A kinematically detected planet candidate in a transition disk

Astronomy and Astrophysics, vol. 670, pp. L1

Abstract

Context. Transition disks are protoplanetary disks with inner cavities possibly cleared by massive companions. Observing them at high resolution is ideal for mapping their velocity structure and probing companion–disk interactions. Aims. We present Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 dust and gas observations of the transition disk around RXJ1604.3–2130 A, known to feature nearly symmetric shadows in scattered light, and aim to search for non-Keplerian features. Methods. We studied the 12 CO line channel maps and moment maps of the line-of-sight velocity and peak intensity. We fitted a Keplerian model of the channel-by-channel emission to study line profile differences and produced deprojected radial profiles for all velocity components. Results. The 12 CO emission is detected out to R ∼ 1.8″ (265 au). It shows a cavity inward of 0.39″ (56 au) and within the dust continuum ring (at ∼0.56″, i.e., 81 au). Azimuthal brightness variations in the 12 CO line and dust continuum are broadly aligned with the shadows detected in scattered-light observations. We find a strong localized non-Keplerian feature toward the west within the continuum ring (at R = 41 ± 10 au and PA = 280 ± 2°). It accounts for Δ v ϕ / v kep ∼ 0.4 or Δ v z / v kep ∼ 0.04, depending on if the perturbation is in the rotational or vertical direction. A tightly wound spiral is also detected and extends over 300° in azimuth, possibly connected to the localized non-Keplerian feature. Finally, a bending of the iso-velocity contours within the gas cavity indicates a highly perturbed inner region, possibly related to the presence of a misaligned inner disk. Conclusions. While broadly aligned with the scattered-light shadows, the localized non-Keplerian feature cannot be solely due to changes in temperature. Instead, we interpret the kinematical feature as tracing a massive companion located at the edge of the dust continuum ring. We speculate that the spiral is caused by buoyancy resonances driven by planet–disk interactions. However, this potential planet at ∼41 au cannot explain the gas-depleted cavity, the low accretion rate, and the misaligned inner disk, which suggests the presence of another companion closer in.

Authors 13

1. Jochen Stadler

   Centre National de la Recherche Scientifique · Université Côte d'Azur · Institut de Planétologie et d'Astrophysique de Grenoble · Lagrange Laboratory · Observatoire de la Côte d’Azur · Université Grenoble Alpes

   Affiliation as printed

   Laboratoire Lagrange, Université Côte d’Azur, CNRS, Observatoire de la Côte d’Azur, 06304 Nice, France

   Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France

   Laboratoire Lagrange, Université Côte d'Azur, CNRS, Observatoire de la Côte d'Azur, 06304 Nice, France

2. M. Benisty

   Centre National de la Recherche Scientifique · Université Côte d'Azur · Institut de Planétologie et d'Astrophysique de Grenoble · Lagrange Laboratory · Observatoire de la Côte d’Azur · Université Grenoble Alpes

   Affiliation as printed

   Laboratoire Lagrange, Université Côte d’Azur, CNRS, Observatoire de la Côte d’Azur, 06304 Nice, France

   Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France

   Laboratoire Lagrange, Université Côte d'Azur, CNRS, Observatoire de la Côte d'Azur, 06304 Nice, France

3. Andrés F. Izquierdo Aachen Leiden Observatory

   Leiden University · European Southern Observatory · Leiden Observatory

   Affiliation as printed

   European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany

   Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands

4. Stefano Facchini

   University of Milan

   Affiliation as printed

   Universitá degli Studi di Milano, Via Celoria 16, 20133 Milano, Italy

5. Richard D. Teague

   Massachusetts Institute of Technology

   Affiliation as printed

   Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

6. N. T. Kurtovic

   Max Planck Institute for Astronomy

   Affiliation as printed

   Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany

7. Paola Pinilla

   University College London

   Affiliation as printed

   Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK

8. Jaehan Bae

   University of Florida

   Affiliation as printed

   Department of Astronomy, University of Florida, Gainesville, FL 32611, USA

9. Megan Ansdell

   National Aeronautics and Space Administration

   Affiliation as printed

   NASA Headquarters, 300 E Street SW, Washington, DC 20546, USA

10. Ryan A. Loomis

    National Radio Astronomy Observatory

    Affiliation as printed

    National Radio Astronomy Observatory, Charlottesville, VA 22903, USA

11. Satoshi Mayama

    The Graduate University for Advanced Studies, SOKENDAI

    Affiliation as printed

    The Graduate University for Advanced Studies, SOKENDAI, Shonan Village, Hayama, Kanagawa 240-0193, Japan

12. Laura M. Pérez

    Millenium Nucleus for Planet Formation · University of Chile

    Affiliation as printed

    Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile

    Núcleo Milenio de Formación Planetaria (NPF), Avenida España 1680, Valparaíso, Chile

13. L. Testi

    European Southern Observatory

    Affiliation as printed

    European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany