Why Do Astronomers Believe the Binary Companions of the White

question 285

Multiple Choice

Why do astronomers believe the binary companions of the white dwarfs that produce Type Ia supernovae are MOST probably main-sequence stars?

• A) Only main-sequence stars have lifetimes that would allow them to fill their Roche lobes at the same time their companion (formed at the same time) is a white dwarf.
• B) We detect white dwarf binaries mostly by the astrometric method of looking for a wobble in the primary star's motion. Only a main-sequence star would be massive enough for this wobble to be detected.
• C) A smaller star would not be able to fill its Roche lobes, and a larger star would swallow the white dwarf before it could produce a supernova.
• D) The supernova explosion will cause the atmosphere of the binary companion to glow. We do not detect enough afterglow to suggest a giant or supergiant as companion.

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