Study of the Spectral and Temporal Characteristics of X-ray Emission of the Gamma-ray Binary LS 5039 with Suzaku

摘要

We report on the results from Suzaku and previous X-ray observations on the galactic binary LS5039, a TeV γ-ray emitting binary. The Suzaku observation which covered continuously more than one orbital period revealed strong X-ay flux modulation at the orbital period for the first time, with its close resemblance to the TeV γ-ray light curve. The X-ray data up to 70keV measured with Suzaku are described by a hard power-law spectrum with a phase-dependent photon index which varies within Γ=1.45-1.6. We also found that the modulation curves are surprisingly stable in 1999-2007. The long-term behavior of the non-thermal X-ray light curves over eight years favors that a scenario in which the radiation is related to an ultrarelativistic pulsar wind would be able to account for the stable clock-like X-ray/TeV γ-ray behaviors.