RXTE/ASM observations of and the nature of the gamma-ray source LSI+61 303
Denis A. Leahy(Department of Physics and Astronomy, University of Calgary)
Abstract
An analysis of RXTE/ASM observations of the unusual binary system LSI+61 303
is presented. The x-ray light curve gives a binary period of 26.42.05 days,
and an eccentricity of 0.275
.035,
which are the best determinations to date. Previous works reported the radio
period which is variable, due to the radio outburst peak not being phase
locked to the binary period, or optical period and eccentricity which have larger
uncertainties. The multi-wavelength spectrum
of LSI+61 303 is summarized and described in terms of a physical emission model.
X-rays through gamma-rays are due to inverse Compton emission from relativistic
electrons around the pulsar. Thus the
X-ray peak gives the time of periastron passage, reported for the first time
here. The
radio emission is due to synchrotron emission of varying optical depth, which
can explain the varying spectral index. The peak of radio emission is near
apastron, which is due to reduced confining pressure on the relativistic
electron cloud and subsequent rapid expansion of the electron cloud.
CATEGORY: BLACK HOLE AND NEUTRON STAR BINARIES