In recent years , the stars of the Of ? p category have revealed a wealth of peculiar phenomena : varying line profiles , photometric changes , and X-ray overluminosity are only a few of their characteristics .
Here we review their physical properties , to facilitate comparisons among the Galactic members of this class .
As one of them has been proposed to resemble the magnetic oblique rotator \theta ^ { 1 } Ori C , though with a longer period , this latter object is also included in our study to illuminate its similarities and differences with the Of ? p category .