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Sco-X-1: Hints of Periodic Variability at Radio Frequencies
1998 Award Winner
Charles F. Bradshaw, The MITRE Corporation
E. B. Fomalont, National Radio Astronomy Observatory
B. J. Geldzahler, Institute for Computational Sciences and Informatics, Center for Earth Observing and Space Research, George Mason University
ABSTRACT
The results of the flux density variability observations of Sco X-1 obtained during six VLA observing sessions between 1981 and 1990 are presented. 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 107K 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.
Publication
Published in May 1997. The Astrophysical Journal, Vol. 481, pp. 489-499.
Additional Search Keywords
radiation mechanisms, nonthermal, radio continuum, stars, individual, Scorpius X-1
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