15,663 research outputs found
ARES+MOOG - a practical overview of an EW method to derive stellar parameters
The goal of this document is to describe the important practical aspects in
the use of an Equivalent Width (EW) method for the derivation of spectroscopic
stellar parameters. A general description of the fundamental steps composing
any EW method is given, together with possible differences that may be found in
different methods used in the literature. Then ARES+MOOG is then used as an
example where each step of the method is described in detail. A special focus
is given for the specific steps of this method, namely the use of a
differential analysis to define the atomic data for the adopted line list, the
automatic EW determinations, and the way to find the best parameters at the end
of the procedure. Finally, a practical tutorial is given, where we focus on
simple exercises useful to illustrate and explain the dependence of the
abundances with the assumed stellar parameters. The interdependences are
described and a clear procedure is given to find the "final" stellar
parameters.Comment: 15 pages, 4 figures, accepted for publication as a chapter in
"Determination of Atmospheric Parameters of B, A, F and G Type Stars",
Springer (2014), eds. E. Niemczura, B. Smalley, W. Pyc
Scale insects (Hemiptera: Coccoidea) of ornamental plants from Sao Carlos, Sao Paulo, Brazil
A list of 35 scale insects collected from 72 ornamental plant species in Sao Carlos, Sao Paulo, Brazil is provided. Regarding host specificity, 30 scale insects were polyphagous, 4 oligophagous, and 1 monophagous. A total of 102 coccoid/plant associations are recorded, 29 of which are new host records for the species; 60 are new host records for the species in Brazil. Pulvinaria urbicola Cockerell, 1893 (Coccidae), Phenacoccus similis Granara de Willink, 1983 (Pseudococcidae), and Orthezia molinarii (Morrison, 1952) (Ortheziidae) are recorded for the first time in Brazil. In addition, we describe the injury caused by scale insects on ornamental plants
From stellar to planetary composition: Galactic chemical evolution of Mg/Si mineralogical ratio
The main goal of this work is to study element ratios that are important for
the formation of planets of different masses. We study potential correlations
between the existence of planetary companions and the relative elemental
abundances of their host stars. We use a large sample of FGK-type dwarf stars
for which precise Mg, Si, and Fe abundances have been derived using HARPS
high-resolution and high-quality data. A first analysis of the data suggests
that low-mass planet host stars show higher [Mg/Si] ratios, while giant planet
hosts present [Mg/Si] that is lower than field stars. However, we found that
the [Mg/Si] ratio significantly depends on metallicity through Galactic
chemical evolution. After removing the Galactic evolution trend only the
difference in the [Mg/Si] elemental ratio between low-mass planet hosts and
non-hosts was present in a significant way. These results suggests that
low-mass planets are more prevalent around stars with high [Mg/Si]. Our results
demonstrate the importance of Galactic chemical evolution and indicate that it
may play an important role in the planetary internal structure and composition.Comment: Accepted by A&A (Letter to the Editor
On the functional form of the metallicity-giant planet correlation
It is generally accepted that the presence of a giant planet is strongly
dependent on the stellar metallicity. A stellar mass dependence has also been
investigated, but this dependence does not seem as strong as the metallicity
dependence. Even for metallicity, however, the exact form of the correlation
has not been established. In this paper, we test several scenarios for
describing the frequency of giant planets as a function of its host parameters.
We perform this test on two volume-limited samples (from CORALIE and HARPS). By
using a Bayesian analysis, we quantitatively compared the different scenarios.
We confirm that giant planet frequency is indeed a function of metallicity.
However, there is no statistical difference between a constant or an
exponential function for stars with subsolar metallicities contrary to what has
been previously stated in the literature. The dependence on stellar mass could
neither be confirmed nor be discarded.Comment: 5 pages, 2 figures, accepted in A&
Orbital and physical properties of planets and their hosts: new insights on planet formation and evolution
We explore the relations between physical and orbital properties of planets
and properties of their host stars to identify the main observable signatures
of the formation and evolution processes of planetary systems. We use a large
sample of FGK dwarf planet hosts with stellar parameters derived in a
homogeneous way from the SWEET-Cat database to study the relation between
stellar metallicity and position of planets in the period-mass diagram. In the
second part we use all the RV-detected planets orbiting FGK stars to explore
the role of planet-disk and planet-planet interaction on the evolution of
orbital properties of planets with masses above 1MJup. We show that planets
orbiting metal-poor stars have longer periods than those in metal-rich systems.
This trend is valid for masses at least from 10MEarth to 4MJup. Earth-like
planets orbiting metal-rich stars always show shorter periods (fewer than 20
days) than those orbiting metal-poor stars. We also found statistically
significant evidence that very high mass giants have on average more eccentric
orbits than giant planets with lower mass.Finally, we show that the
eccentricity of planets with masses higher than 4MJup tends to be lower for
planets with shorter periods. Our results suggest that the planets in the P-MP
diagram are evolving differently because of a mechanism that operates over a
wide range of planetary masses. This mechanism is stronger or weaker depending
on the metallicity of the respective system. One possibility is that planets in
metal-poor disks form farther out from their central star and/or they form
later and do not have time to migrate as far as the planets in metal-rich
systems. The trends and dependencies obtained for very high mass planetary
systems suggest that planet-disk interaction is a very important and
orbit-shaping mechanism for planets in the high-mass domain. Shortened.Comment: 8 pages, 4 figures and 1 table. Accepted for publication in A&
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