"Barium stars are spectral class G to K giants, whose spectra indicate an overabundance of s-process elements by the presence of singly ionized barium, Ba II, at λ 455.4 nm. Barium stars also show enhanced spectral features of carbon, the bands of the molecules CH, CN and C2."[1]

Binary stars edit

"Observational studies of their radial velocity suggested that all barium stars are binary stars[2][3][4] Observations in the ultraviolet using [the] International Ultraviolet Explorer detected white dwarfs in some barium star systems."[1]

Theoretical barium stars edit

"Barium stars are believed to be the result of mass transfer in a binary star system. The mass transfer occurred when the presently-observed giant star was on the main sequence. Its companion, the donor star, was a carbon star on the asymptotic giant branch (AGB), and had produced carbon and s-process elements in its interior. These nuclear fusion products were mixed by convection to its surface. Some of that matter "polluted" the surface layers of the main sequence star as the donor star lost mass at the end of its AGB evolution, and it subsequently evolved to become a white dwarf. We are observing these systems an indeterminate amount of time after the mass transfer event, when the donor star has long been a white dwarf, and the "polluted" recipient star has evolved to become a red giant.[5][6]"[1]

Stellar surface fusion edit

Barium stars exhibit carbon and s-process elements at their surfaces suggesting surface fusion possible during mass transfer or without it.

Main-sequence stars edit

"The mass transfer hypothesis predicts that there should be main sequence stars with barium star spectral peculiarities. At least one such star, HR 107, is known.[7]"[1]

"Prototypical barium stars include zeta Capricorni, HR 774, and HR 4474."[1]

See also edit

References edit

  1. 1.0 1.1 1.2 1.3 1.4 "Barium star". San Francisco, California: Wikimedia Foundation, Inc. February 25, 2013. Retrieved 2013-09-22.
  2. McClure et al., Astrophysical Journal Letters, vol. 238, L35-L38, May 1980
  3. McClure, R.D. & Woodsworth, A.W. Astrophysical Journal, vol. 352, pp. 709–723, April 1990.
  4. Jorissen, A. & Mayor, M. Astronomy & Astrophysics, vol. 198, pp. 187–199, June 1988
  5. McClure, R. Journal of the Royals Astronomical Society of Canada, vol 79, pp. 277–293, Dec. 1985
  6. Boffin, H. M. J. & Jorissen, A., Astronomy & Astrophysics, vol. 205, pp. 155–163, October 1988
  7. Tomkin, J., Lambert, D.L., Edvardsson, B., Gustafsson, B., & Nissen, P.E., Astronomy & Astrophysics, vol 219, pp. L15-L18, July 1989

External links edit