Astronomy C Question Marathon

[syo_astro]

Yeah, bbgun had what I was looking for, sorry forever. I actually wasn't looking for accretion-powered since it actually is powered by thermonuclear runaway (unless you better defined what you said than from my perspective), which makes it closer to classical novae than dwarf novae (at least I think from what I read?), but at least bbgun got the NRA part.

[bbgun34]

Alright, new question:

How come people describe Abell 30 as "born again?"

[AlphaTauri]

planetary nebulaception (Click to Show Hidden Text)

The star went through its RG phase and ejected its outer layers to form a planetary nebula, but then fusion reignited and the star went through another round of being a red giant and ejecting its outer layers, creating a second PNe inside the first

[alpacas]

answer (Click to Show Hidden Text)

the progenitor star of Abell 30 originally went through thermonuclear explansion 12,500 years ago and shed its outer layers, then 850 years ago the progenitor star was essentially reborn and re-shed He and C layers after nuclear reactions and such brought enough nebulous material back to the WD to eventually give it two planetary nebulas like it was reborn

*edit sorry for reanswering I didnt see there was already an answer by alphatauri

[bbgun34]

yup yup yup

[AlphaTauri]

Okay, then I guess it's my turn to post a question?

Is V1 a Type I or Type II Cepheid? Prove it mathematically -- using P-L, distance mod, etc.

(syo_astro, you're not allowed to answer this one because you've already done it :P)

[alpacas]

ANSWER (Click to Show Hidden Text)

[img]http://i39.tinypic.com/ydif7.png[/img]

*edit to be entirely honest I'm not sure what you meant by "prove"

[AlphaTauri]

Yep, that's basically what I was looking for, showing that a Type I Cepheid would match the distance to M31 (I realize that question was kind of vaguely worded). syo and I, being crazy astro people, actually did those calculations to confirm what kind of Cepheid V1 was... instead of being reasonable people and looking it up.

Your turn!

[alpacas]

Astronomers have calculated the lower limit for the mass of the black hole GRS 1915+105 given that the velocity amplitude of the mass donator star is 140±15 km/s. Please find this lower limit and show work thank you!

[Crazy Puny Man]

alpacas, if you don't mind me asking, where did you get that period-luminosity relationship for Type II cepheids?