Revealing δ Cephei's Secret Companion and Intriguing Past

  title={Revealing $\delta$ Cephei's Secret Companion and Intriguing Past},
  author={Richard I. Anderson and Johannes Sahlmann and Berry Holl and Laurent Eyer and Lovro Palaversa and Nami Mowlavi and Maria Suveges and Maroussia Roelens},
  journal={The Astrophysical Journal},
Classical Cepheid variable stars are crucial calibrators of the cosmic distance scale thanks to a relation between their pulsation periods and luminosities. Their archetype, {\delta} Cephei, is an important calibrator for this relation. In this paper, we show that {\delta} Cephei is a spectroscopic binary based on newly-obtained high-precision radial velocities. We combine these new data with literature data to determine the orbit, which has period 2201 days, semi-amplitude 1.5 km/s, and high… 
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