In 1972, T. Lloyd-Evans and associates found the star's prominent bands of C2, CH, and CN varied with the Cepheid phase, being strongest at minimum. They suggested a large overabundance of carbon in the star's atmosphere.[10] Chemical analysis of the atmosphere in 1979 showed a metallicity close to solar, with an enhancement of carbon and nitrogen. It was proposed that V553 Cen is an evolved RR Lyrae variable and is now positioned above the horizontal branch on the HR diagram.[11] V553 Cen is classified as a BL Herculis variable, being a low–mass type II Cepheid with a period between 1 to 6 d. As with other variables of this type, it displays a secondary bump on its light curve.[5] It is a member of a small group of carbon Cepheids, and is one of the brightest stars of that type.[12]
V553 Cen does not appear to have a companion.[13] From the luminosity and shape of the light curve, stellar models from 1981 suggest a mass equal to 49% of the Sun's with 9.9 times the radius of the Sun.[5] Further analysis of the spectrum showed that oxygen is not enhanced, but sodium may be moderately enhanced.[12] There is no evidence of s-process enhancement of elements. Instead, the abundance peculiarities are the result of nuclear reaction sequences followed by dredge-up.[13] In particular, these are the product of triple-α, CN, ON, and perhaps some Ne–Na reactions.[12]
^ abcdPetersen, J. O. (March 1981), "V553 Centauri and a progression of bumps in BL Herculis light curves", Astronomy and Astrophysics, 96: 146–150, Bibcode:1981A&A....96..146P.
^Lloyd Evans, T.; et al. (1972), "V553 Centauri: a type II cepheid with an overabundance of carbon", Monthly Notices of the Royal Astronomical Society, 159: 67, Bibcode:1972MNRAS.159...67L, doi:10.1093/mnras/159.1.67.
^Cotrell, P. L. (October 1979), "Carbon and nitrogen abundances in the carbon-rich Cepheid V553 Centauri", Monthly Notices of the Royal Astronomical Society, 189: 13–25, Bibcode:1979MNRAS.189...13C, doi:10.1093/mnras/189.1.13.
^ abcdWallerstein, George; Gonzalez, Guillermo (October 1996), "The carbon Cepheid V553 Cen: evidence of triple-alpha and CNO cycling", Monthly Notices of the Royal Astronomical Society, 282 (4): 1236–1246, Bibcode:1996MNRAS.282.1236W, doi:10.1093/mnras/282.4.1236.
^ abWallerstein, G.; Gonzalez, G. (1998), Bradley, Paul A.; Guzik, Joyce A. (eds.), "V553 Cen and the Carbon Cepheids", A Half Century of Stellar Pulsation Interpretation: A Tribute to Arthur N. Cox; proceedings of a Conference held in Los Alamos, NM 16-20 June 1997, ASP Conference Series, vol. 135, p. 36, Bibcode:1998ASPC..135...36W.
Further reading
Galazutdinov, G. A.; Klochkova, V. G. (1995), "Spectroscopy of Selected Pulsating Stars: the Anomalous Variable V351 CEP", Astronomical and Astrophysical Transactions, 8 (3): 227–237, Bibcode:1995A&AT....8..227G, doi:10.1080/10556799508203309.
Wallerstein, G.; et al. (February 1979), "The chemical composition and luminosity of the CH-type cepheid, V553 Centauri", Publications of the Astronomical Society of the Pacific, 91: 47–52, Bibcode:1979PASP...91...47W, doi:10.1086/130438.
Landolt, A. U. (June 1975), "UBVRI photometry of V553 Centauri", Publications of the Astronomical Society of the Pacific, 87: 373–377, Bibcode:1975PASP...87..373L, doi:10.1086/129777.
Wisse, P. N. J.; Wisse, M. (1970), "Some Observations of the Anomalous Cepheid V553 Centauri", Monthly Notes of the Astronomical Society of Southern Africa, 29: 151, Bibcode:1970MNSSA..29..151W.