Astronomy Tea Talk

Speaker 1: Chase Leland Smith

Title: Spin-Orbit Alignment of Close Binary Stars and the Origin of Slow Rotators

Abstract:

Previous studies of spin-orbit alignment have been limited to small samples, slowly rotating solar-type stars, and/or wide visual binaries that, not surprisingly, manifest random spin-orbit orientations. In this talk, I will present an analysis of Gaia early-type astrometric binaries. My colleagues and I not only find significant spin-orbit alignment, but that the primaries are on average rotating at speeds less than half that of their single-star or wide-binary counterparts. These slowly spinning stars comprise the slow-rotator population in the observed bimodal rotational velocity distribution of early-type stars. I will discuss our proposed formation models of close binaries, where disk angular momentum is transferred to the orbit and/or secondary spin, resulting in a primary with smaller rotational velocity.

Speaker 2: Jason Hinkle

Title: Studying the Interplay between Tidal Disruption Events and Active Galactic Nuclei with Ambiguous and Extreme Nuclear Transients

Abstract:

Over the past decade, surveys have found a significant number of events occurring in the nuclei of galaxies, including tidal disruption events (TDEs) and flaring from active galactic nuclei (AGNs). Recently, an increasing number of nuclear transients have been discovered that exhibit characteristics of both AGNs and TDEs. As such transients cannot easily be classified, we have dubbed them ambiguous nuclear transients (ANTs). Often residing in galaxies hosting an AGN, these ANTs give us a unique window into the diversity of flaring behaviors associated with accretion onto supermassive black holes. ANTs have shown some broad trends, including a strong UV/optical excess, similar to TDEs, and power-law X-ray spectra and significant nuclear dust, similar to AGNs. However, ANTs also exhibit diverse properties, such as a wide range of peak luminosities, photometric evolution, and the appearance and strength of broad emission lines. An overluminous class of extreme nuclear transients (ENTs) has recently been identified, with properties similar to ANTs and likely powered by massive star TDEs. In this talk, I will summarize the current samples of ANTs and ENTs, compare them to TDEs and AGN flares, and discuss important future directions to deepen our physical understanding of these elusive nuclear transients.