GY Andromedae

GY Andromedae (GY And) is an α² Canum Venaticorum type binary variable star in the northern constellation Andromeda. Its brightness fluctuates in visual magnitude between 6.27^m and 6.41^m, making it a challenge to view with the naked eye even in good seeing conditions. The magnetic activity on this star shows an unusually long period of variability, cycling about once every 23 years.<ref name=aaas114_79/> Based upon parallax measurements, this star is located at a distance of about Template:Convert from the Earth.<ref name="Gaia EDR3"/>

This is classified as an Ap/Bp star, with a peculiar spectrum<ref name=aaas114_79/> showing lines of chromium and europium that change in intensity over a period matching the variability cycle, although opposite in phase.<ref name=apj160_1071/> Its most striking characteristic is the presence of the unstable element promethium in its emission spectrum. All isotopes of this element are radioactive with half lives of 17.7 years or less. The promethium in the outer envelope may be generated by the spontaneous fission of higher mass transuranic elements.<ref name=apj181_475/>

System

Based on radial velocity measurements taken at the Dominion Astrophysical Observatory between 1927 and 1935 Canadian astronomer William Edmund Harper strongly suspected that this star was a spectroscopic binary.<ref name="Harper1937"/> In 1958, American astronomer Horace W. Babcock confirmed the binary nature of the star.<ref name="Babcock1958"/> It has an orbital period of 273 days with a large eccentricity of 0.47. The two components are separated by an estimated distance of at least Template:Nowrap, or 0.25 Astronomical Units.<ref name=an299_2_81/>

External links

• Astronomie: Die Sterne - Special Stars: GY Andromedae