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大质量白矮星双星的观测研究
文献类型：学位论文
| 作者 | 时光 |
| 学位类别 | 博士 |
| 答辩日期 | 2014-05-29 |
| 授予单位 | 中国科学院研究生院（云南天文台） |
| 授予地点 | 北京 |
| 导师 | 钱声帮 |
| 关键词 | 密近双星 恒星：演化 星风外流 白矮星 超新星 轨道周期分析 |
| 其他题名 | The observational investigations on the binary systems with massive white dwarfs |
| 学位专业 | 天体物理 |
| 中文摘要 | 根据密近双星中的子星白矮星质量，我们定义了一类具有相互作用的密近 双星系统，名为大质量白矮星双星。在这类系统中，主星是一颗具有较大质量 （一般接近或者大于1 M⊙）的白矮星，而伴星可能是一颗主序星、红巨星或者 渐进巨星分支等非简并恒星，也可能是一颗He星或者白矮星等简并星，在极端 情况下甚至可能是一个中子星或者黑洞。在标准模型下，随着双星的演化，物 质转移和物质吸积将会导致碳/氧（C/O）白矮星质量不断增加，当质量达到 钱德拉塞卡质量极限时，C/O白矮星最终爆炸成为Ia型超新星（SN Ia）。远距 离星系中Ia型超新星的测距工作，使人们认识到我们的宇宙是在加速膨胀的， 并且揭示了暗物质和暗能量的存在，是天体物理研究领域乃至整个物理学的 巨大突破，因此被授予了2011年诺贝尔物理学奖。然而，Ia型超新星的前身星， 即Ia型超新星的起源，仍然是未解决的科学问题。一般认为，Ia型超新星可能 诞生于具有一颗大质量C/O白矮星的密近双星系统。两颗子星的总质量等于或 者超过钱德拉塞卡质量极限。或者通过吸积非简并伴星的物质，或者通过与简 并的伴星并合，C/O白矮星质量增加并最终产生Ia型超新星。但是也有一些大 质量的白矮星由于内部温度过高，形成氧/氖/镁（O/Ne/Mg）白矮星，最终坍 缩成一颗中子星。 本论文详细介绍了大质量白矮星双星系统的可能演化结局及其理论模型， 还介绍了多种不同类型的大质量白矮星双星系统。通过调研，我们搜集了几 十颗有白矮星质量估测的大质量白矮星双星，作为一个样本。我们从中挑选 了6个样本星（V Sge型双星V Sge、WX Cen和V 617 Sgr 以及长周期的类新 星BT Mon、V363 Aur和QZ Aur），利用国内外的多个地面光学望远镜，对其 进行了长期的测光监测。我们的研究工作获得了以下重要研究成果： 1. 根据轨道周期分析，我们发现在长周期超软X-射线源V Sge和WX Cen中，充满洛希瓣的伴星正在不断地向主星白矮星进行物质转移。这种洛希 瓣外流的物质转移导致了我们观测到的轨道周期长期减小，这个结果与星风 辐射外流物质转移模型预期的轨道周期变化恰恰相反，因此否定了以往研究 中WX Cen是一个低质量比（q = M2/M1 < 1）的星风辐射外流超软X-射线源 的观点。我们还对WX Cen进行了动力学分析并探测其基本物理参数的可能范 围。而在短周期超软X-射线源V617 Sgr中，我们观测到其轨道周期在长期增 加。这个结果符合星风辐射外流物质转移模型的预期。这些超软X射线源很可 能是Ia型超新星前身星的候选体。 2. O-C分析结果表明，长轨道周期的类新星BT Mon、V363 Aur的轨道周 期正在不断下降。引力辐射和磁滞效应导致的轨道周期变化率比观测得到的轨 道周期变化率要小1–2个量级，而主序伴星到主星白矮星的物质转移是导致BT Mon和V363 Aur中轨道周期变化的主要原因。因此，白矮星从伴星获得物质后 其质量不断增加，并最终可能演化成Ia型超新星。测光观测和轨道分析结果显 示，较高的物质转移过程可能存在于QZ Aur 系统之中，而且主星白矮星的质 量与主序伴星的质量非常接近。 3. 在V617 Sgr、BT Mon和V363 Aur的O-C图中探测到的周期振荡成分， 更可能是由第三天体的光时轨道效应导致的。计算结果表明，V617 Sgr中的第 三天体可能是一颗质量非常低的红矮星，而BT Mon和V363 Aur中的第三天体 均可能是几十倍木星质量的褐矮星。 4. 除了大质量白矮星双星系统的研究之外，我们在HW Vir型星（激变双 星前身星）HS 0705+6700 中探测发现了一颗围双星绕转的褐矮星第三天体。 我们的观测结果表明，在这颗褐矮星的轨道之外还有可能存在另外一颗亚恒星 天体在围绕双星运转。 |
| 英文摘要 | According to the mass of the white dwarf component, a subgroup of close binary systems, namely the massive white-dwarf binaries, is de?ned in this the- sis. The massive white-dwarf binary is composed of a quite massive (near or larger than 1 M⊙) white dwarf primary and a secondary companion. In the non- degenerated case, the secondary may be a main sequence, red giant, asymptotic branch giant (AGB), or post-AGB. It may be a He star or white dwarf in the de- generated case. In some extreme cases, it is even a neutron star or black hole. In the standard theory, a Carbon/Oxygen (C/O) white dwarf accumulates material from the secondary star and ?nally produces a type Ia supernova (SN Ia) when its mass reaches the Chandrasekhar-mass limit. However, the progenitor system- s of SNe Ia still remain unclear. As commonly believed, SN Ia originates from a close binary system containing a massive C/O white dwarf, which can either accrete mass from a non-degenerated companion or merge with a degenerated component to produce a SN Ia. But, of the massive white-dwarf binary systems, some containing a white dwarf with an adequately high temperature to trigger the ignition of Carbon and Oxygen, may become a Oxygen/Neon/Magnesium (C/Ne/Mg) white dwarf and ultimately collapse as a neutron star. In this thesis, we in principle introduce some di?erent types of the massive white-dwarf binary systems as well as their possible evolutionary ends and the related models. On base of the published literatures and open data, several tens of such kind systems have been collected as a sample, from which six typical massive white-dwarf binaries are selected for the long-term monitoring and de- tailed investigations by using several ground-base telescopes located in China and Argentina. The main results and conclusions of our work are reported as below: 1. In the long-period supersoft X-ray sources V Sge and WX Cen, the analyses of the orbital-period variations suggest that mass transfer from the lobe- ?ll secondary onto the white dwarf sustains in these two systems, which results in the observed long-term decrease of the orbital periods. This is contradictory to the prediction of the wind-driven accretion mechanism. Hence, it is plausible thatWX Cen is not a wind-driven supersoft X-ray source with a low mass ratio (q = M2/M1 < 1) as pointed out in the previous studies. Some acceptable ranges for the basic systemic parameters are obtained from the dynamic analysis on WX Cen. In the short-period supersoft X-ray source V617 Sgr, the O-C diagram shows a long-term increase of the orbital period, revealing the mass transfer in V617 Sgr is driven by the wind-driven accretion mechanism. These supersoft X-ray sources are the most promising candidates of the SNe Ia progenitors 2. The O-C analyses on the long-period nova-like BT Mon and V363 Aur show decreasing variations in their orbital period. The calculated rates of orbital- period variation by gravitational radiation and magnetic breaking are typically smaller than our observed results by 1–2 orders. The period variations hence should be mainly attributed to the mass transfer from the main-sequence com- panions onto the white dwarfs. As the mass transfer from the donors onto the white dwarf primaries sustains, the white dwarfs can grow in mass, and may ?nally evolve into the SNe Ia. The photometric observations and orbital-period analysis of QZ Aur show that high mass-transfer process may persist in this system, and the mass of white dwarf should be very close to that of the main- sequence secondary star. 3. The periodic oscillation components detected in the O-C analyses of BT Mon, V363 Aur and V617 Sgr are more likely caused by the time-travel e?ect via the third body, rather than the applegate mechanism. It is found that the tertiary component in the binary system V617 Sgr may be a low-mass red dwarf, while that in BT Mon and V363 Aur may be a brown dwarf with a mass only a few tens of MJup. 4. |
| 学科主题 | 天文学 |
| 语种 | 中文 |
| 公开日期 | 2016-05-03 |
| 页码 | 116 |
| 源URL | [http://ir.ynao.ac.cn/handle/114a53/5981]  |
| 专题 | 云南天文台_双星与变星研究组 |
| 推荐引用方式 GB/T 7714 | 时光. 大质量白矮星双星的观测研究[D]. 北京. 中国科学院研究生院（云南天文台）. 2014. |
入库方式： OAI收割
来源：云南天文台
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