On the Fujita exponent for a nonlinear parabolic equation with a forcing term

The purpose of this work is to analyze the blow-up of solutions of the nonlinear parabolic equation $$u_t-\Delta u=|x|^{\alpha}|u|^{p}+{\mathtt a}(t)\textbf{w}(x) \ \quad\mbox{for } (t,x)\in(0,\infty)\times\mathbb{R}^{N},$$ where $p>1$, $\alpha\in\mathbb{R}$ and ${\mathtt a}$, $\textbf{w}$ are suitable given functions. We improve earlier results by considering a wide class of functions ${\mathtt a}(t)$.