Nebular Phase Observations of the Type Ib Supernova 2008D/X-ray Transient 080109: Side-Viewed Bipolar Explosion
Abstract
We present optical spectroscopic and photometric observations of supernova (SN) 2008D, associated with the luminous X-ray transient 080109, at >300 days after the explosion (nebular phases). We also give flux measurements of emission lines from the H II region at the site of the SN, and estimates of the local metallicity. The brightness of the SN at nebular phases is consistent with the prediction of the explosion models with an ejected 56Ni mass of 0.07 Msun, which explains the light curve at early phases. The [O I] line in the nebular spectrum shows a double-peaked profile while the [Ca II] line does not. The double-peaked [O I] profile strongly indicates that SN 2008D is an aspherical explosion. The profile can be explained by a torus-like distribution of oxygen viewed from near the plane of the torus. We suggest that SN 2008D is a side-viewed, bipolar explosion with a viewing angle of > 50^{\circ} from the polar direction.
Keywords
Cite
@article{arxiv.0906.1061,
title = {Nebular Phase Observations of the Type Ib Supernova 2008D/X-ray Transient 080109: Side-Viewed Bipolar Explosion},
author = {Masaomi Tanaka and Masayuki Yamanaka and Keiichi Maeda and Koji S. Kawabata and Takashi Hattori and Takeo Minezaki and Stefano Valenti and Massimo Della Valle and D. K. Sahu and G. C. Anupama and Nozomu Tominaga and Ken'ichi Nomoto and Paolo A. Mazzali and Elena Pian},
journal= {arXiv preprint arXiv:0906.1061},
year = {2009}
}
Comments
6 pages, 7 figures, Accepted for publication in ApJ