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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20181213T110000
DTEND;TZID=Atlantic/Canary:20181213T120000
UID:iactalks-1225
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/1225
CREATED:2018-12-13T11:00:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Nebulae around evolved massive stars
DESCRIPTION:Nebulae around evolved massive stars\nOlga Maryeva\n\n\n\nMassi
 ve stars (with masses higher than 30 M⊙) undergo the mass loss during th
 eir whole lifes. During hydrogen burning in their cores massive stars demo
 nstrate fast winds with velocity about V∞=2500 km/s and relatively l
 ow mass-loss rate about 10 -7-10-6 M⊙/year. At the same time, after the 
 end of core hydrogen burning stars become less stable and mass-loss rate i
 ncreases, stars move to the stage of Luminous Blue variable (LBV). LBVs ar
 e relatively short evolutionary stage in life of massive stars, during whi
 ch they lose significant amount of mass through strong stellar winds and o
 ccasional giant eruptive events. As a result, they shed their outer layers
  and eventually become hydrogen-deficient Wolf–Rayet stars. Massive 
 stars with 25-40 M⊙ reach LBV stage after being red supergiants i.e. rea
 ching cool end on Hertzsprung– Russell diagram, more massive stars b
 ecame LBV right after blue supergiants phase. Consideration of the initial
  mass function leads to conclusion that LBV stars are extremely rare and t
 here should be no more than a few dozens such objects in the Galaxy. Detec
 tion of LBV- like shells may be considered an indication of that their ass
 ociated stars are massive and evolved. Searches for such shells using the 
 infrared surveys resulted in the discovery of many dozens of such shells, 
 while follow-up spectroscopy of their central stars led to the discovery o
 f dozens of new candidates to LBVs. In the talk I will tell about properti
 es of nebula around post-LBV star GR290 and about estimated parameters of 
 couple of stars with LBV-like shells, and discuss that at least in some ca
 ses the envelope loss occurs before LBV stage. \n\n
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