Tautenburg-Ondrejov radial velocity follow-up for transiting planetary systems of stars with different masses

过去几十年对系外行星的研究表明，行星具有令人惊讶的各种性质，有时与我们所知的太阳系非常不同。它们可以在距离远小于0.1 Au的恒星轨道上运行，也可以在距离大于100 Au的恒星轨道上运行。轨道可以是高度偏心的，以及圆形的。一些行星的密度高于10 gcm-3，而另一些行星的密度远低于1 gcm-3。关键问题是如何解释如此多样的行星特征？虽然很明显，这种多样性的性质必须与行星的形成有关，但行星形成的圆盘的哪些性质与行星形成的结果最相关并不明显。以前的观测表明，盘的质量和寿命取决于宿主星星的质量。因此，可以预期行星的性质将取决于宿主星星的质量，但如何基本上是不知道的，因为以前的研究严重偏向于行星的太阳类恒星。在这个建议中，我们采用了一种新的方法，我们研究行星的恒星质量大于1.3 Msun和行星的恒星质量小于0.5 Msun。我们比较了这两个样本之间行星出现的频率和行星密度，以辨别与绕类太阳恒星运行的行星的差异。作为候选星的来源，我们将使用K2和TESS巡天作为高质量恒星的来源，使用K2、TESS和NGTS巡天的北方候选星作为低质量恒星的来源。由于我们的目标是过境物体，因此在许多情况下可以确定行星的密度。在这个联合DFG/GACR提案的框架内，我们将重点关注来自各种调查的凌日行星候选者的径向速度测量。我们计划的一个关键方面是，我们有独特的访问两个2米望远镜在Ondrejov和陶滕堡。与之前的凌日调查不同，新的凌日发现计划侧重于相对明亮的恒星，因此可以使用装备精良的2米级望远镜进行后续观测。对于大质量的恒星来说，这种独特的望远镜时间是必不可少的，因为许多这样的恒星旋转迅速，因此获得的光谱数量比更高的径向速度精度更重要。对于质量较低的恒星，使用Calar Alto 3.5米望远镜上的CARMENES摄谱仪的可能性是有利的，因为在获得低质量恒星的高精度径向速度观测时，这是一种独特的世界级仪器。作为德国/捷克的联合提案，一个提案提交给DFG（本提案），另一个提交给GACR。

The research of exoplanets in the past decades has shown that planets have a surprisingly large variety of properties sometimes very different from those we know from Solar system. They can orbit stars at distances much less than 0.1 AU, as well as distances larger than 100 AU. The orbits can be highly eccentric, as well as circular. Some planets have densities higher than 10 gcm-3, whereas others have densities much lower than 1 gcm-3. The key question is how to explain such a large variety of planetary characteristics? While it is immediately obvious that this diversity of properties must be related to the formation of the planets, it is not so obvious which properties of the disk from which the planets form are most relevant for the outcome of planet formation. Previous observations have shown that the mass and life-time of the disk depend on the mass of the host star. It can thus be expected that the properties of the planets will depend on the mass of the host star but how that is basically not known, because previous studies were heavily biased towards planets of solar-like stars only. In this proposal we apply a new approach in which we study planets of stars with masses larger than1.3 Msun and planets with stellar masses of less than 0.5 Msun. We compare the frequency of planet occurrence and planet densities between these two samples in order to discern differences with planets orbiting solar-like stars. As sources for candidates we will use the K2, and TESS surveys for the higher-mass stars, and K2, TESS and northern candidates of NGTS surveys for the lower-mass stars. Since our targets are transiting objects, it will be possible in many cases to determine the planet density. In the framework of this joined DFG/GACR proposal, we will focus on the radial-velocity measurements of the transiting planets candidates from various surveys. A key aspect of our program is that we have unique access to the two 2-m telescopes at Ondrejov and Tautenburg. In contrast to previous transit surveys above mentioned new transit finding programs focus on relatively bright stars, so that the follow-up observations can be done with well-equipped 2-m-class telescopes. For the higher-mass stars this unique access to telescope time is essential, because many of these stars rotate rapidly and therefore the number of spectra obtained is more important than a higher radialvelocity accuracy. For the lower-mass stars the possibility of access to CARMENES spectrograph on the Calar Alto 3.5m telescope is advantageous because this is a unique world class instrument when it comes to obtaining high-precision radial-velocity observations of stars with low masses. As a joint German/Czech proposal, one proposal is submitted to the DFG (this one) and the other to the GACR.