TITLE:   GCN CIRCULAR
NUMBER:  32327
SUBJECT: GRB220408A: VIRT Optical Upper Limit
DATE:    22/07/05 17:55:28 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 GRB220408A (Caputo et al., GCN 31848) with the
0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin
Islands' Etelman Observatory on 04-08-2022 starting at 23:53:07.963 UT
(T+18.7 hrs). We performed a series of exposures in the R filter with a
total exposure of 6180 s. The weather conditions were partly cloudy during
the hours of observation with an average airmass of 1.5.

We detect no new source within the enhanced XRT position error circle (A.P.
Beardmore et al., 31852), consistent with other non-detections  ( Zheng &
Filippenko, GCN 31850; Jiang et al., GCN 31853; Kumar et al., GCN 31857;
and Gregory et al., GCN 31867)  and report the following 5-sigma upper
limit:

T_mid            ||Exposure     ||Filter      ||Limit

T+ 19.5 hrs    ||6180s          ||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.