Iota Arietis
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Aries |
| Right ascension | 01h 57m 21.058s |
| Declination | +17° 49′ 03.20″ |
| Apparent magnitude (V) | 5.117 |
| Characteristics | |
| Evolutionary stage | horizontal branch |
| Spectral type | K1p or G8III |
| U−B color index | +0.700 |
| B−V color index | +0.921 |
| Astrometry | |
| Radial velocity (Rv) | 2.21±0.07 km/s |
| Proper motion (μ) | RA: +37.138 mas/yr Dec.: −19.983 mas/yr |
| Parallax (π) | 7.4277±0.2980 mas |
| Distance | 440 ± 20 ly (135 ± 5 pc) |
| Absolute magnitude (MV) | −0.4 |
| Orbit | |
| Period (P) | 1,567.66±0.62 d |
| Semi-major axis (a) | ≥ 217 Gm (1.45 AU) |
| Eccentricity (e) | 0.356±0.022 |
| Periastron epoch (T) | 2420961.1±27.2 JD |
| Argument of periastron (ω) (secondary) | 94.04±4.72° |
| Semi-amplitude (K1) (primary) | 10.78±0.31 km/s |
| Details | |
| Mass | 3.17+0.08 −0.09 M☉ |
| Radius | 20.4+0.7 −0.8 R☉ |
| Luminosity | 240+16 −20 L☉ |
| Surface gravity (log g) | 2.60 cgs |
| Temperature | 5,031+6 −2 K |
| Metallicity [Fe/H] | −0.10 dex |
| Rotational velocity (v sin i) | 3.33 km/s |
| Other designations | |
| ι Ari, 8 Arietis, BD+17 289, FK5 2132, GC 2347, HD 11909, HIP 9110, HR 563, SAO 92721, PPM 117816 | |
| Database references | |
| SIMBAD | data |
Iota Arietis is a binary star system in the northern constellation of Aries. Its name is a Bayer designation that is Latinized from ι Arietis, and abbreviated Iota Ari or ι Ari. This star has an apparent visual magnitude of 5.117; bright enough to be dimly seen with the naked eye. Parallax measurements yield an estimated distance of approximately 440 light-years (130 parsecs) from Earth. The position of this system near the ecliptic means it is subject to lunar occultation.
The variable radial velocity of this system was announced by W. W. Campbell in 1922. K. C. Gordon published orbital elements for this single-lined spectroscopic binary system in 1946, giving an orbital period of 4.29 years and an eccentricity (ovalness) of 0.36.
For the visible component, in 1952 N. G. Roman found a stellar classification of K1p, where the 'p' indicates some type of peculiarity with the spectrum. Her comments indicated that the "Hydrogen lines and λ 4290 are strong enough to indicate a class II star, but the CN is barely strong enough for class III, and the Sr II is not much stronger than this would require.". E. A. Harlan published a class of K peculiar in 1969, commenting, "Hδ strong, Fe I λ4045 is weak for type". In 1990, K. Sato and S. Kuji gave a class of G8III, suggesting this is an aging G-type giant star and questioning its peculiar status. Bayesian inference of the stellar properties indicates this star is on the horizontal branch. The companion is a suspected white dwarf.