From: LARRY KLAES (ljk4_at_msn.com)
Date: Wed Jun 29 2005 - 09:22:12 PDT
Paper: astro-ph/0506669
Date: Mon, 27 Jun 2005 20:32:22 GMT (883kb)
Title: Signatures of Planets in Spatially Unresolved Disks
Authors: A. Moro-Martin, S. Wolf and R. Malhotra
Comments: 40 pages (pre-print form), including 16 figures. Published in ApJ
2005
Journal-ref: ApJ, 621, 1079 (2005)
\\
Main sequence stars are commonly surrounded by debris disks, composed of
cold
dust continuously replenished by a reservoir of undetected dust-producing
planetesimals. In a planetary system with a belt of planetesimals (like the
Solar System's Kuiper Belt) and one or more interior giant planets, the
trapping of dust particles in the mean motion resonances with the planets
can
create structure in the dust disk, as the particles accumulate at certain
semimajor axes. Sufficiently massive planets may also scatter and eject dust
particles out of a planetary system, creating a dust depleted region inside
the
orbit of the planet. In anticipation of future observations of spatially
unresolved debris disks with the Spitzer Space Telescope, we are interested
in
studying how the structure carved by planets affects the shape of the disk's
spectral energy distribution (SED), and consequently if the SED can be used
to
infer the presence of planets. We numerically calculate the equilibrium
spatial
density distributions and SEDs of dust disks originated by a belt of
planetesimals in the presence of interior giant planets in different
planetary
configurations, and for a representative sample of chemical compositions.
The
dynamical models are necessary to estimate the enhancement of particles near
the mean motion resonances with the planets, and to determine how many
particles drift inside the planet's orbit. Based on the SEDs and predicted
$\it{Spitzer}$ colors we discuss what types of planetary systems can be
distinguishable from one another and the main parameter degeneracies in the
model SEDs.
\\ ( http://arXiv.org/abs/astro-ph/0506669 , 883kb)
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Paper: astro-ph/0506674
Date: Mon, 27 Jun 2005 21:38:11 GMT (698kb)
Title: Dust outflows and inner gaps generated by massive planets in debris
disks
Authors: A. Moro-Martin and R. Malhotra
Comments: 32 pages (pre-print format), including 12 figures. Accepted to ApJ
(2005). Due to space constrains Fig. 3-6 are at very low resolution
\\
Main sequence stars are commonly surrounded by debris disks, formed by cold
far-IR-emitting dust that is thought to be continuously replenished by a
reservoir of undetected dust-producing planetesimals. We have investigated
the
orbital evolution of dust particles in debris disks harboring massive
planets.
Small dust grains are blown out by radiation pressure, as is well known; in
addition, gravitational scattering by the giant planets also creates an
outflow
of large grains. We describe the characteristics of this large-particle
outflow
in different planetary architectures and for different particle sizes. In
addition, the ejection of particles is responsible for the clearing of dust
inside the orbit of the planet. We study the efficiency of particle ejection
and the resulting dust density contrast inside and outside the orbit of the
planet, as a function of the planet's mass and orbital elements and the
particle size. We discuss its implications for exo-planetary debris disks
and
for the interpretation of in-situ dust detection experiments on space probes
traveling in the outer solar system.
\\ ( http://arXiv.org/abs/astro-ph/0506674 , 698kb)
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Paper: astro-ph/0506675
Date: Mon, 27 Jun 2005 21:47:59 GMT (376kb)
Title: Photometric Accretion Signatures Near the Substellar Boundary
Authors: Peregrine M. McGehee (1 and 2), Andrew A. West (3), J. Allyn Smith
(1
and 4), Kurt S. J. Anderson (2 and 5), J. Brinkmann (5) ((1) LANL, (2) NMSU,
(3) Univ. Washington, (4) Univ. Wyoming, (5) APO)
Comments: 37 pages, 14 figures, accepted by AJ
Report-no: LA-UR-05-4737
\\
Multi-epoch imaging of the Orion equatorial region by the Sloan Digital Sky
Survey has revealed that significant variability in the blue continuum
persists
into the late-M spectral types, indicating that magnetospheric accretion
processes occur below the substellar boundary in the Orion OB1 association.
We
investigate the strength of the accretion-related continuum veiling by
comparing the reddening-invariant colors of the most highly variable stars
against those of main sequence M dwarfs and evolutionary models. A gradual
decrease in the g band veiling is seen for the cooler and less massive
members,
as expected for a declining accretion rate with decreasing mass. We also see
evidence that the temperature of the accretion shock decreases in the very
low
mass regime, reflecting a reduction in the energy flux carried by the
accretion
columns. We find that the near-IR excess attributed to circumstellar disk
thermal emission drops rapidly for spectral types later than M4. This is
likely
due to the decrease in color contrast between the disk and the cooler
stellar
photosphere. Since accretion, which requires a substantial stellar magnetic
field and the presence of a circumstellar disk, is inferred for masses down
to
0.05 Msol we surmise that brown dwarfs and low mass stars share a common
mode
of formation.
\\ ( http://arXiv.org/abs/astro-ph/0506675 , 376kb)
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Paper: astro-ph/0506703
Date: Tue, 28 Jun 2005 18:22:11 GMT (319kb)
Title: Dynamical models of Kuiper Belt dust in the inner and outer Solar
System
Authors: Amaya Moro-Martin and Renu Malhotra
Comments: 25 pages (pre-print format), including 5 figures. Published in AJ
(2003)
Journal-ref: AJ, 125, 2255 (2003)
\\
We report several results related to the dynamical evolution of dust
produced
in the Kuiper Belt (KB). We show that its particle size frequency
distribution
in space is greatly changed from the distribution at production, as a
results
of the combined effects of radiation forces and the perturbations of the
planets. We estimate the contribution of KB dust to the zodiacal cloud by
calculating the radial profile of its number density near the ecliptic. We
also
study the contribution of KB dust to the population of interplanetary dust
particles (IDPs) collected at Earth, by calculating geocentric encounter
velocities and capture rates. Our models show, in contrast with previous
studies, that KB dust grains on Earth-crossing orbits have high
eccentricities
and inclinations and, therefore, their encounter velocities are similar to
those of cometary grains and not to asteroidal grains. We estimate that at
most
25% in number of captured IDPs have cometary or KB origin; the KB
contribution
may be as low as 1%-2%. We present the velocity field of KB dust throughout
the
solar system; this, together with the number density radial profile, is
potentially useful for planning spacecraft missions to the outer solar
system.
\\ ( http://arXiv.org/abs/astro-ph/0506703 , 319kb)
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Paper: astro-ph/0504123
replaced with revised version Tue, 28 Jun 2005 02:58:47 GMT (20kb)
Title: On the Size Distribution of Close-In Extrasolar Giant Planets
Authors: B. Scott Gaudi (CfA)
Comments: 5 pages, 2 figures. Accepted to ApJL. Updated relative to final
ApJL
version to include revised radius of OGLE-TR-10 from Holman et al.,
http://arxiv.org/abs/astro-ph/0506569
The precisions of extrasolar planet radius measurements are reaching the
point at which meaningful and discriminatory comparisons with theoretical
predictions are can be made. However, care must be taken to account for
selection effects in the transit surveys that detect the transiting planets
for which radius measurements are possible. Here I identify one such
selection effect, such that the number of planets with radius R_p detected
in a signal-to-noise ratio limited transit survey is proportional to
R_p^alpha, with alpha~4-6. In the presence of a dispersion sigma in the
intrinsic distribution of planet radii, this selection effect translates to
bias b in the radii of observed planets. Detected planets are, on average,
larger by a fractional amount b ~ alpha (sigma/<R>)^2 relative to the mean
radius <R> of the underlying distribution. I argue that the intrinsic
dispersion in planetary radii is likely to be in the range sigma =
(0.05-0.13)R_J, where the lower bound is that expected theoretically solely
from the variance in stellar insolation, and the upper bound is the 95% c.l.
upper limit from the scatter in observed radii. Assuming an arbitrary but
plausible value of sigma/<R>~10%, and thus b~6%, I infer a mean intrinsic
radius of close-in massive extrasolar planets of <R>=(1.03+/-0.01)R_J. This
value reinforces the case for HD209458b having an anomalously large radius,
and may be inconsistent with coreless models of irradiated giant planets.
\\ ( http://arXiv.org/abs/astro-ph/0504123 , 20kb)
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