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We report on spectroscopy of luminous red stars in the central bulge of M31. A number of these are shown to be late-type M giants similar to those in the Baade's window field of the bulge of the Milky Way. Among the M31 stars, we serendipitously discovered an exceptionally luminous M0 Ie red supergiant which has brightened by more than 5 mag in the last 2 yr. At peak brightness, this star was the most luminous red supergiant in the local group, with M_bol_ = -10.
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Rich et al. (1989) studied this question.
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