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 multicolour photometric observations, radial velocity measurements, and precise eclipse timings from Transiting Exoplanet Survey Satellite allow us to constrain the system parameters. The Rømer delay between primary and secondary minima yields a mass ratio of $q = 0.299 \pm 0.009$, enabling robust simultaneous modelling of the light and radial velocity curves with 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 modelling, we interpret the ETVs and find them best explained by a Jupiter-mass tertiary companion on a ${\sim} 13$-yr orbit in all competing models, while the eccentric (e$\sim 0.46$) models perform better in terms of fit statistics.