  Ultraprecise space photometry enables us to reveal light variability even in
stars that were previously deemed constant. A large group of such stars show
variations that may be rotationally modulated. This type of light variability
is of special interest because it provides precise estimates of rotational
rates. We aim to understand the origin of the light variability of K2 targets
that show signatures of rotational modulation. We used phase-resolved
medium-resolution XSHOOTER spectroscopy to understand the light variability of
the stars KIC~250152017 and KIC~249660366, which are possibly rotationally
modulated. We determined the atmospheric parameters at individual phases and
tested the presence of the rotational modulation in the spectra. KIC 250152017
is a HgMn star, whose light variability is caused by the inhomogeneous surface
distribution of manganese and iron. It is only the second HgMn star whose light
variability is well understood. KIC 249660366 is a He-weak, high-velocity
horizontal branch star with overabundances of silicon and argon. The light
variability of this star is likely caused by a reflection effect in this
post-common envelope binary.
