منابع مشابه
High-precision VLBI astrometry of radio-emitting stars
Multiple-epoch phase-referenced VLBI observations of 11 radio-emitting stars have been conducted as part of an astrometric program to link the Hipparcos optical reference frame to the radio extragalactic reference frame. We present the VLBI positions, proper motions and trigonometric parallaxes from this program in the ICRF (International Celestial Reference Frame). These astrometric parameters...
متن کاملImproved VLBI astrometry of OH maser stars
Aims. Accurate distances to evolved stars with high mass loss rates are needed for studies of many of their fundamental properties. However, as these stars are heavily obscured and variable, optical and infrared astrometry is unable to provide enough accuracy. Methods. Astrometry using masers in the circumstellar envelopes can be used to overcome this problem. We have observed the OH masers of ...
متن کاملRadio astrometry with chromatic AGN core positions
Aims. The effect of frequency-dependent AGN core positions (“core-shifts”) on radio Very Long Baseline Interferometry (VLBI) global astrometry measurements is investigated. Methods. The basic equations relating to VLBI astrometry are reviewed, including the effects of source structure. A power-law representation of core-shifts, based on both observations and theoretical considerations of jet co...
متن کاملStars in the age of micro-arc-second astrometry
The understanding and modeling of the structure and evolution of stars is based on statistical physics as well as on hydrodynamics. Today, a precise identification and proper description of the physical processes at work in stellar interiors are still lacking (one key point being that of transport processes) while the comparison of real stars to model predictions, which implies conversions from...
متن کاملAstrometry of the OH masers of 4 Mira stars
The OH main line masers in circumstellar shells were observed with astrometric VLBI in order to accurately determine the position of the star, as well as its motion, including the parallax. Results are presented on 4 Mira stars monitored for 2-8 years with the VLBA. The data show that in some stars the VLBI detection is dominated by blue-shifted emission that is associated with the stellar imag...
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ژورنال
عنوان ژورنال: Monthly Notices of the Royal Astronomical Society
سال: 1991
ISSN: 0035-8711,1365-2966
DOI: 10.1093/mnras/250.3.576