Jonathan I. Katz has written:

'High energy astrophysics' -- subject(s): Nuclear astrophysics, Stars

B.S.P Shen has written:

'High-energy nuclear reactions in astrophysics' -- subject(s): Astrophysics, Nuclear reactions

M. S. Longair has written:

'High energy astrophysics'

Donald H. Perkins has written:

'Introduction to high energy physics' -- subject(s): Particles (Nuclear physics)

'Particle astrophysics' -- subject(s): Particles (Nuclear physics), Nuclear astrophysics

Yes, theoretical astrophysics is a branch of astrophysics.