Leavitt Variables: The Brightest Cepheids Variables and their Implications for the Distance Scale

Abstract Two low-amplitude variable supergiants in the Large Magellanic Cloud, S65-08 and S65-48 are each found to have periods of approximately 250 days. The cfptical data suggest that these stars are high-luminosity cepheid variables falling more than one magnitude brighter than any other known Cepheids in the LMC. Confirmation of the cepheid nature of these stars comes from their H-band magnitudes which place them accurately on a simple linear extrapolation of the narrower infrared Period-Luminosity relation. So it appears that the cepheid Period-Luminosity relation extends up to M v ~ -8.5. To honour the astronomer who discovered the first of these highest-liminosity Cepheids, we have sub-classified the variables with log P > 1.8 as being “Leavitt variables”. As soon as these long-period variables are discovered in other external galaxies, reliable distances should be possible out to (m-M) ~30.