Optical Studies of Millisecond Pulsar Companions
نویسندگان
چکیده
In observations of four binary millisecond pulsars with the Palomar 200-inch telescope , we have detected white dwarf companions to PSRs J1640+2224 and J2145?0750 and placed upper limits of m r = 24 and m r = 25 on companions to PSRs J0751+1807 and J2229+2643. The temperature inferred for the companion to PSR J1640+2224 is T = (3700 300) K. The luminosity inferred for a star at a distance of 1.2 kpc is consistent with that expected from a (2 1) 10 9 yr-old helium white dwarf. For PSR J2145?0750 the measured colors are inconsistent, possibly due to a combination of emission lines in the spectrum and systematic eeects introduced when subtracting a nearby star. The companion temperature derived lies in the range 4300 K to 6800K. For a carbon-oxygen white dwarf, the corresponding cooling age is 2{610 9 yr. The cooling ages of both systems with detected white dwarf companions are signiicantly less than the upper limits from the pulsar spin-down ages. For both pulsars, the inferred accretion rate for mass transfer during Roche-lobe overrow is two orders of magnitude below Eddington accretion rates.
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