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

[vsnet-grb-info 38410] GRB 250507A: refined SVOM/MXT data analysis
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40381 SUBJECT: GRB 250507A: refined SVOM/MXT data analysis DATE: 25/05/07 14:04:48 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> P. Maggi (ObAS), D. Götz (CEA), H. Goto (Kanazawa University/CEA), M. Moita (CEA), C. Plasse (CEA), F. Robinet (IJCLab), C. Van Hove (IJCLab) report of behalf of the SVOM/MXT Team: GRB 250507A (Wang et al. GCN 40374) was observed by SVOM/MXT after an automatic SVOM slew, starting at T0 = 2025-05-07T06:40:59.951 (374s after trigger time Tb). MXT observed during the first orbit for 2.1 ks effective exposure. Using the full X-band dataset, we measure a complex light curve with two flares of 150 to 200s duration, followed by a rapid decay with a temporal index of -4.1+/-0.2 at times t+T0>400s. The source is no longer detected at t+T0>1200s and hence we restricted the analysis below to the first 20 min of data. The X-ray source located at R.A., Dec 183.066, -23.5928 degrees: R.A. (J2000) = 12h12m15.8s Dec. (J2000) = -23d35m34.12s with a 90% C.L. radius of 37 arcseconds (including 35 arcseconds systematic error added in quadrature) The spectrum is modelled with an absorbed power law. Using the average spectrum of the first 1200s of MXT data, the absorption column NH is 5.2 +/-0.5 x 1e22 /cm2 (90% C.L. uncertainties) and a rather soft photon index of 3.6 +/- 0.2. The time-averaged observed flux is 4.5 x 1e-10 ergs/cm^2/s but the count rate varies by a factor 100 between peak at t+T0=160s and t+T0=1200s. Follow-up observations at other wavelengths are encouraged. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. MXT was developed jointly by CEA, CNES, University of Leicester, IJCLab and MPE. The SVOM point of contact for this burst is:z iqi.wang(a)st.gxu.edu.cn. Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/40381. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38409] GRB 250507A: REM optical/NIR observations
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40380 SUBJECT: GRB 250507A: REM optical/NIR observations DATE: 25/05/07 12:09:00 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB), M. De Pasquale (Univ. of Messina) report on behalf of the REM team: We observed the field of GRB 250507A detected by SVOM/ECLAIRs (Wang et al., GCN 40374) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, and K bands, started on 2025 May 07 at 06:45:31 UT (i.e. about 11 minutes after the burst), and lasted for about 2 hours. From preliminary inspection, we do not detect any possible counterpart inside the SVOM/MXT error circle down to the following 3sigma limits: r > 19.3 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 33 minutes after the trigger; H > 16.0 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 32 minutes after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/40380. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38408] GRB 250507A: SVOM/VT optical upper limit
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40379 SUBJECT: GRB 250507A: SVOM/VT optical upper limit DATE: 25/05/07 11:01:12 GMT FROM: Liping Xin at NAOC, SVOM <xlp(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. T. Palmerio (CEA), Z. Q. Wang (GXU), Y. F. Liang (PMO), W. K. Zheng (UCB) report on behalf of the SVOM/VT instrument team. After the trigger by SVOM/ECLAIRs at 2025-05-07T06:34:45 UT (SVOM burst-id sb25050703), SVOM performed an automatic slew on the burst. SVOM/VT began observing the field at 260 seconds after the SVOM trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With the downlinked X band data, no any uncataloged sources are detected in single or stacked imags within the errorbox of Eclairs or MXT (Wang et al., GCN 40374), compared to the Legacy survey. The 3 sigma upper limits are derived below: Mid_time | Exposure time | Band | Upper limit (AB) 550 sec | 10*50 sec | VT_B | 22.8 550 sec | 10*50 sec | VT_R | 22.7 1225 sec | 38*50 sec | VT_B | 23.2 1225 sec | 38*50 sec | VT_R | 23.1 This results are consistent with the report (J.-G. Ducoin et al. GCN 40376). Given the bright X-ray counterpart (Wang et al., GCN 40374), and the deep optical upper limit at the early phase of the burst, near infrared observations are encouraged to investigate the nature of the burst. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. View this GCN Circular online at https://gcn.nasa.gov/circulars/40379. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38407] GRB 250506A: Swift-XRT observations
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40378 SUBJECT: GRB 250506A: Swift-XRT observations DATE: 25/05/07 09:35:26 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), M. A. Williams (PSU), S. Dichiara (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/MXT-detected burst GRB 250506A at the revised position given in GCN Circ. 40364, collecting 2.9 ks of Photon Counting (PC) mode data between T0+63.2 ks and T0+70.1 ks. One uncatalogued X-ray source has been detected, it is below the RASS limit and shows no definitive signs of fading. Therefore, at the present time we cannot confirm this as the afterglow. Details of this source are given below: Source 1: RA (J2000.0): 219.28269 = 14:37:7.85 Dec (J2000.0): +28.87835 = +28:52:42.1 Error: 2.6 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: 0.0586 +/- 0.0052 ct s^-1 Distance: 84 arcsec from SVOM/MXT position. Flux: (2.16 +/- 0.19)e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV) 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/ToO_GRBs/00021828. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40378. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38406] Fermi-LAT Gamma-ray Observations of IceCube-250506A
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40377 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-250506A DATE: 25/05/07 09:11:45 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg), S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC250506A neutrino event (GCN 40369) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 2025-05-06 14:14:12.09 UTC (T0) with J2000 position RA = 116.50 (+0.59, -0.57) deg, Decl. = 35.32 (+0.48, -0.43) deg 90% PSF containment. No cataloged gamma-ray sources are found within the 90% IC250506A localization error (The Fourth Fermi-LAT catalog, 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5 sigma) new excess emission (> 100 MeV) within the IC250506A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC250506A best-fit position, the >100 MeV flux upper limit (95% confidence) is <2.97e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <6.91e-09(<2.61e-08) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this region will continue. For this analysis, the Fermi-LAT contact person is L. Pfeiffer (leonard.pfeiffer at uni-wuerzburg.de). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/40377. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38405] GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40376 SUBJECT: GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 25/05/07 08:57:04 GMT FROM: J.-G. Ducoin at CPPM <ducoin(a)cppm.in2p3.fr> Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Francis Fortin (IRAP), 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), Z. Wang (GXU) and Y. Liang (PMO): We imaged the field of the SVOM GRB 250507A (Wang et al., GCN 40374) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-05-07 06:36:04 to 07:34:42 UTC (from 79 to 3597 seconds after the trigger) and obtained 2560 seconds of exposure in the i filter. 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 and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the MXT source position (Wang et al., GCN 40374) down to the following 5-sigma limit (AB): i > 22.3 mag Further observations 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/40376. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38404] EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40375 SUBJECT: EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032 DATE: 25/05/07 07:38:27 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Sun, M. H. Zhang, H. Q. Cheng (NAO, CAS), Y. J. Zhang (THU), W. Yuan (NAO, CAS) report on behalf of the Einstein Probe team: We report on the detection of a new X-ray outburst of the low-mass X-ray binary (LMXB) MAXI J1957+032 by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The burst triggered EP-WXT (ID: 01709175213) at 2025-05-06T21:07:59 (UTC). The source light curve lasted for 74 seconds before the observation was interrupted by the follow-up observation. The WXT position of the source, inferred from the onground analysis, is R.A. = 299.150 deg, DEC = 3.444 deg (J2000) with an uncertainty of 2.8 arcmin in radius (90% C.L. statistical and systematic). The averaged WXT spectrum in 0.5-4 keV can be fitted by an absorbed power law model with a photon index of 1.82 (-0.56, +0.62) when fixing the column density at 1.7 x 10^21 cm^-2 (Sánchez et al. 2017). The average unabsorbed 0.5-4 keV flux is 7.6 (-1.7,+2.2) x 10^-10 erg/cm^2/s. Following the WXT trigger, a follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. The FXT observation started at 2025-05-06T21:08:30 (UTC), around 30 seconds after the trigger. The analysis of the data, with an exposure of 1.6 ks, reveals a detection of an X-ray source at RA = 299.1636 deg, Dec = 3.4449 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). This position is consistent with the known LMXB MAXI J1957+032 (also named as IGR J19566+0326), confirming the WXT detection as the outburst of this X-ray source. The averaged FXT spectrum in 0.5-10 keV can be fitted by an absorbed power law model with a photon index of 1.85 (-/+ 0.02) when fixing the column density at 1.7 x 10^21 cm^-2. The average unabsorbed 0.5-10 keV flux is 9.1 (-/+ 0.1) x 10^-10 erg/cm^2/s, which is consistent with the flux detected by the WXT. These parameters derived are at the 1-sigma confidence level. The previous outburst of MAXI J1957+032 happened at the end of September 2016 and lasted for around 4 days. Its X-ray flux was approximately 7 x 10^-13 erg/cm^2/s in 2022 before the outburst, inferred from the Swift/XRT observation. We thus suggest that MAXI J1957+032 has entered a new outburst phase. Contact transient advocate (TA) for MAXI J1957+032 is H. Sun (hsun(a)nao.cas.cn) and please contact the TA for information regarding the EP observation of this source. Reference: Sánchez et al. 2017, MNRAS, 468, 564 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/40375. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38403] GRB 250507A: SVOM detection of a long burst
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40374 SUBJECT: GRB 250507A: SVOM detection of a long burst DATE: 25/05/07 07:23:04 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Z. Wang (GXU), Y. Liang (PMO), H. Yang, O. Godet (IRAP), P. Maggi (ObAS), D. Götz (CEA), L Xin (NAOC) report on behalf of the SVOM mission team: SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250507A (SVOM burst-id sb25050703) starting at 2025-05-07T06:34:45.17 UTC (Tb). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected by the Count-Rate Trigger (CRT) and Image Trigger (IMT). A sequence of 10 alerts was produced. IMT provided the alert with the best signal-to-noise-ratio (SNR) of 10.65 in the 8-120 keV energy band over a time window of 40.96 seconds starting at Tb. The localization of the best alert is R.A., Dec. 182.990, -23.615 degrees: R.A. (J2000) = 12h11m57.6s Dec. (J2000) = -23h36m54s with a 90% confidence level (C.L.) radius of 7.5 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. MXT began observing the field after the slew, starting at 2025-05-07T06:41:02 i.e. 377 s after Tb. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec 183.074, -23.598 degrees: R.A. (J2000) = 12h12m17.76s Dec. (J2000) = -23d35m52.8s with a 90% C.L. radius of 30 arcseconds (including 25 arcseconds systematic error added in quadrature). This location is 4.7’ from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the recorded images will be published in a future circular gathering information on the follow-up of the SVOM optical instruments. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. The Burst Advocate (BA) on shift for this burst is Ziqi Wang: ziqi.wang(a)st.gxu.edu.cn. Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/40374. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38402] GRB 250506A: Mephisto optical upper limits
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40373 SUBJECT: GRB 250506A: Mephisto optical upper limits DATE: 25/05/07 02:43:57 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Dezi Liu, Ziwei Li, Tao Wang, Shuang Lin, Xiangru Qian, Guowang Du, Xingzhu Zou, Yu Pan, Xinlei Chen, Xufeng Zhu, Helong Guo, Yuan Fang, Jinghua Zhang, Chenxu Liu, Edoardo Lagioia, Brajesh Kumar, Jianhui Lian, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team: We conducted simultaneous multi-band photometric observations of the GRB 250506A (SVOM burst-id sb25050601) detected by SVOM/ECLAIRs (Wang et al., GCN 40358) and by Fermi (Fermi GBM team, GCN 40362) with the Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University, located at the Lijiang Observatory. Simultaneous u, g, and i band observations were initiated at 14:08:39 UTC on 2025-05-06 (~12.5 hours after the trigger). We obtained four exposures of 300 seconds each in ugi bands. No optical counterpart was detected at the refined position reported by the SVOM team (Maggi et al., GCN 40364). The preliminary 3-sigma upper limits are below: | UT Start | T-T0 (hr) | Band | Exp | LimMag (AB) | |-------------------|-----------|------|--------|-------------| | 2025/5/6 14:08:40 | 12.53 | u | 4x300s | > 21.82 | | 2025/5/6 14:08:40 | 12.53 | g | 4x300s | > 22.42 | | 2025/5/6 14:08:39 | 12.53 | i | 4x300s | > 21.84 | These limits are consistent with previously reported non-detections (Xin et al., GCN 40366; Ferro et al., GCN 40363; Liu et al., GCN 40360; Postigo et al., GCN 40359). ---------------------------------------------------------- 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/40373. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38401] GRB 250504A: EIRSAT-1 GMOD Detection
by GCN Circulars 06 May '25

06 May '25

TITLE: GCN CIRCULAR NUMBER: 40372 SUBJECT: GRB 250504A: EIRSAT-1 GMOD Detection DATE: 25/05/06 21:03:59 GMT FROM: Padraig McDermott at University College Dublin <padraig.mcdermott(a)ucdconnect.ie> P. McDermott, D. Murphy, C. McKenna, C. de Barra, A. Ulyanov, G. Finneran, G. Corcoran, L. Cotter, A. Empey, J. Fisher, F. Gibson Kiely, J. Thompson, D. McKeown, A. Martin-Carrillo, L. Hanlon, S. McBreen, on behalf of the EIRSAT-1 team: EIRSAT-1 reports the detection of the long gamma-ray burst GRB 250504A by the Gamma-ray Module (GMOD) instrument, which was also detected by Fermi GBM (GCN [40342](https://gcn.nasa.gov/circulars/40342) and [40346](https://gcn.nasa.gov/circulars/40346)) and Swift-BAT (GCN [40343](https://gcn.nasa.gov/circulars/40343)) The GMOD detection was made starting at 2025-05-04 23:25:56.5 UTC. The GMOD light curve for GRB 250405A, with 1.2s binning, shows multiple peaks consistent with the detections by Fermi GBM and Swift-BAT. The spacecraft location at time of detection was 9.886º S, 164.567° E and an altitude of 386 km. The light curve for this event as measured by GMOD can be found here: https://grb.eirsat1.ie/250504A/250504A_LC_onboard_preliminary.png EIRSAT-1 is Ireland’s first satellite (Doyle et al. Proceedings of the 4th SSEA, 2022). It is a 2U CubeSat and carries onboard a number of experiments including the Gamma-Ray Module (GMOD), a novel, compact, gamma-ray detector (Murphy et al, Experimental Astronomy, 53, 961–990, 2022). GMOD consists of a 25 mm × 25 mm × 40 mm Cerium Bromide scintillator coupled to SiPMs and is designed to detect gamma-ray bursts in the ~ 60 keV - 1.5 MeV range. EIRSAT-1 was developed in University College Dublin with support from ESA’s Fly Your Satellite! programme and was launched on 1st December 2023. View this GCN Circular online at https://gcn.nasa.gov/circulars/40372. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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