TITLE:   GCN CIRCULAR
NUMBER:  43938
SUBJECT: GRB 260211A: late-time NOT i-band observations consistent with archival flux
DATE:    26/03/07 10:55:59 GMT
FROM:    Gregory Corcoran  at University College Dublin  <gregory.corcoran@ucdconnect.ie>

G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), S. Bijavara Seshashayana (NOT and Malmo Univ.) report on behalf of a larger collaboration:

We observed the optical counterpart (Li et al., GCN 43748) of GRB 260211A (Gotz et al., GCN 43705; Hamburg, GCN 43713) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC instrument. Observations (3x300 s) were conducted in the SDSS i band, in order to reduce the effect of the large Galactic extinction towards this line of sight (A_V = 2.1 mag). Our image quality was unfortunately degraded by poor seeing (2.1").

The optical counterpart is detected in our images (mid time 23.1 days after the SVOM trigger). We measure a magnitude i = 22.5 +/- 0.2 AB, calibrated against nearby objects from the Pan-STARRS catalog, and not corrected for Galactic extinction.

The source is also detected in archival imaging from the DELVE survey (Drlica-Wagner et al., 2022, doi:10.3847/1538-4365/ac78eb), for which we find a consistent magnitude to within 0.2 mag. Imagine subtraction between the two data sets yields an upper limit of i > 22.9 for any excess component at the afterglow location.

Li et al. (GCN 43923) report a rebrightening of this source between 2.7 and 19.4 days after trigger, possibly suggesting the emergence of a SN. Our data cannot confirm this trend, though the different filters and the large extinction may introduce a systematic difference.