Astronomy Seminar: New Advances in the Mass-Loss Rates of Massive Stars with Implications for Massive Star Evolution
| Date/Time: | Friday, 09 Nov 2018 from 4:20 pm to 5:20 pm |
|---|---|
| Location: | Rm. 38, Physics Bldg. |
| Cost: | Free |
| Contact: | Curt Struck |
| Phone: | 515-294-5440 |
| Channel: | College of Liberal Arts and Sciences |
| Actions: | Download iCal/vCal | Email Reminder |
Second only to the initial stellar mass (or interaction with a close
companion), the rate of wind-driven mass loss determines the final mass
of a massive star and the nature of its remnant. Longstanding
discrepancies between various observational measurement techniques and
theoretical expectations have motivated a new observational
approach. The principle of momentum flux balance between a stellar
wind and the impinging flow of the interstellar medium in the rest frame
of a moving star leads to a previously unexploited measurement
technique. Mass-loss rates for O and early-B stars agree well with
recent theoretical predictions, ranging from 10^-6 solar masses per year
for mid-O dwarfs to few times 10^-8 solar masses per year for late-O
dwarfs, with an order of magnitude dispersion at any given spectral
type and luminosity class. Evolved stars show elevated mass-loss rates
compared to dwarfs, consistent with model expectations. Our results
provide the first observational mass-loss rates for B0-B2 dwarfs -
10^-7 to 10^-9 solar masses per year - significantly higher than
theoretical expectations. B stars with effective temperatures <25,000 K
lie consistently above predictions. We interpret this as the first
empirical evidence for an increase in the mass-loss rates below a
critical temperature, consistent with predictions of a discontinuous
increase in stellar opacity and mass-loss among early B stars.