Transition Disk J160421.7-213028 has a Massive Exoplanet at 9.6 AU

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

Authors:

Pinila et al

Abstract:

Context.

Some of transition disks show asymmetric structures in thermal sub-millimetre 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 (0.626μm). We probe 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 peak is at ∼59 AU from the central star. The peak of the reflected light at 0.626 μm seems to be slightly closer (∼4 AU) than the peak at 1.65 μm, and 20 AU closer than the cavity size observed at 880 μm. In addition, we detect a dip at position angle of ∼46.2±5.4∘. A dip was also detected with HiCIAO but at ∼85∘. If the dip observed with HiCIAO is the same, this suggests an average dip rotation of ∼12∘/year.

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 by fast variability of the inner disk and/or the presence of a warp or circumplanetary material of a planet at ∼9.6 AU.