October 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 40604] GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
by GCN Circulars 29 Oct '25

29 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42519 SUBJECT: GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova DATE: 25/10/29 20:04:03 GMT FROM: jcarney(a)unc.edu Jonathan Carney (UNC), Xander J. Hall (CMU), Igor Andreoni (UNC), Brendan O’Connor (CMU), Malte Busmann (LMU), Daniel Gruen (LMU), and Antonella Palmese (CMU) report: We observed the source SN 2025absf reported by Belkin et al. (GCN 42470), a possible counterpart to short GRB 251026B (GCN 42455), with the Goodman High Throughput Spectrograph (GHTS; Clemens 2004) on the Southern Astrophysical Telescope (SOAR). We used a grating of 400 lines/mm and a 1.0'' wide slit mask in the M1 spectroscopic setup (hereafter 400M1) with 2x2 binning using the GHTS Red Camera. The 400M1 spectra cover a wavelength range of 3800 -- 7040 Å. The spectra were reduced using Pypeit (Prochaska 2020), using arcs taken immediately after target observation and calibration images from the same night. Flux calibration was performed using observations of HR7596 taken on the same night as the observations with an identical 400M1 setup and 2x2 binning. Using SNID (Blondin et al. 2011) and NGSF (AstroNote 2022-191), we find good template matches to a Ia-norm SN at z ~ 0.044. Thus, we classify SN 2025absf as a type Ia supernova. We therefore conclude that SN 2025absf is not the optical counterpart to GRB 251026B. We thank the CTIO and NOIRLab staff for supporting these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42519. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40603] GRB 251022A: Swift-XRT confirmation of fading
by GCN Circulars 29 Oct '25

29 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42518 SUBJECT: GRB 251022A: Swift-XRT confirmation of fading DATE: 25/10/29 19:49:57 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), M. Capalbi (INAF-OAR), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & 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 Fermi/LAT-detected burst GRB 251022A. The observations now extend from T0+38.6 ks to T0+575.9 ks and have a total exposure time of 6.6 ks. . The previously-reported "Source 4" (Burrows et al., GCN Circ. 42417), coincident with GOTO25iym, is now found to be fading with >3-sigma significance, and is therefore likely the GRB afterglow. The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/00021864. The results of the full analysis of the tiled XRT observations are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00139. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42518. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40602] GRB 251026B: LBT near-infrared observations
by GCN Circulars 29 Oct '25

29 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42517 SUBJECT: GRB 251026B: LBT near-infrared observations DATE: 25/10/29 17:44:10 GMT FROM: Yu-Han Yang at University of Rome Tor Vergata <yyang(a)roma2.infn.it> Yu-Han Yang, Eleonora Troja, Massine El Kabir, Muskan Yadav (U Rome) report on behalf of the ERC BHianca team: Following the detection of GRB 251026B by Fermi/GBM (Dafčíková et al., GCN 42455), we observed the candidate optical counterpart GOTO25jgl/AT2025absf (Belkin et al., GCN 42470) in the J filter with the LUCI near-infrared imager mounted on the Large Binocular Telescope (LBT). Observations started at 2025-10-29T11:28:17 (~ 3.2 d after the GBM trigger) with an average airmass of 1.5. We detect the source previously reported as a candidate from GOTO (Belkin et al., GCN 42470) with a preliminary magnitude of J ~ 19.2 AB mag, calibrated using nearby stars from the 2MASS catalog (Skrutskie et al. 2006), uncorrected for Galactic extinction. Our measurement is consistent with the near-infrared upper limit derived by PRIME (Kabir et al. GCN 42501). Compared to the predicted optical magnitude L~19.3 at the same epoch using the magnitudes and decay trend reported by GOTO (Belkin et al., GCN 42470), we find no evidence for a red color excess. Based on the lack of X-ray emission (Osborne et al. GCN 42491) and blue color, the properties of GOTO25jgl do not appear consistent with standard afterglow or kilonova emission, therefore its association with GRB 251026B cannot be confirmed. We acknowledge excellent support from the LBTO and LBT-INAF staff, particularly Ester Marini. View this GCN Circular online at https://gcn.nasa.gov/circulars/42517. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40601] GRB 250926B: VZLUSAT-2 detection
by GCN Circulars 29 Oct '25

29 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42516 SUBJECT: GRB 250926B: VZLUSAT-2 detection DATE: 25/10/29 16:40:33 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU) -- the VZLUSAT-2/GRB payload collaboration. The long-duration GRB 250926B (Fermi/GBM detection: GCN 42012) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/). The data acquisition was performed by the GRB detector unit no. 0. The detection was confirmed at the peak time 2025-09-26 19:50:31 UTC. The T90 duration is 26 s and the significance during T90 reaches 5.4 sigma. The light curve obtained by VZLUSAT-2 is available here: https://vzlusat2.konkoly.hu/static/share/GRB250926B_GCN_VZLUSAT2.pdf All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/ The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral. View this GCN Circular online at https://gcn.nasa.gov/circulars/42516. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40600] GRB 250926A: VZLUSAT-2 detection
by GCN Circulars 29 Oct '25

29 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42515 SUBJECT: GRB 250926A: VZLUSAT-2 detection DATE: 25/10/29 16:39:53 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU) -- the VZLUSAT-2/GRB payload collaboration. The long-duration GRB 250926A (Fermi/GBM detection: GCN 41993; AstroSat/CZTI detection: GCN 42008; INSIGHT-HXMT/HE detection: GCN 42013; CALET/CGBM detection: GCN 42027; Wind/Konus detection trigger at 2025-09-26 00:21:25.489 UTC) was detected by the GRB detectors on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/). The data acquisition was performed by the GRB detector units no. 0 and no. 1. The detection was confirmed at the peak time 2025-09-26 00:21:23 UTC. The T90 duration is 1 s (2 s) and the significance during T90 reaches 5 sigma (17 sigma) for detector unit no. 0 (no. 1). The light curve obtained by VZLUSAT-2 is available here: https://vzlusat2.konkoly.hu/static/share/GRB250926A_GCN_VZLUSAT2.pdf All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/ The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral. View this GCN Circular online at https://gcn.nasa.gov/circulars/42515. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40599] GRB 250925A: VZLUSAT-2 detection
by GCN Circulars 29 Oct '25

29 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42514 SUBJECT: GRB 250925A: VZLUSAT-2 detection DATE: 25/10/29 16:38:52 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU) -- the VZLUSAT-2/GRB payload collaboration. The long-duration GRB 250925A (Swift/BAT detection: GCN 41985) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/). The data acquisition was performed by the GRB detector unit no. 0. The detection was confirmed at the peak time 2025-09-25 17:04:21 UTC. The T90 duration is 22 s and the significance during T90 reaches 6.6 sigma. The light curve obtained by VZLUSAT-2 is available here: https://vzlusat2.konkoly.hu/static/share/GRB250925A_GCN_VZLUSAT2.pdf All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/ The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral. View this GCN Circular online at https://gcn.nasa.gov/circulars/42514. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40598] GRB 251026B: Fermi GBM Observation
by GCN Circulars 29 Oct '25

29 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42513 SUBJECT: GRB 251026B: Fermi GBM Observation DATE: 25/10/29 14:40:22 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova (MUNI) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 07:18:53.33 UT on 26 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251026B (trigger 783155938/251026305). The angle from the Fermi LAT boresight is 19 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 6 s (50-300 keV). The time-averaged spectrum from T0-1.3 to T0+3.7 s is best fit by a simple power law function with index -1.38 +/- 0.04. The event fluence (10-1000 keV) in this time interval is (7.2 +/- 0.7)E-07 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.32 s in the 10-1000 keV band is 1.6 +/- 0.2 ph/s/cm^2. 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/42513. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40597] GRB 251026A/EP251026a: SVOM/VT optical counterpart
by GCN Circulars 29 Oct '25

29 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42512 SUBJECT: GRB 251026A/EP251026a: SVOM/VT optical counterpart DATE: 25/10/29 14:28:29 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, C. Wu, L. P. Xin, Y. L. Qiu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Z. H. Yao, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu., J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), J.X Cao (GXU), X. Tian (GXU) report on behalf of the SVOM/VT team. SVOM/VT performed an automatic slew on the long burst triggered by SVOM/ECLAIRs (Cao et al., GCN 42454) and EP-WXT (Li et al.., GCN 42482). SVOM/VT began observing the field automatically on 2025-10-26T08:34:26, i.e., 424 sec with the slew of the platform triggered on-board, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X band downlinked data, an uncatalogued and fading optical counterpart within EP-FXT's error box (Li et al., GCN 42511) was detected in both channels, compared to the PanSTARRS catalogue. The position is at R.A., Dec. = 72.653080, 51.763733 degrees, equivalent to: R.A. (J2000) = 04:50:36.74 Dec. (J2000) = +51:45:49.44 with an uncertainty of 0.5 arcsec. This location is 3.6 arcminutes from the ECLAIRs onboard position and 2.1 arcminutes from the MXTs position (Cao et al., GCN 42454). The afterglow was fading with a temporal slope of -0.7 from VT_R~19.51+/-0.05 mag, VT_B~21.35+/-0.18 mag at 445 sec, followed by a bump with the peak of VT_R~20.8+/-0.1 mag at the mid time of 3.3 hours post trigger. With the check of VT VHF data, the optical counterpart was also detected in source list and 1 bit images of both channels in Sequence 1. Our photometry was estimated in AB magnitude and not corrected for Galactic extinction. Given the heavy extinction of the Galactic plane (Av = 3.7), the burst was intrinsically optically bright. 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/42512. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40596] GRB 251026A/EP251026a: EP-FXT follow-up observation
by GCN Circulars 29 Oct '25

29 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42511 SUBJECT: GRB 251026A/EP251026a: EP-FXT follow-up observation DATE: 25/10/29 13:22:19 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> A. Li (BNU), J. H. Wu (GZHU), H. Q. Cheng and H. Sun (NAOC) on behalf of the Einstein Probe (EP) team: EP-FXT performed two follow-up observations of GRB 251026A/EP251026a (GCN 42454) at 2025-10-27T09:41:08 and 2025-10-28T01:39:45 (UTC), respectively, about 25 and 41 hours after the ECLAIRs' trigger, with an exposure time of 2.7 and 6.0 ks. No source was detected in the first observation. The second observation detected a weak uncatalogued source within the WXT error circle at R.A. = 72.6573, DEC = 51.7653 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). Based on the spectral fitting result, we got a powerlaw spectrum with the absorption fixed at the Galactic value of 3.77x10^21 cm^-2 and the photon index of 2.5, the flux in 0.5-10 keV is derived to be approximately 5.4x10^-14 erg/s/cm2 from the FXT count rate. 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/42511. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40595] The EP-WXT trigger 01709247588 is likely a flaring star
by GCN Circulars 29 Oct '25

29 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42510 SUBJECT: The EP-WXT trigger 01709247588 is likely a flaring star DATE: 25/10/29 12:02:08 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Author list: J. P. Feng, B. Zhang (USTC), Y. Wang, Y. F. Liang (PMO, CAS), W. D. Zhang (NAO, CAS) on behalf of the Einstein Probe (EP) team: Content: The EP-WXT trigger 01709247588 at the time of 2025-10-29T06:43:17 UTC, is likely a stellar flare associated with Emission-line Star--PM J04472+2038. The estimated flux of the flare is around 1.6e-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 1e31 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/42510. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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