TITLE:   GCN CIRCULAR
NUMBER:  15555
SUBJECT: GRB 131127A: RATIR Rejection of High-z Candidate
DATE:    13/11/29 20:57:31 GMT
FROM:    Nat Butler at UC berkeley  <natxbutler@gmail.com>

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 again 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 29.09 to 2013/11 29.17 UTC
(40.06 to 41.98 hours after the BAT trigger), obtaining a total of 1.42
hours exposure in the r and i bands and 0.60 hours exposure in the Z, Y, J,
and H bands.

For the red source 3.3" away from the center of the XRT positions (Butler
et al., GCN 15525), in comparison with 2MASS, we obtain:

r > 23.78
i = 22.68 +/- 0.16 (0.20 +/- 0.19)
Z = 22.02 +/- 0.26 (0.17 +/- 0.31)
Y = 21.31 +/- 0.24 (0.09 +/- 0.28)
J = 21.26 +/- 0.29 (0.23 +/- 0.32)
H = 20.55 +/- 0.24 (-0.33 +/- 0.31)

The change in magnitude relative to the observations on the previous night
are given in the parentheses.  There is slight (~<1-sigma) evidence for a
fade in most bands, but the shallowness ~t^(-0.2) of the fade is not
expected for a GRB afterglow.  We conclude, as did Im et al. (GCN 15548),
that this source is not the afterglow of GRB 131127A.

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