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arXiv 2003.02970astro-ph.HEastro-ph.SR
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SAX J1808 .4-3658的双星演化:演化施主星的意义

The binary evolution of SAX J1808.4-3658: Implications of an evolved donor star

A. J. Goodwin, T. E. Woods

摘要:

对吸积动力毫秒脉冲星SAXJ1808.4 -3658的观测揭示了一个有趣的双星演化,系统的轨道以加速的速度膨胀。我们使用最近的发现,在SAXJ1808.4 -3658的吸积燃料是氢耗尽大大改善模型的祖先和先前的演变的二元系统。我们约束的伴星的初始质量为1.0-1.2 M $_{\mathrm{\odot}}$,更大的质量比以前的演化研究这个系统已经假设。我们还推断系统必须经历强烈的非保守质量转移,以解释所观察到的轨道周期的变化。继Jia & Li(2015)之后,我们考虑了由于供体星上的脉冲星辐射压力引起的质量损失,引起蒸发风,该蒸发风在双星系统的内拉格朗日点喷出。由此产生的额外的角动量损失解决了保守的质量转移模型和观测到的轨道周期导数之间的差异,该系统。我们还包括了由于吸积光度施主照射的治疗,并发现这对系统的演化有不可忽视的影响。

英文摘要:

Observations of the accretion powered millisecond pulsar SAX J1808.4-3658 have revealed an interesting binary evolution, with the orbit of the system expanding at an accelerated rate. We use the recent finding that the accreted fuel in SAX J1808.4-3658 is hydrogen depleted to greatly refine models of the progenitor and prior evolution of the binary system. We constrain the initial mass of the companion star to 1.0-1.2 M$_{\mathrm{\odot}}$, more massive than previous evolutionary studies of this system have assumed. We also infer the system must have undergone strongly non-conservative mass transfer in order to explain the observed orbital period changes. Following Jia & Li (2015), we include mass loss due to the pulsar radiation pressure on the donor star, inducing an evaporative wind which is ejected at the inner Lagrangian point of the binary system. The resulting additional loss of angular momentum resolves the discrepancy between conservative mass transfer models and the observed orbital period derivative of this system. We also include a treatment of donor irradiation due to the accretion luminosity, and find this has a non-negligible effect on the evolution of the system.

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