Search Publications
Pulsation models of δ Scuti variables. I. The high-amplitude double-mode stars.
Christensen-Dalsgaard, J.; Petersen, J. O.
The relations between high-amplitude δ Scuti stars and the much more abundant low-amplitude δ Sct variables are not clear. Both groups have similar periods and seem to have almost the same basic physical properties, although their light-curve characteristics are very different. In the last few years much improved observational data have been publi…
The Flagstaff Astrometric Scanning Transit Telescope (FASTT) and Star Positions Determined in the Extragalactic Reference Frame
Monet, Alice K. B.; Monet, David G.; Stone, Ronald C. +2 more
This paper describes the methods used for determining star positions in the extragalactic reference frame with the Flagstaff astrometric scanning transit telescope (FASTT) from drift scan observations. A laser metrology system is used to correct for instrumental motions, and detailed numerical computations are made for atmospheric and room refract…
HIPPARCOS distances and mass limits for the planetary candidates: 47 Ursae Majoris, 70 Virginis, and 51 Pegasi
Evans, D. W.; Arenou, F.; Lindegren, L. +19 more
Distances to the recently-discovered planetary system candidates, 47 UMa, 70 Vir and 51 Peg, are presented, based on absolute trigonometric parallaxes from the global reduction of the ESA Hipparcos astrometry satellite data. Standard errors of the parallaxes are in the range 0.66-0.76mas (milliarcsec), with resulting distances accurate to around 1…
A new maximum likelihood method for luminosity calibrations.
Luri, X.; Figueras, F.; Torra, J. +1 more
A new statistical parallax method using the Maximum Likelihood principle is presented, allowing the simultaneous determination of a luminosity calibration, kinematic characteristics and spatial distribution of a given sample. This method has been developed for the exploitation of the Hipparcos data and presents several improvements with respect to…
Searching for VIMs: an astrometric method to detect the binary nature of double stars with a variable component
Wielen, R.
The photo-center of a close double star in which one component has a variable luminosity moves on the sky in the same rhythm as the total luminosity of the system varies in time. This provides an astrometric method to detect the binary nature of the system if more direct methods fail. We propose to call such systems `variability-induced movers', o…
Radial velocities and axial rotation for a sample of chemically peculiar stars.
Morrell, N.; Levato, H.; Grosso, M. +2 more
As part of a systematic project we have determined radial velocities and projected rotational velocities for a sample of 186 chemically peculiar stars which have been observed by the Hipparcos' satellite. The purpose is to provide necessary data to study the space velocities of peculiar stars.
On the width of the theoretical lower main sequence. Consequences for the determination of the {DELTA}Y/{DELTA}Z ratio in the solar neighbourhood.
Baglin, A.; Lebreton, Y.; Fernandes, J.
We discuss the relation between the main sequence thickness and chemical composition variations. With the help of theoretical zero-age main sequence models between 0.7 and 1.0Msun_, computed with an advanced physical description of the stellar interiors, in a range of metallicities typical from Population I stars (0.008<=Z<=0.034)…
The empirical white dwarf mass-radius relation and its possible improvement by HIPPARCOS
Schmidt, H.
The famous mass-radius relation of white dwarf stars is based on theoretical considerations. The structure of a white dwarf, and thereby its fundamental properties, are deduced from the physical properties of the degenerate electron gas. Numerical computations take temperature and evolution effects into consideration. However, the few cases in whi…
UvbyHbeta_ photometry of main sequence A type stars.
Jordi, C.; Figueras, F.; Torra, J. +1 more
We present Stroemgren uvby and Hbeta_ photometry for a set of 575 northern main sequence A type stars, most of them belonging to the Hipparcos Input Catalogue, with V from 5mag to 10mag and with known radial velocities. These observations enlarge the catalogue we began to compile some years ago to more than 1500 stars. Our catalogue inc…
The Twin Astrographic Catalog (TAC) Version 1.0
Zacharias, N.; Wycoff, G. L.; Zacharias, M. I. +1 more
A first version of the Twin Astrographic Catalog (TAC) of positions for 705,679 stars within -18°≤δ≤90° has been produced. The sky coverage of the TAC is complete to over 90% in that area. The limiting magnitude is about B =12.0. Positions are based on 4912 plates taken with the U.S. Naval Observatory Twin Astrograph (blue, yellow lens) at epochs …