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Epsilon Coronae Australis

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Epsilon Coronae Australis

A light curve for Epsilon Coronae Australis plotted from TESS data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Corona Australis
Right ascension 18h 58m 43.37714s[2]
Declination −37° 06′ 26.4865″[2]
Apparent magnitude (V) +4.75[3]
Characteristics
Spectral type F4V Fe-0.8[4]
U−B color index +0.01[3]
B−V color index +0.39[3]
Variable type W UMa[5]
Astrometry
Radial velocity (Rv)57.90 ± 1.2[6] km/s
Proper motion (μ) RA: −132.40[2] mas/yr
Dec.: −110.62[2] mas/yr
Parallax (π)33.13 ± 0.33 mas[2]
Distance98.4 ± 1.0 ly
(30.2 ± 0.3 pc)
Absolute magnitude (MV)2.21[7]
Orbit[8]
Period (P)0.59143357 ± 0.00000016 d
Semi-major axis (a)3.795 ± 0.052 R☉
Eccentricity (e)0
Inclination (i)73.05 ± 0.16°
Longitude of the node (Ω)2.0113 ± 0.0033°
Periastron epoch (T)JD 2442296.95907 ± 0.0070
Details
ε CrA A
Mass1.9[8] M☉
Radius2.167[8][note 1] R☉
Temperature6481 ± 20[8] K
Rotational velocity (v sin i)148.5[9] km/s
ε CrA B
Mass0.24[8] M☉
Radius0.869[8][note 1] R☉
Temperature5939 ± 19[8] K
Other designations
ε CrA, CD−37°13001, CPD−37°8433, HD 175813, HIP 93174, HR 7152, SAO 210781[5]
Database references
SIMBADdata

Epsilon Coronae Australis (ε CrA), is a star system located in the constellation Corona Australis. Varying in brightness between apparent magnitudes of 4.74 to 5 over 14 hours, it is the brightest W Ursae Majoris variable (low mass contact binary) in the night sky.

Naming

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Nicolas Louis de Lacaille gave Epsilon Coronae Australis its Bayer designation. It is also known as HR 7152, and HD 175813.

Properties

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Epsilon Coronae Australis is an F4V dwarf star with an effective temperature of 6000 Kelvin. It ranges between apparent magnitudes of 4.74 to 5 over 14 hours,[10] an absolute magnitude of +2.45, and a mass of 1.1 solar masses. Epsilon Coronae Australis is a W Ursae Majoris variable, indicating that it has a contact companion within the Roche limit of the primary. The star is located at a distance of 30 pc (97 light years) from the Sun.[7] Yildiz and colleagues estimated the age of the system at 2.83 ± 0.28 billion years based on study of the properties of the system and estimated rate of mass transfer. They found the current masses of the primary and secondary to be 1.72 ± 0.04 and 0.22 ± 0.02 solar masses respectively, from their original masses of 1.06 ± 0.03 and 2.18 ± 0.06 solar masses.[11]

Notes

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  1. ^ a b Radii were given as a ratio of the radius to the semi-major axis; the semi-major axis is 3.795 R☉.

References

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  1. ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
  2. ^ a b c d e van Leeuwen, F.; et al. (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.
  3. ^ a b c Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  4. ^ Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Bubar, E. J.; McGahee, C. E.; O'Donoghue, A. A.; Knox, E. R. (2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc--The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID 119476992.
  5. ^ a b "* eps CrA". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 13 March 2017.
  6. ^ Bilir, S.; Karataş, Y.; Demircan, O.; Eker, Z. (2005). "Kinematics of W Ursae Majoris type binaries and evidence of the two types of formation". Monthly Notices of the Royal Astronomical Society. 357 (2): 497–517. arXiv:astro-ph/0411291. Bibcode:2005MNRAS.357..497B. doi:10.1111/j.1365-2966.2005.08609.x. S2CID 16274339.
  7. ^ a b Eker, Z.; Bilir, S.; Yaz, E.; Demircan, O.; Helvaci, M. (2009). "New absolute magnitude calibrations for W Ursa Majoris type binaries". Astronomische Nachrichten. 330 (1): 68–77. arXiv:0807.4989. Bibcode:2009AN....330...68E. doi:10.1002/asna.200811041. S2CID 15071352.
  8. ^ a b c d e f g Wilson, R. E.; Raichur, H. (2011). "Distance and temperature from absolute light curves of three eclipsing binaries". Monthly Notices of the Royal Astronomical Society. 415 (1): 596–604. Bibcode:2011MNRAS.415..596W. doi:10.1111/j.1365-2966.2011.18741.x.
  9. ^ Schröder, C.; Reiners, Ansgar; Schmitt, Jürgen H. M. M. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo" (PDF), Astronomy and Astrophysics, 493 (3): 1099–1107, Bibcode:2009A&A...493.1099S, doi:10.1051/0004-6361:200810377[permanent dead link]
  10. ^ BSJ (4 January 2010). "Epsilon Coronae Australis". AAVSO Website. American Association of Variable Star Observers. Retrieved 22 January 2014.
  11. ^ Yildiz (2014). "Origin of W UMa-type contact binaries - age and orbital evolution". Monthly Notices of the Royal Astronomical Society. 437 (1): 185–94. arXiv:1310.5526. Bibcode:2014MNRAS.437..185Y. doi:10.1093/mnras/stt1874.
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