A 12 DayASCAObservation of the Narrow‐Line Seyfert 1 Galaxy Ton S180: Time‐selected Spectroscopy

P. Romano, T. J. Turner, S. Mathur, I. M. George
2002 Astrophysical Journal  
We present an analysis of the X-ray variability properties of the NLS1 galaxy Ton S180, based upon a 12-day continuous ASCA observation. We observe flux variations of a factor of 3.5 in the 0.7-1.3 keV band and 3.9 in the 2-10 keV band.Time-resolved spectroscopy ( 1d sampling) reveals that the broad 'soft hump' component at energies <2 keV shows flux variations on timescales down to 1 day that are well correlated with the photon index and the 2-10 keV band flux. A broad Fe Kα emission is
more » ... emission is detected. There is a evidence for a narrow Fe Kα line at 6.8 keV, indicating an origin in ionized material. We do not detect significant variations of the line flux or EW on 1 day-1 week timescales. The softness ratio reveals spectral variability on timescales down to 1000 s, indicating that the power-law continuum and soft hump fluxes are not well correlated on this timescale. It also shows a slow decline across the observation, due to a combination of the different time-variability of the power-law continuum and soft hump flux on timescales of 1 week. The X-ray emission originates within 12 Schwarzschild radii, and the amplitudes and timescales of the rapid variations we observed are consistent with those expected within disk-corona models. The soft hump variability timescale rules out an origin in large scale components (circumnuclear starburst). The Γ-soft hump correlation is consistent with the soft hump being produced by up-scattering of the accretion disk radiation within a flaring disk corona.
doi:10.1086/324201 fatcat:6rtxkh2ourd27igyk7ezdo3bny