ET Andromedae

Lore & Background

ET Andromedae was first suggested to be photometrically variable in 1953 by Sanford S. Provin, based on observations at Yerkes Observatory. Variability was later confirmed from Lowell Observatory measurements published by Karl D. Rakos in 1962. The star is classified as an Alpha2 Canum Venaticorum variable with a period of 1.618875 days. The visible component is a well-studied magnetic chemically peculiar star with a stellar classification of A0 Vp SiSr, indicating unusual abundances of silicon and strontium in its spectrum. It has a magnetic field with an average surface value of 3.2 kT, and the abundance of silicon varies depending on the viewing angle. Variations in radial velocity reveal it is a single-lined spectroscopic binary system with an orbital period of 48.3 days and an eccentricity of 0.50. The a sin i value for the primary is 14.8 Gm (0.099 AU), where i is the unknown orbital inclination.

Reader's Guide

ET Andromedae holds significance as a binary system that combines spectroscopic binary characteristics with magnetic chemically peculiar variability. Its classification as an Alpha2 Canum Venaticorum variable, with a precisely measured period of 1.618875 days, makes it a valuable object for studying the interplay between stellar rotation, magnetic fields, and chemical abundance anomalies. The detection of variable silicon abundance with viewing angle provides insight into surface inhomogeneities on magnetic stars. The system's orbital elements, including a 48.3-day period and eccentricity of 0.50, contribute to understanding binary dynamics among chemically peculiar stars. The distance of 602 light years, derived from a parallax of 5.42 mas, places it within a range accessible for detailed spectroscopic and photometric follow-up. The history of its variability discovery, from Provin's initial suggestion in 1953 to Rakos's confirmation in 1962, illustrates the observational efforts at Yerkes and Lowell Observatories that established its variable nature.

Did You Know?

• ET Andromedae has an apparent visual magnitude of 6.48, at the nominal limit for naked-eye visibility.
• The star's magnetic field has an average surface value of 3.2 kT.
• Its orbital eccentricity is 0.50, with a period of 48.3 days.
• The variability period of this Alpha2 Canum Venaticorum variable is 1.618875 days.