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abstract: |
    We report on optical spectroscopic observations of the X-ray Transient XTE J1118+480 covering the period from April 7, 2000 to July 4, 2000. The spectrum is characterized by weak, broad, double-peaked Balmer and He lines on top of a blue continuum of slope $p \approx
    1/3$, as expected for an optically-thick accretion disk. The weak Bowen blend seen in our spectra may indicate a low metallicity for the source. The presence of a partial S-wave pattern in the He $\lambda 4686$ line appears consistent with the reported photometric period $P_{\rm orb} = 4.1$ hr for XTE J1118+480. By using a combination of Doppler mapping and various theoretical arguments, we constrain plausible orbital parameters for the system: a mass ratio $0.02 \lsim q \lsim 0.1$, an inclination $i
    \gsim 70^o$ for a neutron star primary, or $30^o \lsim i \lsim 50^o$ for a black hole primary with a mass between $4$ and $10~M_\odot$. Ca[ii]{} absorption features observed at very high resolution constrain the interstellar hydrogen absorption column $\log [N_{\rm
    H{\sc i}}~({\rm ~cm^{-2}})] \approx 20.45 \pm 0.2$ and the identification of three absorbing clouds indicate a distance to the source $\lsim 1$ kpc, assuming the line-of-sight to XTE J1118+480 