Sigma Arae

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Not to be confused with S Arae.
Sigma Arae
The location of σ Arae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ara
Right ascension 17h 35m 39.591s[1]
Declination −46° 30′ 20.46″[1]
Apparent magnitude (V) +4.575[2]
Characteristics
Spectral type A0 V[3]
U−B color index −0.064[2]
B−V color index −0.027[2]
Astrometry
Radial velocity (Rv)−9.28±0.33[1] km/s
Proper motion (μ) RA: −25.046 mas/yr[1]
Dec.: −38.30 mas/yr[1]
Parallax (π)8.5285±0.1394 mas[1]
Distance382 ± 6 ly
(117 ± 2 pc)
Absolute magnitude (MV)1.40[4]
Details
Mass2.56±0.35[5] M☉
Radius4.90±0.22[5] R☉
Luminosity215±22[5] L☉
Surface gravity (log g)3.47±0.07[5] cgs
Temperature9,986±206[5] K
Other designations
σ Arae, CD−46 11661, GC 23815, HD 159217, HIP 86092, HR 6537, SAO 228162, PPM 323154, TIC 16245795[6]
Database references
SIMBADdata

Sigma Arae is a star in the southern constellation of Ara. Its name is a Bayer designation that is Latinized from σ Arae, and abbreviated Sigma Ara or σ Ara. This star is visible to the naked eye with an apparent visual magnitude of +4.575.[2] The distance to this star, based upon an annual parallax shift of 8.53 mas,[1] is approximately 382 light-years (117 pc). It is drifting closer to the Sun with a radial velocity of −9 km/s.[1]

This is an A-type main sequence star with a stellar classification of A0 V.[3] It has 2.6 times the mass of the Sun and 4.9 times the Sun's radius. The star is radiating 215 times the luminosity of the Sun from its photosphere at an effective temperature of 9,986 K.[5] Unusually for an A-type star, X-ray emissions with a luminosity of 4.6×1029 erg s−1 have been detected from Sigma Arae. Normally this is explained by the presence of a lower mass orbiting companion star. However, such a scenario does not appear to hold true for this star. Instead, the signature of a surface magnetic field has been detected with a strength of roughly 128±73 Gauss, indicating the source of the X-rays may be surface magnetic activity.[7]

References

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  1. ^ a b c d e f g Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b c d Cousins, A. W. J. (1973), "Revised zero points and UBV photometry of stars in the Harvard E and F regions", Memoirs of the Royal Astronomical Society, 77: 223–236, Bibcode:1973MmRAS..77..223C.
  3. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 2, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  4. ^ Neff, James E.; Simon, Theodore (September 2008), "O VI Observations of the Onset of Convection Zones in Main-Sequence A Stars", The Astrophysical Journal, 685 (1): 478–488, arXiv:0805.4459, Bibcode:2008ApJ...685..478N, doi:10.1086/590423, S2CID 8607533.
  5. ^ a b c d e f Stassun, Keivan G.; et al. (September 2019), "The Revised TESS Input Catalog and Candidate Target List", The Astronomical Journal, 158 (4): 138, arXiv:1905.10694, Bibcode:2019AJ....158..138S, doi:10.3847/1538-3881/ab3467, ISSN 1538-3881.
  6. ^ "* sig Ara". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-08-02.{{cite web}}: CS1 maint: postscript (link)
  7. ^ Schröder, C.; et al. (June 2008), "Magnetic fields in A-type stars associated with X-ray emission", Astronomy and Astrophysics, 484 (2): 479–486, Bibcode:2008A&A...484..479S, doi:10.1051/0004-6361:20078963.
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