High-frequency structure of Ooty occultation sources. I Sources with central components

Abstract

The NRAO three-element interferometer operating simultaneously at 2695 and 8085 MHz has been used to study 39 Ooty occultation sources which have been found to be double at 327 MHz. This paper reports on the comparison of the high- and low-frequency structures of five out of nine of the above sources which show an additional central component at the high frequencies. The spectral indices (below 10 GHz) of the central components vary from positive, nearly zero to negative values as high as -0.65. The indices of the extended components are all steeper than about -0.9. Two of the sources are also shown to have compact subcomponents within the extended components. The fraction of the total flux density within the central components of the present sample of 39 weak sources appears to be higher than among the brighter sample of 3C sources.