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GCN Circular 19820

Subject
GRB 160816A: RATIR Optical and NIR Afterglow Confirmation
Date
2016-08-18T12:35:04Z (8 years ago)
From
Eleonora Troja at GSFC <eleonora.troja@nasa.gov>
Eleonora Troja (GSFC), Nat Butler (ASU), Alan M. Watson (UNAM),
Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G.
Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC),
Josh Bloom (UCB), Antonino Cucchiara (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), Harvey Moseley (GSFC), John
Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:

We observed the field of GRB 160816A (Mailyan, et al., GCN 19804;
Racusin, et al., GCN 19802) 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 2016/08 18.17 to 2016/08 18.47 UTC (1.44 to
1.72 days after the GBM trigger), obtaining a total of 2.47 hours
exposure in the r and i bands and 1.03 hours exposure in the Z,
Y, J, and H bands.

For the source reported in Troja, et al. (GCN 19809), in comparison
with the USNO-B1 and 2MASS catalogs, we obtain the following
detections and upper limit (3-sigma):


    r    22.74 +/- 0.15
    i    22.40 +/- 0.12
    Z    22.19 +/- 0.19
    Y    22.18 +/- 0.25
    J    > 22.32
    H    21.20 +/- 0.18

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

The source intensity decreased significantly between our two epochs,
corresponding to fading with power-law index alpha~-1.3 referenced to
the burst trigger. This confirms that the candidate reported by
Guidorzi, et al. (GCN 19808) and Troja et al. (GCN 19809) is the GRB
afterglow.

Deep imaging of the GRB location reveals additional optical sources
within the XRT localization (Kennea et al., GCN 19806), however none of
them have faded.

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