The lively accretion disc in NGC 2992. III. Tentative evidence of rapid Ultra Fast Outflow variability

Abstract

We report on the 2019 XMM-Newton+NuSTAR monitoring campaign of the Seyfert galaxy NGC 2992, observed at one of its highest flux levels in the X-rays. The time-averaged spectra of the two XMM-Newton orbits show Ultra Fast Outflows (UFOs) absorbing structures above 9 keV with $> 3 \sigma$ significance. A detailed investigation of the temporal evolution on a $\sim$5 ks time scale reveals UFO absorption lines at a confidence level $>$95% (2$\sigma$) in 8 out of 50 XMM-Newton segments, estimated via Monte Carlo simulations. We observe a wind variability corresponding to a length scale of 5 Schwarzschild radii $r_S$. Adopting the novel Wind in the Ionised Nuclear Environment (WINE) model, we estimate the outflowing gas velocity ($v=0.21-0.45 c$), column density ($N_H=4-8\cdot 10^{24} cm^{-2}$) and ionisation state ($\log(\xi_0/erg\ cm\ s^{-1})=3.7-4.7$), taking into account geometrical and special relativity corrections. These parameters lead to instantaneous mass outflow rates $\dot{M}_{out}\simeq0.3-0.8 M_{\odot} yr^{-1}$, with associated outflow momentum rates $\dot{p}_{out}\simeq 20-90 L_{Bol}/c$ and kinetic energy rates $\dot{E}_K \simeq 2-25 L_{Bol}$. We estimate a wind duty cycle $\approx$ 12% and a total mechanical power $\approx$ 2 times the AGN bolometric luminosity, suggesting the wind may drive significant feedback effects between the AGN and the host galaxy. Notably, we also provide an estimate for the wind launching radius and density $\approx 5 r_S, 10^{11} {cm}^{-3}$, respectively.