The two - component X - ray spectrum of the 6 . 4 s pulsar 1 E 1048 . 1 – 5937

ASTRONOMY AND ASTROPHYSICS The two-component X-ray spectrum of the 6.4 s pulsar 1E 1048.1–5937 Abstract. The 6.4 s X-ray pulsar 1E 1048.1–5937 was observed by BeppoSAX in 1997 May. This source belongs to the class of " anomalous " pulsars which have pulse periods in range 5–11 s, show no evidence of optical or radio counterparts , and exhibit long-term increases in pulse period. The phase-averaged 0.5–10 keV spectrum can be described by an absorbed power-law and blackbody model. The best-fit photon index is 2.5±0.2 and the blackbody temperature and radius are 0.64±0.01 keV and 0.59 ± 0.02 km (for a distance of 3 kpc), respectively. The detection of blackbody emission from this source strengthens the similarity with two of the more well studied " anomalous " pul-sars, 1E 2259+586 and 4U 0142+614. There is no evidence for any phase dependent spectral changes. The pulse period of 6.45026 ± 0.00001 s implies that 1E 1048.1–5937 continues to spin-down, but at a slower rate than obtained from the previous measurements in 1994 and 1996.