Volume 649, May 2021
|Number of page(s)||13|
|Section||Interstellar and circumstellar matter|
|Published online||27 May 2021|
A bright inner disk and structures in the transition disk around the very low-mass star CIDA 1
Max-Planck-Institut für Astronomie,
2 Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK
3 Unidad Mixta Internacional Franco-Chilena de Astronomía, CNRS/INSU UMI 3386, Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile
4 Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
5 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
6 Dublin Institute for Advanced Studies, School of Cosmic Physics, 31 Fitzwilliam Place, Dublin 2, Ireland
7 University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München, Scheinerstr. 1, 81679 Munich, Germany
8 Institute of Astronomy, University of Cambridge, Madingley Road, CB3 0HA Cambridge, UK
9 Department of Physics and Astronomy, California State University Northridge, 18111 Nordhoff Street, Northridge, CA 91130, USA
10 INAF – Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
Accepted: 17 March 2021
The frequency of Earth-sized planets in habitable zones appears to be higher around M-dwarfs, making these systems exciting laboratories to investigate planet formation. Observations of protoplanetary disks around very low-mass stars and brown dwarfs remain challenging and little is known about their properties. The disk around CIDA 1 (~0.1–0.2 M⊙) is one of the very few known disks that host a large cavity (20 au radius in size) around a very low-mass star. We present new ALMA observations at Band 7 (0.9 mm) and Band 4 (2.1 mm) of CIDA 1 with a resolution of ~0.05″ × 0.034″. These new ALMA observations reveal a very bright and unresolved inner disk, a shallow spectral index of the dust emission (~2), and a complex morphology of a ring located at 20 au. We also present X-shooter (VLT) observations that confirm the high accretion rate of CIDA 1 of Ṁacc = 1.4 × 10−8 M⊙ yr−1. This high value of Ṁacc, the observed inner disk, and the large cavity of 20 au exclude models of photo-evaporation to explain the observed cavity. When comparing these observations with models that combine planet–disk interaction, dust evolution, and radiative transfer, we exclude planets more massive than 0.5 MJup as the potential origin of the large cavity because with these it is difficult to maintain a long-lived and bright inner disk. Even in this planet mass regime, an additional physical process may be needed to stop the particles from migrating inwards and to maintain a bright inner disk on timescales of millions of years. Such mechanisms include a trap formed by a very close-in extra planet or the inner edge of a dead zone. The low spectral index of the disk around CIDA 1 is difficult to explain and challenges our current dust evolution models, in particular processes like fragmentation, growth, and diffusion of particles inside pressure bumps.
Key words: planets and satellites: formation / protoplanetary disks / accretion, accretion disks
© P. Pinilla et al. 2021
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Open Access funding provided by Max Planck Society.
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