PSR B1929+10 revisited in X-rays

We performed timing and spectral analyses for PSR B1929+10, one of the oldest (~10⁷ years) of the ordinary pulsars detected in X-rays, using archival ROSAT, ASCA and RXTE data. Pulsed emission was detected at a more than five sigma level for the combined ROSAT PSPC-B and previously unpublished HRI data. Our pulse profile is in agreement with that obtained by Yancopoulos et al. (1994, ApJ, 429, 832, ROSAT PSPC-B) but now with better statistics. The pulsed fraction in the ROSAT X-ray band is 0.25 ± 0.04. The pulsed signal has also been detected in the ASCA GIS data (0.5-5 keV) with a similar pulsed fraction of 0.36 ± 0.11. No significant timing signal is found in the RXTE PCA data (>2~keV). We found that the combined ROSAT PSPC-B and ASCA GIS spectrum can satisfactorily be described by a power-law as well as by a double black-body model but not by a single black-body model or black-body plus power law model. Fitting the combined ROSAT/ASCA 0.1-10 keV spectrum by a power-law model we obtain a photon index α of 2.54 ± 0.12 and a neutral hydrogen column density N_H towards the source of 9.8_-1.0^+1.4 × 10²⁰ cm^-2. For a double black-body fit our results are T₁ = 2.0_-0.05^+0.05 × 10⁶~K, T₂ = 6.9_-0.35^+0.23 × 10⁶ K and N_H = 4.4_-1.1^+2.1 × 10²⁰ cm^-2. In both cases the derived value of N_H is higher than that adopted in earlier works, but our result is fully consistent with the larger distance estimate of 331 ± 10 pc from parallax measurements combined with the hydrogen distribution measurements in the direction to the pulsar.