{\frac{C_\odot P_{\gamma}}{10^{21}~{\rm s}^{-1}}}.
\label{flux}\end{aligned}$$

This equation is correct if the particles that produce the final photons are highly boosted along the radial direction of the Sun, and should be modified by another factor of $1/2$ if those particles travel very slowly and emit photons isotropically as the Sun is effectively opaque and photons emitted on the back side of the Sun are reabsorbed. We are only interested in the former case in the current discussion. The master formula (\[flux\]) suggests that observable gamma ray fluxes are indeed possible, provided that $P_\gamma$ is not too small. In conventional neutralino-like WIMP scenarios, this probability is in fact negligible, as the only practical way of producing gamma rays is via high-energy neutrinos interacting with the outer layer of the solar material[^1], and in this case the probability $P_\gamma$ is very small. In contrast, secluded WIMPs offer the possibility of maximizing $P_\gamma$, which arises as the product of: (i) the probability $P_{\rm out}$ that the mediator particle decays outside the solar radius; (ii) the probability ${\rm Br}_{\gamma}$ of producing a gamma quantum in the decay of the mediator; and (iii) the probability ${\rm Br}_{V}$ of producing the mediator particle in the annihilation process: P\_= 