Fundamental effective temperature measurements for eclipsing binary stars – I. Development of the method and application to AI Phoenicis

Abstract

Stars with accurate and precise effective temperature (Teff) measurements are needed to test stellar atmosphere models and calibrate empirical methods to determine Teff. There are few standard stars currently available to calibrate temperature indicators for dwarf stars. Gaia parallaxes now make it possible, in principle, to measure Teff for many dwarf stars in eclipsing binaries. We aim to develop a method that uses high-precision measurements of detached eclipsing binary stars, Gaia parallaxes and multi-wavelength photometry to obtain accurate and precise fundamental effective temperatures that can be used to establish a set of benchmark stars. We select the well-studied binary AI Phoenicis to test our method, since it has very precise absolute parameters and extensive archival photometry. The method uses the stellar radii and parallax for stars in eclipsing binaries. We use a Bayesian approach to obtain the integrated bolometric fluxes for the two stars from observed magnitudes, colours and flux ratios. The fundamental effective temperature of two stars in AI Phoenicis are 6199 ± 22 K for the F7 V component and 5094 ± 16 K for the K0 IV component. The zero-point error in the flux scale leads to a systematic error of only 0.2% (≈ 11 K) in Teff. We find that these results are robust against the details of the analysis, such as the choice of model spectra. Our method can be applied to eclipsing binary stars with radius, parallax and photometric measurements across a range of wavelengths. Stars with fundamental effective temperatures determined with this method can be used as benchmarks in future surveys.

Eclipsing Binaries in Dynamically Interacting Close, Multiple Systems

“…Moreover, a promising further direction is the inclusion of the modelling of the net stellar energy distribution (SED), which enables the determination of temperatures for each stellar component with precision close to or better than 1%. Recently, for example, Miller et al [266] have developed a sophisticated method for the SED modelling of totally eclipsing detached EBs, and demonstrated that, under ideal circumstances, their method is able to reach the required accuracy in the two stars' temperatures. Their method, however, cannot be adopted directly to multiple stellar systems, although it does indicate a promising direction.…”

Triply eclipsing triple stars in the northern TESS fields: TICs 193993801, 388459317, and 52041148

“…Moreover, a further fundamental question in such an accurate analysis is the precision of the effective temperatures of the binary members. Recently Miller et al (2020) have developed a new method to determine the temperatures of eclipsing binary stars with a precision better than 1%, via a careful analysis of the system's net spectral energy distribution (SED) while taking into account the components' flux ratio, as 'quasi observables', that can be measured from high quality multi-band occultation lightcurves of some totally eclipsing binaries. Unfortunately, however, due to the significant light contributions of the third stellar components in our systems, as well as the lack of flat-bottomed binary eclipses and the strongly varying profiles of the third-body eclipses, this latter rigorous method for precise SED analysis cannot be applied directly to our triples.…”

Space-Based Photometry of Binary Stars: From Voyager to TESS

“…Second, proximity effects (reflection effect, ellipsoidal effect, gravity darkening) are more complex to model and can make it impossible to determine radii to 0.1% precision (e.g., [265]). A benchmark EB must also have high-quality T eff measurements (a recent approach by Miller et al [346] is promising) and spectroscopic chemical abundances [347].…”