Session R09: LeRoy Apker Award Session

LeRoy Apker Award: Protoplanet Population Properties: a new method to compute survey sensitivity

Studying still-forming protoplanets is an effective method to probe planet formation and evolution mechanisms. Direct imaging, in particular, constrains a protoplanet’s mass, mass accretion rate, and orbital properties, key attributes that enable distinguishing between models of planet growth. The recent development of and successes in dedicated protoplanet surveys allow us to study them as a population for the first time. Establishing limits on protoplanet abundance and the relative importance of different formation pathways are now within reach. Inferring population properties requires quantifying survey detection limits and selection effects (e.g., Malmquist bias). In the planet case, we ask: what is the probability of planet detection as a function of its physical properties (e.g., mass, semimajor axis)? While the procedure for computing sensitivity to fully-formed planets is well-established, no analogous methods have yet been constructed for protoplanets. In particular, computing survey sensitivity requires translating physical properties into observable characteristics. For protoplanets, this mapping is complicated by uncertainties in planetary accretion physics. In this work, we develop a novel method to compute survey sensitivity to accreting protoplanets. We apply our technique to the results of the Magellan Giant Accreting Protoplanet Survey to put the first statistical constraints on protoplanet frequency. Our method is flexible to evolutionary and accretion physics assumptions, and we compare six possible combinations of models. Across accretion models and statistical formalisms, we find a median posterior probability of 30-40% for transitional disk stars to host a protoplanet ~ 1-10 M_J within 2200 mas. Our method for population analyses of protoplanets comes at an opportune time: upcoming surveys will more than triple the sample size, decreasing uncertainty and bringing us closer to understanding the mechanisms by which planets form.   

Devoured Worlds: The Observational Signatures of Planetary Engulfment Events

TBA   

Modeling Planetary Engulfment

In many planetary systems, dynamical processes and stellar evolution will lead to the engulfment of planets by their host stars. Multiple observations suggest that planetary engulfment plays a significant role in the evolution of planetary systems, including (i) stars with abnormal rotational and/or chemical properties, and (ii) the large number of planets at orbital separations such that their star will engulf them when it becomes a giant. A companion talk will discuss the observational signatures of planetary engulfment in detail.

In this talk, I will review models of planetary engulfment. I will also discuss the physical interpretation of ZTF SLRN-2020, an observed transient from a star engulfing a planet. Finally, I will discuss promising future models of planetary engulfment, with an emphasis on predicting its observational signatures and understanding its impact on stellar and planetary system evolution.