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

[vsnet-grb-info 37948] GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39930 SUBJECT: GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations DATE: 25/03/29 19:02:34 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Jean-Grégoire Ducoin (CPPM), Noémie Globus (UNAM), Camila Angulo (UNAM), Sarah Antier (OCA), Ramandeep Gill (UNAM), Stéphane Basa (LAM), William H. Lee (UNAM), Dalya Akl (AUS), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and Hui Yang (IRAP) report: We observed the field of SVOM/ECLAIRs GRB 250327B (Bouchet et al. GCN Circ. 39888) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We obtained 50 minutes of exposure in the i filter from 2025-03-29 03:49 and 11:32 (44.3 and 52.0 hours after the trigger). Our observations were not continuous, but rather were at the start and end of this interval with a long interruption for observations of other sources. We observed through thick clouds. The data were coadded with the COLIBRI pipeline and analysed in STDWeb/STDPipe (Karpov 2021). The photometric calibration was performed using nearby stars from the Pan-STARRS DR1 catalog and the magnitude is not corrected for Galactic extinction. At the position of the previously reported optical transient (Moskvitin et al., GCN Circ. 39889; Xin et al., GCN Circ. 39890; O’Neill et al., GCN Circ. 39891; Malesani et al., GCN Circ. 39893; Lian et al., GCN Circ. 39894; Page et al., GCN Circ. 39895; Shrestha et al., GCN Circ. 39896; Perley & Bochenek, GCN Circ. 39902; Kumar et al., GCN Circ. 39904; Dennefeld et al., GCN Circ. 39905; Pankov et al., GCN Circ. 39906; Pérez-Fournon et al., GCN Circ. 39912; Tarasenkov et al., GCN Circ. 39913; Mo et al., GCN Circ. 39914), we detect a source with i = 22.23 +/- 0.15. Compared to our previous observation at about 7.65 hours after the trigger, the temporal decay index is about -1.0. We acknowledge the excellent support of the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and thank the COLIBRÍ and DDRAGO engineering teams. View this GCN Circular online at https://gcn.nasa.gov/circulars/39930. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37947] GRB 250329B: 1.6m Mephisto Optical Upper Limits
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39929 SUBJECT: GRB 250329B: 1.6m Mephisto Optical Upper Limits DATE: 25/03/29 18:00:42 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Xinlei Chen, Brajesh Kumar, Jianhui Lian, Xufeng Zhu, Fanchuan Kong, Yaosong Yu, Yu Pan, Xingzhu Zou, Guowang Du, Yuan Fang, Jinghua Zhang, Tao Wang, Helong Guo, Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team: We observed the field of SVOM/ECLAIRs-detected GRB 250329B (Xie et al., GCN 39925) with 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Simultaneous uvgriz band observations were started from 2025-03-29 UT13:29:03 (~1.3 hr after the trigger) and multiple frames with different exposure times were taken under moderate sky conditions. In our stacked images, no new optical source was detected, consistent with Xin et al. (GCN 39926). The 5-sigma limiting magnitudes in different bands are below: Start_Time(UT) | Band | Exp(s) | LimMag(AB) ---------------------|------|--------------|------------ 2025-03-29T13:29:05 | u | 180*2, 300*2 | >19.93 2025-03-29T13:43:31 | v | 180*1, 300*2 | >19.76 2025-03-29T13:29:04 | g | 50*6, 300*2 | >20.58 2025-03-29T13:43:30 | r | 50*3, 300*2 | >20.55 2025-03-29T13:29:03 | i | 79*4, 300*2 | >20.68 2025-03-29T13:43:30 | z | 79*2, 300*2 | >19.65 ------------------------------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21. ------------------------------------------------------------------------------------------------- View this GCN Circular online at https://gcn.nasa.gov/circulars/39929. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37946] LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39928 SUBJECT: LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search DATE: 25/03/29 16:53:25 GMT FROM: Zsuzsa Marka at IceCube/Columbia University <zsuzsa(a)astro.columbia.edu> IceCube Collaboration (http://icecube.wisc.edu/) reports: We have performed a search for track-like muon neutrino candidate events detected by IceCube consistent with the sky localization of the low-significance gravitational-wave candidate event S250329fl in a time range of 1000 seconds centered on the alert event time (2025-03-29T14:58:44.29 UTC to 2025-03-29T15:15:24.29 UTC) [1,2]. During this time period, IceCube was collecting good quality data. A single hypothesis test was conducted using a Bayesian approach to quantify the joint GW + neutrino event significance, which assumes a binary merger scenario and accounts for known astrophysical priors, such as GW source distance, in the statistical significance estimation [3]. Two track-like events were found in spatial and temporal coincidence with the gravitational-wave candidate S250329fl calculated from the map circulated in the S250329fl-2-Preliminary notice. This represents an overall p-value of 5.05e-05 for the Bayesian search. The p-value measures the consistency of the observed track-like events with the known atmospheric backgrounds for this single map (not accounting for statistical trials from multiple GW events). Further details are available at https://gcn.nasa.gov/missions/icecube and at https://roc.icecube.wisc.edu/public/LvkNuTrackSearch. Properties of the coincident events are shown below: dt(s) RA(deg) Dec(deg) Angular uncertainty(deg) p-value(Bayesian) ------------------------------------------------------------------------------------- 390.16 279.03 -49.69 0.98 0.0000505 153.42 87.16 47.51 4.07 0.0915 where: dt = Time of track event minus time of GW trigger (sec) Angular uncertainty = Angular uncertainty of track event: the radius of a circle representing 90% CL containment by area. p-value = the p-value for this specific track event from this search. 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] M. G. Aartsen et al 2020 ApJL 898 L10 [2] Abbasi et al. Astrophys.J. 944 (2023) 1, 80 [3] I. Bartos et al. 2019 Phys. Rev. D 100, 083017 View this GCN Circular online at https://gcn.nasa.gov/circulars/39928. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37945] GRB250329A: REM optical afterglow detection
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39927 SUBJECT: GRB250329A: REM optical afterglow detection DATE: 25/03/29 16:25:26 GMT FROM: Matteo Ferro at INAF-OAB <matteo.ferro(a)inaf.it> M. Ferro, R. Brivio, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB), and A. Melandri (INAF-OAR) report on behalf of the REM team: We observed the field of GRB250329A (Wang et al., GCN 39916) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, K bands, starting on 2025 March 29 at 04:19:30 UT (i.e. 96 s after the SVOM trigger), and lasting for about 3 hours. From preliminary photometry we detect the counterpart in the optical images at the position of the optical afterglow (Watson et al., GCN 39915; Wang et al., GCN 39917; Schneider et al., GCN 39918; Ghosh et al., GCN 39922) with the following magnitude: r = 17.2 +/- 0.1 (AB; calibrated against the Pan-STARRS catalogue) at a mid-time of t - t0 = 165 s after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39927. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37944] GRB 250329B: GWAC-F50A optical upper limit
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39926 SUBJECT: GRB 250329B: GWAC-F50A optical upper limit DATE: 25/03/29 13:31:32 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L. P. Xin(NAOC), Y. G. Yang(HNU), X. H. Han, C. WU, Y. L. Qiu, J. Wang, H. L. Li, X .M. Lu, R. S. Zhang, Y. Xu, L. Huang, H. B. Cai, Y. J. Xiao, P. P. Zhang, L. Lan, W. J. Xie, Z. H. Yao, J. Y. Wei(NAOC), X. G. Wang, E. W. Liang(GXU) report on behalf of the SVOM/F50A team: We began to observe GRB 250328A (Xie et al., GCN 39925) with 50cm telescope (GWAC-F50A) at Xinglong station, China, at 2025-03-29T12:27:17.58 (UT), about 7.0 min after the burst. With the first observations with exposure time of 4*100 sec, no any uncatalogued source was detected in our stacked image down to a 3 sigma limit magnitude of 18.5 mag in R band, at the mid time of 10.3 min after the burst, comparing to several nearby USNO B1.0 stars. Further observations are ongoing. We acknowledge the excellent support from observation assistant Yangtong Zheng and Winlong Dong. View this GCN Circular online at https://gcn.nasa.gov/circulars/39926. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37943] GRB 250329B: SVOM detection of a faint transient
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39925 SUBJECT: GRB 250329B: SVOM detection of a faint transient DATE: 25/03/29 13:24:22 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> W.J. Xie (NAOC), Y.H. Cheng (SWIFAR, YNU), B.T. Wang (YNAO, CAS), O. Godet, S. Guillot (IRAP), S. Schanne (CEA), M. Brunet (IRAP) on behalf of the SVOM mission team. SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250329B (SVOM burst-id sb25032902) starting at 2025-03-29T12:10:18 UTC (Tb). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected by the Image Trigger (IMT), which produced a sequence of 2 alerts. IMT provided the alert with the best signal-to-noise-ratio (SNR) of 7.33 in the 8-120 keV energy band over a time window of 40.96 seconds starting at Tb. The localization of the best alert is R.A., Dec 207.6731, 52.8853 degrees: RA (J2000) = 13h50m41.55s Dec (J2000) = 52d53m07.02s with a 90% C.L. radius of 10.69 arcmin (including systematic error of 2 arcmin added in quadrature). No immediate slew was performed on this burst, because its significance was below the slew threshold. A SVOM ToO will be performed. 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. The Burst Advocate (BA) on shift for this burst is Wenjin XIE: xiewj(a)bao.ac.cn. Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/39925. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37942] GRB 250329A: Swift-XRT afterglow detection
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39924 SUBJECT: GRB 250329A: Swift-XRT afterglow detection DATE: 25/03/29 12:53:30 GMT FROM: P.A. Evans at U. Leicester <pae9(a)leicester.ac.uk> S. Dichiara (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: We have analysed 1.6 ks of XRT data for the SVOM/ECLAIRs-detected burst GRB 250329A, from 6.8 ks to 13.1 ks after the SVOM/ECLAIRs trigger. The data are entirely in Photon Counting (PC) mode. Using 1005 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 197.44646, +9.49619 which is equivalent to: RA (J2000): 13h 09m 47.15s Dec(J2000): +09d 29' 46.3" with an uncertainty of 4.7 arcsec (radius, 90% confidence). This position is 51 arcsec from the SVOM/ECLAIRs position, and 3.3 arcsec from the optical candidate first reported by Watson et al., (GCN. Circ 39915). The source has a mean count rate of 3.0e-02 ct/sec and shows weak (1.4-sigma) indications of fading. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00019666. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39924. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37941] GRB 250328A: SVOM/VT optical observation
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39923 SUBJECT: GRB 250328A: SVOM/VT optical observation DATE: 25/03/29 12:50:45 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L.P. Xin, Y. L. Qiu, C. Wu, J. Wang, W.J. Xie, Z. H. Yao, Y. Xu, P. P. Zhang, X. H. Han, Y. J. Xiao, H. B. Cai, J. Y. Wei (NAOC)，M. Brunet, J. Malzac (IRAP) report on behalf of the SVOM team: SVOM performed a ToO observation on the burst triggered by SVOM/ECLAIRs (Brunet et al., GCN 39910). SVOM/VT began observing the field from about 2 hours to 7 hours after the burst in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X band downlinked data, the candidate reported (Schneider et al., GCN 39919, Schneider et al., GCN 39920) was clearly detected in stack images in both channels. The magnitudes are: VT_R=21.7+/- 0.1 mag(AB) and VT_B=22.0+/0.1 mag(AB) with the mid time of 4.85 hours after the burst. The photometry has not been corrected for the Galactic extinction. No any significant fading with larger than 0.2 mag during our observations was found. Further observations are 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/39923. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37940] GRB 250329A: Fading optical counterpart detection by LCO.
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39922 SUBJECT: GRB 250329A: Fading optical counterpart detection by LCO. DATE: 25/03/29 11:20:41 GMT FROM: ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994(a)gmail.com> Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Rahul Gupta (NASA GSFC), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES) on behalf of a larger collaboration. We observed the field of the GRB 250329A triggered by the SVOM/ECLAIRs (Wang et al., GCN 39916) in the B, V filter of the 1-meter Sinistro telescope at the Las Cumbres Observatory Global Telescope (LCOGT) node located at McDonald Observatory. The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel). Observations began on March 29, 2025, starting 1.49 hours after the GRB trigger. We clearly detect the optical transient (OT) reported by GCNs (Watson et al., GCN 39915, Wang et al. GCN 39917, Schneider et al., GCN 39918) in our B, V band image. -------------------------------------------------------------------------------------------------- |Date| |UTstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude| -------------------------------------------------------------------------------------------------- 2025-03-21 05:46:30.432 1.49 1 x 600 B B = 22.28 +/- 0.08 2025-03-21 05:47:59.424 1.51 3 x 300 V V = 21.95 +/- 0.16 -------------------------------------------------------------------------------------------------- The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39922. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37939] GRB 250328A: SVOM/C-GFT optical upper limit
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39921 SUBJECT: GRB 250328A: SVOM/C-GFT optical upper limit DATE: 25/03/29 11:16:01 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Zhe Kang (CHO), J. Malzac(OMP)，M. Brunet(OMP), Liping Xin(NAOC), Xuhui Han(NAOC), Chao WU (NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC), Yulei, Qiu(NAOC), Jing Wang(NAOC), Jianyan Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of GRB 250328A detected by SVOM/ECLAIRs (sb25032803) with C-GFT. Our observations were started on 2025-03-28T17:14:26 UTC, ~17.50 mins fter the trigger. A series of g, r, and i-band images were obtained. No uncataloged optical counterpart candidates were detected within the SVOM/ECLARIRS source error circle (GCN 39910). Additionally, no sources were detected at the positions of the Swift/XRT Source #2 and the location reported by Schneider et al. (GCN 39919) and Schneider et al. (GCN 3920) in our coadded images. The upper limit magnitudes(3sigma) are, (T-T0)_mid(mins) upper_limit(3sigma) band ---------------------------------------------------------------- 22.65 >20.00 i 24.15 >20.20 g 25.63 >20.11 r The photometry was calibrated with UCAC4 catalog. This result is consistent with the report from Xin et al.(39911). We thank the observation assistants Bowen Li at Jilin observatory for their excellent support. Chinese Ground Follow-up Telescope of SVOM mission is located at Jilin, Changchun Observatory, National Astronomical Observatories, CAS. It has FOV of 1.28 deg x 1.28 deg with a 4k*4k CMOS detector mounted on the primary focus of 1.2-meter-aperure telescope. View this GCN Circular online at https://gcn.nasa.gov/circulars/39921. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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