TITLE:   GCN CIRCULAR
NUMBER:  23255
SUBJECT: GRB 180914B: OAJ multi-color follow-up
DATE:    18/09/19 18:32:38 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

L. Izzo, M. Blazek (both HETH/IAA-CSIC), A. de Ugarte Postigo 
(HETH/IAA-CSIC, DARK/NBI), D. A. Kann, C. C. Thoene, K. Bensch (all 
HETH/IAA-CSIC), R. Martone (U. Ferrara), W. Schoenell (Federal U. of Rio 
Grande do Sul), H. Vazquez Radio, M. C. Diaz-Martin, and S. 
Rodriguez-Llano (all OAJ) report:

We have continued to monitor GRB 180914B (Ursi et al., GCN 23226; 
Verrecchia et al., GCN 23231; Bissaldi et al. GCN 23232; D'Ai et al., 
GCN 23236) with the 0.8m T80 telescope of the Javalambre Astrophysical 
Observatory (Teruel, Spain). Observations consisted of a series of 3x300 
s griz exposures, starting at 22:47:49 UT  on September 16 (2.18 days 
after the GRB detection). The afterglow is clearly detected in all 
stacked images. We measure the following magnitudes (AB system):

g' = 20.73 +/- 0.05 mag at 2.1875 days,
r' = 20.27 +/- 0.08 mag at 2.2003 days,
i' = 19.94 +/- 0.07 mag at 2.2260 days,
z' = 19.62 +/- 0.07 mag at 2.2413 days,

as compared to nearby PANSTARRS stars.