Astronomy:Epsilon Arietis

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Short description: Binary star system in the constellation Aries
ε Arietis
Location of ε Arietis (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Aries
Right ascension  02h 59m 12.726s[1]
Declination +21° 20′ 25.54″[1]
Apparent magnitude (V) 4.63[2] (5.2/5.5)[3]
Characteristics
Spectral type A2 Vs + A2 Vs[4]
U−B color index +0.08[2]
B−V color index +0.04[2]
R−I color index 0.02[citation needed]
Astrometry
Radial velocity (Rv)+0.9±0.9[5] km/s
Proper motion (μ) RA: −15.884[1] mas/yr
Dec.: −7.151[1] mas/yr
Parallax (π)9.0296 ± 0.1851[1] mas
Distance361 ± 7 ly
(111 ± 2 pc)
Orbit[6]
Period (P)704.111±1.778 yr
Semi-major axis (a)2.174±0.035″
Eccentricity (e)0.317±0.006
Inclination (i)84.2±0.8°
Longitude of the node (Ω)25.6±0.7°
Periastron epoch (T)704.111±1.778
Argument of periastron (ω)
(secondary)		162.1±1.0°
Details
ε Ari A
Mass2.4[6] M☉
Rotational velocity (v sin i)60[4] km/s
ε Ari B
Mass2.4[6] M☉
Rotational velocity (v sin i)60[4] km/s
Other designations
48 Arietis, BD+20 484, HIP 13914, ADS 2257, WDS J02592+2120AB[7]
ε Ari A: GC 3582, HD 18520, HR 888, SAO 75673, PPM 92122
ε Ari B: HD 18519, HR 887
Database references
SIMBADε Ari
ε Ari A
ε Ari B

Epsilon Arietis is a visual binary[8] star system in the northern constellation of Aries. Its name is a Bayer designation that is Latinized from ε Arietis, and abbreviated Epsilon Ari or ε Ari. This system has a combined apparent visual magnitude of 4.63[2] and can be seen with the naked eye, although the two components are too close together to be resolved without a telescope. With an annual parallax shift of 9.03 mas,[9] the distance to this system can be estimated as 361 light-years (111 parsecs), give or take a 7 light-year margin of error. It is located behind the dark cloud MBM12.[6]

The brighter member of this pair has an apparent magnitude of 5.2.[3] At an angular separation of 1.426″±0.010″ from the brighter component, along a position angle of 209.2°±0.3°,[8] is the magnitude 5.5 companion.[3] Both are A-type main sequence stars with a stellar classification of A2 Vs.[4] (The 's' suffix indicates that the absorption lines in the spectrum are distinctly narrow.) In the 2009 Catalogue of Ap, HgMn and Am stars, the two stars have a classification of A3 Ti,[3] indicating they are Ap stars with an anomalous abundance of titanium. Within the measurement margin of error, their projected rotational velocities are deemed identical at 60 km/s.[4]

Name

This star system, along with δ Ari, ζ Ari, π Ari, and ρ3 Ari, were Al Bīrūnī's Al Buṭain (ألبطين), the dual of Al Baṭn, the Belly.[10] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Buṭain were the title for five stars :δ Ari as Botein, π Ari as Al Buṭain I, ρ3 Ari as Al Buṭain II, ε Ari as Al Buṭain III and ζ Ari as Al Buṭain IV[11]

In Chinese astronomy, Epsilon Arietis may be or may be part of Tso Kang (from Cantonese 左更 zogang, Mandarin pronunciation zuǒgēng).[12][13]

References

  1. ↑ 1.0 1.1 1.2 1.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 Eggen, Olin J. (November 1963), "Luminosities, colors, and motions of the brightest A-type stars", Astronomical Journal 68: 697, doi:10.1086/109198, Bibcode: 1963AJ.....68..697E. 
  3. ↑ 3.0 3.1 3.2 3.3 Renson, P.; Manfroid, J. (May 2009), "Catalogue of Ap, HgMn and Am stars", Astronomy and Astrophysics 498 (3): 961–966, doi:10.1051/0004-6361/200810788, Bibcode: 2009A&A...498..961R. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 Royer, F. et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics 393: 897–911, doi:10.1051/0004-6361:20020943, Bibcode: 2002A&A...393..897R. 
  5. ↑ Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters 32 (11): 759–771, doi:10.1134/S1063773706110065, Bibcode: 2006AstL...32..759G. 
  6. ↑ 6.0 6.1 6.2 6.3 Rica, Francisco (April 2012), "Orbital Elements for BU 741 AB, STF 333 AB, BU 920 and R 207", Journal of Double Star Observations 8 (2): 127–139, Bibcode: 2012JDSO....8..127R. 
  7. ↑ "eps Ari". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=eps+Ari. 
  8. ↑ 8.0 8.1 Scardia, M. et al. (January 2007), "Speckle observations with PISCO in Merate - III. Astrometric measurements of visual binaries in 2005 and scale calibration with a grating mask", Monthly Notices of the Royal Astronomical Society 374 (3): 965–978, doi:10.1111/j.1365-2966.2006.11206.x, Bibcode: 2007MNRAS.374..965S, https://hal.archives-ouvertes.fr/hal-00288211/file/scard06_MerIII.pdf, retrieved 2025-05-04. 
  9. ↑ van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  10. ↑ Star Names: Their Lore and Meaning (Reprint ed.), New York, NY: Dover Publications Inc, 1963, p. 83, ISBN ((0-486-21079-0)), https://archive.org/details/starnamestheirlo00alle/page/83, retrieved 2010-12-12. 
  11. ↑ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology, https://ntrs.nasa.gov/citations/19720005197, retrieved 2025-05-04. 
  12. ↑ Chevalier, S., and Tsuchihashi, P., (1911): "Catalogue d'Étoiles fixes, observés a Pekin sous l'Empereur Kien Long (Qianlong (Chien-Lung)), XVIIIe siecle", Annales de l'Observatoire Astronomique de Zô-Sé.
  13. ↑ 伊世同 (Yi Shi Tong) (1981): 『中西対照恒星図表』科学出版社.(in Chinese)



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