758 research outputs found
A purely geometric distance to the binary star Atlas, a member of the Pleiades
We present radial velocity and new interferometric measurements of the double
star Atlas, which permit, with the addition of published interferometric data,
to precisely derive the orbital parameters of the binary system and the masses
of the components. The derived semi-major axis, compared with its measured
angular size, allows to determine a distance to Atlas of 132+-4 pc in a purely
geometrical way. Under the assumption that the location of Atlas is
representative of the average distance of the cluster, we confirm the distance
value generally obtained through main sequence fitting, in contradiction with
the early Hipparcos result (118.3+-3.5 pc).Comment: 5 pages, 3 figures, accepted for publication in A&A Letter
Extrasolar planets and brown dwarfs around A-F type stars - VII. Theta Cygni radial velocity variations: planets or stellar phenomenon?
(abridged) In the frame of the search for extrasolar planets and brown dwarfs
around early-type main-sequence stars, we present the results obtained on the
early F-type star Theta Cygni. Elodie and Sophie at OHP were used to obtain the
spectra. Our dedicated radial-velocity measurement method was used to monitor
the star's radial velocities over five years. We also use complementary, high
angular resolution and high-contrast images taken with PUEO at CFHT. We show
that Theta Cygni radial velocities are quasi-periodically variable, with a
~150-day period. These variations are not due to the ~0.35-Msun stellar
companion that we detected in imaging at more than 46 AU from the star. The
absence of correlation between the bisector velocity span variations and the
radial velocity variations for this 7 km/s vsini star, as well as other
criteria indicate that the observed radial velocity variations are not due to
stellar spots. The observed amplitude of the bisector velocity span variations
also seems to rule out stellar pulsations. However, we observe a peak in the
bisector velocity span periodogram at the same period as the one found in the
radial velocity periodogram, which indicates a probable link between these
radial velocity variations and the low amplitude lineshape variations which are
of stellar origin. Long-period variations are not expected from this type of
star to our knowledge. If a stellar origin (hence of new type) was to be
confirmed for these long-period radial velocity variations, this would have
several consequences on the search for planets around main-sequence stars, both
in terms of observational strategy and data analysis. An alternative
explanation for these variable radial velocities is the presence of at least
one planet of a few Jupiter masses orbiting at less than 1 AU. (abridged)Comment: 9 pages, accepted in A
The current role of intra-arterial thrombolysis
AbstractBackground: the role of intra arterial thrombolysis (IAT) in the management of peripheral vascular disease has come under scrutiny. This study aims to assess current usage and indications for IAT in the U.K. Method: the use of IAT was assessed at our own centre and a questionnaire was sent to all centres that provide data for the U.K. âThrombolysis Study Groupâ. Results: there has been a steady decline in the use of IAT at our centre from a peak of 40 cases per annum to zero. Response was received from 22 of 24 centres (92%). Nineteen (86%) reported a decline in IAT use. Main reasons were concerns over lack of efficacy (74%) and complication rate (63%). Most centres would use IAT for acute limb ischaemia (86%). However, for acute thrombosis in specific indications the results varied; synthetic graft (82%), vein graft (54%), supra-inguinal graft (54%) and thrombosed popliteal artery aneurysm (54%). When asked what their commonest usage for IAT was, the results again varied; acute limb ischaemia (40%), graft thrombosis (40%), embolism post radiological intervention (12%), other (8%). Conclusion: there has been a significant decrease in IAT use. Concerns exist as to efficacy and complication rate. There is no clear consensus on indications.Eur J Vasc Endovasc Surg 26, 166-169 (2003
SOFI: A 3D simulator for the generation of underwater optical images
International audienceWe present an original simulator-called SOFI-for the synthetic generation of underwater optical images. The simulator architecture is flexible and relies on flow diagrams in order to allow the integration of various models for image generation which are based on the underwater optical phenomena. The objective is also to ensure real time or quasi real time performance so it takes advantage of the latest technologies, such as GPGPU, and relies on GPU programming under CUDA. Two kinds of models for image generation are presented and should be integrated in SOFI: (1) the OSOA model based on the radiative transfer theory and (2) global image modeling which describes globally how an image is deteriorated under the effects of sea water
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
Kepler KOI-13.01 - Detection of beaming and ellipsoidal modulations pointing to a massive hot Jupiter
KOI-13 was presented by the Kepler team as a candidate for having a giant
planet - KOI-13.01, with orbital period of 1.7 d and transit depth of ~0.8%. We
have analyzed the Kepler Q2 data of KOI-13, which was publicly available at the
time of the submission of this paper, and derived the amplitudes of the
beaming, ellipsoidal and reflection modulations: 8.6 +/- 1.1, 66.8 +/- 1.6 and
72.0 +/- 1.5 ppm (parts per million), respectively. After the paper was
submitted, Q3 data were released, so we repeated the analysis with the newly
available light curve. The results of the two quarters were quite similar. From
the amplitude of the beaming modulation we derived a mass of 10 +/- 2 M_Jup for
the secondary, suggesting that KOI-13.01 was a massive planet, with one of the
largest known radii. We also found in the data a periodicity of unknown origin
with a period of 1.0595 d and a peak-to-peak modulation of ~60 ppm. The light
curve of Q3 revealed a few more small-amplitude periodicities with similar
frequencies. It seemed as if the secondary occultation of KOI-13 was slightly
deeper than the reflection peak-to-peak modulation by 16.8 +/- 4.5 ppm. If
real, this small difference was a measure of the thermal emission from the
night side of KOI-13.01. We estimated the effective temperature to be 2600 +/-
150 K, using a simplistic black-body emissivity approximation. We then derived
the planetary geometrical and Bond albedos as a function of the day-side
temperature. Our analysis suggested that the Bond albedo of KOI-13.01 might be
substantially larger than the geometrical albedo.Comment: 15 pages, 8 figures, accepted for publication in Astronomy and
Astrophysic
3D structure and formation of hydrothermal vent complexes at the Paleocene-Eocene transition, the MĂžre Basin, mid-Norwegian margin
Acknowledgments We thank Statoil for providing us with the PL251 (Tulipan) geophysical and geologic reports for well 6302/6- 1. We thank NORSAR for the free academic use of the SeisRox software during the modeling procedures and to Schlumberger for the free academic use of Petrel 2015. Spectral decomposition was carried out using FFA Geoteric software at the University of Aberdeen. FFA are thanked for donation of the software license to the University of Aberdeen. The authors further acknowledge the support from the Research Council of Norway through its Center of Excellence funding scheme, project 223272 (CEED), and from the MIMES project (grant no. 244155). We also gratefully acknowledge the support by the Faculty of Mathematics and Natural Sciences of the University of Oslo to TS. Clayton Grove and Craig Magee are thanked for their many insightful comments and suggestions that helped improve the paper substantially.Peer reviewedPublisher PD
Refined parameters and spectroscopic transit of the super-massive planet HD147506b
In this paper, we report a refined determination of the orbital parameters
and the detection of the Rossiter-McLaughlin effect of the recently discovered
transiting exoplanet HD147506b (HAT-P-2b). The large orbital eccentricity at
the short orbital period of this exoplanet is unexpected and is distinguishing
from other known transiting exoplanets. We performed high-precision radial
velocity spectroscopic observations of HD147506 (HAT-P-2) with the new
spectrograph SOPHIE, mounted on the 1.93 m telescope at the Haute-Provence
observatory (OHP). We obtained 63 new measurements, including 35 on May 14 and
20 on June 11, when the planet was transiting its parent star. The radial
velocity (RV) anomaly observed illustrates that HAT-P-2b orbital motion is set
in the same direction as its parent star spin. The sky-projected angle between
the normal of the orbital plane and the stellar spin axis, \lambda = 0.2 +12.2
-12.5 deg, is consistent with zero. The planetary and stellar radii were
re-determined, yielding R_p = 0.951 +0.039 -0.053 R_Jup, R_s = 1.416 +0.040
-0.062 R_Sun. The mass M_p = 8.62 +0.39 -0.55 M_Jup and radius of HAT-P-2b
indicate a density of 12.5 +2.6 -3.6 g cm^{-3}, suggesting an object in between
the known close-in planets with typical density of the order of 1 g cm^{-3},
and the very low-mass stars, with density greater than 50 g cm^{-3}.Comment: Submitted to A&A; V2: Replaced by accepted versio
A partitioned model order reduction approach to rationalise computational expenses in multiscale fracture mechanics
We propose in this paper an adaptive reduced order modelling technique based
on domain partitioning for parametric problems of fracture. We show that
coupling domain decomposition and projection-based model order reduction
permits to focus the numerical effort where it is most needed: around the zones
where damage propagates. No \textit{a priori} knowledge of the damage pattern
is required, the extraction of the corresponding spatial regions being based
solely on algebra. The efficiency of the proposed approach is demonstrated
numerically with an example relevant to engineering fracture.Comment: Submitted for publication in CMAM
SOPHIE velocimetry of Kepler transit candidates III. KOI-423b: an 18 Mjup transiting companion around an F7IV star
We report the strategy and results of our radial velocity follow-up campaign
with the SOPHIE spectrograph (1.93-m OHP) of four transiting planetary
candidates discovered by the Kepler space mission. We discuss the selection of
the candidates KOI-428, KOI-410, KOI-552, and KOI-423. KOI-428 was established
as a hot Jupiter transiting the largest and the most evolved star discovered so
far and is described by Santerne et al. (2011a). KOI-410 does not present
radial velocity change greater than 120 m/s, which allows us to exclude at 3
sigma a transiting companion heavier than 3.4 Mjup. KOI-552b appears to be a
transiting low-mass star with a mass ratio of 0.15. KOI-423b is a new
transiting companion in the overlapping region between massive planets and
brown dwarfs. With a radius of 1.22 +- 0.11 Rjup and a mass of 18.0 +- 0.92
Mjup, KOI-423b is orbiting an F7IV star with a period of 21.0874 +- 0.0002 days
and an eccentricity of 0.12 +- 0.02. From the four selected Kepler candidates,
at least three of them have a Jupiter-size transiting companion, but two of
them are not in the mass domain of Jupiter-like planets. KOI-423b and KOI-522b
are members of a growing population of known massive companions orbiting close
to an F-type star. This population currently appears to be absent around G-type
stars, possibly due to their rapid braking and the engulfment of their
companions by tidal decay.Comment: 9 pages, 12 figures, accepted in A&
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