HR 465 returning to rare-earth-maximum phase

Abstract

HR465 is unusual among Ap stars. Its spectroscopic variability has been discussed by Wolff and Preston¹ who show that at the rare-earth-minimum phase, the sharp-lined spectrum is similar to that of many other Ap stars of the ‘magnetic sequence’. The rare-earth-maximum phase, studied Bidelman and Pyper (personal communication), was found to have an extremely high density of lanthanide rare-earth lines in addition to Hg II 3,984Å. Their observations of this phase were made in the early 1960s and because of the very long period of the star, around 22–24 yr, they have not been repeated. Until recently, the critical phase of HR465 has been unavailable. However, we report three 2.4Å mm⁻¹ spectrograms of HR465 taken at the Dominion Astrophysical Observatory (DAO) in August 1981 which show that the spectrum now very closely resembles that of the early 1960s—the rare-earth-maximum phase has returned.