The radio source 1934-63

Abstract

Observations of the radio source 1934-63 have been made at a large number of frequencies between 3:30 and 5000 Mc/s using the CSIRO 210 ft radio telescope. The spectrum is found to be broadly peaked near 1400 Mc/s. At higher frequencies, the spectral index is approximately I· 2, while below 1400 Mc/s the flux density rapidly decreases with decreasing frequency. The form of the spectrum may be explained as synchrotron radiation from relativistic electrons having an energy distribution of the form N(E) = KE-3•4 and where there is either absorption clue to free-free transitions in an ionized hydrogen region having an emission measure about 106 cm-6 pc, and an electron temperature of 104 °K, or self-absorption by the relativistic electrons. Assuming a magnetic field of 10-2 G, the angular size of the source must then be about O" • 002, the linear dimensions of the order of, or less than, 20 pc, the surface brightness about 5 X 1012 °K at 400 Mc/s, and the density of relativistic electrons about 10 cm-3• A normal power-law spectrum can also be modified at low frequencies if the synchrotron emission occurs in a region where the index of refraction is less than unity. A density of 4 X 103 electrons/cm3 is needed to produce the observed cut-off at 1400 Mc/s. The possibility that the source may be an artificial transmission from an intelligent civilization is also discussed. Measurements of the flux density below 200 Mc/s are needed to discriminate between the various models proposed to explain the spectral distribution.