Long XMM observation of the narrow-line Seyfert 1 galaxy IRAS 13224-3809: rapid variability, high spin and a soft lag
Young, A. J.; Brandt, W. N.; Ponti, G.; Fabian, A. C.; Miller, J. M.; Reynolds, C. S.; Miniutti, G.; Steiner, J. F.; Uttley, P.; Malzac, J.; Nardini, E.; Reis, R. C.; Cackett, E. M.; Gallo, L. C.; Ross, R. R.; Dwelly, T.; Kara, E.; Zoghbi, A.; Wilkins, D. R.; Tanaka, Y.; Walton, D. J.; Chiang, C. -Y.; Boller, T.; Lozanov, K.
United Kingdom, United States, Netherlands, Canada, Spain, Germany
Abstract
The narrow-line Seyfert 1 galaxy IRAS 13224-3809 has been observed with XMM-Newton for 500 ks. The source is rapidly variable on time-scales down to a few 100 s. The spectrum shows strong broad Fe - K and L emission features which are interpreted as arising from reflection from the inner parts of an accretion disc around a rapidly spinning black hole. Assuming a power law emissivity for the reflected flux and that the innermost radius corresponds to the innermost stable circular orbit, the black hole spin is measured to be 0.989 with a statistical precision better than 1 per cent. Systematic uncertainties are discussed. A soft X-ray lag of 100 s confirms this scenario. The bulk of the power-law continuum source is located at a radius of 2-3 gravitational radii.