We re-examine the properties of the high-velocity and extremely low-mass white dwarf LP 400-22 and its close companion .
Based on an extended observation timeline , we determined a binary period of P = 1.01016 d , somewhat longer than the previously published period , and a mass function f ( M _ { 2 } ) = 0.180 M _ { \odot } , implying a mass for the companion M _ { 2 } > 0.41 M _ { \odot } .
We also re-appraised the mass and cooling age of the white dwarf using low-metallicity ( Z = 0.001 ) evolutionary models appropriate for an old halo member , M _ { 1 } = 0.19 M _ { \odot } , and t _ { cool } \approx 1.8 Gyr , and we infer a mass of 0.85 - 1.0 M _ { \odot } for the progenitor of the white dwarf .
We discuss the likely origin of this system .