Modeling of 35-day superorbital cycle of $B$ and $V$ light curves of IMXB HZ Her/Her X-1. (arXiv:2009.07181v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kolesnikov_D/0/1/0/all/0/1">D. A. Kolesnikov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shakura_N/0/1/0/all/0/1">N. I. Shakura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Postnov_K/0/1/0/all/0/1">K. A. Postnov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Volkov_I/0/1/0/all/0/1">I. M. Volkov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bikmaev_I/0/1/0/all/0/1">I. F. Bikmaev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Irsmambetova_T/0/1/0/all/0/1">T. R. Irsmambetova</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Staubert_R/0/1/0/all/0/1">R. Staubert</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wilms_J/0/1/0/all/0/1">J. Wilms</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Irtuganov_E/0/1/0/all/0/1">E. Irtuganov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Golyshev_P/0/1/0/all/0/1">P. Yu. Golyshev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shugarov_S/0/1/0/all/0/1">S. Yu. Shugarov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nikolenko_I/0/1/0/all/0/1">I. V. Nikolenko</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Trunkovsky_E/0/1/0/all/0/1">E. M. Trunkovsky</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schonherr_G/0/1/0/all/0/1">G. Sch&#xf6;nherr</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schwope_A/0/1/0/all/0/1">A. Schwope</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Klochkov_D/0/1/0/all/0/1">D. Klochkov</a>

The X-ray binary Her X-1 consists of an accreting neutron star and the
optical component HZ Her. The 35-day X-ray superorbital variability of this
system is known since its discovery in 1972 by the Uhuru satellite and is
believed to be caused by forced precession of a warped accretion disk tilted to
the orbital plane. We argue that the observed features of the 35-day optical
variability of HZ Her can be explained by free precession of the neutron star
with a period close to that of the forced disk. The model parameters include a)
the X-ray luminosity of the neutron star; b) the optical flux from the
accretion disk; c) the tilt of the inner and outer edges of the accretion disk.
A possible synchronization mechanism based on the coupling between the neutron
star free precession and the dynamical action of non-stationary gas streams is
discussed.

The X-ray binary Her X-1 consists of an accreting neutron star and the
optical component HZ Her. The 35-day X-ray superorbital variability of this
system is known since its discovery in 1972 by the Uhuru satellite and is
believed to be caused by forced precession of a warped accretion disk tilted to
the orbital plane. We argue that the observed features of the 35-day optical
variability of HZ Her can be explained by free precession of the neutron star
with a period close to that of the forced disk. The model parameters include a)
the X-ray luminosity of the neutron star; b) the optical flux from the
accretion disk; c) the tilt of the inner and outer edges of the accretion disk.
A possible synchronization mechanism based on the coupling between the neutron
star free precession and the dynamical action of non-stationary gas streams is
discussed.

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