Planet Hunters TESS IV: a massive, compact hierarchical triple star system TIC 470710327

Abstract

We report the discovery and analysis of a massive, compact, hierarchical triple system (TIC 470710327) initially identified by citizen scientists in data obtained by NASA’s Transiting Exoplanet Survey Satellite (TESS). Spectroscopic follow-up observations obtained with the hermes spectrograph, combined with eclipse-timing variations (ETVs), confirm that the system is comprised of three OB stars, with a compact 1.10 d eclipsing binary and a non-eclipsing tertiary on a 52.04 d orbit. Dynamical modelling of the system (from radial velocity and ETVs) reveal a rare configuration wherein the tertiary star (O9.5-B0.5V; 14–17 M⊙) is more massive than the combined mass of the inner binary (10.9–13.2 M⊙). Given the high mass of the tertiary, we predict that this system will undergo multiple phases of mass transfer in the future, and likely end up as a double neutron star gravitational wave progenitor or an exotic Thorne–Żytkow object. Further observational characterization of this system promises constraints on both formation scenarios of massive stars as well as their exotic evolutionary end-products.

Extreme Eccentricities of Triple Systems: Analytic Results

“…ZLK had been invoked almost ubiquitously as a central agent in the evolution of triple and multiple systems on planetary (e.g., Wu & Murray 2003;Fabrycky & Tremaine 2007;Perets & Naoz 2009;Naoz et al 2011Naoz et al , 2012Hamers et al 2016;Hamers 2017), stellar (e.g., Mazeh & Shaham 1979;Eggleton & Kiseleva-Eggleton 2001;Perets & Fabrycky 2009;Naoz & Fabrycky 2014;Toonen et al 2020;Hamers et al 2021;Toonen et al 2022;Grishin & Perets 2022;Hamers et al 2022), galactic (e.g., Antonini & Perets 2012;Hoang et al 2018;Fragione et al 2019), and extragalactic (e.g., Bonetti et al 2016;Mannerkoski et al 2021) scales. For example, the recent discovery of a massive, compact, and stable stellar triple TIC 470710327 (Eisner et al 2022) serves as a unique laboratory for triple dynamics (Vigna-Gómez et al 2022). ZLK may also provide an important channel for driving compact-object binaries toward merger as gravitational-wave sources (see, e.g., Mandel & Broekgaarden 2022;Mapelli 2021;Mandel & Farmer 2022 for recent reviews).…”

The Visual Survey Group: A Decade of Hunting Exoplanets and Unusual Stellar Events with Space-Based Telescopes

“…In recent years, the VSG has developed a growing interest in hierarchical systems which has resulted in discoveries of triply eclipsing triple systems (Borkovits et al (2019), Borkovits et al (2020), ( 2018)) including a strongly interacting quadruple (Rappaport et al 2017), the nearest known quadruple (Borkovits et al 2021), and the most eccentric, low-mass, short-period, eclipsing binary known (Han et al 2021), which is also part of a quadruple system. Using TESS, the VSG presented the largest catalogue of newly discovered doubly eclipsing quadruple candidates (Kostov et al 2022), and also contributed to the PH-TESS discovery of a massive, compact hierarchical system (Eisner et al 2022). Adding to this collection, are a quintuple system (Rappaport et al 2016) and the first sextuply eclipsing sextuple star system (Powell et al 2021a).…”

Detached Eclipsing Binaries in Compact Hierarchical Triples: Triple-lined systems BD+44 2258 and KIC 06525196

“…Ongoing projects are using triply-eclipsing triples (TET) to characterise CHT (Rappaport et al 2022). Studies even show that CHT can produce exotic Thorne-Żytkow objects (Eisner et al 2022). Last but not the least, CHT have proven to be useful to study ZLK oscillations and their effect on stellar evolution (Borkovits et al 2022).…”