2016MNRAS.461.3145V -
Mon. Not. R. Astron. Soc., 461, 3145-3152 (2016/September-3)
False periodicities in quasar time-domain surveys.
VAUGHAN S., UTTLEY P., MARKOWITZ A.G., HUPPENKOTHEN D., MIDDLETON M.J., ALSTON W.N., SCARGLE J.D. and FARR W.M.
Abstract (from CDS):
There have recently been several reports of apparently periodic variations in the light curves of quasars, e.g. PG 1302-102 by Graham et al. Any quasar showing periodic oscillations in brightness would be a strong candidate to be a close binary supermassive black hole and, in turn, a candidate for gravitational wave studies. However, normal quasars - powered by accretion on to a single, supermassive black hole - usually show stochastic variability over a wide range of time-scales. It is therefore important to carefully assess the methods for identifying periodic candidates from among a population dominated by stochastic variability. Using a Bayesian analysis of the light curve of PG 1302-102, we find that a simple stochastic process is preferred over a sinusoidal variation. We then discuss some of the problems one encounters when searching for rare, strictly periodic signals among a large number of irregularly sampled, stochastic time series, and use simulations of quasar light curves to illustrate these points. From a few thousand simulations of steep spectrum ('red noise') stochastic processes, we find many simulations that display few-cycle periodicity like that seen in PG 1302-102. We emphasize the importance of calibrating the false positive rate when the number of targets in a search is very large.
Abstract Copyright:
© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
methods: data analysis - methods: statistical - quasars: general - quasars: general
CDS comments:
In p. 3146 : RE J1034-396 is a misprint for RE J1034+396.
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