The Case for Hypercritical Accretion in M33 X-7

Understand

The spin parameter of the black hole in M33 X-7 has recently been measured to be a*=0.77+-0.05 (Liu et al.

• 2008).
• It has been proposed that the spin of the 15.65 M_sun black hole is natal.
• We show that this is not a viable evolutionary path given the observed binary orbital period of 3.45 days since the explosion that would produce a black hole with the cited spin parameter and orbital period would disrupt the binary.