Optical studies of SN2009jf: A Type Ib supernova with an extremely slow decline and aspherical signature

Abstract

Optical UBVRI photometry and medium-resolution spectroscopy of the Type Ib supernova SN2009jf, during the period from ∼-15 to +250d, with respect to the B maximum are reported. The light curves are broad, with an extremely slow decline. The early post-maximum decline rate in the V band is similar to SN2008D; however, the late-phase decline rate is slower than other Type Ib supernovae studied. With an absolute magnitude of MV=-17.96 ± 0.19 at peak, SN2009jf is a normally bright supernova. The peak bolometric luminosity and the energy deposition rate via the 56Ni →56Co chain indicate that ∼0.17+0.03-0.03M⊙ of 56Ni was ejected during the explosion. The Hei 5876Å line is clearly identified in the first spectrum of day ∼-15, at a velocity of ∼16000kms-1. The [Oi] 6300-6364Å line seen in the nebular spectrum has a multipeaked and asymmetric emission profile, with the blue peak being stronger. The estimated flux in this line implies that ≳1.34M⊙ oxygen was ejected. The slow evolution of the light curves of SN2009jf indicates the presence of a massive ejecta. The high expansion velocity in the early phase and broader emission lines during the nebular phase suggest it to be an explosion with a large kinetic energy. A simple qualitative estimate leads to the ejecta mass of Mej= 4-9M⊙ and kinetic energy EK= 3-8 × 1051erg. The ejected mass estimate is indicative of an initial main-sequence mass of ≳20-25M⊙. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.