DH Cephei

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DH Cephei
SH2-142HunterWilson.jpg
DH Cephei is at the center of this image of the NGC 7380 complex [1]
Observation data
Epoch J2000.0        Equinox J2000.0
Constellation Cepheus
Right ascension 22h 46m 54.111s [2]
Declination +58° 05′ 03.53″ [2]
Apparent magnitude  (V)8.61 [3] (8.63 – 8.70) [4]
Characteristics
Evolutionary stage Main sequence
Spectral type O5.5 V + O6 V [5]
B−V color index 0.334±0.041 [6]
Variable type Ellipsoidal [7] [4]
Astrometry
Radial velocity (Rv)−33.4±3.2 [6]  km/s
Proper motion (μ)RA: −2.599  mas/yr [2]
Dec.: −2.236  mas/yr [2]
Parallax (π)0.3397 ± 0.0138  mas [2]
Distance 9,600 ± 400  ly
(2,900 ± 100  pc)
Absolute magnitude  (MV)−4.66±0.25 (A)
−4.55±0.25 (B) [8]
Orbit [3]
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 [3]
A
Mass 25.0 [9] or
38.4±2.5  M☉
Radius 8.31 [9]   R☉
Luminosity 2.34×105 [9]   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 [9] or
33.4±2.2  M☉
Radius 7.76 [9]   R☉
Luminosity1.86×105 [9]   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 [1]
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) DHCepLightCurve.png
A visual band light curve for DH Cephei, adapted from Lines et al. (1986)

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]

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References

  1. 1 2 "HD 215835". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2020-10-20.{{cite web}}: CS1 maint: postscript (link)
  2. 1 2 3 4 5 6 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.
  3. 1 2 3 4 5 6 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.
  4. 1 2 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.
  5. 1 2 3 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.
  6. 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.
  7. 1 2 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 .
  8. 1 2 3 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.
  9. 1 2 3 4 5 6 7 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.
  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.
  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.
  12. 1 2 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.
  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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