2,154 research outputs found
Temporal Variations of Strength and Location of the South Atlantic Anomaly as Measured by RXTE
The evolution of the particle background at an altitude of ~540 km during the
time interval between 1996 and 2007 is studied using the particle monitor of
the High Energy X-ray Timing Experiment on board NASA's Rossi X-ray Timing
Explorer. A special emphasis of this study is the location and strength of the
South Atlantic Anomaly (SAA). The size and strength of the SAA are
anti-correlated with the the 10.7 cm radio flux of the Sun, which leads the SAA
strength by ~1 year reflecting variations in solar heating of the upper
atmosphere. The location of the SAA is also found to drift westwards with an
average drift rate of about 0.3 deg/yr following the drift of the geomagnetic
field configuration. Superimposed to this drift rate are irregularities, where
the SAA suddenly moves eastwards and where furthermore the speed of the drift
changes. The most prominent of these irregularities is found in the second
quarter of 2003 and another event took place in 1999. We suggest that these
events are previously unrecognized manifestations of the geomagnetic jerks of
the Earth's magnetic field.Comment: 21 pages, 11 figures, accepted for publication in Earth and Planetary
Science Letter
Reflection and noise in the low spectral state of GX339-4
We analyze RXTE/PCA observations of GX339-4 in the low spectral state from
1996--1997 and show that the pattern of its spectral and temporal variability
is nearly identical to that of Cyg X-1. In particular, a tight correlation
exists between the QPO centroid frequency and the spectral parameters. An
increase of the QPO centroid frequency is accompanied with an increase of the
amplitude of the reflected component and a steepening the slope of the
underlying power law. Fourier frequency resolved spectral analysis showed, that
the variability of the reflected component at frequencies higher than ~1-10 Hz
is suppressed in comparison with that of the primary emission.Comment: 4 pages, 4 figures. Accepted in Astronomy and Astrophysics Main
Journa
Multiple Cyclotron Lines in the Spectrum of 4U 0115+63
We report phase resolved spectroscopy of the transient accreting pulsar,
4U0115+63. For the first time, more than two cylotron resonance scattering
features are detected in the spectrum of an X-ray pulsar. The shape of the
fundamental line appears to be complex, and this is in agreement with
predictions of Monte-Carlo models. As in other pulsars, the line energies and
optical depths are strong functions of pulse phase. One possible model for this
is an offset of the dipole of the neutron star magnetic field.Comment: 5 pages. To appear in "Proceedings of the 5th Compton Symposium
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