Optical Line Profile Variability of the B1+neutron Star

We present high-resolution spectroscopic observations of the massive X-ray binary system LS I+65 010 (2S 0114+650) in the optical wavelength region. A correlation between equivalent width and radial velocity of photospheric absorption lines is found. The systemic velocity, inferred from the weaker lines, is Vhelio −31 ± 5 km s, which, if attributed solely to the Galactic rotation curve, implies that LS I+65 010 lies within 3 kpc from the Sun. The ISM Na I D lines display 2 resolved high velocity components at Vhelio −70, −48 km s , possibly associated with gas surrounding the binary system, in addition to the −24 and −8 km s ISM features due to the Orion and Perseus arm regions, respectively. Strong photospheric line profile variability is present on a night-to-night timescale, with He I 5875 Å displaying an additional blue-shifted absorption in some of the spectra, similar to what is observed in the optical counterpart of Vela X-1. A connection between the extended blue wing and X-ray maximum is suggested. Short timescale variations in line profiles are detected on only two nights, but the evidence that these variations occur on the 2.78 hour X-ray flaring period is marginal.