GCN Circular 26989
Subject
GRB 200205A / Swift trigger 954304: VLT optical observations
Event
Date
2020-02-05T18:32:10Z (6 years ago)
From
Daniele B Malesani at DTU Space <malesani@space.dtu.dk>
D. B. Malesani (DTU Space), L. Izzo (DARK/NBI), J. Palmerio (GEPI -
Paris Observatory), N. R. Tanvir (Univ. Leicester), A. J. Levan (Radboud
Univ.), D. A. Kann (HETH-IAA/CSIC), report on behalf of the Stargate
consortium:
We observed the optical counterpart of GRB 200205A / Swift trigger
954304 (Evans et al., GCN 26982), with the ESO VLT UT2 (Kueyen) equipped
with the X-shooter instrument. Unfortunately, observations could be
started only late in twilight and no spectroscopy was secured.
We confirm the presence of an optical counterpart just outside the
currently available (unenhanced) XRT position (Evans et al., GCN 26982;
Lipunov et al., GCN 26984; Melandri et al., GCN 26986). Its coordinates
are (calibrated to the Gaia catalog; 0.2" uncertainty):
RA = 08:40:40.94
Dec = -35:16:25.1
In a 60-s image taken in the SDSS r filter at a mid time Feb 5.385 UT
(2.63 hr after the BAT trigger), we measure for it r = 17.7+-0.1 AB,
where the error is dominated by the scatter of the calibrators, chosen
from the SkyMapper catalog (Wolf et al. 2018, PASA, 35, 010;
https:doi.org/10.4225/41/593620ad5b574).
We note that the MAXI detection for a prolonged time at X-ray energies
(Niwano et al., GCN 26987), the unusually large optical/gamma-ray
brightness ratio, and the low Galactic latitude (4 deg above the plane)
may indicate that this source is not a GRB but a Galactic transient.
Further analysis of the high-energy data, or ground-based spectroscopic
observations, will be necessary to distinguish among these options.
We acknowledge support from the ESO observing staff in Paranal, in
particular Elyar Sedaghati, Eleonora Sani, and Ditte Slumstrup.