Long-term X-ray variability of the microquasar system LS 5039/RX J1826.2-1450

We report on the results of the spectral and timing analysis of a BeppoSAX observation of the microquasar system LS 5039 / RX J1826.2-1450 . The source was found in a low-flux state with FX(1-10 keV) = 4.7 \times 10^ -12 cm -2 s -1, which represents almost one order of magnitude lower than a previous RXTE observation 2.5 years before. The 0.1-10 keV spectrum is described by an absorbed power-law continuum with photon-number spectral index (Gamma)=1.8(plus-minus)0.2 and hydrogen column density of NH=1.0 +0.1 -0.3*10^22 cm -2. According to the orbital parameters of the system, the BeppoSAX observation covers the time of an X-ray eclipse should one occur. However, the 1.6-10 keV light curve does not show evidence of such an event, which allows us to give an upper limit to the inclination of the system. The low X-ray flux detected during this observation is interpreted as a decrease in the mass accretion rate onto the compact object due to a decrease in the mass-loss rate from the primary.