ITC Pizza Lunch


Wednesday, February 21, 2018, 11:00am to 12:00pm



Andrea Dupree

Sleuthing Stellar Winds

Stellar winds and mass loss affect stellar evolution, impact exoplanets and neighboring stars, and influence the stellar environment. Mass outflows and winds from stars are detected in many clever ways from the ground and from space to reveal signatures of acceleration and variability. In some instances, wind sources on the stellar photospheres can be identified. Wind characteristics (and driving mechanisms) change with stellar temperature and luminosity. Estimates of mass loss rates for cool stars from observations and  theory represent an ongoing challenge. 


Kate Alexander

Probing TDE Outflows with Radio Observations

Tidal disruption events (TDEs) in which a star is torn apart by a supermassive black hole (SMBH) offer a unique opportunity to study the physics underlying the formation and growth of relativistic jets and outflows and to discover lower mass SMBHs than with existing techniques (~10^4 - 10^7 solar masses). Radio observations of TDEs allow us to precisely localize the emission (confirming its TDE origin), to determine the properties of outflowing material (energy, size, expansion velocity), and to trace the ambient density profile around previously-dormant SMBHs on otherwise unresolvable scales of ~0.1 - 10 pc. I will present our high-cadence broadband radio studies of TDEs, which have revealed that some TDEs produce powerful relativistic jets, while others produce only lower-energy non-relativistic outflows. With upcoming optical surveys like ZTF promising to greatly increase the TDE discovery rate, modeling the radio emission in relativistic and non-relativistic events and comparing them will help us learn whether conditions such as the peak accretion rate, outflow energy, magnetic field strength, or circumnuclear density are responsible for launching relativistic jets.
See also: Pizza Lunch, 2017-18