Relativistic accretion flow in a generic class of spherically symmetric static spacetimes

We investigate the properties of low angular momentum, inviscid, advective accretion flows in a generic static and spherically symmetric spacetime that incorporates higher-order corrections up to the fourth order in $1/r$. Employing this metric, we self-consistently solve the relativistic hydrodynamical equations and obtain the family of global transonic accretion solutions (O, A, W and I-types) by means of the spacetime parameters ($δ$, $η$, $β$) and the flow parameters (specific energy E and angular momentum $λ$). Our analysis reveals that the accretion flow possesses either single or multiple critical points depending on these input parameters. We delineate the regions of the $δ-λ$ and λ-E parameter spaces that admits solutions with multiple critical points and demonstrate how these regions evolve with increasing spacetime parameter $δ$. Furthermore, while connecting the spacetime geometry with observable signatures, we compute the spectral energy distribution (SED) from thermal bremsstrahlung emission and observe that increasing $δ$ enhances the SED relative to the Schwarzschild case. Finally, we find that global transonic solutions harbouring inner critical points (I-types) yields more luminous power than those with only outer critical points (O and A types).