DH Cephei

DH Cephei
	; DH Cephei is at the center of this image of the NGC 7380 complex
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Cepheus
Right ascension	22h 46m 54.111s
Declination	+58° 05′ 03.53″
Apparent magnitude (V)	8.61 (8.63 – 8.70)
Characteristics
Evolutionary stage	Main sequence
Spectral type	O5.5 V + O6 V
B−V color index	0.334±0.041
Variable type	Ellipsoidal
Astrometry
Radial velocity (Rv)	−33.4±3.2 km/s
Proper motion (μ)	RA: −2.599 mas/yr ; Dec.: −2.236 mas/yr
Parallax (π)	0.3397 ± 0.0138 mas
Distance	9,600 ± 400 ly ; (2,900 ± 100 pc)
Absolute magnitude (MV)	−4.66±0.25 (A); −4.55±0.25 (B)
Orbit
Period (P)	2.11095 d
Semi-major axis (a)	≥9.79±0.17 R☉
Eccentricity (e)	0.0 (fixed)
Periastron epoch (T)	2,456,525.564±0.006 HJD
Details
A
Mass	25.0 or; 38.4±2.5 M☉
Radius	8.31 R☉
Luminosity	2.34×105 L☉
Surface gravity (log g)	4.3±0.3 cgs
Temperature	44,000 K
Rotational velocity (v sin i)	175 km/s
B
Mass	16.8 or; 33.4±2.2 M☉
Radius	7.76 R☉
Luminosity	1.86×105 L☉
Surface gravity (log g)	4.3±0.2 cgs
Temperature	43,000 K
Rotational velocity (v sin i)	160 km/s
Other designations
	DH Cep, BD+57° 2607, HD 215835, HIP 112470, WDS 22469+5805
Database references
SIMBAD	data

DH Cephei is a variable binary star^[5] system in the northern circumpolar constellation of Cepheus, positioned about two degrees to the east of the star system Delta Cephei.^[10] With an apparent visual magnitude of 8.61,^[3] it is too faint to be visible without a telescope. Based on parallax measurements, this system is located at a distance of approximately 9.6 kilolight-years (2.9 kiloparsecs) from the Sun.^[2] At present it is moving closer to the Earth with a radial velocity of −33 km/s.^[6]

A visual band light curve for DH Cephei, adapted from Lines *et al.* (1986)^[11]

This is a double-lined spectroscopic binary system consisting of two near-identical, massive, O-type main sequence stars.^[5] Evolutionary tracks place the stars close to the zero age main sequence, with an age of less than two million years.^[12] This is a detached binary^[12] with a close orbit having a period of 2.11 days, and the orbit is assumed to have circularized. The orbital plane is estimated to be inclined by an angle of 47°±1° to the line of sight from the Earth, which yields mass estimates of 38 and 34 times the mass of the Sun.^[3] Although initially suspected to be an eclipsing binary and given a variable star designation,^[8] it doesn't appear to be eclipsing.^[3] Instead, the system displays ellipsoidal light variations that are caused by tidal distortions.^[7]

This system lies at the center of the young open cluster NGC 7380. It is the primary ionizing source for the surrounding H II region designated S142. The pair are a source of X-ray emission, which may be the result of colliding stellar winds.^[13] Their measured X-ray luminosity is 3.2×10³¹ erg s⁻¹.^[9] The location and rare class of these stars make them an important object for astronomical studies.^[8]

References

^ ^a ^b "HD 215835". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-10-20.{{cite web}}: CS1 maint: postscript (link)
^ ^a ^b ^c ^d ^e Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
^ ^a ^b ^c ^d ^e ^f Martins, F.; et al. (November 2017), "Properties of six short-period massive binaries: A study of the effects of binarity on surface chemical abundances", Astronomy & Astrophysics, 607: 13, arXiv:1709.00937, Bibcode:2017A&A...607A..82M, doi:10.1051/0004-6361/201731593, S2CID 7835895, A82.
^ ^a ^b Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
^ ^a ^b ^c Sota, A.; et al. (March 2014), "The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars", The Astrophysical Journal Supplement, 211 (1): 84, arXiv:1312.6222, Bibcode:2014ApJS..211...10S, doi:10.1088/0067-0049/211/1/10, S2CID 118847528, 10.
^ ^a ^b ^c 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.
^ ^a ^b Penny, Laura R.; et al. (July 1997), "Tomographic Separation of Composite Spectra. IV. The Physical Properties of the Massive Close Binary DH Cephei", The Astrophysical Journal, 483 (1): 439–448, Bibcode:1997ApJ...483..439P, doi:10.1086/304239.
^ ^a ^b ^c Hilditch, R. W.; et al. (October 1996), "New masses for the O-type binary DH Cephei, and the temperatures of O-stars.", Astronomy and Astrophysics, 314: 165–172, Bibcode:1996A&A...314..165H.
^ ^a ^b ^c ^d ^e ^f ^g Krtička, J.; et al. (July 2015), "X-ray irradiation of the winds in binaries with massive components", Astronomy & Astrophysics, 579: 15, arXiv:1505.03411, Bibcode:2015A&A...579A.111K, doi:10.1051/0004-6361/201525637, S2CID 119120927, A111.
^ Sinnott, Roger W.; Perryman, Michael A. C. (1997), Millennium Star Atlas, vol. 3, Sky Publishing Corporation and the European Space Agency, p. 1071, ISBN 0-933346-84-0.
^ Lines, L. C.; Lines, R. D.; Guinan, E. F.; Robinson, C. R. (September 1986), "B and V Light Curves of the Massive Close Binary DH Cephei", Information Bulletin on Variable Stars, 2932: 1, Bibcode:1986IBVS.2932....1L, retrieved 1 January 2022.
^ ^a ^b Sturm, E.; Simon, K. P. (February 1994), "Spectroscopic analysis of hot binaries. I. The components of DH Cephei", Astronomy and Astrophysics, 282: 93–105, Bibcode:1994A&A...282...93S.
^ Lata, Sneh; et al. (March 2016), "Variable stars in young open star cluster NGC 7380", Monthly Notices of the Royal Astronomical Society, 456 (3): 2505–2517, arXiv:1511.08892, Bibcode:2016MNRAS.456.2505L, doi:10.1093/mnras/stv2800, S2CID 118473907.

[SIMBAD-1] "HD 215835". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-10-20.{{cite web}}: CS1 maint: postscript (link)

[GaiaEDR3-2] Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.

[Martins2017-3] ^ ^a ^b ^c ^d ^e ^f Martins, F.; et al. (November 2017), "Properties of six short-period massive binaries: A study of the effects of binarity on surface chemical abundances", Astronomy & Astrophysics, 607: 13, arXiv:1709.00937, Bibcode:2017A&A...607A..82M, doi:10.1051/0004-6361/201731593, S2CID 7835895, A82.

[Samus2017-4] Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.

[Sota2014-5] Sota, A.; et al. (March 2014), "The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars", The Astrophysical Journal Supplement, 211 (1): 84, arXiv:1312.6222, Bibcode:2014ApJS..211...10S, doi:10.1088/0067-0049/211/1/10, S2CID 118847528, 10.

[Anderson2012-6] 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.

[Penny1997-7] Penny, Laura R.; et al. (July 1997), "Tomographic Separation of Composite Spectra. IV. The Physical Properties of the Massive Close Binary DH Cephei", The Astrophysical Journal, 483 (1): 439–448, Bibcode:1997ApJ...483..439P, doi:10.1086/304239.

[Hilditch1996-8] Hilditch, R. W.; et al. (October 1996), "New masses for the O-type binary DH Cephei, and the temperatures of O-stars.", Astronomy and Astrophysics, 314: 165–172, Bibcode:1996A&A...314..165H.

[Krtička2015-9] ^ ^a ^b ^c ^d ^e ^f ^g Krtička, J.; et al. (July 2015), "X-ray irradiation of the winds in binaries with massive components", Astronomy & Astrophysics, 579: 15, arXiv:1505.03411, Bibcode:2015A&A...579A.111K, doi:10.1051/0004-6361/201525637, S2CID 119120927, A111.

[Sinnott1997-10] Sinnott, Roger W.; Perryman, Michael A. C. (1997), Millennium Star Atlas, vol. 3, Sky Publishing Corporation and the European Space Agency, p. 1071, ISBN 0-933346-84-0.

[Lines-11] Lines, L. C.; Lines, R. D.; Guinan, E. F.; Robinson, C. R. (September 1986), "B and V Light Curves of the Massive Close Binary DH Cephei", Information Bulletin on Variable Stars, 2932: 1, Bibcode:1986IBVS.2932....1L, retrieved 1 January 2022.

[Sturm1994-12] Sturm, E.; Simon, K. P. (February 1994), "Spectroscopic analysis of hot binaries. I. The components of DH Cephei", Astronomy and Astrophysics, 282: 93–105, Bibcode:1994A&A...282...93S.

[Lata2016-13] Lata, Sneh; et al. (March 2016), "Variable stars in young open star cluster NGC 7380", Monthly Notices of the Royal Astronomical Society, 456 (3): 2505–2517, arXiv:1511.08892, Bibcode:2016MNRAS.456.2505L, doi:10.1093/mnras/stv2800, S2CID 118473907.

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DH Cephei

References

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