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UID:UW-Physics-Event-5167
DTSTART:20190912T203000Z
DTEND:20190912T220000Z
DTSTAMP:20260415T061057Z
LAST-MODIFIED:20190904T164147Z
LOCATION:4421 Sterling Hall\, Coffee and cookies 3:30 PM\, Talk begins
  3:45 PM
SUMMARY:The Yin and Yan of Slowly-Pulasting B Stars: Asteroseismology 
 and Angular Momentum Redistribution\, Astronomy Colloquium\, Professor
  Richard Townsend\, UW Madison Astronomy Department
DESCRIPTION:During their main-sequence evolution\, almost all B-type s
 tars will
\npass through a phase where they are unstable toward oscill
 ation in one or more global internal gravity waves ('g modes'). The g 
 modes\, driven by iron and nickel opacity in the stars' outer envelope
 s\, generate surface temperature and velocity changes with periodiciti
 es on the order of days.<br>
\n<br>
\nIn the 'Yin' part of my talk\, I
 'll discuss how time-series
\nspectroscopy and photometry of these `sl
 owly-pulsating B' (SPB) stars can be leveraged into asteroseismology -
 -- probing the stars'interiors by careful analysis of their oscillatio
 n spectra. I'll highlight in particular how the Kepler mission\, toget
 her with the MESA stellar evolution code and my GYRE stellar oscillati
 on code\, has allowed novel constraints to be established on the inter
 nal rotation and mixing physics of SPB stars.<br>
\n<br>
\nI'll then p
 ivot to the 'Yang' part of my talk. Although we typically regard stell
 ar oscillations as passive tracers of stellar structure\, they can als
 o modify this structure. I'll present recent work with Jacqueline Gold
 stein and Ellen Zweibel\, exploring angular momentum redistribution by
  g modes. Modeling this process in SPB stars\, we find that significan
 t modification of internal rotation profiles can occur on timescales a
 s short as centuries. This suggests that the g modes can impact the st
 ars' life trajectories\, a possibility that's been hitherto ignored in
  stellar evolution calculations.
URL:https://www.physics.wisc.edu/events/?id=5167
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