2017A&A...601A...5H

The circumstellar environment of the AGB star L₂ Puppis was observed with ALMA in cycle 3, with a resolution of 15x18mas. The molecular emission shows a differentially rotating disk, inclined to a nearly edge-on position. In the first paper in this series (Kervella et al., 2016A&A...596A..92K, Paper I) the molecular emission was analysed to accurately deduce the motion of the gas in the equatorial regions of the disk. In this work we model the optically thick ¹²CO J=3-2 and the optically thin ¹³CO J=3-2 rotational transition to constrain the physical conditions in the disk. To realise this effort we make use of the 3D NLTE radiative transfer code LIME. The temperature structure and velocity structure show a high degree of complexity, both radially and vertically. The radial H₂ density profile in the disk plane is characterised by a power law with a slope of -3.1. We find a ¹²CO over ¹³CO abundance ratio of 10 inside the disk. Finally, estimations of the angular momentum in the disk surpass the expected available angular momentum of the star, strongly supporting the indirect detection of a compact binary companion reported in Paper I. We estimate the mass of the companion to be around 1 Jupiter mass.