ROCKY EXTRASOLAR PLANETARY COMPOSITIONS DERIVED FROM EXTERNALLY POLLUTED WHITE DWARFS
- Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1562 (United States)
- Institut fuer Theoretische Physik und Astrophysik, University of Kiel, D-24098 Kiel (Germany)
We report Keck High Resolution Echelle Spectrometer data and model atmosphere analysis of two helium-dominated white dwarfs, PG1225-079 and HS2253+8023, whose heavy pollutions most likely derive from the accretion of terrestrial-type planet(esimal)s. For each system, the minimum accreted mass is {approx}10{sup 22} g, that of a large asteroid. In PG1225-079, Mg, Cr, Mn, Fe, and Ni have abundance ratios similar to bulk Earth values, while we measure four refractory elements, Ca, Sc, Ti, and V, all at a factor of {approx}2-3 higher abundance than in the bulk Earth. For HS2253+8023 the swallowed material was compositionally similar to bulk Earth in being more than 85% by mass in the major element species, O, Mg, Si, and Fe, and with abundances in the distinctive proportions of mineral oxides-compelling evidence for an origin in a rocky parent body. Including previous studies we now know of four heavily polluted white dwarfs where the measured oxygen and hydrogen are consistent with the view that the parents' bodies formed with little ice, interior to any snow line in their nebular environments. The growing handful of polluted white dwarf systems with comprehensive abundance measurements form a baseline for characterizing rocky exoplanet compositions that can be compared with bulk Earth.
- OSTI ID:
- 21612741
- Journal Information:
- Astrophysical Journal, Vol. 741, Issue 1; Other Information: DOI: 10.1088/0004-637X/741/1/64; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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