Resolved millimeter-dust continuum cavity around the very low mass young star CIDA 1

¹ Department of Astronomy/Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson AZ 85721, USA
e-mail: pinilla@email.arizona.edu
² INAF-Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
³ Dublin Institute for Advanced Studies, School of Cosmic Physics, 31 Fitzwilliam Place, Dublin 2, Ireland
⁴ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
⁵ Department of Physics and Astronomy, California State University Northridge, 18111 Nordhoff St, Northridge CA 91130, USA
⁶ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena CA 91109, USA
⁷ SUPA, School of Physics & Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, UK

Received: 23 January 2018
Accepted: 23 April 2018

Abstract

Context. Transition disks (TDs) are circumstellar disks with inner regions highly depleted in dust. TDs are observed in a small fraction of disk-bearing objects at ages of 1–10 Myr. They are important laboratories to study evolutionary effects in disks, from photoevaporation to planet–disk interactions.

Aim. We report the discovery of a large inner dust-empty region in the disk around the very low mass star CIDA 1 (M_⋆ ~ 0.1−0.2 M_⊙). Methods. We used ALMA continuum observations at 887 µm, which provide a spatial resolution of 0″.21 × 0″.12 (~15 × 8 au in radius at 140 pc).

Results. The data show a dusty ring with a clear cavity of radius ~20 au, the typical characteristic of a TD. The emission in the ring is well described by a narrow Gaussian profile. The dust mass in the disk is ~17 M_⊕. CIDA 1 is one of the lowest mass stars with a clearly detected millimeter cavity. When compared to objects of similar stellar mass, it has a relatively massive dusty disk (less than ~5% of Taurus Class II disks in Taurus have a ratio of M_disk/M_⋆ larger than CIDA 1) and a very high mass accretion rate (CIDA 1 is a disk with one of the lowest values of M_disk/Ṁ ever observed). In light of these unusual parameters, we discuss a number of possible mechanisms that can be responsible for the formation of the dust cavity (e.g. photoevaporation, dead zones, embedded planets, close binary). We find that an embedded planet of a Saturn mass or a close binary are the most likely possibilities.