S. Piranomonte (INAF/Roma), D. Malesani (DARK/NBI), V. D'Elia (ASDC and
INAF/Roma), S. Covino (INAF/Brera), L.A. Antonelli (INAF/Roma), D.
Fugazza (INAF/Brera), A. Harutyunyan (INAF/TNG), G. Tessicini
(INAF/TNG), report on behalf of a larger collaboration:
Following the release of the refined X-ray position (Osborne et al., GCN
11526) of the afterglow of GRB 110106A (Mangano et al., GCN 11520), we
further inspected our TNG images. The faint object reported by Malesani
et al. (GCN 11524) is significantly outside the revised error circle,
and is thus likely unrelated to the GRB.
The new X-ray position however partially covers the outskirts of the
extended object mentioned in GCN 11520.
A 1-hr TNG spectrum of this galaxy, starting on Jan 6.878 UT (5.64 hr
after the GRB) and covering the wavelength range 3800-8000 AA, reveals
the presence of a few emission features, which we interpret as Halpha,
[NII] 6583, [SII] 6730, and weak Hbeta at a common redshift z=0.093. At
the same redshift, we also see Ca H and K in absorption.
While the XRT error circle (1.7" radius) overlaps the stellar light from
the galaxy, its center lies 4.3" away of the galaxy nucleus (7.3 kpc in
projection at z=0.093). Such large offset would be more typical of
short-duration GRBs, although the duration of GRB 110106A (T90 =
4.3+-1.1 s; Stamatikos et al., GCN 11527) seems to exclude this
hypothesis. The relation between the galaxy and the GRB cannot be
conclusively established at this point.