A new way to measure supermassive black hole spin in accretion disc
  dominated Active Galaxies
  We show that disc continuum fitting can be used to constrain black hole spin
in a subclass of Narrow Line Seyfert 1 (NLS1) AGN as their low mass and high
mass accretion rate means that the disc peaks at energies just below the soft
X-ray bandpass. We apply the technique to the NLS1 PG1244+026, where the
optical/UV/X-ray spectrum is consistent with being dominated by a standard disc
component. This gives a best estimate for black hole spin which is low, with a
firm upper limit of $a_*<0.86$. This contrasts with the recent X-ray
determinations of (close to) maximal black hole spin in other NLS1 based on
relativistic smearing of the iron profile. While our data on PG1244+026 does
not have sufficient statistics at high energy to give a good measure of black
hole spin from the iron line profile, cosmological simulations predict that
black holes with similar masses have similar growth histories and so should
have similar spins. This suggests that there is a problem either in our
understanding of disc spectra, or/and X-ray reflection or/and the evolution of
black hole spin.
