Theta Arietis

Theta Arietis, Latinised from θ Arietis, is the Bayer designation for a binary star[7] system in the northern constellation of Aries. It is faintly visible to the naked eye with an apparent visual magnitude of 5.58.[2] With an annual parallax shift of 7.61 mas,[1] the distance to this star is an estimated 429 light-years (132 parsecs) with a 10-light-year margin of error. It is drifting further away with a radial velocity of +6 km/s.[2]

θ Arietis
Location of θ Arietis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aries
Right ascension 02h 18m 07.53022s[1]
Declination +19° 54′ 04.1717″[1]
Apparent magnitude (V) 5.58[2]
Characteristics
Spectral type A1 Vn[3]
U−B color index +0.02[4]
B−V color index +0.01[4]
Variable type Constant[5]
Astrometry
Radial velocity (Rv)+6.0[2] km/s
Proper motion (μ) RA: −7.491[1] mas/yr
Dec.: −3.978[1] mas/yr
Parallax (π)7.6084 ± 0.1763 mas[1]
Distance429 ± 10 ly
(131 ± 3 pc)
Absolute magnitude (MV)−0.10[6]
Details
A
Mass2.10+0.37
−0.31 M☉[7]
2.94±0.06[8] M☉
Radius1.9–2.5[9] R☉
Luminosity106[6] L☉
Surface gravity (log g)4.00±0.25[7] cgs
Temperature9,500±1,000[7] K
Rotational velocity (v sin i)186[10] km/s
Age107+286
−93[7] Myr
B
Mass1.0+0.02
−0.04[7] M☉
Temperature5,578±109[7] K
Metallicity [Fe/H]0.0[7] dex
Rotational velocity (v sin i)5[7] km/s
Other designations
θ Ari, 22 Arietis, BD+19 340, FK5 81, HD 14191, HIP 10732, HR 669, SAO 92877[11]
Database references
SIMBADdata

The primary, component A, is a white-hued, A-type main-sequence star with a stellar classification of A1 Vn.[3] It is spinning at a rapid pace as shown by the projected rotational velocity of 186 km/s.[10] This is causing the "nebulous" appearance of the absorption lines indicated by the 'n' suffix in the classification. In 2005, C. Neiner and associates classified this as a Be star because is displays emission features in the hydrogen Balmer lines.[5]

In 2016, a solar-mass companion was reported in close orbit around this star, based on observations using adaptive optics with the Gemini North Telescope.[7]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg, Astronomisches Rechen-Institut Heidelberg, 35 (35): 1, Bibcode:1999VeARI..35....1W.
  3. Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
  4. Rybka, E. (1969), "The corrected magnitudes and colours of 278 stars near S.A. 1-139 in the UBV system", Acta Astronomica, 19: 229, Bibcode:1969AcA....19..229R.
  5. Neiner, C.; et al. (February 2005), "The Identification of New Be Stars in GAUDI", The Astrophysical Journal Supplement Series, 156 (2): 237–243, Bibcode:2005ApJS..156..237N, doi:10.1086/426670, S2CID 123143757.
  6. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  7. Gullikson, Kevin; et al. (August 2016), "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars", The Astronomical Journal, 152 (2): 13, arXiv:1604.06456, Bibcode:2016AJ....152...40G, doi:10.3847/0004-6256/152/2/40, S2CID 119179065, 40.
  8. Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
  9. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367 (2): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
  10. Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298.
  11. "* tet Ari", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2012-08-06.
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