The Type Ib SN 1999dn: One year of photometric and spectroscopic monitoring

Abstract

Extensive optical and near-infrared observations of the Type Ib supernova (SNIb) 1999dn are presented, covering the first year after explosion. These new data turn this object, already considered a prototypical SNIb, into one of the best observed objects of its class. The light curve of SN 1999dn is mostly similar in shape to that of other SNeIb but with a moderately faint peak (MV=-17.2mag). From the bolometric light curve and ejecta expansion velocities, we estimate that about 0.11M⊙ of 56Ni were produced during the explosion and that the total ejecta mass was 4-6M⊙ with a kinetic energy of at least 5 × 1051erg. The spectra of SN 1999dn at various epochs are similar to those of other stripped envelope SNe showing clear presence of H at early epochs. The high explosion energy and ejected mass, along with the small flux ratio [Caii]/[Oi] measured in the nebular spectrum, together with the lack of signatures of dust formation and the moderate metallicity environment is not inconsistent with a single massive progenitor (MZAMS≥ 23-25M⊙) for SN 1999dn. © 2010 The Authors Monthly Notices of the Royal Astronomical Society © 2010 RAS.