  Einstein-Maxwell dilaton-axion (EMDA) gravity provides a simple framework to
investigate the signatures of string theory. The axion and the dilaton fields
arising in EMDA gravity have important implications in inflationary cosmology
and in addressing the late time acceleration of the universe. It is therefore
instructive to explore the implications of such a model in explaining the
astrophysical observations. In this work we explore the role of EMDA gravity in
explaining the observed shadows of black holes (M87* and Sgr A*) released by
the Event Horizon Telescope (EHT) collaboration. The Kerr-Sen metric represents
the exact, stationary and axisymmetric black hole solution of EMDA gravity.
Such a black hole is characterized by the angular momentum $a$ acquired from
the axionic field and the dilatonic charge $r_2$ arising from string
compactifications. We study the role of spin and the dilaton charge in
modifying the shape and size of the black hole shadow. We note that black holes
with larger dilaton charge cast a smaller shadow. We investigate the
consequences of such a result in addressing the EHT observations of M87* and
Sgr A*. Our analysis reveals that the shadow of M87* exhibits a preference
towards the Kerr scenario. However, when 10% offset in the shadow diameter is
considered, $0.1\lesssim r_2\lesssim 0.3$ is observationally favored within
1-$\sigma$. The shadow of Sgr A* on the other hand shows a preference towards
the Kerr-Sen scenario since the central value of its shadow can be better
explained by a non-zero dilaton charge $0.1 \lesssim r_2 \lesssim 0.4$.
However, when the 1-$\sigma$ interval is considered the Kerr scenario is
included. We discuss the implications of our results.
