Variability and dust filtration in the transition disk J160421.7-213028 observed in optical scattered light^⋆,⋆⋆

¹ Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden The Netherlands
e-mail: pinilla@strw.leidenuniv.nl
² Univ. Grenoble Alpes, IPAG, 38000 Grenoble, France
³ CNRS, IPAG, 38000 Grenoble, France
⁴ Institute of Astronomy, Madingley Road, Cambridge CB3 OHA, UK
⁵ Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
⁶ Astronomical Institute Anton Pannekoek, University of Amsterdam, PO Box 94249, 1090 GE Amsterdam, The Netherlands
⁷ Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
⁸ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁹ European Southern Observatory (ESO), Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago, Chile
¹⁰ Centro de Astrobiología (INTA-CSIC), ESAC Campus, PO Box 78, 28691 Villanueva de la Canada, Spain
¹¹ Department of Physics & Astronomy, Rice University, 6100 Main Street, Houston, TX 77005, USA

Received: 16 July 2015
Accepted: 22 October 2015

Abstract

Context. Protoplanetary disks around young stars are the birth-sites of planets. Spectral energy distributions and direct images of a subset of disks known as transition disks reveal dust-depleted inner cavities. Some of these disks show asymmetric structures in thermal submillimetre emission and optical scattered light. These structures can be the result of planet(s) or companions embedded in the disk.

Aims. We aim to detect and analyse the scattered light of the transition disk J160421.7-213028, identify disk structures, and compare the results with previous observations of this disk at other wavelengths.

Methods. We obtained and analysed new polarised intensity observations of the transition disk J160421.7-213028 with VLT/SPHERE using the visible light instrument ZIMPOL at R′-band (0.626 μm). We probed the disk gap down to a radius of confidence of 0.1′′ (~15 AU at 145 pc). We interpret the results in the context of dust evolution when planets interact with the parental disk.

Results. We observe a gap from 0.1 to 0.3′′ (~15 to 40 AU) and a bright annulus as previously detected by HiCIAO H-band observations at 1.65μm. The radial width of the annulus is around 40 AU, and its centre is at ~61 AU from the central star. The peak of the reflected light at 0.626 μm is located 20 AU inward of the cavity detected in the submillimetre. In addition, we detect a dip at a position angle of ~46.2 ± 5.4°. A dip was also detected with HiCIAO, but located at ~85°. If the dip observed with HiCIAO is the same, this suggests an average dip rotation of ~12°/year, which is inconsistent with the local Keplerian angular velocity of ~0.8°/yr at ~61 AU.

Conclusions. The spatial discrepancy in the radial emission in J160421.7-213028 at different wavelengths is consistent with dust filtration at the outer edge of a gap carved by a massive planet. The dip rotation can be interpreted as fast variability of the inner disk and/or the presence of a warp or circumplanetary material of a planet at ~9.6 AU.