منابع مشابه
Hipparcos Parallaxes and Proper Motions of Cepheids and Their Implications *
A summary is given of an analysis of the Hippar-cos trigonometrical parallaxes and proper motions of classical Cepheids. It is possible for the first time to derive zero-points for the period-luminosity and period-luminosity-colour relations from paral-laxes alone, avoiding the problems of less direct methods. The results imply an increase of 8 to 10 percent in the extragalactic distance scale ...
متن کاملPrecision Astrometry with the Very Long Baseline Array: Parallaxes and Proper Motions for 14 Pulsars
Astrometry can bring powerful constraints to bear on a variety of scientific questions about neutron stars, including their origins, astrophysics, evolution, and environments. Using phase-referenced observations at the VLBA, in conjunction with pulsar gating and in-beam calibration, we have measured the parallaxes and proper motions for 14 pulsars. The smallest measured parallax in our sample i...
متن کاملVLBI astrometry of circumstellar OH masers; proper motions and parallaxes of four AGB stars
The main-line OH masers around 4 AGB stars have been observed with the NRAO Very Long Baseline Array (VLBA) at 8 epochs over a period of 2.5 years. Using a phase referencing technique, the position of the most compact maser spot of each star was monitored with respect to two extragalactic reference sources. For U Her and W Hya, we observe the most blue-shifted maser spot, while for R Cas and S ...
متن کاملParallaxes of Southern Extremely Cool Objects I: Targets, Proper Motions and First Results
We present results from the PARallaxes of Southern Extremely Cool objects (PARSEC) program, an observational program begun in April 2007 to determine parallaxes for 122 L and 28 T southern hemisphere dwarfs using the Wide Field Imager on the ESO 2.2m telescope. The results presented here include parallaxes of 10 targets from observations over 18 months and a first version proper motion catalog....
متن کاملParallaxes and proper motions for 20 open clusters as based on the new Hipparcos catalogue
Context. A new reduction of the astrometric data as produced by the Hipparcos mission has been published, claiming that the accuracies for nearly all stars brighter than magnitude Hp = 8 are improved, by up to a factor 4, compared to the original catalogue. As correlations between the underlying abscissa residuals have also been reduced by more than an order of magnitude to an insignificant lev...
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ژورنال
عنوان ژورنال: The Astronomical Journal
سال: 1999
ISSN: 0004-6256
DOI: 10.1086/300747