CLOSE TO THE DREDGE: PRECISE X-RAY C AND N ABUNDANCES IN {lambda} ANDROMEDA AND ITS PRECOCIOUS RED GIANT BRANCH MIXING PROBLEM

Journal Article · Tue Nov 15 00:00:00 EST 2011 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/142/5/144· OSTI ID:21582802

Drake, Jeremy J; Ball, B ^[1]; Eldridge, John J ^[2]; Ness, J -U ^[3]

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1. Smithsonian Astrophysical Observatory, MS-3, 60 Garden Street, Cambridge, MA 02138 (United States)
2. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
3. European Space Agency, XMM-Newton Observatory SOC, SRE-OAX, Apartado 78, 28691 Villanueva de la Canada, Madrid (Spain)

Chandra LETG+HRC-S and XMM-Newton RGS spectra of H-like C and N lines formed in the corona of the primary star of the RS CVn-type binary {lambda} And, a mildly metal-poor G8 III-IV first ascent giant that completed dredge-up {approx}50 Myr ago, have been used to make a precise measurement of its surface C/N ratio. We obtain the formal result [C/N] = 0.03 {+-} 0.07, which is typical of old disk giants and in agreement with standard dredge-up theory for stars {approx}< 1 M{sub sun}. In contrast, these stars as a group, including {lambda} And, have {sup 12}C/{sup 13}C {approx}< 20, which is much lower than standard model predictions. We show that the abundances of the old disk giants are consistent with models including thermohaline mixing that begins at the red giant branch luminosity function 'bump'. Instead, {lambda} And indicates that the {sup 12}C/{sup 13}C anomaly can be present immediately following dredge-up, contrary to current models of extra mixing on the red giant branch. In the context of other recent C and N abundance results for RS CVn-type binaries it seems likely that the anomaly is associated with either strong magnetic activity, fast rotation, or both, rather than close binarity itself.

• OSTI ID: 21582802
• Journal Information: Astronomical Journal (New York, N.Y. Online), Vol. 142, Issue 5; Other Information: DOI: 10.1088/0004-6256/142/5/144; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
CARBON 12
CARBON 13
LUMINOSITY
METALS
ROTATION
STAR EVOLUTION
STARS
X RADIATION
CARBON ISOTOPES
ELECTROMAGNETIC RADIATION
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
EVOLUTION
IONIZING RADIATIONS
ISOTOPES
LIGHT NUCLEI
MOTION
NUCLEI
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
STABLE ISOTOPES