Detection of X-ray emission from the very old pulsar J0108-1431

PSR J0108-1431 is a nearby, 170 Myr old, very faint radio pulsar near the "pulsar death line" in the P- 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 erg 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 Γ ≈ 2.2 and luminosity L _0.3-8 keV ≈ 2 × 10²⁸ d ² ₁₃₀ erg s^-1, or by a blackbody model with temperature kT ≈ 0.28 keV and bolometric luminosity L _bol ≈ 1.3 × 10²⁸ d ² ₁₃₀ erg s^-1, for a plausible hydrogen column density N _H = 7.3 × 10¹⁹ cm^-2 (d ₁₃₀ = d/130 pc). The pulsar converts ∼0.4% of its spin-down power into 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 ≈ 130d ₁₃₀ km s^-1), in the south-southeast direction.