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Photoionization Modeling of Titan’s Dayside Ionosphere
Wahlund, J. -E.; Edberg, N. J. T.; Vigren, E. +4 more
Previous modeling studies of Titan’s dayside ionosphere predict electron number densities that are roughly a factor of 2 higher than those observed by the RPWS/Langmuir probe. The issue can equivalently be described as the ratio between the calculated electron production rates and the square of the observed electron number densities resulting in r…
Dynamical Study of the Exoplanet Host Binary System HD 106515
Rica, F. M.; Barrena, R.; Henríquez, J. A. +2 more
HD 106515 AB (STF1619 AB) is a high common proper motion and common radial velocity binary star system composed of two G-type bright stars located at 35 pc and separated by about 7 arcsec. This system was observed by the Hipparcos satellite with a precision in distance and proper motion of 3 and 2%, respectively. The system includes a circumprimar…
Modern Geometric Methods of Distance Determination
Pietrzyński, Grzegorz; Thévenin, Frédéric; Falanga, Maurizio +2 more
Building a 3D picture of the Universe at any distance is one of the major challenges in astronomy, from the nearby Solar System to distant Quasars and galaxies. This goal has forced astronomers to develop techniques to estimate or to measure the distance of point sources on the sky. While most distance estimates used since the beginning of the 20t…
The Acheron Dorsum on Mars: A novel interpretation of its linear depressions and a model for its evolution
Martino, Salvatore; De Blasio, Fabio Vittorio
The Acheron Dorsum north of Olympus Mons on Mars is a unique 800 km-long arcuate ridge apparently unrelated to other adjacent morphologies. Acheron Dorsum is crossed by deep and wide fractures ("fossae", here referred to also as Linear Depressions or "LDs"), commonly interpreted as grabens formed by local lithosphere stress in response to endogeno…
Application of time transfer functions to Gaia's global astrometry. Validation on DPAC simulated Gaia-like observations
Bertone, Stefano; Bucciarelli, Beatrice; Lattanzi, Mario G. +5 more
Context. A key objective of the ESA Gaia satellite is the realization of a quasi-inertial reference frame at visual wavelengths by means of global astrometric techniques. This requires accurate mathematical and numerical modeling of relativistic light propagation, as well as double-blind-like procedures for the internal validation of the results, …
Data Timing, Time Transfer and On-board Clock Monitoring for Space Astrometry with Gaia
Butkevich, Alexey G.; Klioner, Sergei A.; Geyer, Robin +1 more
The paper discusses the problematic of data timing in the framework of the space astrometry mission Gaia. For various reasons related both to astrometry and to the measuring principles of the Gaia instrument it is mandatory to assign a highly stable and accurate time tag for each observational point. For this purpose Gaia has a Rb clock on board. …
Energy-banded ions in Saturn's magnetosphere
Thomsen, M. F.; Jackman, C. M.; Kurth, W. S. +3 more
Using data from the Cassini Plasma Spectrometer ion mass spectrometer, we report the first observation of energy-banded ions at Saturn. Observed near midnight at relatively high magnetic latitudes, the banded ions are dominantly H+, and they occupy the range of energies typically associated with the thermal pickup distribution in the in…
Resurfacing event observed in Morpheos basin (Eridania Planitia) and the implications to the formation and timing of Waikato and Reull Valles, Mars
Kostama, V. -P.; Raitala, J.; Kukkonen, S.
The large scale outflow channels of the Hellas impact basin are characteristic to its eastern rim region. Although the majority of the valles are located in the large-scale topographic trough connecting Hesperia Planum and Hellas basin, the most far-reaching of them, Reull Vallis is situated to the south-southeast of this trough cutting through Pr…
The development of magnetic field line wander in gyrokinetic plasma turbulence: dependence on amplitude of turbulence
Howes, Gregory G.; Bourouaine, Sofiane
The dynamics of a turbulent plasma not only manifests the transport of energy from large to small scales, but also can lead to a tangling of the magnetic field that threads through the plasma. The resulting magnetic field line wander can have a large impact on a number of other important processes, such as the propagation of energetic particles th…
An astrometric and spectroscopic study of the δ Scuti variable HD 21190 and its wide companion CPD -83° 64B
Ilyin, I.; Niemczura, E.; Hubrig, S. +4 more
Although pulsations of δ Scuti type are not expected among Ap stars from a theoretical point of view, previous observations of the known δ Scuti star HD 21190 indicated a spectral classification F2 III SrEuSi:, making it the most evolved Ap star known. Our atmospheric chemical analysis based on recent High Accuracy Radial velocity Planet Searcher …