TITLE:   GCN CIRCULAR
NUMBER:  25949
SUBJECT: GRB 191004B: Optical Afterglow Detection with LCO
DATE:    19/10/04 23:55:39 GMT
FROM:    Robert Strausbaugh at U. of the Virgin Islands  <robert.strausbaugh@uvi.edu>

R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:

We observed Swift GRB 191004B (Palmer et al., GCN 25947) with
the LCO 1-m Sinistro instrument on September 4, from 21:50 to 22:07 UT
(corresponding to 0.11 to 0.4 hours from the GRB trigger time)
with the Bessel R filter.

We performed a series of 5x180s exposures, and we detect a source not present in either USNO-B1.0 or 2MASS surveys consistent with the optical afterglow location (Palmer et al., GCN 25947
) with the following magnitude:

R = 18.07 +/- 0.02

This flux is calibrated against several USNO-B1.0 objects near the GRB location but is not corrected for Galactic Extinction.

These observations were possible thanks to the USVI NASA-EPSCoR
Research Infrastructure Development (RID) grant NNX16AL44A.