Maximal curves from subcovers of the GK-curve

For every q=n3 with n a prime power greater than 2, the GK-curve is an Fqjavax.xml.bind.JAXBElement@65481bd0-maximal curve that is not Fqjavax.xml.bind.JAXBElement@5a5eaa49-covered by the Hermitian curve. In this paper some Galois subcovers of the GK curve are investigated. Infinitely many examples of maximal curves that cannot be Galois covered by the Hermitian curve are obtained. We also describe explicit equations for some families of quotient curves of the GK-curve. In several cases, such curves provide new values in the spectrum of genera of Fqjavax.xml.bind.JAXBElement@4cf3c39c-maximal curves.