[vsnet-grb-info 21063] GRB 180818B: 1.5m OSN optical afterglow candidate
GCN Circulars
gcncirc at capella2.gsfc.nasa.gov
Wed Aug 22 06:59:39 JST 2018
TITLE: GCN CIRCULAR
NUMBER: 23161
SUBJECT: GRB 180818B: 1.5m OSN optical afterglow candidate
DATE: 18/08/21 21:58:52 GMT
FROM: Youdong HU at IAA-CSIC, UGR <youdong at iaa.es>
Y.-D. Hu, A. Sota, V. Casanova and A.J. Castro-Tirado (IAA-CSIC
Granada), on behalf of a larger collaboration, report:
We observed the field of the Swift/Fermi burst GRB 180818B (Marshall et
al. GCNC 23149, Veres et al. GCNC 23153), with the 150-cm telescope of
the Observatorio de Sierra Nevada (OSN) near Granada, Spain.
Two I-band observations were taken on Aug 19 and 21 (starting at 03:40
and 04:19 UT respectively, i.e. ~15.2 h and ~63.8 h after trigger) with
total exposure times of 2100s and 1200s respectively. Within the
enhanced Swift/XRT position (Beardmore et al. GCNC 23151), an optical
source was detected on the first epoch with an I-band magnitude of 21.6,
which faded by at least 0.5 mag on the 2nd epoch observation. We propose
this source to be the optical afterglow to GRB 180818B.
The above mentioned magnitude is calibrated against the USNO-B1 catalog
and is not corrected for Galactic extinction in the direction of the
GRB. Further observations are encouraged.
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