CHEMICAL ABUNDANCES IN THE EXTERNALLY POLLUTED WHITE DWARF GD 40: EVIDENCE OF A ROCKY EXTRASOLAR MINOR PLANET

Journal Article · Mon Feb 01 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/709/2/950· OSTI ID:21392294

Klein, B; Jura, M; Zuckerman, B; Melis, C ^[1]; Koester, D ^[2]

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1. Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1562 (United States)
2. Institut fur Theoretische Physik und Astrophysik, University of Kiel, 24098 Kiel (Germany)

We present Keck/High Resolution Echelle Spectrometer data with model atmosphere analysis of the helium-dominated polluted white dwarf GD 40, in which we measure atmospheric abundances relative to helium of nine elements: H, O, Mg, Si, Ca, Ti, Cr, Mn, and Fe. Apart from hydrogen, whose association with the other contaminants is uncertain, this material most likely accreted from GD 40's circumstellar dust disk whose existence is demonstrated by excess infrared emission. The data are best explained by accretion of rocky planetary material, in which heavy elements are largely contained within oxides, derived from a tidally disrupted minor planet at least the mass of Juno, and probably as massive as Vesta. The relatively low hydrogen abundance sets an upper limit of 10% water by mass in the inferred parent body, and the relatively high abundances of refractory elements, Ca and Ti, may indicate high-temperature processing. While the overall constitution of the parent body is similar to the bulk Earth being over 85% by mass composed of oxygen, magnesium, silicon, and iron, we find n(Si)/n(Mg) = 0.30 +- 0.11, significantly smaller than the ratio near unity for the bulk Earth, chondrites, the Sun, and nearby stars. This result suggests that differentiation occurred within the parent body.

• OSTI ID: 21392294
• Journal Information: Astrophysical Journal, Vol. 709, Issue 2; Other Information: DOI: 10.1088/0004-637X/709/2/950; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
ATMOSPHERES
CHONDRITES
DUSTS
HELIUM
IRON
MAGNESIUM
MASS
OXIDES
OXYGEN
PLANETS
SILICON
SPECTROMETERS
SUN
WATER
WHITE DWARF STARS
ALKALINE EARTH METALS
CHALCOGENIDES
DWARF STARS
ELEMENTS
FLUIDS
GASES
HYDROGEN COMPOUNDS
MAIN SEQUENCE STARS
MEASURING INSTRUMENTS
METALS
METEORITES
NONMETALS
OXYGEN COMPOUNDS
RARE GASES
SEMIMETALS
STARS
STONE METEORITES
TRANSITION ELEMENTS