When We See X- Rays from an Accretion Disk in a Binary

question 108

Multiple Choice

When we see X- rays from an accretion disk in a binary system, we can't immediately tell whether the accretion disk surrounds a neutron star or a black hole. Suppose we then observe each of the following phenomena in this system. Which one would rule out the possibility of a black hole?

• A)bright X- ray emission that varies on a time scale of a few hours
• B)intense X- ray bursts
• C)visible and ultraviolet light from the companion star
• D)spectral lines from the companion star that alternately shift to shorter and longer wavelengths

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