GCN Circular 15970

Owen Littlejohns (ASU), Antonino Cucchiara (ORAU/GSFC), 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), Eleonora Troja (GSFC), Enrico Ramirez-Ruiz (UCSC),
Jos� A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes�s Gonz�lez
(UNAM), Carlos Rom�n-Z��iga (UNAM), Neil Gehrels (GSFC), and
Harvey Moseley (GSFC) report:

We observed the field of GRB 140311B (Racusin, et al., GCN 15945
Not found
 
 
)
with the Reionization and Transients Infrared Camera
(RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the
Observatorio Astron�mico Nacional on Sierra San Pedro M�rtir from
2014/03 12.37 to 2014/03 12.52 UTC (11.52 to 15.25 hours after the
BAT trigger), obtaining a total of 2.84 hours exposure in the r and
i bands and 1.19 hours exposure in the Z and Y bands.

For a source within the Swift-XRT error circle, in comparison with
the SDSS DR9 and 2MASS, we obtain the following upper limits (3-sigma):

  r     > 23.99
  i     > 23.82
  Z     > 22.85
  Y     > 22.26

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB. In comparison to the earlier
detection of the optical afterglow (Xu, et al., GCN 15949
Not found
 
 
) the GRB has
faded. A power-law temporal decay with an index of alpha = -0.94 or
steeper is required for our r-band upper limit to be consistent with the
earlier detection.

We thank the staff of the Observatorio Astron�mico Nacional in San Pedro
M�rtir.