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[vsnet-grb-info 41663] GRB 260128B: SVOM detection of a burst through offline search
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43561 SUBJECT: GRB 260128B: SVOM detection of a burst through offline search DATE: 26/01/29 19:08:31 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet (IRAP), S. Le Stum, A. Coleiro (APC), O. Godet (IRAP),report on behalf of the SVOM team: The SVOM/ECLAIRs telescope detected a transient source, labelled GRB 260128B, starting at 2026-01-28T06:48:34.72 UTC (T0), through an offline search with the event-by-event data downloaded through the X-band ground station. The burst was detected within several energy ranges and timescales. The best detection is obtained by the Image Trigger with a signal-to-noise ratio of 7.5 within 4-20 keV over a time window of 10.24 seconds starting at T0-10.24s. The lightcurve shows a single peaked structure lasting around 4s. The localization of the source is RA, Dec = 27.734, -25.867 degrees: RA (J2000) = 01h50m56.16s Dec (J2000) = -25d52m01.20s with a 90% C.L. radius of 12.0 arcmin (including systematic error of 6 arcmin added in quadrature). We note that no bright catalogued X-ray sources are found in the error box. The Space 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. ECLAIRs was developed jointly by APC, CEA, CNES, and IRAP. The SVOM point of contact for this event is : Sébastien Le Stum : lestum at apc.in2p3.fr Please contact him by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/43561. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41662] GRB 260129A: Fermi GBM Final Localization
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43560 SUBJECT: GRB 260129A: Fermi GBM Final Localization DATE: 26/01/29 18:53:30 GMT FROM: Christian Malacaria at INAF-OAR <cmalacaria.astro(a)gmail.com> "The Fermi GBM team reports the detection of a likely Long GRB. At 04:33:12 UT on 29 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260129A (trigger 791353997 / 260129190). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 160.4, Dec = -46.8 (J2000 degrees, equivalent to J2000 10h 41m, -46d 48'), with a statistical uncertainty of 9.7 degrees. The angle from the Fermi LAT boresight is 20.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260129190/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260129190/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260129190/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/43560. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41661] IPN triangulation of GRB 260127B (short)
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43559 SUBJECT: IPN triangulation of GRB 260127B (short) DATE: 26/01/29 18:13:36 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, and A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, report: The short-duration GRB 260127B (Fermi-GBM detection: The Fermi GBM team, GCN 43533) was detected by Fermi (GBM trigger 791236957) and Konus-Wind at about 72153 s UT (20:02:33). We have triangulated it to a Konus-GBM annulus centered at RA(2000)=104.669 deg (06h 58m 40s) Dec(2000)=+21.845 deg (+21d 50' 41"), whose radius is 72.490 +/- 0.104 deg (3 sigma). The annulus combined with the Fermi-GBM final position (GCN 43533; glg_healpix_all_bn260127835_v00) gives ~6.8 sq. deg (3 sigma) localization region. The the optical source detected by GOTO (GOTO26aih/AT2026bnn, GCN 43538) is outside the IPN annulus. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB260127_T72154/IPN/ View this GCN Circular online at https://gcn.nasa.gov/circulars/43559. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41660] GRB 260127B: Swift-XRT observations
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43558 SUBJECT: GRB 260127B: Swift-XRT observations DATE: 26/01/29 15:59:58 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), S. Campana (INAF-OAB), A. Melandri (INAF-OAR), T. Sbarrato (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 260127B (The Fermi GBM team, GCN Circ. 43533), collecting 985 s of Photon Counting (PC) mode data between T0+70.4 ks and T0+71.4 ks. No X-ray sources have been detected consistent with the tentative GOTO optical afterglow candidate (O’Neill et al, GCN Circ. 43538). The 3-sigma upper limit in the field ranges from ~0.01 to ~0.02 ct s^-1, corresponding to a 0.3-10 keV observed flux of 5.0e-13 to 6.9e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum). 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/00021900. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43558. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41659] GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43557 SUBJECT: GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations DATE: 26/01/29 15:04:48 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), A. Moskvitin (SAO RAS), N. Pankov (IKI), A. Tarasenkov (INASAN), I. Sokolov (INASAN, KIAM), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN collaboration: We observed the field of the Swift/Fermi/GBM GRB 260127A (Fermi GBM Team, GCN Circ. 43528; Klingler et al., GCN Circ. 43529; Osborne et al., GCN 43535; D'Ai et al, GCN 43539; Trigg, GCN 43546) in R-band with the RC500 telescope of the INASAN-Kislovodsk observatory starting on 2026-01-27 (UT) 23:20:50, in Rc-band with the Zeiss-1000 of the SAO RAS starting on 2026-01-28 (UT) 01:01:40, and in clear light with the 0.8-meter K-800 telescope of the Terskol observatory of INASAN 2026-01-28 (UT) 01:46:18. The optical counterpart reported previously (Saccardi & Malesani, GCN 43530; Lipunov et al., GCNs 43531, 43548; Wu et al., GCN 43537; Hagio et al., GCN 43540; Malesani et al, GCN 43543; Magnani et al., GCN 43544) is clearly detected in the stacked frame of the Zeiss-1000 and is not detected in the stacked frames of the RC500 and K-800 telescopes. Preliminary photometry and observational details are the following: Date UT start t-T0 Exp. Filter Obj. Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2026-01-27 23:20:50 0.30822 110*120 R n/d n/d 21.9 INASAN-Kislovodsk/RC500 2026-01-28 01:01:40 0.32599 15*300 Rc 22.00 0.22 22.7 SAO RAS/Zeiss-1000 2026-01-28 01:46:18 0.35748 94*30 Clear n/d n/d 21.2 Terskol/K800 The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. We would like to thank the SAO RAS engineering team: Afanasieva I. V., Pritychenko M. A., Egorov V. A., Shaldyrvan I. V. for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/43557. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41658] GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43556 SUBJECT: GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection DATE: 26/01/29 14:50:07 GMT FROM: mariaedvige.ravasio(a)ru.nl M. E. Ravasio (ICE-CSIC and Radboud Univ.), P.G. Jonker (Radboud Univ.) and E. Burns (LSU), C. Malacaria (INAF-OAR) report on behalf of the Fermi-GBM Team: Fermi-GBM had full spatial and temporal coverage of the transient EP260128a detected by EP-WXT (H. Zhou et al., GCN 43549; H. Zhou et al., GCN 43554). There was no Fermi-GBM onboard trigger around the refined EP starting time at T0 = 2026-01-28T23:38:19 UTC (H. Zhou et al., GCN 43554). The GBM Targeted Search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [-50;+500] s from T0, seeking signals between 64 ms and 32.768 s in duration. A transient was found, with the most significant signal at T0+145 s on a 16 s timescale, with a false alarm rate of 1.1e-05 Hz, although there is significant evidence of an earlier start of the emission. The light curve is multi-peaked, and a significant signal is also found at T0+70 s with FAR of 6.5e-05 Hz. The localisation is consistent with the EP one, with a spatial association probability of 99.3%. 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/43556. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41657] EP260128a: NOT optical counterpart candidate
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43555 SUBJECT: EP260128a: NOT optical counterpart candidate DATE: 26/01/29 11:54:22 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He, J. An, X. Liu, S.Q. Jiang, Z.P. Zhu, D. Xu (NAOC), S.Y. Fu (HUST), J.P.U. Fynbo (DAWN/NBI), N. Pyykkinen (NOT) report on behalf of a large collaboration: We observed the field of EP260128a (Zhou et al., GCN 43549) using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started at 00:13:10 UT on 2026-01-29, i.e., 33.18 minutes after the EP trigger, and we obtained 9 x 90 s frames in the Sloan r-band and 9 x 100 s frames in the Sloan z- band. The stacked r- and z- band images have 3-sigma depth of r ~ 24.1 and z ~ 23.5, calibrated with nearby Pan-STARRS1 DR2 stars and not corrected for Galactic extinction. A new optical source is detected in the stacked z-band image within the EP/FXT error circle (Zhou et al., GCN 43554) at coordinates RA = 08:33:18.08 (128.32533) DEC = -10:16:32.3 (-10.27565) to ~ 4.2-sigma and we measured z = 23.07 +/- 0.26 (AB) at 1.004 hrs post-trigger. This source is not present in the z-band Legacy Survey DR11 early image v2, which is a bit deeper than the z-band NOT image. This source is also not present in the stacked r-band NOT image, as well as the r-band Legacy Survey image that is deeper than the NOT image. Considering the r-band non-detection and the z-band (weak) detection for the NOT candidate, EP260128a might be a high-redshift (i.e., z > ~5) event. We also note that the counterpart candidate by Liverpool Telescope (Eyles-Ferris et al., GCN 43553) is not present in neither r-band nor z-band stacked NOT image. Further optical and near-infrared follow-ups are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/43555. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41656] EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43554 SUBJECT: EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations DATE: 26/01/29 10:01:54 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO, CAS), T. Wu, H.-C. Ding (AHNU), Z.-X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260128a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Zhou et al., GCN 43549). The refined analysis of the WXT data shows that the event started at T0=2026-01-28T 23:38:19(UTC), and lasted for approximately 100 seconds, after which the WXT light curve was interrupted due to the autonomous follow-up observation. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 5.84×10^20 cm^-2 and a photon index of 0.05 +/- 0.73. The derived average unabsorbed 0.5-4 keV flux is 6.98(-4.40/+11.93)×10^(-9) erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously at 2026-01-28T23:43:01(UTC, T0+282 s). The exposure time of this observation is 2102s. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 128.3253, DEC = -10.2750 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent with the WXT position. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 5.84×10^20 cm^-2 and a photon index of 1.99 +/-0.06. The derived average unabsorbed 0.5-10 keV flux is (2.76 +/- 0.15)×10^(-11) erg/s/cm^2. The best-fitted FXT spectra show no additional absorption is required. Further FXT follow-up observations have been arranged. Although a faint counterpart of EP260128a has been reported (Lipunov et al., GCN 43550; Quirola-Vasquez et al., GCN 43552; Eyles-Ferris et al., GCN 43553), further multi-band follow-up observations are encouraged to explore the nature of EP260128a. 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/43554. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41655] EP260128a: Liverpool Telescope optical observations and possible counterpart
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43553 SUBJECT: EP260128a: Liverpool Telescope optical observations and possible counterpart DATE: 26/01/29 09:33:37 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris and R. L. C. Starling (Leicester) report on behalf of a larger collaboration: We observed the field of EP260128a (Zhou et al., GCN 43549) with the 2m Liverpool Telescope on La Palma using the IO:O instrument. We obtained 6x150s exposures in each of the SDSS r’ and SDSS g’ filters starting at 2026-01-28 23:56:39 UT, approximately 16.6 minutes after the X-ray detection. We performed image subtraction on the stacked images using reference images from Pan-STARRS and Legacy DR11 and also compared the stacked and reference images manually. In the r’ stack and within the EP/FXT localisation, we tentatively identify a low significance source at a position RA 08:33:18.17 (128.32569 deg) Dec -10:16:19.3 (-10.27202 deg) The source is detected to ~2.6-sigma and we measure r’ = 22.92 +/- 0.38. The source is not visible in the g’ stack (started ~18 minutes later). We derive 3-sigma upper limits for our stacked images of r’ > 22.8 and g’ > 22.5 with AB photometry calibrated to Pan-STARRS and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43553. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41654] EP260128a: LCO optical upper limits
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43552 SUBJECT: EP260128a: LCO optical upper limits DATE: 26/01/29 07:47:19 GMT FROM: Jonathan Quirola at Radboud University <jaquirola1990(a)gmail.com> J. A. Quirola-Vasquez (Radboud), J. N. D. van Dalen (Radboud), J. Chacón(PUC), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), A. J. Levan (Radboud), D. B. Malesani (DAWN/NBI and Radboud), and F. E. Bauer (SSI and UTA) report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP260128a (Zhou et al., GCN 43549) using an LCO 1m telescope located at the Cerro Tololo Inter-American Observatory (Chile) equipped with the SINISTRO instrument. A series of 6x300 s exposures was taken in each of the SDSS-r filter, starting on 2026-01-29 at 02:05:48 UT (2.43 hr after the trigger). No new source is detected within or at the border of the EP/FXT uncertainty region (Zhou et al., GCN 43549) compared to Legacy DR11. From the stacked images, we obtain the following 3-sigma upper limits:  r > 22.5 These upper limits are in AB magnitudes, 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/43552. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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