Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998arep...42...52l&link_type=abstract
Astronomy Reports, volume 42, page 52 (1998).
Astronomy and Astrophysics
Astronomy
8
Scientific paper
An analysis of the latest data for close binary systems consisting of O and early B stars shows that during the first half of the lifetime on the main sequence, the components of such systems retain the initial helium abundance He/H = 0.08-0.09 in their atmospheres. Subsequently, He/H abruptly increases approximately twofold in a short interval of relative ages t/t_MS between 0.5 and 0.7, and this enhanced He/H remains constant until the main-sequence stage is complete. Single O stars exhibit a similar nonmonotonic dependence of He/H on t/t_MS with a discontinuity at t/t_MS ~ 0.6. A preliminary analysis performed for single early B stars leads us to conclude that in this case He/H may also increase steeply at t/tMS 0.6. The data available for early B stars reveal no correlation of He/H with the observed projected rotational velocity vsini and with the equatorial rotational velocity v. Nor is there any correlation when changing to the values of v_0sini and v_0 corresponding to the initial time t = 0. It is noted that the current theoretical models of mixing on the main sequence can explain neither the abrupt increase in He/H at t/t_MS ~ 0.6 nor the lack of correlation with rotation. New high-quality spectroscopic observations of early B stars and new helium-abundance determinations are needed to increase the accuracy of the initial data. In particular, of interest is to obtain accurate values of He/H for pulsating Beta Cep stars, because most of them have relative ages t/t_MS > 0.5.
No associations
LandOfFree
Helium Enrichment of the Atmospheres of B and O Stars: New Aspects of the 20-Year-Old Problem does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Helium Enrichment of the Atmospheres of B and O Stars: New Aspects of the 20-Year-Old Problem, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Helium Enrichment of the Atmospheres of B and O Stars: New Aspects of the 20-Year-Old Problem will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1654242