Effects of Orbital Eccentricity on Extrasolar Planet Transit Detection and Lightcurves

It is shown herein that planets with eccentric orbits are more likely to transit than circularly orbiting planets with the same semimajor axis by a factor of (1-e^2)^{-1}. If the orbital parameters of discovered transiting planets are known, as from follow-up radial velocity observations, then the transit-detected planet population is easily debiased of this effect. The duration of a planet's transit depends upon of its eccentricity and longitude of periastron; transits near periastron are shorter, and those near apoastron last longer, for a given impact parameter. If fitting for the stellar radius with the other transit parameters, this effect causes a systematic error in the resulting measurements. If the stellar radius is instead held fixed at a value measured independently, then it is possible to place a lower limit on the planet's eccentricity using photometry alone. Orbital accelerations cause a difference in the planet's ingress and egress durations that lead to an asymmetry in the transit lightcurve that could be used along with the transit velocity measurement to uniquely measure the planet's eccentricity and longitude of periapsis. However, the effect is too small to be measured with current technology. The habitability of transiting terrestrial planets found by Kepler depends on those planets' orbital eccentricities. While Kepler will be able to place lower limits on those planets' orbital eccentricity, the actual value for any given planet will likely remain unknown.Comment: 8 pages, 6 figures, to appear in PASP 2007 Septembe

On the chemical composition of Titan's dry lakebed evaporites

Titan, the main satellite of Saturn, has an active cycle of methane in its troposphere. Among other evidence for a mechanism of evaporation at work on the ground, dry lakebeds have been discovered. Recent Cassini infrared observations of these empty lakes have revealed a surface composition poor in water ice compared to that of the surrounding terrains --- suggesting the existence of organic evaporites deposits. The chemical composition of these possible evaporites is unknown. In this paper, we study evaporite composition using a model that treats both organic solids dissolution and solvent evaporation. Our results suggest the possibility of large abundances of butane and acetylene in the lake evaporites. However, due to uncertainties of the employed theory, these determinations have to be confirmed by laboratory experiments.Comment: Icarus, in pres

MOST Space Telescope Photometry of the 2010 January Transit of Extrasolar Planet HD80606b

We present observations of the full January 2010 transit of HD80606b from the Canadian microsatellite, Microvariability and Oscillations of Stars (MOST). By employing a space-based telescope, we monitor the entire transit thus limiting systematic errors that result from ground observations. We determine measurements for the planetary radius (R_{p}=0.987\pm0.061R_{Jup}) and inclination (i=89.283^{o}\pm0.024) by constraining our fits with the observed parameters of different groups. Our measured mid-transit time of 2455210.6449\pm0.0034 HJD is consistant with the 2010 Spitzer results and is 20 minutes earlier than predicted by groups who observed the June 2009 transit.Comment: 3 figure

Embedded density functional theory for covalently bonded and strongly interacting subsystems

Embedded density functional theory (e-DFT) is used to describe the electronic structure of strongly interacting molecular subsystems. We present a general implementation of the Exact Embedding (EE) method [J. Chem. Phys. 133, 084103 (2010)] to calculate the large contributions of the nonadditive kinetic potential (NAKP) in such applications. Potential energy curves are computed for the dissociation of Li^+–Be, CH_3–CF_3, and hydrogen-bonded water clusters, and e-DFT results obtained using the EE method are compared with those obtained using approximate kinetic energy functionals. In all cases, the EE method preserves excellent agreement with reference Kohn–Sham calculations, whereas the approximate functionals lead to qualitative failures in the calculated energies and equilibrium structures. We also demonstrate an accurate pairwise approximation to the NAKP that allows for efficient parallelization of the EE method in large systems; benchmark calculations on molecular crystals reveal ideal, size-independent scaling of wall-clock time with increasing system size

Using Satellites to Probe Extrasolar Planet Formation

Planetary satellites are an integral part of the heirarchy of planetary systems. Here we make two predictions concerning their formation. First, primordial satellites, which have an array of distinguishing characteristics, form only around giant planets. If true, the size and duration of a planetary system's protostellar nebula, as well as the location of its snow line, can be constrained by knowing which of its planets possess primordial satellites and which do not. Second, all satellites around terrestrial planets form by impacts. If true, this greatly enhances the constraints that can be placed on the history of terrestrial planets by their satellites' compositions, sizes, and dynamics