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

Red giants from the Pennsylvania - Torun Planet Search

The main goal of the Pennsylvania - Torun Planet Search (PTPS) is detection and characterization of planets around evolved stars using the high-accuracy radial velocity (RV) technique. The project is performed with the 9.2 m Hobby-Eberly Telescope. To determine stellar parameters and evolutionary status for targets observed within the survey complete spectral analysis of all objects is required. In this paper we present the atmospheric parameters (effective temperatures, surface gravities, microturbulent velocities and metallicities) of a subsample of Red Giant Clump stars using strictly spectroscopic methods based on analysis of equivalent widths of Fe I and Fe II lines. It is shown that our spectroscopic approach brings reliable and consistent results.Comment: 3 pages, 2 figures, proceeding of the conference "New Technologies for Probing the Diversity of Brown Dwarfs and Exoplanets" (Shangai, China, July 19-24, 2009), to appear in EPJ Web of Conference

A Search for Cold Dust around Neutron Stars

We present observations of nine radio pulsars using the Heinrich-Hertz-Telescope at \lambda 0.87mm and the IRAM 30-m telescope at \lambda 1.2mm in search for a cold dust around these sources. Five of the program pulsars have been observed for the first time at the mm-wavelengths. The results are consistent with the absence of circumpulsar disks that would be massive enough ($\ge 0.01 M_{\odot}$) to support planet formation according to the scenarios envisioned for solar-type stars, but they do not exclude lower mass ($\le 10-100 M_{\oplus}$) disks for a wide range of grain sizes. These conclusions confirm the previously published results and, together with the current lack of further detections of pulsar planets, they suggest that planet formation around neutron stars is not a common phenomenon.Comment: 5 pages, 1 figure, accepted for publication in A&

The Penn State - Torun Centre for Astronomy Planet Search stars. II. Lithium abundance analysis of the Red Giant Clump sample

Using the sample of 348 stars from the PennState-Torun Centre for Astronomy Planet Search, for which uniformly determined atmospheric parameters are available, with chemical abundances and rotational velocities presented here, we investigate various channels of Li enrichment in giants. Our work is based on the HET/HRS spectra. The A(Li) was determined from the 670.8nm line, while we use a more extended set of lines for alpha-elements abundances. In a series of K-S tests, we compare Li-rich giants with other stars in the sample. We also use available IR photometric and kinematical data in search for evidence of mass-loss. We investigate properties of the most Li-abundant giants in more detail by using multi-epoch precise radial velocities. We present Li and alpha-elements abundances, as well as vsini for 348 stars. We detected Li in 92 stars, of which 82 are giants. 11 of them show significant Li abundance A(Li)>1.4 and 7 of them are Li-overabundant objects, according to criterion of A(Li)>1.5 and their location on HR diagram, including two giants with Li abundances close to meteoritic level. For another 271 stars, upper limits of A(Li) are presented. We show that Li-rich giants are among the most massive stars from our sample and show larger than average effective temperatures. They are indistinguishable from the complete sample in terms of their distribution of luminosity, [Fe/H], vsini, and alpha-elements abundances. Our results do not point out to one specific Li enrichment mechanism operating in our sample of giants. On the contrary, in some cases, we cannot identify fingerprints of any of known scenarios. We show, however, that the 4 most Li-rich giant in our sample either have low-mass companions or have RV variations at the level of ~100 m/s, which strongly suggests that the presence of companions is an important factor in the Li-enrichment processes in giants.Comment: Accepted for publication in A&A, 13 figures, 11 tables, 26 page

Constraining the relative inclinations of the planets B and C of the millisecond pulsar PSR B1257+12

We investigate on the relative inclination of the planets B and C orbiting the pulsar PSR B1257+12 in connection with potential violations of the equivalence principle (Abridged).Comment: LaTex2e, 10 pages, 1 table, 3 figures, 17 references. Small stylistic changes. Version to appear in Journal of Astrophysics and Astronomy (JAA

The Penn State - Toru\'n Planet Search: target characteristics and recent results

More than 450 stars hosting planets are known today but only approximately 30 planetary systems were discovered around stars beyond the Main Sequence. The Penn State-Toru\'n Planet Search, putting an emphasis on extending studies of planetary system formation and evolution to intermediate-mass stars, is oriented towards the discoveries of substellar-mass companions to a large sample of evolved stars using high-precision radial velocity technique. We present the recent status of our survey and detailed characteristic for ~350 late type giant stars, i.e. the new results of radial velocity analysis and stellar fundamental parameters obtained with extensive spectroscopic method. Moreover, in the future we will make an attempt to perform the statistical study of our sample and searching the correlations between the existence of substellar objects and stellar atmospheric parameters according to previous works which investigated the planetary companion impact on the evolution of the host stars.Comment: 7 pages, 5 figures, proceeding of the conference "Planetary Systems beyond the Main Sequence" (Bamberg, Germany, August 11-14, 2010) edited by S. Schuh, H. Drechsel and U. Heber, AIP Conference Series, part of PlanetsbeyondMS/2010 proceedings http://arxiv.org/html/1011.660

The Penn State - Toru\'n Centre for Astronomy Planet Search stars IV. Dwarfs and the complete sample

Our knowledge of the intrinsic parameters of exoplanets is as precise as our determinations of their stellar hosts parameters. In the case of radial velocity searches for planets, stellar masses appear to be crucial. But before estimating stellar masses properly, detailed spectroscopic analysis is essential. With this paper we conclude a general spectroscopic description of the Pennsylvania-Torun Planet Search (PTPS) sample of stars. We aim at a detailed description of basic parameters of stars representing the complete PTPS sample. We present atmospheric and physical parameters for dwarf stars observed within the PTPS along with updated physical parameters for the remaining stars from this sample after the first Gaia data release. We used high resolution (R=60 000) and high signal-to-noise-ratio (S/N=150-250) spectra from the Hobby-Eberly Telescope and its High Resolution Spectrograph. Stellar atmospheric parameters were determined through a strictly spectroscopic local thermodynamic equilibrium analysis (LTE) of the equivalent widths of FeI and FeII lines. Stellar masses, ages, and luminosities were estimated through a Bayesian analysis of theoretical isochrones. We present $T_{eff}$, log$g$ , [Fe/H], micrturbulence velocities, absolute radial velocities, and rotational velocities for 156 stars from the dwarf sample of PTPS. For most of these stars these are the first determinations. We refine the definition of PTPS subsamples of stars (giants, subgiants, and dwarfs) and update the luminosity classes for all PTPS stars. Using available Gaia and Hipparcos parallaxes, we redetermine the stellar parameters (masses, radii, luminosities, and ages) for 451 PTPS stars. The complete PTPS sample of 885 stars is composed of 132 dwarfs, 238 subgiants, and 515 giants, of which the vast majority are of roughly solar mass.Comment: 11 pages, 10 figures, Accepted for publication in Astronomy & Astrophysic

Planets Around the K-Giants BD+20 274 and HD 219415

We present the discovery of planet-mass companions to two giant stars by the ongoing Penn State- Toru\'n Planet Search (PTPS) conducted with the 9.2 m Hobby-Eberly Telescope. The less massive of these stars, K5-giant BD+20 274, has a 4.2 MJ minimum mass planet orbiting the star at a 578-day period and a more distant, likely stellar-mass companion. The best currently available model of the planet orbiting the K0-giant HD 219415 points to a Jupiter-mass companion in a 5.7-year, eccentric orbit around the star, making it the longest period planet yet detected by our survey. This planet has an amplitude of \sim18 m/s, comparable to the median radial velocity (RV) "jitter", typical of giant stars.Comment: 5 figures, 13 pages, accepted by the Astrophysical Journal. arXiv admin note: substantial text overlap with arXiv:1110.164