Optical spectroscopy and photometry of SN 2006aj have been performed with the Subaru telescope at t > 200 days after GRB 060218, the X-ray flash with which it was associated. Strong nebular emission lines with an expansion velocity of v ∼ 7300 km s-1 were detected. The peaked but relatively broad [O I] λλX6300, 6363 suggests the existence of ∼2 M⊙ of materials in which ∼1.3 M⊙ is oxygen. The core might be produced by a mildly asymmetric explosion. The spectra are unique among SNe Ic in (1) the absence of [Ca II] λλ7291, 7324 emission and (2) a strong emission feature at ∼7400 Å, which requires ∼0.05 M⊙ of newly synthesized 58Ni. Such a large amount of stable neutron-rich Ni strongly indicates the formation of a neutron star. The progenitor and the explosion energy are constrained to 18 M⊙ ≲ Mms ≲ 22 M⊙ and E ∼ (1-3) × 1051 ergs, respectively.
- Gamma rays: bursts
- Nuclear reactions, nucleosynthesis, abundances
- Supernovae: general
- Supernovae: individual (SN 2006aj)
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science