A Long Look at LMC X-3
Abstract
The black hole binary LMC X-3 exhibits long-term intensity variations of a factor of four on a characteristic time scale of about one hundred days. Presumed periodic based on HEAO-1 data (Cowley et al. ApJ 381, 526, 1991), the RXTE/ASM reveals a more complex variation, not strictly periodic. Times between successive minima are related by rational fractions, suggesting a stable clock in the system driving a nonlinear oscillator (whose variables are the amplitudes of different modes in the accretion disk). Segments whose length are integer multiples of this clock are extracted from the ASM light curve as a base set that describes the dynamics. These are embedded in a realistic phase space, constructed from the data. LMC X-3 has been monitored with the PCA for a substantial fraction of the RXTE mission. From this well-sampled data set, we present the long-term variations in spectral parameters and their relation to the overall flux variations. These data include a dedicated block of observations covering four contiguous 1.7-day binary orbits, during a time when the overall X-ray intensity was low. Flux variations of amplitude 14 % are seen in some (though not all) binary orbits. It is becoming increasingly unlikely that the long-term flux variations in LMC X-3 are caused by an accretion disk with a simple warp, twist or tilt.
- Publication:
-
Rossi2000: Astrophysics with the Rossi X-ray Timing Explorer
- Pub Date:
- 2000
- Bibcode:
- 2000arxt.confE..20B