GCN Circular 34066
Subject
LIGO/Virgo/KAGRA S230615az: LBT spectroscopic classification of GOTO23hn
Date
2023-06-22T16:34:20Z (2 years ago)
From
Andrea Rossi at INAF <andrea.rossi@inaf.it>
E. Maiorano, A. Rossi, E. Palazzi, F. Cusano (INAF-OAS Bologna), L. Izzo (INAF-OAC, DARK/NBI), S.Benetti (INAF OAPd), A. Melandri (INAF-OAR), P. D’Avanzo (INAF-OAB), and V. D’Elia (SSDC and INAF-OAR) report on behalf of GRAvitational Wave Inaf TeAm (GRAWITA):
We report the classification of spectroscopic observations of GOTO23hn (Gompertz et al., GCN #33979; Strausbaugh et al., GCN 34020), one of the GOTO candidate counterparts of the LIGO/Virgo event S230615az. The LBT/MODS spectrum has been obtained at the mid-time 04:33 UT on 2023-06-21, 5.7 days after the GW trigger, for a total on-source time of 1200 s, covering the wavelength range 3200-10000 AA as described in Rossi et al. (GCN #34061), where we measure a spectroscopic redshift of z=0.0929 for the host galaxy.
The spectra display a strong SII line, indicative of a SN Ia. Using the SNID software (Blondin & Tonry 2007), the best match is found with SN 1993ac at about 7 days after maximum. Multiband photometry was also collected and a preliminary analysis gives r=19.015 +-0.014 and g=18.856+- 0.008, AB mag.
We acknowledge the excellent support from the LBTO and LBT-INAF staff, particularly D. Thompson, D. G. Huerta , and D. Paris, in obtaining these observations.