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Jauncey, D.

Publications and source records attributed to Jauncey, D..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

22 GHz VLBI Survey: Status Report and Preliminary Results

A ground-based VLBI survey to measure the visibilities and correlated flux densities in continuum at 22 GHz of more than 140 extragalactic radio sources has been conducted with baselines up to approximately 11 000 km. The project has been designed to help in preparation of target lists for VSOP and Radioastron Space VLBI missions as well as providing observational data for statistical study of structural properties at 22 GHz on sub-milliarcsecond scales for this large sample of extragalactic sources.

VLBI extragalactic radio sources survey↗
NASA NTRS1992

A speckle hologram of the interstellar plasma

Observations of a speckle hologram of scattering material along the line of sight to the Vela pulsar indicate that this material is concentrated in the Vela supernova remnant, deep within the Gum Nebula. The speckle hologram is observed through the amplitude and phase variations of the interferometric cross-power spectrum with time and frequency. These variations describe the density fluctuations of the interstellar plasma, in a holographic fashion. The decorrelation due to the phase variations of the speckles yields the angular size of the scattering disk; comparison with the bandwidth of their amplitude variations yields a characteristic distance from earth to the scattering material of 0.81 +/- 0.03 of the distance from earth to the pulsar. This result is consistent with theories of irregularities associated with particle acceleration in shocks in supernova remnants.

Desai, K. M.↗
NASA NTRS1991

Speckles in interstellar radio-wave scattering

Observations of speckles in the scattering disk of the Vela pulsar are presented and speckle techniques for studying and circumventing scattering of radio waves by the turbulent interstellar plasma are discussed. The speckle pattern contains, in a hologrammatic fashion, complete information on the structure of the radio source as well as the distribution of the scattering material. Speckle observations of interstellar scattering of radio waves are difficult because of their characteristically short timescales and narrow bandwidths. Here, first observations are presented, taken at 13 cm wavelength with elements of the SHEVE VLBI network, of speckles in interstellar scattering.

Desai, K. M.↗
NASA NTRS1988

VLBI observations of Supernova 1987 A

VLBI observations at 2.3 GHz of SN1987 A on February 28, 1987 yielded no fringes, implying, for an optically thin shell, a lower bound on the (outer) diameter of 1.9 mas. From the comparison of the VLBI and optical results, it is inferred that the radiosphere of SN1987 A was either about equal to, or larger than, the photosphere of the supernova five days after the explosion.

Shapiro, I.↗
NASA NTRS1978

Deflection of polarised radiation - Relative phase delay technique

The article discusses the geodesic motion of photons, considering particularly whether oppositely polarized photons fall at the same rate. It is assumed that orthogonally polarized photons would be equally deflected by the gravitational field of a nonrotating mass. Upon the introduction of rotation, the angular momentum of the deflecting source couples to the photon spin through gravitational field action. Thus there arise separate trajectories for orthogonal polarizations. Searching for changes in polarization in a deflected beam is accomplished by a relative phase delay technique. If the beam is split into orthogonal linear polarization, final polarization is elliptical. Experiments have been performed on searching for ellipticity developments in the linearly polarized carrier waves from Helios 1 and 2, and the results are presented.

Dennison, B.↗