PTPS Candidate Exoplanet Host Star Radii Determination with CHARA Array

We propose to measure the radii of the Penn State - Torun Planet Search (PTPS) exoplanet host star candidates using the CHARA Array. Stellar radii estimated from spectroscopic analysis are usually inaccurate due to indirect nature of the method and strong evolutionary model dependency. Also the so-called degeneracy of stellar evolutionary tracks due to convergence of many tracks in the giant branch decreases the precision of such estimates. However, the radius of a star is a critical parameter for the calculation of stellar luminosity and mass, which are often not well known especially for giants. With well determined effective temperature (from spectroscopy) and radius the luminosity may be calculated precisely. In turn also stellar mass may be estimated much more precisely. Therefore, direct radii measurements increase precision in the determination of planetary candidates masses and the surface temperatures of the planets.Comment: 3 pages, 1 figure, in Proceedings IAU Symposium 282: From Interacting Binaries to Exoplanets: Essential Modelling Tools, 2011, eds. M. T. Richards & I. Hubeny, accepted version (2 pages) is available on-line at: http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8544000&fulltextType=RA&fileId=S174392131102736

A Search for Planets with SALT

As the SALT High Resolution Spectrograph completion is nearing we plan to extend the Pennsylvania-Torun Planets Search (PTPS) with HET to the southern hemisphere. Due to overlap of the skies available for both HET and SALT in the declination range (+10, -10) deg some cooperation and immediate follow up is possible. Here we present, as an example, a $\sim$ 1000 star sample of evolved stars for the future SALT Planet Search.Comment: 6 pages, 2 figure

Substellar-mass companions to the K-dwarf BD +14 4559 and the K-giants HD 240210 and BD +20 2457

We present the discovery of substellar-mass companions to three stars by the ongoing Penn State - Toru\' n Planet Search (PTPS) conducted with the 9.2-m Hobby-Eberly Telescope. The K2-dwarf, BD +14 4559, has a 1.5 M$_{J}$ companion with the orbital period of 269 days and shows a non-linear, long-term radial velocity trend, which indicates a possible presence of another planet-mass body in the system. The K3-giant, HD 240210, exhibits radial velocity variations that require modeling with multiple orbits, but the available data are not yet sufficient to do it unambiguously. A tentative, one-planet model calls for a 6.9 M$_J$ planet in a 502-day orbit around the star. The most massive of the three stars, the K2-giant, BD +20 2457, whose estimated mass is 2.8$\pm$1.5 M$_\odot$, has two companions with the respective minimum masses of 21.4 M$_J$ and 12.5 M$_J$ and orbital periods of 380 and 622 days. Depending on the unknown inclinations of the orbits, the currently very uncertain mass of the star, and the dynamical properties of the system, it may represent the first detection of two brown dwarf-mass companions orbiting a giant. The existence of such objects will have consequences for the interpretation of the so-called brown dwarf desert known to exist in the case of solar-mass stars.Comment: 28 pages, 4 tables, 10 figures. Submitted to Ap

Radial velocity measurements of a sample of K-giants with the Hobby-Eberly telescope

We present motivation and initial results of a large RV survey of K giants aimed at a detection of low-mass companions. The survey, performed with the Hobby-Eberly Telescope, utilizes high resolution (60,000) spectra for high precision radial velocity measurements. The primary goal of the survey is the selection of astrometrically stable reference stars for the Extrasolar Planet Interferometric Survey key project to be carried out with the Space Interferometry Mission

A Planet in a 0.6-AU Orbit Around the K0 Giant HD 102272

We report the discovery of one or more planet-mass companions to the K0-giant HD 102272 with the Hobby-Eberly Telescope. In the absence of any correlation of the observed periodicities with the standard indicators of stellar activity, the observed radial velocity variations are most plausibly explained in terms of a Keplerian motion of at least one planet-mass body around the star. With the estimated stellar mass of 1.9M$_\odot$, the minimum mass of the confirmed planet is 5.9M$_J$. The planet's orbit is characterized by a small but nonzero eccentricity of $e$=0.05 and the semi-major axis of 0.61 AU, which makes it the most compact one discovered so far around GK-giants. This detection adds to the existing evidence that, as predicted by theory, the minimum size of planetary orbits around intermediate-mass giants is affected by both planet formation processes and stellar evolution. The currently available evidence for another planet around HD 102272 is insufficient to obtain an unambiguous two-orbit solution.Comment: 10 pages, 5 figure