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

[vsnet-grb-info 41644] GRB 260127B: Swift ToO observations
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43542 SUBJECT: GRB 260127B: Swift ToO observations DATE: 26/01/28 15:34:04 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 Fermi/GBM-detected event GRB 260127B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021900 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 Fermi/GBM 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/43542. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41643] EP260126a: Seimei/TriCCS optical upper limit
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43541 SUBJECT: EP260126a: Seimei/TriCCS optical upper limit DATE: 26/01/28 14:52:16 GMT FROM: Kenta Taguchi <kentagch(a)kusastro.kyoto-u.ac.jp> Kenta Taguchi (Kyoto University) reports on behalf of a larger collaboration: We observed the field of EP260126a detected by the Einstein Probe (Fu et al., GCN 43520) using the Tricolor CMOS Camera and Spectrograph (TriCCS) on the 3.8-m Seimei Telescope at the Okayama Observatory of Kyoto University. Our observation started at 13:30:04 UT on 2026-01-26 (MJD = 61066.5625). For each band, we took 30-second exposures 62 times (i.e., the total exposure time is 1860 s = 31 min). From our preliminary analysis, the 5-sigma limiting magnitudes are 21.74, 21.36, and 21.33 AB mag for g, r, and i-band, respectively. We detected no transient sources in the FXT error circle. View this GCN Circular online at https://gcn.nasa.gov/circulars/43541. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41642] GRB 260127A : MITSuME Akeno optical afterglow candidate detection
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43540 SUBJECT: GRB 260127A : MITSuME Akeno optical afterglow candidate detection DATE: 26/01/28 11:16:16 GMT FROM: hagio.h.ffca(a)m.isct.ac.jp H. Hagio, I. Takahashi, M. Sasada, H. Seki, Y. Kubo, A. Ochi, R. Kato, S. Joshima, Y. Yatsu and N. Kawai (Science Tokyo) report on behalf of the MITSuME collaboration: We observed the field of GRB 260127A detected by Fermi (Fermi GBM team et al., GCN 43528) and Swift ( Klingler et al., GCN 43529) with the optical three-color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50-cm telescope Akeno. The observation started at 2026-01-27 17:52:58 UT (2.4 min after the trigger). We stacked the images taken under good conditions. We detected a point source in the Rc-band image at a position of the reported candidate (Saccardi et al., GCN 43530; Wu et al., GCN 43537). Here we report the preliminary magnitude of the source and the 5-sigma upper-limits as follows. T0+[sec] | MID-UT | T-EXP[sec] | magnitudes --------------------------------------------------------------------------------------------------------------- 1245 | 2026-01-27 18:11:19 | 1620 | g'>19.2,Rc=19.4+/-0.2, Ic>18.7 --------------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the trigger T-EXP: Total exposure time We used the PS1 catalog for flux calibration. The catalog magnitudes in PS1 g, r and i bands were converted to our g', Rc and Ic band magnitudes following Tonry et al. (2012), Table 6. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ; https://github.com/MNiwano/Eclaire) View this GCN Circular online at https://gcn.nasa.gov/circulars/43540. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41641] GRB 260127A: Swift-XRT refined Analysis
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43539 SUBJECT: GRB 260127A: Swift-XRT refined Analysis DATE: 26/01/28 10:27:05 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU), D.N. Burrows (PSU), S. Lanava (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), S. Campana (INAF-OAB), A. Melandri (INAF-OAR) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 9.4 ks of XRT data for GRB 260127A, from 226 s to 51.7 ks after the trigger. The data comprise 102 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The late-time light curve (from T0+5.2 ks) is consistent with a constant source of mean count rate 3.6e+00 ct/sec. A power-law fit gives an index of 3.08 (+0.03, -3.08). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.14 (+0.20, -0.19). The best-fitting absorption column is 8.0 (+4.6, -3.9) x 10^20 cm^-2, in excess of the Galactic value of 4.1 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.75 (+/-0.06) and a best-fitting absorption column of 1.32 (+0.21, -0.20) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.0 x 10^-11 (4.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.32 (+0.21, -0.20) x 10^21 cm^-2 Galactic foreground: 4.1 x 10^20 cm^-2 Excess significance: 7.6 sigma Photon index: 1.75 (+/-0.06) The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01444088. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43539. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41640] GRB 260127B: GOTO candidate optical counterpart
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43538 SUBJECT: GRB 260127B: GOTO candidate optical counterpart DATE: 26/01/28 10:22:31 GMT FROM: d.s.oneill(a)bham.ac.uk D. O’Neill, B. P. Gompertz, G. Ramsay, M. Kennedy, D. Steeghs, J. Lyman, R. Starling, K. Ackley, M. Dyer, K. Ulaczyk, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein, A. Kumar, M. Pursiainen report on behalf of GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the short GRB 260127B (Fermi GBM Team, GCN 43533). Observations covering the localisation area began at 2026-01-28 00:20:53 UT (+4.31h post trigger) and continued through to 2026-01-28 05:10:59 (+9.14h post trigger). 141 images were taken, across 9 unique pointings, covering 242.7 square degrees within the 90% localisation contour. ~61.4% of the total 2D localisation probability was covered, with an average 5-sigma depth of 20.2 mag. Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. We identify one candidate optical counterpart, GOTO26aih (AT2026bnn), within the 90% probability contour at coordinates RA = 12:49:52.73, Dec = +66:44:58.87, equivalent to RA = 192.469711, Dec =66.74969 degrees. This position lies on the 84th percentile probability contour of the Fermi/GBM localisation map. The source was initially detected with L = 19.15 ± 0.14 AB mag (t0+5.66h), before fading to L = 19.82 ± 0.11 mag (t0+7.91h). The measured rate of decay is t^-1.66 ± 0.97. We find no evidence of the source prior to the GRB trigger time in the most recent GOTO observations taken at 2026-01-20 06:01:17 (t0-7.6 days) down to a 5-sigma depth of >20.8 AB mag. We also find no evidence for pre-GRB emission in the ZTF observations provided by the Lasair broker (Smith et al. 2019), or the ATLAS forced photometry server (Shingles et al. 2021). GOTO26aih/AT2026bnn is spatially coincident with the galaxy SDSS J124952.79+664500.4, offset by 1.5” from the core. This galaxy has a measured spectroscopic redshift of z = 0.12 (DESI Collaboration, 2025). A summary of our observations is presented below. +------------------------------------------------------------+ | Observation time (UT) | t-t0 | filter | mag | +------------------------------------------------------------+ | 2026-01-20 06:01:17 | -181.42h | L | >20.8 | | 2026-01-28 01:01:13 | +5.66h | L | 19.15 ± 0.14 | | 2026-01-28 02:01:23 | +6.78h | L | 19.79 ± 0.14 | | 2026-01-28 03:01:22 | +7.91h | L | 19.82 ± 0.11 | +-------------------------------------------------------------+ Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and 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/43538. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41639] GRB 260127A: SVOM/C-GFT optical observations
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43537 SUBJECT: GRB 260127A: SVOM/C-GFT optical observations DATE: 26/01/28 04:44:46 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C. Wu (NAOC), Z. Kang (CHO), L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li, Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of GRB 260127A detected by Fermi/GBM (Fermi GBM team, GCN 43528) and Swift/BAT (Klingler et al., GCN 43529) with LATIOS on SVOM/C-GFT. Observations started at 2026-01-27T19:07:40 UTC, ~76.55 min after the trigger. The optical counterpart (Saccardiet et al., GCN 43530), consistent with XRT position (Evans et al., GCN 43532; Osborne et al., GCN 43535), was detected in our stacked i-band image. The magnitude is: | Mid_t-T0(hr) | exposure time (s) | band | mag (AB) | mag_err| |--------------|-------------------|------|----------|--------| | 2.24 | 30x90s | i | 20.37 | 0.20 | Our detection is deeper than the upper limit reported by Lipunov et al. (GCN 43532). The photometry was calibrated against nearby stars from UCAC4 catalog and no correction for Galactic dust extinction was applied. We thank the observation assistants Yin-Huai Hao Chun-Lei Guo at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/43537. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41638] GRB 260127A: SVOM/C-GFT optical observations
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43537 SUBJECT: GRB 260127A: SVOM/C-GFT optical observations DATE: 26/01/28 04:44:46 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C. Wu (NAOC), Z. Kang (CHO), L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li, Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of GRB 260127A detected by Fermi/GBM (Fermi GBM team, GCN 43528) and Swift/BAT (Klingler et al., GCN 43529) with LATIOS on SVOM/C-GFT. Observations started at 2026-01-27T19:07:40 UTC, ~76.55 min after the trigger. The optical counterpart (Saccardiet et al., GCN 43530), consistent with XRT position (Evans et al., GCN 43532; Osborne et al., GCN 43535), was detected in our stacked i-band image. The magnitude is: | Mid_t-T0(hr) | exposure time (s) | band | mag (AB) | mag_err| |--------------|-------------------|------|----------|--------| | 2.24 | 30x90s | i | 20.37 | 0.20 | Our detection is deeper than the upper limit reported by Lipunov et al. (GCN 43532). The photometry was calibrated against nearby stars from UCAC4 catalog and no correction for Galactic dust extinction was applied. We thank the observation assistants Yin-Huai Hao Chun-Lei Guo at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/43537. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41637] GRB 260127A: SVOM/C-GFT optical observations
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43537 SUBJECT: GRB 260127A: SVOM/C-GFT optical observations DATE: 26/01/28 04:44:46 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C. Wu (NAOC), Z. Kang (CHO), L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li, Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of GRB 260127A detected by Fermi/GBM (Fermi GBM team, GCN 43528) and Swift/BAT (Klingler et al., GCN 43529) with LATIOS on SVOM/C-GFT. Observations started at 2026-01-27T19:07:40 UTC, ~76.55 min after the trigger. The optical counterpart (Saccardiet et al., GCN 43530), consistent with XRT position (Evans et al., GCN 43532; Osborne et al., GCN 43535), was detected in our stacked i-band image. The magnitude is: | Mid_t-T0(hr) | exposure time (s) | band | mag (AB) | mag_err| |--------------|-------------------|------|----------|--------| | 2.24 | 30x90s | i | 20.37 | 0.20 | Our detection is deeper than the upper limit reported by Lipunov et al. (GCN 43532). The photometry was calibrated against nearby stars from UCAC4 catalog and no correction for Galactic dust extinction was applied. We thank the observation assistants Yin-Huai Hao Chun-Lei Guo at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/43537. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41636] The EP-WXT trigger 01709253145 is likely a flaring star
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43536 SUBJECT: The EP-WXT trigger 01709253145 is likely a flaring star DATE: 26/01/28 03:45:30 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> S.Y. Fu (HUST), D.F. Hu (PMO, CAS), J. Yang (ZZU), Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709253145 at the time of 2026-01-28T03:17:37 is likely a stellar flare associated with CD-37 6436. The estimated flux of the flare is around 6x10^-11 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 5.6x10^32 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/43536. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41635] GRB 260127A: Enhanced Swift-XRT position
by GCN Circulars 27 Jan '26

27 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43535 SUBJECT: GRB 260127A: Enhanced Swift-XRT position DATE: 26/01/27 21:35:45 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 1612 s of XRT Photon Counting mode data and 2 UVOT images for GRB 260127A, 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 = 231.87939, +6.76215 which is equivalent to: RA (J2000): 15h 27m 31.05s Dec (J2000): +06d 45' 43.7" with an uncertainty of 2.1 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/43535. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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