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arXiv 1202.6199astro-ph.EP
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近凌日系外行星半径的影响因素

Factors Affecting the Radii of Close-in Transiting Exoplanets

B. Enoch, A. Collier Cameron, K. Horne

摘要:

系外行星的半径可能受到各种因素的影响,包括辐射、行星质量和重元素含量。现在已经发现了相当数量的凌日系外行星,其质量、半径、半长轴、宿主恒星金属丰度和恒星有效温度都是已知的。本文利用多元回归模型,对119颗凌日行星在三种不同质量状态下的行星半径与行星平衡温度T_eq、行星质量M_p、恒星金属丰度[Fe/H]、轨道半长轴a和潮汐加热率H_tidal的关系进行了研究。我们确定,加热导致更大的行星半径,正如预期的那样,增加质量导致增加或减少的半径的低质量(<0.5R_J)和高质量(>2.0R_J)的行星,分别(没有质量的影响,在100倍质量的行星),和增加的主恒星金属丰度导致更小的行星半径,表明主恒星金属丰度和行星重元素含量之间的关系。对于土星质量的行星,其半径的拟合公式为log(R_p/R_J)=-0.077+0.450 log(M_p/M_J)-0.314[Fe/H]+0.671 log(a/AU)+0.398 log(T_eq/K)。大质量行星的半径可用log(Rp/RJ)=-2.217+0.856 log(T_eq/K)+0.291 log(a/AU)拟合。大质量行星半径的最佳拟合公式为log(R_p/R_J)=-1.067+0.380 log(T_eq/K)-0.093 log(M_p/M_J)-0.057[Fe/H]+0.019 log(H_tidal/1x 10 ^{20})。这些方程与观测到的半径有很好的拟合,拟合半径与观测半径的平均绝对差为0.11R_J。(0.1-0.5M_J)行星,其半径几乎完全取决于它们的质量和重元素含量,而气态重元素占主导地位的行星质量(0.5-2.0M_J)行星,其半径增加强烈的辐射通量,部分抵消了幂律依赖于轨道分离。

英文摘要:

The radius of an exoplanet may be affected by various factors, including irradiation, planet mass and heavy element content. A significant number of transiting exoplanets have now been discovered for which the mass, radius, semi-major axis, host star metallicity and stellar effective temperature are known. We use multivariate regression models to determine the dependence of planetary radius on planetary equilibrium temperature T_eq, planetary mass M_p, stellar metallicity [Fe/H], orbital semi-major axis a, and tidal heating rate H_tidal, for 119 transiting planets in three distinct mass regimes. We determine that heating leads to larger planet radii, as expected, increasing mass leads to increased or decreased radii of low-mass (<0.5R_J) and high-mass (>2.0R_J) planets, respectively (with no mass effect on Jupiter-mass planets), and increased host-star metallicity leads to smaller planetary radii, indicating a relationship between host-star metallicity and planet heavy element content. For Saturn-mass planets, a good fit to the radii may be obtained from log(R_p/R_J)=-0.077+0.450 log(M_p/M_J)-0.314[Fe/H]+0.671 log(a/AU)+0.398 log(T_eq/K). The radii of Jupiter-mass planets may be fit by log(R_p/R_J)=-2.217+0.856 log(T_eq/K)+0.291 log(a/AU). High-mass planets' radii are best fit by log(R_p/R_J)=-1.067+0.380 log(T_eq/K)-0.093 log(M_p/M_J)-0.057[Fe/H]+0.019 log(H_tidal/1x10^{20}). These equations produce a very good fit to the observed radii, with a mean absolute difference between fitted and observed radius of 0.11R_J. A clear distinction is seen between the core-dominated Saturn-mass (0.1-0.5M_J) planets, whose radii are determined almost exclusively by their mass and heavy element content, and the gaseous envelope-dominated Jupiter-mass (0.5-2.0M_J) planets, whose radii increase strongly with irradiating flux, partially offset by a power-law dependence on orbital separation.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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