No Time for Dead Time: Timing Analysis of Bright Black Hole Binaries with NuSTAR

M. Bachetti, F.A. Harrison, R. Cook, J. Tomsick, C. Schmid, B.W. Grefenstette, D. Barret, S.E. Boggs, F.E. Christensen, W.W. Craig, A.C. Fabian, F. Fürst, P. Gandhi, C.J. Hailey, E. Kara, Thomas Maccarone, J.M. Miller, K. Pottschmidt, D. Stern, P. UttleyD.J. Walton, J. Wilms, W.W. Zhang

Research output: Contribution to journalArticle

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 languageEnglish
Pages (from-to)109
JournalThe Astrophysical Journal
StatePublished - Feb 2015

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    Bachetti, M., Harrison, F. A., Cook, R., Tomsick, J., Schmid, C., Grefenstette, B. W., Barret, D., Boggs, S. E., Christensen, F. E., Craig, W. W., Fabian, A. C., Fürst, F., Gandhi, P., Hailey, C. J., Kara, E., Maccarone, T., Miller, J. M., Pottschmidt, K., Stern, D., ... Zhang, W. W. (2015). No Time for Dead Time: Timing Analysis of Bright Black Hole Binaries with NuSTAR. The Astrophysical Journal, 109.