GCN Circular 19602

Alan M. Watson (UNAM), Eleonora Troja (GSFC), 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 (GSFC/STScI), Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), Jos�� A. de Diego (UNAM), Leonid Georgiev (UNAM),
Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Neil Gehrels (GSFC),
Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and
Vicki Toy (UMD) report:

We observed the field of the Fermi LAT GRB 160625B (Dirirsa, et al., GCN
19580
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 2016/06 27.36 to
2016/06 27.47 UTC (33.89 to 36.56 hours after the BAT trigger),
obtaining a total of 1.73 hours exposure in the r and i bands and 0.73
hours exposure in the Z, Y, J, and H bands.

We detect the afterglow reported by Troja et al. (GCN Circ. 19588
Not found
 
 
) and,
in comparison with the USNO-B1 and 2MASS catalogs, obtain the following
magnitudes:

  r	= 19.63 +/- 0.01
  i	= 19.52 +/- 0.01
  Z	= 19.34 +/- 0.02
  Y	= 19.17 +/- 0.02
  J	= 19.11 +/- 0.02
  H	= 18.98 +/- 0.03

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

The afterglow has faded by about 1.20 magnitude in all bands compared to
our earlier epoch, confirming the fading seen during the first epoch.
The fading is consistent with a temporal index of -0.90.

More observations are planned.

We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.

[GCN OPS NOTE(27jun16): Per author's request, the GRB name in the Title
was changed from "A" to "B".  The name in the text was/is correct.]