[vsnet-grb-info 20468] GRB 180329B: RATIR Optical Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22564
SUBJECT: GRB 180329B: RATIR Optical Observations
DATE:    18/03/30 06:41:22 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan at astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC),
William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J.
Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz
(UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey
Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki
Toy (UMD) report:

We observed the field of GRB 180329B (Racusin et al., GCN 22558) with
the Reionization and Transients Infrared Camera (RATIR; www.ratir.org)
on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico
Nacional on Sierra San Pedro Mártir from 2018/03 30.13 to 2018/03 30.18
UTC (12.92 to 14.22 hours after the BAT trigger), obtaining a total of
0.96 hours exposure in the r and i bands.

For a source within the Swift-XRT error circle, in comparison with the
USNO-B1 catalog, we obtain the following detections:

 r	= 20.29 +/- 0.09
 i	= 20.32 +/- 0.10

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

The source has faded in r at the 4-sigma level when compared to the
earlier NOT observation of Perley et al. (GCN 22562).

We thank the staff of the Observatorio Astronómico Nacional in San Pedro
Mártir.