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

[vsnet-grb-info 38560] EP#01709176612: Swift-XRT counterpart detection of flaring star
by GCN Circulars 22 May '25

22 May '25

TITLE: GCN CIRCULAR NUMBER: 40528 SUBJECT: EP#01709176612: Swift-XRT counterpart detection of flaring star DATE: 25/05/22 19:17:02 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), M. Capalbi (INAF-IASFPA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Einstein Probe/WXT-detected source EP#01709176612, collecting 2.0 ks of Photon Counting (PC) mode data between T0+4.2 ks and T0+9.7 ks after the trigger. A candidate counterpart has been found. The details of this source are: Source 1 (SWIFT J122501.5-521613): ================================== RA (J2000.0): 186.2566 = 12h 25m 01.58s Dec (J2000.0): -52.2705 = -52d 16' 13.8" Error: 3.5 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 23 arcsec from the Einstein Probe/WXT position. Mean rate: 2.883 +/- 0.078 ct s^-1 Mean flux: (9.45 +/- 0.26)e-11 erg cm^-2 s^-1 Peak rate: 5.3 +/- 1.1 ct s^-1 Peak flux: (1.74 +/- 0.37)e-10 erg cm^-2 s^-1 ECF: 3.28e-11 erg cm^-2 ct^-1, assuming NH=2.18e+21 cm^-2, gamma=2.19; determined from a spectral fit. This matches a catalogued X-ray source XMMSL3 J122501.2-521616 in the XMM-NEWTON/XMMSLEWCLN catalogue. Details: Separation: 2.9" from the XRT source Cat Rate: 6.3e-01 +/- 2.6e-01 ct s^-1 Cat Flux: 5.5e-12 +/- 2.3e-12 erg cm^-2 s^-1 (0.3-10 keV) so the source is 4.5-sigma above the catalogued flux. The source may be fading, at the 1.0-sigma level. A SIMBAD object `WISEA J122501.45-521614.6' is 1.5" away. There are 2 2MASS objects within the source's 3-sigma error radius. All fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated. This is most likely a stellar flare of a Young Stellar Object Candidate Gaia DR3 6077506855610363648 (GCN 40523, Song et al.) The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/EP. This circular is an officicial product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40528. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38559] Fermi GRB 250521D: Global MASTER-Net observations report
by GCN Circulars 22 May '25

22 May '25

TITLE: GCN CIRCULAR NUMBER: 40527 SUBJECT: Fermi GRB 250521D: Global MASTER-Net observations report DATE: 25/05/22 19:15:49 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 250521D ( Fermi GBM team, GCN 40516) errorbox 74439 sec after notice time and 74480 sec after trigger time at 2025-05-22 19:03:16 UT, with upper limit up to 18.2 mag. The observations began at zenith distance = 63 deg. The sun altitude is -20.4 deg. The galactic latitude b = 10 deg., longitude l = 52 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2877804 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 74510 | 2025-05-22 19:03:16 | MASTER-Kislovodsk | (18h 46m 09.15s , +22d 14m 31.3s) | C | 60 | 17.9 | 74594 | 2025-05-22 19:04:40 | MASTER-Kislovodsk | (18h 54m 44.61s , +22d 15m 50.5s) | C | 60 | 17.4 | 74879 | 2025-05-22 19:09:25 | MASTER-Kislovodsk | (18h 31m 37.29s , +20d 22m 21.4s) | C | 60 | 18.2 | 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/40527. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38558] Fermi trigger No 769533898: Global MASTER-Net observations report
by GCN Circulars 22 May '25

22 May '25

TITLE: GCN CIRCULAR NUMBER: 40526 SUBJECT: Fermi trigger No 769533898: Global MASTER-Net observations report DATE: 25/05/22 16:31:05 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) started inspect of the Fermi GRB250521.64 (trigger No 769533898,19h 21m 48.00s , -31d 22m 01.2s, R=12.57) errorbox 44915 sec after notice time and 44947 sec after trigger time at 2025-05-22 03:54:01 UT, with upper limit up to 17.1 mag. The observations began at zenith distance = 41 deg. The sun altitude is -76.5 deg. The galactic latitude b = -20 deg., longitude l = 7 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2877526 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 44968 | 2025-05-22 03:54:01 | MASTER-OAFA | (18h 31m 55.71s , -33d 31m 15.7s) | C | 40 | 17.1 | 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/40526. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38557] Fermi trigger No 769499303: Global MASTER-Net observations report
by GCN Circulars 22 May '25

22 May '25

TITLE: GCN CIRCULAR NUMBER: 40525 SUBJECT: Fermi trigger No 769499303: Global MASTER-Net observations report DATE: 25/05/22 10:47:55 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) started inspect of the Fermi GRB250521.24 (trigger No 769499303,12h 46m 07.20s , -30d 31m 48.0s, R=12.01) errorbox 60162 sec after notice time and 60196 sec after trigger time at 2025-05-21 22:31:35 UT, with upper limit up to 19.0 mag. Observations started at twilight. The observations began at zenith distance = 39 deg. The sun altitude is -10.4 deg. The galactic latitude b = 32 deg., longitude l = 302 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2877064 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 60216 | 2025-05-21 22:31:35 | MASTER-OAFA | (13h 05m 11.76s , -37d 11m 03.5s) | C | 40 | 16.7 | 60227 | 2025-05-21 22:31:35 | MASTER-OAFA | (13h 16m 35.65s , -36d 46m 35.5s) | C | 60 | 12.6 | 60386 | 2025-05-21 22:34:25 | MASTER-OAFA | (13h 05m 09.04s , -35d 17m 27.8s) | C | 40 | 17.0 | 60397 | 2025-05-21 22:34:25 | MASTER-OAFA | (13h 16m 15.99s , -34d 53m 05.7s) | C | 60 | 18.7 | 60555 | 2025-05-21 22:37:14 | MASTER-OAFA | (12h 52m 33.75s , -29d 34m 03.7s) | C | 40 | 17.4 | 60566 | 2025-05-21 22:37:14 | MASTER-OAFA | (13h 03m 00.21s , -29d 09m 57.2s) | C | 60 | 19.0 | 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/40525. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38556] GRB 250521D: DDOTI Optical Upper Limit
by GCN Circulars 22 May '25

22 May '25

TITLE: GCN CIRCULAR NUMBER: 40524 SUBJECT: GRB 250521D: DDOTI Optical Upper Limit DATE: 25/05/22 10:30:43 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Rosa L. Becerra (U Roma), Sahil Atri (U Roma), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report: We observed the field of GRB 250521D detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 40516) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2025-05-22 UTC. DDOTI observed the field of GRB 250521D from 05:34 UTC to 09:09 UTC (from T+7.2 h to T+ 10.8 h after the trigger) and obtained a total exposure of 1.7 hours, alternating with other scientific programs. Comparing our observations to the USNO-B1 and Pan-STARRS PS1 DR2 catalogues, we detect no uncatalogued fading sources within the observed field down to a 10-sigma limiting AB magnitude of: w > 21.0 This value is not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40524. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38555] The EP-WXT trigger 01709176612 is likely a flaring star
by GCN Circulars 22 May '25

22 May '25

TITLE: GCN CIRCULAR NUMBER: 40523 SUBJECT: The EP-WXT trigger 01709176612 is likely a flaring star DATE: 25/05/22 06:37:57 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. J. Song (NAO, CAS), Q. C. Shui (IHEP, CAS), H. Q. Cheng, Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709176612 at the time of 2025-05-22T05:56:51, is likely a stellar flare associated with a Young Stellar Object Candidate Gaia DR3 6077506855610363648. The estimated flux of the flare is around 6e-11 erg/s/cm^2 in 0.5-4 keV, corresponding to an X-ray luminosity of around 1.15e32 erg/s. 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/40523. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38554] GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
by GCN Circulars 22 May '25

22 May '25

TITLE: GCN CIRCULAR NUMBER: 40522 SUBJECT: GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB DATE: 25/05/22 06:31:47 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk> D. O'Neill, A. Kumar, B. P. Gompertz, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, B. Godson, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022) in response to the Fermi/GBM alert for GRB 250521D (GCN 40516, Fermi GBM team). During targeted follow-up of GRB 250521D (Fermi GBM team, GCN 40516), we detected the counterpart candidate reported by LAST in GCN 40520 (Konno et al., GCN 40520) with L = 19.72 ± 0.10 AB mag (+3.19h post trigger), and L = 19.68 ± 0.19 AB mag (+5.08h post trigger). We note however that we have a pre-trigger 5-sigma detection of the source at 2025-05-21 01:24:41 (-20.95h pre-trigger ) with L = 19.38 ±0.19 AB mags, indicating this is likely an unrelated event. The GOTO-L (400-700nm) and LAST unfiltered (comparable to Gaia Bp) bandpasses are roughly equivalent, and the combined GOTO and LAST observations suggest a variable source. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/40522. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38553] GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 22 May '25

22 May '25

TITLE: GCN CIRCULAR NUMBER: 40521 SUBJECT: GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 25/05/22 05:38:13 GMT FROM: Camila Angulo Valdez at UNAM <camiangulo(a)astro.unam.mx> Camila Angulo (UNAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (AUS), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Noémie Globus (UNAM), 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), A. Foisseau (APC) and C. Lachaud (APC): We imaged the field of the SVOM GRB 250521B (Foisseau et al., GCN Circ. 40513) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-05-22 03:29 to 04:08 UTC (from 23.2 to 23.8 hours after the trigger) and obtained 32 minutes of exposure in the i filter. 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 PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the ECLAIRs source position (Foisseau et al., GCN Circ. 40513) down to the following 5-sigma limit: i > 22.8 Further observations and analysis are ongoing. 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/40521. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38552] GRB 250521D: LAST tentative optical counterpart candidate
by GCN Circulars 22 May '25

22 May '25

TITLE: GCN CIRCULAR NUMBER: 40520 SUBJECT: GRB 250521D: LAST tentative optical counterpart candidate DATE: 25/05/22 04:07:48 GMT FROM: Ruslan Konno at Weizmann Institute of Science <ruslankonno(a)gmail.com> R. Konno (WIS), S. Garrappa (WIS), E. A. Zimmerman (WIS), A. Horowicz (WIS), E. O. Ofek (WIS), S. Ben-Ami (WIS), D. Polishook (WIS), O. Yaron (WIS), S. Fainer (WIS), A. Krassilchtchikov (WIS), Y. M. Shani (WIS), E. Segre (WIS), A. Gal-Yam (WIS), S. Spitzer (WIS), and K. Rybicki (WIS) on behalf of the LAST Collaboration We report observations of GRB 250521D (GCN #40516), detected by Fermi-GBM, with the Large Array Survey Telescope (LAST; Ofek et al. 2023; Ben-Ami et al. 2023). We observe the field of GRB 250521D using 20 telescopes, each with a FoV of 7.4 deg^2 and no filter (clear - similar to the GAIA Bp band) over several epochs. In each epoch, we coadd 20x20s images. The standard limiting magnitude of a single 20x20s coadd is about 20.5 (AB mag). We began observations at 2025-05-21 22:47:38 UTC (T-T0 = 25.7 min). The observations are performed by tiling the 90% confidence area, supplied by the glg_healpix_all_bn250521932.fit map, with predefined LAST observation fields. We cover a total area of about 240 deg^2, corresponding to an integrated localization probability of about 56%. We found one new optical transient candidate, reported as AT 2025kze to TNS, in our automatic transient-detection pipeline (Konno et al., in prep.) which showed a brightening during observations. The candidate coordinates are RA, Dec = 278.4350830, 17.5896389 deg, which is 1.95 deg away from the best-fit position reported in GCN #40516. The associated photometry is | JD | T-T0 (h) | Mag | |----------------|----------|-------------------| | 2460817.45206228 | 0.48 | 20.50 (UL) | | 2460817.46226134 | 0.73 | 20.50 (UL) | | 2460817.48502633 | 1.27 | 20.105 ± 0.098 | | 2460817.50906663 | 1.85 | 19.722 ± 0.083 | The reported magnitudes are in the AB system, calibrated against the GAIA DR3 catalog, with no filter (clear). The position shows no LAST detections prior to the GRB trigger time, with the latest observations dating to 2025-04-21 01:33:59 UTC. Neither do we find any evidence of this source prior to the GRB trigger time in the ZTF observations provided by the Lasair broker (Smith et al. 2019), or the ATLAS forced photometry server (Shingles et al. 2021). There is a faint ambiguous extended underlying source at the candidate position visible in survey images provided by the SDSS SkyServer. Follow-up observations are encouraged to determine the nature of this candidate or the underlying source present in survey images. LAST is a survey telescope array of the Weizmann Astrophysical Observatory (https://www.weizmann.ac.il/wao/) View this GCN Circular online at https://gcn.nasa.gov/circulars/40520. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38551] GRB 250520A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 22 May '25

22 May '25

TITLE: GCN CIRCULAR NUMBER: 40519 SUBJECT: GRB 250520A: CALET Gamma-Ray Burst Monitor detection DATE: 25/05/22 02:30:45 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> Y. Asaoka (ICRR), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The short GRB 250520A (Swift Detection: Eyles-Ferris et al., GCN Circ. 40491; SVOM/GRM observation: Wang et al., GCN Circ. 40495; AstroSat CZTI detection: Tembhurnikar et al., GCN Circ. 40497; Konus-Wind detection: Frederiks et al., GCN Circ. 40512) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 02:42:16.72 UTC on 20 May 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1431743946/index.html) The burst signal was seen by all CGBM detectors. The burst light curve shows a single pulse that starts at T+0.06 sec, peaks at T+0.19 sec, and ends at T+0.31 sec. The T90 and T50 durations measured by the SGM data are 0.21 +/- 0.04 sec and 0.09 +/- 0.01 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1431743946/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/40519. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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