If I remember correctly, it depends on whether or not they're "hot" or "cold"
The ones you described are "hot" subdwarfs.
"cold" subdwarfs have a very low metallicity, which means they are more transparent and thus there's less radiation pressure pushing outwards on the outer layers of the star, making them smaller and warmer.
If I remember correctly, it depends on whether or not they're "hot" or "cold"
The ones you described are "hot" subdwarfs.
"cold" subdwarfs have a very low metallicity, which means they are more transparent and thus there's less radiation pressure pushing outwards on the outer layers of the star, making them smaller and warmer.