BL Boötis
BL Boötis (abbreviated to BL Boo) is a pulsating star in the constellation Boötes. It is the prototype of a class of anomalous Cepheids which is intermediate in the H-R diagram between the type I classical Cepheids and the type II Cepheids. It varies from magnitude 14.45 to 15.10 over 0.82 days. It is located 4 arcminutes from the centre of (and assumed to be a member star of) the globular cluster NGC 5466. Its variability was first noted in 1961 by Russian astronomer Nikolaĭ Efimovich Kurochkin, who gave it the variable star designation BL Boötis. However, he thought it was an eclipsing binary. It was subsequently thought to be an RR Lyrae variable by T.I. Gryzunova in 1971. Robert Zinn confirmed it was a member of the globular cluster and found it was too blue to be an RR Lyrae variable. He gave it the name V19 within the cluster. He calculated its solar mass, mass to be around 1.56 times and its luminosity to be around 278 times that of the Sun; its absolute magnitu ...
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