Optical Flickering and Shot Noise in AM Her Systems

  • S. Larsson
  • B. Larsson
Conference paper
Part of the Astrophysics and Space Science Library book series (ASSL, volume 208)


The emission from AM Her systems show a variety of time-variable phenomena, including flickering with a typical power spectrum slope of -1 to -2. The optical flickering is usually modeled as, or assumed to be, a shot noise process with many overlapping simultaneous shots. Panek (1980) found that, for AM Her, a consistent model could be constructed with randomly occurring 70…90s rectangular shots. The power spectrum had a v -2 shape above 0.02 Hz as expected, although it is not clear whether a break in the slope of the power spectrum was actually seen around 0.01 Hz. There are many additional reports in the literature of ‘characteristic time-scales’ on the order of tens of seconds. However we are not aware of any case where the reported time-scale has been supported by e.g. a break in the power density spectrum. It is easy to show that the usual method of estimating a ‘characteristic time-scale’ from the auto correlation function of de-trended data will suggest such a characteristic time-scale even if none is present in the original time series. The evidence for shot noise in AM Her light curves therefore needs a re-examination. In this paper we give a short summary of our analysis of optical flickering in V834 Cen, based on high speed photometry obtained at ESO in 1987. Details will be reported elsewhere.


Power Spectrum Light Curve Shot Noise Power Density Spectrum Original Time Series 
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  1. Panek, R., 1980, Ap. J., 241, 107ADSCrossRefGoogle Scholar

Copyright information

© Kluwer Academic Publishers 1996

Authors and Affiliations

  • S. Larsson
    • 1
  • B. Larsson
    • 1
  1. 1.Stockholm ObservatorySaltsjöbadenSweden

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