BF Pavonis (AB)b?

An overlooked brown dwarf found via timing in W UMa-type binary BF Pavonis. Minimum mass about 25 +/13 M_Jup.

BVRI Photometric Observations, Light Curve Solutions and Orbital Period Analysis of BF Pav

Quote :

A new ephemeris, period change analysis and light curve modeling of the W UMa-type eclipsing binary BF Pav are presented in this study. Light curves of the system taken in BVRI filters from two observatories in Australia and Argentina were modeled using the Wilson-Devinney code. The results of this analysis demonstrate that BF Pav is a contact binary system with a photometric mass ratio q=1.460+_0.014, a fillout factor f=12.5%, an inclination of 87.97+_0.45 deg and a cold spot on the secondary component. By using the distance modulus formula, the distance of BF Pav was calculated to be d=268+_18 pc which is in good agreement with the Gaia EDR3 distance. We obtain an orbital period increase at a rate of 0.142 s/century due to a quadratic trend in the O-C diagram. Also, an alternative sudden period jump probably has occurred which could be interpreted as a rapid mass transfer from the lower mass star to its companion about DeltaM=2.45*10^(-6) Msun. Furthermore, there is an oscillatory behavior with a period of 18.3+_0.3 yr. Since BF Pav does not seem to have significant magnetic activity, this behavior could be interpreted as the light-time effect caused by an undetected third body in this system. In this case, the probability for the third body to be a low mass star with M>=0.075 Msun or a brown dwarf is 5.4% and 94.6% respectively. If we assume i'=90deg, a_3=8.04+_0.33 AU. The mass of the secondary component was also determined using two different methods which result close to each other.

Nice find! How do you manage to find these ancient artifacts in the literature?

Sirius_Alpha wrote:

Nice find! How do you manage to find these ancient artifacts in the literature?

A magician never reveals his own tricks.

Here is also something very interesting too, but it seems not accessible

Orbital Period Analysis of Four Eclipsing Binaries XY Boo, RW Com, MR Del and AK Her

Quote :

The orbital period variations of the eclipsing binaries XY Boo, RW Com, MR Del, and AK Her are investigated. This study includes the first orbital period analysis of the detached eclipsing binary MR Del and necessary updates for the remaining stars with addition of new mid-eclipse times calculated from our recent observations carried out at Ankara University Kreiken Observatory. The analysis shows that the period variations may result from mass exchange/loss and a third body for XY Boo, two additional bodies for RW Com, a substellar third component for MR Del, and mass exchange/loss, additional bodies and/or magnetic activity for AK Her. The hypothetical third component of MR Del with an estimated mass of 0.069 M⊙, appears to be very close to the borderline between stars and brown dwarfs.

I'm interested in what's hiding in RW Com system... in the meantime I have to settle for CC Com...

Orbital Period Changes and Their Evolutionary Status for Weak-Contact Binaries. II. CC Comae Berenices and BV Draconis

Quote :

Based on O − C curves, we present detailed period investigations of two weak-contact binaries CC Com and BV Dra. It is found that the periods of these two binaries have varied in a cyclic variation way superposed on a secular period change. The periods and amplitudes of the cyclic variations are P3 = 23.6(±0.4) yr and A = 0.^d0028(±0.^d0003) for CC Com and P3 = 23.8(±0.6) yr and A = 0.^d0029(±0.^d0003) for BV Dra. The cyclic oscillations for these two stars may be attributed to the light-time effect via an unseen third body, which could extract angular momentum from the central system. If the existence of the additional body is true, CC Com and BV Dra may be triple system stars. For CC Com, the secular period decrease rate is dP/dt = -0.20 × 10^-7 d yr^-1, which suggests that the mass transfers from the more massive component to the less massive one, accompanied with the angular momentum loss due to mass outflow from L2. A decrease in its orbital period will result in the shrinking of the inner and outer critical Roche lobes, and then cause the contact degree to increase. This kind of weak-contact binary with a long-term period decrease may evolve into a deep contact configuration. For BV Dra, the continuous period increase rate is dP/dt = +0.29 × 10^-7 d yr^-1, indicating that the mass transfers from the less massive component to the more massive one. An increase in its orbital period may cause the separation between both components to increase, and thus the contact configuration will break, as predicted by thermal relaxation oscillation theory. Therefore, this kind of weak-contact binary with a secular period increase will evolve into a broken-contact configuration.

There is something out there too...

Given the existence of mass transfer in contact binary stars, I'd rather see some independent confirmation method in addition to timing variations. IIRC similar oscillations in 44 Boötis BC resulted in companion orbits that would be unstable due to the outer A–BC orbit.