TITLE:   GCN CIRCULAR
NUMBER:  20594
SUBJECT: GRB 170202A: SQUEAN Observation
DATE:    17/02/03 13:25:13 GMT
FROM:    Myungshin Im at Seoul Nat U  <mim@astro.snu.ac.kr>

Myungshin Im, Yongjung Kim, & Joonho Kim (CEOU/SNU)

We observed the field of GRB 170202A (Racusin et al., GCN 20575) using
the SQUEAN instrument on the 2.1m Otto Struve telescope at the McDonald
Observatory, Texas. The observation started at 2017-02-03 10:26:26 UT,
​ ​
or about 16 hours after the BAT alert.

We identify the afterglow at the location of the reported GRB position,
with the following preliminary results based on the photometry calibration
using SDSS stars in the vicinity.

 Filter    Mag (AB)  Mag_err   Exp.time  Start-time (UT)
​    r            21.1       0.08         180s x 3    10:26:26.6​
    i            20.6        0.06         180s x 3    10:36:20.7
    z           20.5        0.10         180s x 3    10:47:15.6

 Further observations are planned.