Search Publications
Hipparcos, the New Reduction
van Leeuwen, Floor
An overview is presented on why and how the new reduction of the Hipparcos data was carried out, and in particular on how improved understanding of the dynamics of the Hipparcos satellite was obtained and made the new reduction possible. A brief description is given of the main torques acting on the spacecraft and some peculiar features in the sat…
Origin of the Local Bubble
Breitschwerdt, Dieter; de Avillez, Miguel A.; Fuchs, Burkhard +1 more
We present a new unbiased search for OB associations in the Solar neighbourhood which have hosted the progenitor stars of the core collapse supernovae responsible for the Local Bubble in the interstellar gas. For this purpose we have analyzed a volume complete set (with a diameter of 400 pc) of B stars drawn from the Hipparcos catalogue and the Ar…
What Physical Processes Drive the Interstellar Medium in the Local Bubble?
Dettbarn, C.; Breitschwerdt, D.; Fuchs, B. +1 more
Recent 3D high-resolution simulations of the interstellar medium in a star forming galaxy like the Milky Way show that supernova explosions are the main driver of the structure and evolution of the gas. Its physical state is largely controlled by turbulence due to the high Reynolds numbers of the average flows. For a constant supernova rate a dyna…
Dynamic Modelling of the Hipparcos Attitude
van Leeuwen, Floor; Fantino, Elena
We present a new method for a high-accuracy reconstruction of the attitude for a slowly spinning satellite. This method, referred to as the fully-dynamic approach, explores the possibility to describe the satellite's attitude as that of a rigid body subject to continuous external torques. The method is tried out on the Hipparcos data and is shown …
A Detailed Analysis of the Operational Orbit of the Hipparcos Satellite
van Leeuwen, Floor; Dalla Torre, Andrea
An analysis of the orbital evolution of the ESA's Hipparcos satellite is presented. Hipparcos operated between August 1989 and March 1993 in a highly elliptical orbit: a geostationary transfer orbit with increased perigee height. The requirements of the scientific mission included high accuracy knowledge of the position and velocity vectors of the…
Modelling the Torques Affecting the Hipparcos Satellite
van Leeuwen, Floor; Fantino, Elena
Reconstructed attitude data for the Hipparcos mission as obtained in the final stages of the data analysis for the published catalogue is used to derive detailed information on the dynamics of the satellite. Most elements of the inertia tensor of the satellite could be calibrated from the observed acceleration data, which are also used to reconstr…
The Operational Environment of the Hipparcos Mission
van Leeuwen, Floor; Penston, Margaret J.
We investigate links between the observational environment as experienced by the Hipparcos satellite and the performance of the spacecraft and payload instrumentation, with particular emphasis on finding out whether some of these effects may have been inadequately represented in instrument calibrations and could thus have affected the scientific r…
Introduction to a Further Examination of the Hipparcos Data
van Leeuwen, Floor; Fantino, Elena
We present an introduction to four papers on further analysis of the raw Hipparcos data. This analysis has lead to the recognition of how orbit, radiation and temperature conditions did or didn't affect the scientific results of the Hipparcos mission. It also led the way to a new reduction of the scientific data that shows from its initial results…
Primordial Helium and DeltaY/DeltaZ from H II Regions and from Fine Structure in the Main Sequence Based on HIPPARCOS Parallaxes
Girardi, L.; Høg, E.; Pagel, B. E. J. +3 more
The primordial helium abundance YP is important for cosmology and the ratio DeltaY/DeltaZ of the changes relative to primordial abundances constrains models of stellar evolution. While the most accurate estimates of YP come from emission lines in extragalactic H II regions, they involve an extrapolation to zero metallicity which itself is closely …
Lithium Abundance in Pop.II Stars A post-HIPPARCOS discussion
Spite, M.; Hill, V.; Spite, F.
The relation between the lithium abundance observed in Population II stars and the primordial abundance, is still an open question (see Cayrel and Duncan, this meeting). A few recent results are discussed. HIPPARCOS data show that the standard model of stellar evolution can explain the 6Li detection in HD 84937, suggesting a negligible depletion o…