GCN Circular 21187
Subject
GRB 170531B: SMARTS optical/IR observations
Event
Date
2017-06-01T18:25:15Z (9 years ago)
From
Bethany Cobb at GWU <bcobb@gwu.edu>
B. E. Cobb (GWU), reports:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 170531B
(GCN 21171, Evans et al.) at two epochs (with mid-exposure times
of 2017-06-01 04:22 UT & 08:19 UT). For each epoch, several
dithered images were obtained with total summed exposure times
amounting to 36 minutes in I and 30 minutes in J.
No source is detected at the position of the X-ray/optical
afterglow (GCN 21175, Osborne et al.; GCN 21174, Pozanenko et al.;
GCN 21177, de Ugarte Postigo et al.; GCN 21178, Schady & Kruehler;
GCN 21179, Tyurina et al.) to the approximate 3-sigma limiting
magnitudes listed below:
mid-exposure
time post-burst
(hours) I-limit J-limit
6.33056 >20.8 >18.5
10.27333 >21.2 >18.7
(Optical photometry is calibrated against USNO-B1.0 stars
and IR photometry is calibrated against 2MASS stars in the
field.)