Astrophysics LETTERS The nature of the companion of PSR J1719–1438: a white dwarf or an exotic object?

Abstract We raise the possibility that the very dense, compact companion of PSR J1719–1438, which has a Jupiter-like mass, is an exotic quark object rather than a light helium or carbon white dwarf. The exotic hypothesis naturally explains some of the observed features, and provides quite strong predictions for this system, to be confirmed or refuted in feasible future studies. Key words: binary pulsars — exotic matter — pulsars: individual (PSR J1719–1438)