Accretion flow in deformed Kerr spacetime: Spectral energy distributions from free-free emission

In this paper, we study the properties of accretion flow including its spectral features in Johannsen and Psaltis (JP) non-Kerr spacetime. In doing so, we numerically solve the governing equations that describe the flow motion around the compact objects in a general relativistic framework, where spin ($a_{k}$) and deformation parameters ($\varepsilon$) demonstrate the nature of the central source, namely black hole (BH) or naked singularity (NS). With this, we obtain all possible classes of global accretion solutions ($i. e.$, O, A, W and I-type) by varying the energy ($E$) and angular momentum ($\lambda$) of the relativistic accretion flow, and examine the role of thermal bremsstrahlung emission in studying the spectral energy distributions (SEDs) of the accretion disc. We divide the parameter space in $\lambda-E$ plane in terms of the different classes of accretion solutions for BH and NS models. We further calculate the disc luminosity ($L$) corresponding to these accretion solutions, and observe that I-type solutions yield higher $L$ and SEDs than the remaining types of solutions for both BH and NS models. For BH model, SEDs for W and I-type solutions differ significantly from the results for O and A-type solutions for low $E$ values. On the contrary, for NS model, SEDs for different accretion solutions are identical in the whole parameter space of $\lambda$ and $E$. We also examine the effect of $\varepsilon$ on the SEDs and observe that a non-Kerr BH yields higher SEDs than the usual Kerr BH. Finally, for accretion solutions of identical $E$ and $\lambda$, we compare the SEDs obtained from BH and NS models, and find that naked singularity objects produce more luminous power spectra than the black holes.