TITLE: GCN CIRCULAR NUMBER: 39343 SUBJECT: EP250215a / GRB 250215A : GTC redshift z = 4.61 DATE: 25/02/16 11:58:30 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia ajct@iaa.es
R. Sanchez-Ramirez, A. J. Castro-Tirado, M. D. Caballero-Garcia, S. Guziy, G. Garcia-Segura, I. Perez-Garcia and S.-Y. Wu (IAA-CSIC), M. Gritsevich (Univ. of Helsinki), D. Xu (NOAC), A. Martin-Carrillo (UCD), Y.-D. Hu (GXU), S.B. Pandey (UPSO), S. Geier and A. Cabrera-Lavers (GTC), on behalf of a larger collaboration, report:
Following the detection of EP250215a/GRB250215A by EP/WXT (Wang et al. GCNC 39329), INTEGRAL/SPI-ACS (Barria et al. GCNC 39331), AstroSat CZTI (Tembhurnikar et al. GCNC 39334) SVOM/GRM (Zheng et al., GCN 39335) and Fermi/GBM (Scotton and Meegan, GCNC 39342), we triggered the 10.4m GTC in Observatorio del Roque de Los Muchachos (La Palma, Spain) in order to get an spectrum of the proposed optical afterglow detected by NOT (Liu et al., GCNC 39330, Malesani et al., GCNC 39341), SVOM/VT (Xie et al., GCN 39333) and Gemini-South (Malesani et al., GCNC 39339).
Data was gathered starting on Feb 16, 2:27 UT (i.e. 23.9 hr post- burst), consisting of 4x1000s spectra with the R1000R grism, covering the range 5,200-10,000. Based on a preliminary reduction, we detect a prominent Ly-alpha absoption at ~6820A, plus several metal features interpreted as being due to SiII, CII, SiIV and CIV at a redshift of z = 4.61, wich we proposed to be the redshift of EP250215a/GRB250215A.
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