Testing microvariability in quasar differential light curves using
  several field stars
  Microvariability consists in small time scale variations of low amplitude in
the photometric light curves of quasars, and represents an important tool to
investigate their inner core. Detection of quasar microvariations is
challenging for their non-periodicity, as well as the need for high monitoring
frequency and high signal-to-noise ratio. Statistical tests developed for the
analysis of quasar differential light curves usually show either low power or
low reliability, or both. In this paper we compare two statistical procedures
that include several stars to perform tests with enhanced power and high
reliability. We perform light curve simulations of variable quasars and
non-variable stars, and analyze them with statistical procedures developed from
the F-test and the analysis of variance. The results show a large improvement
in the power of both statistical probes, and a larger reliability, when several
stars are included in the analysis. The results from the simulations agree with
those obtained from observations of real quasars. The high power and high
reliability of the tests discussed in this paper improve the results that can
be obtained from short and long time scale variability studies. These
techniques are not limited to quasar variability; on the contrary, they can be
easily implemented to other sources such as variable stars. Their applications
to future research and to the analysis of large field photometric monitoring
archives can reveal new variable sources.
