Stellar and accretion disk parameters of the close binary HD 50526

TL;DR

This study combines photometric and spectroscopic data to determine the stellar and accretion disk parameters of the close binary HD 50526, revealing a complex system with a Roche lobe-filling accretion disk and detailed stellar characteristics.

Contribution

First detailed modeling of the stellar and accretion disk parameters of HD 50526 using combined photometric and spectroscopic data.

Findings

Orbital period of 6.701 days.

Detection of a Roche lobe-filling accretion disk.

Identification of the stellar types and masses.

Abstract

We present a photometric and spectroscopic study of HD 50526, an ellipsoidal binary member of the group Double Periodic Variable stars. Performing data-mining in photometric surveys and conducting new spectroscopic observations with several spectrographs during 2008 to 2015, we obtained orbital and stellar parameters of the system. The radial velocities were analyzed with the genetic PIKAIA algorithm, whereas Doppler tomography maps for the H$\alpha$ and H$\beta$ lines were constructed with the Total Variation Minimization code. An optimized simplex-algorithm was used to solve the inverse-problem adjusting the light curve with the best stellar parameters for the system. We find an orbital period of $6.701 \pm 0.001 ~\mathrm{d}$ and a long photometric cycle of $191 \pm 2 ~\mathrm{d}$. We detected the spectral features of the coldest star, and modeled it with a $\log{g} = 2.79 \pm 0.02 ~\mathrm{dex}$ giant of mass $1.13 \pm 0.02 ~\mathrm{M_{\odot}}$ and effective temperature $10500 \pm 125 ~\mathrm{K}$. In addition, we determine a mass ratio $q= 0.206 \pm 0.033$ and that the hot star is a B-type dwarf of mass $5.48 \pm 0.02 ~\mathrm{M_{\odot}}$. The $V$-band orbital light curve can be modeled including the presence of an accretion disk around the hotter star. This fills the Roche lobe of the hotter star, and has a radius $14.74 \pm 0.02 ~\mathrm{R_{\odot}}$ and temperature at the outer edge $9400 ~\mathrm{K}$. Two bright spots located in the disk account for the global morphology of the light curve. The Doppler tomography maps of H$\alpha$ and H$\beta$, reveal complex structures of mass fluxes in the system.