How do K, F, A and B stars die?

Question

I know that M (red dwarf) main-sequence stars slowly fade to white dwarf stars, and that G (yellow dwarf) main-sequence stars become red giants and then shed their outer layers in a planetary nebula leaving behind a white dwarf, but do K (orange dwarf) main stars take a similar route to red dwarfs? Or do they expand into red giants like yellow dwarfs?

What about F (yellow-white) main-sequence stars? Do they turn into supergiants and go supernova? Or do they take a similar route to yellow dwarfs? And what about A (white) and B (blue-white) main-sequence stars?

Answer 1

K-type dwarfs behave like stars of a solar mass star but on longer timescales, and will leave behind a (slightly) lower mass ($<0.5M_\odot$) white dwarf at the ends of their lives.

F-type dwarfs will behave like solar mass stars but on faster timescales and leave behind a (slightly) higher mass ($\sim 0.6M_\odot$) white dwarf. In fact, these will be the progenitors of the most of the white dwarfs we see in our Galaxy.

Higher mass (hotter) stars will produce higher mass white dwarfs, up until the initial main sequence star is of about $8M_{\odot}$ (a spectral type of about B3V). The corresponding remnant white dwarf mass will increase up to about $\sim 1.2 M_{\odot}$ - which are the most massive white dwarfs produced via normal, single-star evolution.

All these stars will go through a "first ascent" red giant phase, He core burning and asymptotic giant branch phases.

Above an intial $8M_\odot$, then carbon burning will be initiated in the core and it is likely$^\dagger$ that burning will continue through to iron, followed by core-collapse and a supernova.

$\dagger$ It is possible that stars between $8-10M_\odot$, which would be early B-stars on the main sequence, may halt burning at O/Ne/Mg and form a higher mass white dwarf or even explode directly in an electron capture supernova.

Answer 2

I suppose, there must be some set of evolved early-type low-metallicity K-dwarfs that are going through or entering subgiant phase nowadays.

In theory, even early-type M-dwarfs with initial mass > 0.3 Msol can produce some kind of "small red giants", leaving He-cores (white dwarfs) after the end of their life. This type of stars should not ever go through core He-burning main sequence and, respectively, asymptotic giant branch (AGB) phase. But we'll never see their red giant branches (RGB) on the HR-diagram )