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Herschel detects oxygen in the Pictoris debris disk

Brandeker, A., Cataldi, G., Olofsson, G., Vandenbussche, B., Acke, B., Barlow, M. J., Blommaert, J. A. D. L., Cohen, M., Dent, W. R. F., Dominik, C., Di Francesco, J., Fridlund, M., Gear, Walter, Glauser, A. M., Greaves, Jane, Harvey, P. M., Heras, A. M., Hogerheijde, M. R., Holland, W. S., Huygen, R., Ivison, R. J., Leeks, S. J., Lim, T. L., Liseau, R., Matthews, B. C., Pantin, E., Pilbratt, G. L., Royer, P., Sibthorpe, B., Waelkens, C. and Walker, H. J. 2016. Herschel detects oxygen in the Pictoris debris disk. Astronomy & Astrophysics 591 , A27. 10.1051/0004-6361/201628395

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Abstract

he young star β Pictoris is well known for its dusty debris disk produced through collisional grinding of planetesimals, kilometre-sized bodies in orbit around the star. In addition to dust, small amounts of gas are also known to orbit the star; this gas is likely the result of vaporisation of violently colliding dust grains. The disk is seen edge on and from previous absorption spectroscopy we know that the gas is very rich in carbon relative to other elements. The oxygen content has been more difficult to assess, however, with early estimates finding very little oxygen in the gas at a C/O ratio that is 20 × higher than the cosmic value. A C/O ratio that high is difficult to explain and would have far-reaching consequences for planet formation. Here we report on observations by the far-infrared space telescope Herschel, using PACS, of emission lines from ionised carbon and neutral oxygen. The detected emission from C+ is consistent withthat previously reported observed by the HIFI instrument on Herschel, while the emission from O is hard to explain without assuming a higher density region in the disk, perhaps in the shape of a clump or a dense torus required to sufficiently excite the O atoms. A possible scenario is that the C/O gas is produced by the same process responsible for the CO clump recently observed by the Atacama Large Millimeter/submillimeter Array in the disk and that the redistribution of the gas takes longer than previously assumed. A more detailed estimate of the C/O ratio and the mass of O will have to await better constraints on the C/O gas spatial distribution.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Publisher: EDP Sciences
ISSN: 0004-6361
Date of First Compliant Deposit: 16 August 2017
Date of Acceptance: 25 April 2016
Last Modified: 18 Aug 2017 12:42
URI: http://orca.cf.ac.uk/id/eprint/103663

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