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

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.

Chasing Shadows: Rotation of the Azimuthal Asymmetry in the TW Hya Disk*

“…For example, PDS 66 showed variability in its SB in the optical (Schneider et al 2014) on monthly timescales and hints at azimuthal movement of features with GPI polarized intensity data (Wolff et al 2016). The transition disk J160421.7-213028, observed with SPHERE/ZIMPOL in the visible and with HiCIAO in polarized H-band intensity, also showed a localized dip in the SB of its disk that appeared to move by ∼12°yr −1 ; however, the angular velocity of the shadow pattern is indeterminate, given that data were obtained at only two epochs (Mayama et al 2012;Pinilla et al 2015). Additional claims of variable shadowing have been put forth for HD 163296 (Wisniewski et al 2008), but again the epochto-epoch variation was hard to characterize owing to a dearth of coverage.…”

The Sizes and Depletions of the Dust and Gas Cavities in the Transitional Disk J160421.7-213028

“…The central source is a pre-mainsequence star with a spectral type of K2, an effective temperature ofT 4500 eff K, and a mass ~ M M 1 (Dahm & Carpenter 2009;Mathews et al 2012;Carpenter et al 2014). Its cavity is one of the largest, extending to ∼70 au, as vividly revealed in NIR polarized light by Subaru/HiCIAO (H-band; Mayama et al 2012) and VLT/SPHERE ( ¢ R -band; Pinilla et al 2015). Millimeter observations using SMA (0.88 mm; Mathews et al 2012) and ALMA (cycle0, 0.88 mm, band 7;Zhang et al 2014) have resolved the cavity in dust and CO J=3-2 emission, with angular resolutions of ´ 0.…”

Spirals in protoplanetary disks from photon travel time

“…HD 163296 and J160421, Garufi et al 2014;Pinilla et al 2015). Variable inner disk extinction also explains several types of variation in light curves of highly inclined disk-hosting stars such as AA Tau (Bouvier et al 2007) and a number of sources in the NGC 2264 cluster Stauffer et al 2015).…”