Investigating shadow images and rings of the charged Horndeski black hole illuminated by various thin accretions

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In this paper, we investigate the shadows and rings of the charged Horndeski black hole illuminated by accretion flow that is both geometrically and optically thin.

• We consider two types of accretion models: spherical and thin-disk accretion flow.
• We find that in both types of models, the size of the charged Horndeski black hole shadow decreases with the increase of the charge, and it decreases more slowly for the Reissner-Nordstr\"om (RN) black hole.
• In the spherical accretion flow model, we find that the increase of the charge of Horndeski black hole brightens the light ring around it, and it brightens more significantly in comparison with RN black hole.