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GCN Circular 21394

Subject
GRB 170728B: Optical observations at Crni Vrh
Date
2017-07-30T20:13:20Z (7 years ago)
From
Bojan Dintinjana at OCV <bojan.dintinjana@fmf.uni-lj.si>
B. Dintinjana and H. Mikuz on behalf of PIKA observing program at Crni 
Vrh Observatory:

We observed the afterglow of GRB 170728B (Cenko et al., GCN Circ. 21371) 
with 60 cm Cichocki robotic telescope at Crni Vrh Observatory, Slovenia. 
The series of twenty-six 60 second exposures with Rc filter started at 
23:04:41UT, 81 seconds after the burst. We confirm optical afterglow at 
coordinates reported by D�Avanzo et al. (GCN Circ. 21372, 21373).

Photometry results are given in table below. The table contains the mid 
time of exposure in MJD, time since the Swift GRB detection to the 
middle of exposure in seconds, Rc magnitude and photometric error. The 
magnitudes are derived using comparison stars from the APASS catalog. 
The 3-sigma limiting magnitude in Rc filter is around magnitude 20.2 � 0.2.
The light curve of the GRB 170728B:
http://www.observatorij.org/vstars/GRB170728B/GRB170728B.png

MJD t-T0 Rc err
(s) (mag) (mag)
-------------------------------------
57962.961574 81 17.410 0.04
57962.962407 153 17.867 0.05
57962.963252 226 18.077 0.06
57962.964097 299 18.412 0.08
57962.964931 371 18.638 0.10
57962.965775 444 18.830 0.11
57962.966620 517 18.827 0.11
57962.967454 589 19.123 0.14
57962.968299 662 19.054 0.13
57962.969144 735 19.142 0.14
57962.969977 807 19.181 0.15
57962.970822 880 19.217 0.16
57962.971667 953 19.714 0.26
57962.972512 1026 19.505 0.22
57962.973345 1098 19.507 0.20
57962.974190 1171 19.586 0.23
57962.975023 1243 19.674 0.27
57962.975868 1316 19.456 0.23
57962.976713 1389 19.981 0.35
57962.977558 1462 19.734 0.25
57962.978391 1534 20.227 0.42
57962.979236 1607 19.736 0.25
57962.980081 1680 19.878 0.32
57962.980926 1753 20.200 0.38
57962.981759 1825 19.519 0.21
57962.982604 1898 19.913 0.31
-------------------------------------
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