Quote:
Originally Posted by Placidus
Thanks for the interesting information Colin. After reading it, I wondered about the difference between an A0 supergiant and a Wolf-Rayet star. I guess an A0 is young, still burning hydrogen, and still on the main sequence, whereas a Wolf-Rayet has stopped burning hydrogen, is burning helium, is throwing off a lot of material, and hasn't got long to go.
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If you have a look at
this link it shows that it has moved above the main sequence and has finished its hydrogen burning phase. It will go through periods of burning hydrogen and the photosphere is still largely hydrogen based (with mixes of other heavier elements that get dredged up) but it's now largely in He/C/O/N burning now.
This paper also talked about it being a variable star but there are some more recent papers that discuss its variability with regards to magnetic fields.
I guess where things ultimately get difficult and confusing is that not all big bright stars become WR stars. A stars metallicity plays quite a large roll in it. The less metals there are the faster and hotter it burns which also means larger stars. If it is a faster rotating star it tends to dredge up more heavier metals up once it leaves the main sequence. Having more heavier metals towards the chromosphere seems to be one factor in heavy mass loss.
This paper suggests that it isn't self enrichment (dredging up) that is a likely cause of what creates a WR star but more likely to be a star with an initially higher Fe/H so it would have to be a fair bit higher than average as WR stars aren't hugely common compared to the amount of A&O type stars out there.