Measurements of tt‾+X using the ATLAS detector

The large centre-of-mass energy available at the LHC proton-proton collider allows for copious production of top-quark pairs in association with other final state particles at high transverse momentum. Results on the top-quark pair production in association with W and Z bosons at both 8 and 13 TeV are presented as well as the measurement of the cross section for production with an associated isolated photon at 7 TeV. The ATLAS experiment has measured several final state observables that are sensitive to additional radiation in top anti-top quark final states. Analyses probing the top-quark pair production with additional QCD radiation include the multiplicity of jets for various transverse momentum thresholds in the 13 TeV data. These measurements are compared to some of the most recent Monte Carlo event generators based on NLO QCD or LO multi-leg matrix element calculations.