Large Torque Variations in Two Soft Gamma Repeaters

@article{Woods2002LargeTV,
  title={Large Torque Variations in Two Soft Gamma Repeaters},
  author={Peter M. Woods and Chryssa Kouveliotou and Ersin Gougus and Mark H. Finger and Jean Hebb Swank and Craig B. Markwardt and Kevin Hurley and Michiel van der Klis Nsstc and Usra and NASA-MSFC and Uah and NasaGsfc and Ucb and University of Amsterdam},
  journal={The Astrophysical Journal},
  year={2002},
  volume={576},
  pages={381-390}
}
We have monitored the pulse frequencies of the two soft gamma repeaters SGR 1806-20 and SGR 1900+14 through the beginning of year 2001 using primarily Rossi X-Ray Timing Explorer Proportional Counter Array observations. In both sources, we observe large changes in the spin-down torque up to a factor of ~4, which persist for several months. Using long-baseline phase-connected timing solutions as well as the overall frequency histories, we construct torque noise power spectra for each SGR. The… 
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