Aperiodic variability of low-mass X-ray binaries at very low frequencies

Details Aperiodic variability of low-mass X-ray binaries at very low frequencies Aperiodic variability of low-mass X-ray binaries at very low frequencies

2002-11-20

arxiv.org/abs/astro-ph/0211442v1

Astron.Astrophys. 398 (2003) 1103-1110

Astronomy and Astrophysics

Astrophysics

9 pages, 6 figures. To be published in A&A

Scientific paper

10.1051/0004-6361:20021693

We have obtained discrete Fourier power spectra of a sample of persistent low-mass neutron-star X-ray binaries using long-term light curves from the All Sky Monitor on board the Rossi X-ray Timing Explorer. Our aim is to investigate their aperiodic variability at frequencies in the range 1 x 10^{-7}-5 x 10^{-6} Hz and compare their properties with those of the black-hole source Cyg X-1. We find that the classification scheme that divides LMXBs into Z and atoll sources blurs at very low frequencies. Based on the long-term (~ years) pattern of variability and the results of power-law fits (P ~ v^{-a}) to the 1 x 10^{-7}-5 x 10^{-6} Hz power density spectra, low-mass neutron-star binaries fall into three categories. Type I includes all Z sources, except Cyg X-2, and the atoll sources GX9+1 and GX13+1. They show relatively flat power spectra (a < 0.9) and low variability (rms < 20%). Type II systems comprise 4U 1636-53, 4U 1735-44 and GX3+1. They are more variable (20% < rms < 30%) and display steeper power spectra (0.9 < a < 1.2) than Type I sources. Type III systems are the most variable (rms > 30%) and exhibit the steepest power spectra (a > 1.2). The sources 4U 1705-44, GX354-0 and 4U 1820-30 belong to this group. GX9+9 and Cyg X-2 appear as intermediate systems in between Type I and II and Type II and III sources, respectively. We speculate that the differences in these systems may be caused by the presence of different types of mass-donor companions. Other factors, like the size of the accretion disc and/or the presence of weak magnetic fields, are also expected to affect their low-frequency X-ray aperiodic varibility.

Affiliated with

Also associated with

No associations

Rating

Aperiodic variability of low-mass X-ray binaries at very low frequencies does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Aperiodic variability of low-mass X-ray binaries at very low frequencies, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aperiodic variability of low-mass X-ray binaries at very low frequencies will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-54789