  Measurements of $\mathrm{B}^*_\mathrm{s2}(5840)^0$ and
$\mathrm{B}_\mathrm{s1}(5830)^0$ mesons are performed using a data sample of
proton-proton collisions corresponding to an integrated luminosity of 19.6
fb$^{-1}$, collected with the CMS detector at the LHC at a centre-of-mass
energy of 8 TeV. The analysis studies $P$-wave $\mathrm{B}^0_\mathrm{S}$ meson
decays into $\mathrm{B}^{(*)+}\mathrm{K}^-$ and
$\mathrm{B}^{(*)0}\mathrm{K}^0_\mathrm{S}$, where the $\mathrm{B}^+$ and
$\mathrm{B}^0$ mesons are identified using the decays
$\mathrm{B}^+\to\mathrm{J}/\psi\,\mathrm{K}^+$ and
$\mathrm{B}^0\to\mathrm{J}/\psi\,\mathrm{K}^*(892)^0$. The masses of the
$P$-wave $\mathrm{B}^0_\mathrm{S}$ meson states are measured and the natural
width of the $\mathrm{B}^*_\mathrm{s2}(5840)^0$ state is determined. The first
measurement of the mass difference between the charged and neutral
$\mathrm{B}^*$ mesons is also presented. The $\mathrm{B}^*_\mathrm{s2}(5840)^0$
decay to $\mathrm{B}^0\mathrm{K}^0_\mathrm{S}$ is observed, together with a
measurement of its branching fraction relative to the
$\mathrm{B}^*_\mathrm{s2}(5840)^0\to\mathrm{B}^+\mathrm{K}^-$ decay.
