[vsnet-grb-info 13307] GRB 130514A: RATIR Optical and NIR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14643
SUBJECT: GRB 130514A: RATIR Optical and NIR Observations 
DATE:    13/05/14 18:13:06 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan at astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), 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 observed the field of GRB 130514A (Sonbas et al., GCN 14632) 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 2013/05 14.30 to 2013/05 14.46 UTC (4.7 minutes 
to 3.90 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.

For a source within the Swift-XRT error circle, in comparison with USNO-B1
and 2MASS, we obtain the following upper limits (3-sigma):

  r' > 23.51
  i' > 23.39
  Z > 22.07
  Y > 21.62
  J > 21.43
  H > 21.13

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

Kann et al. (GCN Circular 14634) report a source with r ≈ 20.0 and i ≈
19.2 in images taken from 2 to 6 minutes after the BAT trigger. Perley
(GCN Circular 14633) reports a marginal detection in r and z in images
taken from 12 to 27 minutes after the BAT trigger. We began exposing on
this field less than 5 minutes after the BAT trigger, but due to the
high airmass of almost 5 and poor transparency on the south-eastern
horizon, our first useful images are not until about 17 minutes after
the trigger. The evolution of our 3-sigma limits is:

  i' > 21.72 at 0.49 hours after the trigger
  i' > 22.48 at 1.14 hours
  i' > 23.00 at 1.59 hours
  i' > 23.17 at 2.02 hours
  i' > 23.24 at 2.60 hours
  i' > 23.30 at 3.34 hours
  i' > 23.39 at 3.90 hours
  
If we extrapolate the Kann et al. measurement of i ≈ 19.2 at 4 minutes
according to t^-1, we would expect to have detected their source in our
observations out to 2 hours. That we did not suggests that light curve
fell faster than this. We note that quick-look light curve for Swift-XRT
falls by almost three orders of magnitude between about 3 minutes and 20
minutes, which may be consistent with a rapid optical decay.

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