  In the present work we study non-rotating dark stars in $f(R)$ modified
theory of gravity. In particular, we have considered bosonic self-interacting
dark matter modelled inside the star as a Bose-Einstein condensate, while as
far as the modified theory of gravity is concerned we have assumed
Starobinsky's model $R+aR^2$. We solve the generalized structure equations
numerically, and we obtain the mass-to-ratio relation for several different
values of the parameter $a$, and for two different dark matter
equation-of-states. Our results show that the dark matter stars become more
compact in the R-squared gravity compared to General Relativity, while at the
same time the highest star mass is slightly increased in the modified
gravitational theory. The numerical value of the highest star mass for each
case has been reported.
