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David W. Hogg 1,2, Ivan K. Baldry 3, Michael R. Blanton 1 and Daniel J. Eisenstein 4

Abstract. The K correction "corrects" for the fact that sources observed at different redshifts are, in general, compared with standards or each other at different rest-frame wavelengths. It is part of the relation between the emitted- or rest-frame absolute magnitude of a source in one broad photometric bandpass to the observed-frame apparent magnitude of the same source in another broad bandpass. This short pedagogical paper provides definitions of and equations for the K correction.

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1 Center for Cosmology and Particle Physics, Department of Physics, New York University


3 Department of Physics and Astronomy, The Johns Hopkins University

4 Steward Observatory, University of Arizona