[vsnet-grb-info 13013] GRB 130310A: RATIR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14350
SUBJECT: GRB 130310A: RATIR Observations
DATE:    13/03/28 15:50:17 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), 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 the Fermi-LAT detected GRB 130310A (Guiriec, et
al., GCN 14282) 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.  Data were
taken in the r' and i' channels for a central 9.8 x 7.3 arcmin^2 portion of
the IPN error region (Golenetskii, et al., GCN 14284), centered on RA, DEC
= 141.90061, -17.10809 (J2000),  in 2 epochs, 1.31-1.47 days after the
Fermi trigger and 3.31-3.45 days after the Fermi trigger.  We reach a
limiting magnitude ~24 (AB) in both channels in both epochs.  Data were
captured in the Z, Y, J, and H bands over a larger field (14.8 x 12.5
arcmin^2), reaching a shallower limit (~22 AB).

Of the XRT candidate afterglows (Sbarufatti, et al., GCN 14316), only
source #5 is contained in our images.  We detect that source in both epochs
at a position RA, DEC = 141.881334, -17.147639 (+/-0.5" J2000):

Epoch 1:
  r' = 23.6 +/- 0.1
  i' = 23.6 +/- 0.2

Epoch 2:
  r' = 23.5 +/- 0.1
  i' = 23.3 +/- 0.2

These magnitudes are in the AB system, not corrected for Galactic
extinction in the direction of the GRB, and calibrated relative to USNO-B1.
 We find that source #5 has remained approximately constant in flux over a
2 day period.  It has not faded and is therefore unlikely to be the
afterglow of GRB 130310A.  This source is not detected in the Z, Y, J, or H
bands. We also note that we have searched for additional fading sources
(delta_mag > 0.5) in all bands and have found none.

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