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Paper: The Luminous Blue Variable Phase — do Low Metallicity Stars go through it?
Volume: 353, Stellar Evolution at Low Metallicity: Mass Loss, Explosions, Cosmology
Page: 71
Authors: Weis, K.
Abstract: The most massive stars, above roughly 50 MSolar, pass an unstable phase, the Luminous Blue Variable (LBVs) phase. In this transitional phase between the main-sequence and Wolf-Rayet state, the stars loose large amounts of mass (> 10−5MSolaryr−1). As a consequence the evolution of these stars towards cooler temperatures is stalled and reversed. The most massive stars seem not to enter the red supergiant phase. The coolest location of these stars in the Hertzsprung- Russell Diagram marks the vertical part of the empirical Humphreys-Davidson limit (HDL). The question is whether stars with lower metallicities go through the LBV phase, and if so is there a limit in metallicity above or below which stars do not enter an LBV phase. Observations of local galaxies with a slightly lower metallicity show that LBVs are present but given the still small number of LBVs known, a more extended study is needed to fully answer this question. So far the SMC and NGC 2366 are galaxies with the lowest and M31 and M101 are the ones with the highest metallicities in which LBVs are found.
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