TITLE:   GCN CIRCULAR
NUMBER:  32326
SUBJECT: GRB220412A: VIRT Optical Upper Limit
DATE:    22/07/05 17:53:31 GMT
FROM:    Priyadarshini Gokuldass at U. of the Virgin Islands  <priyadass.94@gmail.com>

K. Noonan (UVI), P. Gokuldass (Florida Institute of Technology), N. Orange
(OrangeWave Innovative Science, LLC), K. Smith (UVI), D. Morris (UVI)
report:

We observed the field of GRB220412A (N. J. Klingler et al., GCN 31881) with
the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the
Virgin Islands' Etelman Observatory on 04-13-2022 starting at 00:11:58.73
UT (T+17.30 hrs). We performed a series of exposures in the R filter with a
total exposure of 4000 s. The weather conditions were partly cloudy during
the hours of observation with an average airmass of 1.25.

We find no new source within the enhanced XRT position error circle (P. A.
Evans et al., 31887) and report the following 5-sigma upper limit:

T_mid            ||Exposure     ||Filter      ||Limit

T+ 18.2 hrs    ||4000s          ||R            ||>20.8

The limit is estimated from comparison to nearby USNO B1 stars and is not
corrected for Galactic extinction. The VIRT is still in the commissioning
phase.

We acknowledge financial support from NASA MUREP MIRO award 80NSSC21M0001, NASA
EPSCoR award 80NSSC19M0060, and NSF EiR award 1901296.This message can be
cited.