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

[vsnet-grb-info 40994] EP251130a: SAO RAS optical observations
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42919 SUBJECT: EP251130a: SAO RAS optical observations DATE: 25/12/01 14:03:05 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin and O. I. Spiridonova (SAO RAS) report on behalf of GRB follow-up team. We observed the field of the X-ray transient EP251130a (Wu et al., GCN 42903; Zhang et al., GCN 42915), also detected by Swift-XRT (Evans et al., GCN 42908) with the Zeiss-1000 1m telescope of the SAO RAS on December 1, 01:29:21--03:08:47 UT (t_mid - T0 = 0.63281 days). We obtained 11 * 300 images in Rc band under mediocre weather conditions. The optical counterpart (Dornic et al., GCN 42904; He et al. GCN 42914; Gupta et al. GCN 42916; Zheng et al. GCN 42917; van Dalen et al., GCN 42918) is clearly detected in our stacked image with the brightness of R = 20.11 +/- 0.07 (R_lim = 21.8). This preliminary photometry is based on nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. USNO-B1 star RA DEC R2 1173-00161316 101.000000 +27.372589 16.26 1173-00161485 101.071981 +27.375787 16.76 1173-00161417 101.045348 +27.394953 16.04 In comparison with the OT brightness from 1.3m DFOT data (Gupta et al., GCN 42916) we noted a brightening between two epochs (also reported by Zheng et al. GCN 42917 and van Dalen et al., GCN 42918). View this GCN Circular online at https://gcn.nasa.gov/circulars/42919. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40993] EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42918 SUBJECT: EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening DATE: 25/12/01 09:30:53 GMT FROM: Agnes van Hoof at Radboud University <agnes.vanhoof(a)ru.nl> J. N. D. van Dalen (Radboud), A. P. C. van Hoof (Radboud), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), J. Quirola-Vasquez (Radboud), P. G. Jonker (Radboud), D. Mata-Sanchez (IAC and ULL), N.C. Rodríguez (GTC), A. Cabrera-Lavers (GTC) report on behalf of a larger collaboration. We observed the counterpart (Dornic et al., GCN 42904; Evans et al., GCN 42908; He et al., GCN 42914; Gupta et al., GCN 42916; Zheng et al., GCN 42917) of EP251130a (Wu et al., GCN 42903; Zhang et al., GCN 42915) with the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ instrument. Three 1200 s exposures were obtained using the R1000R grating and a 1 arcsec slit. Observations began on 2025 Dec 1 at 01:28 UT, approximately 0.6 days after the EP trigger time. From the 60 s acquisition image taken in the i band, we measure a magnitude of i = 19.54+/-0.03 AB (calibrated against nearby Pan-STARRS objects). We find a rebrightening of the optical counterpart by ~1 mag in ~10 hr as compared to He et al. (GCN 42914). In the spectrum, a broad trough centered around 6120 AA is detected, which we interpret as due to a DLA. Several metal absorption lines are also detected on top of the bright continuum, which match Si II, Si II*, O I, C II, Si IV, C IV, Fe II, Al II, all at a common redshift of z = 4.035. View this GCN Circular online at https://gcn.nasa.gov/circulars/42918. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40992] EP251130a: KAIT optical observations
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42917 SUBJECT: EP251130a: KAIT optical observations DATE: 25/12/01 09:16:17 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, automatically responded to EP251130a (Wu et al., GCN 42903) starting at 11:21:40 UT, 831 seconds after the burst. A set of 10x20s, 10x40s, 60x60s clear (roughly R) filter images were obtained. We clearly detected the optical afterglow (Dornic et al., GCN 42904, He et al., GCN 42914; Gupta et al., GCN 42916) in our coadd image. We measure its brightness decreased from 19.6 +/- 0.1 mag (Vega; mid time 16.45 min) to 20.2 +/- 0.2 mag (mid time of 91.03 min) with a decay index of 0.46. Additional 30x60s clear filter images were obtained the following night at a mid time of 0.89 days after the burst. The OT is still detected at 19.7 +/- 0.1 mag, indicating the OT has brightened. More follow-up observations are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/42917. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40991] EP251130A: Optical observation from 1.3m DFOT
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42916 SUBJECT: EP251130A: Optical observation from 1.3m DFOT DATE: 25/12/01 08:45:09 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Pankaj Pawar, Debalina Kar, Dhruv Jain, and Kuntal Misra (ARIES) report: We observed the field of EP251130A detected by Einstein Probe (Wu et al. 2025, GCN 42903) 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 22025-11-30 at 19:21:24 UT, i.e., ~8.22 hours after the EP trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We detect the optical counterpart in our stacked image within the error box of Swift-XRT (Evans et al. 2025, GCN 42908). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude ====================================================================== 2025-11-30 19:21:24 ~8.22 R 300*12 22.20+/- 0.09 Our detection is consistent with Dornic et al. 2025 (GCN 42904); Lipunov et al. 2025 (GCN 42906); He et al. 2025 (GCN 42914). 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 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/42916. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40990] EP251130A: Optical observation from 1.3m DFOT
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42916 SUBJECT: EP251130A: Optical observation from 1.3m DFOT DATE: 25/12/01 08:45:09 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Pankaj Pawar, Debalina Kar, Dhruv Jain, and Kuntal Misra (ARIES) report: We observed the field of EP251130A detected by Einstein Probe (Wu et al. 2025, GCN 42903) 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 22025-11-30 at 19:21:24 UT, i.e., ~8.22 hours after the EP trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We detect the optical counterpart in our stacked image within the error box of Swift-XRT (Evans et al. 2025, GCN 42908). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude ====================================================================== 2025-11-30 19:21:24 ~8.22 R 300*12 22.20+/- 0.09 Our detection is consistent with Dornic et al. 2025 (GCN 42904); Lipunov et al. 2025 (GCN 42906); He et al. 2025 (GCN 42914). 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 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/42916. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40989] EP251130a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42915 SUBJECT: EP251130a: refined analysis of the EP-WXT and EP-FXT observations DATE: 25/12/01 08:40:25 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> W. J. Zhang (NAO, CAS), H. C. Ding, T. Wu (AHNU), Y. H. Jiang, Y. Wu (NJU), Y. Wang (PMO), Y. Liu (NAO, CAS), on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP251130a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Wu et al., GCN 42903), and was followed by several telescopes (Dornic et al., GCN 42904, Lipunov et al., GCN 42906 and Evans et al., GCN 42908). The refined analysis of the WXT data shows that the event started at T0=2025-11-30T11:04:00 (UTC) and lasted for ~230 s, before the observation was interrupted by 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 1.40 x 10^21 cm^-2 and a photon index of 1.54 (-0.63/+0.70). The derived average unabsorbed 0.5-4 keV flux is 2.46 (-0.77/+1.06) x 10^(-10) erg/s/cm^2. A follow-up observation of EP251130a with the Follow-up X-ray Telescope (FXT) was performed automatically at 2025-11-30T11:11:12 (UTC), about 7 minutes after T0, with an exposure time of 4,200 s. The on-ground analysis shows that an uncatalogued source was detected at R.A. = 101.0210 deg, Dec. = 27.3840 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). This position is ~1.6 arcsec from the reported optical counterpart (Dornic et al., GCN 42904). The average FXT 0.5-10 keV spectrum of the observation can be fitted with an absorbed power law, with a hydrogen column density of 1.39 (-0.81/+0.86) x 10^21 cm^-2 and a photon index of 2.12 (-0.32/+0.34). The derived average unabsorbed 0.5-10 keV flux is 3.32 (-0.31/+0.32) x 10^(-12) erg/s/cm^2. 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/42915. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40988] EP251130a: JinShan optical observations
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42914 SUBJECT: EP251130a: JinShan optical observations DATE: 25/12/01 06:43:09 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He, J. An, S.Q. Jiang, X. Liu, Z.P. Zhu, D. Xu (NAOC), S.Y. Fu, A.D. Zhu, L. Lei, H.Z. Wu (HUST), J.Z. Liu (XAO) report on behalf of a large collaboration: We observed the field of EP251130a (Wu et al., GCN 42903) using the 100B telescope of the JinShan project, located at Altay, Xinjiang, China. Obervations started at 2025-11-30 14:13:38 UT, i. e. 3.1 hrs post-burst, and a series of frames in g, r and i bands were obtained. The previously reported optical counterpart candidate (Dornic et al., GCN 42904) was detected in our stacked i-band frame with a magnitude i = 20.60 +/- 0.18 at a mid-time 4.67 hrs post-burst. The magnitude was callibrated with nearby PanSTARRS1 dr2 catalog and without the Galactic extinction correction. We acknowledge the excellent support from T.Q. Chen and J.F. Zhang for enabling these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42914. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40987] GRB 251201A: MAXI/GSC detection
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42913 SUBJECT: GRB 251201A: MAXI/GSC detection DATE: 25/12/01 05:57:21 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> D. Iijima, Y. Kawakubo (AGU), M. Nakajima (Nihon U.), H. Negoro, K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, C. Kang, T. Nakamoto, M. Uenishi, T. Usuki, S. Yatsuzuka (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U) report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 04:36:59 UT on December 1, 2025. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (309.032 deg, 30.413 deg) = (20 36 07, +30 24 46) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.20 deg and 0.16 deg, respectively. The roll angle of long axis from the north direction is 14.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 327 +- 36 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (R.A., Dec) = (307.993, 30.840) deg = (20 31 58, +30 50 23) (J2000) (R.A., Dec) = (307.875, 30.457) deg = (20 31 29, +30 27 25) (J2000) (R.A., Dec) = (310.227, 29.897) deg = (20 40 54, +29 53 49) (J2000) (R.A., Dec) = (310.354, 30.278) deg = (20 41 24, +30 16 40) (J2000) There was no significant excess flux in the previous transit at 03:04 UT. View this GCN Circular online at https://gcn.nasa.gov/circulars/42913. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40986] GRB 251129A / EP251129a: SVOM/VT optical fading
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42887 SUBJECT: GRB 251129A / EP251129a: SVOM/VT optical fading DATE: 25/11/29 05:41:54 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li , L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), W. J. Tan (IHEP), D. F. Kong (GXU) report on behalf of the SVOM/VT team. SVOM/VT performed an automatic slew to GRB 251129A/EP251129a triggered by SVOM/ECL (sb25112901, Tan et al., GCN 42879). The burst was also triggered by EP (Wu et al., GCN 42884). SVOM/VT began the observation at 2025-11-29T02:43:03 UTC, i.e., 658 seconds post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With the downloaded early X band data, the optical counterpart (Angulo et al. GCN 42880; Watson, GCN 42883; Wu et al., GCN 42882; Masi et al. GCN 42885) was clearly detected in both channels. The measurements are given below: Mid_time Band Exposure Time Magnitude (AB) 12.43 min VT_B 50 sec 18.16+/-0.03 mag 12.43 min VT_R 50 sec 17.89+/-0.03 mag 44.96 min VT_B 50 sec 19.11+/-0.04 mag 44.96 min VT_R 50 sec 18.80+/-0.03 mag It was fading with a slope of about 0.7 with a single power law. 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/42887. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40985] EP251130a: COLIBRÍ optical counterpart candidate
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42904 SUBJECT: EP251130a: COLIBRÍ optical counterpart candidate DATE: 25/11/30 15:18:49 GMT FROM: Damien Dornic <ddornic(a)km3net.de> Damien Dornic (CPPM), Margarita Pereyra (UNAM), Stéphane Basa (UAR Pytheas), Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), William H. Lee (UNAM), Kin Ramandeep Gill (UNAM), Noémie Globus (UNAM), Ocelotl López (UNAM), Diego López-Cámara (UNAM), Nikos Mandarakas (LAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM): We imaged the field of the EP251130a (Wu et al., GCN 42903) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-11-30T12:09:17 to 12:28 UTC (from 1.02 to 1.34 hours after the trigger) and obtained 16 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded and analysed with the COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we detect an uncatalogued source at the coordinates: RA = 101.0205 deg, Dec = 27.3840 deg with an uncertainty of 0.5 arcsec, compatible with the EP/FXT position (Wu et al., GCN 42903), at preliminary magnitudes of: r = 20.69 +/- 0.03 z = 19.45 +/- 0.03 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/42904. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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