TITLE:   GCN CIRCULAR
NUMBER:  15877
SUBJECT: GRB 140102A: TAOS early optical afterglow detection
DATE:    14/02/23 01:09:24 GMT
FROM:    Ying-Tung Chen at ASIAA/TAOS  <ytchen@asiaa.sinica.edu.tw>

Y. T. Chen, S. K. King, C. Y. Wen, K. Y. Huang, S. Y. Wang, M. Lehner and
TAOS team

We observed the field of the Swift GRB 140102A (Hagen et al., GCN 15653)
with TAOS 0.5-m telescope of Lulin observatory (Taiwan) starting on Jan., 2
(UT) 21:19:49, i.e., 2.2 minutes after the trigger.

We detected the fading optical afterglow at the time between few early
optical afterglow observations (Xu et al., GCN 15655; Guziy et al., GCN
15685; Yoshii et al. GCN 15778). The details of the photometry were listed
below.

DATE_T_START          T0+   T_EXP   MAG
(UT)                  sec   sec     R

2014-01-02 21:19:49   132   49      15.3+/-0.11
2014-01-02 21:20:38   181   49      15.7+/-0.15
2014-01-02 21:21:27   230   49      16.1+/-0.26
2014-01-02 21:22:16   279   49      (Upper Limit = 16.2)

The R-band magnitude of nearby USNOB1 stars have been used for calibration.
We note that a special filter (5000-7200 A) was used in TAOS telescopes.