Xtronomy (or Xtrophysics) is the physics or EXTREME astronomy/astrophysics and, if you want Cosmology (Xosmology could be used for the latters). It includes the following:

1. X-ray astronomy.
2. Gamma ray astronomy.
3. Cosmic ray astronomy.
4. Neutrino astronomy.
5. Gravitational wave astronomy.
6. Possible X-particle astronomy (like axions, monopoles, dark matter particles, gravitons, etcetera).