3,998 research outputs found
AGB Variables and the Mira Period-Luminosity Relation
Published data for large amplitude asymptotic giant branch variables in the
Large Magellanic Cloud are re-analysed to establish the constants for an
infrared (K) period-luminosity relation of the form: Mk=rho[log P-2.38] +
delta. A slope of rho=-3.51+/-0.20 and a zero point of delta=-7.15+/-0.06 are
found for oxygen-rich Miras (if a distance modulus of 18.39+/-0.05 is used for
the LMC). Assuming this slope is applicable to Galactic Miras we discuss the
zero-point for these stars using the revised Hipparcos parallaxes together with
published VLBI parallaxes for OH Masers and Miras in Globular Clusters. These
result in a mean zero-point of delta=-7.25+/-0.07 for O-rich Galactic Miras.
The zero-point for Miras in the Galactic Bulge is not significantly different
from this value.
Carbon-rich stars are also discussed and provide results that are consistent
with the above numbers, but with higher uncertainties. Within the uncertainties
there is no evidence for a significant difference between the period-luminosity
relation zero-points for systems with different metallicity.Comment: 15 pages, 3 figures, accepted for MNRA
Parent Stars of Extrasolar Planets. X. Lithium Abundances and vsini Revisited
We determine Li abundances and vsini values from new spectra of 53 stars with
Doppler-detected planets not included in our previous papers in this series. We
also examine two sets of stars without detected planets, which together serve
as our comparison sample. Using the method of comparison of Li abundances and
vsini values between two sets of stars we introduced in Gonzalez (2008), we
confirm that these two quantities are smaller among stars with planets compared
to stars without detected planets near the solar temperature. The transition
from low to high Li abundance among SWPs occurs near 5850 K, a revision of
about 50 K from our previous determination. The transition from low to high
vsini occurs near 6000 K, but this temperature is not as well constrained.Comment: accepted for publication in MNRAS; 14 pages, 13 figures, 3 table
Tucumã-do-amazonas Astrocaryum tucuma Martius.
Ecologia. Época de flor e fruto. Densidade. Produção. Valor econômico. Uso. Diferenças entre o tucumã-do-amazonas e o tucumã-do-pará. Nutrição. O sanduÃche de tucumã é moda em Manaus. Caça. Inventário de tucumazeiros. Artesanato dos Ãndios Apurinã. Manejo
A unified approach on Springer fibers in the hook, two-row and two-column cases
We consider the Springer fiber over a nilpotent endomorphism. Fix a Jordan
basis and consider the standard torus relative to this. We deal with the
problem to describe the flags fixed by the torus which belong to a given
component of the Springer fiber. We solve the problem in the hook, two-row and
two-column cases. We provide two main characterizations which are common to the
three cases, and which involve dominance relations between Young diagrams and
combinatorial algorithms. Then, for these three cases, we deduce topological
properties of the components and their intersections.Comment: 42 page
Chemical similarities between Galactic bulge and local thick disk red giant stars
The evolution of the Milky Way bulge and its relationship with the other
Galactic populations is still poorly understood. The bulge has been suggested
to be either a merger-driven classical bulge or the product of a dynamical
instability of the inner disk. To probe the star formation history, the initial
mass function and stellar nucleosynthesis of the bulge, we performed an
elemental abundance analysis of bulge red giant stars. We also completed an
identical study of local thin disk, thick disk and halo giants to establish the
chemical differences and similarities between the various populations.
High-resolution infrared spectra of 19 bulge giants and 49 comparison giants in
the solar neighborhood were acquired with Gemini/Phoenix. All stars have
similar stellar parameters but cover a broad range in metallicity. A standard
1D local thermodynamic equilibrium analysis yielded the abundances of C, N, O
and Fe. A homogeneous and differential analysis of the bulge, halo, thin disk
and thick disk stars ensured that systematic errors were minimized. We confirm
the well-established differences for [O/Fe] (at a given metallicity) between
the local thin and thick disks. For the elements investigated, we find no
chemical distinction between the bulge and the local thick disk, which is in
contrast to previous studies relying on literature values for disk dwarf stars
in the solar neighborhood. Our findings suggest that the bulge and local thick
disk experienced similar, but not necessarily shared, chemical evolution
histories. We argue that their formation timescales, star formation rates and
initial mass functions were similar.Comment: Accepted for publication in A&A, 5 page
Contribuições da Pesquisa para o Beneficiamento da Castanha-de-Cutia (Couepia edulis Prance) e Aproveitamento de seus ResÃduos.
bitstream/CNPDIA/10481/1/DOC15_2005.pd
AMBER/VLTI observations of 5 giant stars
While the search for exoplanets around main sequence stars more massive than
the Sun have found relatively few such objects, surveys performed around giant
stars have led to the discovery of more than 30 new exoplanets. The interest in
studying planet hosting giant stars resides in the possibility of investigating
planet formation around stars more massive than the Sun. Masses of isolated
giant stars up to now were only estimated from evolutionary tracks, which led
to different results depending on the physics considered. To calibrate the
theory, it is therefore important to measure a large number of giant star
diameters and masses as much as possible independent of physical models. We aim
in the determination of diameters and effective temperatures of 5 giant stars,
one of which is known to host a planet. AMBER/VLTI observations with the ATs
were executed in low resolution mode on 5 giant stars. In order to measure high
accurate calibrated squared visibilities, a calibrator-star-calibrator
observational sequence was performed. We measured the uniform disk and
limb-darkened angular diameters of 4 giant stars. The effective temperatures
were also derived by combining the bolometric luminosities and the
interferometric diameters. Lower effective temperatures were found when
compared to spectroscopic measurements. The giant star HD12438 was found to
have an unknown companion star at an angular separation of ~ 12 mas. Radial
velocity measurements present in the literature confirm the presence of a
companion with a very long orbital period (P ~ 11.4 years).}Comment: accepted for publication in A&
Study of the impact of the post-MS evolution of the host star on the orbits of close-in planets. I. Sample definition and physical properties
Context: To date, more than 30 planets have been discovered around giant
stars, but only one of them has been found to be orbiting within 0.6 AU from
the host star, in direct contrast to what is observed for FGK dwarfs. This
result suggests that evolved stars destroy/engulf close-in planets during the
red giant phase.
Aims: We are conducting a radial velocity survey of 164 bright G and K giant
stars in the southern hemisphere with the aim of studying the effect of the
host star evolution on the inner structure of planetary systems. In this paper
we present the spectroscopic atmospheric parameters (\Teff, \logg, ,
[Fe/H]) and the physical properties (mass, radius, evolutionary status) of the
program stars. In addition, rotational velocities for all of our targets were
derived.
Methods: We used high resolution and high S/N spectra to measure the
equivalent widths of many Fe{\sc\,i} and Fe{\sc\,ii} lines, which were used to
derive the atmospheric parameters by imposing local thermodynamic and
ionization equilibrium. The effective temperatures and metallicities were used,
along with stellar evolutionary tracks to determine the physical properties and
evolutionary status of each star.
Results: We found that our targets are on average metal rich and they have
masses between \,1.0\,M and 3.5\,M. In addition, we found
that 122 of our targets are ascending the RGB, while 42 of them are on the HB
phase.Comment: Accepted for publication in A&
The debris disk host star HD 61005: a member of the Argus Association?
HD 61005 is a nearby young solar type star that shows a large infrared excess
due to a debris disk. The disk has been recently imaged from ground and space,
with indications of several components. Some characteristics of the disk
suggest the presence of planetary companions around the star, that remain
undetected in deep adaptive optics imaging. For a better understanding of the
system we aim to refine the determination of the stellar parameters, with
emphasis on the stellar age and system orientation. We used ASAS and Hipparcos
photometry and FEROS spectra to determine the rotation period, radial and
rotational velocity, chromospheric emission, effective temperature, and
chemical composition. We find no indication of any misalignment between the
star rotation axis and the disk. The standard age calibrations applied to
several indicators yield an age close to that of the Pleiades (120 Myr);
however the kinematic properties strongly support its membership in the younger
(40 Myr) Argus association, which also includes the IC 2391 open cluster.
Detailed comparison of the properties of HD 61005 and IC 2391 members shows
that the characteristics of HD 61005 are compatible with membership to the
Argus association, once its rather slow rotation is taken into account, because
lithium and other age indicators are somewhat correlated with stellar rotation
at a fixed age. We also identify systematic differences between the field and
cluster population of the Argus association, which are probably selection
effects, so we suggest that additional members with slower rotation and lower
activity level are waiting to be identified.Comment: A&A, in press, 13 pages, 11 figure
Clustering of Luminous Red Galaxies IV: Baryon Acoustic Peak in the Line-of-Sight Direction and a Direct Measurement of H(z)
We study the clustering of LRG galaxies in the latest spectroscopic SDSS data
releases, DR6 and DR7, which sample over 1 Gpc^3/h^3 to z=0.47. The 2-point
correlation function \xisp is estimated as a function of perpendicular
and line-of-sight (radial) directions. We find a significant
detection of a peak at Mpc/h, which shows as a circular ring in
the plane. There is also significant evidence for a peak along the
radial direction whose shape is consistent with its originating from the
recombination-epoch baryon acoustic oscillations (BAO). A \xisp model with no
radial BAO peak is disfavored at , whereas a model with no
magnification bias is disfavored at . The radial data enable, for the
first time, a direct measurement of the Hubble parameter as a function
of redshift. This is independent from earlier BAO measurements which used the
spherically averaged (monopole) correlation to constrain an integral of .
Using the BAO peak position as a standard ruler in the radial direction, we
find: km/s/Mpc for z=0.15-0.30 and
km/s/Mpc for . The first
error is a model independent statistical estimation and the second accounts for
systematics both in the measurements and in the model. For the full sample,
, we find km/s/Mpc.Comment: Minor revision to match version accepted for publication in MNRAS.
Includes comparison to DR7, a Table with the measurements and errors.
Includes extended analysis on systematic errors. Some figures have been
omitted. Main results and conclusions remain unchange
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