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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20210311T103000
DTEND;TZID=Atlantic/Canary:20210311T113000
UID:iactalks-1443
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/1443
CREATED:2021-03-11T10:30:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Hertzsprung-Russell Diagram: from massive Wolf-Rayet stars to strip
 ped helium stars
DESCRIPTION:Hertzsprung-Russell Diagram: from massive Wolf-Rayet stars to s
 tripped helium stars\nDr. Tomer Shenar\n\n"Classical Wolf-Rayet (WR) stars
 " represent a class of hot, hydrogen-depleted stars wtih powerful stellar 
 winds and are prominent progenitors of black holes. Next to their unparall
 eled radiative and mechanical energy feedback, they offer unique probes of
  massive-star evolution at the upper-mass end. To become a classical WR st
 ar, single stars require substantial mass-loss to strip their outer, hydro
 gen-rich layers, implying that only very massive stars could enter the WR 
 phase. However, mass-transfer in binaries can further aid in the stripping
  of stars and form Wolf-Rayet stars, or more generally helium stars, at lo
 wer masses.  Due to the decrease of mass-loss with metallicity, it ha
 s been predicted that WR stars at low metallicity tend to form in binaries
 . However, this has so far not been supported by observations.In my talk, 
 I will give an overview on our current knowledge of the properties of Wolf
 -Rayet populations in the Galaxy and the Magellanic Clouds based on exhaus
 tive spectral analyses. I will illustrate why binary formation does not ne
 cessarily dominate the evolution of WR stars at low metallicity, and highl
 ight important discrepancies between theory and observations of WR stars. 
 I will discuss the observed rarity of intermediate mass helium stars, and 
 present recent reports of unique helium stars in the exotic binaries LB-1 
 and HR 6819.\n 
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