Distance, Energy, and Variability of Quasar Outflows: Two HST/COS epochs of LBQS 1206+1052

We analyze new HST/COS spectra for two quasar absorption outflows seen in the quasi-stellar object LBQS 1206+1052. These data cover, for the first time, absorption troughs from $S_{IV}$, $S{i}_{II}$, and $P_V$. From the ratio of the $S_{IV}$* to $S_{IV}$ column densities, we measure the electron number density of the higher-velocity ($-1400$ km s${}^{-1}$, v1400) outflow to be log($n_e$) = $4.23_{-0.09}^{+0.09}$ cm${}^{-3}$ and constrain the lower-velocity ($-730$ km s${}^{-1}$, v700) outflow to log($n_e$) $>$ $5.3$ cm${}^{-3}$. The $n_e$ associated with the higher-velocity outflow is an order of magnitude larger than reported in prior work. We find that the previous measurement was unreliable since it was based on density-sensitive absorption troughs that were likely saturated. Using photoionization models, we determine the best ${\chi }^2$-minimization fit for the ionization parameter and hydrogen column density of the higher-velocity outflow: log($U_H$) = $-1.73_{-0.12}^{+0.21}$ and log($N_H$) = $21.03_{-0.15}^{+0.25}$ cm${}^{-2}$, respectively. We calculate from $U_H$ and $n_e$ a distance of $500_{-110}^{+100}$ pc from the central source to the outflow. Using an SED attenuated by the v700 outflow yields a two-phase photoionization solution for the v1400 outflow, separated by a $\Delta U \approxeq 0.7$. Otherwise, the resultant distance, mass flux, and kinetic luminosity are similar to the unattenuated case. However, the attenuated analysis has significant uncertainties due to a lack of constraints on the v700 outflow in 2017.