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Young binary systems offer a unique opportunity to study the fragility of circumstellar disks in dynamically tumultuous environments. In this talk, I will present preliminary ALMA continuum and 12CO emission for several systems, including the puzzling DF Tau. DF Tau is a close visual binary with a semi-major axis of only 14 AU; we find circumstellar disks around both the primary and secondary star. Other disk signatures, i.e. accretion measurements and H-band veiling, indicate only a disk around the primary star. Because the two stars likely formed together, with the same composition, in the same environment, and at the same time, we expect their disks to be co-eval. However the absence of an inner disk around the secondary suggests uneven dissipation. We resolve this contradiction by proposing that the inner disk of DF Tau B is, at minimum, beyond ~0.06 AU and consider several processes which have the potential to accelerate inner disk evolution. 

Abstract This article presents the latest results of our Atacama Large Millimeter/submillimeter Array (ALMA) program to study circumstellar disk characteristics as a function of orbital and stellar properties in a sample of young binary star systems known to host at least one disk. Optical and infrared observations of the eccentric, ∼48 yr period binary DF Tau indicated the presence of only one disk around the brighter component. However, our 1.3 mm ALMA thermal continuum maps show two nearly equal-brightness components in this system. We present these observations within the context of updated stellar and orbital properties, which indicate that the inner disk of the secondary is absent. Because the two stars likely formed together, with the same composition, in the same environment, and at the same time, we expect their disks to be co-eval. However the absence of an inner disk around the secondary suggests uneven dissipation. We consider several processes that have the potential to accelerate inner disk evolution. Rapid inner disk dissipation has important implications for planet formation, particularly in the terrestrial-planet-forming region. 

Abstract Close binary systems present challenges to planet formation. As binary separations decrease, so do the occurrence rates of protoplanetary disks in young systems and planets in mature systems. For systems that do retain disks, their disk masses and sizes are altered by the presence of the binary companion. Through the study of protoplanetary disks in binary systems with known orbital parameters, we seek to determine the properties that promote disk retention and therefore planet formation. In this work, we characterize the young binary−disk system FO Tau. We determine the first full orbital solution for the system, finding masses of ${0.35}_{-0.05}^{+0.06}{M}_{\odot }$and 0.34 ± 0.05M_⊙for the stellar components, a semimajor axis of $22{(}_{-1}^{+2})$au, and an eccentricity of $0.21{(}_{-0.03}^{+0.04})$. With long-baseline Atacama Large Millimeter/submillimeter Array interferometry, we detect 1.3 mm continuum and¹²CO (J= 2–1) line emission toward each of the binary components; no circumbinary emission is detected. The protoplanetary disks are compact, consistent with being truncated by the binary orbit. The dust disks are unresolved in the image plane, and the more extended gas disks are only marginally resolved. Fitting the continuum and CO visibilities, we determine the inclination of each disk, finding evidence for alignment of the disk and binary orbital planes. This study is the first of its kind linking the properties of circumstellar protoplanetary disks to a precisely known binary orbit. In the case of FO Tau, we find a dynamically placid environment (coplanar, low eccentricity), which may foster its potential for planet formation. 

The majority of Sun-like stars form with binary companions, and their dynamical impact profoundly shapes the formation and survival of their planetary systems. Demographic studies have shown that close binaries (a < 100 au) have suppressed planet-occurrence rates compared to single stars, yet a substantial minority of planets do form and survive at all binary separations. To identify the conditions that foster planet formation in binary systems, we have obtained high-angular-resolution, mm interferometry for a sample of disk-bearing binary systems with known orbital solutions. In this poster, we present the case study of a young binary system, FO Tau (a ~ 22 au). Our ALMA observations resolve dust continuum (1.3 mm) and gas (CO J=2-1) from each circumstellar disk allowing us to trace the dynamical interaction between the binary orbit and the planet-forming reservoir. With these data we determine individual disk orientations and masses, while placing these measurements in the context of a new binary orbital solution. Our findings suggest that the FO Tau system is relatively placid, with observations consistent with alignment between the disks and the binary orbital plane. We compare these findings to models of binary formation and evolution, and their predictions for disk retention and planet formation.