Northwestern Events Calendar

Apr
26
2022

Astro Seminar: Diego Muñoz: A Revised Paradigm of Binary-Disk Interaction

When: Tuesday, April 26, 2022
4:00 PM - 5:00 PM CT

Where: 1800 Sherman Avenue, Room 7-600, Evanston, IL 60201 map it

Audience: Faculty/Staff - Student - Post Docs/Docs - Graduate Students

Contact: Samantha Westlake  

Group: Physics and Astronomy Astrophysics Seminars

Category: Academic

Description:

Abstract: In the last five years, we have witnessed a renewed interest in the classical problem of binary-disk interaction, which focuses on the tidal coupling between a central (accreting) binary and the surrounding accretion disk.  In addition to binary growth, this process dictates the evolution of the binary’s orbital elements. Being a ubiquitous scenario, binary-disk interaction plays a pivotal role in a wide range of astrophysical contexts, such as  the formation and migration of stellar binaries, or the interaction between super-massive black hole (SMBH) pairs in gaseous environments, like in post-galactic merger remnants. But despite the critical importance of understanding binary-disk interaction, and despite the monumental advances in computational models of accretion disks, some of the most basic aspects of this decades-old problem remain unclear. In particular, a  ``dogma’’ of binary-disk interaction has been recently challenged: binaries might expand (or ``soften’’) due to their coupling to the gas rather than contract (or ``harden’’), as it was assumed to be the case for the last three decades. This finding alone can have important repercussions for our understanding of binary star formation and SMBH growth via mergers.  Indeed, gas-driven outward migration may severely modify the expected rate at which SMBH binaries coalesce and merge on cosmological scales. Understanding this effect is thus of crucial importance for current and future missions of low-frequency gravitational wave astronomy, such as the Pulsar Timing Array and LISA. In this talk, I will go over this new  ‘outward migration’ conundrum of binary-disk interaction and other ``dogmas’’ that could use a second look.  I will explain why we missed this unexpected effect for 30 years, and discuss what combination of physical ingredients could still make binaries migrate inward.

Speaker: Diego Muñoz, Research Assistant Professor, Northwestern University 

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