# Models Used in Existing Hydrocodes ## gasoline2/ChaNGa Feedback from core collapse SN is governed based on a choice of IMF and stellar lifetimes derived from Equation 3 of [Raiteri 1996](https://ui.adsabs.harvard.edu/abs/1996A%26A...315..105R/abstract). These lifetimes depend on the mass *M* and metallicity *Z* of the star (in solar units) and are given by: $$t_*(\mathrm{yr}) = a_0(Z) + a_1(Z)\log(M) + a_2(Z)(\log(M))^2$$ With the metallicity-dependent coefficients *a**i*(*Z*) given by: $$\begin{aligned} a_0(Z) &= 10.13 + 0.07547\log(Z) - 0.008084\left(\log(Z)\right)^2 \\ a_1(Z) &= -4.424 - 0.7939\log(Z) - 0.1187\left(\log(Z)\right)^2 \\ a_2(Z) &= 1.262 + 0.3385\log(Z) + 0.05417\left(\log(Z)\right)^2 \end{aligned}$$