DY Per is catalogued as type RCB.  However the light curve is unlike any other RCB star known.  The star has only been observed since 1992, and long term monitoring will undoubtedly reveal the true nature of this object.

 

Classical RCB stars are known to be highly luminous, hydrogen deficient stars. DY Per is only moderately hydrogen deficient, with no spectroscopic evidence for high luminosity. Recently a new subgroup of RCB stars has been suggested - the DYPER sub group. The fades and recovery of  DY Per are more symmetrical than classical RCB stars, with the beginning of a decline usually slower, accelerating as the fade progresses. The minima also appears shorter in duration.  

 

A period of 792d has been suggested for DY Per, which is confirmed by simple analysis of the above data.