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I'm not sure how those are called so let me explain what I mean by "P-type asymmetrical binaries" - I'm thinking of two stars of very different masses (originally) that orbit each-other fairly closely. For example, let's say one is a blue star at 5-8 M☉ and another is a red dwarf at 0.5 M☉.

So my questions are:

  1. I'm assuming such systems aren't the most easy to observe because blue stars of that range live only hundreds of My, shine bright and aren't so common. How likely are binaries of significantly different masses (without observational biases)?

  2. Based on a paper I found on RD-WD binaries, we know of systems that had smaller main stars as progenitors for the white dwarf. And it seems that roughly a quarter of the binaries they looked at are very close to one another, so that the red dwarf's orbit degraded inwards because of friction with the primary's atmosphere when it was going through the AGB phase. How much mass can the red dwarf accrete during this process? Can they be close enough so that the RD doubles or triples in mass? (that would only be 1 solar mass, and a primary of 5-8 M☉ will be ejecting many times that amount.)

  3. If the answer for 2 is yes, then the WD will be able to accrete back some mass as the now G or K star ages (the star that used to be a red dwarf). I assume that means periodical novae and eventually a type Ia supernova, especially for a progenitor of this size. Can a system like that maintain some habitable planets between the time the WD was formed and novae started happening? (for example if the system originally had a mini-Neptune that was ablated into an Earth-like planet when the WD was forming)

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  • $\begingroup$ Habitable? I wouldn't like to be in a system with an AGB. Those things make a lot of mess! $\endgroup$
    – PM 2Ring
    Dec 23, 2019 at 14:55
  • $\begingroup$ Of course most things from before the AGB are gone, but I can imagine a situation where a gas planet is ablated and decays in orbit... Alternatively, let's consider the highly unlikely situation of capturing a planet... The question is more about "what is the habitable zone in a system with one K/M/G and a WD (and a planetary nebula)?" $\endgroup$
    – Rosh
    Dec 23, 2019 at 15:01

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