Winds of Massive Stars

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Winds of Massive Stars in the Low Metallicity
Environment of the SMC.
Carrie Trundle
Collaborators Danny Lennon, Chris Evans (ING),
Philip Dufton (QUB), Joachim Puls (USM)
Tartu Aug. 2005
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Observational Dataset of SMC B Supergiants

• Subset of 10 supergiants from Lennon (1997)
  EMMI/NTT medium resolution spectra.
• Supplemented by high resolution echelle
• spectra of 7 B supergiants - UVES/VLT (2001).
• Stellar parameters and abundances of these B0-B3
  Ia supergiants were analysed using FASTWIND -
  Trundle et al. 2004, AA,417,217 Trundle
  Lennon 2005, AA, 434, 677

Puls et al. 2005, AA, 435, 669
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Mass-Loss Observations and Theory

• Mass-loss rates of massive stars are important
  constraints for stellar evolution calculations -
  affect stellar masses, rotational velocities and
  element yields.
• we again stress that any comparison between
• observed and predicted rotation for large masses
• is really much more a test bearing on the
  mass-loss rates than a test of the internal
  coupling and evolution of rotation.
• Meynet Maeder
  2005, AA,429, 581

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Wind Momenta SMC Galactic Observations
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Wind Momenta SMC Galactic Observations
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Wind Momenta SMC Galactic Observations

• In MW and SMC, early B supergiants have higher
  wind-momenta than mid Bs.
• The slopes of the linear regression fits to the
  Galactic and SMC objects are different for both
  the Early and Mid (Tefflt 23kK) SMC B
  supergiants. With the SMC being steeper (i.e ?
  lower). As expected from theory (Puls et al.
  2000).
• Over the luminosity range in common between the
  Early Bs in the MW SMC the wind momenta differ
  by 0.6-0.35 dex whilst the Mid Bs differ by 0.9
  to 0.5dex Although there is a large spread at a
  given point in the two datasets.

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Wind Momenta SMC Observations Theory
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Wind Momenta SMC Observations Theory

• Comparing the theoretical predictions of Vink et
  al. 2001 to our observations in the SMC
• Slopes are steeper by theory than observed for
  the early B supergiants whilst they agree well
  for the mid Bs.
• In the Early Bs there is a difference between
  the wind-momenta but better agreement maybe
  obtained by considering clumping.
• Large discrepancy is seen between the observed
  and theoretical wind momenta of Mid B supergiants
  which can only be exasperated by considering
  clumping.
• Theory predicts a jump to higher Mass-loss rates
  for Mid B stars, in comparison to the Early Bs.
  Opposite to observed effect.

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What is next!

• Important to understand the discrepancy between
  observations and theory - the increase of
  mass-loss as predicted by Vink et al. when
  introduced into the evolutionary models causes a
  large decrease in M vrot as the objects move
  from blue to red supergiants.
• Mass loss rates of B type supergiants in the LMC
  FEROS data of 40 B0-B3 Ia supergiants. These
  will hopefully provide a better comparison with
  the smc objects with better constrained distances
  reducing the scatter in the wind-momenta. (In
  collaboration with C. Evans D. Lennon ING, La
  Palma)

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SPECTRA THEORETICAL FITS FROM FASTWIND
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Overview

• Introduce the dataset of SMC B supergiants
• and their mass-loss rates.
• Compare with Galactic B supergiants
• Kudritzki et al. 1999
• Crowther, Lennon Walborn 2005
• Compare with theoretical predictions
• Vink et al. 2000, 2001

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SMC HR- Diagram Log (L?/L?) vs TEFF