Issue |
A&A
Volume 431, Number 1, February III 2005
|
|
---|---|---|
Page(s) | 391 - 403 | |
Section | Astronomical instrumentation | |
DOI | https://doi.org/10.1051/0004-6361:20041453 | |
Published online | 02 February 2005 |
A simple test for periodic signals in red noise
X-Ray and Observational Astronomy Group, University of Leicester, Leicester, LE1 7RH, UK e-mail: sav2@star.le.ac.uk
Received:
11
June
2004
Accepted:
12
October
2004
We demonstrate a simple method for testing the significance of peaks
in the periodogram of red noise data. The procedure was designed to
test for spurious periodicities in X-ray light curves of active
galaxies, but can be used quite generally to test for periodic
components against a background noise spectrum assumed to have a power
law shape. The method provides a simple and fast test of the
significance of candidate periodic signals in short, well-sampled time
series such as those obtained from XMM-Newton observations of Seyfert
galaxies, without the need for Monte Carlo simulations.
A full account is made of the number of trials and the
uncertainties inherent to the model fitting. Ignoring
these subtle effects can lead to substantially overestimated
significances. These difficulties motivate us to
demand high standards of detection (minimum per cent confidence) for
periodicities in sources that normally show red noise spectra.
The method also provides a simple means to estimate the power spectral index, which may
be an interesting parameter itself, regardless of the presence/absence of
periodicities.
Key words: methods: data analysis / methods: statistical / X-rays: general / X-rays: galaxies
© ESO, 2005
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