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GCN Circular 18917

Subject
GRB 160121A: 1.8m MOA optical afterglow detection
Date
2016-01-21T22:19:41Z (8 years ago)
From
Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>
S. R. Oates, J. C. Tello (IAA-CSIC Granada), P. Tristram (Mt. John Univ. Observatory),
I. Bond (Massey Univ.),  S. Takahiro (Osaka Univ.), P. Yock (Univ. of Auckland) and
A. J. Castro-Tirado (IAA-CSIC & ISA-UMA) report on behalf of a larger collaboration:

We observed the field of GRB 160121A (Hagen  et al., GCN 18912) with the 1.8m MOA-II
telescope at Mt John University Observatory in New Zealand. A series of 60s exposures
were taken with the R-band filter beginning 4.38 min (13:55:0 UT on 21-01-2016) after
the Swift trigger 671231.

We detect a single source at the edge of the Swift-XRT error circle (Hagen  et al., GCN 18912),
which we propose is the afterglow, at coordinates:

RA (J2000.0) = 07:16:21.16
Dec (J2000.0) = -23:35:31.6

with an error of around 0.5".

In the first exposure, ~292s after the trigger, we measure R ~19.7+\-0.2.
The light curve appears to increase slightly in brightness, plateauing
around 500s with a magnitude ~19. The light curve begins to decay around
1200s after the trigger.

Magnitudes and upper limits are calibrated against USNO-B1 catalogue and
are not corrected for the significant Galactic extinction corresponding to a
reddening of E_B-V = 0.53 mag (Schlafly & Finkbeiner 2011).
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