15,717 research outputs found
Parent Stars of Extrasolar Planets. XII. Additional evidence for trends with vsini, condensation temperature, and chromospheric activity
Several recent studies have reported differences in vsini,
abundance-condensation temperature trends, and chromospheric activity between
samples of stars with and without Doppler-detected planets. These findings have
been disputed, and the status of these results remains uncertain. We evaluate
these claims using additional published data and find support for all three.Comment: 4 pages, 4 figures; accepted for publication in MNRAS as a Lette
Are Stars with Planets Polluted?
We compare the metallicities of stars with radial velocity planets to the
metallicity of a sample of field dwarfs. We confirm recent work indicating that
the stars-with-planet sample as a whole is iron rich. However, the lowest mass
stars tend to be iron poor, with several having [Fe/H]<-0.2, demonstrating that
high metallicity is not required for the formation of short period Jupiter-mass
planets. We show that the average [Fe/H] increases with increasing stellar mass
(for masses below 1.25 solar masses) in both samples, but that the increase is
much more rapid in the stars-with-planet sample. The variation of metallicity
with stellar age also differs between the two samples. We examine possible
selection effects related to variations in the sensitivity of radial velocity
surveys with stellar mass and metallicity, and identify a color cutoff
(B-V>0.48) that contributes to but does not explain the mass-metallicity trend
in the stars-with-planets sample. We use Monte Carlo models to show that adding
an average of 6.5 Earth masses of iron to each star can explain both the
mass-metallicity and the age-metallicity relations of the stars-with-planets
sample. However, for at least one star, HD 38529, there is good evidence that
the bulk metallicity is high. We conclude that the observed metallicities and
metallicity trends are the result of the interaction of three effects;
accretion of about 6 Earth masses of iron rich material, selection effects, and
in some cases, high intrinsic metallicity.Comment: 19 pages 11 figure
Length-weight relationships of coral reef fishes from the Alacran Reef, Yucatan, Mexico
Length-weight relationships were computed for 42 species of coral reef fishes from 14 families from the Alacran Reef (Yucatan, Mexico). A total of 1 892 individuals was used for this purpose. The fish species were caught by different fishing techniques such as fishhooks, harpoons, gill and trawl nets. The sampling period was from March 1998 to January 2000
Effective temperatures and radii of planet-hosting stars from IR photometry
In this paper we present and analyse determinations of effective temperatures
of planet-hosting stars using infrared (IR) photometry. One of our goals is the
comparison with spectroscopic temperatures to evaluate the presence of
systematic effects that could alter the determination of metal abundances. To
estimate the stellar temperatures we have followed a new approach based on
fitting the observed 2MASS IR photometry with accurately calibrated synthetic
photometry. Special care has been put in evaluating all sources of possible
errors and incorporating them in the analysis. A comparison of our temperature
determinations with spectroscopic temperatures published by different groups
reveals the presence of no systematic trends and a scatter compatible with the
quoted uncertainties of 0.5-1.3%. This mutual agreement strengthens the results
of both the spectroscopic and IR photometry analyses. Comparisons with other
photometric temperature calibrations, generally with poorer performances, are
also presented. In addition, the method employed of fitting IR photometry
naturally yields determinations of the stellar semi-angular diameters, which,
when combined with the distances, results in estimations of the stellar radii
with remarkable accuracies of ~2-4%. A comparison with the only star in the
sample with an empirically determined radius (HD 209458 -- from transit
photometry) indicates excellent agreement.Comment: 4 pages, 1 figure, accepted for publication as a letter in A&
Asteroseismology of exoplanets host stars: the special case of Horologii (HD17051)
{This paper presents detailed analysis and modelisation of the star HD17051
(alias Hor), which appears as a specially interesting case among
exoplanet host stars. As most of these stars, Hor presents a
metallicity excess which has been measured by various observers who give
different results, ranging from [Fe/H] = 0.11 to 0.26, associated with
different atmospheric parameters. Meanwhile the luminosity of the star may be
determined owing to Hipparcos parallax. Although in the southern hemisphere,
this star belongs to the Hyades stream and its external parameters show that it
could even be one of the Hyades stars ejected during cluster formation. The aim
of this work was to gather and analyse our present knowledge on this star and
to prepare seismic tests for future observations with the HARPS spectrometer
(planned for November 2006).} {We have computed evolutionary tracks with
various metallicities, in the two frameworks of primordial overmetallicity and
accretion. We have concentrated on models inside the error boxes given by the
various observers in the log g - log T diagram. We then computed the
adiabatic oscillation frequencies of these models to prepare future
observations.} {The detailed analysis of Hor presented in this paper
already allowed to constrain its external parameters, mass and age. Some values
given in the literature could be rejected as inconsistent with the overall
analysis. We found that a model computed with the Hyades parameters (age,
metallicity) was clearly acceptable, but other ones were possible too. We are
confident that observations with HARPS will allow for a clear conclusion about
this star and that it will bring important new light on the physics of
exoplanet host stars.}Comment: to be published in Astronomy and Astrophysic
Statistical properties of exoplanets II. Metallicity, orbital parameters, and space velocities
In this article we present a detailed spectroscopic analysis of more than 50
extra-solar planet host stars. Stellar atmospheric parameters and metallicities
are derived using high resolution and high S/N spectra. The spectroscopy
results, added to the previous studies, imply that we have access to a large
and uniform sample of metallicities for about 80 planet hosts stars. We make
use of this sample to confirm the metal-rich nature of stars with planets, and
to show that the planetary frequency is rising as a function of the [Fe/H].
Furthermore, the source of this high metallicity is shown to have most probably
an ``primordial'' source, confirming previous results. The comparison of the
orbital properties (period and eccentricity) and minimum masses of the planets
with the stellar properties also reveal some emerging but still not significant
trends. These are discussed and some explanations are proposed. Finally, we
show that the planet host stars included in the CORALIE survey have similar
kinematical properties as the whole CORALIE volume-limited planet search
sample. Planet hosts simply seem to occupy the metal-rich envelope of this
latter population.Comment: 15 pages, 10 (eps) figures, Astronomy & Astrophysics, in pres
Kinematics of planet-host stars and their relation with dynamical streams in the solar neighbourhood
We present a detailed study on the kinematics of metal-rich stars with and
without planets, and their relation with the Hyades, Sirius and Hercules
dynamical streams in the solar neighbourhood. Accurate kinematics have been
derived for all the stars belonging to the CORALIE planet search survey. We
used precise radial velocity measurements and CCF parameters from the CORALIE
database, and parallaxes, photometry and proper motions from the HIPPARCOS and
Tycho-2 catalogues. The location of stars with planets in the thin or thick
discs has been analysed using both kinematic and chemical constraints. We
compare the kinematic behaviour of known planet-host stars to the remaining
targets belonging to the volume-limited sample, in particular to its metal-rich
population. The high average metallicity of the Hyades stream is confirmed. The
planet-host targets show a kinematic behaviour similar to that of the
metal-rich comparison subsample, rather than to that of the comparison sample
as a whole, thus supporting a primordial origin for the metal excess observed
in stars with known planetary companions. According to the scenarios proposed
as an explanation for the dynamical streams, systems with giant planets could
have formed more easily in metal-rich inner Galactic regions and then been
brought into the solar neighbourhood by dynamical streams.Comment: 14 pages, 12 figures, accepted for publication in A&A (28 August
2006
The metal-rich nature of stars with planets
With the goal of confirming the metallicity "excess" present in stars with
planetary-mass companions, we present in this paper a high-precision
spectroscopic study of a sample of dwarfs included in the CORALIE extrasolar
planet survey. The targets were chosen according to the basic criteria that 1)
they formed part of a limited volume and 2) they did not present the signature
of a planetary host companion. A few stars with planets were also observed and
analysed; namely, HD 6434, HD 13445, HD 16141, HD 17051, HD 19994, HD 22049, HD
28185, HD 38529, HD 52265, HD 190228, HD 210277 and HD 217107. For some of
these objects there had been no previous spectroscopic studies. The
spectroscopic analysis was done using the same technique as in previous work on
the metallicity of stars with planets, thereby permitting a direct comparison
of the results. The work described in this paper thus represents the first
uniform and unbiased comparison between stars with and without planetary-mass
companions in a volume-limited sample. The results show that 1) stars with
planets are significantly metal-rich, and 2) that the source of the metallicity
is most probably "primordial". The results presented here may impose serious
constraints on planetary system formation and evolution models.Comment: 14 pages, 7 figures, A&A in pres
- …