GCN Circular 3089
Subject
GRB 050306: optical afterglow
Event
Date
2005-03-12T18:46:02Z (20 years ago)
From
Daniele Malesani at SISSA-ISAS,Trieste,Italy <malesani@sissa.it>
P. D'Avanzo, D. Fugazza, S. Covino (INAF-OABr), D. Malesani (SISSA), N.
Masetti, E. Palazzi (IASF-CNR), L.A. Antonelli, G.L. Israel (INAF-OARm),
and G. Andreuzzi (INAF-TNG), report on behalf of a larger Italian
collaboration:
We imaged again (Fugazza et al., GCN 3078) the field of GRB 050306
(Markwardt et al., GCN 3071) with the Italian TNG telescope.
Observations were carried out under a clear sky and with a seeing of
about 1.6", starting on 2005 Mar 9.247 UT. Seven R-band exposures were
acquired, with an overall exposure time of 21 minutes (mean UT Mar
9.260, i.e. 3.11 days after the burst).
Inside the revised error circle of the XRT afterglow (Perri et al., GCN
3075; Mangano et al., GCN 3086), we detect several sources. After
performing PSF photometry with DAOPhot, we find that the object at
coordinates:
alpha(J2000) = 18:49:13.95
delta(J2000) = -09:09:08.6
(that is, 3.5" off the XRT centroid position) has faded by 0.54+-0.10
mag since our previous observation, carried out ~2.1 days after the GRB
(Fugazza et al., GCN 3078). Assuming a powerlaw decay (F(t) =
K*t^-delta), this corresponds to delta = 1.28+-0.24, a value typical
among GRB afterglows at comparable epochs. We thus propose that this
object is the optical afterglow of GRB050603. Based on calibration upon
USNO stars, the object has R ~ 23 at the time of our first observation,
Mar 8.25 UT.
A finding chart of the field is posted at the following URL:
http://www.sissa.it/~malesani/GRB/050306
Further observations are planned at the TNG in the following nights, but
no spectroscopy will be possible.
We warmly acknowledge the TNG staff for carefully performing the
observations.
This message can be cited.