2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/6321This chapter for the new CUP book "Compact Stellar Sources" reviews the state of work on multi-wavelength observations of high mass and low mass X-ray binaries. Both neutron star and black hole systems are considered for this work.52 pages. To appear in "Compact Stellar X-ray Sources", eds. W.H.G. Lewin and M. van der Klis. This final text contains significant revisions throughout in response to many comments on the first draftAstrophysicstext