Spectroscopy of A-type-stars
Abstract
[abridged version]The hunt for extrasolar planets focussed on solar-type host stars and was recently extended very successfully to low mass main-sequence stars such as Proxima Centauri. Stars more massive than the sun have attracted less attention because the spectroscopic detection methods for late-type fail for early type stars, limiting the possible detections to massive planets and brown dwarfs in tight orbits around their hosts. However, finding planets around intermediate mass stars is crucial to understand the formation of planets in general and the evolution of such systems. Numerical models predict that the mass of the protoplanetary disk increases with the mass of the host star but its life time decreases. Thus more massive, intermediate-mass stars are perfect objects to test theories about the formation of close-in planets. Therefore a collaborative project between the Thüringer Landessternwarte (TLS) led by Dr. Eike Günther and the Bamberg team funded by the DFG was initiated, to start a convenient program to investigate candidates for transiting substellar companions to B-, A-, and early F-type stars found by the CoRoT mission. At the start of the mission, only one single planet around a main-sequence A-type star (WASP33 b) was known, until today only three additional ones have been found. We began with a first spectral characterization for intermediate-mass-stars, using the EXODAT database of the CoRoT mission. Our target list was derived from an automated reclassification of the targets with template spectra taken at the Australian Astronomical Telescope, carried out at TLS. The list was restricted to systems with orbital periods of less than six days and sufficiently shallow transit depth (< 1.5 %), which led to a final target list of about 100 systems. A detailed analysis of the light curves further restricted that list to about 20 targets, for which spectroscopic follow up observations were performed. On the one hand, to obtain radial velocity measurements to exclude stellar companions which would give large amplitude variations, and on the other hand, to excerpt high quality spectra for a detailed spectroscopic analysis, that allows us to better constrain the stellar parameters and thus also the physical properties of the companion.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- March 2018
- Bibcode:
- 2018PhDT.......103H
- Keywords:
-
- spectroscopy;
- A-type-stars;
- exoplanets