逃逸星在银河系内的速度分布

发布时间：2018-12-13 04:18

【摘要】：在由两颗恒星组成的双星系统中,如果发生超新星爆发,该系统可能会解体,幸存下来的恒星就可能会变成逃逸星(runaway stars)。超新星爆发根据爆发机制的不同可以分为两类:核塌缩型超新星爆发和热核爆发型超新星爆发。核塌缩型超新星爆发是初始质量大于8M恒星演化后期的剧烈的质量损失过程。爆发后新形成的致密天体(可能是中子星或黑洞)得到一个额外的踢速度(kick速度)。如果双星系统因为核塌缩型超新星爆发而解体,形成的逃逸星在本文中叫做核塌缩-逃逸星,标记为CC-RASs。在双星系统中,碳氧(CO)白矮星从伴星吸积物质,当其质量达到钱德拉塞卡极限质量时发生热核爆发型超新星爆发。白矮星在很短的时间内炸光,伴星变成逃逸星。这类逃逸星在本文中叫做热核-逃逸星,标记为TN-RASs。在本文中,我们利用星族合成方法,研究这两类逃逸星的速度分布及其它特性。研究发现,CC-RASs的速度主要分布在30—100 km s-1之间。与已观测到的大部分逃逸星的速度分布非常吻合。已经观测到的大部分逃逸星很可能是CC-RASs。根据恒星化学成分以及结构的不同,TN-RASs也可以分成两个子类:富氢TN-RASs和富氦TN-RASs。这两类TN-RASs的速度分别在100—500 km s-1和600—1100km s-1之间。这与银河系内观测到的超高速星的速度分布非常吻合。在银河系内,已经观测到的超高速星也可能是TN-RASs。US 708是在银河系内发现的速度最快的一颗恒星,其运动速度为1157±53 km s-1。US 708是富氦恒星,很可能是双星系统中发生热核爆发型超新星爆发而产生的。如果在我们的模型里面考虑到超新星抛射物对伴星影响,富氦TN-RASs的速度分布可以解释US 708。
[Abstract]:In a binary system of two stars, if a supernova erupts, the system may disintegrate, and the surviving star may become an escape star, (runaway stars). The supernova burst can be divided into two types according to its mechanism: nuclear collapse type supernova burst and thermonuclear explosion type supernova explosion. The nuclear collapse type supernova burst is a severe mass loss process in the late stage of star evolution with initial mass larger than 8M. A newly formed dense object (possibly a neutron star or a black hole) after the eruption gets an extra kick velocity (kick velocity). If the binary system disintegrates as a result of a nuclear collapse supernova burst, the resulting escape star is called the nuclear collapse-escape star in this paper, labeled CC-RASs. In a binary system, a thermonuclear explosion supernova occurs when the mass of the carbon oxygen (CO) dwarf accretes from the companion star when its mass reaches the limit mass of Chandrasekha. The white dwarf explodes in a short time and the companion becomes an escape star. This type of escape star is called the thermonuclear escape star in this paper and is labeled TN-RASs. In this paper, we study the velocity distribution and other characteristics of these two escape stars by using the star family synthesis method. It was found that the velocity of CC-RASs was mainly between 30 and 100 km s -1. It coincides well with the velocity distribution of most of the observed escape stars. Most of the observed escape stars are likely to be CC-RASs. Depending on the chemical composition and structure of the star, TN-RASs can also be divided into two subclasses: hydrogen-rich TN-RASs and helium-rich TN-RASs. The velocities of these two kinds of TN-RASs are between 100-500 km s -1 and 600-1100km s -1, respectively. This coincides well with the velocity distribution of hypervelocity stars observed in the Milky way. In the Milky way, the observed hypervelocity star may also be TN-RASs.US 708, the fastest star found in the Milky way, with a speed of 1157 卤53 km s-1.US 708 being a helium-rich star. It is likely that a thermonuclear burst supernova occurred in a binary system. If the influence of supernova ejection on the companion star is taken into account in our model, the helium rich TN-RASs velocity distribution can explain the US 708.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P156;P145.3

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