The Dynamics of circumbinary Disks and embedded Planets

• Applicant: Dr. Christoph Schäfer, since 3/2022
• Subject Area: Astrophysics and Astronomy
• Term: from 2015 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 285676328

• Final Report Year: 2025

Final Report Abstract

The majority of stars reside in binary star systems. During their formation a sufficiently close binary star system is still surrounded by a circumbinary disc from which there is still material being accreted onto the binary. The orbital motion of the binary transfers angular momentum to the disc and a central inner cavity forms. These cavities have been directly detected in some special systems and the high spatial resolution capabilities of ALMA will allow to investigate more of these sources in even higher detail. A very active recent research topic is the formation and evolution of the circumbinary planets in these discs as observed by the Kepler-mission. Clearly, the structure and dynamics of the circumbinary disc is strongly influenced by the properties of the binary star. In this project we performed new two-dimensional hydrodynamical simulations to elaborate the detailed structure of the disc. In particular the inner regions close to the stars were in the focus at the start of this project. Given the disc physics we performed evolutionary simulations of embedded planets and compare their final configuration with the results of the Kepler mission, in order to understand their formation process. Moreover, we investigated how the interaction of the disc with the binary stars influences the orbital properties of the stars. We compared the results of locally isothermal discs from finite volume simulations, finite difference simulations and SPH simulations. We compared locally isothermal and radiatively cooled disc models to ones with a parametrised cooling timescale (β-cooling), implemented in 2D numerical simulations for varying binary eccentricities. Using observational data, we compared the results of our hydrodynamical models with observations in polarized scattered light of GG Tau A and high angular resolution ALMA observations at 0.87 mm from CS Cha. With our whole set of simulations, it became possible to create parametrized profiles for individual discs to compare to observations and to find limits to their binary eccentricity or internal viscosity from the simulation data, e.g. for HD 142527. The long-term grid simulations allowed us also to study how disc shape and exchange of mass, momentum, and energy between binary and disc depend on the precession angle between disc and binary orbit on time-scales of thousands of binary orbits.

Publications

• 1:1 orbital resonance of circumbinary planets. Astronomy & Astrophysics, 630, L1.
  Penzlin, Anna B. T.; Ataiee, Sareh & Kley, Wilhelm
  
• Circumbinary discs with radiative cooling and embedded planets. Astronomy & Astrophysics, 627, A91.
  Kley, Wilhelm; Thun, Daniel & Penzlin, Anna B. T.
  
• “The dynamics of circumbinary discs and embedded planets”. PhD thesis. Eberhard Karls University of Tubingen, Germany
  D. G. Thun
  
• Gap, shadows, spirals, and streamers: SPHERE observations of binary-disk interactions in GG Tauri A. Astronomy & Astrophysics, 639, A62.
  Keppler, M.; Penzlin, A.; Benisty, M.; van Boekel, R.; Henning, T.; van Holstein, R. G.; Kley, W.; Garufi, A.; Ginski, C.; Brandner, W.; Bertrang, G. H.-M.; Boccaletti, A.; de Boer, J.; Bonavita, M.; Brown Sevilla, S.; Chauvin, G.; Dominik, C.; Janson, M.; Langlois, M. ... & Wildi, F.
  
• Parking planets in circumbinary discs. Astronomy & Astrophysics, 645, A68.
  Penzlin, Anna B. T.; Kley, Wilhelm & Nelson, Richard P.
  
• Binary orbital evolution driven by a circumbinary disc. Astronomy & Astrophysics, 660, A101.
  Penzlin, Anna B. T.; Kley, Wilhelm; Audiffren, Hugo & Schäfer, Christoph M.
  
• How cooling influences circumbinary discs. Astronomy & Astrophysics, 664, A157.
  Sudarshan, Prakruti; Penzlin, Anna B. T.; Ziampras, Alexandros; Kley, Wilhelm & Nelson, Richard P.
  
• The morphology of CS Cha circumbinary disk suggesting the existence of a Saturn-mass planet. Astronomy & Astrophysics, 664, A151.
  Kurtovic, N. T.; Pinilla, P.; Penzlin, Anna B. T.; Benisty, M.; Pérez, L.; Ginski, C.; Isella, A.; Kley, W.; Menard, F.; Pérez, S. & Bayo, A.
  
• “How cooling influences circumbinary disks”. EAS2022, European Astronomical Society Annual Meeting. July 2022, 519, p. 519.
  P. Sudarshan et al.
  
• “Parking planets in circumbinary discs”. EAS2022, European Astronomical Society Annual Meeting. July 2022, 472, p. 472.
  A. B. T. Penzlin, W. Kley & R. Nelson
  
• Stability of coorbital planets around binaries. Astronomy & Astrophysics, 680, A29.
  Adelbert, Stefan; Penzlin, Anna B. T.; Schäfer, Christoph M.; Kley, Wilhelm; Quarles, Billy & Sfair, Rafael
  
• “Circumbinary disks: A transition from stellar binaries to planetary companion.” EAS2023, European Astronomical Society Annual Meeting. July 2023, 2142, p. 2142.
  J. Joseph & A. Penzlin
  
• The Santa Barbara Binary−disk Code Comparison. The Astrophysical Journal, 970(2), 156.
  Duffell, Paul C.; Dittmann, Alexander J.; D.’Orazio, Daniel J.; Franchini, Alessia; Kratter, Kaitlin M.; Penzlin, Anna B. T.; Ragusa, Enrico; Siwek, Magdalena; Tiede, Christopher; Wang, Haiyang; Zrake, Jonathan; Dempsey, Adam M.; Haiman, Zoltan; Lupi, Alessandro; Pirog, Michal & Ryan, Geoffrey
  
• Viscous circumbinary protoplanetary discs – I. Structure of the inner cavity. Monthly Notices of the Royal Astronomical Society, 532(3), 3166-3179.
  Penzlin, Anna B. T.; Booth, Richard A.; Nelson, Richard P.; Schäfer, Christoph M. & Kley, Wilhelm
  
• “How heat can reshape circumbinary discs”. EAS2024, European Astronomical Society Annual Meeting. July 2024, 689, p. 689.
  A. Penzlin & A. Ziampras
  
• Viscous circumbinary protoplanetary discs – II. Disc effects on the binary orbit. Monthly Notices of the Royal Astronomical Society, 537(3), 2422-2432.
  Penzlin, Anna B. T.; Booth, Richard A.; Nelson, Richard P.; Schäfer, Christoph M. & Kley, Wilhelm