scholarly journals Improving the Reference Frame by Radio–and Optical Astrometry of Radio Stars

1991 ◽  
Vol 127 ◽  
pp. 246-249 ◽  
Author(s):  
Chr. de Vegt ◽  
N. Zacharias ◽  
K.J. Johnston ◽  
R. Hindsley
Keyword(s):  
Reference Frame ◽  
Southern Hemisphere ◽  
Radio Stars

AbstractA longterm program of precise radio – and optical astrometry of selected radio stars has been conducted in the last decade by our observatories using the VLA and astrographs on both hemispheres. Positions of 54 stars north of −26 deg. declination including 6 MASER stars have been obtained. The program status and some results from the southern hemisphere are reported.

Linking the Radio and Optical Frames with Merlin

1998 ◽  
Vol 179 ◽  
pp. 389-391 ◽  
Author(s):  
S.T. Garrington ◽  
R.J. Davis ◽  
L.V. Morrison ◽  
R.W. Argyle
Keyword(s):  
Reference Frame ◽  
The Future ◽  
Celestial Reference Frame ◽  
Radio Stars

MERLIN positions of 12 radio stars are used to link the provisional Hipparcos reference frame to the International Celestial Reference Frame. The accuracy of the link using these radio stars is 2.3 milliarcseconds. Further observations are planned to check the accuracy of the link in the future.

scholarly journals The Possibility to Link Radio and Optical Reference Frames With Artificial Satellites

1990 ◽  
Vol 141 ◽  
pp. 194-194
Author(s):  
Tong Fu
Keyword(s):  
Reference Frame ◽  
Reference Frames ◽  
Artificial Satellites ◽  
Radio Sources ◽  
Bl Lac Objects ◽  
Extragalactic Radio Sources ◽  
Bl Lac ◽  
Optical Reference ◽  
Radio Stars ◽  
Fundamental Reference

Based on extragalactic radio sources, a new high precision extragalactic radio reference frame can be established from radio interferometric measurements. To link the optical fundamental reference frame presently represented by the FK4/5 to the extragalactic radio frame, the optical counterparts of extragalactic radio sources (quasars, BL Lac objects etc.) and radio stars are the most important classes of objects. Besides these two classes of objects, are there any other objects which can be used to link the optical and radio frames? A posible answer is that artificial satellites could be a candidate class of objects contributing to this subject.

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 OPTICAL SPECTRA OF CANDIDATE SOUTHERN HEMISPHERE INTERNATIONAL CELESTIAL REFERENCE FRAME (ICRF) RADIO SOURCES

2011 ◽  
Vol 142 (5) ◽  
pp. 165 ◽  
Author(s):  
O. Titov ◽  
D. L. Jauncey ◽  
H. M. Johnston ◽  
R. W. Hunstead ◽  
L. Christensen
Keyword(s):  
Reference Frame ◽  
Southern Hemisphere ◽  
Optical Spectra ◽  
Radio Sources ◽  
Celestial Reference Frame

A radio optical reference frame. III - Additional radio and optical positions in the Southern Hemisphere

1992 ◽  
Vol 103 ◽  
pp. 2090 ◽  
Author(s):  
J. L. Russell ◽  
D. L. Jauncey ◽  
B. R. Harvey ◽  
G. L. White ◽  
J. E. Reynolds ◽  
...  
Keyword(s):  
Reference Frame ◽  
Southern Hemisphere ◽  
Optical Reference

scholarly journals Research on the Errors in Determination of Precise Optical Positions of Radio Sources

1990 ◽  
Vol 141 ◽  
pp. 499-500
Author(s):  
Lu Chun-Lin ◽  
Li Dong-Ming
Keyword(s):  
Reference Frame ◽  
Radio Sources ◽  
Optical Reference ◽  
Observation Program ◽  
Radio Stars

To link the optical reference frame to extragalactic radio frame, an observation program is in progress in Purple Mountain Observatory (PMO) and Shanghai Observatory. In this program, 70 extragalactic sources will be observed with the 1.56 m astrometric reflector in Shanghai. The secondary reference stars are determined with the twin astrograph (D = 40 cm, f = 300 cm) in PMO, and about 50 radio stars and some bright extragalactic sources will be observed with the twin astrograph.

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.

Linking the optically bright Gaia frame to the third International Celestial Reference Frame

2021 ◽  
Author(s):  
Susanne Lunz ◽  
James Anderson ◽  
Ming H. Xu ◽  
Robert Heinkelmann ◽  
Oleg Titov ◽  
...  
Keyword(s):  
Reference Frame ◽  
European Space Agency ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
The Third ◽  
Long Baseline ◽  
Data Release ◽  
Radio Frequencies ◽  
Celestial Reference Frame ◽  
Radio Stars

&lt;p&gt;The new data release of the Gaia satellite operated by the European Space Agency recently published its 3rd data release (Early Data Release 3, EDR3). The dataset contains astrometric data of about 1.8 billion objects detected at optical frequencies and therefore it outperforms any catalog of astrometric information up to date. The reference frame defined by Gaia EDR3 is aligned to the International Celestial Reference System by referring to counterparts in its realization, the third International Celestial Reference Frame (ICRF3), which is calculated from very long baseline interferometry (VLBI) observations of extragalactic objects at radio frequencies. &lt;br&gt;The Gaia dataset is known to be magnitude-dependent in terms of astrometric calibration. As the objects in ICRF3, although bright at radio frequencies, are mostly faint at optical frequencies, the optically bright Gaia frame has to be linked to ICRF3 by additional counterparts besides objects in ICRF3. The non-rotation of the optically bright Gaia frame is especially important as optically bright objects can, besides astrophysical studies, be used for navigation in space, where other geodetic systems like global navigation satellite systems are out of reach. Suitable additional counterparts are radio stars which are observed by VLBI relative to extragalactic objects in ICRF3. We discuss the orientation and spin differences between the optically bright Gaia EDR3 and VLBI data of radio stars and their impact on the Gaia data usage.&lt;/p&gt;

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