Differences between the two anomalous X-ray pulsars: variations in the spin-down rate of 1E 1048.1-5937 and an extended interval of quiet spin-down in 1E 2259+586


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Baykal A., Strohmayer T., Swank J., Alpar M., Stark M.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol.319, no.1, pp.205-208, 2000 (Peer-Reviewed Journal) identifier identifier

  • Publication Type: Article / Article
  • Volume: 319 Issue: 1
  • Publication Date: 2000
  • Doi Number: 10.1046/j.1365-8711.2000.03845.x
  • Journal Name: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Page Numbers: pp.205-208

Abstract

We analysed the Rossi X-ray Timing Explorer (RXTE) archival data of 1E 1048.1-5937 covering a time-span of more than one year. The spin-down rate of this source decreases by similar to 30 per cent during the observation. We could not resolve the X-ray flux variations because of contamination by eta Carinae. We find that the level of pulse frequency fluctuations of 1E 1048.1-5937 is consistent with typical noise levels of accretion-powered pulsars. Recent RXTE observations of 1E 2259+586 have shown a constant spin-down with a very low upper limit on timing noise. We used the RXTE archival X-ray observations of 1E 2259+586 to show that the intrinsic X-ray luminosity times-series is also stable, with an rms fractional variation of less than 15 per cent. The source could have been in a quiet phase of accretion with a constant X-ray luminosity and spin-down rate.