We detected X-ray emission from the Vela-like pulsar B1800 - 21 and resolved its synchrotron nebula with the Chandra X-ray Observatory .
The pulsar ’ s flux is F _ { psr } = ( 1.4 \pm 0.2 ) \times 10 ^ { -14 } ergs cm ^ { -2 } s ^ { -1 } in the 1–6 keV band .
Its spectrum can be described by a two-component power law ( PL ) + blackbody model , suggesting a mixture of thermal and magnetospheric emission .
For a plausible hydrogen column density n _ { H } = 1.4 \times 10 ^ { 22 } cm ^ { -2 } , the PL component has a slope \Gamma _ { psr } = 1.4 \pm 0.6 and a luminosity L _ { psr } ^ { nonth } \approx 4 \times 10 ^ { 31 } ( d / 4 { kpc } ) ^ { 2 } ergs s ^ { -1 } .
The properties of the thermal component ( kT \sim 0.1 –0.3 keV , L _ { psr } ^ { bol } \sim 10 ^ { 31 } – 10 ^ { 33 } ergs s ^ { -1 } ) are very poorly constrained because of the strong interstellar absorption .
The compact , \approx 7 ^ { \prime \prime } \times 4 ^ { \prime \prime } , inner pulsar-wind nebula ( PWN ) , elongated perpendicular to the pulsar ’ s proper motion , is immersed in a fainter asymmetric emission .
The observed flux of the PWN , including its fainter component , is F _ { pwn } = ( 5.5 \pm 0.6 ) \times 10 ^ { -14 } ergs cm ^ { -2 } s ^ { -1 } in the 1–8 keV band .
The PWN spectrum can be described by a PL model : \Gamma _ { pwn } \simeq 1.6 \pm 0.3 , L _ { pwn } \approx 1.6 \times 10 ^ { 32 } ( d / 4 { kpc } ) ^ { 2 } ergs s ^ { -1 } , for n _ { H } = 1.4 \times 10 ^ { 22 } cm ^ { -2 } .
The elongation of the inner PWN with respect to the direction of the pulsar ’ s proper motion suggests that its X-ray emission emerges from a torus associated with the termination shock in the equatorial pulsar wind .
Such an interpretation provides additional support for the alignment between the pulsar ’ s velocity and the spin axis found for several other pulsars .
The asymmetry in the fainter , more extended emission could be attributed to nonuniform properties of the ambient medium .
A lack of any signs of bow-shock morphology suggests that the pulsar moves subsonically in high-pressure interiors of a supernova remnant .
However , similar to a few other Vela-like pulsars , no supernova remnant is seen in the Chandra image , possibly because its soft X-ray emission is absorbed by the interstellar medium .
The inferred PWN-pulsar properties ( e.g. , the PWN X-ray efficiency , L _ { pwn } / \dot { E } \sim 10 ^ { -4 } ; the luminosity ratio , L _ { pwn } / L _ { psr } ^ { nonth } \approx 4 ; the pulsar wind pressure at the termination shock , p _ { s } \sim 10 ^ { -9 } ergs cm ^ { -3 } ) are very similar to those of other subsonically moving Vela-like objects detected with Chandra ( L _ { pwn } / \dot { E } \sim 10 ^ { -4.5 } – 10 ^ { -3.5 } , L _ { pwn } / L _ { psr } ^ { nonth } \sim 5 , p _ { s } \sim 10 ^ { -10 } – 10 ^ { -8 } ergs cm ^ { -1 } ) .