Iota Aquarii is a binary star system in the equatorial constellation of Aquarius. Its identifier is a Bayer designation that is Latinised from ù Aquarii, and abbreviated Iota Aqr or ù Aqr. This star is visible to the naked eye with an apparent magnitude of +4.279. Based upon parallax measurements, the distance to this star is around . The system is drifting closer to the Sun with a radial velocity of âÂÂ10 km/s.
Iota Aquarii was first catalogued in Uranometria in 1603; the binary nature of this system was discovered in 2009 following a radial velocity survey using the HARPS instrument. A 2010 infrared search for companions around this star was unsuccessful. The presence of a stellar companion was confirmed through direct spectral detection in 2016. The companion shows a significant velocity variation over a 77-day interval, suggesting a short orbital period. The companion was re-observed in 2024, showing a projected separation of 0.38 astronomical units. Together with the masses of the components, this suggests an orbital period of roughly 40 days.
The spectrum of the primary, component A, fits a stellar classification of B8 V, suggesting that this is a B-type main-sequence star. It is roughly 70 million years old and is spinning rapidly with a projected rotational velocity of 135 km/s. The star has 2.9 times the mass of the Sun and 2.1 times the Sun's radius. It is radiating 74 times the luminosity of the Sun from its photosphere at an effective temperature of 11,700 K. The secondary, component B, has 1.2 times the mass of the Sun, 1.1 times the radius, and an effective temperature of 6,350 K. The system is a source for X-ray emission.
There is evidence for a third companion based on the difference of proper motion measurements by the Hipparcos and Gaia spacecrafts. Such a companion would have an orbital period of roughly one year, and be either a faint red dwarf or a white dwarf.