  In this paper we investigate analytic properties of sextet polynomials of
hexagonal systems. For the pyrene chains, we show that zeros of the sextet
polynomials $P_n(x)$ are real, located in the open interval
$(-3-2\sqrt{2},-3+2\sqrt{2})$ and dense in the corresponding closed interval.
We also show that coefficients of $P_n(x)$ are symmetric, unimodal,
log-concave, and asymptotically normal. For general hexagonal systems, we show
that real zeros of all sextet polynomials are dense in the interval
$(-\infty,0]$, and conjecture that every sextet polynomial has log-concave
coefficients.
