We present soft X-ray spectroscopy of the black hole binary LMC X-3 from the XMM-Newton Reflection Grating Spectrometer .
The observations span the full range of spectral states seen in LMC X-3 .
The spectra are completely dominated by continuum emission , and the neutral absorbing column measured from the O I edge ( N _ { H } = 3.8 ^ { +0.8 } _ { -0.7 } \times 10 ^ { 20 } cm ^ { -2 } ) is consistent with the Galactic interstellar column density towards LMC X-3 .
We find no evidence for variability of the neutral absorbing column .
We also constrain the ionized column density using the upper limits to the equivalent width of the O II – O VIII K-shell resonance lines : we find that the equivalent hydrogen column density of gas in which O is partially ionized is < 8 \times 10 ^ { 20 } cm ^ { -2 } .
From this upper limit we can rule out a line driven stellar wind as the power source for the X-ray emission of LMC X-3 except when it is faint .
At wavelengths longward of the peak emission the spectral shape is well described by a multi-temperature disk-blackbody spectrum ; the powerlaw component which dominates at shorter wavelengths does not continue longward of the disk-blackbody peak .
This implies that the multi-temperature disk-blackbody component supplies the seed photons which are Compton upscattered in the hot corona , consistent with the standard paradigm for black hole X-ray binary spectral states .