TITLE: GCN CIRCULAR NUMBER: 39896 SUBJECT: GRB 250327B: Las Cumbres optical counterpart detection DATE: 25/03/28 04:43:23 GMT FROM: Manisha Shrestha at University of Arizona mshrestha1@arizona.edu
M. Shrestha (Univ. of Arizona), D. Sand (Univ. of Arizona), K. D. Alexander (Univ. of Arizona), J. Andrews (Gemini), J. Pearson (Univ. of Arizona), N. Smith (Univ. of Arizona), K. Bostroem (Univ. of Arizona), C. Christy (Univ. of Arizona), N. Franz (Univ. of Arizona), D. A. Howell (LCO/UCSB), C. McCully (LCO/UCSB), M. Newsome (LCO/UCSB), J. Farah (LCO/UCSB) report on behalf of a wider Global Supernova Project collaboration:
We observed the field of GRB 250327B (SVOM team, GCN 39888) with the 1-m telescope, starting on 025-03-28T02:38:50.16 UT (60762.11 MJD, ~5.5 hours after the trigger) using the Sinistro instrument in g, r, i bands (exposure of 2×200 s). We clearly detect the optical counterpart as reported in previous circulars ( Moskvitin+ GCN 39889, Xin+ GCN 39890, O’Neill+ GCN 39891, Malesani+ GCN 39893, Lian+ GCN 39894). Preliminary photometric data are as follows:
g = 20.7 +-0.1 r = 19.4 +-0.1 i = 18.8 +- 0.1
These values were calculated with respect to ATLAS-REFCAT2 (Tonry et al. 2018, ApJ 867 105) catalog. They are not corrected for galactic extinction. This source is fading compared to the magnitude reported in Malesani+ GCN 39893.
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