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

Abstract

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 $0\leqslant \frac{r_2}{M}\leqslant0.4$, 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*.