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arXiv 0909.1752astro-ph.EPastro-ph.SR
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围绕快速旋转恒星运行的太阳系外行星的Transit光变曲线

Transit Lightcurves of Extrasolar Planets Orbiting Rapidly-Rotating Stars

Jason W. Barnes

摘要:

早于光谱型~F6左右的主序星,由于其辐射外部,预计会快速旋转。这种快速的自转导致了一个扁球形的恒星形象。它还导致光球在极处比在赤道处更热(高达几千开尔文),这是由冯·蔡佩尔(1924)首次预测的称为重力暗化的过程的结果。太阳系外行星在这样一个不均匀的扁圆盘上的凌日产生了不寻常的和独特的光变曲线,可以用来确定恒星旋转极和行星轨道法线的相对对齐。这种自旋-轨道对齐可以用来约束行星形成和演化的模型。在与恒星赤道共面的圆盘内,有序的行星形成和迁移将导致自旋轨道对齐。更剧烈的行星-行星散射事件应该会产生自旋-轨道错位的行星。罗西特-麦克劳克林对低质量恒星凌日的测量表明,有些行星是自旋轨道对齐的,有些则不是。由于罗西特-麦克劳克林测量法在快速旋转恒星周围是困难的,光变曲线测光法可能是确定大质量恒星周围行星自旋轨道排列的最佳方法。开普勒任务将在其样本中监测这些恒星中的约10^4颗。任何探测到的行星的光变曲线将使我们能够第一次探测大质量恒星周围的行星形成过程。

英文摘要:

Main-sequence stars earlier than spectral type ~F6 or so are expected to rotate rapidly due to their radiative exteriors. This rapid rotation leads to an oblate stellar figure. It also induces the photosphere to be hotter (by up to several thousand Kelvin) at the pole than at the equator as a result of a process called gravity darkening that was first predicted by von Zeipel (1924). Transits of extrasolar planets across such a non-uniform, oblate disk yield unusual and distinctive lightcurves that can be used to determine the relative alignment of the stellar rotation pole and the planet orbit normal. This spin-orbit alignment can be used to constrain models of planet formation and evolution. Orderly planet formation and migration within a disk that is coplanar with the stellar equator will result in spin-orbit alignment. More violent planet-planet scattering events should yield spin-orbit misaligned planets. Rossiter-McLaughlin measurements of transits of lower-mass stars show that some planets are spin-orbit aligned, and some are not. Since Rossiter-McLaughlin measurements are difficult around rapid rotators, lightcurve photometry may be the best way to determine the spin-orbit alignment of planets around massive stars. The Kepler mission will monitor ~10^4 of these stars within its sample. The lightcurves of any detected planets will allow us to probe the planet formation process around high-mass stars for the first time.

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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