compute_fvar#

gammapy.stats.compute_fvar(flux, flux_err, axis=0)[source]#

Calculate the fractional excess variance.

This method accesses the FLUX and FLUX_ERR columns from the lightcurve data.

The fractional excess variance Fvar, an intrinsic variability estimator, is given by:

Fvar=S2σ2¯x¯2

It is the excess variance after accounting for the measurement errors on the light curve σ. S is the variance.

It is important to note that the errors on the flux must be gaussian.

Parameters
fluxQuantity

The measured fluxes.

flux_errQuantity

The error on measured fluxes.

axisint, optional

Axis along which the excess variance is computed. Default is 0.

Returns
fvar, fvar_errndarray

Fractional excess variance.

References

Vaughan2003

“On characterizing the variability properties of X-ray light curves from active galaxies”, Vaughan et al. (2003) https://ui.adsabs.harvard.edu/abs/2003MNRAS.345.1271V