Epsilon Cephei

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Epsilon Cephei
EpsilonCepLightCurve.png
A visual band light curve for Epsilon Cephei, adapted from Bruntt et al. (2007) [1]
Observation data
Epoch J2000.0        Equinox J2000.0 (ICRS)
Constellation Cepheus
Right ascension 22h 15m 02.19530s [2]
Declination +57° 02′ 36.8771″ [2]
Apparent magnitude  (V)4.15 - 4.21 [3]
Characteristics
Spectral type F0 V (Sr II) [4] or F0 IV [5]
U−B color index +0.073 [6]
B−V color index +0.277 [6]
Variable type δ Sct [3]
Astrometry
Radial velocity (Rv)−4.7±0.8 [7]  km/s
Proper motion (μ)RA: +481.53 [2]   mas/yr
Dec.: +46.04 [2]   mas/yr
Parallax (π)38.17 ± 0.97  mas [2]
Distance 85 ± 2  ly
(26.2 ± 0.7  pc)
Absolute magnitude  (MV)+2.13 [8]
Details
ε Cep Aa
Mass 1.64 [9]   M☉
Radius 1.86 [10]   R☉
Luminosity 11.65 [8]   L☉
Surface gravity (log g)4.11±0.14 [9]   cgs
Temperature 7,514±255 [9]   K
Metallicity [Fe/H]+0.08 [8]   dex
Rotational velocity (v sin i)91 [11]  km/s
Age 1.097 [9]   Gyr
ε Cep Ab
Mass 0.57 [12]   M☉
Other designations
ε Cephei, 23 Cephei, BD+56 2741, HD  211336, HIP  109857, HR  8494, SAO  34227 [13]
Database references
SIMBAD data

Epsilon Cephei, Latinized from ε Cephei, is a star in the northern constellation of Cepheus. Based upon an annual parallax shift of 38.17  mas as seen from the Earth, [2] it is located about 85  light years from the Sun. The star is visible to the naked eye with an apparent visual magnitude of 4.18. [6]

Contents

Properties

Physical Characteristics

This is a yellow-white hued, F-type star with a stellar classification of F0 V (Sr II) [4] or F0 IV. [5] Thus it may either be an F-type main sequence star showing an abundance excess of strontium, or it could be a more evolved subgiant star. It is a Delta Scuti variable star that cycles between magnitudes 4.15 and 4.21 every 59.388 minutes. [3] The star displays an infrared excess, indicating the presence of a debris disk with a temperature of 65 K orbiting at a radius of 62  AU. This dust has a combined mass equal to 6.6% of the Earth's mass. [10]

Binary

There is a faint companion star at an angular separation of 330±50 mas along a position angle of 90°±10°. This corresponds to a projected physical separation of 8.6±1.4  AU . The probability of a random star being situated this close to Epsilon Cephei is about one in a million, so it is most likely physically associated. If so, then the debris disk is probably circumbinary. The fact that this companion was not detected during the Hipparcos mission may indicate its orbit has a high eccentricity. The companion star has a K-band magnitude of 7.8 and is probably of class K8–M2. [5]

Naming

In Chinese, 螣蛇 (Téng Shé), meaning Flying Serpent , refers to an asterism consisting of ε Cephei, α Lacertae, 4 Lacertae, π2 Cygni, π1 Cygni, HD 206267, β Lacertae, σ Cassiopeiae, ρ Cassiopeiae, τ Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, λ Andromedae, κ Andromedae, ι Andromedae, and ψ Andromedae. Consequently, the Chinese name for ε Cephei itself is 螣蛇九 (Téng Shé jiǔ, English: the Ninth Star of Flying Serpent) [14]

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<span class="mw-page-title-main">Alpha Lacertae</span> Star in the constellation Lacerta

Alpha Lacertae, Latinised from α Lacertae, is a single white-hued star in the constellation of Lacerta, located 103 light-years from the Sun. It is the brightest star in Lacerta with an apparent visual magnitude of 3.76. The star is moving closer to the Earth with a heliocentric radial velocity of −4.5 km/s.

<span class="mw-page-title-main">Beta Lacertae</span> G-type giant star in the constellation Lacerta

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<span class="mw-page-title-main">Epsilon Pavonis</span> Star in the constellation Pavo

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References

  1. ↑ Bruntt, H.; Suárez, J. C.; Bedding, T. R.; Buzasi, D. L.; Moya, A.; Amado, P. J.; Martín-Ruiz, S.; Garrido, R.; López de Coca, P.; Rolland, A.; Costa, V.; Olivares, I.; García-Pelayo, J. M. (January 2007), "Asteroseismology with the WIRE satellite I. Combining ground- and space-based photometry of the δ Scuti star ɛ Cephei", Astronomy and Astrophysics, 461 (2): 619–630, arXiv: astro-ph/0610539 , Bibcode:2007A&A...461..619B, doi: 10.1051/0004-6361:20065766 .
  2. 1 2 3 4 5 6 van Leeuwen, F. (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. 1 2 3 "eps Cep", AAVSO Website, American Association of Variable Star Observers , retrieved 2017-05-07.
  4. 1 2 Gray, R. O.; et al. (2001), "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars", The Astronomical Journal, 121 (4): 2148–2158, Bibcode:2001AJ....121.2148G, doi:10.1086/319956.
  5. 1 2 3 Mawet, D.; et al. (September 2011), "A Dim Candidate Companion to epsilon Cephei", The Astrophysical Journal Letters, 738 (1): 5, arXiv: 1107.3872 , Bibcode:2011ApJ...738L..12M, doi:10.1088/2041-8205/738/1/L12, S2CID   37505271, L12.
  6. 1 2 3 Breger, M. (March 1968), "UBV and narrow-band UVBY photometry of bright stars", Astronomical Journal, 73: 84–85, Bibcode:1968AJ.....73...84B, doi:10.1086/110602.
  7. ↑ Gontcharov, G. A. (2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv: 1606.08053 , Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID   119231169
  8. 1 2 3 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv: 1108.4971 , Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID   119257644.
  9. 1 2 3 4 David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv: 1501.03154 , Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID   33401607.
  10. 1 2 Rhee, Joseph H.; et al. (May 2007), "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs", The Astrophysical Journal, 660 (2): 1556–1571, arXiv: astro-ph/0609555 , Bibcode:2007ApJ...660.1556R, doi:10.1086/509912, S2CID   11879505.
  11. ↑ Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv: astro-ph/0610785 , Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID   18475298.
  12. ↑ De Rosa, R. J.; Patience, J.; Wilson, P. A.; Schneider, A.; Wiktorowicz, S. J.; Vigan, A.; Marois, C.; Song, I.; MacIntosh, B.; Graham, J. R.; Doyon, R.; Bessell, M. S.; Thomas, S.; Lai, O. (2013), "The VAST Survey - III. The multiplicity of A-type stars within 75 pc", Monthly Notices of the Royal Astronomical Society, 437 (2): 1216, arXiv: 1311.7141 , Bibcode:2014MNRAS.437.1216D, doi: 10.1093/mnras/stt1932 .
  13. ↑ "eps Cep -- Variable Star of delta Sct type", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg , retrieved 2017-05-06.
  14. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 7 日 Archived 2011-05-21 at the Wayback Machine
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