GCN Circular 10441
Subject
GRB 100219A: VLT/X-shooter redshift
Date
2010-02-20T04:48:54Z (15 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
P. Groot (Radboud Univ. Nijmegen), L. Kaper, L. Ellerbroek (Univ.
Amsterdam), D. Malesani (DARK/NBI), P. Jakobsson (Univ. Iceland), J. P.
U. Fynbo, J. Hjorth, D. J. Watson (DARK/NBI), and E. Mason (ESO), report
on behalf of a larger collaboration:
We observed the optical objects associated to GRB 100219A (Rowlinson et
al., GCN 10430; Holland & Rowlinson, GCN 10432; Bloom & Nugent, GCN
10433; Jakobsson et al., GCN 10438; Kruehler et al., GCN 10439) with the
VLT equipped with the X-shooter spectrograph. The slit was oriented so
to include both the pre-existing object and the candidate afterglow.
Observations started on 2010 Feb 20.105 UT (0.47 days after the GRB),
for a total exposure time of 4x1200 s.
In a preliminary analysis of the spectra, we detect a clear signal from
both objects. The continuum from the candidate afterglow is only
detected redward of ~5310 AA. A further spectral break is recognised at
~7060 AA. This is consistent with the onset of the Lyman limits and of
the Lyman alpha forest at a common redshift z = 4.8. Our observations
are consistent with the photometric redshift indicated by the GROND
observations (Kruehler et al., GCN 10439).
The high luminosity of the object and its spectral shape indicate that
this is indeed the afterglow of GRB 100219A.
The spectrum of the nearby galaxy implies a significantly lower
redshift, around z=0.25, hence it is unrelated to the GRB.
We caution that the above analysis (particularly the wavelength
solution) is preliminary. Reduction with updated calibrations is
underway. We would like to thank Alain Smette (ESO) for his kind assistance.