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The Carlsberg Meridian Telescope: an astrometric robotic telescope

Evans, D. W.

An overview is given of the Carlsberg Meridian Telescope on La Palma, which is one of the oldest robotic telescopes, having started observing on La Palma in 1984. In the spring of 1997, a further stage of automation was made when we converted the telescope to remote operation. Since then, the telescope has been operated over the Internet from Brit…

Binary statistics from Hipparcos data - a progress report

Söderhjelm, S.

The Hipparcos data are an important source for constraining the statistical distribution functions for the binaries in the general field. The present study uses the resolved binaries (separation 0.1-10 arcsec, magnitude-differences below 4 mag) to check directly the frequency of main-sequence binaries with (linear) separations 30-500 a.u. and mass…

The proper-motion signal of unresolved binaries in the Hipparcos catalogue

Brosche, P.; Odenkirchen, M.

We present an investigation of the differences between quasi-instantaneous stellar proper motions from the Hipparcos catalogue and long-term proper motions determined by combining Hipparcos and the Astrographic Catalogue. Our study is based on a sample of about 12000 stars of visual magnitude from 7 to 10 in two declination zones on the northern a…

Pleiades luminosity function: fine structure and new Pre-MS models

Piskunov, A. E.; Schilbach, E.; Belikov, A. N.

In order to study a model-dependence of the results achieved in the previous investigations of the Pleiades luminosity function using D'Antona and Mazzitelli (1994) evolutionary tracks, we repeated the computations with the new track system by D'Antona and Mazzitelli (1997). T h e following main conclusions can be drawn: the new models agree bette…

The Hipparcos distances of open clusters and their implication on the local variations of the ΔY/ΔZ ratio.

Zinnecker, H.; Schilbach, E.; Efremov, Yu. N.

Arguments are collected to demonstrate that recent Hipparcos results on the distances of open clusters are in agreement with previous estimates in the Russian literature which have pointed to a shorter distance scale. Evidence of the absence of a universal correlation between helium and metal abundances is given. It is suggested that violations of…

Duplicity amongst HIPPARCOS stars.

Tucholke, H. -J.; Brosche, P.; Odenkirchen, M.

Stars observed by the astrometry satellite Hipparcos may be unknown double stars. A subsample of those are dangerous for the extragalactic link of Hipparcos proper motions by long-term photographic proper motions, if the time base of Hipparcos is too short to detect the orbital motion. The probability of these cases and the typical size of the pho…

Proper motions in the field of the globular cluster NGC 6934.

Tucholke, H. -J.

We measured relative proper motions with a typical accuracy of 1.0 millarcsec/year (mas/a) for 2000 stars in a 1.4 deg x 1.4 deg field around the low-latitude globular cluster NGC 6934. Four plates taken with the Bonn double refractor, spanning an epoch difference of 62 years, were digitized completely. Within the tidal radius of the cluster, we f…

Determination of the optical or physical nature of wide visual binaries by means of two-dimensional conditional probabilities

Brosche, P.; Denis-Karafistan, A.; Denis, C.

A sample consisting of 888 wide visual double stars with known relative proper motions has been processed for the HIPPARCOS input catalog. Brosche et al. (1992) applied two separate criteria on this list to discriminate statistically between physical and optical pairs. The first of these criteria uses the number density contrast, the second the ra…

Tautenburg proper motion fields

Scholz, R. -D.; Hirte, S.

The possible use of Tautenburg Schmidt plates to determine proper motions was analyzed using the new data base of the Tautenburg plate archive. All fields with at least four first epoch plates were included along with the 10 Hipparcos-Tautenburg link fields and the 17 fields in the program of the main meridional section of the Galaxy. The distribu…

Determination of Absolute Proper-Motions for the Connection of the HIPPARCOS System with a Quasi-Inertial System and the Automation of Astrometric Measurements of Tautenburg Schmidt Plates

Scholz, R. D.