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 near the pulsar death line in the P- diagram. We observed the 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 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 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 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 proper motion of 0.2 arcsec yr–1 (V ⊥ ≈ 130d 130 km s–1), in the south-southeast direction.