Iota Arietis

Iota Arietis, Latinized from ι Arietis, is the Bayer designation for a binary star system in the northern constellation of Aries. It has an apparent visual magnitude of 5.117;[2] bright enough to be dimly seen with the naked eye. Parallax measurements made during the Hipparcos mission yield an estimated distance of 520 light-years (160 parsecs) from Earth.[1] 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.[7]

ι Arietis
Location of ι Arietis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Aries
Right ascension 01h 57m 21.05476s[1]
Declination +17° 49′ 03.1202″[1]
Apparent magnitude (V) 5.117[2]
Characteristics
Spectral type K1p[3] or G8III[4]
U−B color index +0.700[2]
B−V color index +0.921[2]
Astrometry
Radial velocity (Rv)−4.9[5] km/s
Proper motion (μ) RA: +34.76[1] mas/yr
Dec.: −22.95[1] mas/yr
Parallax (π)6.27 ± 0.33 mas[1]
Distance520 ± 30 ly
(159 ± 8 pc)
Absolute magnitude (MV)−0.4[6]
Orbit[7]
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)2,420,961.1±27.2 JD
Argument of periastron (ω)
(secondary)		94.04±4.72°
Semi-amplitude (K1)
(primary)		10.78±0.31 km/s
Details
Mass3.17[8] M☉
Radius20[8] R☉
Luminosity240[8] L☉
Surface gravity (log g)2.60[9] cgs
Temperature5,031[8] 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, HD 11909, HIP 9110, HR 563, SAO 92721[10]
Database references
SIMBADdata

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.".[3] E. A. Harlan published a class of K peculiar in 1969, commenting, "Hδ strong, Fe I λ4045 is weak for type".[11] 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.[4] Bayesian inference of the stellar properties indicates this star is on the horizontal branch.[8] The companion is a suspected white dwarf.[12]

References
  1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  2. Jennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants.", Monthly Notices of the Royal Astronomical Society, 172 (3): 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667.
  3. Roman, Nancy G. (July 1952), "The Spectra of the Bright Stars of Types F5-K5", Astrophysical Journal, 116: 122, Bibcode:1952ApJ...116..122R, doi:10.1086/145598.
  4. Sato, K.; Kuji, S. (1990), "MK classification and photometry of stars used for time and latitude observations at Mizusawa and Washington", Astronomy and Astrophysics Supplement Series, 85: 1069, Bibcode:1990A&AS...85.1069S.
  5. Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
  6. Helfer, H. L.; Wallerstein, George (August 1968), "Abundances in K-Giant Stars. II. a Survey of Field Stars", Astrophysical Journal Supplement, 16: 1, Bibcode:1968ApJS...16....1H, doi:10.1086/190169.
  7. Gordon, Katherine C. (1946), "The Spectroscopic Orbit of ι ARIETIS", The Astrophysical Journal, 103: 16–18, Bibcode:1946ApJ...103...16G, doi:10.1086/144784.
  8. Stock, Stephan; et al. (August 2018), "Precise radial velocities of giant stars. X. Bayesian stellar parameters and evolutionary stages for 372 giant stars from the Lick planet search", Astronomy & Astrophysics, 616: 15, arXiv:1805.04094, Bibcode:2018A&A...616A..33S, doi:10.1051/0004-6361/201833111, S2CID 119361866, A33.
  9. Hekker, S.; Meléndez, J. (2007), "Precise radial velocities of giant stars. III. Spectroscopic stellar parameters", Astronomy and Astrophysics, 475 (3): 1003–1009, arXiv:0709.1145, Bibcode:2007A&A...475.1003H, doi:10.1051/0004-6361:20078233, S2CID 10436552.
  10. "* iot Ari", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2012-08-04.
  11. Harlan, E. A. (September 1969), "MK classifications for F- and G-type stars. I", Astronomical Journal, 74: 916, Bibcode:1969AJ.....74..916H, doi:10.1086/110881.
  12. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
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