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Astronomy 500 November 7, 2008

The Carbon Stars. Astronomy 500 November 7, 2008. The Classical Carbon Star. Stars with luminosities corresponding to late-G, K and M giants but with over abundances of carbon. Come in several flavors: C-R, C-N, C-J,C-H, and C-Hd

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Astronomy 500 November 7, 2008

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  1. The Carbon Stars Astronomy 500 November 7, 2008

  2. The Classical Carbon Star • Stars with luminosities corresponding to late-G, K and M giants but with over abundances of carbon. • Come in several flavors: C-R, C-N, C-J,C-H, and C-Hd • Although most are giants or sub-giants, there are also dwarf carbon stars: dC

  3. Collegio Romano Father Angelo Secchi History Circa 1868 +

  4. Spectral Classification System • Originally devised by Keenan and Morgan in 1941 • Revised by Keenan in 1993 to include several classes of carbon stars • Numbers correspond to the strength of the absorption bands

  5. The C-R Stars • Warmest of the carbon stars and most “blue” • Characterized by their prominent Swan bands (C2) at λ4737 and λ5765

  6. The C-N Stars • Generally redder than C-R stars with weaker Swan bands • S-process elements are more prominent

  7. The C-J Stars • Have a remarkably large abundance of 13C (the 12C/13C ratio is less than 13 as compared to 92 in our solar system) • Have significant SiC2 while weaker Ba II and Sr I lines.

  8. The C-H Stars • Dominated by bands of CH in the blue region of the spectrum • Strong (sometimes saturated) G-band which is formed from the Q-branches of the CH (A-X 0-0 and 1-1) bands located near λ4300

  9. The C-Hd Stars • Hydrogen deficient carbon stars with almost complete absence of the G-band and other hydrogen lines. • Stronger than normal of CN and C2

  10. The dC stars • The discovery of the first dwarf carbon star, G77-61, seemed to be a fluke • Characterized by the same lines as their giant cousins but extremely low luminosities • Some have a severe metal deficiency of almost -5.6 dex

  11. References • Wallerstein G, Knapp G. 1998. Annu. Rev. Astrophys.36:369-433 • Dahn CC, et al. 1977. Ap. J. 216:757 • Gray, R.O., Corbally, C.J.; Stellar Spectral Classification. Princeton University Press, Priceton, NJ, 2009. 306-321 • http://www.ucea.it/PreScen/Astronomia.htm • http://www.sil.si.edu/digitalcollections/hst/scientific-identity/CF/display_results.cfm?alpha_sort=s

  12. What does not exist looks so handsome What does exist, where is it? An ocean is hidden. All we see is foam, shapes of dust, spinning, tall as minarets, but I want the wind Dust can’t rise up without wind, I know, but can’t I understand this by some way other than induction? Invisible ocean, wind. Visible foam and dust: This is speech. Why can’t I hear thought? These eyes were born asleep. Why organize a Universe this way? Jalal al-Din Rumi (1207-1273)

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