Abstract
Timing of high-count-rate sources with the NuSTAR Small Explorer Mission
requires specialized analysis techniques. NuSTAR was primarily designed
for spectroscopic observations of sources with relatively low count
rates rather than for timing analysis of bright objects. The
instrumental dead time per event is relatively long (2.5 msec) and
varies event-to-event by a few percent. The most obvious effect is a
distortion of the white noise level in the power density spectrum (PDS)
that cannot be easily modeled with standard techniques due to the
variable nature of the dead time. In this paper, we show that it is
possible to exploit the presence of two completely independent focal
planes and use the cospectrum, the real part of the cross PDS, to obtain
a good proxy of the white-noise-subtracted PDS. Thereafter, one can use
a Monte Carlo approach to estimate the remaining effects of dead time,
namely, a frequency-dependent modulation of the variance and a
frequency-independent drop of the s
Original language | English |
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Pages (from-to) | 109 |
Journal | The Astrophysical Journal |
State | Published - Feb 2015 |