Understanding planet host stars: testing the limits of stellar spectroscopy
Amanda Doyle
University of Warwick
Determining accurate and precise parameters for exoplanet host stars is crucial for obtaining the planetary parameters, and thus for understanding the habitability of the planets.

The Homogeneous Study of Transiting Systems (HoSTS) aims to characterise planet host stars consistently using a high quality set of stellar spectra. However, even with these spectra there is a limit to how well the parameters can be determined and the limits of 1D LTE spectroscopy are tested in this work.

A common method for determining stellar parameters is to measure a set of iron lines and use these to determine the effective temperature (Teff), surface gravity (log g), microturbulence, and metallicity. It will be shown that even using the same set of spectral lines, it is possible to get different parameters, depending on the exact method used. Many effects are investigated; for example how fixing the surface gravity to an external value will not necessarily improve the parameters, how using atomic data adjusted to the Sun will affect the resulting Teff and log g, and how the excitation balance Teff is extremely sensitive to the inclusion of certain lines.