[vsnet-grb-info 17651] GRB 160225A: RATIR Optical and NIR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19088
SUBJECT: GRB 160225A: RATIR Optical and NIR Observations
DATE:    16/02/26 07:25:27 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 (GSFC/STScI),
Eleonora Troja (GSFC), 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 GRB 160225A (Siegel, et al., GCN 19075) 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 2016/02 26.13 to 2016/02 26.28 UTC (12.72 to
16.34 hours after the BAT trigger), obtaining a total of 2.47 hours
exposure in the r and i bands and 1.04 hours exposure in the Z, Y, J, and H
bands.

We detect the WHT afterglow candidate (Wiersema, et al., GCN 19082), and
find it to have faded.  In comparison with the SDSS DR9 and 2MASS catalogs,
we obtain the following detections and upper limits (3-sigma):

  r > 24.09
  i = 23.03 +/- 0.16
  Z = 22.17 +/- 0.19
  Y > 22.35
  J = 22.06 +/- 0.33
  H > 21.74

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.  The r-band faintness suggests that
this may be a moderate to high-z source.  Fitting Milky Way, LMC, and SMC
Exctinction Laws in Addition to the IGM (see, Littlejohns, et al. 2014), we
find a photo-z of 5.54 (+0.35,-5.11; 90% conf.).  Hence, a high-z solution
is preferred, but a low-z origin is not ruled out.

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