538 research outputs found
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
Multi-object and long-slit spectroscopy of very low mass brown dwarfs in the Orion Nebular Cluster
We present the results of an H-and K-band multi-object and long-slit spectroscopic survey of substellar mass candidates in the outer regions of the Orion Nebula Cluster. The spectra were obtained using MOIRCS on the 8.2m Subaru telescope and ISLE on the 1.88m telescope of Okayama Astrophysical Observatory. Eight out of twelve spectra show strong water absorption and we confirm that their effective temperatures are ≤3000K (spectral type ≥M6) from a chi-square fit to synthetic spectra. We plot our sources on an HR diagram overlaid with theoretical isochrones of low-mass objects and identify three new young brown dwarf candidates. One of the three new candidates is a cool object near the brown dwarf and planetary mass boundary. Based on our observations and those of previous studies, we determine the stellar (0.08Peer reviewe
Sub-Arcsecond Near-Infrared Images of Massive Star Formation Region NGC 6334 V
We present high spatial resolution (0\farcs3) polarimetric images in the
and bands and direct images in the and bands of the NGC 6334
V infrared nebulae. The images show complex structures including the
multi-shells and various knots in the nebulae. The appearances and colors of
the eastern and western nebulae differ considerably. Our polarization images
also show differences between the illuminating sources of the nebulae: the
eastern nebula is illuminated by a deeply embedded mid-infrared source, KDJ 4,
and the western nebula by our newly detected near-infrared source, WN-A1. The
degree of polarization of the nebulae is very large, up to 70% at and 60%
at , which is consistent with a single scattering of near-infrared radiation
from each source at the walls of the mass outflows
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
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