Results 31 to 40 of about 909 (203)
Overview and Status of the International Celestial Reference Frame as Realized by VLBI
Universe, 2022 Accurate measurement of angular positions on the sky requires a well-defined system of reference that is realized with accessible objects. The purpose of this study is to review the international standard realization of such a system, the International ...
Aletha de Witt +3 more
doaj +1 more source
Masses and Densities of Dwarf Planet Satellites Measured with ALMA
The Planetary Science Journal, 2023 We have used the Atacama Large Millimeter/submillimeter Array to measure precise absolute astrometric positions and detect the astrometric wobble of dwarf planet Orcus and its satellite Vanth over a complete orbit.
Michael E. Brown, Bryan J. Butler
doaj +1 more source
VLBI Astrometry of Radio-Emitting Stars [PDF]
Symposium - International Astronomical Union, 1995 High-accuracy astrometric VLBI observations of 7 radio stars are presented with applications to the connection between the Hipparcos and VLBI extragalactic reference frames, to the identification of the radio emitting region in the ternary system Algol and the detectabity of Jupiter-size planet orbiting the radio star σ2 CrB.
J.-F. Lestrade +6 more
openaire +1 more source
Dynamical masses of young stellar objects with the VLBA: DYNAMO-VLBA
Astronomy & AstrophysicsWe present results from a multi-epoch Very Long Baseline Array (VLBA) survey of compact radio sources in the Orion complex, conducted within both the DYNAMO–VLBA and GOBELINS projects.
Dzib Sergio A. +11 more
doaj +3 more sources
Probing the Heart of Active Narrow-line Seyfert 1 Galaxies with VERA Wideband Polarimetry
The Astrophysical Journal, 2023 We explored the parsec-scale nuclear regions of a sample of radio-loud narrow-line Seyfert 1 galaxies (NLSy1s) using the VLBI Exploration of Radio Astrometry wideband (at a recording rate of 16 Gbps) polarimetry at 22 and 43 GHz.
Mieko Takamura +11 more
doaj +1 more source
Science with radio pulsar astrometry [PDF]
Proceedings of the International Astronomical Union, 2012 AbstractHigh precision astrometry on radio pulsars can provide model-independent estimates of their distances and velocities. Such estimates serve to calibrate models of the Galactic electron density distribution, thereby improving distance estimates for the entire pulsar population.
openaire +1 more source
Ray tracing-based delay model for compensating gravitational deformations of VLBI radio telescopes
Journal of Geodetic Science, 2022 The precision and the reliability of very long baseline interferometry (VLBI) depend on several factors. Apart from fabrication discrepancies or meteorological effects, gravity-induced deformations of the receiving unit of VLBI radio telescopes are ...
Lösler Michael +6 more
doaj +1 more source
Improving the Accuracy of Radio Astrometry [PDF]
International Astronomical Union Colloquium, 2000 AbstractThe International Celestial Reference Frame (ICRF) is currently realized by the radio positions of compact extragalactic objects obtained by the technique of Very Long Baseline Interferometry (VLBI). The positions of the defining sources with the highest quality are estimated to be accurate at the 0.25 milliarcsecond (mas) level.
openaire +1 more source
Improving the Reference Frame by Radio–and Optical Astrometry of Radio Stars [PDF]
International Astronomical Union Colloquium, 1991 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.
Chr. de Vegt +3 more
openaire +1 more source
Radio source structures in VLBI astrometry [PDF]
Symposium - International Astronomical Union, 1988 In astrometry, celestial radio sources with extended structures are useful. An algorithm to correct for structure in VLBI delays and delay rates is developed. The radio source NRAO140 is mapped from data with limited u-v coverage by the hybrid method and the Maximum Entropy procedure.
Patrick Charlot +2 more
openaire +1 more source