Skip to main content
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 25971

GRB 191004A: Optical Detection with LCO
2019-10-07T16:14:13Z (5 years ago)
Robert Strausbaugh at U. of the Virgin Islands <>
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 191004A (Barthelmy et al., GCN 25945) with
the LCO 1-m Sinistro instrument on September 4, from 20:12 to 20:47 UT
(corresponding to 1.70 to 2.28 hours from the GRB trigger time)
with the Bessel R and I filters.

We performed a series of 10x180s exposures in each band.  We do not detect a significant source in individual frames, but we do  detect a source in co-added frames that is not present in either USNO-B1.0 or 2MASS surveys and is consistent with the optical afterglow location (Evans et al., GCN 25950) with the following magnitudes:

R = 22.89 +/- 0.10
I = 21.00 +/- 0.09

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.
Looking for U.S. government information and services? Visit