On the zeros of polynomials generated by rational functions with a   hyperbolic polynomial type denominator
  This paper investigates the location of the zeros of a sequence of polynomials generated by a rational function with a denominator of the form $G(z,t)=P(t)+zt^{r}$, where the zeros of $P$ are positive and real. We show that every member of a family of such generating functions - parametrized by the degree of $P$ and $r$ - gives rise to a sequence of polynomials $\{H_{m}(z)\}_{m=0}^{\infty}$ that is eventually hyperbolic. Moreover, when $P(0)>0$ the real zeros of the polynomials $H_{m}(z)$ form a dense subset of an interval $I\subset\mathbb{R}^{+}$, whose length depends on the particular values of the parameters in the generating function. 
Tam\'as Forg\'acs and Khang Tran
math.CV