TITLE:   GCN CIRCULAR
NUMBER:  14178
SUBJECT: GRB 130131A: RATIR optical and infrared upper limits
DATE:    13/02/01 23:07:03 GMT
FROM:    Ori Fox at UCB  <ofox@berkeley.edu>

Ori Fox (UCB), Nat Butler (ASU), Alan M. Watson (UNAM), Alexander 
Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB),
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC),
Eleonora Troja (GSFC), Enrico Ramirez-Ruiz (UCSC), JosÈ A. de
Diego (UNAM), Leonid Georgiev (UNAM), Jes˙s Gonz·lez (UNAM),
Carlos Rom·n-Z˙Òiga (UNAM), Neil Gehrels (GSFC), and Harvey
Moseley (GSFC) report:

Under good weather conditions, we observed the field of GRB 130131A 
(Grupe, et al., GCN 14156) with the Reionization and Transients Infrared 
Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at 
the Observatorio AstronÛmico Nacional on Sierra San Pedro M·rtir. An 
extremely red (K=16.4, J=19.4) afterglow candidate was detected by 
Tanvir, et al. (GCN 14157). We obtained approximately 2.83 hrs (ri) and 
1.07 hrs (ZYJH) of data from 2013 February 1.25 to 2023 February 1.42 
UTC (16.0 to 20.0 hrs after the BAT trigger)

We detect no source within the XRT error circle (Evans et al; GCN 14160) 
or at the position of the UKIRT source (GCN 14157). In comparison with 
SDSS DR8 and 2MASS, we derive the following upper limits (3-sigma) in 
the AB magnitude system:

r' > 23.8
i' > 23.3
Z > 22.2
Y > 21.8
J > 21.9
H > 21.5

The limits are consistent with the suggested fading of at least 2 mag in 
K-band (GCN 14175) measured at 20.5 hours.

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

We thank the staff of the Observatorio AstronÛmico Nacional in San
Pedro M·rtir.

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