The He-rich core-collapse supernova 2007Y: Observations from X-ray to Radio Wavelengths
Abstract
A detailed study spanning approximately a year has been conducted on the Type Ib supernova 2007Y. Imaging was obtained from X-ray to radio wavelengths, and a comprehensive set of multi-band (w2m2w1u'g'r'i'UBVYJHKs) light curves and optical spectroscopy is presented. A virtually complete bolometric light curve is derived, from which we infer a (56)Ni-mass of 0.06 Msun. The early spectrum strongly resembles SN 2005bf and exhibits high-velocity features of CaII and Halpha; during late epochs the spectrum shows evidence of a ejecta-wind interaction. Nebular emission lines have similar widths and exhibit profiles that indicate a lack of major asymmetry in the ejecta. Late phase spectra are modeled with a non-LTE code, from which we find (56)Ni, O and total-ejecta masses (excluding He) to be 0.06, 0.2 and 0.42 Msun, respectively, below 4,500 km/s. The (56)Ni mass confirms results obtained from the bolometric light curve. The oxygen abundance suggests the progenitor was most likely a ~3.3 Msun He core star that evolved from a zero-age-main-sequence mass of 10-13 Msun. The explosion energy is determined to be ~1050 erg, and the mass-loss rate of the progenitor is constrained from X-ray and radio observations to be <~10-6 Msun/yr. SN 2007Y is among the least energetic normal Type Ib supernovae ever studied.