High-resolution ALMA observations of V4046Sgr: a circumbinary disc with a thin ring. (arXiv:2111.12668v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Martinez_Brunner_R/0/1/0/all/0/1">Rafael Martinez-Brunner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Casassus_S/0/1/0/all/0/1">Simon Casassus</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Perez_S/0/1/0/all/0/1">Sebasti&#xe1;n P&#xe9;rez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hales_A/0/1/0/all/0/1">Antonio Hales</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Weber_P/0/1/0/all/0/1">Philipp Weber</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Carcamo_M/0/1/0/all/0/1">Miguel Carcamo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Arce_Tord_C/0/1/0/all/0/1">Carla Arce-Tord</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cieza_L/0/1/0/all/0/1">Lucas Cieza</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Garufi_A/0/1/0/all/0/1">Antonio Garufi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marino_S/0/1/0/all/0/1">Sebasti&#xe1;n Marino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zurlo_A/0/1/0/all/0/1">Alice Zurlo</a>

The nearby V4046 Sgr spectroscopic binary hosts a gas-rich disc known for its
wide cavity and dusty ring. We present high resolution ($sim$20 mas or 1.4 au)
ALMA observations of the 1.3mm continuum of V4046 Sgr which, combined with
SPHERE–IRDIS polarised images and a well-sampled spectral energy distribution
(SED), allow us to propose a physical model using radiative transfer (RT)
predictions. The ALMA data reveal a thin ring at a radius of 13.15$pm$0.42 au
(Ring13), with a radial width of 2.46$pm$0.56 au. Ring13 is surrounded by a
$sim$10 au-wide gap, and it is flanked by a mm-bright outer ring (Ring24) with
a sharp inner edge at 24 au. Between 25 and $sim$35 au the brightness of
Ring24 is relatively flat and then breaks into a steep tail that reaches out to
$sim$60 au. In addition, central emission is detected close to the star which
we interpret as a tight circumbinary ring made of dust grains with a lower size
limit of 0.8 mm at 1.1 au. In order to reproduce the SED, the model also
requires an inner ring at $sim$5 au (Ring5) composed mainly of small dust
grains, hiding under the IRDIS coronagraph, and surrounding the inner
circumbinary disc. The surprisingly thin Ring13 is nonetheless roughly 10 times
wider than its expected vertical extent. The strong near-far disc asymmetry at
1.65 $mu$m points at a very forward-scattering phase function and requires
grain radii of no less than 0.4 $mu$m.

The nearby V4046 Sgr spectroscopic binary hosts a gas-rich disc known for its
wide cavity and dusty ring. We present high resolution ($sim$20 mas or 1.4 au)
ALMA observations of the 1.3mm continuum of V4046 Sgr which, combined with
SPHERE–IRDIS polarised images and a well-sampled spectral energy distribution
(SED), allow us to propose a physical model using radiative transfer (RT)
predictions. The ALMA data reveal a thin ring at a radius of 13.15$pm$0.42 au
(Ring13), with a radial width of 2.46$pm$0.56 au. Ring13 is surrounded by a
$sim$10 au-wide gap, and it is flanked by a mm-bright outer ring (Ring24) with
a sharp inner edge at 24 au. Between 25 and $sim$35 au the brightness of
Ring24 is relatively flat and then breaks into a steep tail that reaches out to
$sim$60 au. In addition, central emission is detected close to the star which
we interpret as a tight circumbinary ring made of dust grains with a lower size
limit of 0.8 mm at 1.1 au. In order to reproduce the SED, the model also
requires an inner ring at $sim$5 au (Ring5) composed mainly of small dust
grains, hiding under the IRDIS coronagraph, and surrounding the inner
circumbinary disc. The surprisingly thin Ring13 is nonetheless roughly 10 times
wider than its expected vertical extent. The strong near-far disc asymmetry at
1.65 $mu$m points at a very forward-scattering phase function and requires
grain radii of no less than 0.4 $mu$m.

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