A. Rossi, E. Pian, F. Cusano, E. Maiorano, E. Palazzi (INAF-OAS) on
behalf of the CIBO collaboration, and S. Belkin (IKI, HSE) report :
We report the results of the spectroscopic follow-up observations of
ZTF22aabjpxh/AT2022cva, the afterglow of GRB 220219B (Ho et al., GCN
31619; Kim�� et al., GCN 31628; Hu et al., GCN 31639; Belkin et al., GCNs
31643, 31683; Pasham et al., GCN 31635; Beardmore et al., GCN 31644;
Tsvetkova et al., GCN 31646) at z=0.293 (Fremling et al., GCN 31629).
The optical spectra were obtained with the Multi-Object Double
Spectrographs (MODS) instrument mounted on the 2x8.4-m LBT telescope
(Mt. Graham, AZ, USA) at ~11 UT on 2021-03-07, ~16 days (i.e. ~12
rest-frame days) after the burst trigger. The spectra covers the
wavelength range 3200-10000 AA, and we obtained a total of 6 exposures
of 900s. The resulting spectrum has been corrected for Galactic
extinction (A_V = 0.025 mag).
The slit was place in order to cover both the host galaxy and the GRB
position. In addition to the host spectra, a second trace is well
visible in the 2D image of the spectrum although superimposed to the one
of the host galaxy. Its low S/N extracted spectrum shows features
similar to those exhibited by XRF-associated SN2006aj at a similar phase
(Mazzali et al. 2006, Nature, 442, 1018). This confirms the bump
observed by Belkin et al. (GCN 31736) as due to the emerging
contribution of the SN.
We acknowledge the excellent support from the LBTO, in particular B.
Rothberg and J. Williams, and from the LBT-INAF, particularly E. Marini
in obtaining these observations.