A new way to measure supermassive black hole spin in accretion disc dominated Active Galaxies

Understand

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.