Description:

Monday Observational Meetings for Northwestern University's Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), this week featuring:

Abigail Polin (UC Berkeley)

Title: Modeling Sub-Chandrasekhar Mass White Dwarf Explosions as Type Ia Supernovae

Abstract: Type Ia supernovae are some of the most common cosmic transients, yet their progenitors are still not known. I will discuss my thesis research on a specific pathway to these explosions, known as the double detonation scenario.  I will first describe the hydrodynamic techniques I use to simulate these explosions and to calculate the composition of the outflow.  I will also describe the radiation transport methods I use to translate the hydrodynamical output into synthetic light curves and spectra.  Using these methods, I have calculated some distinct observational signatures that should be exhibited by any double detonation explosion in both the photospheric and nebular phase.  I will discuss the populations of SNe Type Ia which are consistent with these features. Lastly, I will present the first observed supernova, SN2018byg, that exhibits some "smoking gun" signatures I predicted, and which therefore strongly supports the idea that some Ia's are triggered by double detonations.

Host: Raffaella Margutti

Jane Huang (Harvard)

Title: The ALMA View of Planet Formation

Abstract: The ubiquity and diversity of exoplanets tell us that planets can emerge under an astonishing range of conditions. Observations of protoplanetary disks yield insights into how the masses, compositions, and orbital architectures of planets are influenced by their natal environments. While protoplanets are difficult to image directly, the advent of high-resolution, high-sensitivity telescope facilities such as ALMA has now made it possible to search systematically for disk structures potentially induced by planet-disk interactions and to use their morphologies to infer characteristics of the young planet population. We recently undertook the first high angular resolution ALMA survey of protoplanetary disks, the Disk Substructures at High Angular Resolution Project (DSHARP). Concentric rings and gaps are the most common type of substructure observed in dust continuum emission and are found in disks spanning a large range of ages and stellar host spectral types. The widespread presence of these structures suggests that giant planet formation may occur readily within a million years throughout much of the extent of the disk. Spiral arms are seen in a minority of disks and may arise either because of perturbations from an unseen wide-orbit companion or from gravitational instabilities. Finally, I will discuss case studies of how ring and spiral structures in molecular line emission provide a different window into the planet formation process by tracing vigorous chemical evolution in the disk and dynamical processes beyond the extent of the observed dust emission. 

Host: Kate Alexander (TBC)