  One of the most well-studied exoplanets to date, HD 189733 b, stands out as
an archetypal hot Jupiter with many observations and theoretical models aimed
at characterizing its atmosphere, interior, host star, and environment. We
report here on the results of an extensive campaign to observe atmospheric
escape signatures in HD 189733 b using the Hubble Space Telescope and its
unique ultraviolet capabilities. We have found a tentative, but repeatable
in-transit absorption of singly-ionized carbon (C II, $5.2\% \pm 1.4\%$) in the
epoch of June-July/2017, as well as a neutral hydrogen (H I) absorption
consistent with previous observations. We model the hydrodynamic outflow of HD
189733 b using an isothermal Parker wind formulation to interpret the
observations of escaping C and O nuclei at the altitudes probed by our
observations. Our forward models indicate that the outflow of HD 189733 b is
mostly neutral within an altitude of $\sim 2$ R$_\mathrm{p}$ and singly ionized
beyond that point. The measured in-transit absorption of C II at 133.57 nm is
consistent with an escape rate of $\sim 1.1 \times 10^{11}$ g$\,$s$^{-1}$,
assuming solar C abundance and outflow temperature of $12\,100$ K. Although we
find a marginal neutral oxygen (O I) in-transit absorption, our models predict
an in-transit depth that is only comparable to the size of measurement
uncertainties. A comparison between the observed Lyman-$\alpha$ transit depths
and hydrodynamics models suggests that the exosphere of this planet interacts
with a stellar wind at least one order of magnitude stronger than solar.
