[vsnet-grb-info 21106] GRB 180904A: RATIR Optical and NIR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23204
SUBJECT: GRB 180904A: RATIR Optical and NIR Observations
DATE:    18/09/05 15:49:17 GMT
FROM:    Nat Butler at Az State U  <natbutler at asu.edu>

Nat Butler (ASU), Alan M. Watson (UNAM), 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 180904A (D'Ai, et al., GCN 23194) 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 2018/09 5.13 to 2018/09 5.32 UTC (5.66 to
10.26 hours after the BAT trigger), obtaining a total of 2.91 hours
exposure in the r and i bands and 1.33 hours exposure in the Z, Y, J, and H
bands.

Within the XRT error circle (Osborne, et al., GCN 23196), we detect the
source reported by Malesani, et al. (GCN 23195) at a consistent brightness
level.  In comparison with the USNO-B1 and 2MASS catalogs, we obtain the
following detections and upper limit (3-sigma):

 r = 22.61 +/- 0.08
 i = 22.06 +/- 0.05
 Z = 22.13 +/- 0.16
 Y = 21.64 +/- 0.18
 J = 21.72 +/- 0.21
 H > 21.86

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

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