From: LARRY KLAES (ljk4_at_msn.com)
Date: Mon Dec 12 2005 - 09:51:47 PST
Paper: astro-ph/0512245
Date: Fri, 9 Dec 2005 14:31:39 GMT (59kb)
Title: Extrasolar Planets with AMBER/VLTI, What can we expect from current
performances?
Authors: Florentin Millour (LAOG), Martin Vannier (ESO), R. G. Petrov
(LUAN),
Bruno Lopez (LG), Frederik Rantakiro (ESO)
Proxy: ccsd ccsd-00015058
\\
We present the current performances of the AMBER / VLTI instrument in terms
of differential observables (differential phase and differential visibility)
and show that we are already able to reach a sufficient precision for very
low
mass companions spectroscopy and mass characterization. We perform some
extrapolations with the knowledge of the current limitations of the
instrument
facility. We show that with the current setup of the AMBER instrument, we
can
already reach $3\sigma = 10^{-3}$ radians and have the potential to some low
mass companions characterization (Brown dwarves or hypothetical very hot
Extra
Solar Giant Planets). With some upgrades of the VLTI infrastructure,
improvements of the instrument calibration and improvements of the observing
strategy, we will be able to reach $3\sigma = 10^{-4}$ radians and will have
the potential to perform Extra Solar Giant Planets spectroscopy and mass
characterization.
\\ ( http://arXiv.org/abs/astro-ph/0512245 , 59kb)
Paper: astro-ph/0512254
Date: Fri, 9 Dec 2005 17:06:04 GMT (370kb)
Title: The Multiple System HD 27638
Authors: Guillermo Torres (Harvard-Smithsonian Center for Astrophysics)
Comments: 16 pages in 2-column format, including tables and figures. To
appear
in The Astronomical Journal
\\
We report spectroscopic observations of HD 27638B, the secondary in a visual
binary in which the physically associated primary (separation approximately
19
arcsec) is a B9V star. The secondary shows strong Li 6708 absorption
suggesting
youth, and has attracted attention in the past as a candidate post-T Tauri
star
although this has subsequently been ruled out. It was previously known to be
a
double-lined spectroscopic binary (F8+G6) with a period of 17.6 days, and to
show velocity residuals indicating a more distant massive third companion
with
a period of at least 8 years. Based on our radial velocity measurements
covering more than two cycles of the outer orbit, along with other
measurements, we derive an accurate triple orbital solution giving an outer
period of 9.447 +/- 0.017 yr. The third object is more massive than either
of
the other two components of HD 27638B, but is not apparent in the spectra.
We
derive absolute visual magnitudes and effective temperatures for the three
visible stars in HD 27638. Isochrone fitting based on those properties gives
an
age of 200 +/- 50 Myr for the system. We infer also an inclination angle of
about 53.3 degrees for the inner orbit of HD 27638B. We detect a
near-infrared
excess in HD 27638B which we attribute to the third star being a close
binary
composed of late-type stars. This explains its large mass and lack of a
visible
signature. Modeling of this excess allows us to infer not only the masses of
the components of the unseen companion, but also the inclination angle of
the
outer orbit (approximately 73 deg). The HD 27638 system is thus at least
quintuple.
\\ ( http://arXiv.org/abs/astro-ph/0512254 , 370kb)
Astrophysics, abstract
astro-ph/0509508
From: Soko Matsumura [view email]
Date (v1): Fri, 16 Sep 2005 18:07:44 GMT (396kb)
Date (revised v2): Thu, 8 Dec 2005 23:52:40 GMT (396kb)
Dead Zones and Extrasolar Planetary Properties
Authors: Soko Matsumura, Ralph E. Pudritz
Comments: 13 pages, 11 figures, minor changes, accepted for publication in
MNRAS
Most low-mass protostellar disks evolve in clustered environments where they
are affected by external radiation fields, while others evolve in more
isolated star-forming regions. Assuming that the magneto-rotational
instability (MRI) is the main source of viscosity, we calculate the size of
a poorly ionized, MRI inactive, and hence low viscosity region - the "dead
zone" - in these protostellar disks. We include disk ionization by X-rays,
cosmic rays, radioactive elements and thermal collisions, recombination by
molecules, metals, and grains, as well as the effect of turbulence
stimulation in the dead zone by the active layers lying above it. We also
calculate the gap-opening masses of planets, which are determined by a
disk's viscosity and a disk aspect ratio, for disks in these environments
and compare them with each other.
We find that the dead zone is a robust feature of the protostellar disks
that is largely independent of their environment, typically stretching out
to ~ 15 AU. We analyze the possible effects of dead zones on planet
formation, migration, and eccentricity evolution. We show that the
gap-opening mass inside the dead zone is expected to be of the order of
terrestrial and ice giant mass planets while that outside the dead zone is
Jovian or super-Jovian mass planets, largely independent of the star-forming
environment. We show that dead zones can significantly slow down both type I
and type II planetary migration due to their lower viscosity. We also find
that the growth of eccentricity of massive extrasolar planets is
particularly favorable through the planet-disk interaction inside the dead
zones due to the large gaps expected to be opened by planets.
http://arxiv.org/abs/astro-ph/0509508
Paper: astro-ph/0512207
Date: Wed, 7 Dec 2005 22:00:09 GMT (827kb)
Title: Survey for Transiting Extrasolar Planets in Stellar Systems: III. A
Limit on the Fraction of Stars with Planets in the Open Cluster NGC 1245
Authors: Christopher J. Burke (1), B. Scott Gaudi (2), D. L. DePoy (1),
Richard
W. Pogge (1) ((1) The Ohio State University, (2) Harvard-Smithsonian CfA)
Comments: 24 pages, 15 figures, submitted AJ
\\
We analyze a 19-night photometric search for transiting extrasolar planets
in
the open cluster NGC 1245. An automated transit search algorithm with
quantitative selection criteria finds six transit candidates; none are bona
fide planetary transits. We characterize the survey detection probability
via
Monte Carlo injection and recovery of realistic limb-darkened transits. We
use
this to derive upper limits on the fraction of cluster members with close-in
Jupiter-radii, RJ, companions. We carefully analyze the random and
systematic
errors of the calculation. For similar photometric noise and weather
properties
as this survey, observing NGC 1245 twice as long results in a tighter
constraint on "Hot Jupiter", HJ, companions than observing an additional
cluster of similar richness as NGC 1245 for the same length of time as this
survey. This survey observed ~870 cluster members. If 1% of stars have 1.5
RJ
HJ companions, we expect to detect one planet for every 5000 dwarf stars
observed for a month. To reach a ~2% upper limit on the fraction of stars
with
1.5 RJ HJ companions, we conclude a total sample size of ~7400 dwarf stars
observed for at least a month will be needed. Results for 1.0 RJ companions,
without substantial improvement in the photometric precision, will require a
small factor larger sample size.
\\ ( http://arXiv.org/abs/astro-ph/0512207 , 827kb)
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