TITLE: GCN CIRCULAR NUMBER: 38373 SUBJECT: GRB 241128A: NOT optical observations DATE: 24/11/28 22:59:25 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University d.malesani@astro.ru.nl
B. Gompertz (Birmingham), D. B. Malesani (DAWN/NBI and Radboud Univ.), L. Izzo (INAF/OACN, DARK/NBI), J. H. Terwel (NOT and TCD) report on behalf of a larger collaboration:
We observed the field of GRB 241128A (Brivio et al., GCN 38367; Page, GCN 38368) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were carried out at large airmass and under a poor seeing of 2.5". A total of 3x300 s and 5x200 s were secured in the SDSS r and z bands, respectively.
From a preliminary reduction of the data, the optical afterglow (Hu et al., GCN 38371; Izzo & Malesani, GCN 38372) is well detected in our images. We measure
r = 19.52 +- 0.03 AB on Nov 28.80 UT (2.95 hr after the GRB); z = 19.03 +- 0.05 AB on Nov 28.81 UT (3.25 hr after the GRB).
Both magnitudes are calibrated against nearby objects from the Pan-STARRS catalog.
We note a discrepancy in the r-band magnitude compared to the nearly simultaneous measurement by Izzo & Malesani (GCN 38372), which we are unable to account for at the present time.
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