Credit: A. Smale and P. Boyd (NASA/GSFC); K. Smale (NASA/GSFC/SPS)

Compact Binary Quantization?

Compact binaries, consisting of a "normal" low mass star and a compact object (either a neutron star or black hole), are among the brightest X-ray sources in the sky, and also among the most active X-ray emitting objects, switching from faint states to bright states, apparently irregularly. Now, thanks to continuous monitoring with the All Sky Monitor (ASM) on the Rossi X-ray Timing Explorer (RXTE), astronomers Padi Boyd and Alan Smale have discovered an underlying pattern in the apparently random variations in X-ray brightness for 3 important compact binaries. Boyd and Smale found that the number of days between low points of emission can, for each source, be described as a series of integer multiples of some fundamental underlying number. For example, the neutron star binary Cygnus X-2 has an orbital period of 9.8 days. Boyd and Smale found that the time between minimum X-ray brightness is always a whole-number multiple of 9.8 days -- for example 77.7 days, 58.8 days or 49 days, which are 8, 6 and 5 times 9.8. However the multiple that will come next cannot be predicted. Boyd and Smale also looked at 2 black hole binary systems, Cygnus X-3 and LMC X-3, and found that while some integer multiple relation did exist for these systems, the integer multiple was not related to the orbital period. The image above is an artist's representation of the mass transfer in an X-ray binary system which could produce variations characterized by random integer multiples of a single constant.

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Page Author: Dr. Michael F. Corcoran
Last modified July 2, 2001