A 12-day ASCA Observation of the Narrow-Line Seyfert 1 Galaxy Ton S180: Time-Selected Spectroscopy

Abstract

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 K$\alpha$ emission is detected. There is a evidence for a narrow Fe K$\alpha$ 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 $\Gamma$-soft hump correlation is consistent with the soft hump being produced by up-scattering of the accretion disk radiation within a flaring disk corona.

11 pages, 9 figures; accepted for publication in The Astrophysical Journal, LaTeX emulateapj.sty

References in corpus (3)

• High-Resolution X-ray and Ultraviolet Spectroscopy of the Complex Intrinsic Absorption in NGC 4051 with Chandra and HST
• Multiwavelength Monitoring of the Narrow-Line Seyfert 1 Galaxy Akn 564. I. ASCA Observations and the Variability of the X-ray Spectral Components
• Chandra Grating Spectroscopy of the Seyfert Galaxy Ton S180

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