scholarly journals Astrometric Desiderata for Nearby Stars

1986 ◽  
Vol 109 ◽  
pp. 653-667
Author(s):  
Wilhelm Gliese
Keyword(s):  
Proper Motions ◽  
First Line ◽  
Trigonometric Parallax ◽  
Trigonometric Parallaxes ◽  
Nearby Stars

Astrometric desiderata for nearby stars concern, in first line, the parallax measurements, avoidance and elimination of effects of bias in trigonometric parallax programs: Bias towards large proper motions, preference of parallaxes with positive accidental errors, the Malmquist bias. For some of the nearby stars we do not yet know accurate positions, for some other objects no reliable proper motions were measured. Finally, for calibrating color-luminosity relations the necessity to observe further precise trigonometric parallaxes is demonstrated and emphasized.

scholarly journals The parsec program: a large sample of brown dwarf trigonometric parallaxes

2012 ◽  
Vol 8 (S289) ◽  
pp. 48-51
Author(s):  
Alexandre H. Andrei ◽  
Richard L. Smart ◽  
Beatrice Bucciarelli ◽  
Jucira L. Penna ◽  
Federico Marocco ◽  
...  
Keyword(s):  
Proper Motions ◽  
Brown Dwarf ◽  
Large Sample ◽  
Trigonometric Parallax ◽  
Trigonometric Parallaxes

AbstractWe report on the parsec program, which observed 140 L and T dwarfs on a regular basis from 2007 to 2011, using the WIFI camera on the ESO/2.2 m telescope. Trigonometric parallaxes at 5 mas precision are derived for 49 objects, and mas yr−1-level proper motions are derived for approximately 200,000 objects in the same fields. We discuss image cleaning, object centroiding, and astrometric methods, in particular three different approaches for trigonometric parallax determination.

scholarly journals Luminosity of δ Scuti Stars After Hipparcos Satellite

1998 ◽  
Vol 11 (1) ◽  
pp. 567-567
Author(s):  
E. Antonello ◽  
L. Mantegazza ◽  
E. Poretti
Keyword(s):  
Globular Clusters ◽  
Rotational Velocity ◽  
High Amplitude ◽  
Empirical Dependence ◽  
Trigonometric Parallaxes ◽  
Nearby Stars ◽  
Observational Errors ◽  
Absolute Magnitudes ◽  
Scuti Stars ◽  
Δ Scuti Stars

The absolute magnitudes of δ Scuti stars derived from parallaxes measured by the Hipparcos satellite were compared with the previous estimates based on photometric uvby² indices, and significant differences were found which are related to photometric effects of metallicity and rotational velocity. A reliable calibration of Mv in terms of the photometric indices shall include an estimate of these effects. It is important also to take into account the possible presence of unresolved close companions in order to fully exploit the accuracy of Mv of nearby stars derived from the trigonometric parallaxes. The Mv of few bright SX Phe stars support the period-luminosity relation obtained with ground based observations of globular clusters, while it does not seem to confirm the empirical dependence of this relation on the metallicity. Some high amplitude δ Scuti stars with intermediate or normal metallicity and small and uncertain parallax have apparently a very low luminosity. Simulations of Mv determinations from observed parallaxes based on the discussion of observational errors by Lutz and Kelker (1973) have shown that the low luminosity could be an effect related to these errors.

scholarly journals Esiderata for nearby - star quantities observable with small telescope

1986 ◽  
Vol 118 ◽  
pp. 247-249
Author(s):  
W. Gliese
Keyword(s):  
Broad Band ◽  
Radial Velocities ◽  
General Assembly ◽  
New Delhi ◽  
Proper Motions ◽  
Nearby Star ◽  
Small Telescope ◽  
General Catalogue ◽  
Nearby Stars

At the General Assembly of the IAU at New Delhi van Altena reported on the new General Catalogue of Trigonometric Stellar Parallaxes (GCTSP) which was completed recently at the Yale Observatory. Time seems to be ripe now for the compilation of a Third Catalogue of Nearby Stars which will include all objects known to be nearer than 25 parsecs. This catalogue will contain positions, proper motions, radial velocities, spectral types, broad-band photometry, and parallaxes - quantities won by observations.

Desiderata for the Catalogue of Nearby Stars

1977 ◽  
Vol 35 ◽  
pp. 37-39
Author(s):  
W. Gliese
Keyword(s):  
The Sun ◽  
Royal Observatory ◽  
Trigonometric Parallaxes ◽  
Nearby Stars

In 1969 the second edition of the “Catalogue of Nearby Stars” was published. It contains 1529 single stars and systems with a total of 1890 components. The catalogue lists all stars with parallaxes equal to or larger than 0.”045. Only 1049 of these objects are nearer than 20 pc. The “Catalogue of Stars within 25 pc of the Sun”, published 1970 in the Royal Observatory Annals No. 5 consists of 1744 systems of which 1566 trigonometric parallaxes.

scholarly journals Astrometry With Schmidt Telescopes

1984 ◽  
Vol 78 ◽  
pp. 217-224
Author(s):  
C A Murray
Keyword(s):  
Reference Frame ◽  
Proper Motions ◽  
Large Area ◽  
Full Field ◽  
Potential Value ◽  
Focal Surface ◽  
Single Plate ◽  
Trigonometric Parallaxes ◽  
The Absolute

Photographic astrometry, including work with Schmidt telescopes, can be divided into two main fields, (i) the measurement of positions of objects relative to a reference frame of stars with known celestial coordinates, and (ii) the measurement of relative proper motions and trigonometric parallaxes from a series of plates taken on the same field. The former demands a knowledge of the absolute transformation between angles on the sky and measurements on a plate, whereas in the latter we are only interested in differential transformations from plate to plate. The potential value of Schmidt telescopes for both these fields of astrometry lies in the large area of sky and range of magnitude which can be imaged on a single plate. The former advantage is however, to some extent offset by the curvature of the focal surface which means that, in order to utilize the full field the plates must be constrained to the form of the focal surface during exposure.

scholarly journals Commission 24. (Stellar Parallaxes and Proper Motions.)

1933 ◽  
Vol 4 ◽  
pp. 246-247
Author(s):  
S. A. Mitchell ◽  
F. Slocum
Keyword(s):  
Systematic Errors ◽  
Proper Motions ◽  
Fundamental Assumption ◽  
Trigonometric Parallaxes ◽  
Informal Discussion ◽  
Right Ascension

There were two meetings of the Commission. The first meeting was devoted to an informal discussion of programmes for parallax work. The second session was devoted to a discussion of systematic errors. The President gave a brief summary of the two latest determinations of the systematic errors of trigonometric parallaxes, by Schlesinger (parallaxes published to 1924) and by van Maanen (parallaxes to 1927). Both investigators had used the same basis of comparison, namely, the Mt Wilson spectroscopic parallaxes, and both had made the same fundamental assumption, namely, that the systematic errors of the spectroscopic parallaxes depending on right ascension were negligible.

scholarly journals A preliminary color-magnitude diagram for late-type stars in the solar neighborhood

1959 ◽  
Vol 10 ◽  
pp. 39-40
Author(s):  
O. C. Wilson
Keyword(s):  
Main Sequence ◽  
Star Clusters ◽  
Solar Neighborhood ◽  
Late Type ◽  
Main Sequence Stars ◽  
Individual Values ◽  
Magnitude Diagram ◽  
Trigonometric Parallaxes ◽  
Nearby Stars ◽  
The Mean

Modern photoelectric techniques yield magnitudes and colors of stars with accuracies of the order of a few thousandths and a few hundredths of a magnitude respectively. Hence for star clusters it is possible to derive highly accurate color-magnitude arrays since all of the members of a cluster may be considered to be at the same distance from the observer. It is much more difficult to do this for the nearby stars where all of the objects concerned are at different, and often poorly determined, distances. If one depends upon trigonometric parallaxes, the bulk of the reliable individual values will refer to main sequence stars, and while the mean luminosities of brighter stars are given reasonably well by this method, the scatter introduced into a color-magnitude array by using individual trigonometrically determined luminosities could obscure important features. Somewhat similar objections could be raised against the use of the usual spectroscopic parallaxes which also should be quite good for the main sequence but undoubtedly exhibit appreciable scatter for some, at least, of the brighter stars.

Parallaxes and proper motions of 12 nearby stars.

1949 ◽  
Vol 55 ◽  
pp. 16 ◽  
Author(s):  
P. van de Kamp ◽  
S. L. Lippincott
Keyword(s):  
Proper Motions ◽  
Nearby Stars

scholarly journals Stellar Kinematics and Galactic Research Involving Proper Motions (Invited Paper)

1974 ◽  
Vol 61 ◽  
pp. 217-220
Author(s):  
S. V. M. Clube
Keyword(s):  
Galactic Structure ◽  
Proper Motions ◽  
Stellar Kinematics ◽  
Pilot Survey ◽  
Nearby Stars

A method of analysing proper motions as observed over all the sky is described. The kinematics of nearby stars derived from the Lick Pilot Survey are discussed, and the consequences to galactic structure examined.

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