The Potential of the Timing Method to Detect Evolved Planetary Systems

The timing method, using either stellar pulsations or eclipse timing of close binaries as a clock, is proving to be an efficient way to detect planets around stars that have evolved beyond the red giant branch. In this article we present a short review of the recent discoveries and we investigate the potential of the timing method using data both from ground-based facilities as well as from the Kepler and CoRoT space missions.Comment: Part of PlanetsbeyondMS/2010 proceedings http://arxiv.org/html/1011.6606v1, Proc. of the workshop on "Planetary Systems beyond the Main Sequence" (Bamberg, 11-14 August 2010), AIPC in press (eds. S. Schuh, H. Drechsel and U. Heber), 15 pages, 5 figure

Asteroseismology and evolution of EHB stars

The properties of the Extreme Horizontal Branch stars are quite well understood, but much uncertainty surrounds the many paths that bring a star to this peculiar configuration. Asteroseismology of pulsating EHB stars has been performed on a number of objects, bringing us to the stage where comparisons of the inferred properties with evolutionary models becomes feasible. In this review I outline our current understanding of the formation and evolution of these stars, with emphasis on recent progress. The aim is to show how the physical parameters derived by asteroseismology can enable the discrimination between different evolutionary models.Comment: 13 pages, 6 figures, invited review to appear in Communications in Asteroseismology vol.159, "Proceedings of the JENAM 2008 Symposium No 4: Asteroseismology and Stellar Evolution

Further progress on solar age calibration

We recalibrate a standard solar model seismologically to estimate the main-sequence age of the Sun. Our procedure differs from what we have done in the past by removing from the observed frequencies the effect of hydrogen ionization and the superadiabatic convective boundary layer. Our preliminary result is $t_\odot=4.63 \pm 0.02$ Gy.Comment: Accepted for publication in Comm. Asteroseis., 2 pages, 1 figur

Challenges for stellar pulsation and evolution theory

During the last few decades, great effort has been made towards understanding hydrodynamical processes which determine the structure and evolution of stars. Up to now, the most stringent constraints have been provided by helioseismology and stellar cluster studies. However, the contribution of asteroseismology becomes more and more important, giving us an opportunity to probe the interiors and atmospheres of very different stellar objects. A variety of pulsating variables allows us to test various parameters of micro- and macrophysics by means of oscillation data. I will review the most outstanding key problems, both observational and theoretical, of which our knowledge can be improved by means of asteroseismology.Comment: Invited talk presented at the JENAM 2008 Symposium No.4 "Asteroseismology and stellar evolution", eds. S. Schuh and G. Handler., Communications in Asteroseismology, 159, in press; 11 pages, 1 figur

News From The Gamma Cephei Planetary System

The Gamma Cephei planetary system is one of the most interesting systems due to several reasons: 1.) it is the first planet candidate detected by precise radial velocity (RV) measurements that was discussed in the literature (Campbell et al. 1988); 2.) it is a tight binary system with a ~ 20AU; and 3.) the planet host star is an evolved K-type star. In Hatzes et al. (2003) we confirmed the presence of the planetary companion with a minimum mass of 1.7 M_Jup at 2 AU. In this paper we present additional eight years of precise RV data from the Harlan J. Smith 2.7 m Telescope and its Tull Coude spectrograph at McDonald Observatory. The 900 d signal, that is interpreted as the presence of the giant planetary companion, is strongly confirmed by adding the new data. We present an updated orbital solution for the planet, which shows that the planet is slightly more massive and the orbit more circular than previous results have suggested. An intensive high-cadence week of RV observations in 2007 revealed that Gamma Cep A is a multi-periodic pulsator. We discuss this issue within the context of searching for additional planets in this system.Comment: Part of PlanetsbeyondMS/2010 proceedings http://arxiv.org/html/1011.660

Spectral Analysis of Mid-IR Excesses of White Dwarfs

In our Spitzer 24 \mu m survey of hot white dwarfs (WDs) and archival Spitzer study of pre-WDs, i.e., central stars of planetary nebulae (CSPNs), we found mid-IR excesses for -15 WDs/pre-WDs. These mid-IR excesses are indicative of the presence of circumstellar dust that could be produced by sub-planetary objects. To further assess the nature of these IR-excesses, we have obtained Spitzer IRS, Gemini NIRI and Michelle, and KPNO 4m echelle spectra of these objects. In this paper we present the analysis of these spectroscopic observations and discuss the nature of these IR excesses.Comment: Part of PlanetsbeyondMS/2010 proceedings http://arxiv.org/html/1011.660