[vsnet-grb-info 17656] GRB 160225A: Continued RATIR Optical and NIR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19093
SUBJECT: GRB 160225A: Continued RATIR Optical and NIR Observations
DATE:    16/02/26 16:52:29 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 26.51 UTC (12.72 to
21.97 hours after the BAT trigger), obtaining a total of 6.38 hours
exposure in the r and i bands and 2.68 hours exposure in the Z, Y, J, and H
bands.

With continued exposure (see, Butler, et al., GCN 19088), we now detect the
WHT afterglow candidate (Wiersema, et al., GCN 19082) in all bands.  In
comparison with the SDSS DR9 and 2MASS catalogs, we find:

 r = 23.84 +/- 0.18
 i = 23.13 +/- 0.11
 Z = 22.71 +/- 0.18
 Y = 22.40 +/- 0.22
 J = 22.44 +/- 0.26
 H = 22.04 +/- 0.26

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

We have fitted our photometry with a power-law source and redshifted Milky
Way, LMC, or SMC extinction laws and IGM extinction (see, Littlejohns, et
al. 2014). The detection in r conclusively rules out solutions with z > 5.
However, there are a range of solutions up to z ~ 4.5.

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