TITLE:   GCN CIRCULAR
NUMBER:  20598
SUBJECT: GRB 170202A: Etelman Observatory optical observations
DATE:    17/02/03 22:24:51 GMT
FROM:    Bruce Gendre at ASDC  <bruce.gendre@gmail.com>

B. Gendre (UVI), N. Orange (OrangeWave Innovative Science, LLC), D. 
Morris (UVI), A. Cucchiara (UVI), D. Drost (UVI), T. Giblin (USAF
Academy), J. Hakkila (College of Charleston), A. Klotz (IRAP), J. Neff 
(NSF), D. Smith (UVI), J. Staff (UVI), P. Thierry (Auragne Observatory), 
R. Watlington (UVI), and L. Wentlent (UVI) report:

We observed the field of GRB 170202A (Racusin et al. GCN 20575) with the 
0.5m Virgin Island Robotic Telescope (VIRT) on February the 3rd,
starting at 3:16 UT (8.8 hours after the trigger), until 10:30 UT. We 
performed a series of exposures in the clear filter. The weather 
conditions were variable with a typical estimated seeing of 2".

We detected the afterglow observed by UVOT (Racusin et al., GCN 20575) 
on a combined image (spanning times from 10h to 11.92h after the 
trigger). Its magnitude, estimated by comparison to nearby USNO-B1 
stars, was R = 20.8 +/- 0.3.

Further analysis is in progress.

Magnitudes have not been corrected for Galactic extinction. The VIRT is 
still in its commissioning phase.

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