Iota Aquarii

Iota Aquarii is a binary star^[7] system in the equatorial constellation of Aquarius. Its identifier is a Bayer designation that is Latinised from ι Aquarii, and abbreviated Iota Aqr or ι Aqr, respectively. This star is visible to the naked eye with an apparent magnitude of +4.279.^[3] Based upon parallax measurements, the distance to this star is around 211 light-years (65 parsecs).^[2] The system is drifting closer to the Sun with a radial velocity of −10 km/s.^[6]

Iota Aquarii

Location of ι Aquarii (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Aquarius[1]
Right ascension	22h 06m 26.227s[2]
Declination	−13° 52′ 10.85″[2]
Apparent magnitude (V)	4.279[3]
Characteristics
Spectral type	B8 V[4]
U−B color index	−0.288[3]
B−V color index	−0.062[3]
Variable type	constant[5]
Astrometry
Radial velocity (Rv)	−10.0[6] km/s
Proper motion (μ)	RA: +42.210 mas/yr[2] Dec.: −56.566 mas/yr[2]
Parallax (π)	15.4940±0.2103 mas[2]
Distance	211 ± 3 ly (64.5 ± 0.9 pc)
Absolute magnitude (MV)	+0.64[1]
Details[7]
A
Mass	3.20+0.20 −0.16 M☉
Radius	2.7[8] R☉
Luminosity	74[1] L☉
Surface gravity (log g)	4.09±0.08[9] cgs
Temperature	11,284±284[8] K
Metallicity [Fe/H]	−0.08±0.12[9] dex
Rotational velocity (v sin i)	135[10] km/s
Age	124+37 −62 Myr
B
Mass	1.00±0.03 M☉
Temperature	5,710±112 K
Metallicity [Fe/H]	−0.5 dex
Rotational velocity (v sin i)	20 km/s
Other designations
ι Aquarii, ι Aqr, 33 Aquarii, BD−14 6209, FK5 828, GC 30914, HD 209819, HIP 109139, HR 8418, SAO 164861, PPM 239801[11]
Database references
SIMBAD	data

The binary nature of this system was reported in 2009 following a radial velocity survey using the HARPS instrument.^[5] A 2010 infrared search for companions around this star was unsuccessful.^[12] 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.^[7]

The spectrum of the primary, component A, fits a stellar classification of B8 V,^[4] showing that this is a B-type main-sequence star. It is roughly 124^[7] million years old and is spinning rapidly with a projected rotational velocity of 135 km/s.^[10] The star has 3.2^[7] times the mass of the Sun and 2.7^[8] times the Sun's radius. It is radiating 74^[1] times the luminosity of the Sun from its photosphere at an effective temperature of ~11,284 K.^[8] The secondary, component B, has a spectrum of a solar-mass star.^[7] The system is a source for X-ray emission.^[13]