Eclipse of the V773 Tau B circumbinary disc

Abstract

Context. Young multiple stellar systems can host both circumstellar and circumbinary disks composed of gas and dust, and the orientations of circumbinary disks can be sculpted by the orientation and eccentricity of the central binaries. Studying multiple binary systems and their associated disks enables understanding of the size and distribution of the planetary systems that subsequently form around them. Aims. A deep (∼ 70%) and extended (∼150 days) eclipse was seen towards the young multiple stellar system V773 Tau in 2010. We interpret it as due to the passage of a circumbinary disk around the B components moving in front of the A components. Our aim is to characterise the orientation and structure of the disk, to refine the orbits of the subcomponents, and to predict when the next eclipse will occur. Methods. We combine the photometry from several ground based surveys, construct a model for the light curve of the eclipse, and use high angular resolution imaging to refine the orbits of the three components of the system, A, B and C. Frequency analysis of the light curves, including from the TESS satellite, enables characterisation of the rotational periods of the Aa and Ab stars.Results. A toy model of the circumbinary disk shows that it extends out to approximately 5 au around the B binary and has an inclination of 73 • with respect to the orbital plane of AB, where the lower bound of the radius of the disk is constrained by the geometry of the AB orbit and the upper bound is set by the stability of the disk. We identify several frequencies in the photometric data that we attribute to rotational modulation of the Aa and Ab stellar companions. We produce the first determination of the orbit of the more distant C component around the AB system and limit its inclination to 93 • . Conclusions. The high inclination and large diameter of the disk, together with the match from theory suggest that B is an almost equal mass, moderately eccentric binary. We identify the rotational periods of the Aa and Ab stars, identify a third frequency in the light curve that we attribute to the orbital period of the stars in the B binary. We predict that the next eclipse will be around 2037, during which both detailed photometric and spectroscopic monitoring will characterise the disk in greater detail.

Misaligned Circumbinary Disks as Efficient Progenitors of Interstellar Asteroids

“…Depending on the binary and disk parameters, the alignment timescale can be longer than the disk lifetime, and so the planetesimal disk may form in a misaligned disk. We note that the two currently observed polar circumbinary gas disks have external companions (Kennedy et al 2019;Kenworthy et al 2022) that truncate the outer part of the circumbinary disk, leading to a radially narrow disk and a short alignment timescale (Martin et al 2022). The timescale for gas disk alignment also depends upon a number of other binary and disk parameters including the binary semimajor axis, binary eccentricity, disk viscosity, and disk temperature (e.g., .…”

“…Circumbinary gas disks (CBDs) with large misalignments relative to the binary orbital plane are commonly observed in nature (e.g., Chiang & Murray-Clay 2004;Köhler 2011;Andrews et al 2014;Brinch et al 2016;Takakuwa et al 2017;Fang et al 2019;Kennedy et al 2019;Kenworthy et al 2022;Zhu et al 2022). The degree of CBD misalignment often increases with binary separation and eccentricity (Czekala et al 2019).…”

Polar Circumtriple Planets and Disks Can Only Form Close to a Triple Star

“…Dissipation in the disk leads to alignment either toward coplanar (Facchini et al 2013;Nixon et al 2013) or polar, depending on the initial tilt (Martin & Lubow 2017;Zanazzi & Lai 2018;Cuello & Giuppone 2019). Several polar circumbinary disks around eccentric binaries have been observed (Kennedy et al 2012(Kennedy et al , 2019Kenworthy et al 2022) although none have yet been observed around a triple star. While polar circumbinary planets have not yet been observed, their formation may be as efficient as in a coplanar configuration (Childs & Martin 2021a, 2021b.…”

Coplanar Circumbinary Planets Can Be Unstable to Large Tilt Oscillations in the Presence of an Inner Polar Planet

“…Based on considerations of disk evolution, if it is sufficiently fast, then we expect planets to be either coplanar or polar with respect to the binary orbit (e.g., Martin & Lubow 2017). While polar planets have not yet been found, there are several examples of polar disks (Kennedy et al 2012(Kennedy et al , 2019Kenworthy et al 2022).…”