When our sun exhausts the hydrogen in the core, it will swell as a red giant, encompass the orbits of Mercury and Venus, and likely come very close to earth.
"Black hole B" is currently ten times the mass of our sun. The star that produced it was likely much more massive still. The red giant phase of such a star might have reached to Neptune, so there is no way that these two evolved together.
When the star in this pair exhausts its hydrogen, the black hole will drain the red giant that it becomes.
Disclaimer: I can't make any calculation but... Wouldn't Star A keep orbiting Star B inside the surface of Red Giant Star B, which wouldn't be very dense at the radius of the orbit? There is drag but a lot of inertia. Star A would start from further away than now. It would probably get some extra mass in the process, absorbing the gas of the red giant.
When our sun exhausts the hydrogen in the core, it will swell as a red giant, encompass the orbits of Mercury and Venus, and likely come very close to earth.
"Black hole B" is currently ten times the mass of our sun. The star that produced it was likely much more massive still. The red giant phase of such a star might have reached to Neptune, so there is no way that these two evolved together.
When the star in this pair exhausts its hydrogen, the black hole will drain the red giant that it becomes.