1,207 research outputs found
TASTE IV. Refining ephemeris and orbital parameters for HAT-P-20b and WASP-1b
We present four new light curves of transiting exoplanets WASP-1b and
HAT-P-20b, observed within the TASTE (The Asiago Search for Transit timing
variations of Exoplanets) project. We re-analyzed light curves from the
literature in a homogeneous way, calculating a refined ephemeris and
orbital-physical parameters for both objects. WASP-1b does not show any
significant Transit Timing Variation signal at the 120 s-level. As for
HAT-P-20b, we detected a deviation from our re-estimated linear ephemeris that
could be ascribed to the presence of a perturber or, more probably, to a
previously unnoticed high level of stellar activity. The rotational period of
HAT-P-20 A we obtained from archival data (P_rot ~ 14.5 days), combined with
its optical variability and strong emission of CaII H&K lines, is consistent
with a young stellar age (< 1 Gyr) and support the hypothesis that stellar
activity may be responsible of the measured deviations of the transit times.Comment: 7 pages, 4 figures, 3 tables, accepted to Astronomische Nachrichte
Increasing the efficiency of utilization of soil and fertilizer phosphorus in the subtropical and tropical agricultural systems C
As a rule, soils of the subtropical and tropical regions, in which rainfall is not limiting, are acidic, and low in phosphorus, and, to a less extent, in other macro and micronutrients as well, such a sulfur, boron and zinc. The establishment of a permanent agricultural prac. tice therefore, demands relatively high usage of liming and phosphatic fertilization, to begin with. Several approaches, not mutually exclusive, could be used in order to increase the efficiency of utilization of soil and fertilizer phosphorus so that, goal of diminishing costs of production is reached. The use of liming materials bringing up pH to 6.0-6.5 causes the conversion of iron and aluminum phosphates to more available calcium phosphates; on the other hand, by raising calcium saturation in the exchange complex, it improves the development and operation if the root system which allows c or a higher utilization of all soil nutrients, including phosphorus, and helps of stand water deficits which may occur. The role of mycorrhizal fungi should be considered as a way of increasing soil and fertilizer P utilization, as well as the limitations thereof. Screening of and breeding for varieties with higher efficiency of uptake and utilization of soil and fertilizer phosphorus leads to a reduction in cost of inputs and to higher benefit/cost ratios. Corrective fertilization using ground rock phosphate helps to saturate the fixation power of the soil thereby reducing, as a consequence, the need for phosphorus in the maintenance fertilization. Maintenance fertilization, in which soluble phos-phatic sources are used, could be improved by several means whose performance has been proved: limimg, granula tion, placement, use of magnesium salts. Last, cost of phosphate fertilization could be further reduced, without impairing yields, through impairing yields, through changes in technology designed to obtain products better adapted to local conditions and to the availability or raw materials and energy sources.A falta de P no solo é o fator que com mais freqüência limita a produção nas condições brasileiras, particularmente a das culturas anuais. A eficiência da adubação fosfatada pode ser aumentada de diversas maneiras que à s vezes são empregadas conjuntamente, a saber: 1) Calagem - aumenta o fornecimento de P do solo e diminui a conversão do P do adubo em formas de menor aproveitamento; 2) Localização diminuindo a proporção do fósforo fixado aumenta a absorção; 3) Tipo de adubo - o aproveitamento do P2O5 pode variar em função do adubo usado; 4) Espécies e variedades -o aproveitamento do fósforo na formação da colheita é influenciado pela capacidade da planta; 5) Análise do solo - as quantidades de adubo a usar são função do teor de P do solo e da relação entre custo do fertilizante e valor do produto agrÃcola; 6) Magnésio - a absorção do P do adubo depende do teor de Mg no solo podendo por isso ser aumentada pelo fornecimento de calcário dolomÃtico ou de sais solúveis de magnésio
Eficiência de fontes e doses de fósforo na alfafa e centrosema cultivadas em latossolo amarelo.
O objetivo deste trabalho foi avaliar a eficiência agronômica de fontes e doses de P na alfafa e na centrosema, cultivadas em casa de vegetação, em Latossolo Amarelo distrófico
Fontes e doses de fósforo na concentração e no conteúdo de nitrogênio e micronutrientes na alfafa e na centrosema.
O objetivo deste trabalho foi o de avaliar o efeito de fontes e doses de fósforo na concentração e o conteúdo de N, Cu, Fe, Mn e Zn na alfafa e na centrosema cultivadas em Latossolo Vermelho-Amarelo distrófico
TASTE. III. A homogeneous study of transit time variations in WASP-3b
The TASTE project is searching for low-mass planets with the Transit Timing
Variation (TTV) technique, by gathering high-precision, short-cadence light
curves for a selected sample of transiting exoplanets. It has been claimed that
the "hot Jupiter" WASP-3b could be perturbed by a second planet. Presenting
eleven new light curves (secured at the IAC80 and UDEM telescopes) and
re-analyzing thirty-eight archival light curves in a homogeneous way, we show
that new data do not confirm the previously claimed TTV signal. However, we
bring evidence that measurements are not consistent with a constant orbital
period, though no significant periodicity can be detected. Additional dynamical
modeling and follow-up observations are planned to constrain the properties of
the perturber or to put upper limits to it. We provide a refined ephemeris for
WASP-3b and improved orbital/physical parameters. A contact eclipsing binary,
serendipitously discovered among field stars, is reported here for the first
time.Comment: 10 pages, 6 figures, 4 tables; accepted for publication in A&
M4 Core Project with HST - III. Search for variable stars in the primary field
We present the results of a photometric search for variable stars in the core
of the Galactic globular cluster M4. The input data are a large and
unprecedented set of deep Hubble Space Telescope WFC3 images (large program
GO-12911; 120 orbits allocated), primarily aimed at probing binaries with
massive companions by detecting their astrometric wobbles. Though these data
were not optimised to carry out a time-resolved photometric survey, their
exquisite precision, spatial resolution and dynamic range enabled us to firmly
detect 38 variable stars, of which 20 were previously unpublished. They include
19 cluster-member eclipsing binaries (confirming the large binary fraction of
M4), RR Lyrae, and objects with known X-ray counterparts. We improved and
revised the parameters of some among published variables.Comment: 11 pages, 5 figures, 2 tables. Accepted for publication in MNRA
The M4 Core Project with HST --- I. Overview and First-Epoch
We present an overview of the ongoing Hubble Space Telescope large program
GO-12911. The program is focused on the core of M4, the nearest Galactic
globular cluster, and the observations are designed to constrain the number of
binaries with massive companions (black holes, neutron stars, or white dwarfs)
by measuring the ``wobble'' of the luminous (main-sequence) companion around
the center of mass of the pair, with an astrometric precision of ~50
micro-arcseconds. The high spatial resolution and stable medium-band PSFs of
WFC3/UVIS will make these measurements possible. In this work we describe: (i)
the motivation behind this study, (ii) our observing strategy, (iii) the many
other investigations enabled by this unique data set, and which of those our
team is conducting, and (iv) a preliminary reduction of the first-epoch
data-set collected on October 10, 2012.Comment: 25 pages, 14 figures (9 at low resolution), 3 tables. Published in:
Astronomische Nachrichten, Volume 334, Issue 10, pages 1062-1085, December
2013. http://onlinelibrary.wiley.com/doi/10.1002/asna.201311911/abstrac
A possibly inflated planet around the bright, young star DS Tuc A
The origin of the observed diversity of planetary system architectures is one
of the main topic of the exoplanetary research. The detection of a
statistically significant sample of planets around young stars allows us to
study the early stages of planet formation and evolution, but only a handful of
them is known so far. In this regard, a considerable contribution is expected
from the NASA TESS satellite, which is now performing a survey of
of the sky to search for short-period transiting planets In its first month of
operations, TESS found a planet candidate with an orbital period of 8.14 days
around a member of the Tuc-Hor young association ( 40 Myr), the G6V main
component of the binary system DS\,Tuc. If confirmed, it would be the first
transiting planet around a young star suitable for radial velocity and/or
atmospheric characterization. We aim to validate the planetary nature of this
companion and to measure its orbital and physical parameters. We obtain
accurate planet parameters by coupling an independent reprocessing of the TESS
light curve with improved stellar parameters and the dilution caused by the
binary companion; we analyse high precision archival radial velocities to
impose an upper limit of about 0.1 M on the planet mass; we finally
rule out the presence of external companions beyond 40 au with adaptive optics
images. We confirm the presence of a young, giant ( R) planet having a not negligible possibility to be inflated (theoretical
mass M) around DS\,Tuc~A. We discuss the feasibility
of mass determination, Rossiter-McLaughlin analysis and atmosphere
characterization, allowed by the brightness of the star.Comment: 12 pages, 11 figures. Accepted for publication in A&
Alopecia universalis after discontinuation of pegylated interferon and ribavirin combination therapy for hepatitis C: a case report
Abstract For the last decade, the combination therapy of pegylated interferon (Peg-IFN) plus ribavirin (RBV) has been considered as the standard of care treatment for chronic hepatitis C virus (HCV) infection. However, it has been associated with an increased incidence of many adverse cutaneous reactions and emergence of autoantibodies or even autoimmune diseases. We report a case of irreversible alopecia universalis (AU) with complete hair loss extended to the whole body, which started after discontinuation of Peg-IFN/RBV combination therapy for chronic HCV infection. In conclusion, this case represents an uncommon presentation of a common disease. Physicians must be aware of the potential adverse reactions of an antiviral therapy containing IFN, which might occur even after the discontinuation, and fully inform the patient at the beginning of his treatment course. We hope that interferon-free regimens will utterly supplant interferon-based therapy for most or all HCV patients avoiding the emergence of autoimmune manifestations
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