From: LARRY KLAES (ljk4_at_msn.com)
Date: Fri Dec 23 2005 - 09:22:28 PST
Paper: astro-ph/0512551
Date: Wed, 21 Dec 2005 22:50:05 GMT (155kb)
Title: On the 2:1 Orbital Resonance in the HD 82943 Planetary System
Authors: Man Hoi Lee (UCSB), R. Paul Butler (Carnegie Inst. of Washington),
Debra A. Fischer (SFSU), Geoffrey W. Marcy (UC Berkeley), and Steven S. Vogt
(UCO/Lick)
Comments: 24 pages, including 10 figures; accepted for publication in ApJ
\\
We present an analysis of the HD 82943 planetary system based on a radial
velocity data set that combines new measurements obtained with the Keck
telescope and the CORALIE measurements published in graphical form. We
examine
simultaneously the goodness of fit and the dynamical properties of the
best-fit
double-Keplerian model as a function of the poorly constrained eccentricity
and
argument of periapse of the outer planet's orbit. The fit with the minimum
chi_{nu}^2 is dynamically unstable if the orbits are assumed to be coplanar.
However, the minimum is relatively shallow, and there is a wide range of
fits
outside the minimum with reasonable chi_{nu}^2. For an assumed coplanar
inclination i = 30 deg. (sin i = 0.5), only good fits with both of the
lowest
order, eccentricity-type mean-motion resonance variables at the 2:1
commensurability, theta_1 and theta_2, librating about 0 deg. are stable.
For
sin i = 1, there are also some good fits with only theta_1 (involving the
inner
planet's periapse longitude) librating that are stable for at least 10^8
years.
The libration semiamplitudes are about 6 deg. for theta_1 and 10 deg. for
theta_2 for the stable good fit with the smallest libration amplitudes of
both
theta_1 and theta_2. We do not find any good fits that are non-resonant and
stable. Thus the two planets in the HD 82943 system are almost certainly in
2:1
mean-motion resonance, with at least theta_1 librating, and the observations
may even be consistent with small-amplitude librations of both theta_1 and
theta_2.
\\ ( http://arXiv.org/abs/astro-ph/0512551 , 155kb)
Paper: astro-ph/0512562
Date: Thu, 22 Dec 2005 14:09:32 GMT (311kb)
Title: Resolving the disk rotation of HD 97048 and HD 100546 in the [O I]
6300A
line: evidence for a giant planet orbiting HD 100546
Authors: B. Acke and M.E. van den Ancker
Comments: 13 pages, 8 figures. Accepted for publication in Astronomy &
Astrophysics (28/11/2005)
\\
Aims. We intend to spatially and spectrally resolve the [O I] emission
region
in two nearby Herbig stars.
Methods. We present high-resolution (R = 80,000) VLT/UVES echelle spectra of
the [O I] 6300A line in the Herbig Ae/Be stars HD 97048 and HD 100546. Apart
from the spectral signature, also the spatial extent of the [O I] emission
region is investigated. For both stars, we have obtained spectra with the
slit
positioned at different position angles on the sky.
Results. The [O I] emission region of HD 100546 appears to be coinciding
with
the dust disk, its major axis located at 150+/-11 degrees east of north. The
SE
part of the disk moves towards the observer, while the NW side is
redshifted.
The [O I] emission region rotates counterclockwise around the central star.
For
HD 97048, the position angle of the emission region is 160+/-19 degrees east
of
north, which is the first determination of this angle in the literature. The
southern parts of the disk are blueshifted, the northern side moves away
from
us. Our data support the idea that a gap is present at 10AU in the disk of
HD
100546. Such a gap is likely planet-induced. We estimate the mass and
orbital
radius of this hypothetical companion responsible for this gap to be 20
Jupiter
masses and 6.5 AU respectively.
Conclusions. Based on temporal changes in the [O I] line profile, we
conclude
that inhomogeneities are present in the [O I] emission region of HD 100546.
These ``clumps'' could be in resonance with the suggested companion,
orbiting
the central star in about 11 yr. If confirmed, these observations could
point
to the existence of an object straddling the line between giant planet and
brown dwarf in a system as young as 10 million years.
\\ ( http://arXiv.org/abs/astro-ph/0512562 , 311kb)
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