GCN Circular 21968

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), Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey
Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki
Toy (UMD) report:

We observed the field of GRB 171004A (Cenko et al., GCN Circ. 21966
Not found
 
 
)
with the Reionization and Transients Infrared Camera (RATIR;
www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio
Astron��mico Nacional on Sierra San Pedro M��rtir from 2017/10 4.45 to
2017/10 4.45 to 2017/10 4.52 UTC (2.97 to 4.45 hours after the BAT
trigger), obtaining a total of 1.07 hours exposure in the r and i bands
and 0.45 hours exposure in the Z, Y, J, and H bands.

We detect two sources within the Swift-XRT error circle. One is a
cataloged SDSS source. The other is at 09:16:40.66 +52:41:30.4 (J2000
+/- 0.5 arcsec) and, in comparison with the SDSS DR9 and 2MASS catalogs,
has

  r	= 21.91 +/- 0.11
  i	= 21.32 +/- 0.07
  Z	= 21.13 +/- 0.15
  Y	= 20.43 +/- 0.12
  J	= 20.45 +/- 0.15
  H	= 19.88 +/- 0.13

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 Astron��mico Nacional in San Pedro
M��rtir.