double-lined binary

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A spectroscopic binary in which both components have similar brightnesses; sometimes also called an SB2 system. During certain phases of the orbit the spectral lines appear doubled because of the components' differing radial velocities. The effect is particularly noticeable if the spectral types of the two components are similar. See also Composite-Spectrum Binary; Single-Lined Binary.

Subjects: Astronomy and Astrophysics.

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