9 Cephei

9 Cephei, also known as V337 Cephei, is a variable star in the constellation Cepheus. It is visible to the naked eye.
File:V337CepLightCurve.png|thumb|left|A light curve for V337 Cephei, plotted from TESS data
In 1967, Graham Hill announced his discovery that 9 Cephei is a variable star. 9 Cephei was given the name V337 Cephei and classified as an Alpha [Cygni variable|α Cygni variable] in 1979. It varies irregularly between magnitude 4.69 and 4.78. A study of the Hipparcos satellite photometry showed an amplitude of 0.56 magnitudes, but could find no periodicity.
9 Cephei is considered to be a member of the Cepheus OB2 stellar association, a scattering of massive bright stars around a thousand parsecs away in the southern part of the constellation Cepheus.
Calculations of the physical properties of 9 Cephei vary considerably even from broadly similar observational data. Modelling using the non-LTE line-blanketed CMFGEN atmospheric code gives a temperature of 18,000 K, radius of, luminosity of, and mass of. Calculations using the FASTWIND model give a temperature of 19,200 K, radius of, luminosity of, and mass of.