Recent torque reversal of 4U 1907+09

İnam, S. Ç.
Şahiner, Ş.
Baykal, Altan
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.

Citation Formats
S. Ç. İnam, Ş. Şahiner, and A. Baykal, “Recent torque reversal of 4U 1907+09,” Monthly Notices of the Royal Astronomical Society, vol. 395, no. 2, pp. 1015–1020, 2009, Accessed: 00, 2020. [Online]. Available: