Close Binary Perspectives

Abstract

Development of analytic binary star models is discussed in historical and on-going perspective, beginning with an overview of paradigm shifts, the merits of direct (rectification-free) models, and fundamental four-type binary system morphology. Attention is called to the likelihood that many or even most cataclysmic variables may be of the double contact morphological type. Eclipsing binary distance estimates differ from those of standard candles in being individually measurable—without reliance on (usually nearby) objects that are assumed similar. Recent progress on circumstellar accretion disk models is briefly summarized, with emphasis on the separate roles of fluid dynamic, structural, and analytic models. Time-related parameters (ephemeris, apsidal motion, and light travel time) now can be found with a unified algorithm that processes light curves, velocity curves, and pre-existing eclipse timings together, without need to compute any new timings. Changes in data publication practices are recommended and logical errors and inconsistencies in terminology are noted. Parameter estimation strategies are discussed.

Light and Period Variations in Two K-type Contact Binaries: HI Leo and V523 Cas

“…To study the period variations, we computed the eclipse timing residuals, whose naming was suggested by Wilson (2020). We applied the nonlinear least-squares fitting method with weights, which are inversely proportional to the squared errors.…”

Fifty Years of Eclipsing Binary Analysis with the Wilson–Devinney Model

“…Here the same comment applies: This approach appears so natural, but it was a conceptual breakthrough; • Constrained solutions, including all morphological types based on Roche geometry, that is, the surfaces of both stars are modeled as equipotential surfaces: Detached, semi-detached, over-contact types (see Wilson [3] for the basic idea) and the fourth morphological type (double contact, DBC) (Wilson [6]-paragraph 5, Wilson [7]).…”

“…We focus mainly on modeling ideas and principles rather than the WD computer program (briefly covered in Section 4) that is based on the WDM. Because the WDM and WD programs are the most widely used light curve modeling tools, it seems appropriate to describe its foundations, features, capabilities, and continuing development in some detail; also see Wilson [7] for a recent publication on desirable developments for the field.…”

“…The fourth morphological type, double-contact, was introduced by Wilson [3], (Wilson [6], paragraph 5) and Wilson [7]. This previously unrecognized morphological type, for which the name double-contact binary was suggested by Wilson, is a binary in which both stars fill their limiting lobes and at least one spins faster than synchronously, so that the components do not touch, even at one point (rotation reduces lobe size).…”

“…The WDP consists of two programs-LC and DC-for modeling and analyzing binary star observables, cf. Wilson [7]. Program LC generates light and RV curves, spectral line profiles, images, conjunction times, and timing residuals.…”