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Radiation-pressure-driven sub-Keplerian rotation of the disc around the AGB star L2 Pup

Published version
Peer-reviewed

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Abstract

AbstractWe study the sub-Keplerian rotation and dust content of the circumstellar material around the asymptotic giant branch (AGB) star L2 Puppis. We find that the thermal pressure gradient alone cannot explain the observed rotation profile. We find that there is a family of possible dust populations for which radiation pressure can drive the observed sub-Keplerian rotation. This set of solutions is further constrained by the spectral energy distribution (SED) of the system, and we find that a dust-to-gas mass ratio of ∼10−3 and a maximum grain size that decreases radially outwards can satisfy both the rotation curve and SED. These dust populations are dynamically tightly coupled to the gas azimuthally. However, grains larger than ∼ 0.5 μm are driven outwards radially by radiation pressure at velocities ∼5 km s−1, which implies a dust replenishment rate of ∼3 × 10−9 M⊙ yr−1. This replenishment rate is consistent with observational estimates to within uncertainties. Coupling between the radial motion of the dust and gas is weak and hence the gas does not share in this rapid outward motion. Overall, we conclude that radiation pressure is a capable and necessary mechanism to explain the observed rotation profile of L2 Pup, and offers other additional constraints on the dust properties.

Description

Journal Title

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Conference Name

Journal ISSN

0035-8711
1365-2966

Volume Title

473

Publisher

Oxford University Press (OUP)

Rights and licensing

Except where otherwised noted, this item's license is described as All rights reserved
Sponsorship
European Research Council (341137)
Science and Technology Facilities Council (ST/N000927/1)
Science and Technology Facilities Council (ST/H008586/1)
Science and Technology Facilities Council (ST/K00333X/1)
Science and Technology Facilities Council (ST/M007065/1)
Science and Technology Facilities Council (ST/J005673/1)