Epsilon Coronae Borealis
| Observation data Epoch J2000 Equinox | |
|---|---|
| Constellation | Corona Borealis |
| Right ascension | 15h 57m 35.25147s [1] |
| Declination | +26° 52′ 40.3635″ [1] |
| Apparent magnitude (V) | 4.13 |
| Characteristics | |
| Evolutionary stage | giant |
| Spectral type | K2III [1] |
| Astrometry | |
| Radial velocity (Rv) | –30.92 km/s |
| Proper motion (μ) | RA: -77.07 mas/yr Dec.: -60.61 mas/yr |
| Parallax (π) | 13.97 ± 0.68 mas |
| Distance | 230 ± 10 ly (72 ± 3 pc) |
| Details | |
| Mass | 1.7±0.1 M☉ |
| Radius | 21 R☉ |
| Luminosity (bolometric) | 151 L☉ |
| Temperature | 4406 ± 15 K |
| Metallicity [Fe/H] | –0.094 ± 0.001 dex |
| Age | 1.74±0.37 Gyr |
| Other designations | |
HD 143107, HR 5947, HIP 78159 | |
Epsilon Coronae Borealis (ε CrB) 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,[1] meaning it is visible to the unaided eye in all night skies except those brightly lit in inner city locations.[2] It is an orange giant around 1.7 times as massive as the Sun of spectral type K2III,[3] which has exhausted its core fuel supply of hydrogen and swollen to 21 times the Sun's diameter and 151 times its luminosity.[4] That is, Epsilon Coronae Borealis's diameter is about one-quarter of Mercury's orbit.[5] Its surface temperature has been calculated to be 4365 ± 9 K,[4] or 4406 ± 15 K.[3] It is thought to be around 1.74 billion years old.[3]
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.[5]
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.[5][6]
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.[3]
Epsilon Coronae Borealis lies one degree north of (and is used as a guide for) the variable T Coronae Borealis.[5]
References
- 1 2 3 4 SIMBAD, Epsilon Coronae Borealis (accessed 9 September 2012)
- ↑ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Retrieved 2013-02-20.
- 1 2 3 4 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. arXiv:1209.1187. Bibcode:2012A&A...546A...5L. doi:10.1051/0004-6361/201219347. A5.
- 1 2 Massarotti, Alessandro; Latham, David W.; Stefanik, Robert P.; Fogel, Jeffrey (January 2008). "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity". The Astronomical Journal 135 (1): 209–31. Bibcode:2008AJ....135..209M. doi:10.1088/0004-6256/135/1/209.
- 1 2 3 4 Kaler, James B. (19 August 2011). "Epsilon and T Coronae Borealis". Stars. University of Illinois. Retrieved 16 November 2014.
- ↑ SIMBAD, CCDM J15576+2652C -- Star in double system (accessed 16 November 2014)
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