AstroNote 2023-145

The Nordic optical telescope Un-biased Transient Survey (NUTS2) collaboration report five spectroscopic observations of supernova (SN) 2023ixf have been obtained with the NOT equipped with the low-resolution optical imager and spectrograph ALFOSC. Observations were performed on +2.16d, +3.06d, +4.09d, +5.05d, and +6.25d past the earliest detection (i.e., MJD-60082.85) as reported by Astronotes 2023-130, 2023-133. The first week of evolution reveals spectra with a blue continua, superposed by hydrogen and helium features. The notable flash-ionisation CIII+NIII features present in the classification spectrum taken on +1.08d and reported by Astronote (2023-119) disappear by +2.16d. The NUTS2 sequence reveals the evolution of a number of features including the weakening of both the conspicuous hydrogen Balmer as well as singly and doubly ionised helium features. The full-width-half-maximum velocity of the H-alpha emission feature between +2.16d and +6.25d is estimated to be consistently around 900 km/s. In addition, the data reveal the emergence and disappearance of a feature around 5800 Angstroms likely formed by CIV.

Data taken in the framework of the NUTS2 collaboration https://nuts.sn.ie/ which is funded in part by the Instrument center for Danish Astrophysics (IDA). We thank NOT staff and visiting scientists for their support in executing these observations on the behalf of NUTS2.