Astronomy Tea Talk

Speaker 1: Steffani Grondin

Title: A New Window into Common Envelope Evolution: The First Catalog of Candidate White Dwarf-Main Sequence Binaries in Open Star Clusters

Abstract:

Close compact object binaries are the precursors to Type Ia supernovae and gravitational wave events. While most short-period binaries are believed to have evolved through at least one common envelope (CE) phase, our understanding of CE evolution remains one of the largest unresolved issues in stellar astrophysics, mainly due to the lack of observational benchmarks that connect post-CE parameters with their pre-CE initial conditions. Identifying post-CE systems in star clusters can circumvent this issue by providing an independent constraint on the system's age, but until recently, there were only two white dwarf-main sequence (WD+MS) post-CE systems associated with a star cluster. In this talk, I will describe our discovery of the first population of candidate WD+MS binaries in Milky Way star clusters. First, I will discuss our new catalog of 52 WD+MS candidate binaries in 38 open star clusters identified through multi-wavelength observations and supervised machine learning. Next, I will detail the ongoing follow-up characterization of a subset of systems that has led to the confirmation of new WD+MS post-CE systems in clusters. Finally, I will outline how we can expand this sample by using novel star cluster simulations to link field binaries with their birth clusters. These efforts will ultimately provide fundamental observational constraints on one of the most uncertain yet crucial phases of binary evolution.

Speaker 2: Asia Piotrowska-Karpov

Title: Constraining Black Hole Growth History With Population Spin Measurements

Abstract:

Constraining the primary growth channel of supermassive black holes (SMBH) remains one the most actively debated questions in the context of cosmological structure formation. Owing to the connection between SMBH spin parameter evolution and accretion-/merger-dominated black hole growth, population spin measurements offer a rare observational window into SMBH cosmic assembly history. I will discuss the mass-spin plane of local SMBH as a probe of cosmological black hole growth in the context of state-of-the-art cosmological hydrodynamical simulations and statistical constraints placed by most recent compilations of spin parameter measurements published in the literature.