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34. UNUSUAL STELLAR SPECTRA III: TWO EMISSION-LINE STARS

This page illustrates two unrelated emission-line stars. The first is the famous "Blaze Star", T CrB, a recurrent nova. This star consists of a cool (as indicated by the presence of TiO bands in the spectrum) component in a binary system with a white dwarf. Gas from the cool component, which fills its Roche lobe, falls onto an accretion disk around the white dwarf. The emission lines are due to hot hydrogen gas in this accretion disk. Material from this disk is accreted onto the surface of the white dwarf. Eventually, this material detonates, producing a dramatic brightening of the system. The second star is a proto-type of the B[e] stars, B-type stars which show forbidden lines in emission. The B[e] stars represent a number of evolutionary states, including supergiants, pre-main sequence stars, compact planetary nebulae and symbiotic stars. The exact nature of HD 45677, illustrated here, is not yet known.

Figure 33

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