TITLE: GCN CIRCULAR NUMBER: 20601 SUBJECT: GRB 170202A: SQUEAN Observation (2nd night) DATE: 17/02/04 11:15:37 GMT FROM: Myungshin Im at Seoul Nat U Myungshin Im, Yongjung Kim, & Joonho Kim (CEOU/SNU) We continued the observation of the GRB 170202A afterglow with the SQUEAN instrument on the 2.1m Otto Struve telescope at the McDonald Observatory, Texas. The 2nd night observation started at 2017-02-04 09:45:52 UT, ​ ​or about 39.3 hours after the BAT alert. The afterglow shows the following preliminary magnitude based on the photometry calibration using SDSS stars in the vicinity. Filter Mag (AB) Mag_err Exp.time Start-time (UT) r 21.8 0.15 180s x 10 09:45:52​