Is there a common notation for characteristic subgroups?

Question

There is a common notation in group theory for normal subgroups. Also there is a notation for subnormal subgroups. But quite often we deal with characteristic subgroups. So, my question

Is there a common notation for characteristic subgroups? And if there is no common notation, is this a good idea to denote a characteristic subgroup $H$ of group $G$ in the following manner $H \operatorname{char} G$?

Answer 1

I have seen $N\triangleleft G$ for normal subgroups and $N\blacktriangleleft G$ for characteristic subgroups. This also makes clear that a characteristic subgroup is normal.

Answer 2

There is no common notation for this subgroup, in the sense, not all algebra text has a common notation. However, some authors use H char G to denote H is the characteristic subgroup of G. For example, Dummit and Foote use this notation. Also from the comment, Rotman use this notation. So from now on, use this notation. There's no problem!