The column density towards LMC X-1

Abstract

We measure the neutral absorption towards the black hole X-ray binary system LMC X-1 from six archival soft X-ray spectra obtained with the gratings and/or CCD detectors on Chandra, XMM-Newton, and Swift. Four spectral models for the soft continuum have been investigated. While the powerlaw model may overestimate NH considerably, the others give consistent results. Taking the lower metalicity of the Large Magellanic Cloud into account, we find equivalent hydrogen column densities of N_H = (1.0-1.3)*10^22 cm^-2, with a systematic dependence on the orbital phase. This variation of the neutral absorption can nearly explain the orbital modulation of the soft X-ray flux recently detected with the All Sky Monitor (ASM) on the Rossi X-ray Timing Explorer (RXTE).

4 pages, accepted for publication as a Letter in Astronomy and Astrophysics

References in corpus (4)

• A Determination of the Spin of the Black Hole Primary in LMC X-1
• A New Dynamical Model for the Black Hole Binary LMC X-1
• Pulse phase resolved analysis of the HMXB Cen X-3 over two binary orbits
• Hysteresis of spectral evolution in the soft state of black-hole binary LMC X-3

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