TITLE: GCN CIRCULAR NUMBER: 39073 SUBJECT: GRB 250129A: NOT optical observations and redshift confirmation DATE: 25/01/29 07:32:00 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University d.malesani@astro.ru.nl
Luca Izzo (INAF/OACn and DARK/NBI), Daniele B. Malesani (DAWN/NBI), Kasper E. Heintz (DAWN/NBI), Benjamin Gompertz (Birmingham), Antonio de Ugarte Postigo (CNRS, LAM and OCA), Benjamin N. Hauptmann (NOT, DTU Space ), Arthur M. Kadela (NOT, NBI), report on behalf of a larger collaboration:
We observed the optical counterpart (Francile, GCN 39065; Belkin et al., GCN 39072) of GRB 250129A (Beardmore et al., GCN 39066) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC imager. In a 300-s exposure with mid time 2025 Jan 29.222 UT (34.3 min after trigger), the counterpart is well detected with an AB magnitude r = 16.71 +- 0.02 (calibrated against nearby stars from Pan-STARRS). We measure the following coordinates (J2000):
RA = 13:14:42.40 Dec = +05:01:50.2
A sequence of three 1200-s spectra was secured using grism #4. Bright continuum is detected across the whole wavelength range. A number of absorption lines are detected, which, among others, we identify as H I, Si II, O I, C II, Si IV, C IV, Al II, Fe II, Mg II, all at a common redshift z = 2.15.
Our result is consistent with the value already measured by Schneider et al. (GCN 39071).
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