A Detailed Study of the Physical and Orbital Characteristics, and Eclipse Timing Variations of the Post Common Envelope Binary DD CrB

Abstract

We present an in-depth analysis of the eclipsing binary DD CrB, composed of a B-type subdwarf primary and an M-type main-sequence secondary, with the main goal of investigating its eclipse timing variations (ETVs). Our new multi-color photometric observations, radial velocity measurements, and precise eclipse timings from TESS allow us to constrain the system parameters. The Romer delay between primary and secondary minima yields a mass ratio of $q=0.299\pm 0.009$, enabling robust simultaneous modeling of the light and radial velocity curves with {\sc phoebe} 2.17. By fixing the albedo of the secondary to its maximum physically plausible value (A${}_2=1.0$), despite the degeneracy between albedo, surface temperature, and radius, we obtained a satisfactory fit, resulting in a significantly lower temperature ($T_2\sim 2360$ K) and a radius ($R_2\sim 0.16$ R${}_{\odot }$) in agreement with literature values. Using the total mass of the components and the orbital size derived from this modeling, we interpret the ETVs and find them best explained by a Jupiter-mass tertiary companion on a $\sim 13$-year orbit in all competing models, while the eccentric (e $\sim 0.46$) models perform better in terms of fit statistics.

Accepted for publication by the Monthly Notices of the Royal Astronomical Society, 18 pages, 11 figures, 5 tables