标题： 行星迁移与双伴星：HD 80606b案例 显示英文标题

标题： Planet Migration and Binary Companions: the case of HD 80606b

摘要： 太阳系外行星HD 80606b拥有一个高偏心率（e=0.93）和紧凑轨道（a=0.47天文单位）。我们研究了它如何到达这样的轨道，并且为何迄今为止避免了潮汐圆化的命运。宿主恒星存在的一颗伴星表明，开普勒机制与潮汐耗散可能共同作用，使这颗行星在形成后很久才向内迁移：开普勒振荡会在行星轨道上产生极端偏心率的时期，而这些小近日点距离时期的潮汐耗散会导致轨道逐渐衰减。我们将这种迁移机制称为“开普勒迁移”。它要求初始行星轨道相对于双星轨道具有高度倾斜的角度。对于一颗位于1000天文单位的伴星和初始行星轨道位于5天文单位的情况，所需的最小相对倾角约为85度。我们讨论了从太阳系外行星观测中推断出的潮汐耗散效率。此外，我们还调查了宿主恒星上观测到的速度残差（在移除由行星引起的运动后）的可能解释：如果开普勒迁移起作用，则系统中的第二颗行星在较大的半长轴空间范围内被排除，而HD 80606b在宿主恒星上引起的潮汐效应可能幅度太小。最后，我们讨论了开普勒迁移对其他行星系统的相关性。 显示英文摘要

摘要： The exo-solar planet HD 80606b has a highly eccentric (e=0.93) and tight (a=0.47 AU) orbit. We study how it might arrive at such an orbit and how it has avoided being tidally circularized until now. The presence of a stellar companion to the host star suggests the possibility that the Kozai mechanism and tidal dissipation combined to draw the planet inward well after it formed: Kozai oscillations produce periods of extreme eccentricity in the planet orbit, and the tidal dissipation that occurs during these periods of small pericentre distances leads to gradual orbital decay. We call this migration mechanism the 'Kozai migration'. It requires that the initial planet orbit is highly inclined relative to the binary orbit. For a companion at 1000 AU and an initial planet orbit at 5 AU, the minimum relative inclination required is ~ 85. We discuss the efficiency of tidal dissipation inferred from the observations of exo-planets. Moreover, we investigate possible explanations for the velocity residual (after the motion induced by the planet is removed) observed on the host star: a second planet in the system is excluded over a large extent of semi-major axis space if Kozai migration is to work, and the tide raised on the star by HD 80606b is likely too small in amplitude. Lastly, we discuss the relevance of Kozai migration for other planetary systems.