Physics of Eclipsing Binaries. IV. The Impact of Interstellar Extinction on the Light Curves of Eclipsing Binaries

Abstract

Traditionally, the effects of interstellar extinction on binary star light curves have been treated as a uniform reduction in the observed brightness of the system that is independent of orbital phase. However, unless the orbital plane of the system coincides with the plane of the sky, or if the two stars are completely identical and present with minimal mutual irradiation and tidal/rotational distortions, then this is unlikely to be an accurate representation of the effect of interstellar extinction. Here, we present an updated treatment of interstellar extinction as incorporated in the PHOEBE 2.2 release (publicly available from http://phoebe-project.org) and assess the importance of using such an approach in the modeling of different types of binary systems. We also present the incorporation of PHOENIX model atmospheres into the PHOEBE 2.2 release, providing increased fidelity on computed observables down to lower temperatures than previously available. The importance of these new code developments is then highlighted via an extincted toy model of the eclipsing white-dwarf-subdwarf binary SDSS J235524.29+044855.7 -demonstrating that, in the age of LSST as well as complementary space-based photometric missions, a proper accounting for extinction and as well as the use of realistic model atmospheres will be essential in deriving accurate binary parameters.

Physics of Eclipsing Binaries. V. General Framework for Solving the Inverse Problem

“…PHOEBE 2.0 introduced automatic interpolated limb-darkening by default (see Prša et al 2016, Section 5.2.3), in addition to manual coefficients for linear, logarithmic, quadratic, square-root, and power laws. PHOEBE 2.2 (Jones et al 2020) then included the ability to automatically query coefficients for any of the built-in laws, on a per-surface-element basis.…”

“…PHOEBE is one of many modeling codes which operates by discretizing the gravitationally distorted surface of each stellar component, populating the discretized grid with local quantities from atmosphere tables, and integrating over visible elements at any given time in the orbit to synthesize model observables. Until now, all releases since the 2.0 release (Prša et al 2016;Horvat et al 2018;Jones et al 2020) have been focused on adding advanced physics and precision to the forward-model and leaving the inverse problem to the user.…”

A tidally tilted sectoral dipole pulsation mode in the eclipsing binary TIC 63328020

“…We now proceed to analyse the system parameters via simultaneous fitting of the TESS orbital light curve as well as the RV points using the next-generation Wilson-Devinney code PHOEBE2 we used was defined by Choi et al (2016) as: X = 0.7154, Y = 0.2703, and Z = 0.0142 (taken from Asplund et al 2009). (Prša et al 2016;Horvat et al 2018;Conroy et al 2020;Jones et al 2020). First, we removed the pulsations from the light curve.…”

Consequences of parameterization choice on eclipsing binary light curve solutions

“…To understand the observations, one needs to employ models capable of making predictions with sufficient precision, so that it is possible to compare the observations with predicted theoretical values. A popular example of such software is PHOEBE (Prša et al, 2016;Horvat et al, 2018;Jones et al, 2020), a robust Python package for modeling of EB systems. The latest release provides users with control over a large number of orbital and physical parameters, which allows them to generate synthetic light curves and radial velocities of the binary system.…”

“…emcee) and optimizers (e.g. Nelder-Mead) to solve the inverse problem-for a comprehensive introduction to the inverse problem using PHOEBE see Conroy et al (2020).…”