RR Lyrae in PS1

Nina's working out lots of things about how to do QSO variability right.

Questions arises what would need to be changed to apply same formalism to RR Lyrae.

If one uses Gaussian process (Hogg's advice), then one needs to specify the appropriate
covariance function.

Hogg recommends the covariance corresponding to a damped oscillator.

HWR's thoughts:

Take a covariance that corresponds to range of periods of near-sinusoidal oscillation.
It will look periodic for Dt's corresponding to a few periods, but look like
white noise expectations for long time-intervals.
That way, for short time intervals it matches well, but one is not stuck with the cumbersome
period matching over very long periods.

For thinking about how to write down a suitable GP covariance function, I found it useful
to do a lot of staring at the plots from Sesar's 2010 paper (his Fig 9)

It nicely shows:

• the level of lightcurve asymmetry: slow fall, very rapid rise
• the fact that the g-r color changes drastically but the i-z not at all (just Teff?)