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

[vsnet-grb-info 38537] GRB 250520A: J-band observations with WINTER
by GCN Circulars 20 May '25

20 May '25

TITLE: GCN CIRCULAR NUMBER: 40505 SUBJECT: GRB 250520A: J-band observations with WINTER DATE: 25/05/20 18:00:54 GMT FROM: Geoffrey Mo at MIT <gmo(a)mit.edu> Geoffrey Mo (MIT), Tomas Ahumada (Caltech), Benjamin Schneider (LAM), Viraj Karambelkar (Caltech), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of GRB 250520A (Eyles-Ferris et al., GCN 40491; SVOM/GRM Team, GCN 40495; … [View More]

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[vsnet-grb-info 38536] GRB 250520A: Gemini-South optical observations
by GCN Circulars 20 May '25

20 May '25

TITLE: GCN CIRCULAR NUMBER: 40504 SUBJECT: GRB 250520A: Gemini-South optical observations DATE: 25/05/20 16:07:09 GMT FROM: Jillian Rastinejad at Northwestern Univ. <jillianrastinejad2024(a)u.northwestern.edu> Jillian Rastinejad, Wen-fai Fong, and Charlie Kilpatrick (Northwestern) report on behalf of a larger collaboration: We observed the location of the short-duration GRB 250520A (Eyles-Ferris et al., GCN 40491) with the Gemini Multi-Object Spectrograph (GMOS) mounted on … [View More]Gemini-South under Program GS-2025A-Q-112 (PI: Fong). We obtained 15x120-sec imaging in i-band starting at 2025-05-20 03:45:39.2 UT (1.06 hrs post-burst), at a median airmass of 1.8 and seeing of 0.7''. We detect a clear source coincident with the candidate optical counterpart discovered by SVOM (Xin et al., GCN 40500) that is within the enhanced XRT localization (Goad et al., GCN 40494). Calibrated to Pan-STARRS DR2 (Flewelling et al., 2020, ApJS, 251, 7), we measure a magnitude for this source of i = 22.4 +/- 0.2 AB mag. This value does not include a correction for Galactic extinction, which is significant (A_V = 2.1 mag; Schlafly and Finkbeiner 2011, ApJ, 737, 103). The brightness of this source is consistent with reported upper limits (Brivio et al. GCN 40502, Pereyra et al., GCN 40499, Becerra et al. GCN 40498, Kumar et al. GCN 40493). Correcting our measurement and the value reported by SVOM at 2.14 hours post-burst (VT_R = 23.2 +/- 0.2 mag; Xin et al., GCN 40500) for Galactic extinction, we find no clear evidence for fading within the uncertainties. At or very close to the position of the SVOM and Gemini source, there appears to be a faint source in i- and z-band archival PS1 imaging (Flewelling et al., 2020, ApJS, 251, 7), though more precise astrometry is needed to determine their relative positions. However, forced photometry near the position of the SVOM source (Xin et al., GCN 40500) in the PS1 images yields 3-sigma upper limits on underlying emission of i > 22.2 and z > 21.7 AB mag, uncorrected for extinction. Given that the PS1 i-band limit is shallower than our source magnitude, it is difficult to tell whether the faint source was pre-existing or is the afterglow of GRB 250520A. Further observations are planned to assess the variability of the source and others in the field. We thank the Gemini staff for the rapid scheduling and execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/40504. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L… [View Less]

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[vsnet-grb-info 38535] GRB 250520A: Swift-XRT refined Analysis
by GCN Circulars 20 May '25

20 May '25

TITLE: GCN CIRCULAR NUMBER: 40503 SUBJECT: GRB 250520A: Swift-XRT refined Analysis DATE: 25/05/20 14:29:54 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), M.A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), B. Sbarufatti (INAF-OAB) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.7 ks … [View More]

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[vsnet-grb-info 38534] GRB 250520A: REM optical/NIR early observations
by GCN Circulars 20 May '25

20 May '25

TITLE: GCN CIRCULAR NUMBER: 40502 SUBJECT: GRB 250520A: REM optical/NIR early observations DATE: 25/05/20 11:04:40 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) report on behalf of the REM team: We observed the field of GRB 250520A detected by Swift/BAT (Eyles-Ferris et al., GCN 40491), SVOM/GRM (SVOM/GRM team, GCN 40495), and AstroSat (Tembhurnikar et al., GCN 40497) with the REM 60 cm … [View More]

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[vsnet-grb-info 38533] GRB 250520B: Fermi GBM Final Real-time Localization
by GCN Circulars 20 May '25

20 May '25

TITLE: GCN CIRCULAR NUMBER: 40501 SUBJECT: GRB 250520B: Fermi GBM Final Real-time Localization DATE: 25/05/20 10:46:39 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 10:36:02 UT on 20 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250520B (trigger 769430167.408886 / 250520442). The on-ground calculated location, using the Fermi GBM trigger data, is RA =… [View More]

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[vsnet-grb-info 38532] GRB 250520A：SVOM/VT optical candidate
by GCN Circulars 20 May '25

20 May '25

TITLE: GCN CIRCULAR NUMBER: 40500 SUBJECT: GRB 250520A：SVOM/VT optical candidate DATE: 25/05/20 10:45:18 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) report on behalf of the SVOM/VT team: SVOM performed a Target of Opportunity observation of GRB 250520A detected by Swift/BAT (Eyles-Ferris et al., … [View More]

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[vsnet-grb-info 38531] GRB 250520A: COLIBRÍ optical upper limit
by GCN Circulars 20 May '25

20 May '25

TITLE: GCN CIRCULAR NUMBER: 40499 SUBJECT: GRB 250520A: COLIBRÍ optical upper limit DATE: 25/05/20 10:34:25 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Margarita Pereyra (UNAM), Stéphane Basa (UAR Pytheas), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire … [View More]

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[vsnet-grb-info 38530] GRB 250520A: DDOTI Optical Upper Limit
by GCN Circulars 20 May '25

20 May '25

TITLE: GCN CIRCULAR NUMBER: 40498 SUBJECT: GRB 250520A: DDOTI Optical Upper Limit DATE: 25/05/20 10:26:32 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 … [View More]

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[vsnet-grb-info 38529] GRB 250520A: AstroSat CZTI detection of a short burst
by GCN Circulars 20 May '25

20 May '25

TITLE: GCN CIRCULAR NUMBER: 40497 SUBJECT: GRB 250520A: AstroSat CZTI detection of a short burst DATE: 25/05/20 09:34:08 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 … [View More]

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[vsnet-grb-info 38528] GRB 250516B: GRBAlpha detection
by GCN Circulars 20 May '25

20 May '25

TITLE: GCN CIRCULAR NUMBER: 40496 SUBJECT: GRB 250516B: GRBAlpha detection DATE: 25/05/20 08:49:07 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), 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, … [View More]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 250516B (GECAM-B detection: GCN 40469; NuSTAR detection: GCN 40484; Insight-HXMT/HE detection: GCN 40489; Wind/Konus detection trigger at 2025-05-16 06:31:32.766 UTC) 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 2025-05-16 06:31:54.3 UTC. The T90 duration measured by GRBAlpha is 40 s and the overall significance during T90 reaches 83 sigma. The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB250516B_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/40496. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L… [View Less]

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