A Photometric and Spectrophotometric Study of MR Cygni

Abstract

A self-consistent, physically accurate program suite has been used in an accurate simulation of new spectroscopy and photometry of MR Cygni. Analysis of both the spectroscopic and photometric data used spectrum synthesis techniques and a synthetic photometry augmentation of a light synthesis program package. The theoretical light curves closely fit the observational data. The same self-consistent parameters from the light synthesis solution produced synthetic spectra precisely fitting the observed spectra at all orbital phases. The IRAF-reduced spectroscopy has produced an accurate double-lined radial velocity curve. The derived mass ratio differs greatly from photometric mass ratios in the literature. New UBV photometry closely replicates existing data and indicates photometric stability of the binary system. A synthetic spectrum fitted to IUE data established the primary component Teff. The light curve solution determined a single set of system parameters used to calculate U, B, and V light curves. We conclude that MR Cygni is a member of the relatively rare class of hot Algol systems defined by Popper. It is likely that mass transfer still is in progress, but there is no evidence, either from orbital period variation or from a bright spot on the mass gainer, for its existence. The lack of Hα emission in any of our spectra, including one at phase 0.063, suggests a small current rate of mass transfer. The fact that our computationally self-consistent procedure has successfully represented both the photometry and the spectroscopy for a binary system whose components are appreciably distorted demonstrates the overall power of the procedure.