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

[vsnet-grb-info 38480] EP250511a: Gemini optical counterpart observation
by GCN Circulars 13 May '25

13 May '25

TITLE: GCN CIRCULAR NUMBER: 40449 SUBJECT: EP250511a: Gemini optical counterpart observation DATE: 25/05/13 09:07:23 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> J. Sanchez-Sierras (Radboud), R. A. J. Eyles-Ferris (Leicester), A. Martin-Carrillo (UCD), A. J. Levan (Radboud and Warwick), G. Corcoran (UCD), P. G. Jonker (Radboud), F. E. Bauer (SSI and UTA), D. B. Malesani (DAWN/NBI and Radboud), J. A. Quirola-Vasquez (Radboud), report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP250511a (Lian et al., GCN 40429) using the Gemini-South telescope. Observations started on 2025 May 12 at 01:19:15 UT (17.32 hr after the EP trigger), and consisted of 5x60 s exposures in each of the SDSS i and z bands. At the location of the optical counterpart reported by Schneider et al. (GCN 40431) and Li et al. (GCN 40433) an extended source is clearly visible, with a magnitude of i = 23.04 +/- 0.06 (AB system, calibrated against nearby Pan-STARRS objects). This magnitude is brighter than the archival value reported in the Legacy Survey for the underlying candidate host galaxy (Schneider et al., GCN 40431). Image subtraction using PyZOGY (Zackay et al. 2016, doi:10.3847/0004-637X/830/1/27), using the Legacy Survey as template, reveals indeed a residual source with magnitude, i = 23.64 +/- 0.26 (AB system). We thank excellent support from the observing staff at Gemini, in particular Cinthya Rodrigez and Joan Font. View this GCN Circular online at https://gcn.nasa.gov/circulars/40449. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38479] EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 13 May '25

13 May '25

TITLE: GCN CIRCULAR NUMBER: 40448 SUBJECT: EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations DATE: 25/05/13 07:02:52 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H.N. Yang, D. H. Zhao (NAO, CAS), Y. L. Hua (PMO, CAS), Y. J. Zhang (THU), M. J. Liu, J. W. Hu, H. W. Pan, Y. Liu (NAO, CAS), on behalf of the Einstein Probe (EP) team: The X-ray transient EP250512a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (D. H. Zhao et al. GCN 40437). It was also detected by SVOM/ECLAIRs (Pierre Maggi et al. GCN 40439), and followed up by several telescopes ( H. L. Li et al. GCN 40443; L. P. Xin et al. GCN 40444; V.Lipunov et al. GCN 40446; Malte Busmann et al. GCN 40447). Refined analysis of the WXT data shows that the event started at T0 = 2025-05-12T11:20:03 (UTC) and lasted for about 360 s (T90). The peak flux is about 4.2 x 10^(-9) erg/s/cm^2 (T0+135 s). The averaged 0.5-4 keV spectrum of T90 can be fitted by an absorbed power law model with a Galactic hydrogen column density of 5.7 x 10^20 cm^-2 and a photon index of 1.31 (-0.17/+0.18). The derived average unabsorbed 0.5-4 keV flux is 1.13 (-0.13/+0.14) x 10^(-9) erg/s/cm^2. The uncertainties are quoted at the 90% confidence level for the above parameters. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously about 4 min after T0, starting at 2025-05-12T11:23:44 (UTC). Within the WXT error circle, on-ground analysis of the FXT data found an uncatalogued source at R.A. = 215.2043, DEC = -10.1009 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). During the observation a decline in the source flux lasting for a few hundred seconds is observed from the beginning. The averaged 0.5-10 keV FXT spectrum (from T0+291 s to T0+7094 s, with a total exposure time of 4,095 s) can be fitted by an absorbed power law model with a Galactic hydrogen column density of 5.7 x 10^20 cm^-2 and a photon index of 1.45 (+/-0.05). The derived average unabsorbed 0.5-10 keV flux is 3.78 (-0.18/+0.19) x 10^(-11) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. EP-FXT will continue monitoring this source. More follow-up observations are encouraged. The contact TAs of EP250512a are D. H. Zhao and H. N. Yang. Please contact them via email zhaodh(a)bao.ac.cn, hnyang(a)nao.cas.cn if needed. 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/40448. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38478] EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
by GCN Circulars 13 May '25

13 May '25

TITLE: GCN CIRCULAR NUMBER: 40447 SUBJECT: EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart DATE: 25/05/13 03:20:43 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann(a)physik.lmu.de> Malte Busmann (LMU), Brendan O’Connor (Carnegie Mellon U.), Daniel Gruen (LMU), and Antonella Palmese (Carnegie Mellon U.) report: We observed the couterpart of EP250512a/GRB 250512B (Zhao et al., GCN 40437; Maggi et al., GCN 40437; Li et al., GCN 40443; Xin et al., GCN 40444; Lipunov et al., GCN 40446) with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i and J band simultaneously for 10 x 180 s starting at 2025-05-12T21:43:13 UT (0.43 days after the trigger). We only detect the counterpart in the J band at J = (21.6 +/- 0.3) mag. The 3 sigma upper limits for the r and i band are r > 21.9 mag i > 21.2 mag. The r and i band magnitudes are calibrated against the PS1 catalog and the J band is calibrated with the 2MASS Catalog. All magnitudes are provided in the AB system and are not corrected for Galactic extinction. We thank Michael Schmidt from the Wendelstein Observatory staff for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/40447. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38477] EP250512a: Global MASTER-Net observations report
by GCN Circulars 12 May '25

12 May '25

TITLE: GCN CIRCULAR NUMBER: 40446 SUBJECT: EP250512a: Global MASTER-Net observations report DATE: 25/05/12 20:45:41 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the EP250512a ( EP Team et al., GCN 40437) errorbox 28318 sec after notice time and 31541 sec after trigger time at 2025-05-12 20:07:49 UT, with upper limit up to 17.7 mag. The observations began at zenith distance = 30 deg. The sun altitude is -54.2 deg. The galactic latitude b = 46 deg., longitude l = 337 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2868623 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 31571 | 2025-05-12 20:07:49 | MASTER-SAAO | (14h 19m 12.13s , -10d 13m 30.1s) | C | 60 | 17.2 | 31631 | 2025-05-12 20:07:49 | MASTER-SAAO | (14h 19m 12.13s , -10d 13m 30.1s) | C | 180 | 17.7 | Coadd 31650 | 2025-05-12 20:09:08 | MASTER-SAAO | (14h 19m 06.91s , -10d 14m 28.5s) | C | 60 | 17.1 | 31730 | 2025-05-12 20:10:27 | MASTER-SAAO | (14h 19m 12.41s , -10d 13m 58.2s) | C | 60 | 17.2 | 31809 | 2025-05-12 20:11:47 | MASTER-SAAO | (14h 19m 09.57s , -10d 12m 28.8s) | C | 60 | 17.2 | 31869 | 2025-05-12 20:11:47 | MASTER-SAAO | (14h 19m 09.57s , -10d 12m 28.8s) | C | 180 | 17.6 | Coadd 31889 | 2025-05-12 20:13:06 | MASTER-SAAO | (14h 19m 09.61s , -10d 13m 58.7s) | C | 60 | 17.0 | 31968 | 2025-05-12 20:14:25 | MASTER-SAAO | (14h 19m 12.16s , -10d 12m 34.3s) | C | 60 | 17.0 | 32047 | 2025-05-12 20:15:44 | MASTER-SAAO | (14h 19m 07.13s , -10d 13m 22.0s) | C | 60 | 17.0 | 32107 | 2025-05-12 20:15:44 | MASTER-SAAO | (14h 19m 07.14s , -10d 13m 22.0s) | C | 180 | 17.6 | Coadd 32126 | 2025-05-12 20:17:04 | MASTER-SAAO | (14h 19m 05.72s , -10d 12m 20.9s) | C | 60 | 17.1 | 32206 | 2025-05-12 20:18:24 | MASTER-SAAO | (14h 19m 12.92s , -10d 13m 20.0s) | C | 60 | 17.2 | 32286 | 2025-05-12 20:19:43 | MASTER-SAAO | (14h 19m 06.56s , -10d 14m 18.8s) | C | 60 | 17.0 | 32346 | 2025-05-12 20:19:43 | MASTER-SAAO | (14h 19m 06.56s , -10d 14m 18.8s) | C | 180 | 17.5 | Coadd 32366 | 2025-05-12 20:21:04 | MASTER-SAAO | (14h 19m 13.61s , -10d 14m 04.5s) | C | 60 | 16.9 | 32446 | 2025-05-12 20:22:23 | MASTER-SAAO | (14h 19m 11.06s , -10d 12m 36.7s) | C | 60 | 17.0 | 32943 | 2025-05-12 20:30:40 | MASTER-SAAO | (14h 19m 12.88s , -10d 12m 10.3s) | C | 60 | 16.9 | 33003 | 2025-05-12 20:30:40 | MASTER-SAAO | (14h 19m 12.88s , -10d 12m 10.3s) | C | 180 | 17.4 | Coadd 33022 | 2025-05-12 20:32:00 | MASTER-SAAO | (14h 19m 18.93s , -10d 13m 09.3s) | C | 60 | 16.8 | 33102 | 2025-05-12 20:33:19 | MASTER-SAAO | (14h 19m 14.64s , -10d 14m 08.2s) | C | 60 | 16.8 | 33181 | 2025-05-12 20:34:39 | MASTER-SAAO | (14h 19m 21.08s , -10d 14m 06.4s) | C | 60 | 16.9 | 33241 | 2025-05-12 20:34:39 | MASTER-SAAO | (14h 19m 21.08s , -10d 14m 06.4s) | C | 180 | 17.5 | Coadd 33260 | 2025-05-12 20:35:58 | MASTER-SAAO | (14h 19m 18.22s , -10d 12m 20.5s) | C | 60 | 16.9 | 33340 | 2025-05-12 20:37:17 | MASTER-SAAO | (14h 19m 18.96s , -10d 14m 01.5s) | C | 60 | 16.8 | 33419 | 2025-05-12 20:38:37 | MASTER-SAAO | (14h 19m 22.19s , -10d 12m 23.8s) | C | 60 | 16.9 | 33499 | 2025-05-12 20:39:56 | MASTER-SAAO | (14h 19m 16.86s , -10d 13m 02.6s) | C | 60 | 16.8 | 33578 | 2025-05-12 20:41:16 | MASTER-SAAO | (14h 19m 18.30s , -10d 12m 01.7s) | C | 60 | 16.8 | 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/40446. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38476] EP250511a: FTW optical and NIR observations
by GCN Circulars 12 May '25

12 May '25

TITLE: GCN CIRCULAR NUMBER: 40445 SUBJECT: EP250511a: FTW optical and NIR observations DATE: 25/05/12 17:53:13 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann(a)physik.lmu.de> Malte Busmann (LMU), Brendan O’Connor (Carnegie Mellon U.), Daniel Gruen (LMU), and Antonella Palmese (Carnegie Mellon U.) report: We observed the localization of EP250511a (Lian et al., GCN 40429; Li et al., GCN 40434) with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i and J band simultaneously for 10 x 180 s starting at 2025-05-11T21:30:13 UT (0.56 days after the trigger). We do not detect the counterpart (Schneider et al., GCN 40431; Li et al., GCN 40433) placing 3 sigma upper limits at r > 22.4 mag i > 22.0 mag J > 21.8 mag. These upper limits are consistent with the mentioned detections and previous upper limits (Perez-Garcia et al., GCN 40430; Lipunov et al., GCN 40432; Brivio et al., GCN 40435; Zhong et al., GCN 40442). The r and i band magnitudes are calibrated against the PS1 catalog and the J band is calibrated with the 2MASS Catalog. All magnitudes are provided in the AB system and are not corrected for Galactic extinction. We thank Michael Schmidt from the Wendelstein Observatory staff for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/40445. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38475] GRB 250512B/EP250512a: SVOM/VT optical fading
by GCN Circulars 12 May '25

12 May '25

TITLE: GCN CIRCULAR NUMBER: 40444 SUBJECT: GRB 250512B/EP250512a: SVOM/VT optical fading DATE: 25/05/12 16:37:10 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, 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), S. D. Vergani (CNRS, Obs. Paris/LUX), P. Maggi (ObAS), Y. N. Ma, D. H. Zhao (NAOC) report on behalf of the SVOM/VT Instrument Team: The analysis with more downlinked X-band data shows that the optical counterpart (Li et al., GCN 40443) of GRB 250512B/EP250512a (Maggi et al., GCN 40439, Zhao et al., GCN 40437) has been fading to about 21.5+/-0.2 (AB) mag in VT_R mag at the mid time of 1.6 hours after the burst, with an effective time of 12*50 seconds. The decay slop is about -1.0 after the peak time (Li et al., GCN 40443). 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/40444. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38474] GRB 250512B/EP250512a：SVOM/VT bright optical counterpart
by GCN Circulars 12 May '25

12 May '25

TITLE: GCN CIRCULAR NUMBER: 40443 SUBJECT: GRB 250512B/EP250512a：SVOM/VT bright optical counterpart DATE: 25/05/12 15:15:31 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, 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), P. Maggi (ObAS), Y. N. Ma, D. H. Zhao(NAOC) report on behalf of the SVOM/VT Instrument Team: GRB 250512B (sb25051203), triggered both by SVOM/Eclairs (Maggi et al., GCN 40439) and Einstein Probe(EP/WXT) (labeled as EP250512a, Zhao et al., GCN 40437), was observed by on-board SVOM/VT after the automatic slew of the satellite. The VT conducted observations in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. With the downlinked X-band data, the optical counterpart was clearly detected within the error box of EP/FXT(Zhao et al., GCN 40437) in both VT_B and VT_R bands. The earliest observation started on 2025-05-12T11:23:21 UTC (i.e. 193 seconds after the SVOM trigger time). The position of the counterpart is RA=215.20368 deg, DEC= -10.10071 deg, which is equivalent to: R.A.=14:20:48.88, DEC.=-10:06:02.56, J2000, Error=0.5 arcseconds The light curves show a brightening with a peak of 19.3+/-0.1 mag in VT_R and 21.0+/-0.2 mag in VT_B at 668 seconds after the burst. The photometry is in the AB system and is not corrected for Galactic extinction. Given the color of VT_B-VT_R~1.7 mag, it might be a low or intermediate redshift GRB (Wang et al., 2020). 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/40443. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38473] EP250511a: Mephisto optical upper limits
by GCN Circulars 12 May '25

12 May '25

TITLE: GCN CIRCULAR NUMBER: 40442 SUBJECT: EP250511a: Mephisto optical upper limits DATE: 25/05/12 14:58:06 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Shiyan Zhong, Jianhui Lian, Xufeng Zhu, Yicheng Jin, Dan Zhu, Guowang Du, Xingzhu Zou, Brajesh Kumar, Yuan Fang, Helong Guo, Yu Pan, Xinlei Chen, Jianghua Zhang, Edoardo P. Lagioia, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team: The field of EP250511a (Lian et al., GCN 40429) was observed with the 1.6-meter Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University, located at Lijiang Observatory. The simultaneous observations in Mephisto u/g/i bands were started from 2025-05-11T13:58:03 (~6 h after the trigger). The field was also simultaneously observed in v/r/z bands, starting from 2025-05-11T14:07:46. In our stacked u/g/i images and the single frame v/z images (r-band image was saturated due to high background of moon light), we did not detect any source at the position reported by Schneider et. al. (GCN 40431) and Li et al. (GCN 40433). The preliminary 3-sigma upper limits (listed below) are consistent with Perez-Garcia et al. (GCN 40430), Lipunov et al. (GCN 40432), and Brivio et al. (GCN 40435). Start_Time (UT) | Band | Exp(s) | LimMag(AB) --------------------|------|--------|------------- 2025-05-11T13:58:03 | u | 180*2 | > 19.965 2025-05-11T14:07:46 | v | 180*1 | > 19.152 2025-03-09T20:07:03 | g | 60+180 | > 19.876 2025-05-11T13:58:02 | i | 180*2 | > 19.810 2025-05-11T14:07:45 | z | 180*1 | > 18.032 ------------------------------------------------------------------------------------------------- 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/40442. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38472] GRB 250507B: GRBAlpha detection
by GCN Circulars 12 May '25

12 May '25

TITLE: GCN CIRCULAR NUMBER: 40441 SUBJECT: GRB 250507B: GRBAlpha detection DATE: 25/05/12 14:46:01 GMT FROM: Andras Pal at Konkoly Observatory <apal(a)szofi.net> A. Pal (Konkoly Observatory), M. Dafcikova, J. Ripa, N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Duriskova, M. Kolar, L. Szakszonova, J.-P. Breuer, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal, A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner Research Center/Eotvos U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J. Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration. We report a detection of a likely short-duration GRB 250507B by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract). The event was also observed by Wind/Konus at the trigger time 2025-05-07 09:31:29.176 UTC. The GRBAlpha detection was confirmed at the peak time 2025-05-07 09:31:33.1 UTC. The T90 duration measured by GRBAlpha is 1.5 s and the overall significance during T90 reaches 13 sigma. The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB250507B_GCN.pdf All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/ GRBAlpha, launched on 2021 March 22, is a demonstration mission for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~50 keV to ~1000 keV. To increase the duty cycle and the downlink rate, the upgrade of the on-board data acquisition software stack is in progress. The ground segment is also supported by the radio amateur community and it takes advantage of the SatNOGS network for increased data downlink volume. View this GCN Circular online at https://gcn.nasa.gov/circulars/40441. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38471] GRB 250506A: GRBAlpha detection
by GCN Circulars 12 May '25

12 May '25

TITLE: GCN CIRCULAR NUMBER: 40440 SUBJECT: GRB 250506A: GRBAlpha detection DATE: 25/05/12 14:45:14 GMT FROM: Andras Pal at Konkoly Observatory <apal(a)szofi.net> A. Pal (Konkoly Observatory), M. Dafcikova, J. Ripa, N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Duriskova, M. Kolar, L. Szakszonova, J.-P. Breuer, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal, A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner Research Center/Eotvos U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J. Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration. The long-duration GRB 250506A (Fermi/GBM detection: GCN 40355; SVOM/GRM and ECLAIRs detection: GCN 40358; GECAM-B detection: GCN 40396) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract). The detection was confirmed at the peak time 2025-05-06 02:23:56.5 UTC. The T90 duration measured by GRBAlpha is 41 s and the overall significance during T90 reaches 22 sigma. The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB250506A_GCN.pdf All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/ GRBAlpha, launched on 2021 March 22, is a demonstration mission for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~50 keV to ~1000 keV. To increase the duty cycle and the downlink rate, the upgrade of the on-board data acquisition software stack is in progress. The ground segment is also supported by the radio amateur community and it takes advantage of the SatNOGS network for increased data downlink volume. View this GCN Circular online at https://gcn.nasa.gov/circulars/40440. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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