Recent torque reversal of 4U 1907+09


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İNAM S. Ç. , Sahiner S., BAYKAL A.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol.395, no.2, pp.1015-1020, 2009 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 395 Issue: 2
  • Publication Date: 2009
  • Doi Number: 10.1111/j.1365-2966.2009.14596.x
  • Title of Journal : MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
  • Page Numbers: pp.1015-1020
  • Keywords: accretion, accretion discs, stars: neutron, pulsars: individual: 4U 1907+09, X-rays: binaries, SPIN-UP/SPIN-DOWN, X-RAY PULSARS, THREADED ACCRETION DISK, MAGNETIC-FIELDS, TIMING-EXPLORER, 4U-1907+09, EMISSION, SPECTROSCOPY, COMPANION, SPECTRUM

Abstract

We present timing and spectral analysis of RXTE-PCA ( Proportional Counter Array) observations of the accretion powered pulsar 4U 1907+09 between 2007 June and 2008 August. 4U 1907+09 had been in a spin-down episode with a spin-down rate of -3.54 x 10(-14) Hz s(-1) before 1999. From RXTE observations after 2001 March, the source showed a similar to 60 per cent decrease in spin-down magnitude, and INTEGRAL observations after 2003 March showed that source started to spin-up. We found that the source recently entered into a new spin-down episode with a spin-down rate of -3.59 x 10(-14) Hz s(-1). This spin-down rate is pretty close to the previous long-term spin-down rate of the source measured before 1999. From the spectral analysis, we showed that hydrogen column density varies with the orbital phase.