Simultaneous X-ray and Ultraviolet spectroscopy of the Seyfert galaxy NGC 5548. III. X-ray time variability

Abstract

The Seyfert 1 galaxy NGC 5548 was observed for a week by Chandra using both the HETGS and LETGS spectrometers. In this paper we study the time variability of the continuum radiation. During our observation, the source showed a gradual increase in flux over four days, followed by a rapid decrease and flattening of the light curve afterwards. Superimposed upon these relatively slow variations several short duration bursts or quasi-periodic oscillations occured with a typical duration of several hours and separation between 0.6-0.9 days. The bursts show a delay of the hard X-rays with respect to the soft X-rays of a few hours. We interprete these bursts as due to a rotating, fluctuating hot spot at approximately 10 gravitational radii; the time delay of the hard X-rays from the bursts agree with the canonical picture of Inverse Compton scattering of the soft accretion disk photons on a hot medium that is relatively close to the central black hole.

6 pages, 7 figures, accepted for publication in Astronomy and Astrophysics

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Cited by in corpus (11)

• Simultaneous X-ray and UV spectroscopy of the Seyfert 1 galaxy NGC 5548.II. Physical conditions in the X-ray absorber
• Anatomy of the AGN in NGC 5548 VIII. XMM-Newton's EPIC detailed view of an unexpected variable multilayer absorber
• The structure and X-ray radiation spectra of illuminated accretion disks in AGN. III. Modeling fractional variability
• Smoothed Particle Inference: A Kilo-Parametric Method for X-ray Galaxy Cluster Modeling
• Iron lines from transient and persisting hot spots on AGN accretion disks
• X-ray narrow line region variability as a geometry probe: The case of NGC 5548
• The thermal instability of the warm absorber in NGC 3783
• Simultaneous X-ray and Ultraviolet spectroscopy of the Seyfert galaxy NGC 5548. III. X-ray time variability
• Non-Thermal Emission from AGN Coronae
• Modeling time delays in the X-ray spectrum of the Seyfert galaxy MCG-6-30-15
• Density constraint of the warm absorber in NGC 5548