ITC Colloquium - Jennifer Andrews (Arizona) and Diana Powell (UCSC)


Thursday, October 22, 2020, 11:00am to 12:00pm


  1. Jennifer Andrews (Arizona)  "Supernova Imposters and the Eruptions of Massive Stars"

    Existing in the magnitude space between traditional supernovae (SNe) and classical novae lies a zoo of explosive and eruptive transients with maximum absolute magnitudes of roughly -10<MV<-15. Traditionally interpreted as giant luminous blue variable (LBV) eruptions these often dubbed “SN imposters” likely arise from a variety of initial stellar masses and are caused by physical mechanisms ranging from instabilities in nuclear burning as the object evolves off the main sequence to stellar mergers in binary star systems. Moreover, some individual LBV giant eruptions, including the prototypical case of Eta Car, have been proposed as massive-star merger events. All of these involve large amounts of episodic mass loss, and many of them share observed properties that blur the distinction between categories. While their eruptions mimic those of SNe, these transients appear to all be non-terminal, leaving some form of the progenitor behind after eruption. I will discuss this class of non-terminal transients, including the Great Eruption of the enigmatic Eta Car and a uniquely puzzling SN imposter in M74.
  2. Diana Powell (UCSC) ""Protoplanetary Disks and Clouds in Substellar Atmospheres: Insights from Microphysics"

    In this talk, I will provide evidence that protoplanetary disks are more than an order of magnitude more massive than previously appreciated, that the detailed properties of clouds shape observations of substellar atmospheres, and that the physics of modeling clouds gives a new understanding of the solid content in protoplanetary disks. Clouds on extrasolar worlds are seemingly abundant and interfere with observations; however, little is known about their properties. In our modeling, we predict cloud properties from first principles and investigate how the interesting observational properties of hot Jupiters and brown dwarfs can be explained by clouds. Next, I will report on a new set of models that reconcile theory with observations of protoplanetary disks and create a new set of initial conditions for planet formation models. The total mass available in protoplanetary disks is a critical initial condition for understanding planet formation, however, the surface densities of protoplanetary disks still remain largely unconstrained due to uncertainties in the dust-to-gas ratio and CO abundance. I make use of recent resolved multiwavelength observations of disks in the millimeter to constrain the aerodynamic properties of dust grains to infer the total disk mass without an assumed dust opacity or tracer-to-H2 ratio. Finally, I will present new work that combines the microphysics of cloud formation in planetary atmospheres and our new models of protoplanetary disks to show that the observed depletion of CO in well-studied disks is consistent with freeze-out processes and that the variable CO depletion observed in disks can be explained by the processes of freeze-out and particle drift. 

See also: Colloquium, 2020-21