We re-analyzed soft X-ray data collected with the ROSAT and ASCA observatories on a candidate neutron star ( NS ) near the center of the supernova remnant PKS 1209–52 .
We fitted the observed spectra with NS atmosphere models .
The hydrogen atmosphere fits yield more realistic parameters of the NS and the intervening hydrogen column than the traditional blackbody fit .
In particular , for a NS of mass 1.4 ~ { } M _ { \odot } and radius 10 km , we obtained the NS surface temperature T _ { eff } = ( 1.4 - 1.9 ) \times 10 ^ { 6 } K and distance d = 1.6 - 3.3 kpc versus T = ( 4.2 - 4.6 ) \times 10 ^ { 6 } K and ( implausible ) d = 11 - 13 kpc for the blackbody fit , at a 90 % confidence level .
Our fits suggest that the surface magnetic field is either very weak , B \raisebox { -2.58 pt } { \mbox { $ \stackrel { < } { \mbox { \scriptsize$ \sim$ } } \ > $ } } 10 ^ { 10 } G , or it exceeds \simeq 2 \times 10 ^ { 12 } G. The hydrogen column density inferred from the atmosphere fits , n _ { H } = ( 0.7 - 2.2 ) \times 10 ^ { 21 } cm ^ { -2 } , agrees fairly well with independent estimates obtained from UV observations of nearby stars , radio data , and X-ray spectrum of the shell of the supernova remnant , whereas the blackbody and power-law fits give considerably lower and greater values , n _ { H } = ( 0.2 - 0.4 ) \times 10 ^ { 21 } and ( 5.2 - 7.0 ) \times 10 ^ { 21 } cm ^ { -2 } , respectively .
The inferred NS surface temperature is consistent with standard NS cooling models .