Canonical Timing and Spectral Behavior of LMC X-3 in the Low/Hard State

We present results from three observations with the Rossi X-Ray Timing Explorer (RXTE) of LMC X-3, obtained while the source was in an extended low/hard state. The data reveal a hard X-ray spectrum that is well fit by a pure power law with photon index Γ = 1.69 ± 0.02, with a source luminosity at 50 kpc of (5-16) × 1036 ergs s-1 (2-10 keV). Strong broadband (0.01-100 Hz) time variability is also observed, with fractional rms amplitude 40% ± 4%, plus a quasi-periodic oscillation (QPO) peak at 0.46 ± 0.02 Hz with rms amplitude ~14%. This is the first reported observation in which the full canonical low/hard state behavior (pure hard power-law spectrum combined with strong broadband noise and QPO) for LMC X-3 is seen. We reanalyze several archival RXTE observations of LMC X-3, derive consistent spectral and timing parameters, and determine the overall luminosity variation between high/soft and low/hard states. The timing and spectral properties of LMC X-3 during the recurrent low/hard states are quantitatively similar to that typically seen in the Galactic black hole candidates.