No abstract available

[en] Observations from 600 Mark III VLBI experiments from 1979 to 1988, resulting in 237,681 acceptable pairs of group delay and phase delay rate observations, have been used to derive positions of 182 extragalactic radio sources with typical formal standard errors less than 1 mas. The sources are distributed fairly evenly above delta = -30 deg, and 70 sources have delta greater than 0 deg. Analysis with different troposphere models, as well as internal and external comparisons, indicates that a coordinate frame defined by this set of radio sources should be reliable at the 1 mas level. The right ascension zero point of this reference frame has been aligned with the FK5 by using the optical positions of 28 extragalactic radio sources whose positions are on the FK5 system. Because of known defects in the knowledge of astronomical constants, daily nutation offsets in longitude and obliquity were determined relative to an arbitrary reference day in the set of experiments. 30 refs

[en] Radio positions, angular structure data, and polarizations were measured with the NRAO interferometer at 3.71 and 11.1 cm for 18 sources whose optical identifications seem to have jets, wisps, or close companions. Optical positions were measured with the University of Texas measuring machine. In five cases, alignment within 10⁰ in position angle of the optical and the radio major axes was found. The quasar PHL 1093 (0137+012) may be similar to 3C273. There is a compact, flat-spectrum source at the quasar position and an extended, steep-spectrum component at the end of the optical jet

[en] Photoelectric and photographic data are presented for the two components of the M51 system, NGC 5194 and NGC 5195. The photoelectric observations (UBV and I) are presented as a series of drift scans with various diaphragm sizes covering the bright central and faint outer regions. These data indicate the complexity and the very large extent of the system. Colors and magnitudes of the spiral arms are presented. The I data in particular show the broad spiral features first shown photographically by Zwicky. Deep, integrated photographic plates (IIIa-J) also show the large, structured outer regions and the complex nature of the region between the two galaxies. Calibrated contour maps and integrated luminosities of the system are presented.The maximum detected extent of the system is 40 arcmin or 120kpc. If a M/L ratio of 10 is assumed, the mass in the outer envelope is equal to the mass obtained for the more familiar bright optical components.These data and their presentation in the form of photoelectric drift scans, composite photographs, contour maps, and three-dimensional plots show the marvelous complexity of the system. It would seem that the individual galaxies, NGC 5194 and NGC 5195, cannot be considered separately but must be studied in the context of their being members of the M51 system

[en] Observations of 99 suspected variable sources are presented. The observations cover periods of up to 10-1/2 yr at 2.8 cm and 7 yr at 4.5-cm wavelength. We conclude from the observations that bursts of particle generation occur in the average variable source about once every 1-1/2--2 yr. There seems to be a universal emission mechanism such that the maximum flux density S/sub max/(lambda) at wavelength lambda is proportional to lambda/sup -0.4/ for wavelengths in the range 1 to 10 cm

[en] The cooled Schottky-diode receivers used to observe millimeter-wavelength spectral lines exhibit harmonic response, that is, response in sidebands associated with harmonics of the local oscillator frequency. Ignoring this response leads to a systematic error if the line intensities are calibrated by observing braod-band noise sources. The inferred line intensities are all lower than the true values. Experimental data confirm the relevance of the effect for astronomical observations. Although the error is not large, careful observers should be aware of it for projects that require exceptionally well-calibrated data. 8 references

[en] The observational properties of extragalactic radio sources of sizes comparable with or greater than a typical galactic diameter and intrinsic luminosities at 408 MHz greater than 10 to the 23rd W/Hz are discussed. Following a survey of the major instrumental and observational techniques developed over the last three decades for the measurement of source structure, classes of radio structure that are commonly observed, including narrow edge-brightened and -darkened double sources, narrow- and wide-tailed sources and cluster halos, are described, and various taxonomic sequences of these morphologies are discussed. Means by which such physical properties as the energetics, confinement parameters, magnetic fields, sites of electron acceleration and rotation are derived from intensity and polarization distribution measurements are examined, and the observed characteristics of the various components of extended radio sources are considered in detail, including diffuse emission regions, hot spots, cores and jets. Finally, relationships of radio source morphologies to the properties of the parent galaxies and clusters are reviewed, and a model of the radio-source phenomenon is proposed

[en] The Soviet spacecraft GRANAT, to be launched in the near future, will carry the French telescope SIGMA, designed to obtain high-sensitivity images of the sky in the 30-2000 keV energy range, with an unprecedented angular accuracy. The principal objective of the experiment will be to locate and study galactic and extragalactic celestial bodies where high-energy phenomena take place. The telescope features a coded mask 2.5m away from a position-sensitive detector, surrounded by a thick anticoincidence shield. An operational life time in excess of 18 months is foreseen, so that hundreds of targets can each be observed. In this paper, we describe the key figures and the anticipated performances of the instrument in the light of the principal scientific objectives of the mission

[en] 1048 radio source positions measured with the Texas Interferometer were searched for optical identifications on glass copies of the Palomar Sky Survey E and O plates, resulting in 242 identifications and 806 blank fields. Finding charts are presented for 124 of the 125 new identifications not previously reported in the literature, and for 73 blank fields containing nearby optical objects which may be real identifications. This brings the cumulative number of Texas radio positions searched to 2015, producing 864 optical identifications and 1151 blank fields

No abstract available