Multicolor Photoelectric WBVR-Observations of the CBS HZ~Her=Her~X-1 in 1986--1988

TL;DR

This study presents detailed four-color photoelectric observations of the binary HZ Her=Her X-1 over three seasons, revealing fine photometric effects and proposing a model for matter flow and hot spots in the accretion disk.

Contribution

It provides high-precision multi-color light curves and color diagrams, and introduces a model explaining inhomogeneous gas flow and hot spots in the accretion disk of HZ Her=Her X-1.

Findings

Identification of fine photometric effects in light curves.

Evidence for inhomogeneous gas flow and hot spots.

Observation of 'splashes' in Keplerian orbits.

Abstract

We present results of four-color WBVR- photoelectric observations of the close binary HZ~Her=HER~X-1 in 1986--1988. As a rule, the duration of the observations exceeded two 35-day X-ray orbital periods in the 1986--1988 observing seasons. The accuracy and length of the photoelectric observations facilitated multi-faceted studies, which enabled us to define several fine photometric effects in the light curves of the binary more precisely and attempt to interpret them in a model for the matter flow from the optical component to the accretion disk around the neutron star. This model provides a satisfactory explanation for the inhomogeneity of the gas flow and "hot spot", as well as the existence of distinct "splashes" moving in their own Keplerian orbits around the outer parts of the Keplerian disk. We present series of light curves for all the observing seasons, as well as color--color diagrams that reflect the physics of various photometric effects. The transformation coefficients for each of the instrumental systems for the three observatories at which the observations were carried out are given. Atmospheric extinction was taken into account during multi-color observations of the object, with subsequent correction for atmospheric effects with accuracies ranging from 0.003^m to 0.005^m for air masses up to M(z)=2.