Comparison of the X-ray properties of x Persei and. gamma. Cassiopeiae
We examine the X-ray properties of the main-sequence Be stars X Per and ..gamma.. Cas and conclude that the latter is a widely separated binary system containing an accreting neutron star. The X-ray spectra in the 2--20 keV band are very similar and can be characterized by approx.10 keV thermal emission. A high-energy excess in the spectrum of X Per, spectral variations across the X Per pulse, and the lack of any iron emission at 6.7 keV from both ..gamma.. Cas and X Per suggest that the emission is not truly thermal and that we are using a simple spectral model to approximate the complex emission from the magnetic pole of an accreting neutron star. No X-ray pulsations greater than approx.5% and 15% semiamplitude are detected from ..gamma.. Cas for periods from 80 ms to 15 minutes and from 15 to 20 minutes, respectively; this is in contrast to X Per's 13.9 minute X-ray pulsations with approx.40% semiamplitude. Noncoherent variations in the X-ray flux of both ..gamma.. Cas and X Per on time scales of approx.10 minutes probably reflect stellar wind inhomogeneities with a typical size of < or approx. =1 R/sub sun/. The long-term optical brightness variations of X Per are not directly correlated with the X-ray flux, although a gradual factor of 5 reduction in the X-ray flux of X Per between 1972 and 1980 may be related to a 0.5 mag decline in the optical brightness in 1973. X Per pulse timings rule out orbital periods of less than 40 days. The observed X-ray luminosities, combined with the lower limits to orbital motion, indicate mass loss rates greater than 8 x 10/sup -8/ v/sup 4//sub 3/M/sub sun/ yr/sup -1/ and greater than 9 x 10/sup -8/v/sup 4//sub 3/ M/sub sun/ yr/sup -1/ from X Per and ..gamma.. Cas, respectively, where ..nu../sub 3/ is the wind velocity in 1000 km s/sup -1/.ess from main-sequence OB stars.
- Research Organization:
- Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center
- OSTI ID:
- 5637976
- Journal Information:
- Astrophys. J.; (United States), Vol. 263:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
BINARY STARS
NEUTRON STARS
STELLAR WINDS
X-RAY SPECTRA
COSMIC X-RAY SOURCES
MAIN SEQUENCE STARS
RADIATION FLUX
STAR ACCRETION
VARIABLE STARS
X RADIATION
COSMIC RAY SOURCES
ELECTROMAGNETIC RADIATION
IONIZING RADIATIONS
RADIATIONS
SPECTRA
STAR EVOLUTION
STARS
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources