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The Formation of Binary Stars and Planets

The majority of solar-type stars are born in binaries, and therefore star and planet formation must be examined in the context of stellar multiples. I will first highlight the hurdles in standard migration models of close binaries and hot Jupiters.  Although the majority of close binaries have outer tertiary companions, which initially indicated that secular evolution hardened the inner binary on Gyr timescales, recent observations of T Tauri stars demonstrate that most close binaries migrated within a few Myr.  I will overview a new population synthesis model that incorporates more realistic initial conditions and dynamical tides, which efficiently hardens close binaries and hot Jupiters on rapid timescales. Second, there is accumulating observational evidence that young binary companions within a < 100 AU substantially suppress planet formation. I will demonstrate that 40% of solar-type stars do not host close planets due to suppression by close binaries, which accounts for the discrepancy in planet occurrence rates and trends inferred from radial velocity versus transit techniques. Finally, I will discuss the role of metallicity in forming binary stars and planets. In particular, the close binary fraction of solar-type stars decreases significantly with metallicity, which partially explains why Jovian planets prefer metal-rich hosts, contrary to canonical planet formation theories.

Cody Hall, AB 107

Maxwell Moe, University of Arizona

February 26, 2020
3:00 pm - 4:00 pm