epsilon Cephei
{{Short description|Star in the constellation Cepheus}}
{{Starbox begin
| name = Epsilon Cephei
}}
{{Starbox image
| image = 250px
| caption = A visual band light curve for Epsilon Cephei, adapted from Bruntt et al. (2007)
}}
{{Starbox observe
| epoch = J2000.0
| constell = Cepheus
| dec = {{DEC|+57|02|36.8771}}
}}
{{Starbox character
| class = {{nowrap|F0 V (Sr II)}} or F0 IV
| r-i =
| variable = δ Sct
}}
{{Starbox astrometry
| parallax = 38.17
| p_error = 0.97
}}
{{Starbox detail
| source =
| component1 = ε Cep Aa
| temperature = {{Val|7514|255|fmt=commas}}
| component2 = ε Cep Ab
}}
{{Starbox catalog
| names = ε Cephei, 23 Cephei, BD+56 2741, HD 211336, HIP 109857, HR 8494, SAO 34227
}}
{{Starbox reference
| Simbad = eps+Cep
}}
{{Starbox end}}
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, 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.
Properties
= Physical Characteristics =
This is a yellow-white hued, F-type star with a stellar classification of {{nowrap|F0 V (Sr II)}} or F0 IV. 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. 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.
= Binary =
There is a faint companion star at an angular separation of {{Val|330|50|u=mas}} along a position angle of {{Val|90|10|u=°}}. This corresponds to a projected physical separation of {{Val|8.6|1.4|u=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.
Naming
In Chinese, {{lang|zh|螣蛇}} ({{lang|zh-Latn|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 {{lang|zh|螣蛇九}} ({{lang|zh-Latn|Téng Shé jiǔ}}, {{langx|en|the Ninth Star of Flying Serpent}})
References
{{reflist|refs=
| last1=Bruntt | first1=H. | last2=Suárez | first2=J. C. | last3=Bedding | first3=T. R.
| last4=Buzasi | first4=D. L. | last5=Moya | first5=A. | last6=Amado | first6=P. J.
| last7=Martín-Ruiz | first7=S. | last8=Garrido | first8=R. | last9=López de Coca | first9=P.
| last10=Rolland | first10=A. | last11=Costa | first11=V. | last12=Olivares | first12=I.
| last13=García-Pelayo | first13=J. M.
| title=Asteroseismology with the WIRE satellite I. Combining ground- and space-based photometry of the δ Scuti star ɛ Cephei
| journal=Astronomy and Astrophysics | date=January 2007 | volume=461 | issue=2 | pages=619–630
| doi=10.1051/0004-6361:20065766 | arxiv=astro-ph/0610539 | bibcode=2007A&A...461..619B | doi-access=free }}
| title=Validation of the new Hipparcos reduction
| last1=van Leeuwen | first1=F.
| journal=Astronomy and Astrophysics
| volume=474 | issue=2 | pages=653–664 | date=2007
| arxiv=0708.1752 | bibcode=2007A&A...474..653V
| doi=10.1051/0004-6361:20078357 | s2cid=18759600 | postscript=. }}
| title=XHIP: An extended hipparcos compilation
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| bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015
| arxiv=1108.4971 | s2cid=119257644 | postscript=. }}
| doi=10.1134/S1063773706110065 | bibcode=2006AstL...32..759G
| title=Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system
| journal=Astronomy Letters
| volume=32 | issue=11 | pages=759–771 | year=2006
| last1=Gontcharov | first1=G. A. |arxiv = 1606.08053 | s2cid=119231169
}}
| bibcode=2014MNRAS.437.1216D | doi=10.1093/mnras/stt1932 | arxiv=1311.7141
| title=The VAST Survey - III. The multiplicity of A-type stars within 75 pc
| journal=Monthly Notices of the Royal Astronomical Society
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| last13=Thomas | first13=S. | last14=Lai | first14=O. | doi-access=free }}
| title=eps Cep | work=AAVSO Website
| publisher=American Association of Variable Star Observers
| url=https://www.aavso.org/vsx/index.php?view=detail.top&oid=9067
| access-date=2017-05-07 | postscript=. }}
| title=A Dim Candidate Companion to epsilon Cephei
| display-authors=1 | last1=Mawet | first1=D.
| last2=Mennesson | first2=B. | last3=Serabyn | first3=E.
| last4=Stapelfeldt | first4=K. | last5=Absil | first5=O.
| journal=The Astrophysical Journal Letters | postscript=.
| volume=738 | issue=1 | id=L12 | pages=5 | date=September 2011
| doi=10.1088/2041-8205/738/1/L12 | bibcode=2011ApJ...738L..12M |arxiv = 1107.3872 | s2cid=37505271 }}
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| title=The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets
| journal=The Astrophysical Journal
| volume=804 | issue=2 | pages=146 | year=2015
| bibcode=2015ApJ...804..146D | doi=10.1088/0004-637X/804/2/146
| arxiv=1501.03154 | s2cid=33401607 | postscript=. }}
| last1=Rhee | first1=Joseph H. | last2=Song | first2=Inseok
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| display-authors=1 | journal=The Astrophysical Journal
| title=Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs
| volume=660 | issue=2 | pages=1556–1571 |date=May 2007
| doi=10.1086/509912 | bibcode=2007ApJ...660.1556R
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| title=The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars
| journal=The Astronomical Journal
| volume=121 | issue=4 | pages=2148–2158 | year=2001
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| title=Rotational velocities of A-type stars. III. Velocity distributions
| journal=Astronomy and Astrophysics
| volume=463 | issue=2 | pages=671–682 | date=February 2007
| doi=10.1051/0004-6361:20065224 | bibcode=2007A&A...463..671R
| arxiv=astro-ph/0610785 | s2cid=18475298 | postscript=. }}
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| title=UBV and narrow-band UVBY photometry of bright stars
| journal=Astronomical Journal | postscript=.
| volume=73 | pages=84–85 | date=March 1968
| doi=10.1086/110602 | bibcode=1968AJ.....73...84B }}
| title=eps Cep -- Variable Star of delta Sct type
| work=SIMBAD Astronomical Database
| publisher=Centre de Données astronomiques de Strasbourg
| url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=eps+Cep
| access-date=2017-05-06 | postscript=. }}
}}
{{Stars of Cepheus|state=collapsed}}
{{DEFAULTSORT:Epsilon Cephei}}
Category:F-type main-sequence stars
Category:Delta Scuti variables
Category:Cepheus (constellation)