Epsilon Coronae Australis
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Corona Australis |
Right ascension | 18h 58m 43.37714s[1] |
Declination | −37° 06′ 26.4865″[1] |
Apparent magnitude (V) | +4.75[2] |
Characteristics | |
Spectral type | F4V Fe-0.8[3] |
U−B color index | +0.01[2] |
B−V color index | +0.39[2] |
Variable type | W UMa[4] |
Astrometry | |
Radial velocity (Rv) | 57.90 ± 1.2[5] km/s |
Proper motion (μ) | RA: −132.40[1] mas/yr Dec.: −110.62[1] mas/yr |
Parallax (π) | 33.13 ± 0.33[1] mas |
Distance | 98.4 ± 1.0 ly (30.2 ± 0.3 pc) |
Absolute magnitude (MV) | 2.21[6] |
Orbit[7] | |
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 | |
Mass | 1.9[7] M☉ |
Radius | 2.167[7][note 1] R☉ |
Temperature | 6481 ± 20[7] K |
Rotational velocity (v sin i) | 148.5[8] km/s |
ε CrA B | |
Mass | 0.24[7] M☉ |
Radius | 0.869[7][note 1] R☉ |
Temperature | 5939 ± 19[7] K |
Other designations | |
Database references | |
SIMBAD | data |
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[]
Nicolas Louis de Lacaille gave Epsilon Coronae Australis its Bayer designation. It is also known as HR 7152, and HD 175813.
Properties[]
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,[9] 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.[6] 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.[10]
Notes[]
References[]
- ^ 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.
- ^ 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.
- ^ 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.
- ^ a b "* eps CrA". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 13 March 2017.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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
- ^ BSJ (4 January 2010). "Epsilon Coronae Australis". AAVSO Website. American Association of Variable Star Observers. Retrieved 22 January 2014.
- ^ 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.
- Corona Australis
- Bayer objects
- F-type main-sequence stars
- W Ursae Majoris variables
- Durchmusterung objects
- HR objects
- Henry Draper Catalogue objects
- Hipparcos objects