We report the discovery of 105-ms X-ray pulsations from the compact central object ( CCO ) in the supernova remnant Kes 79 using data acquired with the Newton X-Ray Multi-Mirror Mission .
Two observations of the pulsar taken 6 days apart yield an upper limit on its spin-down rate of \dot { P } < 7 \times 10 ^ { -14 } s s ^ { -1 } and no evidence for binary orbital motion .
The implied energy loss rate is \dot { E } < 2 \times 10 ^ { 36 } ergs s ^ { -1 } , surface magnetic field strength is B _ { p } < 3 \times 10 ^ { 12 } G , and spin-down age is \tau > 24 kyr .
The latter exceeds the remnant ’ s estimated age , suggesting that the pulsar was born spinning near its current period .
The X-ray spectrum of PSR J1852 + 0040 is best characterized by a blackbody model of temperature kT _ { BB } = 0.44 \pm 0.03 keV , radius R _ { BB } \approx 0.9 km , and L _ { bol } = 3.7 \times 10 ^ { 33 } ergs s ^ { -1 } at d = 7.1 kpc .
The sinusoidal light curve is modulated with a pulsed fraction of > 45 \% , suggestive of a small hot spot on the surface of the rotating neutron star .
The lack of a discernible pulsar wind nebula is consistent with an interpretation of PSR J1852 + 0040 as a rotation-powered pulsar whose spin-down luminosity falls below the empirical threshold for generating bright wind nebulae , \dot { E } _ { c } \approx 4 \times 10 ^ { 36 } ergs s ^ { -1 } .
The age discrepancy implies that its \dot { E } has always been below \dot { E } _ { c } , perhaps a distinguishing property of the CCOs .
Alternatively , the X-ray spectrum of PSR J1852 + 0040 suggests a low-luminosity AXP , but the weak inferred B _ { p } field is incompatible with a magnetar theory of its X-ray luminosity .
So far , we can not exclude accretion from a fall-back disk .
The ordinary spin parameters discovered from PSR J1852 + 0040 highlight the difficulty that existing theories of isolated neutron stars have in explaining the high luminosities and temperatures of CCO thermal X-ray spectra .