[vsnet-grb-info 18154] GRB 160625A: RATIR Optical and NIR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19602
SUBJECT: GRB 160625A: RATIR Optical and NIR Observations 
DATE:    16/06/27 14:12:33 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan at astro.unam.mx>

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), José A. de Diego (UNAM), Leonid Georgiev (UNAM),
Jesús González (UNAM), Carlos Román-Zúñiga (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) 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 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) 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 Astronómico Nacional in San Pedro
Mártir.