ON THE UNUSUAL GAS COMPOSITION IN THE [beta] PICTORIS DEBRIS DISK

• Published in: The Astrophysical journal Vol. 762; no. 2; pp. 1 - 9
• Main Authors: Xie, Ji-Wei, Brandeker, Alexis, Wu, Yanqin
• Format: Journal Article
• Language: English
• Published: United States 10.01.2013
• Subjects: Abundance; ASTRONOMY; ASTROPHYSICS; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BLOWOUTS; CALCIUM; CARBON; COMPARATIVE EVALUATIONS; COSMIC DUST; COSMIC GASES; COUPLING; Debris; DEGASSING; Disks; ELEMENT ABUNDANCE; Enrichment; Gas composition; Grains; INTERSTELLAR GRAINS; IRON; OXYGEN; PLANETS; PROTOPLANETS; SODIUM; STARS; VISCOSITY
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/762/2/114

The metallic gas associated with the [beta] Pic debris disk is not believed to be primordial, but arises from the destruction of dust grains. Recent observations have shown that carbon and oxygen in this gas are exceptionally overabundant compared to other elements, by some 400 times. We study the origin of this enrichment under two opposing hypotheses: preferential production, where the gas is produced with the observed unusual abundance (as may happen if gas is produced by photodesorption from C/O-rich icy grains), and preferential depletion, where the gas evolves to the observed state from an original solar abundance (if outgassing occurs under high-speed collisions) under a number of dynamical processes. We include in our study the following processes: radiative blowout of metallic elements, dynamical coupling between different species, and viscous accretion onto the star. We find that, if gas viscosity is sufficiently low (the conventional [alpha] parameter [lap]10 super(-3)), differential blowout dominates.