  Hot subdwarfs in close binaries with either M dwarf, brown dwarf or white
dwarf companions show unique light variations. In hot subdwarf binaries with M
dwarf or brown dwarf companions we can observe the so-called reflection effect
and in hot subdwarfs with close white dwarf companions ellipsoidal modulation
and/or Doppler beaming. Aims. The analysis of these light variations can be
used to derive the mass and radius of the companion and hence determine its
nature. Thereby we assume the most probable sdB mass and the radius of the sdB
derived by the fit of the spectral energy distribution and the Gaia parallax.
In the high signal-to-noise space-based light curves from the Transiting
Exoplanet Survey Satellite and the K2 space mission, several reflection effect
binaries and ellipsoidal modulation binaries have been observed with much
better quality than possible for ground-based observations. The high quality of
the light curves allowed us to analyse a large sample of sdB binaries with M
dwarf or white dwarf companions using lcurve. For the first time we can
constrain the absolute parameters of 19 companions of reflection effect systems
covering periods from 2.5 to 19 hours and companion masses from the hydrogen
burning limit to early M dwarfs. Moreover, we could determine the mass of eight
white dwarf companion to hot subdwarf binaries showing ellipsoidal modulations,
covering a so far unexplored period range from 7 to 19 hours. The derived
masses of the white dwarf companions show that all but two of the white dwarf
companions are most likely helium-core white dwarfs. Combining our results with
previously measured rotation velocities allowed us to derive the rotation
period of seven sdBs in short-period binaries. In four of those systems the
rotation period of the sdB agrees with a tidally locked orbit, in the other
three systems the sdB rotates significantly slower.
