F Eridani

f Eridani is a binary, or possibly a triple, star system in the equatorial constellation of Eridanus, consisting of stars HD 24071 and HD 24072. They share a single Hipparcos catalogue entry, HIP 17797, but have separate Bright Star Catalogue listings, HR 1189 and 1190. f Eridani is the Bayer designation of the pair.

f Eridani is visible to the naked eye as a single star with a magnitude of 4.25. HD 24071 has an apparent visual magnitude of 5.25 and HD 24072 a magnitude of 4.72. As of 2009, the pair had an angular separation of $4.721$ along a position angle of 216°. Both stars have an annual parallax shift $5.246$, which provides a distance estimate to the system of 173 light years. The pair are members of the Tucana-Horologium moving group, a 45 million year old set of stars that share a common motion through space.

The brighter component, HD 24072, is a B-type main-sequence star with a classification of B9.5 Van. The n suffix indicates "nebulous" absorption lines which are caused by its rapid rotation. It has a projected rotational velocity of 225 km/s.

HD 24071 may itself be a spectroscopic binary. The visible component is an A-type main-sequence star with a stellar classification of A1 Va. It is a suspected variable star of unknown type showing an amplitude of 0.05 magnitude, and is a source of X-ray emission, which may originate from a companion of class G2-5V.