10,914 research outputs found
A global analysis of Spitzer and new HARPS data confirms the loneliness and metal-richness of GJ 436 b
Context. GJ 436b is one of the few transiting warm Neptunes for which a
detailed characterisation of the atmosphere is possible, whereas its
non-negligible orbital eccentricity calls for further investigation.
Independent analyses of several individual datasets obtained with Spitzer have
led to contradicting results attributed to the different techniques used to
treat the instrumental effects. Aims. We aim at investigating these previous
controversial results and developing our knowledge of the system based on the
full Spitzer photometry dataset combined with new Doppler measurements obtained
with the HARPS spectrograph. We also want to search for additional planets.
Methods. We optimise aperture photometry techniques and the photometric
deconvolution algorithm DECPHOT to improve the data reduction of the Spitzer
photometry spanning wavelengths from 3-24 {\mu}m. Adding the high precision
HARPS radial velocity data, we undertake a Bayesian global analysis of the
system considering both instrumental and stellar effects on the flux variation.
Results. We present a refined radius estimate of RP=4.10 +/- 0.16 R_Earth, mass
MP=25.4 +/- 2.1 M_Earth and eccentricity e= 0.162 +/- 0.004 for GJ 436b. Our
measured transit depths remain constant in time and wavelength, in disagreement
with the results of previous studies. In addition, we find that the
post-occultation flare-like structure at 3.6 {\mu}m that led to divergent
results on the occultation depth measurement is spurious. We obtain occultation
depths at 3.6, 5.8, and 8.0 {\mu}m that are shallower than in previous works,
in particular at 3.6 {\mu}m. However, these depths still appear consistent with
a metal-rich atmosphere depleted in methane and enhanced in CO/CO2, although
perhaps less than previously thought. We find no evidence for a potential
planetary companion, stellar activity, nor for a stellar spin-orbit
misalignment. [ABRIDGED]Comment: 25 pages, 26 figures, 8 tables, accepted for publication in A&
Understanding stellar activity-induced radial velocity jitter using simultaneous K2 photometry and HARPS RV measurements
One of the best ways to improve our understanding of the stellar
activity-induced signal in radial velocity (RV) measurements is through
simultaneous high-precision photometric and RV observations. This is of prime
importance to mitigate the RV signal induced by stellar activity and therefore
unveil the presence of low-mass exoplanets. The K2 Campaign 7 and 8
field-of-views were located in the southern hemisphere, and provided a unique
opportunity to gather unprecedented simultaneous high precision photometric
observation with K2 and high-precision RV measurements with the HARPS
spectrograph to study the relationship between photometric variability and RV
jitter. We observed nine stars with different levels of activity; from quiet to
very active. We probe the presence of any meaningful relation between measured
RV jitter and the simultaneous photometric variation, and also other activity
indicators (e.g. BIS, FWHM, , and F8), by evaluating the strength
and significance of the correlation between RVs and each indicator. We found
that for the case of very active stars, strong and significant correlations
exist between almost all the observables and measured RVs; however, for lower
activity levels the correlations become random. Except for the F8 which its
strong correlation with RV jitter persists over a wide range of stellar
activity level, and thus our result suggests that F8 might be a powerful proxy
for activity induced RV jitter. Moreover, we examine the capability of two
state-of-the-art modeling techniques, namely the FF' method and SOAP2.0, in
accurately predicting the RV jitter amplitude using the simultaneous
photometric observation. We found that for the very active stars both
techniques can reasonably well predict the amplitude of the RV jitter, however,
at lower activity levels the FF' method underpredicts the RV jitter amplitude.Comment: 13 pages, 7 figures, 2 tables, accepted for publication in A&
Reprodução no macho caprino: análise básica e aplicada.
A reprodução de pequenos ruminantes é dependente de diversos eventos fisiológicos e ambientais, assim como da harmonia dos manejos nutricionais e sanitários dos rebanhos. O conhecimento consorciado da reprodução do macho caprino, unindo avaliações básicas já existentes às práticas aplicadas a campo, torna-se de fundamental relevância para que profissionais, produtores e acadêmicos das ciências agrárias possam visualizar esta área da Medicina Veterinária de uma forma mais ampla e completa. O conhecimento de eventos fisiológicos e sua aplicação prática na utilização de exames diagnósticos, que visem à seleção de reprodutores caprinos para centrais de inseminação artificial ou mesmo que visem ? seleção de reprodutores para a utilização em programas de melhoramento genético, dar· subsídios para a escolha de animais superiores e perfeitamente confiáveis para a formão de bancos de germoplasma, por exemplo. Essa série documentos tem como objetivo esclarecer de forma conjunta a produtores, técnicos e acadêmicos, quanto ? importância de se conhecer uma avaliação andrológica e seminal com base na fisiologia dos machos caprinos e desta forma, proporcionar aos profissionais uma visão mais completa da reprodução em caprinos.bitstream/CNPC-2010/21843/1/doc79.pd
Comparison between two mobile absolute gravimeters: optical versus atomic interferometers
We report a comparison between two absolute gravimeters: the LNE-SYRTE cold
atoms gravimeter and FG5#220 of Leibniz Universit\"at of Hannover. They rely on
different principles of operation: atomic and optical interferometry. Both are
movable which enabled them to participated to the last International Comparison
of Absolute Gravimeters (ICAG'09) at BIPM. Immediately after, their bilateral
comparison took place in the LNE watt balance laboratory and showed an
agreement of 4.3 +/- 6.4 {\mu}Gal
The SOPHIE search for northern extrasolar planets: VI. Three new hot Jupiters in multi-planet extrasolar systems
We present high-precision radial-velocity measurements of three solar-type
stars: HD 13908, HD 159243, and HIP 91258. The observations were made with the
SOPHIE spectrograph at the 1.93-m telescope of Observatoire de Haute-Provence
(France). They show that these three bright stars host exoplanetary systems
composed of at least two companions. HD 13908 b is a planet with a minimum mass
of 0.865+-0.035 Mjup, on a circular orbit with a period of 19.382+-0.006 days.
There is an outer massive companion in the system with a period of 931+-17
days, e = 0.12+-0.02, and a minimum mass of 5.13+-0.25 Mjup. The star HD
159243, also has two detected companions with respective masses, periods, and
eccentricities of Mp = 1.13+-0.05 and 1.9+-0.13 Mjup, = 12.620+-0.004 and
248.4+-4.9 days, and e = 0.02+-0.02 and 0.075+-0.05. Finally, the star HIP
91258 has a planetary companion with a minimum mass of 1.068+-0.038 Mjup, an
orbital period of 5.0505+-0.0015 days, and a quadratic trend indicating an
outer planetary or stellar companion that is as yet uncharacterized. The
planet-hosting stars HD 13908, HD 159243, and HIP 91258 are main-sequence stars
of spectral types F8V, G0V, and G5V, respectively, with moderate activity
levels. HIP 91258 is slightly over-metallic, while the two other stars have
solar-like metallicity. The three systems are discussed in the frame of
formation and dynamical evolution models of systems composed of several giant
planets.Comment: accepted in A&
Demandas tecnológicas para o sistema produtivo da mandioca nas microrregiões de Altamira e Santarém, no estado do Pará.
bitstream/item/102430/1/DOC-395.pd
The SOPHIE search for northern extrasolar planets. XI. Three new companions and an orbit update: Giant planets in the habitable zone
We report the discovery of three new substellar companions to solar-type
stars, HD191806, HD214823, and HD221585, based on radial velocity measurements
obtained at the Haute-Provence Observatory. Data from the SOPHIE spectrograph
are combined with observations acquired with its predecessor, ELODIE, to detect
and characterise the orbital parameters of three new gaseous giant and brown
dwarf candidates. Additionally, we combine SOPHIE data with velocities obtained
at the Lick Observatory to improve the parameters of an already known giant
planet companion, HD16175 b. Thanks to the use of different instruments, the
data sets of all four targets span more than ten years. Zero-point offsets
between instruments are dealt with using Bayesian priors to incorporate the
information we possess on the SOPHIE/ELODIE offset based on previous studies.
The reported companions have orbital periods between three and five years and
minimum masses between 1.6 Mjup and 19 Mjup. Additionally, we find that the
star HD191806 is experiencing a secular acceleration of over 11 \ms\ per year,
potentially due to an additional stellar or substellar companion. A search for
the astrometric signature of these companions was carried out using Hipparcos
data. No orbit was detected, but a significant upper limit to the companion
mass can be set for HD221585, whose companion must be substellar.
With the exception of HD191806 b, the companions are located within the
habitable zone of their host star. Therefore, satellites orbiting these objects
could be a propitious place for life to develop.Comment: 12 pages + tables, 7 figures. Accepted for publication in Astronomy &
Astrophysic
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