Nebular Phase Observations of the Type Ib Supernova 2008D/X-Ray Transient 080109 : Side-Viewed Bipolar Explosion

Tanaka Masaomi

Yamanaka Masayuki

Maeda Keiichi

Kawabata Koji S

Hattori Takashi

Minezaki Takeo

Valenti Stefano

Della Valle Massimo

Sahu D. K

Anupama G. C

Tominaga Nozomu

Nomoto Ken'ichi

Mazzali Paolo A

Pian Elena

Astrophysical Journal

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 Ni-56 mass of 0.07 M-circle dot, 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 degrees from the polar direction.

line: profiles

nuclear reactions, nucleosynthesis, abundances

supernovae: general

supernovae: individual (SN 2008D)

Astronomy. Space sciences [ 440 ]

eng

IOP Publishing LTD

[ISSN] 0004-637X

[DOI] 10.1088/0004-637X/700/2/1680

[NCID] AA00553253

[DOI] http://dx.doi.org/10.1088/0004-637X/700/2/1680