The Longterm Variability of 4u 1705-44---A Chaotic System?
Abstract
The bright low-mass X-ray binary 4U 1705-44, a bursting Atoll source, exhibits longterm aperiodic variability with a timescale of several hundred days. The All-Sky Monitor (ASM) aboard the Rossi X-ray Timing Explorer (RXTE) observed 4U 1705-44 continuously from December 1995 through January 2012. MAXI, the Japanese X-ray All-Sky Monitor aboard the International Space Station observed the source from August 2009 through the present. Combining the ASM and MAXI data sets yeilds a continuous, uninterrupted, evenly spaced time series containing over fifty cycles at the timescale of interest. We use traditional and novel time series analysis techniques to analyze the longterm variability. A phase space embedding of the flux versus its first derivative shows a strong resemblence to the canonical double-welled nonlinear Duffing osciallator. We find a range of parameters and initial conditions for which the Duffing oscillator closely follows the time evolution of 4U 1705-44. We find evidence for unstable periodic orbits embedded in the aperiodc variabiity of 4U 1705-44, and argue that the period-1 orbit has a period of ~120 days. Clear signatures of period-1, period-2 and period-3 orbits are found in the light curve. We extract these orbits from both the 4U 1705-44 and Duffing oscillator time series and compare their topological information in phase space. It appears that the X-ray long term time variability of 4U 1705-44 can be described by a Duffing oscillator. We discuss the implications of this discovery on the allowable models to describe the longterm variability of 4U 1705-44 and, by extention, to the allowable models describing the class of X-ray binaries which show high amplitude, longterm variabilty at timescales many times the orbital periods of the systems.
- Publication:
-
American Astronomical Society Meeting Abstracts #225
- Pub Date:
- January 2015
- Bibcode:
- 2015AAS...22542804B