Planetary/substellar third bodies in eclipsing binary systems

Hereby I'm proposing to open a dedicated topic to substellar third bodies detected around eclipsing double systems (including degenerate systems too) and merge other similar threads about the same topic with it, so as to these don't fill the forum with redundant threads.

This is the starting thread concerning a circumbinary brown dwarf companion to RU Ursae Minoris system

Photomeric analysis of eclipsing binaries: VY UMI, RU UMI AND GSC 04364-00648

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We present the photometric analysis of BVR and TESS light curves of three eclipsing binaries (RU UMi and purely studied VY UMi, GSC 04364-00648), together with their period changes considering archival data and new minima times from our and TESS observations. For the first time we detected wave-like variations with low-amplitude in O−C residua of RU UMi, which can be interpreted as a consequence of the light-time effect caused by the 3rd invisible component with period 7370 days. Period increase with rate 2.56(9)×10^-7~d/yr^-1 detected in the VY UMi system corresponds to mass transfer from the secondary to the primary component. For GSC 04364-00648 binary system we find some quadratic changes on the O−C diagram, which corresponds to a period decrease with a high rate of −2.26(5)×10^-5 d/yr^-1. We cannot assumptions about their nature, mainly due to short time of observation and uneven coverage of O−C diagram. We also determined the absolute parameter of their components using the photometric solution and GAIA distances.

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According to the mass function of the 3rd body f(m₃) and masses of the binary components (see Tab. 6), we can find that the minimum mass of the 3rd component in the case of the edge-on orbit (sini₃ = 1) should be M₃=0.063(16)M⊙ ∼ 60M_J. It corresponds to a low massive red dwarf or more probably (due to its mass) it is a brown dwarf (Joergens 2014) with very low luminosity. It is supported also by the results of the photometric solution, where no 3rd light was detected.

Merging a few threads

1 - Confirmed substellar third body around FS Aur with slightly different orbital solution
Revisiting FS Aurigae and its triple cataclysmic variable system hypothesis

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A very long term variability (VLPP), with period of 875 days, was observed in the long-term light curve of FS Aurigae in 2011. This periodicity was calculated on 6 cycles. We re-examine the periodicity with new observations over of the past 5 yrs. A total of 18 yrs of observations confirm the hypothesis of a third body perturbing in a secular way the cataclysmic variable (CV). Improvements to the model such as eccentric and inclined orbits for the third body and a binary post-Newtonian correction are considered. We confirm the VLPP of FS Aur and find the new period of 857 ± 78 days. The secular perturbations are most efficient when the mass of the third body is M=29 MJ, much less than the 50 MJ reported in 2011. We estimate the effect of the third body on the mass transfer rate and the brightness of the system. We consider alternative scenarios for the VLPP. The new data and analysis supports the hypothesis that FS Aur is a CV in a triple system.

2 - Interesting system: circumternary brown dwarf at NSVS 7453183

A photometric study of NSVS 7453183: a probable quadruple system with long-term surface activity

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The VRC light curves were regularly measured for the eclipsing binary NSVS 7453183 as a part of our long-term observational project for studying of low-mass eclipsing binaries with a short orbital period and surface activity. The TESS light curve solution in Phoebe results to the detached configuration, where the temperature of primary component was adopted to T1 = 4300 K according to the SED approximation. It gives us T2= 4080 ± 100 K for the secondary component. The spectral type of the primary component was estimated to be K6 and the photometric mass ratio was derived q=0.86. We confirm presence of the third body in this system, a stellar companion with a minimal mass 0.33 MSun orbiting the eclipsing pair with a short period about 425 days, and propose the next, fourth body with a longer orbiting period of about 12 years, probably a brown dwarf with the minimal mass of 50 MJup. The hierarchical structure ((1+1)+1)+1 of this quadruple system is assumed. Characteristics and temporal variations of the dark region on the surface of the primary component were estimated. The average migration speed of about 10 deg/month was found during years 2020-2022.

3 - NSVS 11868841 (AB)b

NSVS 11868841: An active detached eclipsing binary system with a substellar object

Quote :

Four-color CCD photometric light curves (LCs) of eclipsing binary (EB) NSVS 11868841 are presented in this paper. These LCs are analyzed by using the 2013 version of the Wilson-Devinney (W-D) code. We found that NSVS 11868841 is a late-type low-mass detached EB with an orbit inclination nearly 90 ° . The LCs are asymmetric, especially in its out-of-eclipse. Based on all available times of the light minimum, we analyzed the variations of the orbital period by using the (O- C) method. The O-C curve shows a cycle oscillation with a period of 11.83(± 0 . 04) years and an amplitude of 0.0009 days (∼ 1.3 min). This cyclic change detected in NSVS 11868841 could be explained by the light-travel time effect (LTTE) via the presence of a third body. Subsequently, we calculated the mass of this third component as M3sin(i3)=0.047(± 0 . 015)M⊙. If the third body is coplanar with the central system, it may be a brown dwarf. And this discovery will provide important insights on the formation and evolution of brown dwarf companions.