  The AGN STORM 2 collaboration targeted the Seyfert 1 galaxy Mrk 817 for a
year-long multiwavelength, coordinated reverberation mapping campaign including
HST, Swift, XMM-Newton, NICER, and ground-based observatories. Early
observations with NICER and XMM revealed an X-ray state ten times fainter than
historical observations, consistent with the presence of a new dust-free,
ionized obscurer. The following analysis of NICER spectra attributes
variability in the observed X-ray flux to changes in both the column density of
the obscurer by at least one order of magnitude ($N_\mathrm{H}$ ranges from
$2.85\substack{+0.48\\ -0.33} \times 10^{22}\text{ cm}^{-2}$ to
$25.6\substack{+3.0\\ -3.5} \times 10^{22} \text{ cm}^{-2}$) and the intrinsic
continuum brightness (the unobscured flux ranges from $10^{-11.8}$ to
$10^{-10.5}$ erg s$^{-1}$ cm$^{-2}$ ). While the X-ray flux generally remains
in a faint state, there is one large flare during which Mrk 817 returns to its
historical mean flux. The obscuring gas is still present at lower column
density during the flare but it also becomes highly ionized, increasing its
transparency. Correlation between the column density of the X-ray obscurer and
the strength of UV broad absorption lines suggests that the X-ray and UV
continua are both affected by the same obscuration, consistent with a clumpy
disk wind launched from the inner broad line region.
