[vsnet-grb-info 20988] GRB 180805B: VLT optical and near-infrared observations
GCN Circulars
gcncirc at capella2.gsfc.nasa.gov
Mon Aug 6 22:01:54 JST 2018
TITLE: GCN CIRCULAR
NUMBER: 23086
SUBJECT: GRB 180805B: VLT optical and near-infrared observations
DATE: 18/08/06 13:01:16 GMT
FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani at dark-cosmology.dk>
D. B. Malesani (DAWN/NBI and DARK/NBI), G. Pugliese (API/Univ.
Amsterdam), P. D'Avanzo (INAF/Brera), N. R. Tanvir (Univ. Leicester), K.
Wiersema (Univ. Warwick), report on behalf of the Stargate consortium:
We observed the field of GRB 180805B, classified as short with extended
emission (D'Avanzo et al., GCN 23076; Sakamoto et al., GCN 23082), using
the ESO Telescopes located in Cerro Paranal. Optical and near-infrared
observations were obtained using the FORS2 and HAWK-I instruments,
respectively. No counterpart is detected inside the UVOT-enhanced XRT
error circle (Evans et al., GCN 23077) in either images, with the
3-sigma upper limits summarized in the table below.
Filter Mid time (UT) Time since GRB (hr) Limiting mag (Vega)
---------------------------------------------------------------
J Aug 6.245 16.84 23.5
R Aug 6.363 19.67 25.5
Calibration was carried out against a single 2MASS star for the J band,
and using archival FORS2 zeropoints for the R band.
We note the presence of four extended objects within a few arcsec of the
center of the XRT error circle, including a source 3.5" North of the GRB
(R ~ 22.5) also visible in the Pan-STARRS r and i images. Their
association with the GRB cannot be assessed at the present time.
We acknowledge excellent support from the ESO observing staff in
Paranal, especially Stephane Brillant, Joe Anderson, and Bian Fuyan. DBM
also acknowledges useful discussion with Amy Lien (GSFC/UMBC) about the
classification of this GRB.
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