Photon limit of an eclipse difference spectrum
= Photon limit of an eclipse difference spectrum
For a fractional feature amplitude $d$, equal independent in- and out-of-eclipse samples with $N_\gamma$ stellar photons each have fractional difference noise approximately $\sqrt{2/N_\gamma}$. The ideal significance is $d\sqrt{N_\gamma/2}$. Correlated systematics, stellar variability and unequal exposure budgets change this result.