1,579 research outputs found
High-Resolution Spectroscopy of the Transiting Planet Host Star TrES-1
We report on a spectroscopic determination of the stellar parameters and chemical abundances for the parent star of the transiting planet TrES-1. Based on a detailed analysis of iron lines in our Keck and Hobby-Eberly Telescope spectra, we derive Teff = 5250 ± 75 K, log g = 4.6 ± 0.2, and [Fe/H] = 0.00 ± 0.09. By measuring the Ca II activity indicator and by putting useful upper limits on the Li abundance, we constrain the age of TrES-1 to be 2.5 ± 1.5 Gyr. By comparing theoretical stellar evolution models with the observational parameters, we obtain M* = 0.89 ± 0.05 Mâ and R* = 0.83 ± 0.05 Râ. Our improved estimates of the stellar parameters are utilized in a new analysis of the transit photometry of TrES-1 to derive a mass Mp = (0.76 ± 0.05) MJ a radius RP = 1.04-0.05+0.08RJ, and an inclination i = 89.5-1.3+0.5 deg. The improved planetary mass and radius estimates provide the grounds for new crucial tests of theoretical models of evolution and evaporation of irradiated extrasolar giant planets
S4N: A Spectroscopic Survey of Stars in the Solar Neighborhood
[ABRIDGED] We report the results of a high-resolution spectroscopic survey of
all the stars more luminous than Mv = 6.5 mag within 14.5 pc from the Sun. We
derive stellar parameters and perform a preliminary abundance and kinematic
analysis of the F-G-K stars in the sample. The inferred metallicity ([Fe/H])
distribution is centered at about -0.1 dex, and shows a standard deviation of
0.2 dex.
We identify a number of metal-rich K-type stars which appear to be very old,
confirming the claims for the existence of such stars in the solar
neighborhood. With atmospheric effective temperatures and gravities derived
independently of the spectra, we find that our classical LTE model-atmosphere
analysis of metal-rich (and mainly K-type) stars provides discrepant abundances
from neutral and ionized lines of several metals. Based on transitions of
majority species, we discuss abundances of 16 chemical elements.
In agreement with earlier studies we find that the abundance ratios to iron
of Si, Sc, Ti, Co, and Zn become smaller as the iron abundance increases until
approaching the solar values, but the trends reverse for higher iron
abundances. At any given metallicity, stars with a `low' galactic rotational
velocity tend to have high abundances of Mg, Si, Ca, Sc, Ti, Co, Zn, and Eu,
but low abundances of Ba, Ce, and Nd. The Sun appears deficient by roughly 0.1
dex in O, Si, Ca, Sc, Ti, Y, Ce, Nd, and Eu, compared to its immediate
neighbors with similar iron abundances.Comment: 24 pages, 19 figures, to appear in A&A; data can be accessed from
http://hebe.as.utexas.edu/s4n/ or http://www.astro.uu.se/~s4n
High Resolution Spectroscopy and Spectropolarimetry of some late F-/early G-type sun-like stars as targets for Zeeman Doppler imaging
High resolution spectroscopy and spectropolarimetry have been undertaken at
the Anglo-Australian Telescope in order to identify suitable targets for
magnetic studies of young sun-like stars, for the proxy study of early solar
evolution. This study involved the investigation of some variable late F-/early
G-type sun-like stars originally identified by the Hipparcos mission. Of the 38
stars observed for this study, HIP 31021, HIP 64732, HIP 73780 were found to be
spectroscopic binary stars while HIP 19072, HIP 67651 and HIP 75636 are also
likely to be binaries while HIP 33111 could even be a triple system. Magnetic
fields were detected on a number of the survey stars: HIP 21632, HIP 43720, HIP
48770, HIP 62517, HIP 71933, HIP 77144, HIP 89829, HIP 90899 and HIP 105388,
making these stars good candidates for follow-up Zeeman Doppler imaging
studies.Comment: 16 pages, 16 figures, 4 tables Accepted for publication in PAS
Depicting the battle between nectarine and Monilinia laxa: the fruit developmental stage dictates the effectiveness of the host defenses and the pathogenâs infection strategies
Infections by the fungus Monilinia laxa, the main cause of brown rot in Europe, result in considerable losses of stone
fruit. Herein, we present a comprehensive transcriptomic approach to unravel strategies deployed by nectarine fruit
and M. laxa during their interaction. We used M. laxa-inoculated immature and mature fruit, which was resistant and
susceptible to brown rot, respectively, to perform a dual RNA-Seq analysis. In immature fruit, host responses, pathogen
biomass, and pathogen transcriptional activity peaked at 14â24 h post inoculation (hpi), at which point M. laxa
appeared to switch its transcriptional response to either quiescence or death. Mature fruit experienced an exponential
increase in host and pathogen activity beginning at 6 hpi. Functional analyses in both host and pathogen highlighted
differences in stage-dependent strategies. For example, in immature fruit, M. laxa unsuccessfully employed
carbohydrate-active enzymes (CAZymes) for penetration, which the fruit was able to combat with tightly regulated
hormone responses and an oxidative burst that challenged the pathogenâs survival at later time points. In contrast, in
mature fruit, M. laxa was more dependent on proteolytic effectors than CAZymes, and was able to invest in
filamentous growth early during the interaction. Hormone analyses of mature fruit infected with M. laxa indicated that,
while jasmonic acid activity was likely useful for defense, high ethylene activity may have promoted susceptibility
through the induction of ripening processes. Lastly, we identified M. laxa genes that were highly induced in both
quiescent and active infections and may serve as targets for control of brown rot.info:eu-repo/semantics/publishedVersio
Deliverable D6a: Regional climatic characteristics for the European sites at specific times: the dynamical downscaling. Work Package 2, Simulation of the future evolution of the biosphere system using the hierarchical strategy. Modelling Sequential Biosphere Systems under Climate Change for Radioactive Waste Disposal (BIOCLIM)
The overall aim of BIOCLIM is to assess the
possible long-term impacts due to climate
change on the safety of radioactive waste
repositories in deep formations. This aim is addressed
through the following specific objectives:
âą Development of practical and innovative strategies for
representing sequential climatic changes to the
geosphere-biosphere system for existing sites over
central Europe, addressing the timescale of one
million years, which is relevant to the geological
disposal of radioactive waste.
âą Exploration and evaluation of the potential effects of
climate change on the nature of the biosphere
systems used to assess the environmental impact.
âą Dissemination of information on the new
methodologies and the results obtained from the
project among the international waste management
community for use in performance assessments of
potential or planned radioactive waste repositories.
The BIOCLIM project is designed to advance the
state-of-the-art of biosphere modelling for use in
Performance Assessments. Therefore, two strategies
are developed for representing sequential climatic
changes to geosphere-biosphere systems. The
hierarchical strategy successively uses a hierarchy of
climate models. These models vary from simple 2-D
models, which simulate interactions between a few
aspects of the Earth system at a rough surface
resolution, through General Circulation Model (GCM)
and vegetation model, which simulate in great detail the
dynamics and physics of the atmosphere, ocean and
biosphere, to regional models, which focus on the
European regions and sites of interest. Moreover,
rule-based and statistical downscaling procedures are
also considered. Comparisons are provided in terms of
climate and vegetation cover at the selected times and
for the study regions. The integrated strategy consists
of using integrated climate models, representing all
the physical mechanisms important for long-term
continuous climate variations, to simulate the climate
evolution over many millennia. These results are then
interpreted in terms of regional climatic changes using
rule-based and statistical downscaling approaches.
This deliverable, D6a, focuses on the hierarchical
strategy, and in particular the MAR simulations.
According to the hierarchical strategy developed in
the BIOCLIM project to predict future climate, six
BIOCLIM experiments were run with the MAR model. In
addition to these experiments a baseline experiment,
presenting the present-day climate simulated by MAR,
was also undertaken. In the first step of the hierarchical
strategy the LLN 2-D NH climate model simulated
the gross features of the climate of the next 1 Myr
[Ref.1]. Six snapshot experiments were selected from
these results. In a second step a GCM and a biosphere
model were used to simulate in more detail the climate
of the selected time periods. These simulations were
performed on a global scale [Ref.1]. The third step of
the procedure is to derive the regional features of the
climate at the same time periods. Therefore the results
of the GCM are used as boundary conditions to force
the regional climate model (MAR) for the six selected
periods and the baseline simulation. The control
simulation (baseline) corresponds to the regional
climate simulated under present-day conditions, both
insolation forcing and atmospheric CO2 concentration.
All the BIOCLIM simulations are compared to that
baseline simulation. In addition, other comparisons will
also be presented. Tableau 1 summarises the
characteristics of these BIOCLIM experiments already
presented in [Ref.1] and [Ref.2]
The Spectroscopic Orbit of the Planetary Companion Transiting HD209458
We report a spectroscopic orbit with period P = 3.52433 +/- 0.00027 days for
the planetary companion that transits the solar-type star HD209458. For the
metallicity, mass, and radius of the star we derive [Fe/H] = 0.00 +/- 0.02, M =
1.1 +/- 0.1 solar masses, and R = 1.3 +/- 0.1 solar radii. This is based on a
new analysis of the iron lines in our HIRES template spectrum, and also on the
absolute magnitude and color of the star, and uses isochrones from four
different sets of stellar evolution models. Using these values for the stellar
parameters we reanalyze the transit data and derive an orbital inclination of i
= 85.2 +/- 1.4 degrees. For the planet we derive a mass of Mp = 0.69 +/- 0.05
Jupiter masses, a radius of Rp = 1.54 +/- 0.18 Jupiter radii, and a density of
0.23 +/- 0.08 grams per cubic cm.Comment: 11 pages, 1 figure, 2 tables, LaTex, aastex, accepted for publication
by ApJ Letter
Deliverable D8a: Development of the rule-based downscaling methodology for BIOCLIM Workpackage 3. Work Package 3, Simulation of the future evolution of the biosphere system using the hierarchical strategy. Modelling Sequential Biosphere Systems under Climate Change for Radioactive Waste Disposal (BIOCLIM)
One of the tasks of BIOCLIM WP3 was to develop
a rule-based approach for downscaling from the
MoBidiC model of intermediate complexity (see
Ref.1) in order to provide consistent estimates of
monthly temperature and precipitation for the specific
regions of interest to BIOCLIM (Central Spain, Central
England and Northeast France, together with Germany
and the Czech Republic). Such an approach has been
developed and used in a previous study funded by Nirex
to downscale output from an earlier version of this
climate model covering the Northern Hemisphere only,
LLN 2-D NH, to Central England, and evaluated using
palaeoclimate proxy data and General Circulation
Model (GCM) output for this region. This previous study
[Ref.2] provides the starting point for the BIOCLIM
work.
A statistical downscaling methodology has been
developed by Philippe Marbaix of CEA/LSCE for use
with the second climate model of intermediate
complexity used in BIOCLIM â CLIMBER-GREMLINS
(see Ref.1). This statistical methodology is described
in Deliverable D8b [Ref.3]. Inter-comparisons of all the
downscaling methodologies used in BIOCLIM (including
the dynamical methods applied in WP2 â see Ref.4 and
Ref.5) are discussed in Deliverable D10-12 [Ref.6].
The rule-based methodology assigns climate states or
classes to a point on the time continuum of a region
according to a combination of simple threshold
values which can be determined from the coarse
scale climate model. Once climate states or classes
have been defined, monthly temperature and
precipitation climatologies are constructed using
analogue stations identified from a data base of
present-day climate observations. The most appropriate
climate classification for BIOCLIM purposes is the
KĂžppen/Trewartha scheme (Ref.7 ; see Appendix 1).
This scheme has the advantage of being empirical, but
only requires monthly averages of temperature and
precipitation as input variables
Deliverable D7: Continuous climate evolution scenarios over western Europe (1000 km) scale. Work Package 2, Simulation of the future evolution of the biosphere system using the hierarchical strategy. Modelling Sequential Biosphere Systems under Climate Change for Radioactive Waste Disposal (BIOCLIM)
The overall aim of BIOCLIM is to assess the
possible long term impacts due to climate
change on the safety of radioactive waste
repositories in deep formations. This aim is addressed
through the following specific objectives:
âą Development of practical and innovative strategies
for representing sequential climatic changes to the
geosphere-biosphere system for existing sites over
central Europe, addressing the timescale of one
million years, which is relevant to the geological
disposal of radioactive waste.
âą Exploration and evaluation of the potential effects of
climate change on the nature of the biosphere
systems used to assess the environmental impact.
âą Dissemination of information on the new
methodologies and the results obtained from the
project among the international waste management
community for use in performance assessments of
potential or planned radioactive waste repositories.
A key point of the project is therefore to develop
strategies for representing sequential long-term
climatic changes by addressing time scales of
relevance to geological disposal of solid radioactive
wastes. The integrated strategy, which first step is
described in this deliverable (D7), consists of building
an integrated, dynamic climate model, to represent all
the known important mechanisms for long term
climatic variations. The time-dependent results will then
be interpreted in terms of regional climate using rulebased
and statistical downscaling approaches.
Therefore, the continuous simulation of the climate
evolution of the next 200 000 years selected for study
is a major objective of the BIOCLIM project. This
requires models that account for the simultaneous
evolution of the atmosphere, biosphere, land-ice and
the ocean. To be able to perform several 200 000-yearlong
transient climate simulations, the models have to
include all these components, but also need to be
simple enough to run fast. Therefore, climate models of
intermediate complexity have been chosen to complete
this part of the BIOCLIM project.
In the present deliverable, we report on the results
of two such models, MoBidiC (Louvain-la-Neuve) and
CLIMBER-GREMLINS (LSCE). The overall objective of
the work presented here is the simulation of the climate
of the next 200 000 years for three different CO2
scenarios [Ref.1]. However, both models used for
this work have been either modified for the project
(MoBidiC) or developed within the project (CLIMBERGREMLINS).
Therefore their performance, and the
modifications and developments needed to be
documented, especially as far as their ability to
reproduce past and different climates is concerned.
Therefore, a large section of the present deliverable is
devoted to the evaluation of the models through past
climate simulations.
The deliverable is structured as follows: first, a brief
description of the models is given. In the second
section, results from the models for past climate
situations are presented. The third section deals with
the future climate simulations devised for the BIOCLIM
project: for each CO2 scenario, the results of the two
models are compared.
It is emphasized that the model results, especially
those for CLIMBER-GREMLINS, should be regarded as
illustrations of possibilities rather than absolute
predictions of climate evolution. The novel approach to
long-term climate change adopted in BIOCLIM is based
on research tools under continuing development,
notably, the CLIMBER-GREMLINS model
Starspots on the fastest rotators in the Beta Pic moving group
Aims: We carried out high-resolution spectroscopy and BV(I)_C photometric
monitoring of the two fastest late-type rotators in the nearby Beta Pictoris
moving group, HD199143 (F7V) and CD-641208 (K7V). The motivation for this work
is to investigate the rotation periods and photospheric spot patterns of these
very young stars, with a longer term view to probing the evolution of rotation
and magnetic activity during the early phases of main-sequence evolution. We
also aim to derive information on key physical parameters, such as rotational
velocity and rotation period. Methods: We applied maximum entropy (ME) and
Tikhonov regularizing (TR) criteria to derive the surface spot map
distributions of the optical modulation observed in HD199143 (F7 V) and
CD-641208 (K7V). We also used cross-correlation techniques to determine stellar
parameters such as radial velocities and rotational velocities. Lomb-Scargle
periodograms were used to obtain the rotational periods from differential
magnitude time series. Results: We find periods and inclinations of 0.356 days
and 21.5deg for HD199143, and 0.355 days and 50.1deg for CD-641208. The spot
maps of HD199143 obtained from the ME and TR methods are very similar, although
the latter gives a smoother distribution of the filling factor. Maps obtained
at two different epochs three weeks apart show a remarkable increase in spot
coverage amounting to ~7% of the surface of the photosphere over a time period
of only ~20 days. The spot maps of CD-641208 from the two methods show good
longitudinal agreement, whereas the latitude range of the spots is extended to
cover the whole visible hemisphere in the TR map. The distributions obtained
from the first light curve of HD199143 show the presence of an extended and
asymmetric active longitude with the maximum filling factor at longitude
~325degree.Comment: Accepted by A&A. 13 pages, 13 figures (4 online included), 5 Table
Deliverable D8b: Development of the physical/statistical downscaling methodology and application to climate model CLIMBER for BIOCLIM Workpackage 3. Work Package 3, Simulation of the future evolution of the biosphere system using the hierarchical strategy. Modelling Sequential Biosphere Systems under Climate Change for Radioactive Waste Disposal (BIOCLIM)
The overall aim of BIOCLIM is to assess the
possible long term impacts due to climate
change on the safety of radioactive waste
repositories in deep formations. This aim is addressed
through the following specific objectives:
âą Development of practical and innovative strategies for
representing sequential climatic changes to the
geosphere-biosphere system for existing sites over
central Europe, addressing the timescale of one
million years, which is relevant to the geological
disposal of radioactive waste.
âą Exploration and evaluation of the potential effects of
climate change on the nature of the biosphere
systems used to assess the environmental impact.
âą Dissemination of information on the new
methodologies and the results obtained from the
project among the international waste management
community for use in performance assessments of
potential or planned radioactive waste repositories.
This deliverable has the following specific motivations
and objectives:
Its main aim is to provide time series of climatic
variables at the high resolution as needed by
performance assessment (PA) of radioactive waste
repositories, on the basis of coarse output from the
CLIMBER-GREMLINS climate model
- âŠ