Protoplanetary Disk Dynamics
Circumstellar Disks with Binary Companions
Given that ~50% of FGK stars have binary companions (e.g. Raghavan+ 2010), and up to ~80% of young binaries host protoplanetary disks (e.g. Kraus+ 2012), planet formation frequently occurs in binary star systems. The bulk of my PhD research worked to understand their dynamics. Over long timescales, I found viscous dissipation from the disk drives the disk into alignment with the binary, and the star into alignment with the disk. However, the binary's torque can sometimes misalign the host star's spin axis with the disk's orbital angular momentum axis, forming planets with orbital planes misaligned with the host star's equatorial plane. I showed this is the most likely explanation for the large stellar obliquities in some exoplanetary systems, such as K2 290. Sometimes, a close and inclined binary companion can not only tilt the disk, but also make it very eccentric through the Lidov-Kozai effect.
My collaborators and I are still working to understand if viscous dissipation within disks can explain the observed alignment of planetary systems with binary companions, and if disk precession driven by the binary can explain the stellar obliquities of exoplanetary systems.
Inclined Circumbinary Disks
Few gaseous and debris disks orbiting binary stars that had large inclinations between the disk and binary's orbital planes, which tended to orbit eccentric binaries. During my PhD, I showed gravitational torques from the eccentric binary and viscous torques from disk warping can drive the disk-binary inclination to 90 degrees (polar alignment). After publication, more highly inclined circumbinary disks (such as GW Ori and HD 98800) were detected orbiting eccentric binaries, confirming my predictions.
The undergraduate Michael Poon (undergraduate CPS and SURP fellow at the University of Toronto) and I analyzed the KH 15D light-curve, which consists of an inner binary orbited by a warped protoplanetary disk which eclipses the binary as it precesses. Combining photometry and radial velocity data with a dynamical model, we constrained the disk's annular extent, tilt, and precession period.
Right image credit: Michael Poon
Planets Embedded in Transition Disks
Multiple planetary systems with large mutual inclinations have been observed, and shadows reveal inclined inner disks hiding within transition disk cavities. Recently, I showed planets forming in a transition disk cavity can undergo a nodal secular resonance can excite the inner planet's inclination, explaining the large misalignments observed in some planetary systems. This same mechanism can also tilt an inner disk, if a transition disk's cavity harbors a massive planet. I also made testable predictions for the masses of putative planets hiding within a disk cavity, testable with high-constrast imaging.
Publications
Gerbig K., Rice M., Zanazzi J. J., Christian S., Vanderburg A.; Aligning Planet-hosting Binaries via Dissipative Precession in Circumstellar Disks. 2024, ApJ, 972, 161. PDF
Knudstrup E., Albrecht S., Winn J., Gandolfi D., Zanazzi J. J., et al.; Obliquities of Exoplanet Host Stars: 19 New and Updated Measurements, and Trends in the Sample of 205 Measurements. 2024, accepted to A&A, PDF
Tofflemire B., Prato L., Kraus A., Segura-Cox D., Schaefer G., Akeson R., Andrews S., Jensen E., Johns-Krull C., Zanazzi J. J., Simon M.; Sites of Planet Formation in Binary Systems. I. Evidence for Disk‑Orbit Alignment in the Close Binary FO Tau. 2024, AJ, 167, 232. PDF
J. J. Zanazzi & Eugene Chiang; Sweeping Secular Resonances and Giant Planet Inclinations in Transition Discs. 2024, MNRAS, 527, 7203. PDF
Dullemond C., Kimmig C., Zanazzi J. J.; On the equations of warped disc dynamics. 2022, MNRAS, 511, 2925. PDF
Zhu W., Bernhard K., Dai F., Fang M., Zanazzi J. J., et al.; Two Candidate KH 15D-like Systems from the Zwicky Transient Facility. 2022, ApJL, 933, L21. PDF
Hjorth M., Albrecht S., Hirano T., Winn J. N., Dawson R. I., Zanazzi J. J., et al.; A backward-spinning star with two coplanar planets. 2021, PNAS, 118, 2017418118. PDF
Michael Poon, J. J. Zanazzi, & Wei Zhu; Constraining the Circumbinary Disk Tilt in the KH 15D system. 2021, MNRAS, 503, 1599. PDF
J. J. Zanazzi & Dong Lai; Planet Formation in Disks with Inclined Binary Companions: Can Primordial Spin-Orbit Misalignment be Produced? 2018, MNRAS, 478, 835. PDF
J. J. Zanazzi & Dong Lai; Effect of Disk Warp in Star-Disk-Binary Systems. 2018, MNRAS, 477, 5207. PDF
J. J. Zanazzi & Dong Lai; Inclination Evolution of Protoplanetary Disks around Eccentric Binaries. 2018, MNRAS, 473, 603. PDF
J. J. Zanazzi & Dong Lai; The Lidov-Kozai Effect in Hydrodynamical Disks: Linear Stability Analysis. 2017, MNRAS, 467 (2): 1957-1964. PDF