Abstract
Context: Low mass X-ray binaries were found to have very low frequency breaks
in their power density spectra below which the power density spectra are nearly
in white noise structure and at higher frequencies they approximately follow
the $P_\nu \propto \nu^{-1.3}$ law.
Aims: In 2005, Gilfanov and Arefiev studied X-ray variability of persistent
LMXBs in the $10^{-8}-10^{-1}$ Hz frequency range and
To determine whether high mass X-ray binary power density spectra have
similar properties and the findings for low mass X-ray binaries are also valid
for high mass binaries, we analyzed the time series of high mass X-ray binary
sources produced by All Sky Monitor of Rossi X-ray Timing Explorer.
Method: We obtained the power density spectra of the high mass X-ray binaries
using the cosine transform of autocorrelation function.
Results: We identified break frequencies for seven sources, namely OAO
1657-415, SS 433, Vela X-1, SMC X-1, 4U 1700-377, GX 301-2, and LMC X-1. The
normalized break frequencies with respect to the orbital frequency
($f_{break}/f_{orbit}$) for sources OAO 1657-415, SS 433, SMC X-1 and LMC X-1
are consistent with those of Roche lobe overflow systems. The other high mass
X-ray binary systems, Vela X-1, GX 301-2, and 4U 1700-377, however, have larger
break frequency ratios, $f_{break}/f_{orb} $, which are indicative of short
viscous times. These are all wind-accreting sources and the stellar winds in
the systems allow the formation of only short radius discs.
Consequently, we qualitatively distinguished the Roche lobe overflow binaries
from the wind accreting system by comparing their normalized break frequencies.