NGC 1365: A low column density state unveiling a low ionization disk wind

We present the time-resolved spectral analysis of the XMM-Newton data of NGC 1365, collected during one XMM-Newton observation, which caught this “changing-look” AGN in a high flux state characterized also by a low column density ($N_{\mathrm{H}}\sim {10}^{22}$ cm ${}^{-2}$) of the X-ray absorber. During this observation the low energy photoelectric cut-off is at about $\sim 1$ keV and the primary continuum can be investigated with the XMM-Newton-RGS data, which show strong spectral variability that can be explained as a variable low $N_{\mathrm{H}}$, which decreased from $N_{\mathrm{H}}\sim {10}^{23}$ cm ${}^{-2}$ to ${10}^{22}$ cm ${}^{-2}$ in a 100 ks time-scale. The spectral analysis of the last segment of the observation revealed the presence of several absorption features that can be associated with an ionized (log $\xi \sim 2$ erg cm s${}^{-1}$) outflowing wind ($v_{\mathrm{o}\mathrm{u}\mathrm{t}}\sim 2000$ km s${}^{-1}$). We detected for the first time a possible P-Cygni profile of the Mg,$\text{textsc}xii$ Ly$\alpha$ line associated with this mildly ionized absorber indicative of a wide angle outflowing wind. We suggest that this wind is a low ionization zone of the highly ionized wind present in NGC 1365, which is responsible for the iron K absorption lines and is located within the variable X-ray absorber. At the end of the observation, we detected a strong absorption line at $E\sim 0.76$ keV most likely associated with a lower ionization zone of the absorber (log $\xi \sim 0.2$ erg cm s${}^{-1}$, $N_{\mathrm{H}}\sim {10}^{22}$ cm ${}^{-2}$), which suggests that the variable absorber in NGC 1365 could be a low ionization zone of the disk wind.