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

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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.