They were first recognized as being distinct from classical Cepheids by
Walter Baade in 1942, in a study of Cepheids in the
Andromeda Galaxy that proposed that stars in that galaxy were of two populations.[4]
^Soszyński, I.; Udalski, A.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Wyrzykowski, Ł.; Szewczyk, O.; Ulaczyk, K.; Poleski, R. (2008). "The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. II.Type II Cepheids and Anomalous Cepheids in the Large Magellanic Cloud". Acta Astronomica. 58: 293.
arXiv:0811.3636.
Bibcode:
2008AcA....58..293S.
^Webb, Stephen (1999). Measuring the Universe: The Cosmological Distance Ladder. Springer.
External links
AAVSO Variable Star of the Month. W Virginis: Spring 2003
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