289 research outputs found
Pupil stabilization for SPHERE's extreme AO and high performance coronagraph system
We propose a new concept of pupil motion sensor for astronomical adaptive
optics systems and present experimental results obtained during the first
laboratory validation of this concept. Pupil motion is an important issue in
the case of extreme adaptive optics, high contrast systems, such as the
proposed Planet Finder instruments for the ESO and Gemini 8-meter telescopes.
Such high contrast imaging instruments will definitively require pupil
stabilization to minimize the effect of quasi-static aberrations. The concept
for pupil stabilization we propose uses the flux information from the AO system
wave-front sensor to drive in closed loop a pupil tip-tilt mirror located in a
focal plane. A laboratory experiment validates this concept and demonstrates
its interest for high contrast imaging instrument.Comment: This paper was published in Optics Express and is made available as
an electronic reprint with the permission of OSA. The paper can be found at
http://www.opticsexpress.org/abstract.cfm?id=144687 on the OSA websit
DNA waves and water
Some bacterial and viral DNA sequences have been found to induce low
frequency electromagnetic waves in high aqueous dilutions. This phenomenon
appears to be triggered by the ambient electromagnetic background of very low
frequency. We discuss this phenomenon in the framework of quantum field theory.
A scheme able to account for the observations is proposed. The reported
phenomenon could allow to develop highly sensitive detection systems for
chronic bacterial and viral infections.Comment: Invited talk at the DICE2010 Conference, Castiglioncello, Italy
September 201
High-contrast spectroscopy of SCR J1845-6357 B
Spectral characterization of sub-stellar companions is essential to
understand their composition and formation processes. However, the large
contrast ratio of the brightness of each object to that of its parent star
limits our ability to extract a clean spectrum, free from any significant
contribution from the star. During the development of the long slit
spectroscopy (LSS) mode of IRDIS, the dual-band imager and spectrograph of
SPHERE, we proposed a data analysis method to estimate and remove the
contributions of the stellar spectrum. This method has never been tested on
real data because of the lack of instrumentation capable of combining adaptive
optics (AO), coronagraphy, and LSS. Nonetheless, a similar attenuation of the
star can be obtained using a particular observing configuration. Test data were
acquired using the AO-assisted spectrograph VLT/NACO. We obtained new J- and
H-band spectra of SCR J1845-6357 B, a T6 companion to a nearby (3.85\pm0.02 pc)
M8 star. This system is a well-suited benchmark as it is relatively wide
(~1.0") with a modest contrast ratio (~4 mag), and a previously published JHK
spectrum is available for reference. We demonstrate that (1) our method is
efficient at estimating and removing the stellar contribution, (2) it allows to
properly recover the spectral shape of the companion, and (3) it is essential
to obtain an unbiased estimation of physical parameters. We also show that the
slit configuration associated with this method allows us to use long exposure
times with high throughput producing high signal-to-noise ratio data. However,
the signal of the companion gets over-subtracted, particularly in our J-band
data, compelling us to use a fake companion spectrum to estimate and compensate
for the loss of flux. Finally, we report a new astrometric measurement of the
position of the companion (sep = 0.817", PA = 227.92 deg).Comment: 11 pages, 8 figures, 4 tables. Accepted for publication in A&
Effet de lâendommagement transverse sur la rĂ©sistance en compression sens fibre dâun composite carbone/Ă©poxy
National audienceL'Ă©tude expĂ©rimentale proposĂ©e analyse l'influence de l'endommagement transverse sur la rĂ©sistance en compression sens fibre pour des composites tissĂ©s carbone/Ă©poxy. Afin d'explorer plusieurs mĂ©thodes expĂ©rimentales, l'Ă©tude porte d'abord sur des essais de flexion pure oĂč le comportement dans la zone comprimĂ©e est explorĂ© pour des Ă©prouvettes saines. Ensuite un essai de compression pure sur des tubes prĂ©alablement endommagĂ©s en torsion est proposĂ©e. Les essais sont suivis par corrĂ©lation d'image afin de dĂ©terminer les effets de structure nuisant Ă la caractĂ©risation du matĂ©riau. On montrera finalement que l'endommagement transverse influence la tenue mĂ©canique en compression
SOPHIE velocimetry of Kepler transit candidates IX. KOI-415 b: a long-period, eccentric transiting brown dwarf to an evolved Sun
We report the discovery of a long-period brown-dwarf transiting companion of
the solar-type star KOI-415. The transits were detected by the Kepler space
telescope. We conducted Doppler measurements using the SOPHIE spectrograph at
the Observatoire de Haute-Provence. The photometric and spectroscopic signals
allow us to characterize a 62.14+-2.69 Mjup, brown-dwarf companion of an
evolved 0.94+-0.06 Msun star in a highly eccentric orbit of P =
166.78805+-0.00022 days and e = 0.698+-0.002. The radius of KOI-415 b is 0.79
(-0.07,+0.12) Rjup, a value that is compatible with theoretical predictions for
a 10 Gyr, low-metallicity and non-irradiated object.Comment: accepted in A&A Letter
SOPHIE velocimetry of Kepler transit candidates XIV. A joint photometric, spectroscopic, and dynamical analysis of the Kepler-117 system
As part of our follow-up campaign of Kepler planets, we observed Kepler-117
with the SOPHIE spectrograph at the Observatoire de Haute-Provence. This
F8-type star hosts two transiting planets in non-resonant orbits. The planets,
Kepler-117 b and c, have orbital periods and days,
and show transit-timing variations (TTVs) of several minutes. We performed a
combined Markov chain Monte Carlo (MCMC) fit on transits, radial velocities,
and stellar parameters to constrain the characteristics of the system. We
included the fit of the TTVs in the MCMC by modeling them with dynamical
simulations. In this way, consistent posterior distributions were drawn for the
system parameters. According to our analysis, planets b and c have notably
different masses ( and M) and low
orbital eccentricities ( and ). The
uncertainties on the derived parameters are strongly reduced if the fit of the
TTVs is included in the combined MCMC. The TTVs allow measuring the mass of
planet b, although its radial velocity amplitude is poorly constrained.
Finally, we checked that the best solution is dynamically stable.Comment: 16 pages, of whom 5 of online material.12 figures, of whom 2 in the
online material. 7 tables, of whom 4 in the online material. Published in A&
SOPHIE velocimetry of Kepler transit candidates. XV. KOI-614b, KOI-206b, and KOI-680b: a massive warm Jupiter orbiting a G0 metallic dwarf and two highly inflated planets with a distant companion around evolved F-type stars
We report the validation and characterization of three new transiting
exoplanets using SOPHIE radial velocities: KOI-614b, KOI-206b, and KOI-680b.
KOI-614b has a mass of and a radius of
, and it orbits a G0, metallic
([Fe/H]=) dwarf in 12.9 days. Its mass and radius are familiar and
compatible with standard planetary evolution models, so it is one of the few
known transiting planets in this mass range to have an orbital period over ten
days. With an equilibrium temperature of K, this places
KOI-614b at the transition between what is usually referred to as "hot" and
"warm" Jupiters. KOI-206b has a mass of and a
radius of , and it orbits a slightly evolved F7-type
star in a 5.3-day orbit. It is a massive inflated hot Jupiter that is
particularly challenging for planetary models because it requires unusually
large amounts of additional dissipated energy in the planet. On the other hand,
KOI-680b has a much lower mass of and requires less
extra-dissipation to explain its uncommonly large radius of . It is one of the biggest transiting planets characterized so far,
and it orbits a subgiant F9-star well on its way to the red giant stage, with
an orbital period of 8.6 days. With host stars of masses of
and , respectively, KOI-206b,
and KOI-680b are interesting objects for theories of formation and survival of
short-period planets around stars more massive than the Sun. For those two
targets, we also find signs of a possible distant additional companion in the
system
Characterization of the four new transiting planets KOI-188b, KOI-195b, KOI-192b, and KOI-830b
The characterization of four new transiting extrasolar planets is presented
here. KOI-188b and KOI-195b are bloated hot Saturns, with orbital periods of
3.8 and 3.2 days, and masses of 0.25 and 0.34 M_Jup. They are located in the
low-mass range of known transiting, giant planets. KOI-192b has a similar mass
(0.29 M_Jup) but a longer orbital period of 10.3 days. This places it in a
domain where only a few planets are known. KOI-830b, finally, with a mass of
1.27 M_Jup and a period of 3.5 days, is a typical hot Jupiter. The four planets
have radii of 0.98, 1.09, 1.2, and 1.08 R_Jup, respectively. We detected no
significant eccentricity in any of the systems, while the accuracy of our data
does not rule out possible moderate eccentricities. The four objects were first
identified by the Kepler Team as promising candidates from the photometry of
the Kepler satellite. We establish here their planetary nature thanks to the
radial velocity follow-up we secured with the HARPS-N spectrograph at the
Telescopio Nazionale Galileo. The combined analyses of the datasets allow us to
fully characterize the four planetary systems. These new objects increase the
number of well-characterized exoplanets for statistics, and provide new targets
for individual follow-up studies. The pre-screening we performed with the
SOPHIE spectrograph at the Observatoire de Haute-Provence as part of that study
also allowed us to conclude that a fifth candidate, KOI-219.01, is not a planet
but is instead a false positive.Comment: 13 pages, 4 figures, 6 tables, final version accepted for publication
in A&
SOPHIE velocimetry of Kepler transit candidates XI. Kepler-412 system: probing the properties of a new inflated hot Jupiter
We confirm the planetary nature of Kepler-412b, listed as planet candidate
KOI-202 in the Kepler catalog, thanks to our radial velocity follow-up program
of Kepler-released planet candidates, which is on going with the SOPHIE
spectrograph. We performed a complete analysis of the system by combining the
Kepler observations from Q1 to Q15, to ground-based spectroscopic observations
that allowed us to derive radial velocity measurements, together with the host
star parameters and properties. We also analyzed the light curve to derive the
star's rotation period and the phase function of the planet, including the
secondary eclipse. We found the planet has a mass of 0.939 0.085
M and a radius of 1.325 0.043 R which makes it a member
of the bloated giant subgroup. It orbits its G3 V host star in 1.72 days. The
system has an isochronal age of 5.1 Gyr, consistent with its moderate stellar
activity as observed in the Kepler light curve and the rotation of the star of
17.2 1.6 days. From the detected secondary, we derived the day side
temperature as a function of the geometric albedo and estimated the geometrical
albedo, Ag, is in the range 0.094 to 0.013. The measured night side flux
corresponds to a night side brightness temperature of 2154 83 K, much
greater than what is expected for a planet with homogeneous heat
redistribution. From the comparison to star and planet evolution models, we
found that dissipation should operate in the deep interior of the planet. This
modeling also shows that despite its inflated radius, the planet presents a
noticeable amount of heavy elements, which accounts for a mass fraction of 0.11
0.04.Comment: 11 pages, 9 figure
Extrasolar planets and brown dwarfs around A--F type stars. VIII. A giant planet orbiting the young star HD113337
In the frame of the search for extrasolar planets and brown dwarfs around
early-type main-sequence stars, we present the detection of a giant planet
around the young F-type star HD113337. We estimated the age of the system to be
150 +100/-50 Myr. Interestingly, an IR excess attributed to a cold debris disk
was previously detected on this star. The SOPHIE spectrograph on the 1.93m
telescope at Observatoire de Haute-Provence was used to obtain ~300 spectra
over 6 years. We used our SAFIR tool, dedicated to the spectra analysis of A
and F stars, to derive the radial velocity variations. The data reveal a 324.0
+1.7/-3.3 days period that we attribute to a giant planet with a minimum mass
of 2.83 +- 0.24 Mjup in an eccentric orbit with e=0.46 +- 0.04. A long-term
quadratic drift, that we assign to be probably of stellar origin, is
superimposed to the Keplerian solution.Comment: 7 pages, 4 figure
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