The core - collapse of a hydrogen rich massive star most often results in a supernova ( SN ) with a plateau phase in its light curve .
However , in some cases we do not observe this plateau .
We present observations of the unusually luminous supernova 2016gsd that displays little evidence of the expected drop from the optically thick phase to the radioactively powered tail .
With a peak absolute magnitude of V = - 19.95 \pm 0.08 , this object is one of the brightest type II SNe , and lies in the gap of magnitudes between the majority of type II SNe and the superluminous SNe .
The velocities derived from the absorption in H \alpha are also unusually high with the blue edge tracing the fastest moving gas initially at 20000 km s ^ { -1 } and then declining approximately linearly to 15000 km s ^ { -1 } over \sim 100 days .
The dwarf host galaxy of the SN indicates a low metallicity progenitor which may also contribute to the weakness of the metal lines in its spectra .
We examine SN 2016gsd with reference to similarly luminous , linear type II SNe such as SNe 1979C and 1998S , and discuss the interpretation of its observational characteristics .
We compare the observations with a model produced by the JEKYLL code and find that a massive star with a depleted and inflated hydrogen envelope struggles to reproduce the high luminosity and extreme linearity of SN 2016gsd .
Instead , we suggest that the influence of interaction between the SN ejecta and circumstellar material can explain the majority of the observed properties of the SN .
The high velocities and strong H \alpha absorption present throughout the evolution of the SN may imply a CSM configured in an asymmetric geometry .