Astronomy and Astrophysics – Astrophysics
Scientific paper
2001-09-20
Astrophys.J. 576 (2002) 381-390
Astronomy and Astrophysics
Astrophysics
26 pages, 11 figures included, accepted for publication in ApJ, analysis of torque noise power density spectra is revised from
Scientific paper
10.1086/341536
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 power spectrum of each source is very red (power-law slope ~-3.5). The torque noise power levels are consistent with some accreting systems on time scales of ~1 year, yet the full power spectrum is much steeper in frequency than any known accreting source. To the best of our knowledge, torque noise power spectra with a comparably steep frequency dependence have only been seen in young, glitching radio pulsars (e.g. Vela). The observed changes in spin-down rate do not correlate with burst activity, therefore, the physical mechanisms behind each phenomenon are also likely unrelated. Within the context of the magnetar model, seismic activity cannot account for both the bursts and the long-term torque changes unless the seismically active regions are decoupled from one another.
Finger Mark H.
Gougus Ersin
Hurley Kevin
Kouveliotou Chryssa
Markwardt Craig B.
No associations
LandOfFree
Large Torque Variations in Two Soft Gamma Repeaters does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Large Torque Variations in Two Soft Gamma Repeaters, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Large Torque Variations in Two Soft Gamma Repeaters will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-722776