Sco X-1: Hints of Periodic Variability at Radio Frequencies

摘要

We present the results of the flux density variability observations of Sco X-1 obtained during six VLA observing sessions between 1981 and 1990. The light curves indicate three timescales of flux density variation: slow, intermediate, and rapid. The rapidity of the variations sets a conservative upper limit on size of ~6 mas, assuming a distance of 200 pc, from light travel arguments for the radio-emitting regions. The corresponding brightness temperature of greater than 107 K indicates a nonthermal origin for the radio emission. A detailed analysis of the light curves suggests that the radio emission may exhibit true periodicity on timescales of ~3 hr. We also provide a prescription for accurate signal recovery and image restoration of point and extended sources when an object of varying signal is present in the synthesized beam.