1,522 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
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
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
The High-Metallicity Explosion Environment of the Relativistic Supernova 2009bb
We investigate the environment of the nearby (d ~ 40Mpc) broad-lined Type Ic
supernova SN 2009bb. This event was observed to produce a relativistic outflow
likely powered by a central accreting compact object. While such a phenomenon
was previously observed only in long-duration gamma-ray bursts (LGRBs), no LGRB
was detected in association with SN 2009bb. Using an optical spectrum of the SN
2009bb explosion site, we determine a variety of ISM properties for the host
environment, including metallicity, young stellar population age, and star
formation rate. We compare the SN explosion site properties to observations of
LGRB and broad-lined SN Ic host environments on optical emission line ratio
diagnostic diagrams. Based on these analyses, we find that the SN 2009bb
explosion site has a very high metallicity of ~2x solar, in agreement with
other broad-lined SN Ic host environments and at odds with the low-redshift
LGRB host environments and recently proposed maximum metallicity limits for
relativistic explosions. We consider the implications of these findings and the
impact that SN 2009bb's unusual explosive properties and environment have on
our understanding of the key physical ingredient that enables some SNe to
produce a relativistic outflow.Comment: 7 pages, 4 figures, 1 table; accepted for publication in ApJ Letters
(replaced to include missing figure
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]
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
Deliverable D4/5: Global climatic characteristics, including vegetation and seasonal cycles over Europe, for snapshots over the next 200,000 years. 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 aim of the BIOCLIM project is to develop and
present techniques that can be used to develop
self-consistent patterns of possible future
climate changes over the next million years (climate
scenarios), and to demonstrate how these climate
scenarios can be used in assessments of the long-term
safety of nuclear waste repository sites.
Within the project, two strategies are implemented to
predict climate change. The first is the hierarchical
strategy, in which a hierarchy of climate models is used
to investigate the evolution of climate over the period of
interest. These models vary from very simple 2-D and
threshold models, which simulate interactions between
only a few aspects of the earth system, through general
circulation models (GCMs) and vegetation models,
which simulate in great detail the dynamics and physics
of the atmosphere, ocean, and biosphere, to regional
models, which focus in particular on the European
region and the specific areas of interest. The second
strategy is the integrated strategy, in which
intermediate complexity climate models are developed,
and used to consecutively simulate the development of
the earth system over many millennia. Although these
models are relatively simple compared to a GCM, they
are more advanced than 2D models, and do include
physical descriptions of the biosphere, cryosphere,
atmosphere and ocean.
This deliverable, D4/5, focuses on the hierarchical
strategy, and in particular the GCM and vegetation
model simulation of possible future climates.
Deliverable D3 documented the first step in this
strategy. The Louvain-la-Neuve 2-D climate model
(LLN-2D) was used to estimate (among other variables)
annual mean temperatures and ice volume in the
Northern Hemisphere over the next 1 million years.
It was driven by the calculated evolution of orbital
parameters, and plausible scenarios of CO2
concentration. From the results, 3 future time periods
within the next 200,000 years were identified as being
extreme, that is either significantly warmer or cooler
than the present. The next stage in the hierarchical
strategy was to use a GCM and biosphere model, to
simulate in more detail these extreme time periods
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
Deliverable D10/12: Development and application of a methology for taking climate-driven environmental change into account in performance assessments.Work package 4:Biosphere System Description. Modelling Sequential Biosphere Systems under Climate Change for Radioactive Waste Disposal(BIOCLIM)
The aim of the BIOCLIM project has been to
provide a scientific basis and practical
methodology for assessing the potential impacts
of long-term climate change on biosphere
characteristics in the context of radiological
performance assessments (PA) of radioactive waste
repositories in deep geological formations. The project
brought together twelve different European
organisations plus associated sub-contractors with
responsibilities for either the safe disposal of
radioactive waste or the development of climate
models. Through this scientific and technical
collaboration, climate models that can simulate future
climate changes in Europe over very long timescales
have been developed. The climate modelling results
have been linked to an understanding of the pattern of
biosphere changes for selected European regions in
order to address the issue of how to represent future
biosphere systems in long term radiological
performance assessments.
The project was implemented through five work
packages (WP)
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