scholarly journals Optical Positions And Proper Motions Of Selected Radio Stars

1988 ◽  
Vol 133 ◽  
pp. 455-459
Author(s):  
H.M. Schwerdtfeger ◽  
R. Hering ◽  
H.G. Walter ◽  
H. Jahreiß
Keyword(s):  
Base Line ◽  
Proper Motions ◽  
Input Catalogue ◽  
Radio Stars

From a list of 275 confirmed or potential radio stars proposed to the Hipparcos input catalogue we selected about 80 objects which either lie outside the conventional astrometric catalogues or which are SAO-stars having declinations less than −17°. The positions of these stars were derived from measurements on POSS, SRC, and ESO(B) plates using reference stars from the SAO catalogue for the northern candidates, and from the Perth 70 catalogue for the southern candidates, respectively. The epochs of our positions fall in the middle of the fifties and seventies. For 52 stars other epochs were supplied by observations taken from literature. We determine proper motions from these positions which provide a base-line up to 35 years.

scholarly journals The Role of Observation With Horizontal Meridian Circle in China for Establishing an Inertial Frame

1990 ◽  
Vol 141 ◽  
pp. 142-142
Author(s):  
Li Zhi-gang ◽  
Qi Guan-Rong
Keyword(s):  
Inertial Frame ◽  
Minor Planets ◽  
Meridian Circle ◽  
Horizontal Meridian ◽  
Proper Motions ◽  
The Earth ◽  
The Future ◽  
History Of ◽  
Radio Stars

While HIPPARCOS is expected to measure positions and proper motions with more accuracy than those obtained by ground-based instruments, what can we do in the future for ground-based instruments? The observations with them still are important for establishing an inertial frame because of the long history of observations with them and improvements in the instruments. Moreover, it is necessary to have data of observations from them for research on problems related to the Earth. The horizontal meridian circle in China (DCMT) is expected to have advantage over the classical meridian circles. The DCMT will be assembled and tested this year. It should work in the following fields: (1) observing radio stars, (2) observation of minor planets, (3) absolute determinations of IRS.

scholarly journals Accuracy Assessment of Hipparcos Optical and VLA Radio Positions of Stars

1993 ◽  
Vol 156 ◽  
pp. 377-380
Author(s):  
H. G. Walter ◽  
R. Hering ◽  
H. Lenhardt ◽  
Chr. deVegt ◽  
D.R. Florkowski ◽  
...  
Keyword(s):  
Radio Emission ◽  
Reference Frame ◽  
Accuracy Assessment ◽  
Optical Emission ◽  
Relative Orientation ◽  
Large Array ◽  
Proper Motions ◽  
Data Noise ◽  
Very Large Array ◽  
Radio Stars

Optical positions of some 30 radio stars derived from 12 months of HIPPARCOS measurements are compared with their radio positions obtained with the Very Large Array (VLA). — Once the lengths of arcs between optical and radio positions of pairs of stars are calculated the differences of the arcs are formed. They provide an estimate of the coincidence of the optical and radio emission centres. — From the comparison of optical and radio positions infinitesimal rotation angles of the HIPPARCOS frame with respect to the VLA extragalactic reference frame are determined by rigid rotations. After taking account of the relative orientation of the frames the standard deviations of the remaining residuals are approximately of the order of the VLA observation errors, thus demonstrating the reliability of the HIPPARCOS results. However, they also indicate some data noise very likely caused by the low accuracy of optical proper motions used to bridge the HIPPARCOS-radio epoch differences up to 9 years, and possible discrepancies of radio-optical emission centres of some stars.

scholarly journals Compilation of the Hipparcos Input Cataloguean Extensive Use of Schmidt Sky Surveys

1984 ◽  
Vol 78 ◽  
pp. 225-227 ◽  
Author(s):  
C. Turon-Lacarrieu
Keyword(s):  
Southern Hemisphere ◽  
Proper Motions ◽  
Sky Surveys ◽  
Sky Survey ◽  
Photometric Measurements ◽  
Input Catalogue

The ESA Astrometry satellite Hipparcos is due to be launched in early 1988. It will measure very precise positions, parallaxes and proper motions for about 100 000 stars. However, in order to be included in the Input Catalogue, the programme stars should have positions and magnitudes known in advance with respective accuracies of about 1" and 0.5 magnitude. This will require new astrometric and photometric measurements and observations. Sky Survey Schmidt plates will be extensively used, especially for astrometric measurements in the Southern hemisphere.

scholarly journals Results of VLBI Observations of Radio Stars and Their Potential for Linking the HIPPARCOS and Extragalactic Reference Frames

1986 ◽  
Vol 109 ◽  
pp. 779-788 ◽  
Author(s):  
Jean-Francois Lestrade ◽  
Robert A. Preston ◽  
Arthur E. Niell ◽  
Robert L. Mutel ◽  
Robert B. Phillips
Keyword(s):  
Reference Frame ◽  
Binary Systems ◽  
Reference Frames ◽  
Proper Motions ◽  
Vlbi Observations ◽  
Angular Extent ◽  
The Future ◽  
Radio Stars

VLBI observations of bright radio stars have been initiated in an attempt to measure the positions and proper motions of their radio components in order to tie the future HIPPARCOS stellar frame to a VLBI extragalactic reference frame. Through VLBI observations of a sample of 20 known radio stars we have identified 11 stars that should be appropriate for both astrometric VLBI and HIPPARCOS observations. Our measurements indicate that the angular extent of their radio emitting regions is small, i.e. < 3 milliarcseconds for 7 of them. Most of these radio stars belong to the RS Canum Venaticorum class of binary systems.

scholarly journals Astrometric Positions and Proper Motions of 19 Radio Stars

2003 ◽  
Vol 126 (1) ◽  
pp. 484-493 ◽  
Author(s):  
D. A. Boboltz ◽  
A. L. Fey ◽  
K. J. Johnston ◽  
M. J. Claussen ◽  
C. de Vegt ◽  
...  
Keyword(s):  
Proper Motions ◽  
Radio Stars

scholarly journals A Preliminary Study on The Improvement of Proper Motions For HipparcosStars by Using Photographic Plates

1998 ◽  
Vol 11 (1) ◽  
pp. 552-552
Author(s):  
W. Jin ◽  
Z. Tang ◽  
J. Li ◽  
S. Wang
Keyword(s):  
Variable Stars ◽  
Open Clusters ◽  
Proper Motions ◽  
Preliminary Study ◽  
Radio Stars ◽  
Made In

The 3435 photographic plates, which were obtained by using the 40cm astrograph at Zô-Sè station of Shanghai Observatory during 1901-1993, have been accumulated for observing open clusters, extragalatic nebulas, radio stars and variable stars etc. These plates cover 764 unoverlapping regions (2°.3 * 1°.7) on the sky. Most of the plates distribute along the ecliptic, about 10 000 Hipparcos stars, 27 000 PPM stars and 500 FK5 stars are included in these regions. Among these plates, there are 2718 plates having two observing epochs, and they cover 359 different regions; there are 142 and 92 regions where the intervals of two epochs are about 50 and 70 years, and the numbers of plates in these regions are about1494 and 1023 respectively. About 372 plates were photographed before 1949,which play an important action for improvement of proper motions of Hipparcos stars. Four methods used to improve the proper motions for Hipparcos stars were designed. If the 2718 plates mentioned above having two epochs were used for improvement of the proper motions of Hipparcos stars, the stellar number of 299, 1378, 377 and 1664 corresponding to the four methods will be obtained with final precision 0.7 mas/yr. If supplementary observations are made in 1997, the stellar number of 494, 2431, 1534 and 2899 will be obtained with the same precision.

scholarly journals Tycho Astrometry and Photometry

1986 ◽  
Vol 109 ◽  
pp. 625-635 ◽  
Author(s):  
E. Høg
Keyword(s):  
Data Reduction ◽  
Proper Motions ◽  
Satellite Attitude ◽  
Input Catalogue

The HIPPARCOS Star Mappers were designed to determine the satellite attitude by observation of stars with known positions. ESA has now enhanced them so that the continuous photon counts from two photo multipliers with B and V response will be recorded. The records will be used to derive an astrometric and photometric catalogue, the TYCHO Catalogue, complete to about B=11 mag and thus containing about 500 000 stars. The positions, annual proper motions and parallaxes will have an accuracy of about 0.03 arcsec and the magnitudes one of 0.03 mag.The instrument is described and some aspects of the data reduction are discussed, namely the evaluation of a photon record by means of numerical filters, and the use of a TYCHO Input Catalogue.

scholarly journals New Proper Motions for HIPPARCOS Stars

1992 ◽  
Vol 9 ◽  
pp. 399-399
Author(s):  
H. Jahreiß ◽  
F. Crifo ◽  
Y. Réquième
Keyword(s):  
Northern Hemisphere ◽  
Positional Error ◽  
Meridian Circle ◽  
Proper Motions ◽  
Mean Error ◽  
Input Catalogue

During the preparation of the Hipparcos Input Catalogue precise positions were measured very recently by the Bordeaux automatic meridian circle (BMC) for about 5500 stars in the northern hemisphere. On average eight observations were made for each star at a mean epoch 1987. The estimated mean error in α is 0″.12 and in δ 0″. 18. With 2555 stars almost half the BMC sample lies in the declination zone -2° < δ < +32°. In this zone the (x,y) measurements of all Astrographic Catalogue plates have been newly reduced (S. Röser, priv. comm.). So, at least two independent positions are available for practically all stars down to the limiting magnitude of the AC with epochs around 1910 and with a mean positional error of 0”. 28. A combination of these two sources should provide proper motions to an accuracy of 0″. 004 yr−1.

scholarly journals Absolute Proper Motions of the Dwarf Spheroidal Galaxies in Draco and Ursa Minor

1994 ◽  
Vol 161 ◽  
pp. 535-539 ◽  
Author(s):  
R.-D. Scholz ◽  
M.J. Irwin
Keyword(s):  
Proper Motion ◽  
Globular Clusters ◽  
Reduction Process ◽  
Systematic Errors ◽  
Base Line ◽  
Proper Motions ◽  
Dwarf Spheroidal Galaxies ◽  
Accuracy Level ◽  
Ursa Minor ◽  
The Mean

Palomar and Tautenburg Schmidt plates with a base line of about 35 years have been measured with the Automated Photographic Measuring (APM) system in Cambridge (UK) in order to obtain the proper motions of the Galactic dwarf spheroidal satellites (dSph) in Draco and Ursa Minor with respect to a well defined extragalactic reference frame. The investigations were encouraged by the accuracy level achieved for the mean absolute proper motions of galactic globular clusters (0.05 arcsec/century from 25 years base line Tautenburg plate pairs) which is comparable to the expected proper motion of the Draco and Ursa Minor dSph assuming tangential motions of about 100 km/s. Different methods for the removal of systematic errors in the absolute proper motion introduced by the measuring and reduction process are discussed. The more accurate relative proper motions of individual stars in both dSphs obtained by Stetson (1980) and by Cudworth, Olszewski &amp; Schommer (1986) provide an external comparison and are also used to obtain the mean absolute proper motion of the dSphs.

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