[vsnet-grb-info 13146] GRB 130427A: Continued RATIR Optical and NIR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14483
SUBJECT: GRB 130427A: Continued RATIR Optical and NIR Observations
DATE:    13/04/28 05:46:39 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 (UCSC),
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 130427A (Maselli, et al., GCN 14448)
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 2013/04 28.14 to 2013/04 28.20 UTC
(19.62 to 20.99 hours after the BAT trigger), obtaining a total of 1.07
hours exposure in the r' and i' bands and 0.45 hours exposure in the Z, Y,
J, and H bands.

We continue to detect the optical/NIR afterglow (Elenin et al; GCN 14450)
in all bands.  In comparison with SDSS DR8 and 2MASS, we find:

  r'    17.68 +/- 0.01
  i'    17.52 +/- 0.01
  Z     17.26 +/- 0.04
  Y     17.12 +/- 0.02
  J     17.21 +/- 0.02
  H     17.01 +/- 0.03

These magnitudes are in the AB system and not corrected for Galactic
extinction in the direction of the GRB.  Uncertaints are 1-sigma.  The
source has faded by about 3 magnitudes in all bands as compared to our
measurements last night (Butler et al. 2013; GCN 14459).

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