Thin accretion disk and shadow of Kerr–Sen black hole in Einstein–Maxwell-dilaton–axion gravity

We investigate the thin disk and shadow of Kerr–Sen black hole in Einstein–Maxwell-dilaton–axion gravity. The results reveal that as the dilaton parameter $r_2$ increase, the energy flux, the radiation temperature, the spectra luminosity, and the radiative efficiency of the disk all increase. By narrowing down the dilaton parameter range to $0⩽\frac{r_2}{M}⩽0.4$, we discover that in the high-frequency region, the Kerr–Sen black hole demonstrates higher energy output compared to the Kerr black hole. We also investigated the shadow of Kerr–Sen black hole in a uniform plasma environment. For fixed inclination angle, dilaton, and spin parameters, the shadow increases as the homogeneous plasma parameter $k$ increases. Conversely, when $k$ and $a$ are fixed, an increase in $r_2$ leads to a decrease in the shadow. Finally, we constrain the model parameters with observational data from M87* and Sgr A*.