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GCN Circular 23239

GRB 180914B: Optical counterpart observation from OAJ
2018-09-16T08:58:16Z (6 years ago)
Antonio de Ugarte Postigo at IAA-CSIC <>
A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), L. Izzo (HETH/IAA-CSIC), 
D.A. Kann (HETH/IAA-CSIC), C.C. Thoene (HETH/IAA-CSIC), H. Vazquez 
Ramio (CEFCA), N. Maicas (CEFCA) and V. Tilve (CEFCA) report:

We have observed the field of 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). The observation consisted of 12x300s i-band exposures, each 
covering the complete LAT error box. The exposures started at 22:03:46 UT of 
the 15th September, 27.68 hr after the burst. The counterpart identified by Zheng 
& Filippenko (GCN 23237) and Troja et al. (GCN 23238) is well detected in the 
individual images. Photometry of the first epoch, as compared with SDSS 
reference stars yields i(AB)=18.84+/-0.03.

Comparing with the RATIR photometry (roja et al. GCN 23238), our photometry 
implies a decay rate of alpha ~ -1.9 (where F_nu ~ t^alpha), indicating that the 
afterglow has possibly entered a post-jet-break regime evolution.
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