Gifts from Exoplanetary Transits

The discovery of transiting extrasolar planets has enabled us a number of interesting stduies. Transit photometry reveals the radius and the orbital inclination of transiting planets, and thereby we can learn the true mass and the density of respective planets by the combined information of radial velocity measurements. In addition, follow-up observations of transiting planets such as secondary eclipse, transit timing variations, transmission spectroscopy, and the Rossiter-McLaughlin effect provide us information of their dayside temperature, unseen bodies in systems, planetary atmospheres, and obliquity of planetary orbits. Such observational information, which will provide us a greater understanding of extrasolar planets, is available only for transiting planets. Here I briefly summarize what we can learn from transiting planets and introduce previous studies.Comment: 6 pages, 2 figures, Proceedings of the 2nd Subaru International Conference "Exoplanets and Disks: Their Formation and Diversity" Keauhou - Hawaii - USA, 9-12 March 200

Initial Conditions of Planet Formation: Lifetimes of Primordial Disks

The statistical properties of circumstellar disks around young stars are important for constraining theoretical models for the formation and early evolution of planetary systems. In this brief review, I survey the literature related to ground-based and Spitzer-based infrared (IR) studies of young stellar clusters, with particular emphasis on tracing the evolution of primordial (``protoplanetary'') disks through spectroscopic and photometric diagnostics. The available data demonstrate that the fraction of young stars with optically thick primordial disks and/or those which show spectroscopic evidence for accretion appears to approximately follow an exponential decay with characteristic time ~2.5 Myr (half-life = 1.7 Myr). Large IR surveys of ~2-5 Myr-old stellar samples show that there is real cluster-by-cluster scatter in the observed disk fractions as a function of age. Recent Spitzer surveys have found convincing evidence that disk evolution varies by stellar mass and environment (binarity, proximity to massive stars, and cluster density). Perhaps most significantly for understanding the planeticity of stars, the disk fraction decay timescale appears to vary by stellar mass, ranging from ~1 Myr for >1.3 Msun stars to ~3 Myr for <0.08 Msun brown dwarfs. The exponential decay function may provide a useful empirical formalism for estimating very rough ages for YSO populations and for modeling the effects of disk-locking on the angular momentum of young stars.Comment: 8 pages, 1 figure, invited review, Proceedings of the 2nd Subaru International Conference "Exoplanets and Disks: Their Formation and Diversity", Keauhou - Hawaii - USA, 9-12 March 200

Homogeneous comparison of planet candidates imaged directly until 2008

We present a compilation of the planet candidates currently known from direct imaging. We have gathered available data from the literature and derive the luminosity of all candidates in a homogeneous way using a bolometric correction, the distances and the K band magnitudes of the objects. In a final step we find the masses of the candidates from a comparison of the luminosity or, if not available, an absolute brightness and several well known hot-start evolutionary models.Comment: 4 pages, 1 figure, Proceedings of the 2nd Subaru International Conference on Exoplanets and Disks: Their Formation and Diversity, Keauhou - Hawaii - USA, 9-12 March 2009; 2nd version: Several typos correcte

A Short Guide to Debris Disk Spectroscopy

Multi-wavelength spectroscopy can be used to constrain the dust and gas properties in debris disks. Circumstellar dust absorbs and scatters incident stellar light. The scattered light is sometimes resolved spatially at visual and near-infrared wavelengths using high contrast imaging techniques that suppress light from the central star. The thermal emission is inferred from infrared through submillimeter excess emission that may be 1-2 orders of magnitude brighter than the stellar photosphere alone. If the disk is not spatially resolved, then the radial distribution of the dust can be inferred from Spectral Energy Distribution (SED) modeling. If the grains are sufficiently small and warm, then their composition can be determined from mid-infrared spectroscopy. Otherwise, their composition may be determined from reflectance and/or far-infrared spectroscopy. Atomic and molecular gas absorb and resonantly scatter stellar light. Since the gas is believed to be secondary, detailed analysis analysis of the gas distribution, kinematics, and composition may also shed light on the dust composition and processing history.Comment: 6 pages, 2nd Subaru International Conference on Exoplanets and Disks: Their Formation and Diversity, Keauhou - Hawaii, 9-12 March 200

The Subaru Coronagraphic Extreme AO project

High contrast coronagraphic imaging is a challenging task for telescopes with central obscurations and thick spider vanes, such as the Subaru Telescope. Our group is currently assembling an extreme AO bench designed as an upgrade for the newly commissionned coronagraphic imager instrument HiCIAO, that addresses these difficulties. The so-called SCExAO system combines a high performance PIAA coronagraph to a MEMS-based wavefront control system that will be used in complement of the Subaru AO188 system. We present and demonstrate good performance of two key optical components that suppress the spider vanes, the central obscuration and apodize the beam for high contrast coronagraphy, while preserving the throughput and the angular resolution.Comment: 4 pages, 2nd Subaru International Conference on Exoplanets and Disks: Their Formation and Diversity, Keauhou - Hawaii, 9-12 March 200

An Innovative Method to Identify Autoantigens Expressed on the Endothelial Cell Surface: Serological Identification System for Autoantigens Using a Retroviral Vector and Flow Cytometry (SARF)

Autoantibodies against integral membrane proteins are usually pathogenic. Although anti-endothelial cell antibodies (AECAs) are considered to be critical, especially for vascular lesions in collagen diseases, most molecules identified as autoantigens for AECAs are localized within the cell and not expressed on the cell surface. For identification of autoantigens, proteomics and expression library analyses have been performed for many years with some success. To specifically target cell-surface molecules in identification of autoantigens, we constructed a serological identification system for autoantigens using a retroviral vector and flow cytometry (SARF). Here, we present an overview of recent research in AECAs and their target molecules and discuss the principle and the application of SARF. Using SARF, we successfully identified three different membrane proteins: fibronectin leucine-rich transmembrane protein 2 (FLRT2) from patients with systemic lupus erythematosus (SLE), intercellular adhesion molecule 1 (ICAM-1) from a patient with rheumatoid arthritis, and Pk (Gb3/CD77) from an SLE patient with hemolytic anemia, as targets for AECAs. SARF is useful for specific identification of autoantigens expressed on the cell surface, and identification of such interactions of the cell-surface autoantigens and pathogenic autoantibodies may enable the development of more specific intervention strategies in autoimmune diseases

Gas accretion by planetary cores

We present accretion rates obtained from three-dimensional self-gravitating radiation hydrodynamical models of giant planet growth. We investigate the dependence of accretion rates upon grain opacity and core/protoplanet mass. The accretion rates found for low mass cores are inline with the results of previous one-dimensional models that include radiative transfer.Comment: To be published in American Institute of Physics; Conference proceedings - Exoplanets and Disks: Their Formation and Diversity. 4 pages, 3 figure

Anachronistic Grain Growth and Global Structure of the Protoplanetary Disk Associated with the Mature Classical T Tauri Star, PDS 66

We present ATCA interferometric observations of the old (13 Myr), nearby (86pc) classical T Tauri star, PDS 66. Unresolved 3 and 12 mm continuum emission is detected towards PDS 66, and upper limits are derived for the 3 and 6 cm flux densities. The mm-wave data show a spectral slope flatter than that expected for ISM-sized dust particles, which is evidence of grain growth. We also present HST/NICMOS 1.1 micron PSF-subtracted coronagraphic imaging of PDS 66. The HST observations reveal a bilaterally symmetric circumstellar region of dust scattering about 0.32% of the central starlight, declining radially in surface brightness. The light-scattering disk of material is inclined 32 degrees from face-on, and extends to a radius of 170 AU. These data are combined with published optical and longer wavelength observations to make qualitative comparisons between the median Taurus and PDS 66 spectral energy distributions (SEDs). By comparing the near-infrared emission to a simple model, we determine that the location of the inner disk radius is consistent with the dust sublimation radius (1400 K at 0.1 AU). We place constraints on the total disk mass using a flat-disk model and find that it is probably too low to form gas giant planets according to current models. Despite the fact that PDS 66 is much older than a typical classical T Tauri star (< 5 Myr), its physical properties are not much different.Comment: 31 pages, 7 figure