Spectral-timing of AGN ionized outflows with Athena
By Anna Juráňová
X-ray spectra of many variable active galactic nuclei (AGNs) show absorption features produced by outflowing photoionized gas. While being common, the effect of these outflows on the surrounding environment or their location within the system is hard to determine. For this to be understood, we need to estimate the gas density, which is a notoriously difficult task.
In this paper, we show results from simulations of the observable behaviour of such outflows in the changing conditions of a highly variable AGN. We prove that the key missing information can be derived from the time-variability properties of the absorbing gas. In particular, we show that the gas density, and consequently its distance to the central region, can be determined from the signal coherence, which quantifies the linearity of the relation between the absorbed and unabsorbed spectral bands. However, high spectral resolution and large effective area are necessary to constrain these properties reliably. We show that with the capabilities of Athena with the X-ray Integral Field Unit (X-IFU) onboard, it will be possible to make these measurements, revolutionising our understanding of the processes which shape AGN and their surroundings.