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

[vsnet-grb-info 38510] GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
by GCN Circulars 17 May '25

17 May '25

TITLE: GCN CIRCULAR NUMBER: 40478 SUBJECT: GRB 250515A:COLIBRÍ optical observations of the GOTO candidate DATE: 25/05/17 06:16:42 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Kin Ocelotl López (UNAM), Alan M. Watson (UNAM), Rosa L. Becerra (U Roma), Benjamin Schneider (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Noémie Globus (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Antonio de Ugarte Postigo (LAM): We imaged the field of the GOTO candidate afterglow (Gompertz et al., GCN Circ. 40464) of the Fermi GRB 250515A (Fermi GBM team., GCN Circ. 40462) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-05-17 03:23 to 05:27 UTC (median epoch 1.30 days after the trigger) and obtained 32 minutes of exposure in the i filter and 3 minutes in each of the g and r filters. The data were reduced and coadded with the COLIBRÍ pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detected the optical candidate at preliminary magnitudes of: g = 20.31 +/- 0.03 r = 20.24 +/- 0.04 i = 20.45 +/- 0.03 This source was also detected by SVOM/VT (Xin et al., GCN Circ. 40474) and Mephisto (Zhang et al., GCN Circ. 40476). Our magnitudes are similar in g, fainter in r, and brighter in i than those reported at 0.71 days by Zhang et al. (GCN Circ. 40746), and these changes are not obviously compatible with the temporal evolution of a GRB afterglow after about 1 day. 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/40478. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38509] Swift GRB 250516A: Global MASTER-Net observations report
by GCN Circulars 17 May '25

17 May '25

TITLE: GCN CIRCULAR NUMBER: 40477 SUBJECT: Swift GRB 250516A: Global MASTER-Net observations report DATE: 25/05/17 05:58:24 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, 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.Sosnovskij (CrAO), 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 GRB 250516A ( A. P. Beardmore et al., GCN 40467) errorbox 54907 sec after notice time and 54930 sec after trigger time at 2025-05-17 05:50:59 UT, with upper limit up to 15.5 mag. The observations began at zenith distance = 77 deg. The sun altitude is -68.5 deg. The galactic latitude b = -50 deg., longitude l = 53 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2872228 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 55020 | MASTER-OAFA | C | 180 | 15.5 | 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/40477. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38508] GRB 250515A: 1.6m Mephisto optical detection
by GCN Circulars 17 May '25

17 May '25

TITLE: GCN CIRCULAR NUMBER: 40476 SUBJECT: GRB 250515A: 1.6m Mephisto optical detection DATE: 25/05/17 05:06:22 GMT FROM: zhjh(a)nao.cas.cn Jinghua Zhang, Yu Pan, Xiangkun Liu, Yiheng Xie, Guowang Du, Yuan Fang, Xinlei Chen, Xingzhu Zou, Helong Guo, Xufeng Zhu, Tao Wang, Brajesh Kumar, Xinzhong Er, Yuanpei Yang, Xiaowei Liu (SWIFAR, YNU) report on behalf of Mephisto Team: We conducted simultaneous multi-band photometric observations of the optical candidate of the likely short GRB 250515A (Fermi GBM team, GCN 40462) with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University, located at the Lijiang Observatory. Mephisto was triggered ~17 hours post-alert and commenced observations starting from 13:47:01 UTC 2025-05-16 in moderate sky conditions. Multiple frames across uvgriz bands were acquired. The optical candidate (B. P. Gompertz et al., GCN 40464; Xin et al., GCN40474) was clearly detected in the stacked images of g and r bands while marginally detected in the u, v, i, z -bands. The preliminary photometry (AB magnitude system) are listed below: | Time-Mid (2025-05-16 UT) | Filter | Exposure | Mag | Mag Err | | 15:02:22 | u | 300sec*3 | 21.17 | 0.27 | | 13:54:44 | v | 300sec*3 | 21.46 | 0.47 | | 15:02:22 | g | 300sec*3 | 20.21 | 0.07 | | 13:54:44 | r | 300sec*3 | 19.91 | 0.08 | | 15:02:22 | i | 300sec*3 | 20.74 | 0.20 | | 13:54:44 | z | 300sec*3 | 20.22 | 0.47 | ------------------------------------------------------------------------------------------------------- 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/40476. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38507] GRB 250516A: AstroSat CZTI detection
by GCN Circulars 17 May '25

17 May '25

TITLE: GCN CIRCULAR NUMBER: 40475 SUBJECT: GRB 250516A: AstroSat CZTI detection DATE: 25/05/17 04:54:01 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long duration GRB 250516A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 40466), and Swift/BAT (Beardmore et al., GCN Circ. 40467). The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed a single burst of emission that peaked at 2025-05-16 14:35:33.81 UTC. The measured peak count rate associated with the burst is 333 (+66, -72) counts/s above the background in the combined data of all quadrants, with a total of 527 (+187, -195) counts. The local mean background count rate was 1349 (+8, -9) counts/s. We measure a T90 of 2.4 (+1.8, -1.2) s from the cumulative Veto light curve. We note that our T90 is low since we detect just the brightest burst episode from the lightcurve seen in other missions (Fermi/GBM, Swift/BAT). This is likely due to the unfavourable orientation of our detectors with respect to the GRB. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40475. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38506] GRB 2500515A/GOTO25cqo: SVOM/VT optical blue color
by GCN Circulars 17 May '25

17 May '25

TITLE: GCN CIRCULAR NUMBER: 40474 SUBJECT: GRB 2500515A/GOTO25cqo: SVOM/VT optical blue color DATE: 25/05/17 01:24:43 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, Z. H. Yao, Y. N. Ma, 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), Y. Wang (PMO, CAS), R. Z. Li (YNAO, CAS), J. X. Cao, D. F. Kong (GXU), J. R. Mao (YNAO, CAS), X. W. Liu (YNU) report on behalf of the SVOM/VT team: SVOM/VT conducted ToO follow-up observations of the optical transient (B. P. Gompertz et al., GCN 40464) which was proposed to be the optical candidate of the GRB 250515A (Fermi GBM team, GCN 40462). The observation started from 2025-05-16T12:16:52 UTC (15.50 hours after the Fermi GBM trigger) to 2025-05-16T19:20:30 UTC in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical candidate (B. P. Gompertz et al., GCN 40464) was clearly detected in VT both channels, which is not found in the legacy survey. The brightness in AB magnitude was estimated to be: Mid time (hour) | Band | Exposure Time (second) | Magnitude | Magnitude error 22.27 | VT_B | 32x70 | 20.25 | 0.03 22.27 | VT_R | 32x70 | 20.56 | 0.05 Our photometry was not corrected for Galactic extinction. The source shows no significant fading or brightening in both channels during our observations. However, given the blue color and the possible association to the likely short GRB (Fermi GBM team, GCN 40462), more multiband follow-up observations are encouraged. 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/40474. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38505] GRB 250516A: Fermi GBM Observation
by GCN Circulars 16 May '25

16 May '25

TITLE: GCN CIRCULAR NUMBER: 40473 SUBJECT: GRB 250516A: Fermi GBM Observation DATE: 25/05/16 23:59:42 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 14:35:29.28 UT on 16 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250516A (trigger 769098934/250516608). which was also detected by Swift BAT (A. P. Beardmore et al. 2025, GCN 40467). The Fermi GBM on-ground location is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 36 degrees. The GBM light curve consists of two peaks with a duration (T90) of about 21.8 s (50-300 keV). The time-averaged spectrum from T0-1.4 to T0+25.2 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.26 +/- 0.07 and the cutoff energy, parameterized as Epeak, is 200 +/- 30 keV. The event fluence (10-1000 keV) in this time interval is (4.8 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+5.1 s in the 10-1000 keV band is 5.8 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/40473. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38504] GRB 250516A: Swift-XRT refined Analysis
by GCN Circulars 16 May '25

16 May '25

TITLE: GCN CIRCULAR NUMBER: 40472 SUBJECT: GRB 250516A: Swift-XRT refined Analysis DATE: 25/05/16 23:13:02 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), J.A. Kennea (PSU), D.N. Burrows (PSU), M.A. Williams (PSU), J.P. Osborne (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.8 ks of XRT data for GRB 250516A, from 108 s to 23.8 ks after the trigger. The data comprise 151 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The late-time light curve (from T0+5.9 ks) can be modelled with a power-law decay with a decay index of alpha=1.45 (+0.18, -0.17). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.44 (+0.13, -0.12). The best-fitting absorption column is 3.5 (+0.5, -0.4) x 10^21 cm^-2, in excess of the Galactic value of 5.8 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.98 (+/-0.12) and a best-fitting absorption column of 3.0 (+/-0.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (5.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.0 (+/-0.5) x 10^21 cm^-2 Galactic foreground: 5.8 x 10^20 cm^-2 Excess significance: 8.2 sigma Photon index: 1.98 (+/-0.12) If the light curve continues to decay with a power-law decay index of 1.45, the count rate at T+24 hours will be 5.8 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.2 x 10^-13 (3.3 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01314210. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40472. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38503] GRB 250516A: Swift/UVOT Detection
by GCN Circulars 16 May '25

16 May '25

TITLE: GCN CIRCULAR NUMBER: 40471 SUBJECT: GRB 250516A: Swift/UVOT Detection DATE: 25/05/16 22:17:55 GMT FROM: Sam Shilling at Lancaster University <shilling.sam(a)gmail.com> S. P. R. Shilling (Lancaster U.) and A. P. Beardmore (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250516A 108 s after the BAT trigger (Beardmore et al., GCN Circ. 40467). A source consistent with the enhanced XRT position (Evans et al., GCN Circ. 40468) is detected in the initial UVOT exposures. The preliminary detection and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 108 1715 411 20.5 +/- 0.3 v 650 1765 136 >18.5 b 576 1691 117 >19.2 u 320 1838 362 >19.7 w1 699 1814 117 >18.8 w2 626 1741 97 >19.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.062 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40471. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38502] GRB 250515A: Swift ToO observations
by GCN Circulars 16 May '25

16 May '25

TITLE: GCN CIRCULAR NUMBER: 40470 SUBJECT: GRB 250515A: Swift ToO observations DATE: 25/05/16 21:26:55 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the Fermi/GBM-detected event GRB 250515A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021829 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Fermi/GBM event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40470. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38501] GRB 250516B: GECAM-B detection of a bright long burst
by GCN Circulars 16 May '25

16 May '25

TITLE: GCN CIRCULAR NUMBER: 40469 SUBJECT: GRB 250516B: GECAM-B detection of a bright long burst DATE: 25/05/16 19:33:50 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by a bright long burst GRB 250516B at 2025-05-16T06:31:34.7 UTC (denoted as T0). According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 40.6 +0.9/-0.7 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecamgrb250516B.png GECAM-B localized this burst to the following position (J2000): Ra: 137.5 deg Dec: 41.4 deg Err: 7.0 deg (1-sigma, statistical only) The time-averaged spectrum from T0-5 s to T0+75 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.00 +/-0.07 and the cutoff energy, parameterized as Epeak, is 367 +46/-36 keV. The event fluence (10-1000 keV) in this time interval is (2.3 +/-0.1)E-04 erg/cm^2. Thus GRB 250516B is consistent with Type II GRBs in the 'Amati' relation diagram, as shown at: https://www.bursthub.cn//admin/static/grb250516B_amati.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/40469. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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