Iota Arietis
Binary star system in the constellation Aries
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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;[2] 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.[11] The position of this system near the ecliptic means it is subject to lunar occultation.[12]
 | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Aries |
| Right ascension | 01h 57m 21.058s[1] |
| Declination | +17° 49′ 03.20″[1] |
| Apparent magnitude (V) | 5.117[2] |
| Characteristics | |
| Evolutionary stage | horizontal branch[3] |
| Spectral type | K1p[4] or G8III[5] |
| U−B color index | +0.700[2] |
| B−V color index | +0.921[2] |
| Astrometry | |
| Radial velocity (Rv) | 2.21±0.07[6] km/s |
| Proper motion (μ) | RA: +37.138 mas/yr[1] Dec.: −19.983 mas/yr[1] |
| Parallax (π) | 7.4277±0.2980 mas[1] |
| Distance | 440 ± 20 ly (135 ± 5 pc) |
| Absolute magnitude (MV) | −0.4[7] |
| Orbit[8] | |
| 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[3] M☉ |
| Radius | 20.4+0.7 −0.8[3] R☉ |
| Luminosity | 240+16 −20[3] L☉ |
| Surface gravity (log g) | 2.60[9] cgs |
| Temperature | 5,031+6 −2[3] K |
| Metallicity [Fe/H] | −0.10[9] dex |
| Rotational velocity (v sin i) | 3.33[9] 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[10] | |
| Database references | |
| SIMBAD | data |
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.[8]
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.".[4] E. A. Harlan published a class of K peculiar in 1969, commenting, "Hδ strong, Fe I λ4045 is weak for type".[13] 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.[5] Bayesian inference of the stellar properties indicates this star is on the horizontal branch.[3] The companion is a suspected white dwarf.[14]