[vsnet-grb-info 15422] GRB 140818B: OSN I-band afterglow candidate

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16711
SUBJECT: GRB 140818B: OSN I-band afterglow candidate
DATE:    14/08/18 22:50:24 GMT
FROM:    Alberto Castro-Tirado at Inst.de Astro. de Andalucia  <ajct at iaa.es>

F.J. Aceituno (OSN/IAA-CSIC), J. Gorosabel (IAA-CSIC/UPV-EHU) and A.J.
Castro-Tirado (IAA-CSIC/UMA), report on behalf of a larger collaboration:

We observed the field of GRB 140818B (Vargas et al., GCN 16709) with the
1.5m OSN telescope at Observatorio de Sierra Nevada (Spain). Several 300s
images were acquired in the I- and R-band starting on Aug 18, 20:15 UT
(i.e. 1.5 hours post burst). An optical source at the edge of the
Swift/XRT error box is detected at coordinates (J2000) RA: 18 04 32.47,
Dec: -01 23 09.8 (+/- 1"), which is not present in the corresponding DSS-2
image. A preliminary photometry  against  the USNO  B1.0  catalog yields
an I-band magnitude of 19.7 (Vega). At the moment we cannot determine if
the source if fading in brightness. Further observations are encouraged.