[vsnet-grb-info 18204] GRB 160703A: MITSuME Akeno Optical Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19652
SUBJECT: GRB 160703A: MITSuME Akeno Optical Observations 
DATE:    16/07/04 17:56:53 GMT
FROM:    Taketoshi Yoshii at Tokyo Tech  <yoshii.t.ac at m.titech.ac.jp>

Y. Tachibana,  Y. Saito, Y. Muraki, Y. Ono, T. Fujiwara, T. Yoshii, K. Saisho,
H. Ohuchi, Y. Yano, S. Harita, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:

We report the optical follow-up observations of GRB 160703A (S. B. Cenko et al., GCN Circular #19645) with a tricolor camera (g', Rc, and Ic) attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan.

The observation started at 2016-07-03 12:10:54 UT (~30 sec after the burst).
Although the first eight frames (each exposure time is 30 sec) are covered by thick clouds, we detected a bright optical transient source in the refined BAT error circle (A. Y. Lien et al., GCN Circular #19648)  ~5 min after the trigger.
The position of the counterpart is
RA(J2000) = 19h 09m 40.1s
Dec(J2000) = +36d 55' 08.1"
with an uncertainty of ~0.5 arc sec. 

Nearby the optical transient, a known source N2JN062852 (RA, Dec = 19h 09m 40.212s, +36d 55' 06.9816$B!I(B)
catalogued in GSC2.3 is located. 
In the photometric analysis, we ignored the contamination from the nearby source because its 
flux is substantially lower (Fmag = 20.27) comparing with the optical counterpart.
The results were shown below:

  T0+[min]    MID-UT    T-EXP[sec]    g$B!G(B    g$B!G(B_err    Rc    Rc_err    Ic    Ic_err
----------------------------------------------------------------------------------------------------------------------
   5.82          12:15:54        30          15.46    0.06        14.59    0.06        14.25    0.09
   58.35        13:08:26      3900        18.18    0.05        17.08    0.04        16.87    0.06
   330.52      15:40:36      7680        19.13    0.06        17.96    0.05        17.61    0.06
----------------------------------------------------------------------------------------------------------------------
  T0+ : Elapsed time after the burst
  T-EXP: Total Exposure time

We used GSC2.3 catalog for flux calibration.
Further analysis is ongoing.