 UT, i.e. ~0.65 days since trigger. The optical counterpart (Wu et. al, GCN 43300) was not detected in the co-add images of both epochs. The preliminary upper limits and the observation details are given below: Date UT start t-T0 Exp. Filter OT Err. UL (mid, days) (s) (3sigma) 2026-01-02 19:21:22 0.65786 72*60 R n/d n/d 20.1 2026-01-03 19:22:18 1.65850 72*60 R n/d n/d 19.8 The photometry was calibrated using nearby stars from USNO-B1.0 and was not corrected for the Galactic extinction. The obtained results do not contradict the optical upper limits from other groups (Antier et. al, GCN 43303; Saccardi et. al, GCN 43305). View this GCN Circular online at https://gcn.nasa.gov/circulars/43351. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41442] GRB 260107A: Fermi GBM Final Real-time Localization
by GCN Circulars 07 Jan '26

07 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43350 SUBJECT: GRB 260107A: Fermi GBM Final Real-time Localization DATE: 26/01/07 20:07:44 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 19:57:01 UT on 7 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260107A (trigger 789508626.671092 / 260107831). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 339.0, Dec = 2.0 (J2000 degrees, equivalent to J2000 22h 36m, 2d 00'), with a statistical uncertainty of 2.6 degrees. The angle from the Fermi LAT boresight is 73.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260107831/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260107831/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260107831/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43350. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41441] GRB 260107A: Fermi GBM Final Real-time Localization
by GCN Circulars 07 Jan '26

07 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43350 SUBJECT: GRB 260107A: Fermi GBM Final Real-time Localization DATE: 26/01/07 20:07:44 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 19:57:01 UT on 7 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260107A (trigger 789508626.671092 / 260107831). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 339.0, Dec = 2.0 (J2000 degrees, equivalent to J2000 22h 36m, 2d 00'), with a statistical uncertainty of 2.6 degrees. The angle from the Fermi LAT boresight is 73.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260107831/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260107831/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260107831/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43350. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41440] EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
by GCN Circulars 07 Jan '26

07 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43349 SUBJECT: EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient DATE: 26/01/07 13:08:28 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> X. X. Sun, G. J. Yang, M. J. Liu, , C. C. Jin, Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260105b. The transient triggered EP-WXT (ID: 01709251028) at 2026-01-05T18:47:36 (UTC). The WXT position of the source is R.A. = 158.387 deg, DEC = 17.616 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). In a previous Circular (Yang et al. , GCN 43340) , this event was tentatively classified as a stellar flare associated with ET Leo, based on the preliminary localization and flux estimation available at that time. After refined data processing and ground analysis of the WXT and FXT observations, we find that the evnet is unlikely to be a stellar flare from ET Leo. We find a short-timescale X-ray varability in the WXT refined telemetry data, therefore classify this event as an X-ray transient. A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 158.3695 deg, DEC = 17.6123 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). A significant decay was detected in the light curve during the initial phase of FXT observation. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 2.97 x 10^20 cm^-2 and a photon index of 2.18(-0.87,0.92). The derived average unabsorbed 0.5-10 keV flux is 2.6 (-0.94/+2.59) x 10^(-13) erg/s/cm^2. Further multiwavelength follow-up observations are encouraged to clarify the physical nature of this transient. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43349. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41439] The EP-WXT trigger 01709251112 is likely a flaring star
by GCN Circulars 07 Jan '26

07 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43348 SUBJECT: The EP-WXT trigger 01709251112 is likely a flaring star DATE: 26/01/07 10:53:44 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Y. Ren (NAOC), Q.-C. Liu (THU), R.-Z. Li (YNAO, CAS) and H. Sun (NAOC) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709251112 at the time of 2026-01-07T10:12:47, is likely a stellar flare associated with PM J08310+4012. The estimated flux of the flare is around 8e-11 erg/s/cm^2 in 0.5-4.0 keV. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43348. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41438] Fermi GRB 260105A: Global MASTER-Net observations report
by GCN Circulars 07 Jan '26

07 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43347 SUBJECT: Fermi GRB 260105A: Global MASTER-Net observations report DATE: 26/01/07 03:45:50 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-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 260105A ( Fermi GBM team, GCN 43335) errorbox 42914 sec after notice time and 42952 sec after trigger time at 2026-01-06 10:43:04 UT, with upper limit up to 19.2 mag. Observations started at twilight. The observations began at zenith distance = 35 deg. The sun altitude is -12.9 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 260105A errorbox 1 days 4422 sec after notice time and 1 days 4460 sec after trigger time at 2026-01-07 00:01:32 UT, with upper limit up to 17.2 mag. The observations began at zenith distance = 48 deg. The sun altitude is -50.2 deg. The galactic latitude b = 4 deg., longitude l = 150 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3096780 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 42983 | 2026-01-06 10:43:04 | MASTER-Tunka | (04h 46m 35.26s , +57d 50m 19.5s) | C | 60 | 19.2 | 42983 | 2026-01-06 10:43:04 | MASTER-Tunka | (04h 47m 41.61s , +57d 41m 18.4s) | C | 60 | 18.7 | 49648 | 2026-01-06 12:34:09 | MASTER- | (04h 54m 01.68s , +56d 22m 44.2s) | C | 60 | 17.3 | 49648 | 2026-01-06 12:34:09 | MASTER- | (04h 52m 23.46s , +56d 56m 52.2s) | C | 60 | 17.2 | 50074 | 2026-01-06 12:41:15 | MASTER- | (04h 24m 20.56s , +60d 44m 34.6s) | C | 60 | 17.0 | 50074 | 2026-01-06 12:41:15 | MASTER- | (04h 26m 06.14s , +60d 10m 24.1s) | C | 60 | 17.5 | 50393 | 2026-01-06 12:46:34 | MASTER- | (04h 53m 57.37s , +56d 22m 05.4s) | C | 60 | 17.6 | 50393 | 2026-01-06 12:46:34 | MASTER- | (04h 52m 21.16s , +56d 56m 07.4s) | C | 60 | 17.2 | 50819 | 2026-01-06 12:53:40 | MASTER- | (04h 26m 00.27s , +60d 10m 01.0s) | C | 60 | 17.5 | 50819 | 2026-01-06 12:53:40 | MASTER- | (04h 24m 16.25s , +60d 44m 10.6s) | C | 60 | 17.0 | 51136 | 2026-01-06 12:58:57 | MASTER- | (04h 53m 56.14s , +56d 21m 50.3s) | C | 60 | 17.3 | 51136 | 2026-01-06 12:58:58 | MASTER- | (04h 52m 21.74s , +56d 55m 48.1s) | C | 60 | 16.9 | 51568 | 2026-01-06 13:06:09 | MASTER- | (04h 26m 02.40s , +60d 10m 25.4s) | C | 60 | 16.5 | 51568 | 2026-01-06 13:06:09 | MASTER- | (04h 24m 20.55s , +60d 44m 28.7s) | C | 60 | 15.9 | 51886 | 2026-01-06 13:11:28 | MASTER- | (04h 53m 50.30s , +56d 22m 14.7s) | C | 60 | 15.8 | 51886 | 2026-01-06 13:11:28 | MASTER- | (04h 52m 17.69s , +56d 56m 07.6s) | C | 60 | 15.6 | 52310 | 2026-01-06 13:18:31 | MASTER- | (04h 25m 59.19s , +60d 10m 12.1s) | C | 60 | 15.8 | 52310 | 2026-01-06 13:18:31 | MASTER- | (04h 24m 19.17s , +60d 44m 11.3s) | C | 60 | 15.4 | 61752 | 2026-01-06 15:55:53 | MASTER-Tunka | (04h 32m 04.80s , +60d 25m 18.6s) | C | 60 | 17.8 | 61752 | 2026-01-06 15:55:53 | MASTER-Tunka | (04h 30m 52.16s , +60d 33m 07.6s) | C | 60 | 17.1 | Coadd 90891 | 2026-01-07 00:01:32 | MASTER-Kislovodsk | (04h 53m 24.59s , +56d 38m 40.5s) | C | 60 | 17.3 | 102412 | 2026-01-07 03:13:34 | MASTER-Kislovodsk | (04h 39m 35.25s , +56d 05m 19.5s) | C | 60 | 16.3 | 102412 | 2026-01-07 03:13:34 | MASTER-Kislovodsk | (04h 32m 17.01s , +56d 24m 49.6s) | C | 60 | 16.8 | 102515 | 2026-01-07 03:15:16 | MASTER-Kislovodsk | (04h 31m 43.02s , +57d 59m 37.8s) | C | 60 | 16.5 | 102515 | 2026-01-07 03:15:16 | MASTER-Kislovodsk | (04h 24m 00.92s , +58d 19m 01.2s) | C | 60 | 16.9 | 102662 | 2026-01-07 03:17:43 | MASTER-Kislovodsk | (04h 23m 11.61s , +59d 52m 00.8s) | C | 60 | 16.7 | 102662 | 2026-01-07 03:17:44 | MASTER-Kislovodsk | (04h 15m 06.89s , +60d 11m 20.5s) | C | 60 | 17.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43347. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41437] GRB 260105B: Fermi GBM Detection
by GCN Circulars 07 Jan '26

07 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43346 SUBJECT: GRB 260105B: Fermi GBM Detection DATE: 26/01/07 00:08:46 GMT FROM: Matt Godwin <msg0028(a)uah.edu> Matt Godwin (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 23:21:36.55 UT on 05 January 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260105B (trigger 789348101/260105973). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 259.71, Dec = 1.74 (J2000 degrees, equivalent to J2000 17h 18m, +1d 44'), with a statistical uncertainty of 2.03 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]). The angle from the Fermi LAT boresight is 68 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 11 s (50-300 keV). The time-averaged spectrum from T0-1.9 to T0+12.5 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.96 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 232 +/- 2 keV. The event fluence (10-1000 keV) in this time interval is (8 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.4 s in the 10-1000 keV band is 156 +/- 2 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 178 +/- 2 keV, alpha = -0.83 +/- 0.01 and beta = -2.19 +/- 0.03. 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/43346. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41436] EP260105a: FTW optical observations
by GCN Circulars 06 Jan '26

06 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43345 SUBJECT: EP260105a: FTW optical observations DATE: 26/01/06 15:03:15 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann(a)physik.lmu.de> Malte Busmann, Jule Augustin, Mitra Maleki (LMU), Xander J. Hall, Brendan O'Connor (CMU), Daniel Gruen (LMU), and Antonella Palmese (CMU) report: We observed the 90% FXT localization of EP260105a (Zhou et al., GCNs 43327 and 43333) with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r and i-band simultaneously for 10 x 180 s starting at 2026-01-06T02:04:38 UT (0.84 days after the trigger). We performed difference imaging with templates from the DESI Legacy Surveys and did not detect any uncatalogued sources to a 3-sigma upper limit of r > 22.7 AB mag. The non-detection is consistent with the reports by Lipunov et al. (GCN 43328), Corcoran et al. (GCN 43332), and Li et al (GCN 43337). The magnitude is calibrated against the PS1 catalog and not corrected for Galactic extinction. We thank Christoph Ries from the Wendelstein Observatory for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43345. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41435] EP260104: FTW optical observations
by GCN Circulars 06 Jan '26

06 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43344 SUBJECT: EP260104: FTW optical observations DATE: 26/01/06 15:02:43 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann(a)physik.lmu.de> Malte Busmann, Jule Augustin, Mitra Maleki (LMU), Xander J. Hall, Brendan O'Connor (CMU), Daniel Gruen (LMU), and Antonella Palmese (CMU) report: We observed the 90% WXT localization of EP260104a (Zhou et al., GCN 43330) with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r and i-band simultaneously for 10 x 180 s starting at 2026-01-06T01:09:48 UT (1.6 days after the trigger). We performed difference imaging with templates from the DESI Legacy Surveys and did not detect any uncatalogued sources to a 3-sigma upper limit of r > 21.5 AB mag. The non-detection is consistent with the report by Lipunov et al. (GCN 43331). The magnitude is calibrated against the PS1 catalog and not corrected for Galactic extinction. We thank Christoph Ries from the Wendelstein Observatory for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43344. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41434] GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
by GCN Circulars 06 Jan '26

06 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43343 SUBJECT: GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973) DATE: 26/01/06 08:43:43 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 789348101 at 23:21:36 on 05 Jan. 2026 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 258.7 deg Decl.(2000.0) = 7.9 deg The 1 sigma statistical error radius is 2.1 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260105973/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260105973/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260105973/json View this GCN Circular online at https://gcn.nasa.gov/circulars/43343. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41433] GRB 260105A: SVOM/GRM observation
by GCN Circulars 06 Jan '26

06 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43342 SUBJECT: GRB 260105A: SVOM/GRM observation DATE: 26/01/06 08:30:22 GMT FROM: Yue Wang <m18509381757(a)163.com> SVOM/GRM team: Yue Wang, Chen-Wei Wang, Hao-Xuan Guo, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Sebastien Guillot (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered on-ground by GRB 260105A at 2026-01-05T22:47:16.000 (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43335). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a T90 of 69 +16/-12 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260105A.png In addition, the position of this burst, as determined by Fermi/GBM (RA = 64.5, Dec = 55.5, Error = 3.3, GCN #43335), is located at about 85 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-7 to T0+83 s is best fitted by a power law function. The power law index is -1.64 +0.08/-0.07. The event fluence (10-1000 keV) in this time interval is (1.85 +0.20/-0.20)E-05 erg/cm^2. 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Yue Wang (IHEP) (yuewang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43342. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41432] GRB 260105B: SVOM/GRM observation
by GCN Circulars 06 Jan '26

06 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43341 SUBJECT: GRB 260105B: SVOM/GRM observation DATE: 26/01/06 07:25:39 GMT FROM: Yue Wang <m18509381757(a)163.com> SVOM/GRM team: Yue Wang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Sebastien Guillot (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 260105B (SVOM trigger reference: sb26010502) at 2026-01-05T23:21:37.000 (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43336). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 6.8 +1.8/-1.4 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260105B.png In addition, the position of this burst, as determined by Fermi/GBM (RA = 259.7, Dec = 1.7, Error = 2.0, GCN #43336), is located at about 91 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-1 to T0+7 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.61 +0.12/-0.13 and the cutoff energy, parameterized as Epeak, is 177 +15/-13 keV. The event fluence (10-1000 keV) in this time interval is (9.34+0.47/-0.44)E-06 erg/cm^2. The 1s peak spectrum, measured from T0-1.5 to T0+2.5 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -0.81 +0.15/-0.17 and the cutoff energy, parameterized as Epeak, is 242 +45/-33 keV. The flux (10-1000 keV) in this time interval is (2.53 +0.22/-0.20)E-06 erg/cm^2/s. The localization of GRB 260105B in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260105B_amati.png The localization of GRB 260105B in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260105B_yonetoku.png 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Yue Wang (IHEP) (yuewang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43341. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41431] The EP-WXT trigger 01709251028 is likely a flaring star
by GCN Circulars 06 Jan '26

06 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43340 SUBJECT: The EP-WXT trigger 01709251028 is likely a flaring star DATE: 26/01/06 04:02:15 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> G. J. Yang, M. J. Liu, X. X. Sun, C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709251028 at the time of 2026-01-05T18:47:36, is likely a stellar flare associated with ET Leo. The estimated flux of the flare is around 1.8e-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 2.4e+32 erg/s. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43340. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41430] FRB 20251229A: COLIBRÍ optical upper limits
by GCN Circulars 06 Jan '26

06 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43339 SUBJECT: FRB 20251229A: COLIBRÍ optical upper limits DATE: 26/01/06 04:00:53 GMT FROM: globus(a)astro.unam.mx Noémie Globus (UNAM), Jean-Luc Atteia (IRAP), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (NYUAD), Camila Angulo (UNAM), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Nikos Mandarakas (LAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM), report: We imaged the field of FRB 20251229A (Mulyk et al., GCN Circ. 43334), using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-06 02:08 to 02:42 UTC and obtained 29 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and was not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the uncertainty region (Mulyk et al., GCN Circ. 43334) down to the following preliminary 5-sigma limits: r > 22.99, z > 21.88. 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/43339. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41429] Fermi GRB 260105B: Global MASTER-Net observations report
by GCN Circulars 06 Jan '26

06 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43338 SUBJECT: Fermi GRB 260105B: Global MASTER-Net observations report DATE: 26/01/06 03:15:41 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 [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 260105B ( Fermi GBM team, GCN 43336) errorbox 11975 sec after notice time and 12000 sec after trigger time at 2026-01-06 02:41:37 UT, with upper limit up to 15.8 mag. The observations began at zenith distance = 76 deg. The sun altitude is -21.3 deg. The galactic latitude b = 21 deg., longitude l = 24 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3096822 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 12031 | 2026-01-06 02:41:37 | MASTER-Kislovodsk | (17h 22m 13.00s , +01d 20m 58.9s) | C | 60 | 15.1 | 12031 | 2026-01-06 02:41:37 | MASTER-Kislovodsk | (17h 26m 08.53s , +00d 57m 53.4s) | C | 60 | 15.2 | 12121 | 2026-01-06 02:43:08 | MASTER-Kislovodsk | (17h 10m 08.21s , +01d 21m 09.6s) | C | 60 | 14.9 | 12128 | 2026-01-06 02:43:14 | MASTER-Kislovodsk | (17h 14m 04.52s , +00d 58m 08.3s) | C | 60 | 15.3 | 12226 | 2026-01-06 02:44:52 | MASTER-Kislovodsk | (17h 11m 25.82s , +03d 16m 06.5s) | C | 60 | 15.1 | 12226 | 2026-01-06 02:44:52 | MASTER-Kislovodsk | (17h 15m 22.74s , +02d 53m 06.6s) | C | 60 | 15.5 | 12321 | 2026-01-06 02:46:27 | MASTER-Kislovodsk | (17h 23m 33.99s , +03d 14m 28.1s) | C | 60 | 14.8 | 12322 | 2026-01-06 02:46:28 | MASTER-Kislovodsk | (17h 27m 29.97s , +02d 51m 24.2s) | C | 60 | 15.0 | 12414 | 2026-01-06 02:48:00 | MASTER-Kislovodsk | (17h 13m 55.29s , +05d 08m 02.6s) | C | 60 | 15.4 | 12414 | 2026-01-06 02:48:00 | MASTER-Kislovodsk | (17h 17m 53.06s , +04d 45m 03.0s) | C | 60 | 15.5 | 12510 | 2026-01-06 02:49:36 | MASTER-Kislovodsk | (17h 10m 02.76s , -00d 33m 18.0s) | C | 60 | 14.2 | 12510 | 2026-01-06 02:49:36 | MASTER-Kislovodsk | (17h 13m 58.54s , -00d 56m 23.5s) | C | 60 | 15.1 | 12604 | 2026-01-06 02:51:10 | MASTER-Kislovodsk | (17h 21m 59.11s , -00d 32m 11.6s) | C | 60 | 15.0 | 12605 | 2026-01-06 02:51:11 | MASTER-Kislovodsk | (17h 25m 53.95s , -00d 55m 21.3s) | C | 60 | 15.3 | 12703 | 2026-01-06 02:52:49 | MASTER-Kislovodsk | (17h 26m 04.82s , +05d 09m 14.6s) | C | 60 | 15.8 | 12812 | 2026-01-06 02:54:38 | MASTER-Kislovodsk | (17h 03m 25.00s , +02d 54m 15.4s) | C | 60 | 13.8 | 13208 | 2026-01-06 03:01:14 | MASTER-Kislovodsk | (17h 34m 09.17s , +01d 21m 41.1s) | C | 60 | 13.3 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43338. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41428] EP260105a: SVOM/VT optical upperlimit
by GCN Circulars 06 Jan '26

06 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43337 SUBJECT: EP260105a: SVOM/VT optical upperlimit DATE: 26/01/06 03:03:52 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, Y. Xu, X. H. Han, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observation on the fast X-ray transient EP260105a (Zhou et al., GCN 43327). The observation started on 2026-01-05T07:51:04 UT (i.e. 2.06 hour post trigger) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. Inside the error box of the EP-FXT (Zhou et al., GCN 43333) we did not detect any new uncatalogued source, which was consistent with the non detections reported by MASTER-Net (Lipunov et al., GCN 43328) and LCO (Corcoran et al., GCN 43332). The 3 sigma limit magnitudes are derived as below: Mid time | Band | Exposure Time | 3 sigma limit magnitude 4.68 hour VT_B 30*100 sec > 23.5 mag 4.68 hour VT_R 30*100 sec > 23.5 mag 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/43337. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41427] GRB 260105B: Fermi GBM Final Real-time Localization
by GCN Circulars 05 Jan '26

05 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43336 SUBJECT: GRB 260105B: Fermi GBM Final Real-time Localization DATE: 26/01/05 23:32:13 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 23:21:36 UT on 5 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260105B (trigger 789348101.546602 / 260105973). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 259.7, Dec = 1.7 (J2000 degrees, equivalent to J2000 17h 18m, 1d 42'), with a statistical uncertainty of 2.0 degrees. The angle from the Fermi LAT boresight is 68.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260105973/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260105973/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260105973/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43336. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41426] GRB 260105A: Fermi GBM Final Real-time Localization
by GCN Circulars 05 Jan '26

05 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43335 SUBJECT: GRB 260105A: Fermi GBM Final Real-time Localization DATE: 26/01/05 22:57:42 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 22:47:11 UT on 5 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260105A (trigger 789346036.667754 / 260105949). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 64.5, Dec = 55.5 (J2000 degrees, equivalent to J2000 04h 17m, 55d 30'), with a statistical uncertainty of 3.3 degrees. The angle from the Fermi LAT boresight is 99.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260105949/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260105949/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260105949/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43335. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41425] FRB 20251229A: A potentially hyperactive repeating fast radio burst source
by GCN Circulars 05 Jan '26

05 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43334 SUBJECT: FRB 20251229A: A potentially hyperactive repeating fast radio burst source DATE: 26/01/05 17:53:25 GMT FROM: nicole.mulyk(a)mail.mcgill.ca Nicole Mulyk (McGill University, Trottier Space Institute) on behalf of the CHIME/FRB Collaboration: The CHIME/FRB Collaboration reports the detection of three bursts from a new repeating fast radio burst (FRB) source over the last week, with TNS designation FRB 20251229A. These bursts were detected on 2025-12-29 22:00:58, 2026-01-01 21:56:03, and 2026-01-03 21:53:36 UTC (400 MHz, topocentric). The first two detections were streamed through our VOEvents service. The third burst did not trigger a VOEvents notification as its signal-to-noise ratio was below the trigger threshold of 12 (see table below; Abbott et al. 2025). The rapid succession of these bursts in combination with the low declination of the source (+16 degrees; see below), and low CHIME exposure of only ~5 minutes per day (see note below), provides evidence of high activity. Additionally, this FRB source has a relatively low DM of 192.145 +/- 0.013 pc/cm^3, calculated by structure-maximizing the time profile using the highest signal-to-noise burst (Seymour, Michilli, & Pleunis 2019). The expected Galactic contribution along this line of sight is 93.6 or 75.3 pc/cm^3 from NE2001 (Cordes & Lazio 2002) or YMW16 (Yao, Manchester & Wang 2017), respectively. The large disparity between the predicted maximum Galactic DM from both models, and the much larger source DM, strongly suggests this is an extragalactic source. Assuming an average contribution of the intergalactic medium to the DM (Macquart et al. 2020), we expect the FRB’s redshift to be within ~0.1. Initial analysis of the raw voltage data of the brightest event from 2026-01-01 provides a best-fit localization, of RA (J2000): 20h41m26.3s +/- 1.2s, Dec (J2000): 16°01’24” +/- 18”, with errors quoted at 1-sigma uncertainty (Michilli et al. 2021). Using the raw voltage data for the 2026-01-01 burst, we obtain a peak flux of 30 +/- 3 Jy and a 400 to 800 MHz band-averaged fluence of 160 +/- 16 Jy ms (CHIME/FRB Collaboration 2024). We have attached the waterfall plot for the 2026-01-01 burst in the link at the end of this ATel. Due to the potentially high repetition rate and relative proximity of the source, we encourage multi-wavelength follow-up. Note: This is compared to a “typical” daily exposure of ~15 minutes near zenith (see also Fig. 5 of CHIME/FRB Collaboration 2021, ApJS, 257, 59). Topocentric Burst 400 MHz Arrival Time (UTC) | Detection Signal to Noise (S/N) Ratio : 2025-12-29 22:00:58 | 13.36 2026-01-01 21:56:03 | 47.90 2026-01-03 21:53:36 | 11.25 Waterfall plot: https://storage.googleapis.com/chimefrb-dev.appspot.com/FRB20251229A/FRB202… View this GCN Circular online at https://gcn.nasa.gov/circulars/43334. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41424] EP260105a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 05 Jan '26

05 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43333 SUBJECT: EP260105a: refined analysis of the EP-WXT and EP-FXT observations DATE: 26/01/05 14:30:43 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO, CAS), Z. C. Zou (NJU), D. Y. Li, Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260105a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Zhou et al., GCN 43327). The refined analysis of the WXT data shows that the event started at T0=2026-01-05T05:47:50 (UTC) and lasted for 100 seconds. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 2.4 x 10^20 cm^-2 and a photon index of 0.89(-0.65/+0.67). The derived average unabsorbed 0.5-4 keV flux is (1.1+/-0.5) x 10^(-9) erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously at 2026-01-05T05:52:07 (UTC), about 4.3 minutes after T0. The exposure time of this observation is 2698s. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 181.0148, DEC = 22.7092 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent with the WXT position. A significant decay was detected in the light curve during the initial phase of FXT observation. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 2.4 x 10^20 cm^-2 and a photon index of 2.07 (-0.56/+0.58). The derived average unabsorbed 0.5-10 keV flux is 4.2 (-1.7/+2.1) x 10^(-13) erg/s/cm^2. No optical counterpart of EP260105a has been detected so far (Lipunov et al., GCN 43328; Corcoran et al., GCN 43332) , and further mutil-band follow-up observations are encouraged to explore the nature of EP260105a. Another ToO observation with EP-FXT is being performed start from 2026-01-05T12:31:46 (UTC). Further information will be updated when the telemetry data is received. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43333. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41423] EP260105a: LCO Optical Upper limit
by GCN Circulars 05 Jan '26

05 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43332 SUBJECT: EP260105a: LCO Optical Upper limit DATE: 26/01/05 11:05:43 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> G. Corcoran (UCD), J. Quirola-Vasquez (Radboud), F. E. Bauer (SSI and UTA), A. Levan (Radboud), A. Martin-Carrillo (UCD), P.G. Jonker (Radboud) report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP260105a (Zhou et al. GCN 43327) using the Las Cumbres Observatory (LCO) network at the Cerro Tololo Inter-American Observatory node using the Sinistro instrument on the 1m telescope. A series of 6x300s exposures were taken in the SDSS-r filter starting at 2026-01-05T07:10:04.556 UTC (1.326 hours after the WXT trigger). We do not detect any sources within the EP/FXT uncertainty region. From the stacked image we obtain a 3 sigma upper limit of: r > 21.5. This upper limit is in AB magnitudes, was calibrated using nearby stars from the Pan-STARRS catalog and is not corrected for Galactic extinction. Our observations are consistent with the upper limits reported by Lipunov et al. GCN 43328. View this GCN Circular online at https://gcn.nasa.gov/circulars/43332. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41422] EP260104a: Global MASTER-Net observations report
by GCN Circulars 05 Jan '26

05 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43331 SUBJECT: EP260104a: Global MASTER-Net observations report DATE: 26/01/05 09:18:34 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 [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP260104a ( EP Team et al., GCN 43330) errorbox 56335 sec after trigger time at 2026-01-05 02:04:39 UT, with upper limit up to 15.3 mag. The observations began at zenith distance = 28 deg. The sun altitude is -27.9 deg. The galactic latitude b = 73 deg., longitude l = 251 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3096369 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 56366 | 2026-01-05 02:04:39 | MASTER-Kislovodsk | (11h 56m 25.18s , +14d 49m 37.7s) | C | 60 | 15.3 | 80735 | 2026-01-05 08:49:48 | MASTER- | (11h 58m 24.52s , +15d 34m 21.5s) | C | 180 | 17.0 | 81514 | 2026-01-05 09:02:47 | MASTER- | (11h 58m 27.43s , +15d 32m 44.3s) | C | 180 | 17.9 | 81514 | 2026-01-05 09:02:47 | MASTER- | (11h 59m 39.45s , +14d 59m 25.9s) | C | 180 | 17.9 | 81896 | 2026-01-05 09:09:09 | MASTER- | (11h 59m 35.99s , +14d 58m 57.1s) | C | 180 | 17.3 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43331. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41421] EP260104a: Einstein Probe detection of a fast X-ray transient
by GCN Circulars 05 Jan '26

05 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43330 SUBJECT: EP260104a: Einstein Probe detection of a fast X-ray transient DATE: 26/01/05 08:41:44 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO, CAS), Z. C. Zou (NJU), J. P. Chen (SYSU), Y. J. Yi (BNU), D. Y. Li, C. L. Guo, Z. X. Ling, Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260104a. The transient triggered EP-WXT (ID: 01709250979) at 2026-01-04T10:25:44 (UTC). The WXT position of the source is R.A. = 178.535 deg, DEC = 16.491 deg (J2000) with an uncertainty of 2.8 arcmin in radius (90% C.L. statistical and systematic). Since EP260104a was triggered in SAA region, no autonomous follow-up observation was performed. We analyzed the telemetry data, and the 0.5-4 keV rate light curve shows a single pulse lasting for about 150 seconds. The absorbed powerlaw model with a fixed Galactic column density of Hydrogen of 4.57 x 10^20 cm^-2 was adopted to fit the average WXT spectrum. The best-fitted photon index is 2.44(+1.26/-0.96), the average flux (0.5-4 keV) is (2.4+/-1.1) x 10^-10 erg s^-1 cm^-2, and no additional absorption is required. All uncertainties are reported in 90% C.L. We have arranged X-ray follow-up observations and will update the information upon receiving the data. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43330. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41420] GRB 260101A: COLIBRÍ optical upper limits
by GCN Circulars 05 Jan '26

05 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43329 SUBJECT: GRB 260101A: COLIBRÍ optical upper limits DATE: 26/01/05 06:51:12 GMT FROM: Jean-Luc Atteia at IRAP <jean-luc.atteia(a)irap.omp.eu> Jean-Luc Atteia (IRAP), Noémie Globus (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Dalya Akl (NYUAD), Camila Angulo (UNAM), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Nikos Mandarakas (LAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM), report: We imaged the field of GRB 260101A (Fermi GBM team, GCN Circ. 43284; Cenko et al., GCN Circ. 43285; Pérez-Fournon et al., GCN Circ. 43286; de Ugarte Postigo et al., GCN Circ. 43287; Beardmore et al., GCN Circ. 43289; Lipunov et al., GCN Circ. 43290; D'Avanzo et al., GCN Circ. 43291; SVOM/GRM team et al., GCN Circ. 43292; Saccardi et al., GCN Circ. 43293; Wang et al., GCN Circ. 43294; Hristov et al., GCN Circ. 43297; Globus et al., GCN Circ. 43312; Klinger et al., GCN Circ. 43318) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-05 03:38 to 05:46 UTC (98.7 hours to 100.8 hours after the trigger) and obtained 94 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In our stacked images, the previously detected afterglow (Cenko et al., GCN Circ. 43285; Pérez-Fournon et al., GCN Circ. 43286; Globus et al., GCN Circ. 43312; Klinger et al., GCN Circ. 43318) has faded beyond our 5-sigma detection limit: r > 22.96, z > 22.42. 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/43329. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41419] EP260105a: Global MASTER-Net observations report
by GCN Circulars 05 Jan '26

05 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43328 SUBJECT: EP260105a: Global MASTER-Net observations report DATE: 26/01/05 06:36:38 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 [1] located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP260105a ( EP Team et al., GCN 43327) errorbox 302 sec after trigger time at 2026-01-05 05:55:32 UT, with upper limit up to 17.7 mag. The observations began at zenith distance = 76 deg. The sun altitude is -33.4 deg. The galactic latitude b = 79 deg., longitude l = 235 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3096319 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 333 | 2026-01-05 05:55:32 | MASTER-OAFA | (12h 04m 39.81s , +22d 45m 13.6s) | C | 60 | 17.0 | 404 | 2026-01-05 05:56:38 | MASTER-OAFA | (12h 04m 39.97s , +22d 45m 19.5s) | C | 70 | 17.2 | 490 | 2026-01-05 05:57:55 | MASTER-OAFA | (12h 04m 40.18s , +22d 45m 26.3s) | C | 90 | 17.3 | 597 | 2026-01-05 05:59:31 | MASTER-OAFA | (12h 04m 40.39s , +22d 45m 34.0s) | C | 110 | 17.3 | 723 | 2026-01-05 06:01:28 | MASTER-OAFA | (12h 04m 40.60s , +22d 45m 42.6s) | C | 130 | 17.4 | 874 | 2026-01-05 06:03:44 | MASTER-OAFA | (12h 04m 40.84s , +22d 45m 52.0s) | C | 160 | 17.5 | 991 | 2026-01-05 06:06:30 | MASTER-OAFA | (12h 04m 41.03s , +22d 45m 59.4s) | C | 60 | 17.5 | 1056 | 2026-01-05 06:07:36 | MASTER-OAFA | (12h 04m 41.10s , +22d 46m 03.1s) | C | 60 | 17.5 | 1121 | 2026-01-05 06:08:41 | MASTER-OAFA | (12h 04m 41.18s , +22d 46m 07.0s) | C | 60 | 17.5 | 1188 | 2026-01-05 06:09:47 | MASTER-OAFA | (12h 04m 41.28s , +22d 46m 10.9s) | C | 60 | 17.5 | 1253 | 2026-01-05 06:10:53 | MASTER-OAFA | (12h 04m 41.36s , +22d 46m 14.7s) | C | 60 | 17.6 | 1319 | 2026-01-05 06:11:58 | MASTER-OAFA | (12h 04m 41.43s , +22d 46m 18.6s) | C | 60 | 17.7 | 1385 | 2026-01-05 06:13:05 | MASTER-OAFA | (12h 04m 41.51s , +22d 46m 22.1s) | C | 60 | 17.7 | 1451 | 2026-01-05 06:14:10 | MASTER-OAFA | (12h 04m 41.60s , +22d 46m 25.6s) | C | 60 | 17.6 | 1516 | 2026-01-05 06:15:16 | MASTER-OAFA | (12h 04m 41.63s , +22d 46m 29.0s) | C | 60 | 17.7 | 1582 | 2026-01-05 06:16:22 | MASTER-OAFA | (12h 04m 41.67s , +22d 46m 32.3s) | C | 60 | 17.7 | 1648 | 2026-01-05 06:17:27 | MASTER-OAFA | (12h 04m 41.73s , +22d 46m 35.5s) | C | 60 | 17.7 | 1714 | 2026-01-05 06:18:33 | MASTER-OAFA | (12h 04m 41.76s , +22d 46m 38.8s) | C | 60 | 17.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43328. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41418] EP260105a: Einstein Probe detection of an X-ray transient
by GCN Circulars 05 Jan '26

05 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43327 SUBJECT: EP260105a: Einstein Probe detection of an X-ray transient DATE: 26/01/05 06:17:04 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO, CAS), Z. C. Zou (NJU), D. Y. Li, Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260105a. The transient triggered EP-WXT (ID: 01709250995) at 2026-01-05T05:50:30 (UTC). The WXT position of the source is R.A. = 181.036 deg, DEC = 22.723 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 181.0158 deg, DEC = 22.7089 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43327. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41417] GRB 260103A: Insight-HXMT/HE detection
by GCN Circulars 05 Jan '26

05 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43326 SUBJECT: GRB 260103A: Insight-HXMT/HE detection DATE: 26/01/05 05:48:29 GMT FROM: Xinghao Luo at IHEP <2952704891(a)qq.com> Xing-hao Luo, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2026-01-03T01:46:53.800 (T0), Insight-HXMT/HE detected the long burst GRB 260103A, which is also detected by SVOM/GRM (Chen-Wei Wang et.al., GCN #43314) , GECAM-B (Xing-Hao Luo et.al., GCN #43317) The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 4.6 +1.8/-1.0 s. The 1s peak rate, measured from T0-0.25 s, is 1848 cnts/sec. Insight-HXMT/HE detected a total of 4704 counts form this burst. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260103A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 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/43326. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41416] GRB 260104A: COLIBRÍ optical upper limits
by GCN Circulars 05 Jan '26

05 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43325 SUBJECT: GRB 260104A: COLIBRÍ optical upper limits DATE: 26/01/05 04:32:13 GMT FROM: globus(a)astro.unam.mx Noémie Globus (UNAM), Jean-Luc Atteia (IRAP), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Dalya Akl (NYUAD), Camila Angulo (UNAM), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Nikos Mandarakas (LAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM), report: We imaged the field of GRB 260104A (Caputo et al., GCN Circ. 43315; Evans et al., GCN Circ. 43319; Kennea et al., GCN Circ. 43320), using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-05 at 01:46 to 02:44 UTC (from 20.16 to 21.12 hr after the trigger) and obtained 41 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ ASU pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and was not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the XRT uncertainty region (Caputo et al., GCN Circ. 43315) down to the following 5-sigma limit: r > 21.90, z > 20.96. 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/43325. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41415] GRB 260104C: Fermi GBM Final Real-time Localization
by GCN Circulars 05 Jan '26

05 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43324 SUBJECT: GRB 260104C: Fermi GBM Final Real-time Localization DATE: 26/01/05 00:08:31 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 23:57:57 UT on 4 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260104C (trigger 789263882.41794 / 260104999). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 312.7, Dec = -26.1 (J2000 degrees, equivalent to J2000 20h 50m, -26d 06'), with a statistical uncertainty of 9.3 degrees. The angle from the Fermi LAT boresight is 101.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260104999/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260104999/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260104999/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43324. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41414] Fermi GRB 260104B: Global MASTER-Net observations report
by GCN Circulars 04 Jan '26

04 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43323 SUBJECT: Fermi GRB 260104B: Global MASTER-Net observations report DATE: 26/01/04 18:30:45 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-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 260104B ( Fermi GBM team, GCN 43316) errorbox 41510 sec after notice time and 41543 sec after trigger time at 2026-01-04 17:22:21 UT, with upper limit up to 16.9 mag. The observations began at zenith distance = 76 deg. The sun altitude is -38.2 deg. The galactic latitude b = -38 deg., longitude l = 231 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3095661 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 2242 | 2026-01-04 06:26:49 | MASTER- | (04h 57m 27.88s , -27d 20m 35.2s) | C | 60 | 16.2 | 2311 | 2026-01-04 06:27:58 | MASTER- | (05h 06m 32.28s , -27d 20m 26.9s) | C | 60 | 15.5 | 2523 | 2026-01-04 06:31:30 | MASTER- | (04h 39m 55.89s , -27d 23m 49.4s) | C | 60 | 15.2 | 2666 | 2026-01-04 06:33:53 | MASTER- | (04h 52m 07.50s , -25d 29m 24.1s) | C | 60 | 16.5 | 2666 | 2026-01-04 06:33:53 | MASTER- | (04h 53m 11.08s , -26d 03m 29.8s) | C | 60 | 16.5 | 2736 | 2026-01-04 06:35:03 | MASTER- | (05h 01m 14.80s , -25d 28m 03.2s) | C | 60 | 16.9 | 2736 | 2026-01-04 06:35:03 | MASTER- | (05h 02m 18.57s , -26d 02m 09.0s) | C | 60 | 16.7 | 2808 | 2026-01-04 06:36:15 | MASTER- | (04h 52m 28.51s , -31d 45m 31.6s) | C | 60 | 16.2 | 2808 | 2026-01-04 06:36:15 | MASTER- | (04h 51m 23.06s , -31d 11m 26.1s) | C | 60 | 16.2 | 2878 | 2026-01-04 06:37:25 | MASTER- | (05h 00m 58.96s , -31d 08m 33.7s) | C | 60 | 16.7 | 2878 | 2026-01-04 06:37:25 | MASTER- | (05h 02m 04.41s , -31d 42m 39.1s) | C | 60 | 16.4 | 2948 | 2026-01-04 06:38:36 | MASTER- | (04h 57m 21.81s , -27d 22m 07.2s) | C | 60 | 17.0 | 3018 | 2026-01-04 06:39:45 | MASTER- | (05h 07m 35.96s , -27d 54m 01.5s) | C | 60 | 15.6 | 3229 | 2026-01-04 06:43:16 | MASTER- | (04h 40m 01.43s , -27d 26m 00.8s) | C | 60 | 13.6 | 3370 | 2026-01-04 06:45:37 | MASTER- | (04h 53m 12.96s , -26d 04m 26.6s) | C | 60 | 14.2 | 3440 | 2026-01-04 06:46:47 | MASTER- | (05h 02m 17.23s , -26d 01m 36.0s) | C | 60 | 14.9 | 3864 | 2026-01-04 06:53:51 | MASTER- | (04h 55m 49.13s , -29d 51m 20.9s) | C | 60 | 14.7 | 3934 | 2026-01-04 06:55:01 | MASTER- | (04h 41m 00.45s , -28d 01m 07.5s) | C | 60 | 15.3 | 5582 | 2026-01-04 07:22:29 | MASTER- | (04h 49m 02.68s , -27d 27m 05.8s) | C | 60 | 14.9 | 5722 | 2026-01-04 07:24:49 | MASTER- | (05h 02m 07.90s , -26d 07m 35.4s) | C | 60 | 15.9 | 5794 | 2026-01-04 07:26:01 | MASTER- | (04h 51m 20.48s , -31d 16m 47.1s) | C | 60 | 15.7 | 5871 | 2026-01-04 07:27:18 | MASTER- | (05h 01m 55.81s , -31d 48m 03.9s) | C | 60 | 15.6 | 5871 | 2026-01-04 07:27:18 | MASTER- | (05h 00m 51.97s , -31d 14m 17.1s) | C | 60 | 15.8 | 5941 | 2026-01-04 07:28:29 | MASTER- | (04h 58m 23.48s , -28d 02m 10.3s) | C | 60 | 15.6 | 5941 | 2026-01-04 07:28:29 | MASTER- | (04h 57m 21.23s , -27d 28m 23.1s) | C | 60 | 15.7 | 6011 | 2026-01-04 07:29:38 | MASTER- | (05h 07m 38.07s , -27d 59m 29.0s) | C | 60 | 15.8 | 6011 | 2026-01-04 07:29:38 | MASTER- | (05h 06m 35.66s , -27d 25m 41.7s) | C | 60 | 15.9 | 6225 | 2026-01-04 07:33:12 | MASTER- | (04h 39m 56.85s , -27d 30m 34.5s) | C | 60 | 15.5 | 6294 | 2026-01-04 07:34:21 | MASTER- | (04h 50m 03.23s , -28d 04m 16.2s) | C | 60 | 15.5 | 6294 | 2026-01-04 07:34:21 | MASTER- | (04h 49m 01.46s , -27d 30m 29.0s) | C | 60 | 15.6 | 6364 | 2026-01-04 07:35:31 | MASTER- | (04h 53m 11.10s , -26d 09m 47.5s) | C | 60 | 15.6 | 6364 | 2026-01-04 07:35:31 | MASTER- | (04h 52m 09.83s , -25d 36m 00.6s) | C | 60 | 15.7 | 6574 | 2026-01-04 07:39:01 | MASTER- | (05h 00m 52.79s , -31d 15m 18.7s) | C | 60 | 15.2 | 6715 | 2026-01-04 07:41:22 | MASTER- | (05h 06m 28.06s , -27d 26m 49.6s) | C | 60 | 15.8 | 7698 | 2026-01-04 07:57:45 | MASTER- | (04h 50m 05.69s , -28d 04m 34.9s) | C | 60 | 15.6 | 7768 | 2026-01-04 07:58:55 | MASTER- | (04h 53m 00.95s , -26d 11m 14.1s) | C | 60 | 15.9 | 7768 | 2026-01-04 07:58:55 | MASTER- | (04h 52m 00.40s , -25d 37m 26.0s) | C | 60 | 16.1 | 7838 | 2026-01-04 08:00:05 | MASTER- | (05h 02m 02.71s , -26d 09m 10.2s) | C | 60 | 16.2 | 41574 | 2026-01-04 17:22:21 | MASTER-Kislovodsk | (04h 50m 32.18s , -29d 17m 24.6s) | C | 60 | 16.5 | 41574 | 2026-01-04 17:22:21 | MASTER-Kislovodsk | (04h 45m 43.40s , -28d 54m 23.9s) | C | 60 | 16.0 | 41665 | 2026-01-04 17:23:52 | MASTER-Kislovodsk | (04h 51m 16.48s , -30d 47m 33.2s) | C | 60 | 15.9 | 41665 | 2026-01-04 17:23:52 | MASTER-Kislovodsk | (04h 56m 09.74s , -31d 10m 40.4s) | C | 60 | 16.4 | 41765 | 2026-01-04 17:25:32 | MASTER-Kislovodsk | (04h 40m 47.65s , -27d 00m 22.3s) | C | 60 | 16.1 | 41765 | 2026-01-04 17:25:32 | MASTER-Kislovodsk | (04h 45m 32.33s , -27d 23m 21.7s) | C | 60 | 16.6 | 41864 | 2026-01-04 17:27:11 | MASTER-Kislovodsk | (04h 42m 14.12s , -31d 12m 16.4s) | C | 60 | 16.5 | 41864 | 2026-01-04 17:27:11 | MASTER-Kislovodsk | (04h 37m 20.17s , -30d 49m 11.9s) | C | 60 | 16.0 | 41971 | 2026-01-04 17:28:58 | MASTER-Kislovodsk | (05h 04m 22.64s , -29d 18m 38.3s) | C | 60 | 16.5 | 41971 | 2026-01-04 17:28:58 | MASTER-Kislovodsk | (04h 59m 34.30s , -28d 55m 32.0s) | C | 60 | 16.1 | 42065 | 2026-01-04 17:30:32 | MASTER-Kislovodsk | (04h 32m 06.66s , -28d 53m 31.4s) | C | 60 | 16.1 | 42065 | 2026-01-04 17:30:32 | MASTER-Kislovodsk | (04h 36m 56.06s , -29d 16m 33.1s) | C | 60 | 16.7 | 42164 | 2026-01-04 17:32:11 | MASTER-Kislovodsk | (04h 48m 10.69s , -33d 06m 19.4s) | C | 60 | 16.7 | 42164 | 2026-01-04 17:32:11 | MASTER-Kislovodsk | (04h 43m 11.58s , -32d 43m 08.2s) | C | 60 | 16.0 | 42271 | 2026-01-04 17:33:58 | MASTER-Kislovodsk | (04h 54m 05.21s , -25d 28m 29.6s) | C | 60 | 16.7 | 42271 | 2026-01-04 17:33:58 | MASTER-Kislovodsk | (04h 49m 24.55s , -25d 05m 31.4s) | C | 60 | 16.3 | 43000 | 2026-01-04 17:46:07 | MASTER-Kislovodsk | (05h 02m 25.68s , -33d 04m 15.6s) | C | 60 | 16.2 | 43000 | 2026-01-04 17:46:07 | MASTER-Kislovodsk | (04h 57m 26.37s , -32d 41m 10.1s) | C | 60 | 15.7 | 43101 | 2026-01-04 17:47:48 | MASTER-Kislovodsk | (05h 05m 24.66s , -30d 48m 57.6s) | C | 60 | 16.0 | 43101 | 2026-01-04 17:47:48 | MASTER-Kislovodsk | (05h 10m 18.41s , -31d 12m 01.4s) | C | 60 | 16.4 | 43197 | 2026-01-04 17:49:24 | MASTER-Kislovodsk | (04h 23m 27.29s , -30d 47m 05.7s) | C | 60 | 16.3 | 43197 | 2026-01-04 17:49:24 | MASTER-Kislovodsk | (04h 28m 22.30s , -31d 10m 02.1s) | C | 60 | 16.4 | 43296 | 2026-01-04 17:51:03 | MASTER-Kislovodsk | (05h 07m 45.12s , -27d 01m 13.2s) | C | 60 | 16.3 | 43296 | 2026-01-04 17:51:03 | MASTER-Kislovodsk | (05h 12m 29.83s , -27d 24m 09.3s) | C | 60 | 16.9 | 43392 | 2026-01-04 17:52:39 | MASTER-Kislovodsk | (05h 02m 48.98s , -25d 05m 52.7s) | C | 60 | 16.4 | 43392 | 2026-01-04 17:52:39 | MASTER-Kislovodsk | (05h 07m 30.08s , -25d 28m 45.0s) | C | 60 | 16.9 | 43489 | 2026-01-04 17:54:16 | MASTER-Kislovodsk | (04h 28m 56.26s , -32d 41m 38.2s) | C | 60 | 16.1 | 43489 | 2026-01-04 17:54:16 | MASTER-Kislovodsk | (04h 33m 56.47s , -33d 04m 37.0s) | C | 60 | 16.8 | 43611 | 2026-01-04 17:56:18 | MASTER-Kislovodsk | (04h 45m 14.35s , -23d 12m 04.0s) | C | 60 | 16.5 | 43611 | 2026-01-04 17:56:18 | MASTER-Kislovodsk | (04h 49m 52.66s , -23d 34m 50.9s) | C | 60 | 16.9 | 43713 | 2026-01-04 17:58:00 | MASTER-Kislovodsk | (05h 13m 17.23s , -28d 55m 26.7s) | C | 60 | 15.9 | 43713 | 2026-01-04 17:58:00 | MASTER-Kislovodsk | (05h 18m 06.31s , -29d 18m 24.5s) | C | 60 | 16.5 | 43812 | 2026-01-04 17:59:39 | MASTER-Kislovodsk | (04h 18m 26.58s , -28d 53m 32.5s) | C | 60 | 16.5 | 43812 | 2026-01-04 17:59:39 | MASTER-Kislovodsk | (04h 23m 17.31s , -29d 16m 23.2s) | C | 60 | 16.7 | 43913 | 2026-01-04 18:01:20 | MASTER-Kislovodsk | (04h 23m 04.76s , -25d 05m 38.8s) | C | 60 | 16.4 | 43913 | 2026-01-04 18:01:20 | MASTER-Kislovodsk | (04h 27m 47.39s , -25d 28m 24.3s) | C | 60 | 16.7 | 44015 | 2026-01-04 18:03:02 | MASTER-Kislovodsk | (04h 58m 17.18s , -23d 12m 44.0s) | C | 60 | 16.5 | 44015 | 2026-01-04 18:03:02 | MASTER-Kislovodsk | (05h 02m 55.78s , -23d 35m 30.2s) | C | 60 | 16.9 | 44116 | 2026-01-04 18:04:43 | MASTER-Kislovodsk | (04h 49m 39.60s , -34d 36m 43.5s) | C | 60 | 16.3 | 44116 | 2026-01-04 18:04:43 | MASTER-Kislovodsk | (04h 54m 45.85s , -34d 59m 47.5s) | C | 60 | 16.6 | 44642 | 2026-01-04 18:13:29 | MASTER-Kislovodsk | (04h 35m 04.96s , -34d 37m 22.1s) | C | 60 | 16.2 | 44642 | 2026-01-04 18:13:29 | MASTER-Kislovodsk | (04h 40m 12.32s , -35d 00m 09.5s) | C | 60 | 16.5 | 44743 | 2026-01-04 18:15:10 | MASTER-Kislovodsk | (05h 11m 49.15s , -32d 42m 49.7s) | C | 60 | 15.9 | 44743 | 2026-01-04 18:15:10 | MASTER-Kislovodsk | (05h 16m 49.49s , -33d 05m 40.2s) | C | 60 | 16.3 | 44863 | 2026-01-04 18:17:10 | MASTER-Kislovodsk | (04h 32m 07.30s , -23d 10m 34.0s) | C | 60 | 16.6 | 44863 | 2026-01-04 18:17:10 | MASTER-Kislovodsk | (04h 36m 47.11s , -23d 33m 05.7s) | C | 60 | 16.9 | 44964 | 2026-01-04 18:18:51 | MASTER-Kislovodsk | (05h 04m 19.98s , -34d 35m 48.0s) | C | 60 | 15.1 | 44964 | 2026-01-04 18:18:51 | MASTER-Kislovodsk | (05h 09m 26.52s , -34d 58m 39.2s) | C | 60 | 15.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43323. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41413] Swift GRB 260104A: Global MASTER-Net observations report
by GCN Circulars 04 Jan '26

04 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43322 SUBJECT: Swift GRB 260104A: Global MASTER-Net observations report DATE: 26/01/04 16:48:28 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 [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 260104A ( R. Caputo et al., GCN 43315) errorbox 39152 sec after notice time and 39173 sec after trigger time at 2026-01-04 16:29:55 UT, with upper limit up to 15.0 mag. The observations began at zenith distance = 82 deg. The sun altitude is -28.6 deg. The galactic latitude b = -58 deg., longitude l = 36 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3095622 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 39263 | MASTER-Kislovodsk | C | 180 | 13.5 | 39263 | MASTER-Kislovodsk | C | 180 | 14.3 | 39471 | MASTER-Kislovodsk | C | 180 | 13.5 | 39471 | MASTER-Kislovodsk | C | 180 | 14.1 | 39687 | MASTER-Kislovodsk | C | 180 | 14.2 | 39687 | MASTER-Kislovodsk | C | 180 | 15.0 | 39903 | MASTER-Kislovodsk | C | 180 | 14.7 | 39903 | MASTER-Kislovodsk | C | 180 | 15.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43322. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41412] GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
by GCN Circulars 04 Jan '26

04 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43321 SUBJECT: GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits DATE: 26/01/04 15:26:20 GMT FROM: Dr. Kaushik Chatterjee at SWIFAR, Yunnan University <mails.kc.physics(a)gmail.com> Kaushik Chatterjee, Guowang Du, Yu Pan, Yifei Ding, Guangya Zeng, Brajesh Kumar, Yuan Fang, Jinghua Zhang, Xingzhu Zou, Xinlei Chen, Xufeng Zhu, Tao Wang, Xinzhong Er, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team: The EP-WXT trigger 01709250693 (trigger time 2025-12-30T01:22:21), identified as EP251230a/GRB251230A (Lanava et al., GCN 43252; Li et al. GCN 43255; Wang. C. et al., GCN 43259; Osborne et al., GCN 43263) was observed with the following facility of the Yunnan University, located at the Lijiang Observatory: the 1.6m Multi-channel Photometric Survey Telescope (Mephisto). A set of simultaneous multi-band (ugi and vrz) frames were collected starting from 2025-12-30 UTC19:34:28 (~ 16.9 hr after the trigger) and continued till 2025-12-30 UTC20:00:18. The optical counterpart reported previously (Busmann et al., GCN 43258; Masi et al., GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265) was not detected in our stacked frames and the upper limits (5 sigma) are listed below. --------------------------------------------------- Start_Time(UT) | Band | Exp(s) | LimMag (AB) --------------------------------------------------- 2025-12-30T19:34:28 | u | 45.0*7 | >21.08 2025-12-30T19:54:43 | v | 45.0*6 | >20.89 2025-12-30T19:34:30 | g | 45.0*6 | >21.36 2025-12-30T19:54:45 | r | 45.0*6 | >21.38 2025-12-30T19:34:30 | i | 45.0*7 | >21.04 2025-12-30T19:54:44 | z | 45.0*6 | >20.32 --------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. The facility is operated by the South-Western Institute for Astronomy Research (SWIFAR), Yunnan University. It provides real-time, high-quality colors of stellar objects. The Mephisto mosaic cameras were installed in October 2025. The first light was achieved in all three channels on 10 October 2025 and presently, these are under the commissioning phase. All the data have been reduced by the Mephisto data processing pipeline. Here, we note that the current data processing pipeline is still at a preliminary stage, with flux calibration precision in each band at the level of about 5% or even higher. View this GCN Circular online at https://gcn.nasa.gov/circulars/43321. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41411] GRB 260104A: Swift-XRT refined Analysis
by GCN Circulars 04 Jan '26

04 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43320 SUBJECT: GRB 260104A: Swift-XRT refined Analysis DATE: 26/01/04 14:58:50 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.A. Kennea (PSU), D.N. Burrows (PSU), S. Lanava (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-OAR), M. Perri (SSDC & INAF-OAR) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.3 ks of XRT data for GRB 260104A, from 101 s to 28.3 ks after the trigger. The data comprise 10 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The late-time light curve (from T0+5.1 ks) can be modelled with a power-law decay with a decay index of alpha=1.22 (+0.26, -0.23). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.78 (+0.16, -0.10). The best-fitting absorption column is 3.55 (+3.69, -0.15) x 10^20 cm^-2, consistent with the Galactic value of 3.4 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 3.7 x 10^-11 (4.0 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.55 (+3.69, -0.15) x 10^20 cm^-2 Galactic foreground: 3.4 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.78 (+0.16, -0.10) If the light curve continues to decay with a power-law decay index of 1.22, the count rate at T+24 hours will be 4.6 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x 10^-13 (1.8 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/01430212. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43320. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41410] GRB 260104A: Enhanced Swift-XRT position
by GCN Circulars 04 Jan '26

04 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43319 SUBJECT: GRB 260104A: Enhanced Swift-XRT position DATE: 26/01/04 14:49:33 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 3264 s of XRT Photon Counting mode data and 6 UVOT images for GRB 260104A, 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 = 337.39920, -21.29552 which is equivalent to: RA (J2000): 22h 29m 35.81s Dec (J2000): -21d 17' 43.9" with an uncertainty of 2.0 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/43319. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41409] GRB 260101A: Swift/UVOT Detection
by GCN Circulars 04 Jan '26

04 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43318 SUBJECT: GRB 260101A: Swift/UVOT Detection DATE: 26/01/04 10:35:48 GMT FROM: noelklin(a)umbc.edu N. Klingler (NASA-GSFC / UMBC / CRESST II) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 260101A 144 s after the BAT trigger (Cenko et al., GCN Circ. 43285). A source consistent with the enhanced XRT position (Evans et al., GCN Circ. 43289) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 05:45:42.96 = 86.42898 (deg.) Dec (J2000) = +63:35:32.1 = 63.59226 (deg.) with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence). Detections and 2-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag b 399.7 419.5 19.8 16.57 +/- 0.10 b 548.6 568.4 19.8 16.74 +/- 0.11 b 697.4 717.1 19.7 16.80 +/- 0.11 b 847.1 866.9 19.8 17.20 +/- 0.14 b 1031.0 1200.3 169.3 17.50 +/- 0.11 b 1329.9 1498.6 168.7 17.69 +/- 0.12 b 1628.4 1648.2 19.8 17.81 +/- 0.18 b 21638.8 22547.2 908.4 21.07 +/- 0.27 u 144.3 394.1 249.8 16.09 +/- 0.05 u 523.8 543.5 19.7 16.44 +/- 0.13 u 672.6 692.3 19.7 17.15 +/- 0.18 u 822.4 842.1 19.7 16.97 +/- 0.16 u 875.8 1025.6 149.8 17.12 +/- 0.08 u 1155.7 1324.8 169.1 17.86 +/- 0.18 u 1454.1 1623.5 169.4 17.86 +/- 0.18 u 95366.4 96053.5 687.1 >21.51 v 450.4 470.2 19.8 16.17 +/- 0.14 v 599.0 618.8 19.8 15.87 +/- 0.12 v 747.6 767.4 19.8 16.28 +/- 0.15 v 1081.4 1251.3 169.9 16.98 +/- 0.15 v 1380.2 1549.5 169.3 17.23 +/- 0.17 v 11438.4 12223.4 785.0 19.27 +/- 0.14 v 27138.9 28046.0 907.1 20.55 +/- 0.38 uvw1 499.5 816.9 317.4 >19.48 uvw1 1131.1 1599.0 467.9 >19.74 uvw1 34121.1 34973.5 852.4 >21.44 uvw2 425.8 743.0 317.2 >19.43 uvw2 1057.0 1525.2 468.2 >19.72 uvw2 10532.3 11432.0 899.7 >21.06 uvw2 22553.7 23374.5 820.8 >21.39 uvw2 100888.2 101273.5 385.3 >20.96 uvm2 474.7 643.2 168.5 >18.78 uvm2 1105.7 1424.3 318.6 >18.80 uvm2 28051.2 28842.6 791.4 >21.25 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.197 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/43318. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41408] GRB 260103A: GECAM-B observation of a burst
by GCN Circulars 04 Jan '26

04 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43317 SUBJECT: GRB 260103A: GECAM-B observation of a burst DATE: 26/01/04 08:59:17 GMT FROM: Xinghao Luo at IHEP <2952704891(a)qq.com> GRB 260103A: GECAM-B observation of a burst Xing-Hao Luo, Chen-Wei Wang, Shao-Lin Xiong, Yue Huang (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by GRB 260103A, at 2026-01-03T01:46:53.950 UTC (denoted as T0), which is also detected by SVOM/GRM (Chen-Wei Wang et.al., GCN #43314). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 9.0 +3.6/-7.0 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260103A.png GECAM-B on-ground localization of this burst is (J2000): Ra: 269.0 deg Dec: 46.7 deg Err: 4.6 deg (1-sigma, statistical only) Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/43317. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41407] GRB 260104B: Fermi GBM Final Localization
by GCN Circulars 04 Jan '26

04 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43316 SUBJECT: GRB 260104B: Fermi GBM Final Localization DATE: 26/01/04 07:50:23 GMT FROM: Rushikesh Sonawane at IISER, TVM <rushikesh23(a)iisertvm.ac.in> The Fermi GBM team reports the detection of a likely LONG GRB "At 05:49:57.62 UT on 04 January 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260104B (trigger 789198602/260104243). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 87.42, Dec = -29.65 (J2000 degrees, equivalent to J2000 05h 49m, -29d 39'), with a statistical uncertainty of 10.28 degrees. The angle from the Fermi LAT boresight is 42 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260104243/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260104243/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260104243/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/43316. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41406] GRB 260104A: Swift detection of a burst
by GCN Circulars 04 Jan '26

04 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43315 SUBJECT: GRB 260104A: Swift detection of a burst DATE: 26/01/04 05:57:24 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> R. Caputo (GSFC), J. J. DeLaunay (PSU), K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 05:37:02 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 260104A (trigger=1430212). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 337.415, -21.280 which is RA(J2000) = 22h 29m 40s Dec(J2000) = -21d 16' 48" 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 20 sec. The peak count rate was ~2400 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 05:38:28.9 UT, 86.1 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 337.39898, -21.29547 which is equivalent to: RA(J2000) = 22h 29m 35.76s Dec(J2000) = -21d 17' 43.7" with an uncertainty of 2.2 arcseconds (radius, 90% containment). This location is 77 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (3.40 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 2.8 (+2.48/-2.16) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 90 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 none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.033. Burst Advocate for this burst is R. Caputo (regina.caputo AT nasa.gov) 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/43315. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41405] GRB 260103A: SVOM/GRM observation of a possible GRB
by GCN Circulars 03 Jan '26

03 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43314 SUBJECT: GRB 260103A: SVOM/GRM observation of a possible GRB DATE: 26/01/03 11:42:40 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Piron (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a burst GRB 260103A (SVOM trigger reference: sb26010302) at 2026-01-03T01:46:54.000 UTC (T0). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a T90 of 8.0 +3.8/-1.8 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260103A.png We note that the burst occurred near the end of a C class solar flare as detected by the GOES satellites. So the solar flare origin cannot be excluded although this burst has a typical brightness, duration, and hardness of a long GRB. 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang(IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43314. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41404] Fermi-LAT Gamma-ray Observations of IceCube-251225A
by GCN Circulars 03 Jan '26

03 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43313 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-251225A DATE: 26/01/03 09:01:01 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 IC251225A neutrino event (GCN 43239) 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 25-12-25 at 20:14:06.80 UTC (T0) with J2000 position RA = 297.42 (+0.54, -0.49) deg, Decl. = 22.47 (+0.46, -0.48) deg 90% PSF containment (J2000). No cataloged gamma-ray sources are found within the 90% IC251225A 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 IC251225A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC251225A 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), <1.3e-08 (<2.2e-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/43313. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41403] GRB 260101A: COLIBRÍ optical observations
by GCN Circulars 03 Jan '26

03 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43312 SUBJECT: GRB 260101A: COLIBRÍ optical observations DATE: 26/01/03 06:27:01 GMT FROM: globus(a)astro.unam.mx Noémie Globus (UNAM), Sarah Antier (IJCLAB), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Camila Angulo (UNAM), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Nikos Mandarakas (LAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM), report: We observed the optical counterpart of the “New Year Burst”, GRB 260101A (Fermi GBM team, GCN Circ. 43284; Cenko et al., GCN Circ. 43285; Pérez-Fournon et al., GCN Circ. 43286; de Ugarte Postigo et al., GCN Circ. 43287; Beardmore et al., GCN Circ. 43289; Lipunov et al., GCN Circ. 43290; D'Avanzo et al., GCN Circ. 43291; SVOM/GRM team et al., GCN Circ. 43292; Saccardi et al., GCN Circ. 43293; Wang et al., GCN Circ. 43294; Hristov et al., GCN Circ. 43297) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-03 03:22 to 05:47 UTC (50.4 hours to 52.9 hours after the trigger) and obtained 105 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In our stacked images, we detect a source at the position of the afterglow (Cenko et al., GCN Circ. 43285) at preliminary magnitudes of: r = 22.11 +/- 0.11, z = 21.47 +/- 0.09. 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/43312. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41402] SVOM GRB260103.08: Global MASTER-Net observations report
by GCN Circulars 03 Jan '26

03 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43311 SUBJECT: SVOM GRB260103.08: Global MASTER-Net observations report DATE: 26/01/03 02:28:23 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 [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the SVOM GRB260103.08 (trigger No 1767405296,10h 29m 22.85s , +78d 07m 01.2s, R=1) errorbox 9 sec after notice time and 47 sec after trigger time at 2026-01-03 01:55:42 UT, with upper limit up to 17.8 mag. The observations began at zenith distance = 36 deg. The sun altitude is -29.5 deg. The galactic latitude b = 37 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=3094431 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 52 | 2026-01-03 01:55:42 | MASTER-Kislovodsk | (10h 28m 21.31s , +78d 15m 14.6s) | C | 10 | 16.1 | 72 | 2026-01-03 01:55:42 | MASTER-Kislovodsk | (10h 28m 21.31s , +78d 15m 14.7s) | C | 50 | 17.2 | Coadd 52 | 2026-01-03 01:55:43 | MASTER-Kislovodsk | (10h 26m 28.30s , +78d 37m 51.0s) | P| | 10 | 15.1 | 88 | 2026-01-03 01:56:13 | MASTER-Kislovodsk | (10h 28m 20.71s , +78d 15m 17.8s) | C | 20 | 16.5 | 88 | 2026-01-03 01:56:13 | MASTER-Kislovodsk | (10h 26m 27.38s , +78d 37m 54.9s) | P| | 20 | 15.8 | 129 | 2026-01-03 01:56:54 | MASTER-Kislovodsk | (10h 28m 20.20s , +78d 15m 20.4s) | C | 20 | 16.4 | 129 | 2026-01-03 01:56:54 | MASTER-Kislovodsk | (10h 26m 26.58s , +78d 37m 57.6s) | P| | 20 | 15.7 | 174 | 2026-01-03 01:57:35 | MASTER-Kislovodsk | (10h 28m 19.34s , +78d 15m 23.0s) | C | 30 | 16.8 | 219 | 2026-01-03 01:57:35 | MASTER-Kislovodsk | (10h 28m 19.30s , +78d 15m 23.2s) | C | 120 | 17.5 | Coadd 174 | 2026-01-03 01:57:35 | MASTER-Kislovodsk | (10h 26m 25.67s , +78d 38m 00.3s) | P| | 30 | 15.9 | 229 | 2026-01-03 01:58:25 | MASTER-Kislovodsk | (10h 28m 18.65s , +78d 15m 25.6s) | C | 40 | 16.8 | 229 | 2026-01-03 01:58:25 | MASTER-Kislovodsk | (10h 26m 24.60s , +78d 38m 02.7s) | P| | 40 | 16.1 | 295 | 2026-01-03 01:59:25 | MASTER-Kislovodsk | (10h 28m 17.63s , +78d 15m 28.0s) | C | 50 | 16.9 | 295 | 2026-01-03 01:59:25 | MASTER-Kislovodsk | (10h 26m 23.54s , +78d 38m 04.8s) | P| | 50 | 16.2 | 375 | 2026-01-03 02:00:35 | MASTER-Kislovodsk | (10h 28m 16.24s , +78d 15m 30.2s) | C | 70 | 17.1 | 475 | 2026-01-03 02:00:35 | MASTER-Kislovodsk | (10h 28m 16.19s , +78d 15m 30.3s) | C | 270 | 17.8 | Coadd 375 | 2026-01-03 02:00:35 | MASTER-Kislovodsk | (10h 26m 22.26s , +78d 38m 06.6s) | P| | 70 | 16.4 | 475 | 2026-01-03 02:02:05 | MASTER-Kislovodsk | (10h 28m 14.77s , +78d 15m 32.1s) | C | 90 | 17.2 | 475 | 2026-01-03 02:02:05 | MASTER-Kislovodsk | (10h 26m 20.59s , +78d 38m 07.9s) | P| | 90 | 16.6 | 596 | 2026-01-03 02:03:56 | MASTER-Kislovodsk | (10h 28m 13.42s , +78d 15m 32.8s) | C | 110 | 17.3 | 596 | 2026-01-03 02:03:56 | MASTER-Kislovodsk | (10h 26m 18.31s , +78d 38m 08.2s) | P| | 110 | 16.4 | 731 | 2026-01-03 02:06:07 | MASTER-Kislovodsk | (10h 28m 13.42s , +78d 15m 32.8s) | C | 120 | 14.8 | 731 | 2026-01-03 02:06:07 | MASTER-Kislovodsk | (10h 26m 18.35s , +78d 38m 07.2s) | P| | 120 | 14.4 | 908 | 2026-01-03 02:09:34 | MASTER-Kislovodsk | (10h 34m 57.99s , +79d 17m 59.5s) | C | 60 | 17.0 | 908 | 2026-01-03 02:09:34 | MASTER-Kislovodsk | (10h 09m 58.98s , +79d 35m 40.7s) | C | 60 | 17.2 | 1008 | 2026-01-03 02:11:13 | MASTER-Kislovodsk | (10h 50m 24.38s , +77d 23m 12.9s) | C | 60 | 17.0 | 1008 | 2026-01-03 02:11:13 | MASTER-Kislovodsk | (10h 29m 13.06s , +77d 41m 41.3s) | C | 60 | 17.3 | 1113 | 2026-01-03 02:12:58 | MASTER-Kislovodsk | (10h 29m 26.49s , +78d 16m 54.1s) | C | 60 | 17.0 | 1113 | 2026-01-03 02:12:58 | MASTER-Kislovodsk | (10h 06m 36.99s , +78d 34m 43.4s) | C | 60 | 17.2 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43311. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41401] GRB 260102B: Fermi GBM Final Real-time Localization
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43310 SUBJECT: GRB 260102B: Fermi GBM Final Real-time Localization DATE: 26/01/02 21:23:33 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 SHORT GRB At 21:12:03 UT on 2 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260102B (trigger 789081128.373244 / 260102883). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 60.7, Dec = -67.8 (J2000 degrees, equivalent to J2000 04h 02m, -67d 47'), with a statistical uncertainty of 17.7 degrees. The angle from the Fermi LAT boresight is 23.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260102883/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260102883/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260102883/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43310. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41400] SVOM GRB260102.17: Global MASTER-Net observations report
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43309 SUBJECT: SVOM GRB260102.17: Global MASTER-Net observations report DATE: 26/01/02 18:14:24 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 [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the SVOM GRB260102.17 (trigger No 1767326986,12h 15m 31.27s , +48d 15m 29.9s, R=0.0849) errorbox 48331 sec after notice time and 48428 sec after trigger time at 2026-01-02 17:36:54 UT, with upper limit up to 15.1 mag. The observations began at zenith distance = 81 deg. The sun altitude is -41.1 deg. The galactic latitude b = 68 deg., longitude l = 138 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3093252 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 33488 | 2026-01-02 13:26:23 | MASTER- | (12h 20m 52.08s , +49d 49m 23.4s) | C | 180 | 17.3 | 48459 | 2026-01-02 17:36:54 | MASTER-Kislovodsk | (12h 14m 33.74s , +47d 55m 28.1s) | C | 60 | 15.1 | 50357 | 2026-01-02 18:08:32 | MASTER-Kislovodsk | (12h 14m 30.88s , +47d 52m 14.0s) | C | 60 | 15.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43309. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41399] Fermi GBM Sub-Threshold Detection of GRB 260102A
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43308 SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 260102A DATE: 26/01/02 17:59:21 GMT FROM: rhamburg(a)usra.edu R. Hamburg (USRA) reports on behalf of the Fermi-GBM Team: SVOM/ECLAIRs detected GRB 260102A on 2026-01-02 at 04:10:03 UTC (Xie et al 2026, GCN 43295). There was no Fermi-GBM onboard trigger around this event time. An automated, blind search for gamma-ray bursts below the onboard triggering threshold in Fermi-GBM identified no candidates. The GBM Targeted Search [1], the most sensitive coherent search for GRB-like signals in GBM, identified a transient starting approximately 33 seconds after the ECLAIRs best imaging SNR time at 2026-01-02T04:09:45 (Xie et al 2026, GCN 43295). The transient is detected most significantly on the 32.768 s timescale with a false alarm rate of 1.1e-05 Hz, using a "normal" spectrum (Band function with Epeak = 230 keV, alpha = -1.0, beta = -2.3) for a GRB. The Targeted Search localization is consistent with the ECLAIRs position. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/43308. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41398] GRB 260102A: EP-FXT follow-up observation
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43307 SUBJECT: GRB 260102A: EP-FXT follow-up observation DATE: 26/01/02 15:50:27 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (HKU), X. Mao (NAO, CAS), J. P. Chen (SYSU), and H. W. Pan (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 260102A (SVOM/sb26010201, Xie et al., GCN 43295) at 2026-01-02 05:43:47 (UTC), about 1.5 hours after the SVOM/ECLAIRs trigger, with an exposure time of 3523 s. One uncatalogued source is detected within the ECLAIRs error circle, and the source is spatially consistent with the counterpart reported in optical and X-ray bands, including detections (Evans et al., GCN 43298; Wu et al., GCN 43300; Bernardini et al., GCN 43304) and upper limits (Antier et al., GCN 43303; Saccardi et al., GCN 43305). Preliminary analysis on this source is automatically conducted, and details are listed as follows. EPF_J121547.6+481500 RA (J2000): 183.9483 Dec (J2000): 48.2501 Flux: 3.82 x 10^-13 erg/s/cm2 (observed, 0.5-10 keV) Flux_err: 4.60 x 10^-14 erg/s/cm2 (1 sigma) The position uncertainty of the source is about 10 arcsec in radius (90% C.L. statistical and systematic). Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43307. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41397] EP260101a: Global MASTER-Net observations report
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43306 SUBJECT: EP260101a: Global MASTER-Net observations report DATE: 26/01/02 15:18:21 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 [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP260101a ( EP Team et al., GCN 43288) errorbox 1 days 27579 sec after notice time and 1 days 29347 sec after trigger time at 2026-01-02 14:44:49 UT, with upper limit up to 15.3 mag. Observations started at twilight. The observations began at zenith distance = 30 deg. The sun altitude is -10.3 deg. The galactic latitude b = -16 deg., longitude l = 150 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3092541 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 115778 | 2026-01-02 14:44:49 | MASTER-Kislovodsk | (03h 03m 11.45s , +39d 18m 40.8s) | C | 60 | 15.3 | 116532 | 2026-01-02 14:57:23 | MASTER-Kislovodsk | (03h 03m 11.69s , +39d 19m 18.4s) | C | 60 | 14.7 | 116631 | 2026-01-02 14:59:03 | MASTER-Kislovodsk | (03h 03m 05.44s , +39d 18m 20.6s) | C | 60 | 14.5 | 116730 | 2026-01-02 15:00:41 | MASTER-Kislovodsk | (03h 03m 10.27s , +39d 18m 43.9s) | C | 60 | 15.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43306. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41396] GRB 260102A: LCO optical upper limits
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43305 SUBJECT: GRB 260102A: LCO optical upper limits DATE: 26/01/02 15:02:54 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Saccardi (CEA/Irfu), C. Wu, W. Xie (NAOC), W. Tan (IHEP) report on behalf of the SVOM mission team: We observed the field of the SVOM GRB 260102A (Xie et al., GCN 43295) with the LCO 1m telescope at McDonald Observatory equipped with the Sinistro instrument. Our observation started on 2026-01-02 at 08:14:01 UT (about 4.06 hr after the trigger) and we obtained 3x200 s exposures in the Pan-STARRS z filter. In the stacked image, we do not detect any new source within the Swift/XRT source #2 error circle (Bernardini et al., GCN 43304) and at the position of the SVOM/VT optical counterpart (Wu et al., GCN 43300). We measure the following upper limit calibrated against the Pan-STARRS DR1 catalog, and not corrected for Galactic extinction: z > 20.1 AB (3-sigma, mid-time 4.13 hr after the trigger). This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/43305. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41395] GRB 260102A: Swift-XRT observations
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43304 SUBJECT: GRB 260102A: Swift-XRT observations DATE: 26/01/02 14:37:52 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M.G. Bernardini (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-OAR) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected burst GRB 260102A, collecting 2.8 ks of Photon Counting (PC) mode data between T0+9.6 ks and T0+26.1 ks. One uncatalogued X-ray source has been detected within the estimated 3-sigma SVOM/ECLAIRs error region (502 arcsec), it is below the RASS limit and shows no definitive signs of fading. Therefore, at the present time we cannot confirm this as the afterglow. Details of this source are given below: Source 2: RA (J2000.0): 183.9493 = 12h 15m 47.82s Dec (J2000.0): +48.2506 = +48d 15' 02.1" Error: 6.2 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: (6.3 [+2.2, -1.8])e-3 ct s^-1 Distance: 167 arcsec from SVOM/ECLAIRs position. Flux: (1.72 [+0.59, -0.48])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) SVOM/VT detected an optical counterpart consistent with this X-ray source (GCN Circ. 43300). An uncatalogued source 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/00021896. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43304. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41394] GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43303 SUBJECT: GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations DATE: 26/01/02 14:09:15 GMT FROM: Dalya Akl at New York University Abu Dhabi <dka2010(a)nyu.edu> Sarah Antier (IJCLAB), William H. Lee (UNAM), Dalya Akl (NYUAD), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Nikos Mandarakas (LAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Wenjin Xie (NAOC), and Wenjun Tan (IHEP) report: We imaged the field of the SVOM GRB 260102A (Xie et al., GCN Circ. 43295) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-01-02 13:04 to 13:25 UTC (about 8.9 hours after the trigger) and obtained 18 minutes of simultaneous exposure in the r/z filters. The data were reduced and coadded with the COLIBRÍ ASU pipeline and analyzed 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 did not detect the optical counterpart reported by Wu et al. (GCN Circ. 43300) to preliminary 3-sigma magnitude limits of: r > 23.5 z > 22.8 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/43303. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41393] Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43302 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB DATE: 26/01/02 13:09:36 GMT FROM: A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca(a)unitn.it> A. Holzmann Airasca (UniTrento and INFN Bari) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 789047602/260102495 at 11:53:17.07 UT on 02 January 2026, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to local particle activity." View this GCN Circular online at https://gcn.nasa.gov/circulars/43302. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41392] GRB 251230A / EP251230a: GECAM-B detection
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43301 SUBJECT: GRB 251230A / EP251230a: GECAM-B detection DATE: 26/01/02 13:08:59 GMT FROM: guohx(a)ihep.ac.cn Hao-Xuan Guo, Chen-Wei Wang, Zheng-Hang Yu, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by GRB 251230A / EP251230a at 2025-12-30T01:21:44.050 UTC (denoted as T0), which is also detected by Swift (Lanava et al., GCN #43252), EP-WXT (Li et al., GCN #43255 and Wang et al., GCN #43272) and Insight-HXMT/HE (Guo et al., GCN #43299). According to the GECAM-B light curve in about 70-6000 keV, this burst mainly consists of multi-pulses with a duration (T90) of 71.2 +4.6/-8.2 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251230A.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/43301. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41391] GRB 260102A: SVOM/VT optical counterpart
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43300 SUBJECT: GRB 260102A: SVOM/VT optical counterpart DATE: 26/01/02 12:45:56 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> C. Wu, H. L. Li, L. P. Xin, Y. L. Qiu, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, L. Lan, J. R. Xu, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), W. J. Tan (IHEP) report on behalf of the SVOM team. SVOM performed an automatic slew on the burst GRB 260102A triggered by SVOM/ECLAIRs (sb26010201, Xie et al., GCN 42295) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The observation began at 2026-01-02T04:13:40, i.e., 217 sec post trigger. An optical uncatalogued source was detected within errorbox of ECLAIRs (Xie et al., GCN 42295) and Swift-XRT source #2 (Evans et al., GCN 43298), compared to the Legacy survey catalog. The position is at R.A., Dec. = 183.95015, 48.25116 degrees, equivalent to: R.A. (J2000) = 12:15:48.03 Dec. (J2000) = 48:15:04.18 with an uncertainty of 0.5 arcsec. The magnitudes are: Mid_time Band Exposure Time Magnitude (AB) 242 sec VT_B 50 sec 19.98+/-0.06 242 sec VT_R 50 sec 18.46+/-0.03 872 sec VT_B 50 sec 21.40+/-0.16 872 sec VT_R 50 sec 20.21+/-0.10 Our photometry was not corrected for Galactic extinction. More follow-ups for this burst 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/43300. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41390] GRB 251230A / EP251230a: Insight-HXMT/HE detection
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43299 SUBJECT: GRB 251230A / EP251230a: Insight-HXMT/HE detection DATE: 26/01/02 12:17:17 GMT FROM: guohx(a)ihep.ac.cn Hao-Xuan Guo, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team: At 2025-12-30T01:22:22.000 (T0), Insight-HXMT/HE detected a burst, GRB 251230A / EP251230a, which is also detected by Swift (Lanava et al., GCN #43252) and EP-WXT (Li et al., GCN #43255 and Wang et al., GCN #43272). The Insight-HXMT/HE light curve mainly consists of multiple pulses with T90 of 54.4 +11.6/-8.4 s. The 1s peak rate, measured from T0-0.70 s, is 797 cnts/sec. Insight-HXMT/HE detected a total of 10,311 counts from this burst. The Insight-HXMT /HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251230A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the Low-Gain mode with the energy range of about 300-3000 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/43299. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41389] GRB 260102A: Swift ToO observations
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43298 SUBJECT: GRB 260102A: Swift ToO observations DATE: 26/01/02 06:48:54 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 260102A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021896 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/43298. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41388] GRB 260101A: Fermi GBM Observation
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43297 SUBJECT: GRB 260101A: Fermi GBM Observation DATE: 26/01/02 05:59:57 GMT FROM: Glowbug DEV <boyan.a.hristov(a)nasa.gov> B. Hristov (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 00:56:30.65 UT on 01 January 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260101A (trigger 788921795/260101039). which was also detected by Swift (S. B. Cenko et al. 2026, GCN 43285), SVOM/GRM (Z. Yu et al. 2026, GCN 43292) and GECAM-B (C. Wang et al. 2026, GCN 43294). The Fermi GBM on-ground location is consistent with the one reported by Swift. The angle from the Fermi LAT boresight is 43 degrees. The GBM light curve consists of multiple emission episodes with a duration (T90) of about 27.4 s (50-300 keV). The time-averaged spectrum from T0 to T0+29.6 s s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.09 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 143.5 +/- 1.5 keV. The event fluence (10-1000 keV) in this time interval is (6.7 +/- 0.12)e-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+25 s in the 10-1000 keV band is 9.6 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: sftp://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/43297. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41387] EP260101a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43296 SUBJECT: EP260101a: refined analysis of the EP-WXT and EP-FXT observations DATE: 26/01/02 04:56:23 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> M.-H. Zhang, Y.-L. Wang, W. Chen, H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260101a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Zhang et al., GCN 43288). The refined analysis of the WXT data shows that the event started at T0=2026-01-01T06:31:46 (UTC) and lasted for 200 seconds before the observation was interrupted by the autonomous follow-up. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.3 x 10^21 cm^-2 and a photon index of 1.7 (-0.7/+0.7). The derived average unabsorbed 0.5-4 keV flux is 6.6 (-3.2/+2.0) x 10^(-11) erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously at 2026-01-01T06:38:27 (UTC), about 7 minutes after T0. The exposure time of this observation is 4674s. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 46.0631, DEC = 39.4376 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent with the WXT position. A significant decay was detected in the light curve during the initial phase of FXT observation. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.3 x 10^21 cm^-2 and a photon index of 2.9 (-0.4/+0.3). The derived average unabsorbed 0.5-10 keV flux is 8.4 (-1.3/+1.2) x 10^(-13) erg/s/cm^2. We performed another ToO observation with EP-FXT, starting at 2026-01-01T11:08:28 (UTC), with an exposure time of 6950 s. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with the same fixed Galactic hydrogen column density and a photon index of 3.5 (-1.1/+1.0). The derived average unabsorbed 0.5-10 keV flux is 8.6 (-4.1/+2.9) x 10^(-14) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43296. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41386] GRB 260102A: SVOM detection of a burst
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43295 SUBJECT: GRB 260102A: SVOM detection of a burst DATE: 26/01/02 04:43:22 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Wenjin XIE (NAOC), Wenjun TAN (IHEP), Donhua ZHAO (NAOC), Chenwei WANG (IHEP) report on behalf of the SVOM mission team: At 2026-01-02T04:10:03 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260102A (SVOM burst-id sb26010201). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 14 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 16.44 in the [8-120] keV energy band over a time window of 40.96 seconds starting at 2026-01-02T04:09:45. The localization of the best alert is R.A., Dec. 183.8803, 48.2583 degrees: R.A. (J2000) = 12h15m31.28s Dec. (J2000) = 48d15m29.77s with a 90% confidence level (C.L.) radius of 5.09 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM/GRM detected the burst also. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260102A.png SVOM slewed to the burst. SVOM/MXT and VT began observing the field after the slew. The analysis of the data will be published in a future circular. 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 Wenjin XIE: xiewj(a)bao.ac.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/43295. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41385] GRB 260101A: GECAM-B detection
by GCN Circulars 02 Jan '26

02 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43294 SUBJECT: GRB 260101A: GECAM-B detection DATE: 26/01/02 04:42:19 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Zheng-Hang Yu, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by GRB 260101A at 2026-01-01T00:56:34.100 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43284), Swift (S. B. Cenko et al., GCN #43285), SVOM/GRM (Yu et al., GCN #43292). According to the GECAM-B light curve in about 70-6000 keV, this burst mainly consists of multi-pulses with a duration (T90) of 30.0 +6.0/-3.0 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260101A.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/43294. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41384] GRB 260101A: NOT spectroscopic observations
by GCN Circulars 01 Jan '26

01 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43293 SUBJECT: GRB 260101A: NOT spectroscopic observations DATE: 26/01/01 21:05:21 GMT FROM: Andrea Saccardi at CEA/Irfu <andrea.saccardi(a)cea.fr> A. Saccardi (CEA/Irfu), L. Izzo (INAF/OACN and DARK/NBI), A. Martin-Carrillo (UCD), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), K. Valeckas (NOT & NBI), report on behalf of a larger collaboration: We observed the optical afterglow (Cenko et al., GCN 43285; Perez-Fournon et al., GCN 43286; de Ugarte Postigo et al., GCN 43287) of GRB 260101A detected by Fermi (Fermi GBM team, GCN 43284), Swift (Cenko et al., GCN 43285) and SVOM/GRM (Yu et al., GCN 43292) with the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. A spectrum using grism #4 was secured starting on 2026 Jan 1 at 01:43:54 UT (47 min after the GRB trigger). Due to bad weather and seeing, we only got two spectra, one of which had a very short exposure time, resulting in a relatively low S/N for the stacked spectrum. The total exposure time is ~ 1500 s covering the wavelength range 3800-9300 AA. From the unfiltered acquisition 30 s image we measure an AB magnitude of 17.30 +/- 0.07, at a mid-time of 45 minutes after the trigger. Our photometry was calibrated against nearby stars from the r-band PanSTARRS catalogue and not corrected for Galactic extinction. In a preliminary reduction of the stacked spectrum, we detect a trace over the whole observed wavelength range. At the redshift of z = 2.623 reported by de Ugarte Postigo et al. (GCN 43287) we identify different absorption features, which we interpret as due to Si IV, C IV, and Al II. We note that we do not see a clear absorption corresponding to the weak Ly-alpha. Further analysis is ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/43293. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41383] GRB 260101A: SVOM/GRM observation
by GCN Circulars 01 Jan '26

01 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43292 SUBJECT: GRB 260101A: SVOM/GRM observation DATE: 26/01/01 14:35:47 GMT FROM: yzh807926(a)163.com SVOM/GRM team: Zheng-Hang Yu, Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Hui Yang (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a burst GRB 260101A (SVOM trigger reference: sb26010101) at 2026-01-01T00:56:37.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43284) and Swift (S. B. Cenko et al., GCN #43285). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a precursor followed by a main episode with multiple peaks a T90 of 33.0 +5.5/-3.0 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260101A.png In addition, the position of this burst, as determined by Swift/XRT (RA= 89.43, DEC= 63.59 GCN#43285), is located at about 53 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-9 to T0+26 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.39 +/-0.11 and the cutoff energy, parameterized as Epeak, is 150 +48/-27 keV. The event fluence (10-1000 keV) in this time interval is (8.10 +0.83/-0.66)E-06 erg/cm^2. The 1s peak spectrum, measured from T0+18.5 to T0+19.5 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -0.89 +0.15/-0.16 and the cutoff energy, parameterized as Epeak, is 109 +14/-10 keV. The flux (10-1000 keV) in this time interval is (8.99 +0.63/-0.56)E-07 erg/cm^2/s. With the redshift z = 2.623 by GTC (A. de Ugarte Postigo et al., GCN#43287), GRB 260101A is more consistent with Type II GRBs in the 'Amati' relation diagram, as shown at:https://www.bursthub.cn//admin/static/svgrb260101A_amati.png And the localization in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260101A_yonetoku.png 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Zheng-Hang Yu(IHEP)(zhyu(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43292. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41382] GRB 260101A: Swift-XRT refined Analysis
by GCN Circulars 01 Jan '26

01 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43291 SUBJECT: GRB 260101A: Swift-XRT refined Analysis DATE: 26/01/01 12:11:45 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), 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), E. Ambrosi (INAF-IASFPA) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.7 ks of XRT data for GRB 260101A, from 100 s to 28.9 ks after the trigger. The data comprise 165 s in Windowed Timing (WT) mode (the first 10 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The late-time light curve (from T0+5.3 ks) can be modelled with a power-law decay with a decay index of alpha=1.65 (+/-0.17). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.02 (+0.16, -0.15). The best-fitting absorption column is 2.1 (+/-0.5) x 10^21 cm^-2, consistent with the Galactic value of 1.6 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.91 (+0.16, -0.15) and a best-fitting absorption column of 2.2 (+0.6, -0.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.2 (+0.6, -0.5) x 10^21 cm^-2 Galactic foreground: 1.6 x 10^21 cm^-2 Excess significance: 1.8 sigma Photon index: 1.91 (+0.16, -0.15) If the light curve continues to decay with a power-law decay index of 1.65, the count rate at T+24 hours will be 3.9 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.5 x 10^-13 (2.0 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/01429608. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43291. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41381] Swift GRB 260101A: Global MASTER-Net observations report
by GCN Circulars 01 Jan '26

01 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43290 SUBJECT: Swift GRB 260101A: Global MASTER-Net observations report DATE: 26/01/01 10:38:30 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-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the Swift GRB 260101A ( S. B. Cenko et al., GCN 43285) errorbox 34465 sec after notice time and 34491 sec after trigger time at 2026-01-01 10:31:22 UT, with upper limit up to 17.4 mag. Observations started at twilight. The observations began at zenith distance = 44 deg. The sun altitude is -11.9 deg. The galactic latitude b = 18 deg., longitude l = 150 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3092325 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 34522 | MASTER-Tunka | C | 60 | 17.3 | Coadd 34522 | MASTER-Tunka | C | 60 | 17.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43290. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41380] GRB 260101A: Enhanced Swift-XRT position
by GCN Circulars 01 Jan '26

01 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43289 SUBJECT: GRB 260101A: Enhanced Swift-XRT position DATE: 26/01/01 07:52:37 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 1689 s of XRT Photon Counting mode data and 3 UVOT images for GRB 260101A, 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 = 86.42902, +63.59238 which is equivalent to: RA (J2000): 05h 45m 42.96s Dec (J2000): +63d 35' 32.6" 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/43289. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41379] EP260101a: Einstein Probe detection of an X-ray transient
by GCN Circulars 01 Jan '26

01 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43288 SUBJECT: EP260101a: Einstein Probe detection of an X-ray transient DATE: 26/01/01 07:02:51 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> M.-H. Zhang, Y.-L. Wang, W. Chen, H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260101a. The transient triggered EP-WXT (ID: 01709250882) at 2026-01-01T06:35:42 (UTC). The WXT position of the source is R.A. = 46.057 deg, DEC = 39.410 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 46.0605 deg, DEC = 39.4380 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. Happy 2026!!! Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43288. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41378] GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
by GCN Circulars 01 Jan '26

01 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43287 SUBJECT: GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst DATE: 26/01/01 03:32:50 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> A. de Ugarte Postigo (LAM), A. Martin-Carrillo (UCD), C. C. Thoene (AbAO), D. B. Malesani (DAWN/NBI and Radboud), J. F. Agui Fernandez (CAHA), M. A. Aloy (UV), J. P. U. Fynbo (DAWN/NBI), L. Galbany (IEEC-CSIC), S. Geier (GTC), L. Izzo (INAF/OACN and DARK/NBI), G. Lombardi (GTC), N. A. Rakotondrainibe (LAM), B. Schneider (LAM), N. R. Tanvir (Univ. Leicester), R. Scarpa (GTC) report: We observed the optical counterpart of the new year burst GRB 260101A (Fermi GBM team, GCN 43284, Cenko et al. GCN ) using the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ instrument. In the r-band 30-s acquisition image (beginning on 2026-01-01 at 02:13:40.010 UT, that is 1.286 hr after trigger), the optical afterglow is well detected with a magnitude 18.05 ± 0.10 (AB), calibrated against nearby SDSS objects, and not corrected for Galactic extinction. A total of 2 spectra of 900 s were secured under poor conditions before clouds came in. Indeed, the second spectrum is already affected by a very high background. The first spectrum started on 2026-01-01 at 02:21:06.010 UT (1.410 hr after trigger), using grism R1000B. Continuum is visible over the range 3600-7800 AA. A number of absorption features are detected, which we interpret as due to Ly-alpha, SiII, OI, CII, SiIV, CIV, FeII and AlII, all at a common redshift z = 2.623, which we suggest to be the redshift of GRB 260101A. We note that the Ly-alpha absorption is very weak, making it a rather peculiar sight line. Happy 2026!!! This work has used the GRBspec database at http://grbspec.eu (de Ugarte Postigo et al. 2014, doi:10.1117/12.2055774). View this GCN Circular online at https://gcn.nasa.gov/circulars/43287. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41377] GRB 260101A: LCO detection of the optical counterpart
by GCN Circulars 01 Jan '26

01 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43286 SUBJECT: GRB 260101A: LCO detection of the optical counterpart DATE: 26/01/01 03:09:05 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon (IAC and ULL), F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia, E. Lekaroz-Urriza, M. Quintana-Ansaldo (all ULL), and A. López-Oramas (IAC and ULL) Following the detection of the long GRB 260101A, detected by Fermi (Fermi GBM team, GCN #43284) and Swift (Cenko et al., GCN #43285), we observed the field with one of the two Las Cumbres Observatory (LCO) 1-m telescopes, equipped with Sinistro cameras, located at the LCO node at McDonald Observatory, Texas. The observation, a single exposure of 180 sec in the SDSS r' filter, started on 2026-01-01 at 01:55:13 UT, about 58.7 minutes after the Fermi and Swift triggers. The optical counterpart detected by Swift UVOT (Cenko et al., GCN #43285), is clearly detected in our image with a magnitude of r' = 17.67 +/- 0.04, calibrated against PanSTARRS-1 DR2 stars and not corrected for Galactic extinction. This work makes use of observations from the Las Cumbres Observatory global telescope network (LCO program IAC2025B-008, SGLF and Superluminous Supernovae surveys). This work made use of the Astro-COLIBRI platform (P. Reichherzer et al. 2021, ApJS, 256, 5). View this GCN Circular online at https://gcn.nasa.gov/circulars/43286. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41376] GRB 260101A: Swift detection of a burst with an optical counterpart
by GCN Circulars 01 Jan '26

01 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43285 SUBJECT: GRB 260101A: Swift detection of a burst with an optical counterpart DATE: 26/01/01 01:13:39 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> S. B. Cenko (GSFC), J. J. DeLaunay (PSU), S. Dichiara (PSU), R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (U Tampa), K. L. Page (U Leicester) and T. M. Parsotan (GSFC) report on behalf of the Neil Gehrels Swift Observatory Team: At 00:56:30 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 260101A (trigger=1429608). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 86.465, +63.568 which is RA(J2000) = 05h 45m 51s Dec(J2000) = +63d 34' 06" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 40 sec. The peak count rate was ~7000 counts/sec (15-350 keV), at ~25 sec after the trigger. The XRT began observing the field at 00:57:54.9 UT, 84.7 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 86.42741, 63.59172 which is equivalent to: RA(J2000) = 05h 45m 42.58s Dec(J2000) = +63d 35' 30.2" with an uncertainty of 3.5 arcseconds (radius, 90% containment). This location is 104 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.60 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 3.3 (+3.30/-2.79) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 250 seconds with the U filter starting 144 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 05:45:42.94 = 86.42890 DEC(J2000) = +63:35:32.1 = 63.59225 with a 90%-confidence error radius of about 0.61 arc sec. This position is 4.5 arc sec. from the center of the XRT error circle. The estimated magnitude is 16.03 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.179. Burst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov) 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/43285. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41375] GRB 260101A: Fermi GBM Final Real-time Localization
by GCN Circulars 01 Jan '26

01 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43284 SUBJECT: GRB 260101A: Fermi GBM Final Real-time Localization DATE: 26/01/01 01:07:07 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 00:56:30 UT on 1 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260101A (trigger 788921795.64985 / 260101039). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 83.7, Dec = 64.0 (J2000 degrees, equivalent to J2000 05h 34m, 64d 00'), with a statistical uncertainty of 3.6 degrees. The angle from the Fermi LAT boresight is 43.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260101039/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260101039/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260101039/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43284. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41374] SVOM GRB251231.57: Global MASTER-Net observations report
by GCN Circulars 31 Dec '25

31 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43283 SUBJECT: SVOM GRB251231.57: Global MASTER-Net observations report DATE: 25/12/31 23:56:31 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-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the SVOM GRB251231.57 (trigger No 1767188879,18h 28m 56.90s , +11d 21m 52.2s, R=1) errorbox 33399 sec after notice time and 33434 sec after trigger time at 2025-12-31 23:05:13 UT, with upper limit up to 16.6 mag. The observations began at zenith distance = 80 deg. The sun altitude is -18.4 deg. The galactic latitude b = 10 deg., longitude l = 41 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3091965 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 33464 | 2025-12-31 23:05:13 | MASTER-Tunka | (18h 28m 26.18s , +10d 59m 08.2s) | C | 60 | 16.6 | 33464 | 2025-12-31 23:05:13 | MASTER-Tunka | (18h 28m 44.47s , +10d 53m 07.2s) | C | 60 | 16.2 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43283. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41373] GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
by GCN Circulars 31 Dec '25

31 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43282 SUBJECT: GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit DATE: 25/12/31 17:00:53 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, H. L. Li, Z. H. Yao, 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), J. X. Cao (GXU), W. L. Zhang (PMO) report on behalf of the SVOM/VT team. SVOM/VT conducted continued observations of GRB 251230A / EP251230a detected by Swift/BAT and EP/WXT (Lanava et al., GCN 43252; Wang et al., GCN 43259; Osborne et al., GCN 43263; Wang et al., GCN 43272; Sbarrato et al., GCN 43275). The magnitudes of the optical afterglow (Li et al., GCN 43255; Lipunov et al., GCN 43256; Busmann et al., GCN 43258; Masi, GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265; Starling et al., GCN 43267; He et al., GCN 43269; Tak et al., GCN 43270; Breeveld et al., GCN 43271; Gupta et al., GCN 43277; Sankar.K et al., GCN 43279; He et al., GCN 43280; Antier et al., GCN 43281) are: mid time (h) | exposure time (s) | band | mag (AB) -------------|-------------------|------|---------- 16.51 | 37*50 | VT_B | 23.0+-0.3 29.48 | 41*50 | VT_B | >23.4 16.51 | 37*50 | VT_R | 22.5+-0.2 29.46 | 39*50 | VT_R | >23.1 Our photometry was not corrected for Galactic extinction. Further analysis is ongoing. 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. Happy New Year to everyone ! ! ! View this GCN Circular online at https://gcn.nasa.gov/circulars/43282. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41372] GRB 251230A: GRANDMA/TAROT Early Detection
by GCN Circulars 31 Dec '25

31 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43281 SUBJECT: GRB 251230A: GRANDMA/TAROT Early Detection DATE: 25/12/31 14:25:21 GMT FROM: Dalya Akl at New York University Abu Dhabi <dka2010(a)nyu.edu> S. Antier (IJCLAB), A. Klotz (IRAP), D. Akl (NYUAD), C. Limonta (OCA), A. Dupin (OCA), Q. André (OCA), M. Coughlin (UNM), R. Strausbaugh (EIU), Z. Maksut (NU), E. Abdikamalov (NU), P. Hello (IJCLAB), S. Karpov (FZU), M. Pillas (IAP), C. Douzet (IJCLAB), Z. Wang (BNU), N. Kochiashvili (AbAO), A. Iskandar (XAO) on behalf of GRANDMA: We observed the field of the fast X-ray transient GRB 251230A/EP251230a (Lanava et al., GCN 43252; Wang et al., GCN 43259; Osborne et al., GCN 43263; Wang et al., GCN 43272; Sbarrato et al., GCN 43275) using TAROT/TCA with no filter. The observations started at 01:22:07 UTC on the 30th of December 2025, 36s post Swift trigger time, and lasted for 3 hours. We detected the optical afterglow candidate in the first (earliest) measurement with TAROT/TCA (60s exposure time), and we measured on 2025-12-30 01:23:19, r = 13.1 +/- 0.05 mag, after color correction. The data were reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022), using the PS1 catalogue for reference. Part of the light curve is public here on Skyportal/ICARE (https://skyportal-icare.ijclab.in2p3.fr) and also accessible in the public-report group of Skyportal: https://skyportal-icare.ijclab.in2p3.fr/public/sources/GRB-251230_012141/ve… We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). The results are consistent with other measurements reported. 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/43281. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41371] GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
by GCN Circulars 31 Dec '25

31 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43280 SUBJECT: GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening DATE: 25/12/31 12:31:28 GMT FROM: luca.izzo(a)inaf.it L. He (NAOC), L. Izzo (INAF/OACN and DARK/NBI), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), K. Valeckas (NOT & NBI) report on behalf of a larger collaboration: We observed the optical counterpart (Lanava et al., GCN 43252; Li et al., GCN 43255; Busmann et al., GCN 43258; Masi, GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265; Starling et al., GCN 43267; He et al., GCN 43269; Breeveld et al., GCN 43271; Sankar et al., GCN 43279) of GRB 251230A / EP251230a (Lanava et al., GCN 43252; Wang et al., GCN 43259; Osborne et al., GCN 43263), using the Nordic Optical Telescope (NOT), equipped with the ALFOSC camera. A series of 10 x 150s exposures was taken in the i band starting on 2025 Dec 31 at 04:46:27 (1.14 days after the Swift trigger). The afterglow is detected in the final stacked images with an AB magnitude of i = 22.93 +/- 0.09 mag, at a mid-time of 1.15 days after the trigger. Our photometry was calibrated using nearby stars from the Pan-STARRS catalog and is not corrected for Galactic extinction. This new epoch suggests that the fading of the optical afterglow has slowed down considerably from the decay index reported by He et al. GCN 43269. We note that, based on the colour measured in our earlier epoch, the r-band upper limit reported by Sankar et al. GCN 43279 suggests a possible rebrightening. Happy New Year to everyone!!! View this GCN Circular online at https://gcn.nasa.gov/circulars/43280. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41370] GRB 251230A/EP251230a: Optical upper limit with Kinder observations
by GCN Circulars 31 Dec '25

31 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43279 SUBJECT: GRB 251230A/EP251230a: Optical upper limit with Kinder observations DATE: 25/12/31 10:29:09 GMT FROM: Janet Chen at National Central University <janetstars(a)gmail.com> A. Sankar.K, A. Aryan, T.-W. Chen, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), J. H. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), Y.-H. Lee, M.-H. Lee, Y.-C. Pan, C.-C. Ngeow, C.-H. Lai, W.-J. Hou, H.-Y. Hsiao, H.-C. Lin, J.-K. Guo (all NCU), S. Yang, Z. N. Wang, L. L. Fan, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient GRB 251230A/EP251230a (Lanava et al., GCN#43252; Wang et al., GCN#43259; Osborne et al., GCN#43263; Wang et al., GCN#43272; Sbarrato et al., GCN#43275) using the 40cm SLT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The first SLT epoch of observations started at 18:17 UTC on the 30th of December 2025 (MJD 61039.762), 16.91 hr after the Swift/BAT trigger. We utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. In the stacked frame, we did not detect the proposed optical counterpart candidate (Li et al., GCN#43255; Busmann et al., GCN#43258; Masi et al., GCN#43260; Ghosh et al., GCN#43262; Ma et al., GCN#43265; Breeveld et al., GCN#43271), which has a tentative redshift upper limit of z < 2.2 (He et al., GCN#43269). Moreover, we utilized AutoPhOT to perform the PSF photometry. The details of the observations and the measured 3-sigma upper limit (in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | r | 61039.762 | 16.91 | 300 * 24 | >22.5 | 2".10 | 1.17 Utilizing the rigorous Lulin Observatory optical follow-up of the Einstein-Probe-discovered FXTs within the first year of the mission's operation, we investigated the possible connection between FXTs and GRBs, as reported in Aryan et al. (2025), ApJS, 281, 20. Our upper limits are the deepest and latest among those reported (Starling et al., GCN#43267; Tak et al., GCN#43270). The presented upper limit is calibrated using the field stars from the PanSTARRs DR2 and is not corrected for the expected Galactic foreground extinction of A_r = 0.05 mag in the direction of the transient (Schlafly & Finkbeiner, 2011). The methodology, details on the Lulin observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein-Probe mission are presented in Aryan et al., 2025, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69. View this GCN Circular online at https://gcn.nasa.gov/circulars/43279. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41369] EP251229a: Optical upper limit with Kinder observations
by GCN Circulars 31 Dec '25

31 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43278 SUBJECT: EP251229a: Optical upper limit with Kinder observations DATE: 25/12/31 10:27:16 GMT FROM: Janet Chen at National Central University <janetstars(a)gmail.com> A. Sankar.K, A. Aryan, T.-W. Chen, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), J. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), Y.-H. Lee, M.-H. Lee, Y.-C. Pan, C.-C. Ngeow, C.-H. Lai, W.-J. Hou, H.-Y. Hsiao, H.-C. Lin, J.-K. Guo (all NCU), S. Yang, Z. N. Wang, L. L. Fan, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP251229a (Wang et al., GCN#43253) using the 40cm SLT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The first SLT epoch of observations started at 20:18 UTC on the 29th of December 2025 (MJD 61038.846), 0.32 hr after the EP-WXT trigger. We utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. Moreover, we utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform template subtraction with the DESI Legacy Survey (Dey et al., 2019, AJ 157, 168) DR10 image using the 'sfft' (Hu et al., 2022, ApJ, 936, 157) algorithm. We did not detect any new and uncataloged source within the EP-FXT localization circle with a radius of 20", either in the stacked or difference image. Moreover, we further utilized AutoPhOT to perform the PSF photometry. The details of the observations and the measured 3-sigma upper limit (in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | r | 61038.846 | 0.32 | 300 * 12 | >22.4 | 2".01 | 1.35 Our non-detection is deeper than Lipunov et al. (GCN#43254), consistent with Martin-Carrillo et al. (GCN#43266) and Perez-Garcia et al. (GCN#43268). The absence of any associated optical counterpart down to 22.4 mag with the optical observations starting at 0.32 hours of its X-ray discovery aligns well with the 'Dark' nature of FXTs (Aryan et al., 2025, ApJS, 281, 20). The presented upper limit is calibrated using the field stars from the PanSTARRs DR2 and is not corrected for the expected Galactic foreground extinction of A_r = 0.14 mag in the direction of the transient (Schlafly & Finkbeiner, 2011). The methodology, details on the Lulin observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein-Probe mission are presented in Aryan et al., 2025, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69. View this GCN Circular online at https://gcn.nasa.gov/circulars/43278. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41368] GRB 251230A: 1.3m DFOT optical upper limit
by GCN Circulars 31 Dec '25

31 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43277 SUBJECT: GRB 251230A: 1.3m DFOT optical upper limit DATE: 25/12/31 09:38:27 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Kuntal Misra, Pankaj Pawar, Dhruv Jain, Debalina Kar (ARIES) report: We observed the field of GRB 251230A detected by Swift (Lanava et al. 2025, GCN 43252) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations began on 2025-12-30 at 21:36:37 UT, ~ 20.24 hours after the Swift trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We could not detect the optical emission in our stacked image within the error box of Swift/UVOT (Breeveld et al. 2025, GCN 43271). We obtain the following 3-sigma upper limit in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude =============================================================== 2025-12-30 21:36:37 ~20.24 R 300s*6 >22.3 The non-detection of the burst is consistent with Li et al. 2025, (GCN 43255); Lipunov et al. 2025, (GCN 43256); Busmann et al. 2025, (GCN 43258); Masi et al. 2025, (GCN 43260); Ghosh et al. 2025, (GCN 43262); Ma et al. 2025, (GCN 43265); Starling et al. 2025, (GCN 43267); He et al. 2025, (GCN 43269); Breeveld et al. 2025, (GCN 43271). The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalogue. View this GCN Circular online at https://gcn.nasa.gov/circulars/43277. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41367] Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
by GCN Circulars 31 Dec '25

31 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43276 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB DATE: 25/12/31 02:32:09 GMT FROM: Glowbug DEV <boyan.a.hristov(a)nasa.gov> B. Hristov (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 788833547/251231018 at 00:25:42.73 UT on 31 December 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to a Solar flare." View this GCN Circular online at https://gcn.nasa.gov/circulars/43276. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41366] GRB 251230A: Swift-XRT refined Analysis
by GCN Circulars 31 Dec '25

31 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43275 SUBJECT: GRB 251230A: Swift-XRT refined Analysis DATE: 25/12/31 01:48:14 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 5.6 ks of XRT data for GRB 251230A, from 92 s to 50.9 ks after the trigger. The data comprise 329 s in Windowed Timing (WT) mode (the first 6 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=7.1 (+/-0.5). At T+129 s the decay flattens to an alpha of 0.2 (+0.3, -1.1) before breaking again at T+194 s to a final decay with index alpha=1.51 (+/-0.05). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.80 (+/-0.06). The best-fitting absorption column is 4.4 (+1.3, -1.2) x 10^20 cm^-2, in excess of the Galactic value of 1.9 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.82 (+/-0.14) and a best-fitting absorption column of 5.7 (+3.6, -3.2) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (4.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 5.7 (+3.6, -3.2) x 10^20 cm^-2 Galactic foreground: 1.9 x 10^20 cm^-2 Excess significance: 2.0 sigma Photon index: 1.82 (+/-0.14) If the light curve continues to decay with a power-law decay index of 1.51, the count rate at T+24 hours will be 2.3 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.4 x 10^-14 (9.4 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01429020. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43275. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41365] GRB 251231A: Fermi GBM Final Real-time Localization
by GCN Circulars 31 Dec '25

31 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43274 SUBJECT: GRB 251231A: Fermi GBM Final Real-time Localization DATE: 25/12/31 00:36:41 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 SHORT GRB At 00:25:42 UT on 31 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251231A (trigger 788833547.728264 / 251231018). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 312.1, Dec = -46.0 (J2000 degrees, equivalent to J2000 20h 48m, -46d 00'), with a statistical uncertainty of 16.4 degrees. The angle from the Fermi LAT boresight is 12.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251231018/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251231018/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251231018/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43274. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41364] GRB 251222A: Mondy Optical Observations
by GCN Circulars 30 Dec '25

30 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43273 SUBJECT: GRB 251222A: Mondy Optical Observations DATE: 25/12/30 17:23:31 GMT FROM: Nicolai Pankov at IKI <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), E. Klunko (ISTP), A. Pozanenko (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 251222A (The Fermi GBM team, GCN 43186; Yang et. al, GCN 43188; Preis & Greiner, GCN 43190; Evans, GCN 43191; Beardmore et. al, GCN 43213; Frederiks et. al, GCN 43214; Guo et. al, GCN 43218; Neights et. al, GCN 43222) at z = 3.171 (Saccardi et. al, GCN 43204) in the R filter using the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy). The observations began on 2025-12-25 at 14:32 UT, i.e. ~2.91 days since trigger. The optical counterpart (Palmerio et. al, GCN 43189; An et. al, GCN 43194; Calapai et. al, GCN 43195; Durbak et. al, GCN 43197; Li et. al, GCN 43203; Saccardi et. al, GCN 43208; Gupta et. al, GCN 43207; Saccardi et. al, GCN 43204; Kumar et. al, GCN 43209; Pérez-Fournon et. al, GCN 43212; Gupta et al., GCN 43224; Globus et al., GCN 43225; Freeberg et al., GCN 43229; Volnova et al., GCN 43230; Busmann et al., GCN 43233; Lee et al., GCN 43236; Maksut et al., GCN 43237; Kumar et al., GCN 43250) is detected in the co-add image of 30x120 sec. The observation details and preliminary photometry are presented in the table below: Date UT start t-T0 Exp. Filter OT Err. UL (mid, days) (s) (3sigma) 2025-12-25 14:32:35 2.91441 30*120 R 21.66 0.12 22.9 The photometry was calibrated using nearby stars from USNO-B1.0 and not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43273. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41363] EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 30 Dec '25

30 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43272 SUBJECT: EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations DATE: 25/12/30 14:21:51 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> B.T. Wang (YNAO, CAS), J.P. Chen (SYSU), D. Zhu, K.J. Zhang (YNU), and Z.X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP251230a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Wang et al., GCN 43259) and Swift/BAT as GRB 251230A (Lanava et al., GCN 43252, Osborne et al., GCN 43263), and was followed by several optical telescopes (Li et al., GCN 43255, Lipunov et al., GCN 43256, Busmann et al., GCN 43258, Masi et al., GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265, Starling et al., GCN 43267, He et al., GCN 43269, Tak et al., GCN 43270, Breeveld et al., GCN 43271). The refined analysis of the WXT data shows that the event started at T0=2025-12-30T01:21:31 (UTC) and lasted for 72 s with a single pulse. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 1.21(-0.48/+0.59) x 10^22 cm^-2 and a photon index of 2.16 (-0.82/+0.89). The derived average unabsorbed 0.5-4 keV flux is 6.56 (-2.40, +2.80) x 10^(-9) erg/s/cm^2. The autonomous observation by the Follow-up X-ray Telescope (FXT) on board EP was performed at 2025-12-30T01:24:36 (UTC), about 3 minutes after T0. The exposure time of this observation is 1859 s. The on-ground analysis shows that an uncatalogued source was detected at R.A., Dec. = 179.8974, 11.4382 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic equivalent hydrogen column density of 2.0 x 10^20 cm^-2 and a photon index of 1.83 (-0.04/+0.04). The derived average unabsorbed 0.5-10 keV flux is 4.02 (-0.13/+0.13) x 10^(-11) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43272. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41362] GRB 251230A: Swift/UVOT detection
by GCN Circulars 30 Dec '25

30 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43271 SUBJECT: GRB 251230A: Swift/UVOT detection DATE: 25/12/30 13:45:04 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk> A.A. Breeveld (UCL-MSSL), N.P.M. Kuin (UCL-MSSL), S. Lanava (PSU) and M. De Pasquale (U. Messina) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251230A 76s after the BAT trigger (Lanava et al., GCN Circ. 43252). A bright, fading source consistent with the enhanced XRT position (Osborne et al., GCN Circ. 43263) and optical detections (Lanava et al., GCN 43252; Li et al., GCN 43255; Busmann et al., GCN 43258; Masi et al., GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265, He et al., GCN 43269) is detected in the initial UVOT exposures in the white, v, b, u and uvw1 filters. The burst is also detected in the UV grism and, while there is some contamination from other zeroth orders, we obtain a tentative redshift of z=1.73. The preliminary UVOT position is: RA (J2000) = 11:59:35.41 = 179.89756 (deg.) Dec (J2000) = +11:26:19.2 = 11.43867 (deg.) with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence). Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the finding chart (FC) and other early settled exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 76 226 147 13.61 ± 0.03 white 868 1017 286 15.63 ± 0.02 v 619 638 19 14.69 ± 0.07 b 545 564 20 14.78 ± 0.05 u_FC 288 538 246 13.77 ± 0.02 uvw1 668 687 19 15.2 ± 0.1 uvm2 643 1775 136 >18.8 uvw2 594 614 19 >17.7 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.024 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/43271. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41361] GRB251230A: 7DT optical upper limits
by GCN Circulars 30 Dec '25

30 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43270 SUBJECT: GRB251230A: 7DT optical upper limits DATE: 25/12/30 13:38:44 GMT FROM: Donggeun Tak <donggeun.tak(a)gmail.com> Donggeun Tak (SNU ARC/SNU), Myungshin Im (SNU ARC/SNU), YoungPyo Hong (SNU ARC/SNU), Hyeonho Choi (SNU ARC/SNU), Donghwan Hyun (SNU ARC/SNU), Gregory S.H. Paek (IfA, SNU ARC/SNU), Seo-Won Chang (SNU ARC/SNU), and Ji Hoon Kim (SNU ARC/SNU) report on behalf of the 7 Dimensional Telescope (7DT) team: We report optical follow-up observations of GRB251230A (GCN 43252; GCN 43263), conducted with the 7-Dimensional Telescope (7DT), located in Chile. The 7DT follow-up began at 06:52:54 UTC on 2025-12-30, corresponding to T0 + 5.5 hours, pointing to a region covering the target localization provided by Swift (GCN 43252) at RA, DEC = 179.89760 deg, 11.43870 deg. Initial observations were made with 12 units in 20 medium-band filters as well as g-, r-, and i-band filters (23 filters in total). The following table summarizes the derived 5-sigma upper limits: Filter Mag Mag_err Exposure Date Time ---------------------------------------------------------------------------------------------------- g >20.04 N/A 300s 2025-12-30T06:49:06.000 r >19.42 N/A 300s 2025-12-30T06:54:28.333 i >18.34 N/A 300s 2025-12-30T06:49:04.000 m400 >18.32 N/A 300s 2025-12-30T06:54:34.667 m425 >18.89 N/A 300s 2025-12-30T06:54:20.000 m450 >18.95 N/A 300s 2025-12-30T06:49:02.667 m475 >19.00 N/A 300s 2025-12-30T06:54:26.000 m500 >19.04 N/A 300s 2025-12-30T06:49:10.667 m525 >18.93 N/A 300s 2025-12-30T06:54:29.000 m550 >18.60 N/A 300s 2025-12-30T06:54:34.000 m575 >18.79 N/A 300s 2025-12-30T06:49:09.667 m600 >18.60 N/A 300s 2025-12-30T06:49:08.667 m625 >18.21 N/A 300s 2025-12-30T06:54:42.667 m650 >18.25 N/A 300s 2025-12-30T06:49:03.000 m675 >18.28 N/A 300s 2025-12-30T06:54:38.333 m700 >18.16 N/A 300s 2025-12-30T06:49:07.000 m725 >17.72 N/A 300s 2025-12-30T06:54:36.333 m750 >17.56 N/A 600s 2025-12-30T06:51:49.833 m775 >17.04 N/A 300s 2025-12-30T06:54:24.667 m800 >16.81 N/A 300s 2025-12-30T06:49:05.667 m825 >16.65 N/A 300s 2025-12-30T06:54:29.667 m850 >16.44 N/A 300s 2025-12-30T06:48:59.000 m875 >15.91 N/A 300s 2025-12-30T06:49:08.000 ---------------------------------------------------------------------------------------------------- No significant transient event was identified in the preliminary result. Preliminary analysis yields 5σ limiting magnitudes in the range of 15.91–20.04 mag depending on sky brightness and airmass. Photometric flux calibration was performed using synthetic photometry based on the Gaia DR3 XP catalog (Gaia Collaboration et al. 2022) within the AB magnitude system. Note that no extinction correction has been applied. The 7-Dimensional Telescope (7DT), located in Chile and comprising 20 wide-field telescopes equipped with 40 medium-bandwidth (~25nm) filters, aims to detect optical counterparts of GW sources and conduct the 7-Dimensional Sky Survey (7DS) of the Southern Hemisphere. Further information about the 7DT is available at https://7ds.snu.ac.kr/ and http://gwuniverse.snu.ac.kr/. View this GCN Circular online at https://gcn.nasa.gov/circulars/43270. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41360] GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
by GCN Circulars 30 Dec '25

30 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43269 SUBJECT: GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2 DATE: 25/12/30 13:23:01 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> L. He (NAOC), L. Izzo (INAF/OACN and DARK/NBI), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), J. An (NAOC), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Kadela (NOT & NBI) report on behalf of a larger collaboration: We observed the optical counterpart (Lanava et al., GCN 43252; Li et al., GCN 43255; Busmann et al., GCN 43258; Masi, GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265) of GRB 251230A / EP251230a (Lanava et al., GCN 43252; Wang et al., GCN 43259; Osborne et al., GCN 43263), using the Nordic Optical Telescope (NOT), equipped with the ALFOSC camera and spectrograph. We obtained three exposures of 300 s in the r-band starting on 2025 Dec 30 at 06:30:20 UT (5.144 hr after the Swift trigger). The afterglow is clearly detected with an AB magnitude of r = 20.75 +/- 0.02 mag, calibrated against nearby stars from the Pan-STARRS catalogue and not corrected for Galactic extinction. Compared to previous measurements, our photometry suggests rapid optical decay with power-law index ~1.95. A sequence of 4 spectra of 1200 s each was acquired, covering the wavelength range 3700-9600 AA. In a preliminary reduction of the spectra, we detect a continuum over the entire covered wavelength range. From detection in the blue down to ~3900 AA, and the lack of hydrogen absorption, we set a redshift upper limit z < 2.2. We do not identify clear metal absorption features. Further analysis is ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/43269. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41359] EP251229a: BOOTES-2 early optical upper limit
by GCN Circulars 30 Dec '25

30 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43268 SUBJECT: EP251229a: BOOTES-2 early optical upper limit DATE: 25/12/30 12:07:44 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es> I. Perez-Garcia, M.D. Caballero-Garcia, E. J. Fernandez-Garcia, R. Sanchez-Ramirez, S.-Y. Wu, S. Guziy, and A. J. Castro-Tirado (IAA-CSIC, Granada), Y.-D. Hu (GXU), C. Perez del Pulgar and A. Reina (Univ. of Malaga), M. Gritsevich (Univ. of Helsinki), R. Fernandez-Munoz (IHSM/UMA-CSIC), D. R. Xiong (Yunnan Observatories of CAS), and M. Jelinek (ASU-CAS, Ondrejov Obs.), on behalf of a larger collaboration, report: Following the detection of the X-ray transient EP251229a by Einstein Probe (Wang et al. GCN 43253), the 0.6m BOOTES-2/TELMA robotic telescope at IHSM UMA “La Mayora” (Malaga, Spain) automatically responded to this high-energy event starting on Dec 29, 20:11:10 UT (i.e. 12 min after detection). On a coadd image (14 x 60sec) at 20:50:40 UT (mid exposure time; i.e. 51 min after detection), nothing is detected down to 19.3 mag (clear filter) within the FXT error region (Wang et al. GCN 43264), in agreement with the deeper observations taken later on (Martin-Carrillo et al. GCN 43266). We would like to thank the staff at IHSM-/UMA-CSIC “La Mayora” for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/43268. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41358] GRB 251230A: GOTO optical upper limit
by GCN Circulars 30 Dec '25

30 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43267 SUBJECT: GRB 251230A: GOTO optical upper limit DATE: 25/12/30 11:26:15 GMT FROM: Rhaana Starling at U of Leicester <rlcs1(a)leicester.ac.uk> R. Starling, A. Kumar, G. Ramsay, D. O’Neill, B. P. Gompertz, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, S. Belkin, B. Godson, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration: We report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) that serendipitously covered the field of GRB 251230A detected by Swift (Lanava et al., GCN 43252; Osborne et al., GCN 43263) and likely coincident with an Einstein Probe trigger (Wang et al., GCN 43259). Two sets of observations were performed by GOTO-North at 2025-12-30 06:01:45 UT and 2025-12-30 06:16:08 UT. Each observation consisted of 4x45 s exposures in the GOTO L-band (400-700 nm). Images were processed using the GOTO pipeline. We do not detect the optical counterpart (Lanava et al., GCN 43252; Li et al., GCN 43255; Busmann et al., GCN 43258; Masi et al., GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265) down to 3-sigma limiting magnitudes of L >20.8 (AB) and L >20.6 (AB) at 4.7 hours and 4.9 hours post-trigger, respectively. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/43267. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41357] EP251229a: NOT optical upper limits
by GCN Circulars 30 Dec '25

30 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43266 SUBJECT: EP251229a: NOT optical upper limits DATE: 25/12/30 10:31:06 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> A. Martin-Carrillo (UCD), J. Chacón (PUC), Z.P. Zhu, D. Xu (NAOC), G. Corcoran (UCD), F. E. Bauer (SSI and UTA), P.G. Jonker (Radboud) report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP251229a (Wang et al., GCN 43253) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were obtained in the SDSS i and z bands consisting of 5x200 s exposures, starting on 2025-12-29 at 23:36:08 UTC (3.622 hours after the WXT trigger). No new source is detected within or at the border of the EP/FXT uncertainty region (Wang et al., GCN 43253). From the stacked images we obtain the following 3-sigma upper limits:  i > 24.0 z > 23.1 These upper limits are in AB magnitudes and were calibrated using nearby stars from the Pan-STARRS catalog and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43266. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41356] GRB 251230A / EP251230a: SVOM/VT optical observation
by GCN Circulars 30 Dec '25

30 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43265 SUBJECT: GRB 251230A / EP251230a: SVOM/VT optical observation DATE: 25/12/30 09:58:05 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, H. L. Li, Z. H. Yao, 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), J. X. Cao (GXU), W. L. Zhang (PMO) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of GRB 251230A / EP251230a detected by Swift/BAT and EP/WXT (Lanava et al., GCN 43252; Wang et al., GCN 43259; Osborne et al., GCN 43263). SVOM/VT began observing the field at 2025-12-30T03:13:20 UTC, 1.861 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X-band data available, the optical counterpart (Li et al., GCN 43255; Busmann et al., GCN 43258; Masi, GCN 43260; Ghosh et al., GCN 43262) was clearly detected in both VT_B and VT_R bands. The magnitudes are: mid time (s) | exposure time (s) | band | mag (AB) | mag err -------------|-------------------|------|----------|-------- 6874 | 50 | VT_B | 19.11 | 0.04 8174 | 50 | VT_B | 19.53 | 0.05 6874 | 50 | VT_R | 18.57 | 0.03 8174 | 50 | VT_R | 19.07 | 0.05 Our photometry was 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 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/43265. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41355] EP251229a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 30 Dec '25

30 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43264 SUBJECT: EP251229a: refined analysis of the EP-WXT and EP-FXT observations DATE: 25/12/30 09:05:29 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> B.T. Wang (YNAO, CAS), J.P. Chen (SYSU), D. Zhu, K.J. Zhang (YNU), and Z.X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP251229a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Wang et al., GCN 43253) and followed by an optical telescope (Lipunov et al., GCN 43254). The refined analysis of the WXT data shows that the event started at T0=2025-12-29T19:54:09 (UTC) and lasted for 173 s with a single pulse. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 5.3 (-2.2/+2.6) x 10^21 cm^-2 and a photon index of 2.3 (-0.68/+0.77). The derived average unabsorbed 0.5-4 keV flux is 1.62 (-0.41/+0.87) x 10^(-9) erg/s/cm^2. The autonomous observation by the Follow-up X-ray Telescope (FXT) was performed at 2025-12-29T20:01:28 (UTC), about 7 minutes after T0. The exposure time of this observation is 855 s. The on-ground analysis shows that an uncatalogued source was detected at R.A., Dec. = 124.1027, 37.2068 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic equivalent hydrogen column density of 6.0 x 10^20 cm^-2 and a photon index of 1.89 (-0.13/+0.13). The derived average unabsorbed 0.5-10 keV flux is 3.46 (-0.37/+0.40) x 10^(-11) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43264. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41354] GRB 251230A: Enhanced Swift-XRT position
by GCN Circulars 30 Dec '25

30 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43263 SUBJECT: GRB 251230A: Enhanced Swift-XRT position DATE: 25/12/30 08:02:58 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 1379 s of XRT Photon Counting mode data and 1 UVOT images for GRB 251230A, 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 = 179.89737, +11.43831 which is equivalent to: RA (J2000): 11h 59m 35.37s Dec (J2000): +11d 26' 17.9" with an uncertainty of 2.2 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/43263. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41353] GRB 251230A: Early optical counterpart detection by LCO.
by GCN Circulars 30 Dec '25

30 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43262 SUBJECT: GRB 251230A: Early optical counterpart detection by LCO. DATE: 25/12/30 05:52:21 GMT FROM: ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994(a)gmail.com> Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Rahul Gupta (NASA GSFC), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES) on behalf of a larger collaboration. We observed the field of the GRB 251230A triggered by Swift (Lanava et al., GCN 43252) in B, V, and r filter of the 1-m Sinistro telescope and 0.4-m SCICAM QHY600 at the Las Cumbres Observatory Global Telescope (LCOGT) node located at South African Astronomical Observatory (SAAO). The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel) and the 0.4 m SCICAM QHY600 is equipped with 9576 x 6388 pixel CCD (FOV: 1.9 x 1.2 degrees, scale: 0.74 arcsec/pixel). Observations began on October 13, 2025, starting from 0.84 hours after the GRB trigger. Further observations are still ongoing. We clearly detect the optical transient (OT) reported by GCNs (Lanava et al., GCN 43252, Li et al., GCN 43255, Masi et al., GCN 43260). ----------------------------------------------------------------------------------------------------- |Date| |JDstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude| ----------------------------------------------------------------------------------------------------- 2025-12-30 2461039.59159 0.84 1 x 300 r r = 17.20 +/- 0.01 2025-12-30 2461039.60333 1.12 2 x 300 r r = 17.64 +/- 0.11 ----------------------------------------------------------------------------------------------------- The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43262. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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