Epsilon Persei

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Epsilon Persei
Diagram showing star positions and boundaries of the Perseus constellation and its surroundings
Cercle rouge 100%.svg

Location of ε Persei (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Perseus
Right ascension 03h 57m 51.23205s[1]
Declination +40° 00′ 36.7752″[1]
Apparent magnitude (V) +2.88[2]
Spectral type B0.5 V+[3]
U−B color index –0.96[2]
B−V color index –0.20[2]
Variable type β Cep[4]
Proper motion (μ) RA: +14.06[1] mas/yr
Dec.: –23.78[1] mas/yr
Parallax (π) 5.11 ± 0.23[1] mas
Distance 640 ± 30 ly
(196 ± 9 pc)
Companion ε Per B
Period (P) 14.06916 ± 0.00004 days
Eccentricity (e) 0.5549 ± 0.0093
Periastron epoch (T) 47767.543 ± 0.024
Argument of periastron (ω)
105.8 ± 1.2°
Semi-amplitude (K1)
15.23 ± 0.20 km/s
ε Per A
Mass 13.5 ± 2.0[5] M
Radius 7.66[3] R
Luminosity 28,330[6] L
Temperature 26,500[6] K
Rotational velocity (v sin i) 155 ± 20[3] km/s
Age 15.4 ± 0.6[7] Myr
ε Per B
Mass 0.85–1.77[5] M
Radius 1.4 ± 0.4[5] R
Rotational velocity (v sin i) 300 ± 30[3] km/s
Other designations
45 Persei, BD+39 895, FK5 147, HD 24760, HIP 18532, HR 1220, SAO 56840.[8]
Database references

Epsilon Persei (ε Persei, ε Per) is a multiple star system in the northern constellation of Perseus. It has a combined apparent visual magnitude of +2.88,[2] which is bright enough to be viewed with the naked eye. Based upon parallax measurements, this system is located at a distance of roughly 640 light-years (196 parsecs) from Earth.[1]

This is a spectroscopic binary system, which means that the presence of an orbiting companion has been revealed by radial velocity variations in the spectrum of the primary. The two components are orbiting each other with a period of 14 days at a high orbital eccentricity of 0.55. The secondary component has about 6–13% of the primary's mass and may have a stellar classification in the range from A6 V to K1 V. There may be a third component to this system with an orbital period of roughly 9,428 days (25.8 years), although this has not been conclusively demonstrated. If this component exists, it would have about 51–139% of the primary's mass. This high level of uncertainty is because the inclination of the orbit is not known.[5]

The primary component of this system, Epsilon Persei A, is a massive star with 12–16[5] times the Sun's mass and near eight times the radius of the Sun.[3] It has a stellar classification of B0.5 V,[3] making it a B-type main sequence star that is generating energy at its core through the nuclear fusion of hydrogen. Component A is radiating over 28,000[6] times the Sun's luminosity from its outer envelope at an effective temperature of 26,500 K.[6] This gives the star the blue-white hue that is typical of B-type stars.[9]

Epsilon Persei A is a Beta Cephei variable star with a primary pulsation period of 0.1603 days, or 6.24 cycles per day. It may have multiple pulsation frequencies.[4]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c d Lutz, T. E.; Lutz, J. H. (June 1977), "Spectral classification and UBV photometry of bright visual double stars", Astronomical Journal, 82: 431–434, Bibcode:1977AJ.....82..431L, doi:10.1086/112066 
  3. ^ a b c d e f Howe, K. S.; Clarke, C. J. (January 2009), "An analysis of v sin (i) correlations in early-type binaries", Monthly Notices of the Royal Astronomical Society, 392 (1): 448–454, Bibcode:2009MNRAS.392..448H, doi:10.1111/j.1365-2966.2008.14073.x 
  4. ^ a b Stankov, Anamarija; Handler, Gerald (June 2005), "Catalog of Galactic β Cephei Stars", The Astrophysical Journal Supplement Series, 158 (2): 193–216, arXiv:astro-ph/0506495Freely accessible, Bibcode:2005ApJS..158..193S, doi:10.1086/429408 
  5. ^ a b c d e f Libich, J.; et al. (February 2006), "The new orbital elements and properties of ɛ Persei", Astronomy and Astrophysics, 446 (2): 583–589, Bibcode:2006A&A...446..583L, doi:10.1051/0004-6361:20053032 . Results per solution 6.
  6. ^ a b c d Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335Freely accessible, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355 
  7. ^ Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883Freely accessible, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x 
  8. ^ "eps Per -- Variable Star of beta Cep type". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2012-01-25. 
  9. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-10, retrieved 2012-01-16 

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