Photoelectric Absorption in the Stellar Wind of the Binary System 4U 1538-52/QV Nor

Abstract

We have used the Rossi X-ray Timing Explorer (RXTE) observatory to analyze the persistent X-ray source 4U 1538-52/QV Nor. The RXTE satellite observed close to one complete binary orbit on January 1997 and 2001 of this X-ray binary system. We have obtained orbital phase resolved spectra to investigate changes in the absorption column density with orbital phase. The variation of the column density over the binary orbit is caused by the movement of the X-ray source through the stellar wind of the companion star. A simple model of absorption in a stellar wind from the companion star described the orbital phase dependence reasonably. From our analysis, we have inferred a wind mass-loss rate from the companion star of (1.3-2.5) ×10-6M/yr. Such rate is in agreement with those obtained by the Ginga observations of this X-ray binary pulsar.