TITLE: GCN CIRCULAR NUMBER: 10441 SUBJECT: GRB 100219A: VLT/X-shooter redshift DATE: 10/02/20 04:48:54 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst 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.