210 research outputs found
About putative Neptune-like extrasolar planetary candidates
We re-analyze the precision radial velocity (RV) data of HD188015, HD114729,
HD190360, HD147513 and HD208487. All these stars are supposed to host Jovian
companions in long-period orbits. We test a hypothesis that the residuals of
the 1-planet model of the RV or an irregular scatter of the measurements about
the synthetic RV curve may be explained by the existence of additional planets
in short-period orbits. We perform a global search for the best fits in the
orbital parameters space with genetic algorithms and simplex method. This makes
it possible to verify and extend the results obtained with an application of
commonly used FFT-based periodogram analysis for identifying the leading
periods. Our analysis confirms the presence of a periodic component in the RV
data of HD190360 which may correspond to a hot-Neptune planet. We found four
new cases when the 2-planet model yields significantly better fits to the RV
data than the best 1-planet solutions. If the periodic variability of the
residuals of single-planet fits has indeed a planetary origin then hot-Neptune
planets may exist in these extrasolar systems. We estimate their orbital
periods in the range of 7-20d and minimal masses about of 20 masses od the
Earth.Comment: Contains 14 pages, 24 figures, 1 table. Accepted for publication in
Astronomy and Astrophysics (4/11/2005). This is a raw unedited manuscript.
Some figures are in low-resolution format suitable for publication in
astro-p
The non-resonant, relativistic dynamics of circumbinary planets
We investigate the non-resonant, 3-D (spatial) model of the hierarchical
system composed of point-mass stellar (or sub-stellar) binary and a low-mass
companion (a circumbinary planet or a brown dwarf). We take into account the
leading relativistic corrections to the Newtonian gravity. The secular model of
the system relies on the expansion of the perturbing Hamiltonian in terms of
the ratio of semi-major axes , averaged over the mean anomalies. We
found that the low-mass object in a distant orbit may excite large eccentricity
of the inner binary when the mutual inclination of the orbits is larger than
about of 60 deg. This is related to strong instability caused by a phenomenon
which acts similarly to the Lidov-Kozai resonance (LKR). The secular system may
be strongly chaotic and its dynamics unpredictable over the long-term time
scale. Our study shows that in the Jupiter-- or brown dwarf-- mass regime of
the low-massive companion, the restricted model does not properly describe the
long-term dynamics in the vicinity of the LKR. The relativistic correction is
significant for the parametric structure of a few families of stationary
solutions in this problem, in particular, for the direct orbits configurations
(with the mutual inclination less than 90 degrees). We found that the dynamics
of hierarchical systems with small may be qualitatively
different in the realm of the Newtonian (classic) and relativistic models. This
holds true even for relatively large masses of the secondaries.Comment: 18 pages, 17 figures, accepted to Monthly Notices of the Royal
Astronomical Societ
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