Precise Estimates of the Physical Parameters for the Exoplanet System HD-17156 Enabled by HST FGS Transit and Asteroseismic Observations

We present observations of three distinct transits of HD 17156b obtained with the Fine Guidance Sensors (FGS) on board the Hubble Space Telescope} (HST). We analyzed both the transit photometry and previously published radial velocities to find the planet-star radius ratio R_p/R_s = 0.07454 +/- 0.00035, inclination i=86.49 +0.24/-0.20 deg, and scaled semi-major axis a/R = 23.19 +0.32/-0.27. This last value translates directly to a mean stellar density determination of 0.522 +0.021/-0.018 g cm^-3. Analysis of asteroseismology observations by the companion paper of Gilliland et al. (2009) provides a consistent but significantly refined measurement of the stellar mean density. We compare stellar isochrones to this density estimate and find M_s = 1.275 +/- 0.018 M_sun and a stellar age of $3.37 +0.20/-0.47 Gyr. Using this estimate of M_s and incorporating the density constraint from asteroseismology, we model both the photometry and published radial velocities to estimate the planet radius R_p= 1.0870 +/- 0.0066 Jupiter radii and the stellar radius R_s = 1.5007 +/- 0.0076 R_sun. The planet radius is larger than that found in previous studies and consistent with theoretical models of a solar-composition gas giant of the same mass and equilibrium temperature. For the three transits, we determine the times of mid-transit to a precision of 6.2 s, 7.6 s, and 6.9 s, and the transit times for HD 17156 do not show any significant departures from a constant period. The joint analysis of transit photometry and asteroseismology presages similar studies that will be enabled by the NASA Kepler Mission.Comment: Accepted for publication to Ap

Metamodel Instance Generation: A systematic literature review

Modelling and thus metamodelling have become increasingly important in Software Engineering through the use of Model Driven Engineering. In this paper we present a systematic literature review of instance generation techniques for metamodels, i.e. the process of automatically generating models from a given metamodel. We start by presenting a set of research questions that our review is intended to answer. We then identify the main topics that are related to metamodel instance generation techniques, and use these to initiate our literature search. This search resulted in the identification of 34 key papers in the area, and each of these is reviewed here and discussed in detail. The outcome is that we are able to identify a knowledge gap in this field, and we offer suggestions as to some potential directions for future research.Comment: 25 page