Two cold belts in the debris disk around the G-type star NZ Lupi^★,★★

¹ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
e-mail: Anthony.boccaletti@obspm.fr
² CNRS, IPAG, Université Grenoble Alpes, 38000 Grenoble, France
³ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁴ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁵ European Southern Observatory, Alonso de Córdova 3107, Casilla 19001 Vitacura, Santiago 19, Chile
⁶ STAR Institute, Université de Liège, Allée du Six Août 19c, 4000 Liège, Belgium
⁷ ETH Zurich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland
⁸ SUPA, Institute for Astronomy, The University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK
⁹ Geneva Observatory, University of Geneva, Chemin des Mailettes 51, 1290 Versoix, Switzerland
¹⁰ CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, Aix-Marseille Université, 13388 Marseille, France
¹¹ CRAL, UMR 5574, CNRS, Université de Lyon, Ecole Normale Supérieure de Lyon, 46 Allée d’Italie, 69364 Lyon Cedex 07, France
¹² Department of Astronomy, University of Michigan, 1085 South University, Ann Arbor, MI 48109, USA
¹³ Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Avenue Gran Bretaña 1111, Valparaíso, Chile
¹⁴ Núcleo Milenio Formación Planetaria – NPF, Universidad de Valparaíso, Avenue Gran Bretaña 1111, Valparaíso, Chile
¹⁵ DOTA, ONERA, Université Paris Saclay, 91123 Palaiseau, France

Received: 25 January 2019
Accepted: 25 March 2019

Abstract

Context. Planetary systems hold the imprint of the formation and of the evolution of planets especially at young ages, and in particular at the stage when the gas has dissipated leaving mostly secondary dust grains. The dynamical perturbation of planets in the dust distribution can be revealed with high-contrast imaging in a variety of structures.

Aims. SPHERE, the high-contrast imaging device installed at the VLT, was designed to search for young giant planets in long period, but is also able to resolve fine details of planetary systems at the scale of astronomical units in the scattered-light regime. As a young and nearby star, NZ Lup was observed in the course of the SPHERE survey. A debris disk had been formerly identified with HST/NICMOS.

Methods. We observed this system in the near-infrared with the camera in narrow and broad band filters and with the integral field spectrograph. High contrasts are achieved by the mean of pupil tracking combined with angular differential imaging algorithms.

Results. The high angular resolution provided by SPHERE allows us to reveal a new feature in the disk which is interpreted as a superimposition of two belts of planetesimals located at stellocentric distances of ~85 and ~115 au, and with a mutual inclination of about 5°. Despite the very high inclination of the disk with respect to the line of sight, we conclude that the presence of a gap, that is, a void in the dust distribution between the belts, is likely.

Conclusions. We discuss the implication of the existence of two belts and their relative inclination with respect to the presence of planets.