[vsnet-grb-info 14211] GRB 131127A: RATIR Optical and NIR Observations, High-z Candidate

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15525
SUBJECT: GRB 131127A: RATIR Optical and NIR Observations, High-z Candidate
DATE:    13/11/28 08:41:53 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), Chris Klein (UCB), Ori Fox (UCB),
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(ORAU/GSFC), 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), and
Harvey Moseley (GSFC) report:

We observed the field of GRB 131127A (Markwardt, et al., GCN 15516) 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 2013/11 28.11 to 2013/11 28.26 UTC (16.42
to 19.94 hours after the BAT trigger), obtaining a total of 2.49 hours
exposure in the r and i bands and 1.04 hours exposure in the Z, Y, J, and H
bands.

We do not detect any sources within the Enhanced Swift-XRT error circle
(Evans et al., GCN 15520), in comparison with 2MASS, we obtain the
following upper limits (3-sigma):

  r > 24.19
  i > 23.53
  Z > 22.78
  Y > 22.16
  J > 22.04
  H > 21.48

However, we do detect a red source just outside (3.3" away from the center)
of the XRT position, at a position RA, DEC = 332.731227 , 36.609171 (J2000,
+/- 0.5").  We measure:

  r = 24.21 +/- 0.35
  i = 22.48 +/- 0.11
  Z = 21.85 +/- 0.16
  Y = 21.22 +/- 0.15
  J = 21.03 +/- 0.14
  H = 20.88 +/- 0.20

The faint flux in r band relative to the redder bands could be due to IGM
attenuation at high redshift, z ~ 5.  We cannot confirm fading of this
source.  Further observations of this source are encouraged.

The magnitudes above are in the AB system and are not corrected for
Galactic extinction, E[B-V]~0.1, in the direction of the GRB.

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