15 research outputs found
Extrasolar planetary dynamics with a generalized planar Laplace-Lagrange secular theory
The dynamical evolution of nearly half of the known extrasolar planets in
multiple-planet systems may be dominated by secular perturbations. The commonly
high eccentricities of the planetary orbits calls into question the utility of
the traditional Laplace-Lagrange (LL) secular theory in analyses of the motion.
We analytically generalize this theory to fourth-order in the eccentricities,
compare the result with the second-order theory and octupole-level theory, and
apply these theories to the likely secularly-dominated HD 12661, HD 168443, HD
38529 and Ups And multi-planet systems. The fourth-order scheme yields a
multiply-branched criterion for maintaining apsidal libration, and implies that
the apsidal rate of a small body is a function of its initial eccentricity,
dependencies which are absent from the traditional theory. Numerical results
indicate that the primary difference the second and fourth-order theories
reveal is an alteration in secular periodicities, and to a smaller extent
amplitudes of the planetary eccentricity variation. Comparison with numerical
integrations indicates that the improvement afforded by the fourth-order theory
over the second-order theory sometimes dwarfs the improvement needed to
reproduce the actual dynamical evolution. We conclude that LL secular theory,
to any order, generally represents a poor barometer for predicting secular
dynamics in extrasolar planetary systems, but does embody a useful tool for
extracting an accurate long-term dynamical description of systems with small
bodies and/or near-circular orbits.Comment: 14 pages, 12 figures, 1 table, accepted for publication in Ap
A resonant-term-based model including a nascent disk, precession, and oblateness: application to GJ 876
Investigations of two resonant planets orbiting a star or two resonant
satellites orbiting a planet often rely on a few resonant and secular terms in
order to obtain a representative quantitative description of the system's
dynamical evolution. We present a semianalytic model which traces the orbital
evolution of any two resonant bodies in a first- through fourth-order
eccentricity or inclination-based resonance dominated by the resonant and
secular arguments of the user's choosing. By considering the variation of
libration width with different orbital parameters, we identify regions of phase
space which give rise to different resonant ''depths,'' and propose methods to
model libration profiles. We apply the model to the GJ 876 extrasolar planetary
system, quantify the relative importance of the relevant resonant and secular
contributions, and thereby assess the goodness of the common approximation of
representing the system by just the presumably dominant terms. We highlight the
danger in using ''order'' as the metric for accuracy in the orbital solution by
revealing the unnatural libration centers produced by the second-order, but not
first-order, solution, and by demonstrating that the true orbital solution lies
somewhere ''in-between'' the third- and fourth-order solutions. We also present
formulas used to incorporate perturbations from central-body oblateness and
precession, and a protoplanetary or protosatellite thin disk with gaps, into a
resonant system. We quantify these contributions to the GJ 876 system, and
thereby highlight the conditions which must exist for multi-planet exosystems
to be significantly influenced by such factors. We find that massive enough
disks may convert resonant libration into circulation; such disk-induced
signatures may provide constraints for future studies of exoplanet systems.Comment: 39 pages of body text, 21 figures, 5 tables, 1 appendix, accepted for
publication in Celestial Mechanics and Dynamical Astronom
THE EUROPEAN LOCATION FRAMEWORK – FROM NATIONAL TO EUROPEAN
The European Location Framework (ELF) means a technical infrastructure which will deliver authoritative, interoperable geospatial
reference data from all over Europe for analysing and understanding information connected to places and features. The ELF has
been developed and set up through the ELF Project, which has been realized by a consortium of partners (public, private and
academic organisations) since March 2013. Their number increased from thirty to forty in the year 2016, together with a project
extension from 36 to 44 months. The project is co-funded by the European Commission’s Competitiveness and Innovation
Framework Programme (CIP) and will end in October 2016. In broad terms, the ELF Project will deliver a unique gateway to the
authoritative reference geospatial information for Europe (harmonised pan-European maps, geographic and land information)
sourced from the National Mapping and Cadastral Authorities (NMCAs) around Europe and including transparent licensing. This
will be provided as an online ELF web service that will deliver an up-to-date topographic base map and also as view & download
services for access to the ELF datasets. To develop and build up the ELF, NMCAs are accompanied and collaborate with several
research & academia institutes, a standardisation body, system integrators, software developers and application providers. The
harmonisation is in progress developing and triggering a number of geo-tools like edge-matching, generalisation, transformation and
others. ELF will provide also some centralised tools like Geo Locator for searching location based on geographical names, addresses
and administrative units, and GeoProduct Finder for discovering the available web-services and licensing them. ELF combines
national reference geo-information through the ELF platform. ELF web services will be offered to users and application developers
through open source (OSKARI) and proprietary (ArcGIS Online) cloud platforms. Recently, 29 NMCAs plus the EuroGeographics –
their pan-European umbrella association, contribute to the ELF through an enrichment of data coverage. As a result, over 20
European countries will be covered with the ELF topo Base Map in 2016. Most countries will contribute also with other harmonized
thematic data for viewing or down-loading. To overcome the heterogeneity of data resources and diversity of languages in tens of
European countries, ELF builds on the existing INSPIRE rules and its own coordination and interoperability measures. ELF
realisation empowers the implementation of INSPIRE in Europe and it complements related activities of European NMCAs, e.g.
Czech Office for Surveying, Mapping and Cadastre (CUZK), which provides a large portfolio of spatial data/services and contributes
significantly to the NSDI of Czech Republic. CUZK is also responsible for the Base Register of Territorial Identification, Addresses
and Real Estates (RUIAN) – an important pillar of Czech e-Government. CUZK became an early-bird in implementing INSPIRE and
it provides to the ELF a number of compliant datasets and web services. CUZK and the Polish NMCA (GUGiK) collaborate in the
Central-European ELF Pilot (cluster) and test various cross-border prototypes. The presentation combines the national and crossborder
view and experiences of CUZK and the European perspective of EuroGeographics