  We report on the precise mass measurement of the $^{173}$Hf isotope performed
at the Ion Guide Isotope Separator On-Line facility using the JYFLTRAP double
Penning trap mass spectrometer. The new mass-excess value, ${\mathrm{ME} =
-55390.8(30)}$ keV, is in agreement with the literature while being nine times
more precise. The newly determined $^{173}$Hf electron-capture $Q$ value,
$Q_{EC} = 1490.2(34)$ keV, allows us to firmly reject the population of an
excited state at 1578 keV in $^{173}$Lu and 11 transitions tentatively assigned
to the decay of $^{173}$Hf. Our refined mass value of $^{173}$Hf reduces
mass-related uncertainties in the reaction rate of
$^{174}$Hf$(\gamma,n)^{173}$Hf. Thus, the rate for the main photodisintegration
destruction channel of the $p$ nuclide $^{174}$Hf in the relevant temperature
region for the $\gamma$ process is better constrained.
