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轨道距离对系外行星大气逃逸的影响
Alternative TitleThe Impacts of Orbital Distance on Exoplanetary Atmospheric Escape
杨沫1,2,3; 郭建恒1,2
Source Publication天文学报(Acta Astronomica Sinica)
2016-11
Volume57Issue:6Pages:657-672
DOI10.15940/j.cnki.0001-5245.2016.06.004
ClassificationP185
Contribution Rank第1完成单位
Indexed ByCSCD ; 核心
Keyword流体动力学 行星和卫星:大气 恒星:类太阳星 X射线:恒星
Abstract

大气逃逸是行星大气演化的重要一环,其主要能量来源为主星在高能波段的辐射.辐射流量随轨道距离的增大会急剧下降,不同轨道处的行星大气逃逸差异较大,轨道距离对系外行星大气逃逸的影响需要深入研究.运用一维流体动力学模型,并且考虑辐射转移和多种粒子的光化学反应过程,对行星大气逃逸随轨道距离的变化进行了研究.由于主星光谱在不同的演化阶段会表现出较大差异,故采用XSPEC(X-Ray Spectral Fitting Package)中的等离子体模型APEC(Astrophysical Plasma Emission Code),获得不同年龄的类太阳星光谱作为模型输入光谱.结果发现:不同轨道处的行星逃逸率显著不同,逃逸机制也会随轨道距离的增大由剧烈的流体动力学逃逸转化为缓和的金斯逃逸,且行星引力势越小、恒星-行星系统越年轻,这一转化距离越远.处于年轻恒星-行星系统中的短周期行星,逃逸率和辐射流量的相关性降低.这个结果表明经典的能量限制(Energy-limited)逃逸理论对这类行星是不适用的.这些发现丰富了对系外行星大气逃逸过程的研究,尤其是扩展了在不同轨道距离和恒星年龄条件下,逃逸机制和能量转换过程的研究.

Other Abstract

Driven by the high energy radiation of host stars, atmospheric escape is very important for planet evolution. While the flux drops dramatically with the increase of orbital distance, it is essential to study the impacts of orbital distance on atmospheric escape. We consider the hydrodynamic escape of exoplanets driven by the XUV (X-ray and extreme-ultraviolet) radiation of their host stars. We aim to study the mass-loss rate, the transition of escape mechanism, the structures of temperature and velocity, based on a one-dimensional hydrodynamic model which includes radiative transfer processes and photochemical reactions. As the stellar XUV emission varies with the stellar evolution, we use XSPEC (X-Ray Spectral Fitting Package) to construct the XUV spectra of solar-type stars at different ages. We find that with the increase of orbital distance, the mass-loss rates drop significantly, and when the stellar XUV flux is too small to preserve the hydrodynamic escape, it will turn to Jeans escape. This transition occurs in larger distance for younger and smaller planets. For young planets, hydrodynamic escape can occur in 1–2 au. For very young and close-in planets, the relation between mass-loss rate and stellar flux is not as significant as planets that are not close to their host stars, and the energy-limited equation can lead to large overestimate.

Funding Project国家自然科学基金项目[11273054]
Funding Organization国家自然科学基金项目[11273054]
Language中文
Subject Area天文学 ; 恒星与银河系 ; 恒星物理学 ; 太阳与太阳系 ; 行星物理学
MOST Discipline Catalogue理学 ; 理学::天文学
ISSN0001-5245
CSCD IDCSCD:5872518
Citation statistics
Cited Times:1[CSCD]   [CSCD Record]
Document Type期刊论文
Identifierhttp://ir.ynao.ac.cn/handle/114a53/9836
Collection恒星物理研究组
中国科学院天体结构与演化重点实验室
Affiliation1.中国科学院云南天文台,昆明,650011
2.中国科学院天体结构与演化重点实验室,昆明,650011
3.中国科学院大学,北京,100049
First Author AffilicationYunnan Observatories, Chinese Academy of Sciences
Recommended Citation
GB/T 7714
杨沫,郭建恒. 轨道距离对系外行星大气逃逸的影响[J]. 天文学报(Acta Astronomica Sinica),2016,57(6):657-672.
APA 杨沫,&郭建恒.(2016).轨道距离对系外行星大气逃逸的影响.天文学报(Acta Astronomica Sinica),57(6),657-672.
MLA 杨沫,et al."轨道距离对系外行星大气逃逸的影响".天文学报(Acta Astronomica Sinica) 57.6(2016):657-672.
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