منابع مشابه
Comparing Tycho–2 Astrometry with Ucac1
The Tycho–2 Catalogue, released in February 2000, is based on the ESA Hipparcos space mission data and various ground–based catalogs for proper motions. An external comparison of the Tycho–2 astrometry is presented here using the first U.S. Naval Observatory CCD As-trograph Catalog (UCAC1). The UCAC1 data were obtained from observations performed at CTIO between February 1998 and November 1999,...
متن کاملThe IMF of open star clusters with Tycho – 2
We studied the fields of nine nearby open star clusters based on the Tycho–2 catalogue. We determined membership probabilities for the stars in the cluster fields from the stellar proper motions and used the Tycho–2 photometry to compute the initial mass function (IMF) of the clusters from the main sequence turn-off point down to approx. 1M⊙. We found IMF slopes ranging from Γ = −0.69 down to Γ...
متن کاملExoplanet search with astrometry
Searching for extrasolar planets by direct detection is extremely challenging for current instrumentation. Indirect methods, that measure the effect of a planet on its host star, are much more promising and have indeed led to the discovery of nearly all extrasolar systems known today. While the most successful method thus far is the radial velocity technique, new interferometric instruments lik...
متن کاملGlobal astrometry with OSI
— The Orbiting Stellar Interferometer is a proposed space-based interferometer which makes very accurate wide-angle astrometric measurements on several thousand stars. As opposed to Hipparcos, OSI does not have a “basic angle” between two separate field-of-views but three separate interferometers and a highly accurate metrology system. The questions addressed in this paper are whether it is pos...
متن کاملPulsar Astrometry with the VLBA
Many features of the Very Long Baseline Array (VLBA) contrive to make it the best telescope for pulsar astrometry. The measured proper motions and parallaxes allow distances and transverse velocities to be determined. These in turn provide clues to questions spanning nuclear astrophysics on scales of 10−23 m to the distribution of gas in the Galaxy on scales of 10 m. Three pulsars are discussed...
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ژورنال
عنوان ژورنال: The Astronomical Journal
سال: 2000
ISSN: 0004-6256
DOI: 10.1086/301474