Context: More than 40 planets have been found around giant stars, revealing a lack of systems orbiting interior to $sim$ 0.6 AU. This observational fact contrasts with the planetary population around solar-type stars and has been interpreted as the r
esult of the orbital evolution of planets due to the interaction with the host star and/or because of a different formation/migration scenario of planets around more massive stars. Aims: We are conducting a radial velocity study of a sample of 166 giant stars aimed at studying the population of close-in planets orbiting post-main sequence stars. METHODS: We have computed precision radial velocities from multi-epoch spectroscopic data, in order to search for planets around giant stars. Results: In this paper we present the discovery of a massive planet around the intermediate-mass giant star HIP,63242. The best keplerian fit to the data lead to an orbital distance of 0.57 AU, an eccentricity of 0.23 and a projected mass of 9.2 mjup. HIP,63242,b is the innermost planet detected around any intermediate-mass giant star and also the first planet detected in our survey.
We describe our procedure to determine effective temperatures, rotational velocities, microturbulent velocities, and chemical abundances in the atmospheres of Sun-like stars. We use independent determinations of iron abundances using the fits to the
observed Fe I and Fe II atomic absorption lines. We choose the best solution from the fits to these spectral features for the model atmosphere that provides the best confidence in the determined log N(Fe), Vt, and vsini. First, we compute the abundance of iron for a set of adopted microturbulent velocities. To determine the most self-consistent effective temperature and microturbulent velocity in any stars atmosphere, we used an additional constraint where we minimise the dependence of the derived abundances of Fe I and Fe II on the excitation potential of the corresponding lines. We analyse the spectra of the Sun and two well known solar type stars, HD1835 and HD10700 to determine their abundances, microturbulent velocity and rotational velocity. For the Sun abundances of elements obtained from the fits of their absorption features agree well enough (+/- 0.1 dex) with the known values for the Sun. We determined a rotational velocity of vsini = 1.6 +/- 0.3 km/s for the spectrum of the Sun as a star. For HD1835 the self-consistent solution for Fe I and Fe II lines log N(Fe)=+0.2 was obtained with a model atmosphere of 5807/4.47/+0.2 andmicroturbulent velocity Vt = 0.75 km/s, and leads to vsini = 7.2 $pm$ 0.5 km/s. For HD10700 the self-consistent solution log N(Fe) = -4.93 was obtained using a model atmosphere of 5383/4.59/-0.6and microturbulent velocity Vt = 0.5 km/s. The Fe I and Fe II lines give rise to a vsini = 2.4 +/- 0.4 km/s. Using the Teff found from the ionisation equilibrium parameters for all three stars, we found abundances of a number of other elements: Ti, Ni, Ca, Si, Cr. ... Abriged.
The detailed study of the exoplanetary systems HD189733 and HD209458 has given rise to a wealth of exciting information on the physics of exoplanetary atmospheres. To further our understanding of the make-up and processes within these atmospheres we
require a larger sample of bright transiting planets. We have began a project to detect more bright transiting planets in the southern hemisphere by utilising precision radial-velocity measurements. We have observed a constrained sample of bright, inactive and metal-rich stars using the HARPS instrument and here we present the current status of this project, along with our first discoveries which include a brown dwarf/extreme-Jovian exoplanet found in the brown dwarf desert region around the star HD191760 and improved orbits for three other exoplanetary systems HD48265, HD143361 and HD154672. Finally, we briefly discuss the future of this project and the current prospects we have for discovering more bright transiting planets.
The paper was withdrawn due to another possible solution to the dataset that is significantly different in nature. This issue will be addressed shortly and clarified with an additional data point.
We have begun a metal-rich planet search project using the HARPS instrument in La Silla, Chile to target planets with a high potential to transit their host star and add to the number of bright benchmark transiting planets. The sample currently consi
sts of 100, bright (7.5 </= V </= 9.5) solar-type stars (0.5 </= B-V </= 0.9) in the southern hemisphere which are both inactive (logRHK </= -4.5) and metal-rich ([Fe/H] >/= 0.1 dex). We determined the chromospheric activity and metallicity status of our sample using high resolution FEROS spectra. We also introduce the first result from our HARPS planet search and show that the radial-velocity amplitude of this star is consistent with an orbiting planetary-mass companion (i.e. Msini < 0.5MJ) with a period of ~5 days. We are currently engaged in follow-up to confirm this signal as a bonafide orbiting planet.
