Can I read Flash Mixing on the White Dwarf Cooling Curve: Spectroscopic Confirmation in NGC 2808 on EtoBox?

Flash Mixing on the White Dwarf Cooling Curve: Spectroscopic Confirmation in NGC 2808 by Brown, Thomas M.; Lanz, Thierry; Sweigart, Allen V.; Cracraft, Misty; Hubeny, Ivan; Landsman, Wayne B. is a scholarly article available to read on EtoBox.

What is Flash Mixing on the White Dwarf Cooling Curve: Spectroscopic Confirmation in NGC 2808 about?

[Abridged] We present new HST FUV spectroscopy of 24 hot evolved stars in NGC2808, a massive globular cluster with a large population of "blue-hook" (BHk) stars. The BHk stars are found in UV color-magnitude diagrams of the most massive globular clusters, where they fall at luminosities immediately below the hot end of the horizontal branch (HB), in a region of the HR diagram unexplained by canonical stellar evolution theory. Using new evolutionary and atmospheric models, we have shown that these subluminous HB stars are very likely the progeny of stars that undergo extensive internal mixing during a late He-core flash on the white dwarf cooling curve. This flash mixing leads to hotter temperatures and an enormous enhancement of the surface He and C; these hotter temperatures, together with the decrease in H opacity shortward of the Lyman limit, make the BHk stars brighter in the EUV while appearing subluminous in the UV and optical. Our FUV spectroscopy demonstrates that, relative to normal HB stars at the same color, the BHk stars of NGC2808 are hotter and greatly enhanced in He and C, thus providing unambiguous evidence of flash mixing. Although the C abundance in the BHk stars

Author

Brown, Thomas M.; Lanz, Thierry; Sweigart, Allen V.; Cracraft, Misty; Hubeny, Ivan; Landsman, Wayne B.

Published

2012

Language

EN