Astronomy:Epsilon Coronae Borealis
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| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Corona Borealis |
| Right ascension | 15h 57m 35.25147s[1] |
| Declination | +26° 52′ 40.3635″[1] |
| Apparent magnitude (V) | 4.13[2] |
| Characteristics | |
| Spectral type | K2 III[2] |
| U−B color index | +1.28[3] |
| B−V color index | +1.235[3] |
| Astrometry | |
| Radial velocity (Rv) | −32.42[2] km/s |
| Proper motion (μ) | RA: −77.07[1] mas/yr Dec.: −60.61[1] mas/yr |
| Parallax (π) | 13.4922 ± 0.1023[4] mas |
| Distance | 242 ± 2 ly (74.1 ± 0.6 pc) |
| Absolute magnitude (MV) | −0.02[5] |
| Details[6] | |
| Mass | 1.37±0.24 M☉ |
| Radius | 21.87+0.98 −0.99 R☉ |
| Luminosity (bolometric) | 162.9±9.4 L☉ |
| Surface gravity (log g) | 1.94±0.15[7] cgs |
| Temperature | 4,408±109 K |
| Metallicity [Fe/H] | −0.22±0.03[7] dex |
| Rotational velocity (v sin i) | 2.4[8] km/s |
| Age | 3.24±1.81 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Epsilon Coronae Borealis, Latinized from ε Coronae Borealis, is a multiple star system in the constellation Corona Borealis located around 230 light-years from the Solar System. It shines with a combined apparent magnitude of 4.13,[9] meaning it is visible to the unaided eye in all night skies except those brightly lit in inner city locations.[10]
This star has a stellar spectrum matching the class K2III, which indicate it is a giant star that exhausted its hydrogen supply at its core and evolved.[11] Being 40% more massive than the Sun and 3.2 billion years old, it expanded to over 20 times the Sun's size and cooled to an effective temperature of 4,408 K.[6] That is, Epsilon Coronae Borealis's diameter is about one-quarter of Mercury's orbit.[12] The star radiates with 160 times the Sun's luminosity.[6]
Epsilon Coronae Borealis B is a companion star thought to be an orange dwarf of spectral types K3V to K9V that orbits at a distance of 135 astronomical units, completing one orbit every 900 years.[12]
A faint (magnitude 11.5) star, 1.5 arc minutes away, has been called Epsilon Coronae Borealis C although it is only close by line of sight and is unrelated to the system.[12][13]
Epsilon Coronae Borealis lies one degree north of (and is used as a guide for) the variable T Coronae Borealis.[12]
Planetary system
The ε CrB star system's radial velocity was observed over seven years from January 2005 to January 2012, during which time a 'wobble' with a period of around 418 days was recorded. This has been calculated to be a planet around 6.7 times as massive as Jupiter orbiting at a distance of 1.3 astronomical units with an eccentricity of 0.11.[11]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥6.7 ± 0.3 MJ | 1.3 | 417.9 ± 0.5 | 0.11 ± 0.03 | — | — |
References
- ↑ 1.0 1.1 1.2 1.3 van Leeuwen, F. (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.
- ↑ 2.0 2.1 2.2 Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal 150 (3): 88, doi:10.1088/0004-6256/150/3/88, Bibcode: 2015AJ....150...88L.
- ↑ 3.0 3.1 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data. SIMBAD, Bibcode: 1986EgUBV........0M, http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?1986EgUBV........0M&db_key=AST&nosetcookie=1.
- ↑ Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G. Gaia EDR3 record for this source at VizieR.
- ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A.
- ↑ 6.0 6.1 6.2 Baines, Ellyn K. et al. (2018), "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer", The Astronomical Journal 155 (1): 30, doi:10.3847/1538-3881/aa9d8b, Bibcode: 2018AJ....155...30B.
- ↑ 7.0 7.1 Mortier, A. et al. (September 2013), "New and updated stellar parameters for 71 evolved planet hosts. On the metallicity-giant planet connection", Astronomy & Astrophysics 557: 19, doi:10.1051/0004-6361/201321641, A70, Bibcode: 2013A&A...557A..70M.
- ↑ Massarotti, Alessandro et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal 135 (1): 209–231, doi:10.1088/0004-6256/135/1/209, Bibcode: 2008AJ....135..209M.
- ↑ 9.0 9.1 "eps CrB". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=eps+CrB.
- ↑ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. http://www.skyandtelescope.com/resources/darksky/3304011.html?page=1&c=y.
- ↑ 11.0 11.1 Lee, B.-C.; Han, I.; Park, M.-G.; Mkrtichian, D. E.; Kim, K.-M. (2012). "A planetary companion around the K giant ɛ Corona Borealis". Astronomy & Astrophysics 546: 5. doi:10.1051/0004-6361/201219347. A5. Bibcode: 2012A&A...546A...5L.
- ↑ 12.0 12.1 12.2 12.3 Kaler, James B. (19 August 2011). "Epsilon and T Coronae Borealis". Stars. University of Illinois. http://stars.astro.illinois.edu/sow/epscrb.html.
- ↑ SIMBAD, CCDM J15576+2652C -- Star in double system (accessed 16 November 2014)
- ↑ Jean Schneider (2003). "Planet eps CrB b". Extrasolar Planets Encyclopaedia. https://exoplanet.eu/catalog/eps_crb_b--1201/. Retrieved 4 February 2017.
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