GCN Circular 13134

T. Kruehler, J. P. U Fynbo, B. Milvang-Jensen (all DARK), N. Tanvir (U. Leicester) and P. Jakobsson (U. Iceland) report on behalf of a larger collaboration.

We observed the optical/NIR afterglow (e.g., Sbarufatti et al., GCN# 13123, Klotz et al., GCN#13124, Smith et al., GCN#13125) of the Swift GRB 120327A (Sbarufatti et al., GCN# 13123) with the VLT/UT2 equipped with the X-shooter spectrograph. Observations started around 05:03 UT on 2012-03-27, which is roughly 2.13 hrs after the trigger. Four exposures in a nodding pattern with an integration time of 600 s each were obtained. The spectrum covers an approximate wavelength range between 3100 and 23000 AA. The slit width was set to 1" in the ultra-violet/blue arm, and 0.9" in the visual and near-infrared arm, resulting in a resolving power range of approximately 4500-7500.

Preliminary reduction of the spectrum shows a well detected continuum with several absorption features, that we identify with Ly-limit and Ly-alpha as well as absorption lines of CII/CII*, SiII/SiII*, AlI, FeII and MgII at a redshift of 2.813. This is confirms previous reports based on spectroscopy (Perley & Tanvir, GCN #13133) and photometry (Sudilovsky et al. GCN #13129).

We are grateful for the excellent support from the Paranal Observatory staff, in particular Dimitri Gadotti. We acknowledge private communication with the GROND team, in particular Vlad Sudilovsky.