GCN Circular 18095
Subject
GRB 150727A: Continued RATIR Optical Observations - Fading
Date
2015-07-29T20:03:54Z (9 years ago)
From
Alan M. Watson at Instituto de Astronomia UNAM <alan@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 (ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU),
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 150727A (Cenko et al., GCN 18076) 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 2015/07 29.15 to 2015/07 29.19
UTC (32.64 to 33.50 hours after the BAT trigger), obtaining a total of
0.70 hours exposure in the r, i, and z bands.
We no longer detect the source seen on the previous night (Watson et
al., GCN 18089). In comparison with the USNO-B1 and 2MASS catalogs, we
obtain the following upper limits (3-sigma):
r > 22.27
i > 22.61
z > 19.11
These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.
The source has faded by at least 1 magnitude in both r and i. We
therefore suggest that it it corresponds to the afterglow.
We thank the staff of the Observatorio Astron�mico Nacional in San Pedro
M�rtir.