On the nature of Hydrogen-rich Superluminous Supernovae
  We present two hydrogen-rich superluminous supernovae (SLSNe), namely
SN2013hx and PS15br. These objects, together with SN2008es are the only SLSNe
showing a distinct, broad Halpha feature during the photospheric phase and also
do not show any sign of strong interaction between fast-moving ejecta and
circumstellar shells in their early spectra. Despite PS15br peak luminosity is
fainter than the other two objects, the spectrophotometric evolution is similar
to SN2013hx and different than any other supernova in a similar luminosity
space. We group all of them as SLSNe II and hence distinct from the known class
of SLSN IIn. Both transients show a strong, multi-component Halpha emission
after 200 days past maximum which we interpret as an indication of interaction
of the ejecta with an asymmetric, clumpy circumstellar material. The spectra
and photometric evolution of the two objects are similar to type II supernovae,
although they have much higher luminosity and evolve on slower timescales. This
is qualitatively similar to how SLSNe I compare with normal type Ic in that the
former are brighter and evolve more slowly. We apply a magnetar and an
interaction semi-analytical codes to fit the light curves of our two objects
and SN2008es. The overall observational dataset would tend to favour the
magnetar, or central engine, model as the source of the peak luminosity
although the clear signature of late-time interaction indicates that
interaction can play a role in the luminosity evolution of SLSNe II at some
phases.
