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08/29/19: SO/NOAO Joint Colloquium Series: Cristobal Petrovich, Steward Observ.


Title: Shortest-period Planets and Merging Black Holes: A Chaotic History

Several populations of planets and binary systems are most readily detected in extremely tight orbits. Such orbits are not natural outcomes of traditional formation processes and provide with an opportunity to understand relevant steps in the assembly of planetary and stellar systems. In this talk, I will describe two of these populations and argue that long-term dynamical chaos has played a major role in their formation.

First, I will describe the puzzling population of ultra-short-period planets---rocky planets in orbits interior to ~1 day. I will argue that secular chaos, the same process shaping Mercury’s (possibly fatal) orbit, has driven their migration into their tight orbits. I will show how this model fits within the Kepler data and discuss the upcoming research opportunities from TESS.

Second, I will discuss the population of binary black holes that have been detected by LIGO/Virgo, where a major question in the field is how and where these black holes merge. I will show a new and promising channel in which black holes merge dynamically in the centers of galaxies due to dynamical chaos triggered by the host star cluster’s tidal field. I will discuss the predictions of this model for the effective spins of black holes as well as the observed overdensity of X-ray binaries in the central parsec.

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