Is it possible that a star with an initial mass greater than $12 M_\odot$ loses so much mass in the giant phase that it eventually becomes a white dwarf? If it is possible, what constellation or environment would be favourable for this to happen, e.g. a companion of an already present neutron star, the dense population of a globular cluster, or...?
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2 Answers
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The usual maximum mass that is quoted for a white dwarf progenitor of $\sim 8M_\odot$ is empirically determined from young, local star clusters that have (roughly) a similar composition to the Sun. Any theoretical calculation of that maximum mass is quite dependent on the prescription of mass loss during the red giant branch and the asymptotic giant branch, which is itself highly uncertain, so the empirical limit is preferred.
Having said that, we would need some reason then why a $12 M_\odot$ star might lose more mass than similar high mass stars in local open clusters? I can think of two possible reasons. Firstly, radiation-driven mass loss is highly dependent on metallicity. A star with a metallicity much greater than the Sun might be expected to lose more of its envelope during the giant phases and thus could still leave a core lower than the Chandrasekhar limit, leading to a stable white dwarf. Second, binary interactions could lead to stripping of the progenitor star's envelope by a binary companion. This is the scenario thought to lead to low-mass helium white dwarfs, despite there being no evolutionary scenario for single stars that could produce such objects in the lifetime of the Galaxy. I would assume that if such interactions took place prior to the progenitor forming a C/O core, it could lead to the formation of a white dwarf.
In terms then of what environments might favour these scenarios - high metallicity environments (the Galactic bulge?) or regions featuring lots of binary stars (though most high mass stars are in binary systems).
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Yes, it is theoretically possible for a star with an initial mass greater than 12 solar masses (M⊙) to lose enough mass during its giant phase to eventually become a white dwarf. While the typical end life for a star with an initial mass greater than 12M⊙ is as a neutron star or black hole, under specific conditions such as significant mass loss in a binary system or rare dynamical interactions in dense stellar environments, such a star could indeed become a white dwarf. These scenarios, are very rare.
