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arXiv 0907.2669astro-ph.EPastro-ph.SR
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第一批CoRoT系外行星的结构和演化：探测棕矮星/行星重叠质量状态

Structure and evolution of the first CoRoT exoplanets: Probing the Brown Dwarf/Planet overlapping mass regime

J. Leconte, I. Baraffe, G. Chabrier, T. Barman, B. Levrard

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6 pages, 5 figures, accepted for publication in Astronomy and Astrophysics
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摘要：

我们提出了详细的结构和演化计算的第一个凌日太阳系外行星发现的天基CoRoT任务。理论半径和观测半径之间的比较提供了关于CoRoT天体内部组成的信息。我们区分了三种不同类型的行星出现在这些发现和以前的地面调查：（i）行星解释的标准行星模型，包括辐射，（ii）异常膨胀的行星和（iii）大质量的物体属于重叠的质量制度之间的行星和褐矮星。对于第二类，我们表明，潮汐加热可以解释相关的CoRoT对象，提供非零偏心率。我们强调，通常在凌日光变曲线分析中所做的潮汐使轨道快速圆化的假设，并不像Levrard等人（2009年）最近所建议的那样是先验合理的，并且应该对某些观测仔细重新进行偏心率分析。最后，特别关注的是CoRoT-3b，并确定其性质：巨行星或褐矮星？这个物体的半径确定证实了理论上对亚恒星区域气态物体质量半径的预测，但是，考虑到目前观测的不确定性，还不能明确地确定它的性质。然而，这为观测识别这两个不同的天体物理群体，褐矮星和巨行星，在它们重叠的质量范围内开辟了道路，就像对8千兆赫质量的物体Hat-P-2b所做的那样。（节略）

英文摘要：

We present detailed structure and evolution calculations for the first transiting extrasolar planets discovered by the space-based CoRoT mission. Comparisons between theoretical and observed radii provide information on the internal composition of the CoRoT objects. We distinguish three different categories of planets emerging from these discoveries and from previous ground-based surveys: (i) planets explained by standard planetary models including irradiation, (ii) abnormally bloated planets and (iii) massive objects belonging to the overlapping mass regime between planets and brown dwarfs. For the second category, we show that tidal heating can explain the relevant CoRoT objects, providing non-zero eccentricities. We stress that the usual assumption of a quick circularization of the orbit by tides, as usually done in transit light curve analysis, is not justified a priori, as suggested recently by Levrard et al. (2009), and that eccentricity analysis should be carefully redone for some observations. Finally, special attention is devoted to CoRoT-3b and to the identification of its very nature: giant planet or brown dwarf ? The radius determination of this object confirms the theoretical mass-radius predictions for gaseous bodies in the substellar regime but, given the present observational uncertainties, does not allow an unambiguous identification of its very nature. This opens the avenue, however, to an observational identification of these two distinct astrophysical populations, brown dwarfs and giant planets, in their overlapping mass range, as done for the case of the 8 Jupiter-mass object Hat-P-2b. (abridged)

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