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CV Serpentis is a binary star system in the equatorial constellation of Serpens. It is a detached eclipsing binary with an orbital period of 29.7 days.[5] The system includes a Wolf–Rayet (WR) star with the identifier WR 113. The system is located at a distance of approximately 6,700 light years from the Sun based on parallax measurements.[2] It is a member of the Serpens OB2 association of co-moving stars.[11]

CV Serpentis

A broad-band optical light curve for CV Serpentis, adapted from David-Uraz et al. (2012)[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Serpens
Right ascension 18h 19m 07.363s[2]
Declination −11° 37′ 59.16″[2]
Apparent magnitude (V) 9.08[3]
Characteristics
Spectral type WC8d + O8-9IV[4]
B−V color index 0.724±0.033[3]
Variable type E/D/WR[5]
Astrometry
Radial velocity (Rv)17±2[3] km/s
Proper motion (μ) RA: −0.691 mas/yr[2]
Dec.: −1.568 mas/yr[2]
Parallax (π)0.4896 ± 0.0157 mas[2]
Distance6,700 ± 200 ly
(2,040 ± 70 pc)
Absolute magnitude (MV)System: −5.1±0.8
WR star: −3.6+1.8
−1.3[6]
Orbit[1]
Period (P)29.704 d
Eccentricity (e)0.02±0.02
Inclination (i)63.5±2.5[4]°
Periastron epoch (T)2,455,003±1 HJD
Argument of periastron (ω)
(secondary)		330±10°
Semi-amplitude (K1)
(primary)		173±1 km/s
Details
OB star
Mass33.3±2.0[4] M☉
Luminosity64,749[7] L☉
Temperature27,570[7] K
Rotational velocity (v sin i)310-330[8] km/s
WR star
Mass11.7±0.9[4] M☉
Luminosity24,018[7] L☉
Temperature44,500[9] K
Other designations
WR 113, CV Ser, BD−11 4593, HD 168206, HIP 89769, SAO 161325, PPM 234357[10]
Database references
SIMBADdata

In 1892, this star was found to be an object of interest based on photographs of its peculiar stellar spectra taken from the Boyden Station in Arequipa, Peru.[12] It was determined to be a carbon-type Wolf–Rayet (WR) star and in 1945 was found to be a spectroscopic binary system by W. A. Hiltner.[13] This system was reported to be an eclipsing binary by S. Gaposchkin in 1949,[14] who found a decrease in brightness of 0.14 magnitude during the first eclipse and 0.08 in the second. R. M. Hjellming and W. A. Hiltner in 1963 measured a much deeper primary eclipse with a decrease of about 0.55 magnitude,[15] then in 1970 K. Stępień saw no evidence of eclipsing.[16] L. V. Kuhi and F. Schweizer confirmed this latter result, hypothesizing that it is the result of a changing Wolf-Rayet envelope.[17]

This is a double-lined spectroscopic binary system in a near circular orbit, meaning that the spectra of both components is visible.[4] The companion of the WR star is a massive OB star with a stellar classification of O8-9IV.[4] A nebulous double-shell centered on CV Ser was discovered in 1984, spanning angular diameters of 4′ and 9′. The diffuse outer ring is incomplete, spanning a radius of 5.4 pc at an approximate distance of two kiloparsecs.[18] Variations in the system's light curve continued to be observed, suggesting changes in the outflow from the Wolf-Rayet star.[19] An emission feature in the spectrum of the system was interpreted as a region between the two stars where their stellar winds are colliding,[20] forming a shock region of plasma.[4]

The system is expected to evolve into a binary with the OB-star and an 8 M☉ black hole following a failed supernova where the WR star collapses with little or no visible explosion.[21] The OB star is observed to be rotating rapidly at between 310 and 330 km/s using spectral lines of neutral helium. Observations using ionized helium absorption lines show a lower velocity, interpreted as showing an oblate shape with gravity darkening causing lower temperatures at the equator.[8]

Speckle interferometry has found a companion star 1.16″ from the bright primary and eight magnitudes fainter. The projected separation of 2,200 AU is much larger than the maximum possible 129 AU separation of the Wolf-Rayet and OB pair. If it is found to be at the same distance as the bright spectroscopic pair, it would likely be an F-type main sequence star in an orbit with a period around 100,000 years and the lowest-luminosity known companion of any WR star at 5 L☉.[22]


References


  1. David-Uraz, Alexandre; et al. (November 2012), "Using MOST to reveal the secrets of the mischievous Wolf-Rayet binary CV Ser", Monthly Notices of the Royal Astronomical Society, 426 (3): 1720–1730, arXiv:1207.6032, Bibcode:2012MNRAS.426.1720D, doi:10.1111/j.1365-2966.2012.21736.x.
  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.
  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.
  4. Hill, G. M.; Moffat, A. F. J.; St-Louis, N. (March 2018), "Modelling the colliding-wind spectra of the WC8d+O8-9IV binary CV Ser (WR 113)", Monthly Notices of the Royal Astronomical Society, 474 (3): 2987–2999, Bibcode:2018MNRAS.474.2987H, doi:10.1093/mnras/stx2943.
  5. Samus', N. N; et al. (2017), "General catalogue of variable stars", Astronomy Reports, GCVS 5.1, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  6. Crowther, Paul A.; Rate, Gemma (2020), "Unlocking Galactic Wolf–Rayet stars with Gaia DR2 – I. Distances and absolute magnitudes", Monthly Notices of the Royal Astronomical Society, 493 (1): 1512–1529, arXiv:1912.10125, Bibcode:2020MNRAS.493.1512R, doi:10.1093/mnras/stz3614.
  7. Hohle, M. M.; et al. (2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355, S2CID 111387483.
  8. Vanbeveren, D.; et al. (2018), "Spin rates and spin evolution of O components in WR+O binaries", Astronomy & Astrophysics, 615: A65, arXiv:1711.05989, Bibcode:2018A&A...615A..65V, doi:10.1051/0004-6361/201732212, S2CID 119058832.
  9. Wright, Candace O.; et al. (2003), "The Tycho-2 Spectral Type Catalog", The Astronomical Journal, 125 (1): 359, Bibcode:2003AJ....125..359W, doi:10.1086/345511.
  10. "CV Ser", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2022-03-15.
  11. Forbes, Douglas (November 2000), "The Serpens OB2 Association and Its Thermal "Chimney"", The Astronomical Journal, 120 (5): 2594–2608, Bibcode:2000AJ....120.2594F, doi:10.1086/316822.
  12. Fleming, M. (May 1892), "Stars having peculiar spectra", Astronomy and Astro-Physics, 11: 418–419, Bibcode:1892AstAp..11..418F.
  13. Hiltner, W. A. (November 1945), "The Wolf-Rayet Spectroscopic Binary HD 168206", Astrophysical Journal, 102: 492, Bibcode:1945ApJ...102..492H, doi:10.1086/144777.
  14. Gaposchkin, S. (1949), "HD 168206 = CV Serpentis", Peremennye Zvezdy (in Russian), 7: 36–37, Bibcode:1949PZ......7...36G.
  15. Hjellming, R. M.; Hiltner, W. A. (May 1963), "Light-Curves for Two Wolf-Rayet Binaries: CV SER and HD 211853", Astrophysical Journal, 137: 1080, Bibcode:1963ApJ...137.1080H, doi:10.1086/147586.
  16. Stępień, K. (1970), "CV Ser - A Peculiar Wolf-Rayet Binary", Acta Astronomica, 20: 13, Bibcode:1970AcA....20...13S.
  17. Kuhi, L. V.; Schweizer, F. (June 1970), "CV Serpentis has Stopped ECLIPSING!", Astrophysical Journal, 160: L185, Bibcode:1970ApJ...160L.185K, doi:10.1086/180556.
  18. Gonzalez, J.; Rosado, M. (May 1984), "Discovery of a double shell around the binary system CV Ser", Astronomy and Astrophysics, 134: L21–L23, Bibcode:1984A&A...134L..21G.
  19. Lipunova, N. A. (February 1985), "The Variability of the Lightcurve of the Wolf-Rayet Eclipsing Binary CV Serpentis", Astrophysics and Space Science, 109 (1): 57–62, Bibcode:1985Ap&SS.109...57L, doi:10.1007/BF00651013, S2CID 120138431.
  20. Antokhin, I. I.; et al. (2000), Lamers, Henny; Sapar, Arved (eds.), "Modeling the Spectra of Colliding Winds in the Wolf-Rayet WC8 + 08-9 Binary CV Ser", Thermal and Ionization Aspects of Flows from Hot Stars, ASP Conference Series, vol. 204, p. 295, Bibcode:2000ASPC..204..295A, ISBN 1-58381-031-5.
  21. Sen, K.; et al. (2021), "X-ray emission from BH+O star binaries expected to descend from the observed galactic WR+O binaries", Astronomy & Astrophysics, 652: A138, arXiv:2106.01395, Bibcode:2021A&A...652A.138S, doi:10.1051/0004-6361/202141214, S2CID 235313547.
  22. Shara, Michael M.; et al. (2022), "A speckle-imaging search for close and very faint companions to the nearest and brightest Wolf–Rayet stars", Monthly Notices of the Royal Astronomical Society, 509 (2): 2897–2907, doi:10.1093/mnras/stab2666.

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