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

[vsnet-grb-info 39386] GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41328 SUBJECT: GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations DATE: 25/08/12 14:45:26 GMT FROM: Ny Avo Rakotondrainibe at LAM <nyavo.rakotobe(a)gmail.com> Ny Avo Rakotondrainibe (LAM), Diego López-Cámara (UNAM), Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Fredd Sánchez Álvarez (UNAM), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (OCA), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and L. P. Xin (NAOC): We imaged the field of the SVOM GRB 250812A (Xin et al., GCN Circ. 41322) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-08-12 11:47 to 11:53 UTC (from 8.86 to 8.96 hours after the trigger) and obtained 300 seconds of exposure in the i-band filter. Due to the position of the field, the observations were conducted during astronomical twilight and at an airmass of about 3.4. The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the SkyMapper DR4 catalog, is in the AB system, and is not corrected for Galactic extinction. We detected the optical counterpart reported by He et al. (GCN Circ 41324) and Xin et al. (GCN Circ 41326) at a preliminary magnitude of: i = 18.89 +/- 0.05 Further observations are planned. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/41328. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39385] EP250812a: Einstein Probe detection of an X-ray transient
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41327 SUBJECT: EP250812a: Einstein Probe detection of an X-ray transient DATE: 25/08/12 13:59:12 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> M.-H. Zhang (NAO,CAS), H. Zhou (PMO,CAS) and W.-D. Zhang (NAO,CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250812a. The transient triggered EP-WXT (ID: 01709198788) at 2025-08-12T13:09:44 (UTC). The WXT position of the source is R.A. = 30.979 deg, DEC = -9.305 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 30.9964 deg, DEC = -9.3206 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. 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/41327. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39384] GRB 250812A: SVOM/VT optical afterglow confirmation
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41326 SUBJECT: GRB 250812A: SVOM/VT optical afterglow confirmation DATE: 25/08/12 13:41:54 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L. P. Xin, H. L. Li, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), Z. M. Wang (BNU) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of GRB 250812A detected by SVOM/Eclairs (Xin et al., GCN 41322). The observation began at 2025-08-12T09:19:03 UTC, 6.55 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical counterpart (He et al., GCN 41324) within the errorbox of Swift/XRT (Sbarrato et al., GCN 41325) was detected in both VT_R and VT_B. The magnitudes are: Mid-time (h) | exposure time (s) | band | mag (AB) | mag err ---------------|-------------------|------|----------|-------------------------------- 8.29 | 22*70 | VT_B | 19.36 | 0.02 8.29 | 22*70 | VT_R | 18.92 | 0.02 We also noticed that this source was brightening during our observations for about 0.4 magnitudes from 6.67 hours to 8.33 hours after the burst. Our photometry was not corrected for Galactic extinction. More VT follow-ups will be scheduled. 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/41326. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39383] GRB 250812A: Swift-XRT afterglow detection
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41325 SUBJECT: GRB 250812A: Swift-XRT afterglow detection DATE: 25/08/12 13:34:45 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> T. Sbarrato (INAF-OAB), D.N. Burrows (PSU), M.A. Williams (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of GRB 250812A. We searched for X-ray sources in 977 s of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 977 s, obtained between T0+6.7 ks and T0+12.4 ks. An uncatalogued X-ray source is detected and is above the RASS 3-sigma upper limit at this position, and is therefore likely the GRB afterglow. Using 1351 s of PC mode data and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 32.80701, -43.16360 which is equivalent to: RA (J2000): 02h 11m 13.68s Dec(J2000): -43d 09' 49.0" with an uncertainty of 3.0 arcsec (radius, 90% confidence). The light curve is consistent with a constant source of mean count rate 1.5e-01 ct/sec. A power-law fit gives an index of 0.16 (+0.64, -0.16). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.97 (+0.40, -0.23). The best-fitting absorption column is consistent with the Galactic value of 1.5 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.1 x 10^-11 (3.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.5 (+/-6.9) x 10^20 cm^-2 Galactic foreground: 1.5 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.97 (+0.40, -0.23) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00019994. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/SVOM_FIELD00028. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41325. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39382] GRB 250812A: TRT likely optical counterpart detection
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41324 SUBJECT: GRB 250812A: TRT likely optical counterpart detection DATE: 25/08/12 09:35:34 GMT FROM: J. An <jiean0813(a)foxmail.com> L.B. He (NAOC), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), S.Y. Fu (HUST), J. An, X. Liu, Z.P. Zhu, S.Q. Jiang, D. Xu (NAOC) report on behalf of a large collaboration: We observed the field of GRB 250812A (Xin et al., GCN 41322), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Cerro Tololo Inter-American Observatory, Chile. Observations started at 04:32:00 UTC on 2025-08-12, i.e., ~1.8 hr after the SVOM/ECLAIRs trigger and a series of frames in the r band were obtained. In our stacked image, we detect an uncatalogued source within the SVOM/ECLAIRs error circle at coordinates: R.A.(J2000) = 02:11:13.72 = 32.80715 Dec.(J2000) = -43:09:49.21 = -43.16367 with an uncertainty of ~0.5 arcsec. We measure a preliminary magnitude of r ~ 18.8, calibrated with Legacy catalog and not corrected for Galactic extinction. We suggest this is likely the optical counterpart of GRB 250812A. View this GCN Circular online at https://gcn.nasa.gov/circulars/41324. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39381] IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41323 SUBJECT: IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/08/12 03:56:05 GMT FROM: Yuhua Yao <yyao255(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-Cascade 250809A (https://gcn.gsfc.nasa.gov/notices_amon_icecube_cascade/141229_33703437.amon) in a time range of 1000 seconds centered on the alert event time (2025-08-09 13:49:08.550 UTC to 2025-08-09 14:05:48.550 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-Cascade 250809A.We report a p-value of 1.00 in this time window. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-Cascade 250809A is 1.4e-01 GeV cm^-2 in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 2e+02 GeV and 9e+04 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-08-08 13:57:28.550 UTC to 2025-08-10 13:57:28.550 UTC). In this case, we report a p-value of 0.14, consistent with no significant excess of track events. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-Cascade 250809A ranges from 1.6e-01 to 1.7e-01 GeV cm^-2 in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/41323. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39380] GRB 250812A: SVOM detection of a faint long burst
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41322 SUBJECT: GRB 250812A: SVOM detection of a faint long burst DATE: 25/08/12 03:53:19 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> L. P. Xin(NAOC), Z.M. Wang(BNU), W.J. Xie(NAOC), H. Goto(Kanazawa univ.) report on behalf of the SVOM mission team: At 2025-08-12T02:46:03 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 250812A (SVOM burst-id sb25081201). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced a sequence of 2 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 7.38 in the [8-120] keV energy band over a time window of 40.96 seconds starting at 2025-08-12T02:45:22. The localization of the best alert is R.A., Dec. 32.6058, -43.0702 degrees: R.A. (J2000) = 2h10m25.40s Dec. (J2000) = -43d04m12.86s with a 90% confidence level (C.L.) radius of 10.62 arcmin (including systematic error of 2 arcmin added in quadrature). Due to the detection significance being below the slew threshold, no immediate slew was performed on this burst. No X-ray observation could be performed by SVOM/MXT for the time being. No optical observation could be performed by SVOM/VT for the time being. Follow-ups with MXT and VT would be scheduled. The Space-based multi-band astronomical 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. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is xlp AT nao.cas.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/41322. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39379] GRB 250809A: Swift-BAT refined analysis
by GCN Circulars 11 Aug '25

11 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41321 SUBJECT: GRB 250809A: Swift-BAT refined analysis DATE: 25/08/11 18:09:12 GMT FROM: D. R. Sadaula at NASA GSFC <dev.r.sadaula(a)nasa.gov> D. Sadaula (GSFC/UMBC), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250809A (trigger #1340954) (Parsotan, et al., GCN Circ. 41303). The BAT ground-calculated position is RA, Dec = 233.034, -53.314 deg which is RA(J2000) = 15h 32m 08.2s Dec(J2000) = -53d 18' 50.6" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 96%. The BAT light curve showed a complex structure with a duration of about 32 sec. T90 (15-350 keV) is 17.79 +- 2.77 sec (estimated error including systematics). The time-averaged spectrum from T+1.01 to T+20.94 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.83 +- 0.20. The fluence in the 15-150 keV band is 3.9 +- 0.5 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+11.58 sec in the 15-150 keV band is 0.6 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1340954 View this GCN Circular online at https://gcn.nasa.gov/circulars/41321. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39378] Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
by GCN Circulars 11 Aug '25

11 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41320 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB DATE: 25/08/11 17:10:25 GMT FROM: Jacob Smith at Fermi-GBM Team <jrs0118(a)uah.edu> Jacob Smith (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: The Fermi Gamma-ray Burst Monitor (GBM) trigger 776620220/250811660 at 15:50:15.05 UT on 11 August 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to local particles. View this GCN Circular online at https://gcn.nasa.gov/circulars/41320. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39377] GRB 250309B: 1.3m DFOT Optical observations
by GCN Circulars 11 Aug '25

11 Aug '25

TITLE: GCN CIRCULAR NUMBER: 39679 SUBJECT: GRB 250309B: 1.3m DFOT Optical observations DATE: 25/03/12 06:18:47 GMT FROM: Amit Kumar Ror at ARIES <mitturor77894(a)gmail.com> Amit K. Ror, Anshika Gupta, Pranshu, Shashi B. Pandey, Kuntal Mishra (ARIES) report: We observed the field of GRB 230509B detected by the Swift and Fermi (Evans et al. 2025, GCN 39633; Fermi GBM team, GCN 39635, 39642) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-03-10 at 20:25:19 UT, i.e., ~ 1.53 days after the Ferm-GBM trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We detected an optical afterglow reported by Stein et al. 2025 (GCN 39639) in our stacked image. We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude ========================================================= 2025-03-10 20:25:19 ~1.53 R 300s*24 20.36 +/- 0.10 Our detection is consistent with Stein et al. 2025 (GCN 39639); Lipunov et al. 2025 (GCN 39641); Pérez-Fournon et al. 2025 (GCN 39643); Stein et al. 2025 (GCN 39644); Moskvitin et al. 2025 (GCN 39645); Perley et al. 2025 (GCN 39646); Malesani et al. 2025 (GCN 39647); Ducoin et al. 2025 (GCN 39650); Shin et al. 2025 (GCN 39654); Moskvitin et al. 2025 (GCN 39658); Wang et al. 2025 (GCN 39661) and Guiffreda et al. 2025 (GCN 39670). The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalogue. This circular may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39679. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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