TITLE:   GCN CIRCULAR
NUMBER:  27035
SUBJECT: GRB 200131A: Tautenburg observations
DATE:    20/02/11 15:39:37 GMT
FROM:    Sylvio Klose at TLS Tautenburg  <klose@tls-tautenburg.de>

B. Stecklum, S. Klose, A. Nicuesa Guelbenzu, and C. Hoegner (all Tautenburg) 
report:

We observed the field of GRB 200131A (T0=22:41:15 UT; Sbarufatti et al., GCN 
26953) with the Tautenburg 1.34m Schmidt telescope equipped with the TAUKAM 6k 
x 6k CCD camera and the wide V-band filter (VB). The transmission curve of this 
filter closely follows the Gaia GBP filter.

Based on several Gaia DR2 stars in the field within 1 arcmin radius about the 
afterglow position, we measure for the optical transient (Lipunov et al., GCN 
26954; Butler et al., GCN 26957; Strausbaugh et al., GCN 26959; Gokuldass et 
al., GCN 26960; Kuin et al., GCN 26962; Pozanenko et al., GCN 26964, 26965; 
Watson et al., GCN 26977) the following Vega magnitudes:

mean time t = Jan 31, 23:12:15 UT; t-T0 = 00h 31m 00s;  VB = 18.00 +/- 0.10
mean time t = Feb 01, 20:41:47 UT; t-T0 = 22h 00m 32s;  VB = 21.85 +/- 0.30.