TITLE: GCN CIRCULAR NUMBER: 39893 SUBJECT: GRB 250327B: NOT spectroscopic redshift z = 3.035 DATE: 25/03/28 00:17:12 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University d.malesani@astro.ru.nl
D. B. Malesani (DAWN/NBI and Radboud), B. Schneider (LAM), A. Martin-Carrillo (UCD), J. T. Palmerio (CEA/Irfu), G. Corcoran (UCD), B. Gompertz (Birmingham), A. de Ugarte Postigo (LAM), T. Pursimo (NOT), report on behalf of a larger collaboration:
We observed the optical afterglow (Moskvitin et al., GCN 39889; Xin et al., GCN 39890; O'Neill et al., GCN 39891) of the SVOM GRB 250327B (Bouchet et al., GCN 39888) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC spectrograph. The covered wavelength range (grism #4) is 3200 - 9600 AA.
In an image of 2x180 s in the r-band, starting on 2025 Mar. 27 at 22:48:21 (1.7 hr after the trigger), we measure r = 17.13 +/- 0.04 (AB). The photometric calibration was performed using nearby stars from the Pan-STARRS catalog and the magnitude is not corrected for Galactic extinction.
Based on a preliminary reduction, the spectrum shows bright continuum all the way to the red, with a strong trough around 4900 AA and a break blueward of it, typical of DLA absorption and Lyman forest. From detection of multiple absorption features, which we interpret as due to, among others, Si II, C II, S IV, C IV, Fe II, Al II, we measure a redshift z = 3.035.
View this GCN Circular online at https://gcn.nasa.gov/circulars/39893. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...