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SN 2006aj Associated with XRF 060218 At Late Phases: Nucleosynthesis-Signature of A Neutron Star-Driven Explosion

Keiichi Maeda·Koji Kawabata·Masaomi Tanaka·Ken'ichi Nomoto·Nozomu Tominaga·Takashi Hattori·Takeo Minezaki·Takami Kuroda·Tomoharu Suzuki·Jinsong Deng·Paolo A. Mazzali·Elena Pian
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Abstract

Optical spectroscopy and photometry of SN 2006aj have been performed with the Subaru telescope at t > 200 days after GRB060218, the X-ray Flash with which it was associated. Strong nebular emission-lines with an expansion velocity of v ~ 7,300 km/s were detected. The peaked but relatively broad [OI]6300,6363 suggests the existence of ~ 2 Msun of materials in which ~1.3 Msun is oxygen. The core might be produced by a mildly asymmetric explosion. The spectra are unique among SNe Ic in (1) the absence of [CaII]7291,7324 emission, and (2) a strong emission feature at ~ 7400A, which requires ~ 0.05 Msun 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 Msun < Mms < 22 Msun and E ~ (1 - 3) 10^{51} erg, respectively.

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Keiichi Maeda, Koji Kawabata, Masaomi Tanaka, Ken'ichi Nomoto, Nozomu Tominaga, Takashi Hattori, Takeo Minezaki, Takami Kuroda, Tomoharu Suzuki, Jinsong Deng, Paolo A. Mazzali, Elena Pian. 2007-03-08. SN 2006aj Associated with XRF 060218 At Late Phases: Nucleosynthesis-Signature of A Neutron Star-Driven Explosion. https://doi.org/10.1086/513564

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