Gaps in Protoplanetary Disks as Signatures of Planets: I. Methodology and Validation

We examine the observational consequences of partial gaps being opened by planets in protoplanetary disks. We model the disk using a static alpha-disk model with detailed radiative transfer, parametrizing the shape and size of the partially cleared gaps based on the results of hydrodynamic simulations. Shadowing and illumination by stellar irradiation at the surface of the gap leads to increased contrast as the gap trough is deepened by shadowing and cooling and the far gap wall is puffed up by illumination and heating. In calculating observables, we find that multiple scattering is important and derive an approximation to include these effects. A gap produced by a 200 M_Earth (70 M_Earth) planet at 10 AU can lower/raise the midplane temperature of the disk by up to ~-25/+29% (~-11/+19%) by shadowing in the gap trough and illumination on the far shoulder of the gap. At the distance of Taurus, this gap would be resolvable with ~0.01" angular resolution. The gap contrast is most significant in scattered light and at thermal continuum wavelengths characteristic of the surface temperature, reducing or raising the surface brightness by up to order of magnitude. Since gaps sizes are correlated to planet mass, this is a promising way of finding and determining the masses of planets embedded in protoplanetary disks.Comment: 11 pages, 9 figures. Accepted to Ap

THE SPANNING SET AS A MEASURE OF MOVEMENT VARIABILITY

The variability of an individual’s movement pattern is an increasingly important focus of research in sport and exercise biomechanics. Inter-trial variability of a single variable is typically assessed using mean deviation or coefficient of variation, however, recent alternatives to these have been proposed such as the spanning set technique. This paper presents an investigation into the validity of the spanning set measure. Variability scores using the spanning set were compared against more traditional measures of variability (mean deviation, coefficient of variation and variance ratio). Results indicate that the spanning set is biased towards early-phase variability and may inaccurately describe the overall level of movement variability

Constraints on the Formation of the Planet Around HD188753A

The claimed discovery of a Jupiter-mass planet in the close triple star system HD 188753 poses a problem for planet formation theory. A circumstellar disk around the planet's parent star would be truncated close to the star, leaving little material available for planet formation. In this paper, we attempt to model a protoplanetary disk around HD 188753A using a fairly simple alpha-disk model, exploring a range of parameters constrained by observations of T Tauri-type stars. The disk is truncated to within 1.5 to 2.7 AU, depending on model parameters. We find that the in situ formation of the planet around HD 188753A is implausible.Comment: Accepted version, to appear in ApJ. 23 pages, 5 figures (3 in color