66 research outputs found
Trojan pairs in the HD 128311 and HD 82943 planetary systems?
Two nearby stars, HD 128311 and HD 82943, are believed to host pairs of
Jupiter-like planets involved in a strong first order 2:1 mean motion resonance
(MMR). In this work we reanalyze available radial velocity (RV) measurements
and demonstrate that it is also possible to explain the observed RV variations
of the parents stars as being induced by a pair of Trojan planets (i.e., in a
1:1 MMR). We show that these Trojan configurations reside in extended zones of
stability in which such systems may easily survive in spite of large masses of
the planets, large eccentricities and nonzero mutual inclinations of their
orbits. We also show that HD 82943 could harbor a previously unknown third
planet about of 0.5 Jupiter masses in 2.1 AU orbit.Comment: 18 pages (total), 17 figures in low resolution format suitable for
arXiv, revised version resubmitted to ApJ. The preprint with high resolution
images is available from
http://www.astri.uni.torun.pl/~chris/astroph.0510109v2.ps.g
The Janus head of the HD 12661 planetary system
In this work we perform a global analysis of the radial velocity curve of the
HD 12661 system. Orbital fits that are obtained by the genetic and gradient
algorithms of minimization reveal the proximity of the system to the 6:1 mean
motion resonance. The orbits are locked in the secular resonance with apsidal
axes librating about 180 deg with the full amplitude . Our
solution incorporates the mutual interaction between the companions. The
stability analysis with the MEGNO fast indicator shows that the system is
located in an extended stable zone of quasi-periodic motions. These results are
different from those obtained on the basis of the orbital fit published by
Fischer et al. (2003)Comment: 7 pages, 5 figures, manuscript submitted to ApJ Letters, revised
versio
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
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