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arXiv 1102.1732astro-ph.SR
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IIb型超新星的双星祖先模型

Binary progenitor models of type IIb supernovae

J. S. W. Claeys, S. E. de Mink, O. R. Pols, J. J. Eldridge, M. Baes

摘要:

失去富氢外壳的大质量恒星会爆炸成扩展的IIb型超新星,这是一种有趣的亚型,将富氢的II型超新星与贫氢的Ib型和Ic型超新星联系起来。母星可能是非常巨大的单颗恒星,由于它们的恒星风而失去了它们的外壳,但由于与双星系统中的伴星相互作用而导致的质量剥离目前被认为是主要的形成通道。我们用Eggleton二进制演化代码计算了一个广泛的二进制模型网格。从我们的标准模型,其中假设保守的传质预测率,是约6倍小于目前的速度由观察表明。它更大,但仍然与预期的单星速率相当。为了恢复观测到的速率,我们必须慷慨地考虑到不确定性和低吸积效率,以及系统有限的角动量损失。受少数IIb超新星发现和未发现伴星的影响,我们研究了次级恒星在爆炸时刻的性质。我们确定了三种情况:(1)在大约90%的情况下,伴星看起来是一颗热的O星;(2)在大约3%的情况下,伴星变成一颗过亮的B星;或者(3)伴星看起来是一颗K超巨星。第二种情况,适用于SN 1993 J和可能的SN 2001 ig,是最不常见的情况,要求伴星非常有效地吸积转移的物质-与恢复总IIb速率所需的条件相反。快速增加的IIb型探测器数量可能会导致对模型不确定性的更坚实的约束,如恒星风质量损失和内部混合。

英文摘要:

Massive stars that lose their hydrogen-rich envelope down to a few tenths of a solar mass explode as extended type IIb supernovae, an intriguing subtype that links the hydrogen-rich type II supernovae with the hydrogen-poor type Ib and Ic. The progenitors may be very massive single stars that lose their envelope due to their stellar wind, but mass stripping due to interaction with a companion star in a binary system is currently considered to be the dominant formation channel. We computed an extensive grid of binary models with the Eggleton binary evolution code. The predicted rate from our standard models, which assume conservative mass transfer, is about 6 times smaller than the current rate indicated by observations. It is larger but still comparable to the rate expected from single stars. To recover the observed rate we must generously allow for uncertainties and low accretion efficiencies in combination with limited angular momentum loss from the system. Motivated by the claims of detection and non-detection of companions for a few IIb supernovae, we investigate the properties of the secondary star at the moment of explosion. We identify three cases: (1) the companion appears as a hot O star in about 90% of the cases, (2) the companion becomes an over-luminous B star in about 3% of the cases, or (3) the companion will appear as a K supergiant. The second case, which applies to the well-studied case of SN 1993J and possibly to SN 2001ig, is the least common case and requires that the companion very efficiently accretes the transferred material -in contrast to what is required to recover the overall IIb rate. The fast increasing number of type IIb detections may lead to more solid constraints on model uncertainties, like stellar wind-mass loss and internal mixing.

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