Optical Detection of Two Intermediate Mass Binary Pulsar Companions

We report the detection of probable optical counterparts for two Intermediate Mass Binary Pulsar (IMBP) systems, PSR J1528−3146 and PSR J1757−5322. Recent radio pulsar surveys have uncovered a handful of these systems with putative massive white dwarf companions, thought to have an evolutionary history different from that of the more numerous class of Low Mass Binary Pulsars (LMBPs) with He white dwarf companions. The study of IMBP companions via optical observations offers us several new diagnostics: the evolution of main sequence stars near the white-dwarf-neutron star boundary, the physics of white dwarfs close to the Chandrasekhar limit, and insights into the recycling process by which old pulsars are spun up to high rotation frequencies. We were unsuccessful in our attempt to detect optical counterparts of PSR J1141−6545, PSR J1157−5112, PSR J1435−6100, and PSR J1454−5846. Subject headings: binaries:close — pulsars: general — stars: neutron — white dwarfs Department of Astronomy, California Institute of Technology, MS 105-24, Pasadena, CA 91125; [email protected]. present address: Naval Research Laboratory, Code 7213, 4555 Overlook Avenue, SW, Washington, DC, 20375; [email protected]. Department of Physics and Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139; [email protected]. Department of Astronomy and Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada; [email protected]. present address: Department of Physics and Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139; [email protected].