Speaker
Description
Abstract: Metallicity correlations and other observed statistics indicate that disc fragmentation due to Gravitational Instability (GI) is the likely origin of massive companions to stars, such as giant planets orbiting M-dwarf stars, Brown Dwarf (BD) companions to FGK stars, and binary stars with separations smaller than about 100 au. In paper I of this series, we showed that disc fragmentation in young rapidly evolving binary systems inevitably ejects an abundant population of massive Jupiter-mass free-floating planets (FFPs). In this model, a massive disc around an initially single protostar fragments on a number of clumps, and the secondary star is an oligarch fragment that grows particularly massive. As the system rearranges itself from a singe to a binary star configuration, a dramatic "pincer movement" by the binary ejects planets through dynamical interactions with the stars. Here we propose that the same scenario applies to an even more abundant population of smaller FFPs discovered by the microlensing surveys. Although disc fragmentation is usually believed to form only massive objects, three different pathways [1,2,3] for forming small core-dominated planets exist. We present results from three complementary simulation approaches (3D SPH, 2D FARGO-ADSG, and N-body REBOUND), all of which indicate planet ejection efficiency greater than 50%. We discuss observational implications of this scenario. FFP observations may be the most convincing evidence yet that disc fragmentation forms not only giant planets, BD, and stellar companions, but also low mass (M<< 1 Jupiter mass) planets, and that planets are made well before the binary matures. Future FFP observations may be decisive in constraining the physics of GI planet and binary formation scenarios.
[1]: Gibbons,P. +14, https://ui.adsabs.harvard.edu/abs/2014MNRAS.442..361G/abstract
Longarini, C. +23, https://ui.adsabs.harvard.edu/abs/2023MNRAS.522.6217L/abstract
[2] Boley, A +10, https://ui.adsabs.harvard.edu/abs/2010Icar..207..509B/abstract
Nayakshin, S 2017, https://ui.adsabs.harvard.edu/abs/2017PASA...34....2N/abstract
[3] Deng, H. +21, https://ui.adsabs.harvard.edu/abs/2021NatAs...5..440D/abstract
Kubli, N. +23, https://ui.adsabs.harvard.edu/abs/2023MNRAS.525.2731K/abstract
- List of collaborators: Aleksandra Calovic, Luyao Zhang, Hans Lee, Clement Baruteau, Sarah Casewell, Nuria Miret-Roig, Farzana Meru, Lucio Mayer.
