Detection of X-ray Emission from the Very Old Pulsar J0108-1431
Abstract
PSR J0108-1431 is a nearby, 170 Myr old, very faint radio pulsar near the "pulsar death line" in the P-Pdot diagram. We observed the pulsar field with the Chandra X-ray Observatory and detected a point source (53 counts in a 30 ks exposure, energy flux (9+/-2)× 10-15 ergs cm-2 s-1 in the 0.3-8 keV band) close to the radio pulsar position. Based on the large X-ray/optical flux ratio at the X-ray source position, we conclude that the source is the X-ray counterpart of PSR J0108-1431.The pulsar spectrum can be described by a power-law model with photon index Gamma ≈ 2.2 and luminosity L0.3-8 keV 2× 1028 d1302 ergs s-1, or by a blackbody model with the temperature kT≈ 0.28 keV and bolometric luminosity Lbol 1.3× 1028 d1302 ergs s-1, for a plausible hydrogen column density NH = 7.3× 1019 cm-2 (d130=d/130 pc). The pulsar converts 0.4% of its spin-down power into the X-ray luminosity, i.e., its X-ray efficiency is higher than for most younger pulsars. From the comparison of the X-ray position with the previously measured radio positions, we estimated the pulsar proper motion of 0.2 arcsec yr-1 (V 130 d130 km s-1), in the south-southeast direction.