[vsnet-grb-info 17192] GRB 151027B: RATIR Late-Time Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18543
SUBJECT: GRB 151027B: RATIR Late-Time Upper Limits
DATE:    15/10/31 15:12:21 GMT
FROM:    Nat Butler at UC berkeley  <natxbutler at gmail.com>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI), 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), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:

We observed the field of GRB 151027B (Ukwatta, et al., GCN 18499) 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 2015/10 31.23 to 2015/10 31.52 UTC (78.85 to 85.85 hours after the BAT trigger), obtaining a total of 5.20 hours exposure in the r, i, and z bands.

We no longer detect the optical afterglow (Malesani et al., GCN 18501).  In comparison with the USNO-B1 and 2MASS catalogs, we obtain the following upper limits (3-sigma):

   r > 23.45
   i > 23.39
   z > 18.57

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

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