{
  "bibcode": "2022GCN.32850....1M",
  "body": "E. Maiorano, E. Palazzi, A. Rossi (INAF-OAS), V. D'Elia (SSDC & \nINAF-OAR), and A. Melandri (INAF-OAR) on behalf of the CIBO \ncollaboration, and F. Cusano (INAF-OAS), L. Izzo (DARK/NBI) report:\n\nWe report the results of the spectroscopic follow-up observations of the \nafterglow of GRB 221009A (Dichiara et al., GCN 32632; Fermi GBM \ndetection: Veres et al., GCN 32636). The optical spectra were obtained \nwith the Multi-Object Double Spectrographs (MODS) instrument mounted on \nthe 2x8.4-m LBT telescope (Mt. Graham, AZ, USA) at 3 UT on 2022-10-18, \n8.56 days after the burst trigger. The spectra cover the wavelength \nrange 3200-10000 AA, and we obtained a total of 6 exposures of 900 s.\n\nAfter correction for the foreground Galactic extinction (E(B-V)=1.324, \nSchlafly & Finkbeiner 2011), we find that the resulting spectrum is \nclearly dominated by the afterglow. We subtracted the afterglow \ncontribution assuming a spectral slope -0.7 (using the convention F_nu ~ \nnu^-beta), anchored to the simultaneous NIR flux. This value has been \nobtained modeling the NIR light curve of the afterglow (Ferro et al., \nGCN 32804; D'Avanzo et al., GCN 32755). The remaining low S/N spectrum \nshows features typical of type Ic-BL supernovae. Therefore, we confirm \nthe emerging contribution of SN 2022xiw (de Ugarte Postigo et al. et al. \nTNSCR, 2022-3047) as reported by de Ugarte Postigo et al. (GCN 32800).\n\nWe acknowledge the excellent support from the LBTO and LBT-INAF staff, \nparticularly A. Becker and D. G. Huerta, in obtaining these observations.",
  "circularId": 32850,
  "createdOn": 1666716609000,
  "email": "andrea.rossi@inaf.it",
  "subject": "GRB 221009A: spectroscopic confirmation of SN in LBT spectra",
  "submitter": "Andrea Rossi at INAF  <andrea.rossi@inaf.it>",
  "eventId": "GRB 221009A"
}