# Are Weierstrass points algebraic

Let $X$ be a compact connected Riemann surface of genus $g>0$.

Suppose that $X$ can be defined over a number field (as an algebraic curve). Then, is it clear that each Weierstrass point of $X$ is algebraic?

• Yes it is clear. – Felipe Voloch Oct 9 '11 at 13:36

Edit: as pointed out by Felipe below, what used to be here was sort of wrong-headed, but I can't delete this answer since it has already been accepted. Anyway you should do what he says: the divisor of all Weierstrass points counted with weights is defined by the vanishing of the Wronskian determinant of a basis of the space of $1$-forms on $X$. This divisor is then manifestly defined over $k$ and so all the Weierstrass points are defined over a finite extension.