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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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