2,773 research outputs found
Performance of the Micromegas detector in the CAST experiment
The gaseous Micromegas detector designed for the CERN Axion search experiment
CAST, operated smoothly during Phase-I, which included the 2003 and 2004
running periods. It exhibited linear response in the energy range of interest
(1-10keV), good spatial sensitivity and energy resolution (15-19% FWHM at
5.9keV)as well as remarkable stability. The detector's upgrade for the 2004
run, supported by the development of advanced offline analysis tools, improved
the background rejection capability, leading to an average rate 5x10^-5
counts/sec/cm^2/keV with 94% cut efficiency. Also, the origin of the detected
background was studied with a Monte Carlo simulation, using the GEANT4 package.Comment: Prepared for PSD7: The Seventh International Conference on Position
Sensitive Detectors, Liverpool, United Kingdom, 12-16 Sep. 200
Paisaje y ciudad
The history of the relationship between men’s cities and Nature has gone through different times; the country appropriation process developed by cities increases at the Modern Period and, in the XXth century, a very intense urbanization process gave way to the ecological movement birth, showing conservation and sustainability as a matter for concern. Tendencies in the first years of the 21th century present country merged with city into a new and unique landscape, as the result of the appearence of a regional and diffuse city, wher the enclosed open spaces are also completely active; even more, a landscape where the demand for the use of the territory as urban space spreads futher than the city borders. The reading of this XXIst century creation landscape turns out to be the spectator’s own appropriation.La relación entre la ciudad del hombre y la Naturaleza ha atravesado diferentes etapas a través de la historia; el proceso de apropiación del campo por parte de la ciudad se acentúa en la Modernidad, y en el siglo XX un intensísimo proceso urbanizador da paso al nacimiento de la conciencia ecológica para evidenciar la necesidad de conservación y sostenibilidad del entorno. Las tendencias en el inicio del siglo XXI vienen definidas por una fusión de campo y ciudad en un único “paisaje total” fruto de la aparición de una ciudad regional y difusa donde los espacios libres englobados son también plenamente activos, e incluso en la que la demanda se extiende más allá de la propia ciudad reivindicando el uso del territorio como si de ciudad se tratase. La lectura del paisaje creado en el siglo XXI se convierte en la apropiación que de él hace el espectador
Cedrinho como alternativa para produção de madeira em pequenas propriedades rurais.
bitstream/item/37740/1/com-tec172.pd
The 0.4-Mo Eclipsing Binary CU Cancri: Absolute Dimensions, Comparison with Evolutionary Models and Possible Evidence for a Circumstellar Dust Disk
Photometric observations in the R and I bands of the detached M-type
double-lined eclipsing binary CU Cnc have been acquired and analysed. The
photometric elements obtained from the analysis of the light curves have been
combined with an existing spectroscopic solution to yield high-precision
(errors<2%) absolute dimensions: M_A=0.4333+/-0.0017 Mo, M_B=0.3980+/-0.0014
Mo, R_A=0.4317+/-0.0052 Ro, and R_B=0.3908+/-0.0094 Ro. The mean effective
temperature of the system has been estimated to be Teff=3140+/-150 K by
comparing multi-band photometry with synthetic colors computed from model
atmospheres. Additionally, we have been able to obtain an estimate for the age
(~320 Myr) and chemical composition ([Fe/H]~0.0) of the binary system through
its membership of the Castor moving group. With all these observational
constraints, we have carried out a critical test of recent stellar models for
low-mass stars. The comparison reveals that most evolutionary models
underestimate the radius of the stars by as much as 10%, thus confirming the
trend observed by Torres & Ribas (2002) for YY Gem and V818 Tau. In the
mass-absolute magnitude diagram, CU Cnc is observed to be dimmer than other
stars of the same mass. After ruling out a number of different scenarios, the
apparent faintness of CU Cnc can be explained if its components are some 10%
cooler than similar-mass stars or if there is some source of circumstellar dust
absorption. The latter could be a tantalizing indirect evidence for a coplanar
(Vega-like) dusty disk around this relatively young M-type binary.Comment: 14 pages, 5 figures, 6 tables. Accepted for publication in A&A.
Tables 1 and 2 available in electronic form at the CDS after publicatio
The K2-ESPRINT Project VI: K2-105 b, a Hot-Neptune around a Metal-rich G-dwarf
We report on the confirmation that the candidate transits observed for the
star EPIC 211525389 are due to a short-period Neptune-sized planet. The host
star, located in K2 campaign field 5, is a metal-rich ([Fe/H] = 0.260.05)
G-dwarf (T_eff = 543070 K and log g = 4.480.09), based on
observations with the High Dispersion Spectrograph (HDS) on the Subaru 8.2m
telescope. High-spatial resolution AO imaging with HiCIAO on the Subaru
telescope excludes faint companions near the host star, and the false positive
probability of this target is found to be < using the open source
vespa code. A joint analysis of transit light curves from K2 and additional
ground-based multi-color transit photometry with MuSCAT on the Okayama 1.88m
telescope gives the orbital period of P = 8.2669020.000070 days and
consistent transit depths of or . The transit depth corresponds to a planetary radius of , indicating that EPIC 211525389 b is a
short-period Neptune-sized planet. Radial velocities of the host star, obtained
with the Subaru HDS, lead to a 3\sigma\ upper limit of 90 on the mass of EPIC 211525389 b, confirming its planetary nature.
We expect this planet, newly named K2-105 b, to be the subject of future
studies to characterize its mass, atmosphere, spin-orbit (mis)alignment, as
well as investigate the possibility of additional planets in the system.Comment: 11 pages, 9 figures, 4 tables, PASJ accepte
Impact of the new solar abundances on the calibration of the PMS binary system RS Cha
Context: In a recent work, we tried to obtain a calibration of the two
components of the pre-main sequence binary system RS Cha by means of
theoretical stellar models. We found that the only way to reproduce the
observational parameters of RS Cha with standard stellar models is to decrease
the initial abundances of carbon and nitrogen derived from the GN93 solar
mixture of heavy elements by a few tenths of dex.
Aims: In this work, we aim to reproduce the observational properties of the
RS Cha stars with stellar evolution models based on the new AGS05 solar mixture
recently derived from a three-dimensional solar model atmosphere. The AGS05
mixture is depleted in carbon, nitrogen and oxygen with respect to the GN93
mixture.
Methods: We calculated new stellar models of the RS Cha components using the
AGS05 mixture and appropriate opacity tables. We sought models that
simultaneously satisfy the observations of the two components (masses, radii,
luminosities, effective temperatures and metallicity).
Results: We find that it is possible to reproduce the observational data of
the RS Cha stars with AGS05 models based on standard input physics. From these
models, the initial helium content of the system is Y~0.255 and its age is
~9.13 +- 0.12 Myr.Comment: Research note accepted in A&A, 5 pages, 2 figure
Magdalena (Colombia) (Río). Mapas generales (17--?). 1:467836
Título propio tomado del versoManuscrito firmado y rubricado por el autor. A plumilla en tinta negraSeñala toponimia de los núcleos de población existentes a lo largo del curso del río y la dirección de éste mediante flechaCopia digital. Madrid : Ministerio de Cultura. Dirección General del Libro, Archivos y Bibliotecas, 201
Scalar field in cosmology: Potential for isotropization and inflation
The important role of scalar field in cosmology was noticed by a number of
authors. Due to the fact that the scalar field possesses zero spin, it was
basically considered in isotropic cosmological models. If considered in an
anisotropic model, the linear scalar field does not lead to isotropization of
expansion process. One needs to introduce scalar field with nonlinear potential
for the isotropization process to take place. In this paper the general form of
scalar field potentials leading to the asymptotic isotropization in case of
Bianchi type-I cosmological model, and inflationary regime in case of isotropic
space-time is obtained. In doing so we solved both direct and inverse problem,
where by direct problem we mean to find metric functions and scalar field for
the given potential, whereas, the inverse problem means to find the potential
and scalar field for the given metric function. The scalar field potentials
leading to the inflation and isotropization were found both for harmonic and
proper synchronic time.Comment: 10 page
A Test of Pre-Main-Sequence Lithium Depletion Models
Despite the extensive study of lithium depletion during pre-main-sequence
contraction, studies of individual stars show discrepancies between ages
determined from the HR diagram and ages determined from lithium depletion (Song
et al. 2002, White & Hillenbrand 2005) indicating open questions in the
pre-main-sequence evolutionary models. To further test these models, we present
high resolution spectra for members of the Beta Pictoris Moving Group (BPMG),
which is young and nearby. We measure equivalent widths of the 6707.8 Angstrom
Li I line in these stars and use them to determine lithium abundances. We
combine the lithium abundance with the predictions of pre-main-sequence
evolutionary models in order to calculate a lithium depletion age for each
star. We compare this age to the age predicted by the HR diagram of the same
model. We find that the evolutionary models under-predict the amount of lithium
depletion for the BPMG given its nominal HR diagram age of ~12 Myr (Zuckerman
et al. 2001), particularly for the mid-M stars, which have no observable Li I
line. This results in systematically older ages calculated from lithium
depletion isochrones than from the HR diagram. We suggest that this discrepancy
may be related to the discrepancy between measured M-dwarf radii and the
smaller radii predicted by evolutionary models.Comment: Accepted by ApJ; 21 pages, 5 figure
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