  It is well known that the equation of state (EoS) of compact objects like
neutron and quark stars is not determined despite there are several
sophisticated models to describe it. From the electromagnetic observations,
summarized in \cite{Lattimer01}, and the recent observation of gravitational
waves from binary neutron star inspiral GW170817 \cite{Abbott2017_etal} and
GW190425 \cite{Abbott2019}, it is possible to make an estimation of the range
of masses and so constraint the mass of the neutron and quark stars,
determining not only the best approximation for the EoS, but which kind of
stars we would be observing. In this paper we explore several configurations of
neutron stars assuming a simple polytropic equation of state, using a single
layer model without crust. In particular, when the EoS depends on the mass rest
density, $p=K \rho_{0}^{\Gamma}$, and when it depends on the energy density
$p=K \rho^{\Gamma}$, considerable differences in the mass-radius relationships
are found. On the other hand, we also explore quark stars models using the MIT
bag EoS for different values of the vacuum energy density $B$.
