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

[vsnet-grb-info 37958] GRB 250329B: Swift-XRT afterglow detection
by GCN Circulars 30 Mar '25

30 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39939 SUBJECT: GRB 250329B: Swift-XRT afterglow detection DATE: 25/03/30 08:26:45 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU), D.N. Burrows (PSU), M. A. Williams (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: We have analysed 1.1 ks of XRT data for the SVOM/ECLAIRs-detected burst GRB 250329B, from 7.4 ks to 8.5 ks after the SVOM/ECLAIRs trigger. The data are entirely in Photon Counting (PC) mode. An uncatalogued X-ray source is found which is substantially brighter than an upper limit derived from the Rosat All-Sky Survey and is thus likely the afterglow. Using 1140 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 = 207.66921, +52.82343 which is equivalent to: RA (J2000): 13h 50m 40.61s Dec(J2000): +52d 49' 24.3" with an uncertainty of 3.3 arcsec (radius, 90% confidence). This position is 3.7 arcmin from the SVOM/ECLAIRs position. We cannot at this time determine whether the source is fading. A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 3.2 (+0.9, -0.8). The best-fitting absorption column is 7.1 (+4.0, -3.1) x 10^21 cm^-2, in excess of the Galactic value of 1.3 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 2.6 x 10^-11 (1.4 x 10^-10) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 7.1 (+4.0, -3.1) x 10^21 cm^-2 Galactic foreground: 1.3 x 10^20 cm^-2 Excess significance: 3.8 sigma Photon index: 3.2 (+0.9, -0.8) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00019667. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39939. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37957] GRB 250330A: Swift detection of a burst
by GCN Circulars 30 Mar '25

30 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39938 SUBJECT: GRB 250330A: Swift detection of a burst DATE: 25/03/30 06:28:16 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> S. B. Cenko (GSFC), K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 06:07:38 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250330A (trigger=1299776). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 252.790, -86.870 which is RA(J2000) = 16h 51m 10s Dec(J2000) = -86d 52' 11" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 10 sec. The peak count rate was ~5800 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 06:08:51.3 UT, 73.2 seconds after the BAT trigger. Due to the proximity of Swift to the SAA, XRT centroided on a cosmic ray. Given the short visibility window, no other data are available at this time. UVOT data are not available at this time. Although this trigger occurred while Swift was close to the SAA, the BAT light-curve shows a definite peak, and Fermi-GBM also triggered at the same time. Burst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/39938. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37956] Swift GRB250330.26: Global MASTER-Net observations report
by GCN Circulars 30 Mar '25

30 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39937 SUBJECT: Swift GRB250330.26: Global MASTER-Net observations report DATE: 25/03/30 06:21:28 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB250330.26 (trigger No 1299776,16h 51m 09.60s , -86d 52m 12.0s, R=0.05) errorbox 47 sec after notice time and 74 sec after trigger time at 2025-03-30 06:08:53 UT, with upper limit up to 19.1 mag. The observations began at zenith distance = 56 deg. The sun altitude is -55.5 deg. The galactic latitude b = -26 deg., longitude l = 306 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2827980 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 80 | MASTER-OAFA | C | 10 | 18.6 | 115 | MASTER-OAFA | C | 20 | 19.1 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39937. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37955] GRB250328A: A fading optical afterglow confirmed by SVOM/VT
by GCN Circulars 30 Mar '25

30 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39936 SUBJECT: GRB250328A: A fading optical afterglow confirmed by SVOM/VT DATE: 25/03/30 03:36:32 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, J. Wang, W. J. Xie, B.T. Wang (YNAO, CAS), Z. H. Yao, Y. N. Ma, 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/VT performed a second ToO observation on the burst triggered by SVOM/ECLAIRs (Brunet et al., GCN 39910). The observation began from about 20.65 hours to 21.5 hours after the burst in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The candidate reported (Schneider et al., GCN 39919, Schneider et al., GCN 39920) was fading by about one magnitude in stack images in both channels, compared to the previous brightness reported by Li et al. GCN 39923. The magnitude is VT_R = 22.8+/-0.2 mag(AB) at the mid time of 21.05 hours after the burst. The photometry has not been corrected for the Galactic extinction. We proposed that this candidate is the optical counterpart of GRB 250328A. 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/39936. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37954] GRB 250329B: SVOM/C-GFT optical upper limit
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39935 SUBJECT: GRB 250329B: SVOM/C-GFT optical upper limit DATE: 25/03/29 23:27:41 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Chao WU (NAOC), W.J. Xie (NAOC), Y.H. Cheng (SWIFAR, YNU), B.T. Wang (YNAO, CAS), Zhe Kang (CHO), Liping Xin(NAOC), Xuhui Han(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 250329B detected by SVOM/ECLAIRs (sb25032902) with C-GFT. Our observations were started on 2025-03-29T12:50:31 UTC, ~40.20 mins after the trigger. No any source was detected in our stacked image within the source error circle of the X-ray Swift/XRT (source #1: https://www.swift.ac.uk/SVOM/SVOM_FIELD00008/ ). The limiting magnitude(3 sigma) in i band is 19.80 mag at the middle time of 41.95 minutes after the burst. The photometry was calibrated with UCAC4 catalog. This result is consistent with the reports (Xin et al., GCN 39926, Chen et al., GCN 39929, and Xin et al., GCN 39931). We thank the observation assistants Yinhuai Hao and 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/39935. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37953] LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39934 SUBJECT: LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1) DATE: 25/03/29 22:30:24 GMT FROM: Isaac McMahon at University of Zürich <isaac.mcmahon(a)ligo.org> S. MacBride (UZH), I. McMahon (UZH), M. Soares-Santos (UZH), reporting on behalf of the Dark Energy Survey Gravitational Wave (DESGW) Team: At 01:43 UTC, March 29th, the Dark Energy Camera (DECam) began the first epoch of observations in response to the LVK alert issued for the candidate gravitational-wave event S250328ae (GCN 39898). We observed eight fields centered on the following ICRS coordinates: (145.286221, 10.615360) (145.996500, 12.108130) (143.786221, 10.715360) (144.496500, 12.208130) (144.069167, 9.115670) (143.344621, 7.609550) (145.900667, 13.593470) (142.620092, 6.103430) These pointings cover the 90% localization region of candidate gravitational-wave event S250328ae. All fields were observed in DECam r, i, and z filters with 90-second exposures. The limiting magnitude achieved is ~22.7 in r-band, ~22.1 in i-band, and ~21.4 in z-band. We process the images with our difference imaging pipeline (Herner et al. 2020) using DES and public DECam images as templates. We employ the autoscan machine learning code (Goldstein et al 2015) to reject subtraction artifacts. Candidates were selected by requiring at least two high signal to noise detections. We also require an autoscan score of at least 0.7 on at least one of those detections. We also match our candidates against the ALLWISE, Milliquas, and Quaia AGN catalogs (Secrest et al 2015, Flesch 2023, Storey-Fisher et al 2024) within the LVK localization volume to determine if any correspond to known active galactic nuclei. After candidate selection, we report the 20 high confidence candidates listed below. After vetting and identification, 8 candidates are classified as nuclear candidates (likely active galactic nuclei), 8 candidates as possible supernovae, and 3 other candidates do not fall in either category. 1 additional candidate (2292763) has been identified as a known AGN WISEA J093710.05+082057.2. We have numerous other transient candidates which require further observation to confidently classify. Further observations are ongoing, and we encourage followup of the 20 candidates identified herein. | TYPE | ID | ATNAME | RA | DEC | MAG_R | MAG_R_ERR | MAG_I | MAG_I_ERR | MAG_Z | MAG_Z_ERR | | -------- | ------- | --------- | ---------- | ---------- | ----- | ---- | ----- | ---- | ----- | ---- | | SN_LIKE | 2290892 | AT2025gei | 143.636743 | 9.980209 | N/A | N/A | 20.59 | 0.03 | N/A | N/A | | OTHER | 2292987 | AT2025gej | 143.183373 | 6.893136 | 21.37 | 0.04 | 21.45 | 0.08 | N/A | N/A | | AGN_LIKE | 2290036 | AT2025gek | 145.199481 | 10.828527 | 20.77 | 0.04 | 20.62 | 0.03 | 20.69 | 0.1 | | SN_LIKE | 2290467 | AT2020woa | 144.388798 | 10.255536 | 19.87 | 0.02 | N/A | N/A | 20.1 | 0.04 | | SN_LIKE | 2290524 | AT2025gel | 144.524917 | 10.199936 | N/A | N/A | N/A | N/A | 20.47 | 0.06 | | OTHER | 2290001 | AT2025avp | 144.806008 | 10.632223 | 20.36 | 0.02 | 20.19 | 0.02 | 20.22 | 0.06 | | SN_LIKE | 2291473 | AT2025gem | 144.706509 | 11.560317 | 20.92 | 0.03 | N/A | N/A | 21.22 | 0.1 | | AGN_LIKE | 2293190 | AT2025cvb | 144.191297 | 10.828462 | 20.86 | 0.03 | 20.87 | 0.03 | N/A | N/A | | AGN_LIKE | 2290623 | AT2025gen | 144.112464 | 11.641817 | 21.4 | 0.04 | 21.3 | 0.08 | 21.37 | 0.12 | | SN_LIKE | 2292782 | AT2025geo | 144.928578 | 10.349243 | 20.92 | 0.04 | 21.07 | 0.04 | N/A | N/A | | SN_LIKE | 2291779 | AT2025gej | 143.182187 | 6.894174 | N/A | N/A | N/A | N/A | 20.76 | 0.06 | | OTHER | 2290762 | AT2025gep | 144.259773 | 11.511316 | 21.29 | 0.04 | N/A | N/A | N/A | N/A | | SN_LIKE | 2290334 | AT2025geq | 145.235616 | 12.469694 | 20.22 | 0.02 | 20.57 | 0.03 | N/A | N/A | | AGN_LIKE | 2290970 | AT2025ger | 142.543835 | 6.090899 | 21.71 | 0.05 | 21.43 | 0.06 | 21.28 | 0.09 | | AGN_LIKE | 2292040 | AT2025ges | 144.438216 | 9.885617 | 21.72 | 0.07 | 21.75 | 0.11 | 21.93 | 0.17 | | SN_LIKE | 2292645 | AT2025get | 144.053408 | 11.422277 | N/A | N/A | 22.67 | 0.21 | N/A | N/A | | AGN_LIKE | 2293517 | AT2025geu | 145.956024 | 12.381673 | 21.73 | 0.08 | 21.65 | 0.07 | N/A | N/A | | AGN_LIKE | 2291833 | AT2025gev | 143.241035 | 8.651865 | 22.16 | 0.09 | 21.99 | 0.13 | 22.22 | 0.22 | | AGN_LIKE | 2294074 | AT2025gew | 144.291829 | 8.349302 | 22.23 | 0.1 | 21.85 | 0.11 | N/A | N/A | | AGN | 2292763 | AT2025gex | 146.071329 | 11.839902 | 21.89 | 0.11 | 21.92 | 0.12 | 21.05 | 0.1 | The DECam Search & Discovery Program for Optical Signatures of Gravitational Wave Events (DESGW) is carried out by the Dark Energy Survey (DES) collaboration in partnership with wide-ranging groups in the community. DESGW uses data obtained with the Dark Energy Camera (DECam), which was constructed by the DES collaboration with support from the Department of Energy and member institutions, and utilizes data as distributed by the Science Data Archive at NOIRLAB. NOIRLAB is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. We thank the Cerro Tololo observatory staff for their support in acquiring these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39934. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37952] GRB 250327B: ALMA detection
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39933 SUBJECT: GRB 250327B: ALMA detection DATE: 25/03/29 21:34:47 GMT FROM: Tanmoy Laskar at U of Utah <tanmoylaskar(a)gmail.com> T. Laskar (University of Utah), N. Franz, C. Christy, K. D. Alexander (University of Arizona), E. Berger (Harvard University), R. Chornock (UC Berkeley), W. Fong (Northwestern University), R. Margutti (UC Berkeley), P. Schady (University of Bath), and G. Schroeder (Cornell University), report on behalf of a larger collaboration: “We observed GRB 250327B (Bouchet et al., GCN 39888) with the Atacama Large Millimeter/Submillimeter Array (ALMA) at 97.5 GHz beginning on 2025 March 29 at 01:45 UT (28.5 hours after the burst). Preliminary analysis reveals a mm source with flux density of ~ 0.5 mJy at position: RA (J2000) = 11:47:06.72 Dec (J2000) = +29:50:24.71 with an uncertainty of 0.05" in each coordinate. This is consistent with the X-ray position (Bouchet et al., GCN 39888; Page et al. GCN 39895), optical position (Moskvitin et al., GCN 39889; Xin et al., GCN 39890), and radio position (Christy et al., GCN 39932). We thank the JAO staff, AoD, P2G, and the entire ALMA team for their help with these observations." View this GCN Circular online at https://gcn.nasa.gov/circulars/39933. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37951] GRB 250327B: VLA detection
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39932 SUBJECT: GRB 250327B: VLA detection DATE: 25/03/29 21:32:49 GMT FROM: Tanmoy Laskar at U of Utah <tanmoylaskar(a)gmail.com> C. Christy, N. Franz (University of Arizona), T. Laskar (University of Utah), K. D. Alexander (University of Arizona), E. Berger (Harvard University), R. Chornock (UC Berkeley), W. Fong (Northwestern University), R. Margutti (UC Berkeley), P. Schady (University of Bath), and G. Schroeder (Cornell University), report on behalf of a larger collaboration: “We observed GRB 250327B (Bouchet et al., GCN 39888) with the Karl G. Jansky Very Large Array (VLA) at multiple frequencies beginning on 2025 March 29 at 03:00 UT (29.8 hours after the burst). In preliminary analysis, we detect a radio counterpart at 15.1 GHz with a flux density of ~0.2 mJy at the position: RA (J2000) = 11:47:06.72 +/- 0.08” Dec (J2000) = +29:50:24.89 +/- 0.05” This is consistent with the X-ray position (Bouchet et al., GCN 39888; Page et al. GCN 39895) and optical position (Moskvitin et al., GCN 39889; Xin et al., GCN 39890). Further observations are planned. We thank the VLA staff for scheduling and executing these observations.” View this GCN Circular online at https://gcn.nasa.gov/circulars/39932. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37950] GRB 250329B: SVOM/VT optical upper limit
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39931 SUBJECT: GRB 250329B: SVOM/VT optical upper limit DATE: 25/03/29 19:13:49 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L.P. Xin, H.L. Li, Y. L. Qiu, C. Wu, Z.H. Yao, Y. Xu, P.P. Zhang, J. Wang, Y.N. Ma, X.H. Han, H.B. Cai, J.Y. Wei, W.J. Xie (NAOC), Y.H. Cheng (SWIFAR, YNU), B.T. Wang (YNAO, CAS), J. T. Palmerio (CEA) report on behalf of the SVOM/VT team: SVOM performed a Target of Opportunity observation of GRB 250329B (Xie et al., GCN 39925), starting at 2025-03-29T15:00:16 UT, ~2.85 hours after the SVOM/Eclairs trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. No any source was detected in the stacked images within the errorbox of the X-ray Swift/XRT [source #1]( https://www.swift.ac.uk/SVOM/SVOM_FIELD00008/) . The 3 sigma limits in VT_R is 23.1 mag (AB) at the middle time of 4.0 hours after the burst. This result is consistent with the reports (Xin et al., GCN 39926, Chen et al., GCN 39929). Deeper or redder follow-ups are encouraged to investigate the nature of the burst. 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/39931. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37949] GRB 250329B: SVOM/VT optical upper limit
by GCN Circulars 29 Mar '25

29 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39931 SUBJECT: GRB 250329B: SVOM/VT optical upper limit DATE: 25/03/29 19:13:49 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L.P. Xin, H.L. Li, Y. L. Qiu, C. Wu, Z.H. Yao, Y. Xu, P.P. Zhang, J. Wang, Y.N. Ma, X.H. Han, H.B. Cai, J.Y. Wei, W.J. Xie (NAOC), Y.H. Cheng (SWIFAR, YNU), B.T. Wang (YNAO, CAS), J. T. Palmerio (CEA) report on behalf of the SVOM/VT team: SVOM performed a Target of Opportunity observation of GRB 250329B (Xie et al., GCN 39925), starting at 2025-03-29T15:00:16 UT, ~2.85 hours after the SVOM/Eclairs trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. No any source was detected in the stacked images within the errorbox of the X-ray Swift/XRT [source #1]( https://www.swift.ac.uk/SVOM/SVOM_FIELD00008/) . The 3 sigma limits in VT_R is 23.1 mag (AB) at the middle time of 4.0 hours after the burst. This result is consistent with the reports (Xin et al., GCN 39926, Chen et al., GCN 39929). Deeper or redder follow-ups are encouraged to investigate the nature of the burst. 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/39931. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

2025

2024

2023

2022

2021

vsnet-grb-info March 2025