  We calculate Fourier coefficients of the net-baryon number as a function of a
purely imaginary chemical potential. The asymptotic behavior of these
coefficients is governed by the singularity structure of the QCD partition
function and thus encodes information on phase transitions. For the calculation
of the Fourier coefficients from lattice data of the Bielefeld-Parma
collaboration we use a novel Filon-type quadrature, designed for highly
oscillatory integrals. We find sensitivity to chiral scaling in a narrow
temperature interval below the Roberge-Weiss transition temperature. Scaling
fits yield reasonable values for the position of the Lee-Yang edge singularity
in the complex chemical potential plane. Our lattice data has been obtained
from simulations with (2+1)-flavors of highly improved staggered quarks (HISQ)
at imaginary chemical potential on $N_\tau=4, 6$ and $8$ lattices at physical
quark masses.
