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Radar properties of comets: Parametric dielectric modeling of Comet 67P/Churyumov-Gerasimenko
Kofman, Wlodek; Heggy, Essam; Palmer, Elizabeth M. +3 more
In 2014, the European Space Agency’s Rosetta mission is scheduled to rendezvous with Comet 67P/Churyumov-Gerasimenko (Comet 67P). Rosetta’s CONSERT experiment aims to explore the cometary nucleus’ geophysical properties using radar tomography. The expected scientific return and inversion algorithms are mainly dependent on our understanding of the …
Electron pitch-angle diffusion in radiation belts: The effects of whistler wave oblique propagation
Krasnoselskikh, V.; Breuillard, H.; Agapitov, O. +2 more
We calculated the electron pitch-angle diffusion coefficients in the outer radiation belt for L-shell ∼4.5 taking into account the effects of oblique whistler wave propagation. The dependence of the distribution of the angle θ between the whistler wave vector and the background magnetic field on magnetic latitude is modeled after statistical resul…
Quantitative spectroscopy of Galactic BA-type supergiants. I. Atmospheric parameters
Przybilla, N.; Firnstein, M.
Context. BA-type supergiants show a high potential as versatile indicators for modern astronomy. This paper constitutes the first in a series that aims at a systematic spectroscopic study of Galactic BA-type supergiants. Various problems will be addressed, including in particular observational constraints on the evolution of massive stars and a de…
Solar cycle variations of the Cluster spacecraft potential and its use for electron density estimations
Fazakerley, A. N.; Trotignon, J. -G.; Haaland, S. +5 more
A sunlit conductive spacecraft, immersed in tenuous plasma, will attain a positive potential relative to the ambient plasma. This potential is primarily governed by solar irradiation, which causes escape of photoelectrons from the surface of the spacecraft, and the electrons in the ambient plasma providing the return current. In this paper we comb…
Neutron star masses from hydrodynamical effects in obscured supergiant high mass X-ray binaries
Walter, R.; Manousakis, A.; Blondin, J. M.
Context. A population of obscured supergiant high mass X-ray binaries has been discovered by INTEGRAL. X-ray wind tomography of IGR J17252-3616 inferred a slow wind velocity to account for the enhanced obscuration.
Aims: The main goal of this study is to understand under which conditions high obscuration could occur.
Methods: We have use…
Speckle Interferometry and Orbits of "Fast" Visual Binaries
Tokovinin, Andrei
Results of speckle observations at the 4.1 m SOAR telescope in 2012 (158 measures of 121 systems, 27 non-resolutions) are reported. The aim is to follow fast orbital motion of recently discovered or neglected close binaries and sub-systems. Here, eight previously known orbits are defined better, two more are completely revised, and five orbits are…
Ion distributions in the vicinity of Mars: Signatures of heating and acceleration processes
Fedorov, A.; Barabash, S.; Lundin, R. +5 more
More than three years of data from the ASPERA-3 instrument on-board Mars Express has been used to compile average distribution functions of ions in and around the Mars induced magnetosphere. We present samples of average distribution functions, as well as average flux patterns based on the average distribution functions, all suitable for detailed …
Nonlinear spatiotemporal evolution of whistler mode chorus waves in Earth's inner magnetosphere
Omura, Yoshiharu; Summers, Danny; Lee, Dong-Hun +1 more
We analyze the nonlinear evolution of whistler mode chorus waves propagating along a magnetic field line from their equatorial source. We solve wave evolution equations off the equator for the wave magnetic field amplitude and wave frequency, subject to boundary conditions at the equator comprising model “chorus equations” that describe the genera…
C and N abundances of main sequence and subgiant branch stars in NGC 1851
Rejkuba, M.; Milone, A. P.; Marino, A. F. +6 more
We present the first chemical analysis of stars on the double subgiant branch (SGB) of the globular cluster NGC 1851. We obtained 48 Magellan IMACS spectra of subgiants and fainter stars covering the spectral region between 3650-6750 Å to derive C and N abundances from the spectral features at 4300 Å (G-band) and at ~3883 Å (CN). We added to our s…
Germanium, Arsenic, and Selenium Abundances in Metal-poor Stars
Roederer, Ian U.
The elements germanium (Ge, Z = 32), arsenic (As, Z = 33), and selenium (Se, Z = 34) span the transition from charged-particle or explosive synthesis of the iron-group elements to neutron-capture synthesis of heavier elements. Among these three elements, only the chemical evolution of germanium has been studied previously. Here we use archive obse…