Transiting planets of intermediate-mass stars

与类太阳恒星的行星相比，对中等质量（1.3-2.1 Msun）恒星的行星知之甚少。虽然众所周知，中等质量恒星可能有长轨道周期的行星，但不知道它们是否也有像太阳一样短轨道周期的行星。有趣的是，这些恒星的盘的寿命是低质量恒星的一半。因此，如果我们探测到这些恒星附近的行星，我们就知道这些行星一定是在这段时间内形成并向内迁移的。我们从CoRoT数据库中选择了轨道周期为4天或更短的凌日行星候选者。对于这些候选者，我们已经知道有一个凌日天体。然而，我们不知道这个物体是一颗低质量的星星、褐矮星还是行星。只有径向速度测量才能很好地说明这一点。在过去的一年中，我们已经获得了光谱与CAFE摄谱仪在2.2米望远镜的卡拉尔阿尔托。我们发现了一些质量在星星和棕矮星之间的天体，以及质量如此之低的伴星，需要更多的光谱才能确定它们的性质。因此，我们在同一台望远镜上申请了更多的观测时间，以确定这些物体的质量。在Calar Alto项目的同时，我们还获得了ESO的观测时间，在此期间我们发现了一颗褐矮星和一颗行星。一旦调查完成，我们将知道这些恒星的近距离凌日行星的频率是多少，以及它们是否平均具有比太阳类恒星行星更高的质量和密度，正如理论预测的那样。

In contrast to planets of solar-like stars, very little is known about planets of intermediate mass (1.3-2.1 Msun) stars. Although it is well known that intermediate-mass stars can have planets with long orbital periods, it is not know whether they have also have planets with short orbital periods, like solar-like stars. The interesting aspect is that the lifetime of the disks of these stars is half as long as that of lower-mass stars. Thus, if we detect close-in planets of such stars we know the planets must have formed and migrated inwards within this time. We selected transiting planet candidates from the CoRoT-database, which have orbital periods of 4 days or less. For these candidates we already know that there is a transiting object. However, we do not know whether this objects is a low-mass star, a brown dwarf or a planet. Only radial-velocity measurements well tell that. In the previous year, we have obtained spectra with the CAFE-spectrograph at the 2.2m telescope on Calar Alto. We found serval objects with masses in the range between the star and a brown-dwarf, and companions with such low-mass that more spectra are needed in order to determine their nature. We thus applied for more observing time on the same telescope in order to determine the masses of these objects. In parallel to the Calar Alto project, we also obtained observing time at ESO in which we found one brown dwarf and one planet. Once the survey is completed, we will know what the frequency of close-in transiting planets of such stars is, and whether they have on average a higher mass and density than planets of solar-like stars, as predicted by theory.