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[vsnet-grb-info 38296] EP250427a / GRB 250427A: LCO optical counterpart detection
by GCN Circulars 27 Apr '25

27 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40267 SUBJECT: EP250427a / GRB 250427A: LCO optical counterpart detection DATE: 25/04/27 16:30:09 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), and A. López-Oramas (IAC and ULL) Following the detection of the fast X-ray transient EP250427a (Wang et al., GCN circ. 40257), detected also by Fermi-GBM, GRB … [View More]

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[vsnet-grb-info 38295] EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
by GCN Circulars 27 Apr '25

27 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40266 SUBJECT: EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520 DATE: 25/04/27 15:39:47 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> A. Saccardi (CEA/Irfu), V. Abril-Melgarejo (LUX-Paris Obs.), Z. P. Zhu (NAOC), V. D’Elia (ASI/SSDC), A. J. Levan (Radboud and Warwick), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), B. Schneider (LAM), N. R. Tanvir (Leicester), A. L. … [View More]Thakur (INAF/IAPS), S. D. Vergani (LUX-Paris Obs.), K. Wiersema (Hertfordshire), D. Xu (NAOC), report on behalf of the Stargate collaboration: We observed the optical counterpart (Perez-Garcia et al., GCN 40259; Liu et al., GCN 40260; Becerra et al., GCN 40261; Brivio et al., GCN 40264) of EP250427a / GRB 250427A (Wang et al., GCN 40257; Ravasio et al., GCN 40262) using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-21,000 AA, and consist of 2 exposures of 600 s each. The observation mid time was 2025 Apr 27.394 UT (5.80 hr after the GRB). In a 30-s image taken in the r band at a mid time of 5.61 hr after the trigger, we measure a magnitude r = 18.40 +- 0.02 AB, calibrated against nearby stars from the Pan-STARRS catalog. In a preliminary reduction of the spectra, we clearly observe a bright continuum over the entire covered wavelength range, detected at high S/N. The sightline is rich with intervening absorption systems, in particular C IV absorbers (1548,1550 doublet) are detected at z = 1.146, 1.222, 1.231, 1.405, 1.407, 1.518, and 1.520. The highest-redshift system is only securely detected in C IV and Si IV (at both z = 1.518 and 1.520). There is a possible indication of Lyman alpha absorption at the very blue end of the spectrum, with very low column density (much less than a DLA). The system at z = 1.405/1.407 is on the other hand the strongest and has detection in many species at both high and low ionization, including Si II, C II, Si IV, C IV, Fe II, Al II, Al III, Mg II and Mg I, as well as a rich velocity structure. No emission lines are visible at any of the above mentioned redshifts. Our data are therefore in good agreement with the results and the redshift value z = 1.520 already reported by Chornock et al. (GCN 40265) using the Keck telescope. We acknowledge expert and efficient support from the observing staff at Paranal, in particular Boris Haeussler, Francesca Lucertini, Rodrigo Romero, and Elisa Garro. View this GCN Circular online at https://gcn.nasa.gov/circulars/40266. --- 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 38294] EP250427A/GRB250427A: Keck/LRIS redshift
by GCN Circulars 27 Apr '25

27 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40265 SUBJECT: EP250427A/GRB250427A: Keck/LRIS redshift DATE: 25/04/27 14:11:22 GMT FROM: Ryan Chornock at UC Berkeley <chornock(a)berkeley.edu> R.Chornock, E. Hammerstein, X. Guo (UC Berkeley) report: We observed the optical afterglow (GCNs 40258, 40259, 40260, 40261, 40263, 40264) of EP250427a (GCN 40257)/GRB 250427a (GCN 40262) using the Low-Resolution Imaging Spectrometer on the Keck-I telescope at a mean time of 12:36UT on 2025 Apr 27. … [View More]

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[vsnet-grb-info 38293] EP250427a: REM optical/NIR afterglow detection
by GCN Circulars 27 Apr '25

27 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40264 SUBJECT: EP250427a: REM optical/NIR afterglow detection DATE: 25/04/27 13:23:16 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 EP250427a detected by EP/WXT (Wang et al., GCN 40257), also seen by Fermi/GBM (Ravasio et al., GCN 40262) with the REM 60 cm robotic telescope located at the ESO observatory of … [View More]

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[vsnet-grb-info 38292] GRB 250424A: LCO optical observation
by GCN Circulars 27 Apr '25

27 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40263 SUBJECT: GRB 250424A: LCO optical observation DATE: 25/04/27 13:05:34 GMT FROM: ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994(a)gmail.com> Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES), Rahul Gupta (NASA GSFC) on behalf of a larger collaboration. We observed the field of the GRB 250424A triggered by Swift (Cenko et al., GCN 40224), … [View More]

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[vsnet-grb-info 38291] GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
by GCN Circulars 27 Apr '25

27 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40262 SUBJECT: GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection DATE: 25/04/27 12:34:44 GMT FROM: mariaedvige.ravasio(a)ru.nl M. E. Ravasio (Radboud Univ.), E. Burns (LSU), Adam Goldstein (USRA) and P.G. Jonker (Radboud Univ.) report on behalf of the Fermi-GBM Team: Fermi-GBM had full spatial and temporal coverage of the transient EP250427a detected by EP-WXT (Wang et al., GCN 40257). There was no Fermi-GBM onboard trigger around the EP starting … [View More]

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[vsnet-grb-info 38290] EP250427A: COLIBRÍ Optical Detection
by GCN Circulars 27 Apr '25

27 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40261 SUBJECT: EP250427A: COLIBRÍ Optical Detection DATE: 25/04/27 10:34:16 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Rosa L. Becerra (U Roma), Benjamin Schneider (LAM), Jean-Luc Atteia (IRAP), Margarita Pereyra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA/IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Gré… [View More]

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[vsnet-grb-info 38289] EP250427a: TRT optical counterpart detection
by GCN Circulars 27 Apr '25

27 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40260 SUBJECT: EP250427a: TRT optical counterpart detection DATE: 25/04/27 10:13:08 GMT FROM: Dong Xu at NAOC/CAS <dxu(a)nao.cas.cn> X. Liu, Z.P. Zhu, S.Q. Jiang (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), S.Y. Fu (HUST), J. An, Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang, D. Xu (NAOC) report on behalf of a large collaboration: We observed the field of EP250427a (Wang et al., GCN 40257), using the 0.7-m telescope of the Thai Robotic … [View More]

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[vsnet-grb-info 38288] EP 250427a: BOOTES-7 optical afterglow candidate
by GCN Circulars 27 Apr '25

27 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40259 SUBJECT: EP 250427a: BOOTES-7 optical afterglow candidate DATE: 25/04/27 10:11:14 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es> I. Perez-Garcia, A. J. Castro-Tirado, E. Fernandez-Garcia, S.-Y. Wu, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy (IAA-CSIC), C. Perez del Pulgar (Univ. de Malaga), G. Garcia-Segura (Inst. de Astronomia, UNAM), M. Gritsevich (Univ. of Helsinki), D. R. Xiong (Yunnan … [View More]

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[vsnet-grb-info 38287] EP250427a: Global MASTER-Net observations report
by GCN Circulars 27 Apr '25

27 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40258 SUBJECT: EP250427a: Global MASTER-Net observations report DATE: 25/04/27 10:09:47 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.… [View More]

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