  IC 10 X-1 is an eclipsing high mass X-ray binary (HMXB) containing a
stellar-mass black hole (BH) and a Wolf-Rayet (WR) donor star with an orbital
period of P = 34.9 hr. This binary belongs to a group of systems that can be
the progenitors of gravitational wave sources, hence understanding the dynamics
of systems such as IC 10 X-1 is of paramount importance. The prominent He II
4686 emission line (previously used in mass estimates of the BH) is out of
phase with the X-ray eclipse, suggesting that this line originates somewhere in
the ionized wind of the WR star or in the accretion disk. We obtained 52
spectra from the GEMINI/GMOS archive, observed between 2001 and 2019. We
analyzed the spectra both individually, and after binning them by orbital phase
to improve the signal-to-noise ratio. The RV curve from the stacked data is
similar to historical results, indicating the overall parameters of the binary
have remained constant. However, the He II line profile shows a correlation
with the X-ray hardness-ratio values, also, we report a pronounced skewness of
the line-profile, and the skewness varies with the orbital phase. These results
support a paradigm wherein the He II line tracks structures in the stellar wind
that are produced by interactions with the BH's ionizing radiation and the
accretion flow. We compare the observable signatures of two alternative
hypotheses proposed in the literature: wind irradiation plus shadowing, and
accretion disk hotspot; and we explore how the line-profile variations fit into
each of these models.
