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[vsnet-grb-info 41634] Fermi GRB 260127B: Global MASTER-Net observations report
by GCN Circulars 27 Jan '26

27 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43534 SUBJECT: Fermi GRB 260127B: Global MASTER-Net observations report DATE: 26/01/27 21:30:30 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) started inspect of the Fermi GRB 260127B ( Fermi GBM team, GCN 43533) errorbox 2657 sec after notice time and 2678 sec after trigger time at 2026-01-27 20:47:11 UT, with upper limit up to 19.7 mag. The observations began at zenith distance = 7 deg. The sun altitude is -37.8 deg. The galactic latitude b = 60 deg., longitude l = 125 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3117123 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 2709 | 2026-01-27 20:47:11 | MASTER-Tunka | (12h 37m 21.08s , +57d 00m 17.6s) | C | 60 | 19.5 | 2822 | 2026-01-27 20:49:04 | MASTER-Tunka | (12h 51m 46.69s , +57d 02m 10.2s) | C | 60 | 19.7 | 2897 | 2026-01-27 20:50:19 | MASTER-Tunka | (12h 19m 40.16s , +58d 55m 09.9s) | C | 60 | 19.7 | 2970 | 2026-01-27 20:51:32 | MASTER-Tunka | (12h 34m 49.83s , +58d 54m 52.1s) | C | 60 | 19.7 | 3049 | 2026-01-27 20:52:51 | MASTER-Tunka | (12h 27m 48.95s , +55d 06m 33.8s) | C | 60 | 19.7 | 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/43534. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41633] GRB 260127B: Fermi GBM Final Real-time Localization
by GCN Circulars 27 Jan '26

27 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43533 SUBJECT: GRB 260127B: Fermi GBM Final Real-time Localization DATE: 26/01/27 20:13:04 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 SHORT GRB At 20:02:32 UT on 27 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260127B (trigger 791236957.568148 / 260127835). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 190.4, Dec = 56.9 (J2000 degrees, equivalent to J2000 12h 41m, 56d 53'), with a statistical uncertainty of 5.2 degrees. The angle from the Fermi LAT boresight is 109.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127835/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127835/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127835/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43533. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41632] GRB 260127A: Prompt enhanced Swift-XRT position
by GCN Circulars 27 Jan '26

27 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43532 SUBJECT: GRB 260127A: Prompt enhanced Swift-XRT position DATE: 26/01/27 19:08:40 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-XRT team: Using 1.6 ks of promptly downlinked XRT event data for GRB 260127A, we find an enhanced XRT position of the afterglow: RA, Dec: 231.87962, 6.76262 which is equivalent to: RA (J2000) = 15h 27m 31.11s Dec (J2000) = 00h 27m 03.03s with an uncertainty of 1.9 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/1444088. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43532. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41631] Swift GRB 260127A: Global MASTER-Net observations report
by GCN Circulars 27 Jan '26

27 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43531 SUBJECT: Swift GRB 260127A: Global MASTER-Net observations report DATE: 26/01/27 19:08:27 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 260127A ( N. J. Klingler et al., GCN 43529) errorbox 3854 sec after notice time and 3972 sec after trigger time at 2026-01-27 18:56:47 UT, with upper limit up to 17.1 mag. The observations began at zenith distance = 77 deg. The sun altitude is -52.1 deg. The galactic latitude b = 47 deg., longitude l = 12 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3117002 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 3988 | MASTER-Tunka | C | 30 | 17.1 | 4030 | MASTER-Tunka | C | 30 | 17.1 | 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/43531. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41630] GRB 260127A: LCO optical afterglow discovery
by GCN Circulars 27 Jan '26

27 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43530 SUBJECT: GRB 260127A: LCO optical afterglow discovery DATE: 26/01/27 19:06:16 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Saccardi (CEA/Irfu), D. B. Malesani (DAWN/NBI and Radboud) report on behalf of the SVOM mission team: We observed the field of GRB 260127A (Fermi GBM team, GCN 43528; Klingler et al., GCN 43529) with the LCO 1-m telescope at Siding Spring Observatory equipped with the Sinistro instrument. Our observation started on 2026-01-27 at 18:12:42 (about 22 min after the trigger) and we obtained 3x200 s exposures in the SDSS r filter. An uncatalogued optical transient is detected within the XRT error box at the following coordinates (J2000): RA = 15:27:31.14 Dec = +06:45:45.49 with an uncertainty of 0.3". No object is visible at these coordinates in the much deeper archival images from the Legacy Survey, indicating that this object is most likely the optical afterglow of GRB 260127A. We measure the following magnitude, calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction: r = 20.45 +/- 0.20 AB (mid-time of 27.3 min after the trigger). Further observations are planned. This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/43530. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41629] GRB 260127A: Swift detection of a burst
by GCN Circulars 27 Jan '26

27 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43529 SUBJECT: GRB 260127A: Swift detection of a burst DATE: 26/01/27 18:17:19 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> N. J. Klingler (GSFC/UMBC/CRESSTII), R. Gupta (NASA GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester), T. M. Parsotan (GSFC) and B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 17:50:34 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 260127A (trigger=1444088). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 231.857, +6.758 which is RA(J2000) = 15h 27m 26s Dec(J2000) = +06d 45' 30" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed no structure initially, typical of an image trigger, with a more classic pulse structure starting at ~T0+20 sec. The emission has a duration of about 50 sec. The peak count rate was ~1460 counts/sec (15-350 keV), at ~33 sec after the trigger. The XRT began observing the field at 17:54:00.1 UT, 205.3 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 231.87885, 6.76345 which is equivalent to: RA(J2000) = 15h 27m 30.92s Dec(J2000) = +06d 45' 48.4" with an uncertainty of 3.5 arcseconds (radius, 90% containment). This location is 80 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 (4.07 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.2 (+2.30/-2.03) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 4.58e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 213 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 0.049. Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu) Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/43529. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41628] GRB 260127A: Fermi GBM Final Real-time Localization
by GCN Circulars 27 Jan '26

27 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43528 SUBJECT: GRB 260127A: Fermi GBM Final Real-time Localization DATE: 26/01/27 18:01:38 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 17:51:07 UT on 27 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260127A (trigger 791229072.735026 / 260127744). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 226.9, Dec = -2.2 (J2000 degrees, equivalent to J2000 15h 07m, -2d 12'), with a statistical uncertainty of 5.1 degrees. The angle from the Fermi LAT boresight is 79.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127744/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127744/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127744/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43528. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41627] GRB 260125A: Swift-XRT observations
by GCN Circulars 27 Jan '26

27 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43527 SUBJECT: GRB 260125A: Swift-XRT observations DATE: 26/01/27 15:36:17 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), S. Campana (INAF-OAB) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/GBM-detected burst GRB 260125A (Fermi GBM Team, GCN 43510), collecting 3.1 ks of Photon Counting (PC) mode data between T0+64.9 ks and T0+86.3 ks. No X-ray sources have been detected consistent with the GOTO counterpart position (Gompertz et al., GCN 43514). The 3-sigma upper limit in the field is 0.003 ct s^-1, corresponding to a 0.3-10 keV observed flux of 1.0e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum). Five uncatalogued sources were detected too far from the GOTO position, and not showing significant signs of fading to be likely afterglow candidates. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021899. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43527. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41626] EP260126a: EP-FXT follow-up observation
by GCN Circulars 27 Jan '26

27 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43526 SUBJECT: EP260126a: EP-FXT follow-up observation DATE: 26/01/27 13:40:40 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> S.Y. Fu (HUST), Z.M. Wang (BNU), J.H. Wu (GZHU), H.Y. Liu, H.W. Pan (NAOC, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of EP260126a (detected by EP-WXT, GCN 43520) about 19.1 hours after the WXT detection, with an exposure time of 5.8 ks. The FXT telemetry data show that an uncatalogued source was detected within the WXT error circle at R.A. = 103.7551, DEC = 37.7053 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The FXT X-ray spectrum of this uncatalogued source can be fitted with an absorbed powerlaw with a hydrogen column density fixed at the Galactic value of 1.21 x 10^21 cm^-2 and a photon index of 1.76 (+/- 0.20). The derived unabsorbed 0.5-10 keV flux is approximately 5.65 (+1.0/-0.85) x 10^-13 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Multi-band follow-up observations are encouraged. 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/43526. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41625] EP260126a: Optical upper limit with Kinder observations
by GCN Circulars 27 Jan '26

27 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43525 SUBJECT: EP260126a: Optical upper limit with Kinder observations DATE: 26/01/27 12:48:50 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> M.-H. Lee, 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, A. Sankar.K, 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 EP260126a (Fu et al., GCN 43520) 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 in r-band started at 13:53 UTC on the 26 January 2026 (MJD 61066.578), 9.46 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 used AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform PSF photometry. We do not detect any new or uncataloged sources within the 20" EP-FXT localization circle. The details of the observations and the measured 3-sigma upper limits (in the AB system) are as follows: Telescope | Filter | MJD (start)| t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | r | 61066.578 | 9.46 | 300 * 6 | >21.0 | 2".8 | 1.04 SLT | i | 61066.606 | 10.14 | 300 * 3 | >20.3 | 2".5 | 1.03 The non-detections in our observations are consistent with those reported by Zhu et al. (GCN 43521), Globus et al. (GCN 43522), Eyles-Ferris et al. (GCNs 43523 and 43524). The presented upper limits are calibrated using the field stars from the Pan-STARRS catalog and are not corrected for the expected Galactic foreground extinction of A_r = 0.24 and A_i = 0.18 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/43525. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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