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[vsnet-grb-info 40846] EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42778 SUBJECT: EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT DATE: 25/11/20 07:22:12 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, Y. Xu, X. H. Han, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observation on the EP-WXT trigger 01709248403 (Li et al. GCNC 42775). The observation began on 2025-11-19T19:32:02 UT (i.e. 37 min post trigger) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously . The counterpart PM J02028+0447 was decreasing in brightness from 12.57 mag at 40 min to 12.67 mag at 78 min in VT_B band, confirming this event as due to a stellar flare, as already suggested by the EP team (Li et al. GCNC 42775). 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/42778. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40845] LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42777 SUBJECT: LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results DATE: 25/11/20 07:21:34 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, L. P. Xin, Z. H. Yao, Y. L. Qiu, C. Wu, H. L. Li, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed the Target of Opportunity observations of 3 candidates of S251112cm reported by LIGO/Virgo/KAGRA (GCN 42650, GCN 42690). SVOM/VT began observing the field at 2025-11-17, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. We observed AT2025adhf (GCN 42675, GCN 42724), AT2025adkl (GCN 42691), and AT2025addc (GCN 42658), which were reported by the Vera C. Rubin Observatory (GCN 42707). We found that AT2025adhf is located within a galaxy, while AT2025adkl is situated at a galaxy's edge. Here we provide the total magnitudes of the supernovae and the galaxies (using the galactic nuclei as the photometric center), since we do not have the templates for this sources. AT2025addc is an isolated source, and we also provide its magnitude. The magnitudes are: Name |Observation Date(UTC) |VT_B(AB_mag) |VT_R(AB_mag) ----------------------|----------------------|-------------|------------- AT2025adhf(+galaxy) |2025-11-17 |17.19+-0.01 |16.41+-0.01 AT2025adkl(+galaxy) |2025-11-18 |20.14+-0.05 |19.50+-0.04 AT2025addc |2025-11-17 |20.45+-0.04 |20.75+-0.07 Our photometry was not corrected for Galactic extinction. Further analysis of these candidates is ongoing. 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/42777. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40844] EP251118a / GRB 251118C: SVOM/VT optical observation
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42776 SUBJECT: EP251118a / GRB 251118C: SVOM/VT optical observation DATE: 25/11/20 06:52:54 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, Y. Xu, X. H. Han, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observation on EP251118a/GRB 251116C (Jiang et al., GCN 42749; Shi et al., GCN 42754; Frederiks et al., GCN 42765; Wang et al., GCN 42766; Delaunay et al., GCN 42770; Woolf et al, GCN 42771). The observation started at 2025-11-19T07:02:19 UT, i.e. 14.33 hour after EP-WXT staring time in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical counterpart reported by Malesani et al. (GCN 42751) and other optical observations (An et al., GCN 42756; Belkin et al, GCN 42758; Yadav et al., GCN 42760; Busmann et al., GCN 42763; Francile et al., GCN 42767; Urquijo-Rodríguez et al., GCN 42773) was clearly detected by VT in both channels. The measurements in AB magnitudes were derived as below: Mid time | Band | Exposure Time | Magnitudes (AB) 15.84 hour VT_B 20*70 sec 21.07+/-0.05 mag 15.84 hour VT_R 20*70 sec 20.64+/-0.05 mag Our photometry was not corrected for Galactic extinction. 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/42776. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40843] The EP-WXT trigger 01709248403 is likely a flaring star
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42775 SUBJECT: The EP-WXT trigger 01709248403 is likely a flaring star DATE: 25/11/20 01:36:45 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li (YNAO, CAS), J. Yang (ZZU), R. Shi (PMO, CAS), F.-F. Song (YNAO, CAS), C. L. Guo and H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709248403 at the time of 2025-11-19T18:55:22, is likely a stellar flare associated with a High Proper Motion Star PM J02028+0447. The estimated flux of the flare is around 2.6e-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 1.3e31 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/42775. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40842] GRB 251118A: NuSTAR detection of bright prompt emission
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42774 SUBJECT: GRB 251118A: NuSTAR detection of bright prompt emission DATE: 25/11/20 00:26:27 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 251118A in both the NuSTAR CsI anti-coincidence shields. This GRB was identified through a blind search using the CsI shield rates. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm triggered at 2025-11-18 20:32:21.000 (with a resolution ~5-seconds). This is consistent with the detections of GRB 251118A by Fermi/GBM (Fermi GBM Team, GCN Circ. 42743) and Fermi/LAT (Gupta et al., GCN Circ. 42752). The NuSTAR CsI shield data are recorded at 1 Hz. We do not detect the first two bursts as seen in the Fermi/GBM lightcurve (GCN Circ. 42743) and detect the third bright burst. The burst appears to be composed of one bright peak lasting for ~9-s. The peak count rate is ~3000-cps over a baseline rate of ~1,000-cps during this time period. We do not see any evidence in the signal above 100 keV in the CdZnTe detectors. The Fermi/LAT localization (GCN Circ. 42752) at RA = 160.08, Dec = -34.58 implies an offset from the NuSTAR boresight of 140-deg and an offset from the geocenter of 99-deg. Lightcurves and analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2025/251118A Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/42774. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40841] EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
by GCN Circulars 19 Nov '25

19 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42773 SUBJECT: EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO DATE: 25/11/19 23:38:46 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> E. Urquijo-Rodríguez, J. Basurto Merino, P.G. Berdayes, A. Caballero-Almagro, A. Cerón, M. Contreras, F. Díaz-Segado, T. Ferrer-Laviña, B. Gandolfi, V. Ghiraldo, J. Hernández Fung, L. Juliá-Maroto, E. Lekaroz-Urriza, M. Manzano García, E. Mejía-Martínez, J. Prieto Polo, M. Pulido-Torres, M. Quintana-Ansaldo, A. Schenone-Zanuzzi, A. Selezneva, T. Tundidor Rodríguez (all ULL), M. Abdul-Masih (IAC and ULL), and I. Pérez-Fournon (IAC and ULL). Following the detection of the fast X-ray transient EP251118a by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Jiang et al., GCN circ. 42749) and by the EP Follow-up X-ray Telescope (FXT) (Shi et al., GCN circ. 42754), we observed the field with one of the three Las Cumbres Observatory (LCO) 1-m telescopes equipped with Sinistro cameras located at the LCO node at Cerro Tololo Inter-American Observatory (CTIO), Chile. The observation, a single exposure of 500 sec in the SDSS r' filter, started on 2025-11-19 at 07:58:16 UT, about 15.26 hours after the EP-WXT trigger. The optical counterpart first detected by NOT ALFOSC (Malesani et al., GCN 42751), at a redshift of z = 1.216 (An et al., GCN circ. 42756) is clearly detected in our image with a magnitude of r' = 20.69 +/- 0.06 (AB), calibrated against PanSTARRS-1 DR2 stars and not corrected for Galactic extinction. Our result is consistent with other optical and near-infrared observations: Belkin et al. (GCN circ. 42758), Yadav et al. (GCN circ. 42760), Busmann et al. (GCN circ. 42763), and Francile et al. (GCN circ. 42767). EPP251118a is likely associated with the long-duration GRB 251118C detected by Konus-Wind (Frederiks et al., GCN circ. 42765), SVOM/GRM (Wang et al., GCN circ. 42766), Swift/BAT (DeLaunay et al., GCN circ. 42770),and Glowbug (Woolf et al., GCN circ. 42771). This work makes use of observations from the Las Cumbres Observatory global telescope network (LCO program IAC2025B-010). These observations are part of a course in Astrophysical Techniques of the Master in Astrophysics of the Astrophysics Department of the University of La Laguna in collaboration with the Instituto de Astrofísica de Canarias (La Laguna, Tenerife, Canary Islands, Spain). This work made use of the Astro-COLIBRI platform (P. Reichherzer et al. 2021, ApJS, 256, 5). View this GCN Circular online at https://gcn.nasa.gov/circulars/42773. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40840] GRB 251116C: NOT optical observations
by GCN Circulars 19 Nov '25

19 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42772 SUBJECT: GRB 251116C: NOT optical observations DATE: 25/11/19 22:04:25 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), L. Fuglsang (NOT) report on behalf of a larger collaboration: We observed the location of the SVOM/ECLAIRs (Pillas et al., GCN 42703; Brunet et al., GCN 42703) and Swift/BAT (DeLaunay et al., GCN 42726) GRB 251116C, using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Our observation covers ~90% of the 3'-radius BAT error circle (including XRT source #1; Evans et al., GCN 42721), and consists of six 300-s images in the r band, taken at a mean epoch of 2025 Nov 17.910 UT (1.245 days after the trigger). Inside or in close proximity of XRT source #1, four objects (3 point-like) are detected in both the NOT and Legacy Survey images. Their photometry does not show significant variation by more than ~0.1 mag. Image subtraction was performed using the Legacy Survey as reference template. No new sources are detected within the covered fraction of the BAT error circle, down to a 3 sigma limiting magnitude of r > 24.4. Our non-detection is consistent with the earlier reports by LCO (Turpin et al., GCN 42705) and SVOM/VT (Li et al., GCN 42712). View this GCN Circular online at https://gcn.nasa.gov/circulars/42772. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40839] GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
by GCN Circulars 19 Nov '25

19 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42771 SUBJECT: GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A DATE: 25/11/19 20:54:02 GMT FROM: richard.s.woolf.civ(a)us.navy.mil R. Woolf, C.C. Cheung, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 251118C, a possible gamma-ray counterpart of EP251118A (GCN 42749), also detected by Konus-Wind (GCN 42765), SVOM/GRM (GCN 42766), and Swift/BAT (GCN 42770). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-11-18 16:44:45.264 with a duration of 8.2 s and a total significance of about 23.8 sigma. The light curve comprises a single primary peak. Note that data from ~T0+8s to ~T0+12s suffered from deadtime in various detectors. The best-fit localization is RA, Decl. (J2000, deg) = 125.0, 14.2 with a radius of 10.5 deg (95% confidence), with a highly uncertain systematic uncertainty. The Glowbug position for GRB 251118C is consistent with that reported for the fast X-ray transient EP251118A (GCN 42749). The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42771. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40838] GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
by GCN Circulars 19 Nov '25

19 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42770 SUBJECT: GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A DATE: 25/11/19 20:06:57 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Samuele Ronchini (GSSI), Aaron Tohuvavohu (Cosmic Frontier), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (Northwestern) report: Swift/BAT did not localize GRB 251118C onboard (T0: 2025-11-18T16:44:49 UTC, Konus-Wind GCN 42765, SVOM/GRM GCN 42766) Due to the lack of prompt trigger, the Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1) was unable to save time-tagged event data around this burst. The GRB is clearly detected in the BAT rates data with a S/N ~ 13. The emission is seen starting at ~T0 - 12 s and lasts ~28 s. There are minimal counts seen at energies less than 50 keV, which is consistent with a GRB that is outside the coded field of view of BAT, especially with the soft spectrum observed by Konus-Wind and SVOM/GRM. There is also a 10 s time tagged event data file during the burst due to an onboard rate trigger that failed to recover an image position. We used the 10 s of event data to create an image (15 - 350 keV) and find no new sources in it. Due to the lack of sources in the image and the observed energy spectrum, this GRB is likely to be outside the 10% coded field of view of Swift/BAT. Also, we can confirm that the GRB is not Earth Occulted for Swift. This rules out a circular region of the sky centered at ra, dec = 21.69, 12.65 deg (J2000) with a radius of 69.5 deg. This rules out only ~half of the sky, and does not rule out the position of EP 251118A (GCN 42749). There are no NITRATES results due to the lack of GUANO data, but the rates light-curve and position of the Earth and BAT coded FoV at the time can be seen on the results summary page https://guano.swift.psu.edu/trigger_report?id=785177125 View this GCN Circular online at https://gcn.nasa.gov/circulars/42770. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40837] GRB 251018A: FRAM-Auger optical detection
by GCN Circulars 19 Nov '25

19 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42769 SUBJECT: GRB 251018A: FRAM-Auger optical detection DATE: 25/11/19 20:02:40 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek(a)asu.cas.cz> Anurag Talele (University of Potsdam), Martin Jelinek, Alzbeta Malenakova, Jan Strobl (ASU CAS Ondrejov, CZ), Filip Novotny (ASU Ondrejov + Masaryk University), Martin Masek, Petr Janecek, Sergey Karpov, Jakub Jurysek, Jan Ebr, Ronan Cunniffe, Petr Travnicek and Michael Prouza (Institute of Physics, Prague, CZ) report: The 30 cm robotic telescope at the FRAM-Auger in Malargue (Argentina) reacted robotically to the Swift/BAT alert of GRB251018A (trigger 1405083, Gupta et. al. GCN42343) issued at 03:12:02 UT. FRAM obtained its first unfiltered exposure 42 seconds after the trigger, at 03:12:44 UT, followed by a sequence of 20s and 60s exposures. An optical transient is detected at the UVOT position. It appears at R(Vega) roughly 15.5 mag at T0 + 78s and fades to roughly 18.0 mag by the end of our 28 minutes observing run consistent with detections by Lipunov et. al. GCN42346, Hu et. al. GCN42363 and Kuin et. al. GCN42353. View this GCN Circular online at https://gcn.nasa.gov/circulars/42769. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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