GCN Circular 10441

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
Not found
 
 
; Holland & Rowlinson, GCN 10432
Not found
 
 
; Bloom & Nugent, GCN 
10433
Not found
 
 
; Jakobsson et al., GCN 10438
Not found
 
 
; Kruehler et al., GCN 10439
Not found
 
 
) 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
Not found
 
 
).

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.