  Let $S$ be a $*$-semigroup and let $a,w,v\in S$. The initial goal of this
work is to introduce two new classes of generalized inverses, called the
$w$-core inverse and the dual $v$-core inverse in $S$. An element $a\in S$ is
$w$-core invertible if there exists some $x\in S$ such that $awx^2=x$, $xawa=a$
and $(awx)^*=awx$. Such an $x$ is called a $w$-core inverse of $a$. It is shown
that the core inverse and the pseudo core inverse can be characterized in terms
of the $w$-core inverse. Several characterizations of the $w$-core inverse of
$a$ are derived, and the expression is given by the inverse of $w$ along $a$
and $\{1,3\}$-inverses of $a$ in $S$. Also, the connections between the
$w$-core inverse and other generalized inverses are given. In particular, when
$S$ is a $*$-ring, the existence criterion for the $w$-core inverse is given by
units. The dual $v$-core inverse of $a$ is defined by the existence of $y\in S$
satisfying $y^2va=y$, $avay=a$ and $(yva)^*=yva$. Dual results for the dual
$v$-core inverse also hold.
