A search for radio pulsars around low-mass white dwarfs

Low-mass white dwarfs can be produced either in low-mass X-ray binaries by stable mass transfer to a neutron star, or in a common envelope phase with a heavier white dwarf companion. We have searched eight low-mass white dwarf candidates recently identified in the Sloan Digital Sky Survey for radio pulsations from pulsar companions, using the Green Bank Telescope at 340 MHz. We have found no pulsations down to flux densities of 0.6–0.8 mJy kpc
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and conclude that a given low-mass helium-core white dwarf has a probability of <0.18 ± 0.05 of being in a binary with a radio pulsar.