Wyatt, M. C.
Dent, W. R. F.
Hughes, A. M.
AffiliationUniv Arizona, Dept Astron, Steward Observ
stars: individual: HD 181327
radio continuum: planetary systems
MetadataShow full item record
PublisherOXFORD UNIV PRESS
CitationExocometary gas in the HD 181327 debris ring 2016, 460 (3):2933 Monthly Notices of the Royal Astronomical Society
Rights© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
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AbstractAn increasing number of observations have shown that gaseous debris discs are not an exception. However, until now, we only knew of cases around A stars. Here we present the first detection of (CO)-C-12 (2-1) disc emission around an F star, HD 181327, obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with radiative transfer calculations, we study the dust and CO mass distribution. We find the dust is distributed in a ring with a radius of 86.0 +/- 0.4 au and a radial width of 23.2 +/- 1.0 au. At this frequency, the ring radius is smaller than in the optical, revealing grain size segregation expected due to radiation pressure. We also report on the detection of low-level continuum emission beyond the main ring out to similar to 200 au. We model the CO emission in the non-local thermodynamic equilibrium regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging between 1.2 x 10(-6) M-aS center dot and 2.9 x 10(-6) M-aS center dot, depending on the gas kinetic temperature and collisional partners densities. The CO densities and location suggest a secondary origin, i.e. released from icy planetesimals in the ring. We derive a CO+CO2 cometary composition that is consistent with Solar system comets. Due to the low gas densities, it is unlikely that the gas is shaping the dust distribution.
VersionFinal published version
SponsorsEuropean Union through ERC ; Millennium Nucleus (Chilean Ministry of Economy) [RC130007]; FONDECYT [1130949, 3140601]; Royal Society