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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-2632
DTSTART:20120329T203000Z
DTEND:20120329T220000Z
DTSTAMP:20260314T194530Z
LAST-MODIFIED:20120322T180825Z
LOCATION:4421 Sterling Hall
SUMMARY:X-ray Spectroscopy of Massive Stars: Constraints on Stellar Wi
 nd Mass-Loss Rates\, Clumping\, and Shock Physics\, Astronomy Colloqui
 um\, David Cohen\, Swarthmore College
DESCRIPTION:Hot\, luminous\, massive stars are strong sources of soft 
 X-ray emission\, despite their general lack of surface magnetic fields
  and the associated dynamo activity and MHD processes that heat a coro
 na and explain the X-ray emission of solar-type stars. Since massive s
 tars' surprising discovery as X-ray sources in the late 1970s\, a cons
 ensus has emerged that the X-rays are produced in their strong radiati
 on-driven winds. I will show how high-resolution X-ray spectroscopy ca
 rried out over the past decade with the Chandra and XMM-Newton satelli
 te observatories has confirmed the basic wind-shock scenario of X-ray 
 production in massive stars and enabled the testing of theoretical mod
 els by providing quantitative constraints on the temperature\, spatial
  distribution\, and kinematics of the X-ray emitting plasma embedded i
 n the stellar wind. I will also discuss how absorption signatures in t
 he X-ray spectra can be used to measure the mass-loss rates of these w
 inds\, and present some initial results that indicate lower mass-loss 
 rates than have been traditionally assumed. When combined with observa
 tions in the optical and radio\, these X-ray absorption measurements a
 lso provide information about the clumping properties of massive star 
 winds.
URL:https://www.physics.wisc.edu/events/?id=2632
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