ET Andromedae

ET Andromedae is a binary star system star in the northern constellation of Andromeda. It has an apparent visual magnitude of 6.48, placing it at the nominal limit for visibility with the naked eye. The distance to this system can be estimated from its annual parallax shift of $−0.037$, which yields a value of 602 light years.

Variations in the radial velocity of this star suggest it is a single-lined spectroscopic binary system. This yields orbital elements with a period of 48.3 days and an eccentricity of 0.50. The a sin i value for the primary is 14.8 Gm, where a is the semimajor axis and i is the (unknown) orbital inclination.

The visible component is a well-studied magnetic chemically peculiar star with a stellar classification of A0 Vp SiSr. The SiSr notation indicates unusual abundances of silicon and strontium in the spectrum. It has a magnetic field with an average surface value of $−0.30$. The abundance of silicon varies depending on the viewing angle. The star is an Alpha2 Canum Venaticorum variable with a period of 1.618875 days.