Weak G-band star

Weak G-band stars belong to the group of chemically peculiar stars . They are yellow giants of spectral class G or K with a weak or undetectable Fraunhofer line G at 4300 Angstroms . The weak G-band is a consequence of a lower abundance of carbon , which form the CH bands in chemically normal yellow giants. In addition, the weak G-band stars show an unusual ratio of carbon isotopes ¹² C / ¹³ C and a high incidence of lithium .

The weak G-band stars are not part of binary star systems like the barium stars , which is why a mass transfer between the components is excluded as the cause of the unusual chemical composition. The stars are rather poor in metal and seem to have an unusually high mass of 2.5 to 5 solar masses . According to simulation calculations, the helium-burning giants could be formerly fast rotating main sequence stars which, due to a strong mixing, have developed differently chemically, since they remain longer in the state of nuclear hydrogen burning .

Examples

HD 165634
HD 26575
HD 36552

Individual evidence

^ Jens Adamczak and David L. Lambert: Atmospheric composition of weak G band stars: CNO and Li abundances . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1301.5571 .
^ A. Palacios et al .: Weak G-band stars on the HR Diagram: Clues to the origin of Li anomaly . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1112.2973 .

[1] Jens Adamczak and David L. Lambert: Atmospheric composition of weak G band stars: CNO and Li abundances . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1301.5571 .

[2] A. Palacios et al .: Weak G-band stars on the HR Diagram: Clues to the origin of Li anomaly . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1112.2973 .