Engineering topics

Skjerve, Lyle

Publications and source records attributed to Skjerve, Lyle.

4 records

NASA NTRS1989

The Southern Hemisphere VLBI experiment

Six radio telescopes were operated as the first Southern Hemisphere VLBI array in April and May 1982. Observations were made at 2.3 and 8.4 GHz. This array provided VLBI modeling and hybrid imaging of celestial radio sources in the Southern Hemisphere, high-accuracy VLBI geodesy between Southern Hemisphere sites, and subarcsecond radio astrometry of celestial sources south of declination -45 deg. The goals and implementation of the array are discussed, the methods of modeling and hybrid image production are explained, and the VLBI structure of the sources that were observed is summarized.

Preston, Robert A.↗

NASA NTRS1989

The high-resolution structure of the Centaurus A nucleus at 2.3 and 8.4 GHz

VLBI observations of the nucleus of Centaurus A have been made at two frequencies with an array of five Australian radio telescopes as part of the Southern Hemisphere VLBI Experiment. Observations were made at 2.3 GHz with all five antennas, while only two were employed at 8.4 GHz. At 2.3 GHz seven tracks in the (u,v) plane with coverage of 6-8 hr each were obtained, yielding significant information on the structure of the nuclear jet. At 8.4 GHz a compact unresolved core was detected as well. It is found that the source consists of the compact self-absorbed core, a jet containing a set of three knots extending from 100 to 160 mas from the core, and a very long, narrow component elongated along the same position angle as the knots. The allowable range for the position angle of the jet is 51 + or - 3 deg, in agreement with that of the radio and X-ray structure on arcsecond and arcminute scales. The jet has brightened at 2.3 GHz by about 4 Jy, a factor of nearly 3, since the early 1970s, 1.8 Jy of which has occurred in the last 2 yr with no discernable changes in structure.

Meier, David L.↗

NASA NTRS1989

VLBI observations at 2.3 GHz of the compact galaxy 1934-638

VLBI observations of the strong radio source 1934-638 show it to be a binary with a component separation of 42.0 + or - 0.2 mas, a position angle of 90.5 + or - 1 deg, and component sizes of about 2.5 mas. The results imply the presence of an additional elongated component aligned with, and between, the compact double components. The sources's almost equal compact double structure, peaked spectrum, low variability, small polarization, and particle-dominated radio lobes suggests that it belongs to the class of symmetric compact double sources identified by Phillips and Mutel (1980, 1981, 1982).

Tzioumis, Anastasios K.↗

NASA NTRS1989

Radio structure at 8.4 GHz in Sagittarius A, the compact radio source at the Galactic center

VLBI observations of the compact, nonthermal radio source at the Galactic center show it to be elongated at 8.4 GHz along a position angle of 82 + or - 6 deg. The source has an axial ratio of 0.53 + or - 0.10 with a major axis of 17.4 + or - 0.5 mas. Examination of VLA maps of the Galactic center region indicate no obvious alignment with this smaller-scale elongation of the nuclear region, nor is the nuclear position angle aligned with the axis of Galactic rotation. Comparison with the size measured at frequencies from 1 to 22 GHz shows that the size follows very closely the lambda-squared dependence expected from interstellar scattering. The alongated nature of the source implies either that the scattering medium is anisotropic or that some remnant of the intrinsic structure remains visible through the scattering medium.

Jauncey, David L.↗