Killingbeck J.P.,University of Hull |
Lakhlifi A.,Observatoire de Besancon
Journal of Mathematical Chemistry | Year: 2017
Accurate results for WKB and quantum mechanical approaches to the quartic oscillator are obtained by renormalized perturbation theory. The WKB estimate of (Formula presented.)(0) agrees closely with that obtained using a finite difference method previously published in this journal. © 2017 Springer International Publishing Switzerland
Lammer H.,Austrian Academy of Sciences |
Chassefiere E.,University Paris - Sud |
Karatekin O.,Royal Observatory of Belgium |
Morschhauser A.,German Aerospace Center |
And 12 more authors.
Space Science Reviews | Year: 2013
The evolution and escape of the martian atmosphere and the planet's water inventory can be separated into an early and late evolutionary epoch. The first epoch started from the planet's origin and lasted ∼500 Myr. Because of the high EUV flux of the young Sun and Mars' low gravity it was accompanied by hydrodynamic blow-off of hydrogen and strong thermal escape rates of dragged heavier species such as O and C atoms. After the main part of the protoatmosphere was lost, impact-related volatiles and mantle outgassing may have resulted in accumulation of a secondary CO2 atmosphere of a few tens to a few hundred mbar around ∼4-4.3 Gyr ago. The evolution of the atmospheric surface pressure and water inventory of such a secondary atmosphere during the second epoch which lasted from the end of the Noachian until today was most likely determined by a complex interplay of various nonthermal atmospheric escape processes, impacts, carbonate precipitation, and serpentinization during the Hesperian and Amazonian epochs which led to the present day surface pressure. © 2012 Springer Science+Business Media Dordrecht.
Bonifacio P.,University Paris Diderot |
Arenou F.,University Paris Diderot |
Babusiaux C.,University Paris Diderot |
Balkowski C.,University Paris Diderot |
And 29 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010
We present the scientific motivations for GYES: a high multiplex (of the order of several hundred), high resolution (about 20 000), spectrograph to be placed at the prime focus of the CFHT. The main purpose of such an instrument is to conduct a spectroscopic survey complementary to the Gaia mission. The final Gaia catalogue (expected around 2020) will provide accurate distances, proper motions and spectrophotometry for all the stars down to a magnitude of 20. The spectroscopic instrument on board the Gaia satellite will provide intermediate resolution (R=11 500) spectra for stars down to the 17th magnitude. For the fainter stars there will be no radial velocity information. For all the stars the chemical information will be limited to a few species. A multifibre spectrograph at the prime focus of the CFHT will be able to provide the high resolution spectra for stars fainter than 13th magnitude, needed to obtain both accurate radial velocities and detailed chemical abundances. The possible use of GYES will not be limited to Gaia complementary surveys and we here describe the potentialities of such an instrument. We describe here how the scientific drivers are translated into technical requirements. The results of our on-going feasibility study are described in an accompanying poster. © 2010 Copyright SPIE - The International Society for Optical Engineering.
Parker A.H.,University of Victoria |
Parker A.H.,Harvard - Smithsonian Center for Astrophysics |
Kavelaars J.J.,National Research Council Canada |
Petit J.-M.,Observatoire de Besancon |
And 3 more authors.
Astrophysical Journal | Year: 2011
The low-inclination component of the Classical Kuiper Belt is host to a population of extremely widely separated binaries. These systems are similar to other trans-Neptunian binaries (TNBs) in that the primary and secondary components of each system are of roughly equal size. We have performed an astrometric monitoring campaign of a sample of seven wide-separation, long-period TNBs and present the first-ever well-characterized mutual orbits for each system. The sample contains the most eccentric (2006 CH69, em = 0.9) and the most widely separated, weakly bound (2001 QW 322, a/RH ≃ 0.22) binary minor planets known, and also contains the system with lowest-measured mass of any TNB (2000 CF 105, M sys ≃ 1.85 × 1017kg). Four systems orbit in a prograde sense, and three in a retrograde sense. They have a different mutual inclination distribution compared to all other TNBs, preferring low mutual-inclination orbits. These systems have geometric r-band albedos in the range of 0.09-0.3, consistent with radiometric albedo estimates for larger solitary low-inclination Classical Kuiper Belt objects, and we limit the plausible distribution of albedos in this region of the Kuiper Belt. We find that gravitational collapse binary formation models produce an orbital distribution similar to that currently observed, which along with a confluence of other factors supports formation of the cold Classical Kuiper Belt in situ through relatively rapid gravitational collapse rather than slow hierarchical accretion. We show that these binary systems are sensitive to disruption via collisions, and their existence suggests that the size distribution of TNOs at small sizes remains relatively shallow. © 2011. The American Astronomical Society. All rights reserved.
Uttenthaler S.,Catholic University of Leuven |
Stute M.,Jet Propulsion Laboratory |
Stute M.,National and Kapodistrian University of Athens |
Stute M.,University of Turin |
And 6 more authors.
Astronomy and Astrophysics | Year: 2010
Aims. We aim at measuring mass-loss rates and the luminosities of a statistically large sample of Galactic bulge stars at several galactocentric radii. The sensitivity of previous infrared surveys of the bulge has been rather limited, thus fundamental questions for late stellar evolution, such as the stage at which substantial mass-loss begins on the red giant branch and its dependence on fundamental stellar properties, remain unanswered. We aim at providing evidence and answers to these questions. Methods. To this end, we observed seven 15 × 15 arcmin2 fields in the nuclear bulge and its vicinity with unprecedented sensitivity using the IRAC and MIPS imaging instruments on-board the Spitzer Space Telescope. In each of the fields, tens of thousands of point sources were detected. Results. In the first paper based on this data set, we present the observations, data reduction, the final catalogue of sources, and a detailed comparison to previous mid-IR surveys of the Galactic bulge, as well as to theoretical isochrones. We find in general good agreement with other surveys and the isochrones, supporting the high quality of our catalogue. © 2010 ESO.
Bonifacio P.,University Paris Diderot |
Mignot S.,University Paris Diderot |
Dournaux J.-L.,University Paris Diderot |
Francois P.,University Paris Diderot |
And 39 more authors.
EAS Publications Series | Year: 2011
We have chosen the name of GYES, one of the mythological giants with one hundred arms, offspring of Gaia and Uranus, for our instrument study of a multifibre spectrograph for the prime focus of the Canada-France-Hawaii Telescope. Such an instrument could provide an excellent ground-based complement for the Gaia mission and a northern complement to the HERMES project on the AAT. The CFHT is well known for providing a stable prime focus environment, with a large field of view, which has hosted several imaging instruments, but has never hosted a multifibre spectrograph. Building upon the experience gained at GÉPI with FLAMES-Giraffe and X-Shooter, we are investigating the feasibility of a high multiplex spectrograph (about 500 fibres) over a field of view one degree in diameter. We are investigating an instrument with resolution in the range 15000 to 30000, which should provide accurate chemical abundances for stars down to 16th magnitude and radial velocities, accurate to 1 kms -1 for fainter stars. The study is led by GÉPI-Observatoire de Paris with a contribution from Oxford for the study of the positioner. The financing for the study comes from INSU CSAA and Observatoire de Paris. The conceptual study will be delivered to CFHT for review by October 1st 2010. © EAS, EDP Sciences 2011.
An D.,Ewha Womans University |
Ramirez S.V.,California Institute of Technology |
Sellgren K.,Ohio State University |
Arendt R.G.,NASA |
And 6 more authors.
Astrophysical Journal | Year: 2011
We present results from our spectroscopic study, using the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope, designed to identify massive young stellar objects (YSOs) in the Galactic center (GC). Our sample of 107 YSO candidates was selected based on Infrared Array Camera (IRAC) colors from the high spatial resolution, high sensitivity Spitzer/IRAC images in the Central Molecular Zone, which spans the central ∼300pc region of the Milky Way. We obtained IRS spectra over 5-35 μm using both high- and low-resolution IRS modules. We spectroscopically identify massive YSOs by the presence of a 15.4 μm shoulder on the absorption profile of 15 μm CO2 ice, suggestive of CO2 ice mixed with CH3OH ice on grains. This 15.4 μm shoulder is clearly observed in 16 sources and possibly observed in an additional 19 sources. We show that nine massive YSOs also reveal molecular gas-phase absorption from CO2, C2H2, and/or HCN, which traces warm and dense gas in YSOs. Our results provide the first spectroscopic census of the massive YSO population in the GC. We fit YSO models to the observed spectral energy distributions and find YSO masses of 8-23 M ⊙, which generally agree with the masses derived from observed radio continuum emission. We find that about 50% of photometrically identified YSOs are confirmed with our spectroscopic study. This implies a preliminary star formation rate of ∼0.07 M⊙ yr-1 at the GC. © 2011. The American Astronomical Society. All rights reserved.
Lebzelter T.,University of Vienna |
Uttenthaler S.,University of Vienna |
Busso M.,University of Perugia |
Schultheis M.,Observatoire de Besancon |
Aringer B.,National institute for astrophysics
Astronomy and Astrophysics | Year: 2012
Context. A small number of K-type giants on the red giant branch (RGB) is known to be very rich in lithium (Li). This fact is not accounted for by standard stellar evolution theory. The exact phase and mechanism of Li enrichment is still a matter of debate. Aims. Our goal is to probe the abundance of Li along the RGB, from its base to the tip, to confine Li-rich phases that are supposed to occur on the RGB. Methods. For this end, we obtained medium-resolution spectra with the FLAMES spectrograph at the VLT in GIRAFFE mode for a large sample of 401 low-mass RGB stars located in the Galactic bulge. The Li abundance was measured in the stars with a detectable Li 670.8 nm line by means of spectral synthesis with COMARCS model atmospheres. A new 2MASS (J-K S)-T eff calibration from COMARCS models is presented in the Appendix. Results. Thirty-one stars with a detectable Li line were identified, three of which are Li-rich according to the usual criterion (logε(Li) > 1.5). The stars are distributed all along the RGB, not concentrated in any particular phase of the red giant evolution (e.g. the luminosity bump or the red clump). The three Li-rich stars are clearly brighter than the luminosity bump and red clump, and do not show any signs of enhanced mass loss. Conclusions. We conclude that the Li enrichment mechanism cannot be restricted to a clearly defined phase of the RGB evolution of low-mass stars (M ∼ 1 M ⊙), contrary to earlier suggestions from disk field stars. © 2012 ESO.
Guittet M.,University Paris Diderot |
Haywood M.,University Paris Diderot |
Schultheis M.,Observatoire de Besancon
EPJ Web of Conferences | Year: 2012
We investigate the characteristics of the thick disk in the Canada - France - Hawaii - Telescope Legacy Survey (CFHTLS) fields, complemented at bright magnitudes with Sloan Digital Sky Survey (SDSS) data. The ([Fe/H], Z) distributions are derived in the W1 and W3 fields, and compared with simulated maps produced using the Besançon model. It is shown that the thick disk, represented in star-count models by a distinct component, is not an adequate description of the observed ([Fe/H], Z) distributions in these fields. © Owned by the authors, published by EDP Sciences, 2012.
Czekaj M.,University of Barcelona |
Robin A.C.,Observatoire de Besancon |
Luri X.,University of Barcelona |
Figueras F.,University of Barcelona |
EAS Publications Series | Year: 2011
From the Gaia mission, kinematic and star count data, together with the physical parameters of the stars - ages and metallicities-, will allow to characterise our Galaxy populations and, from that, the overall Galactic gravitational potential. One of the promising procedures to reach such goal will be to optimise the present Population Synthesis models by fitting, through robust statistical techniques, the large and small scale structure and kinematics parameters that best will reproduce Gaia data. As a first step we present here the comparison between the data from the Tycho-2 catalogue and the Besançon Galaxy Model simulations, as well as our present and future work on the model optimization. © EAS, EDP Sciences 2011.