2024A&A...684A.168Z

Context. A spatially resoved circumstellar disk spectrum and composition can provide valuable insights into the bulk composition of forming planets and into the mineralogical signatures that emerge during and after planet formation.
Aims. We systemically extracted the RX J1604.3-213010 (J1604 hereafter) protoplanetary disk in high-contrast imaging observations and obtained its multi-band reflectance in the visible to near-infrared wavelengths.
Methods. We obtained coronagraphic observations of J1604 from the Keck Observatory NIRC2 instrument and archival data from the Very Large Telescope SPHERE instrument. Using archival images to remove star light and speckles, we recovered the J1604 disk and obtained its surface brightness using forward modeling. Together with polarization data, we obtained the relative reflectance of the disk in R, J, H (H2 and H3), K (K1 and K2), and L' bands spanning 2 yr.
Results. Relative to the J1604 star, the resolved disk has a reflectance of ∼10^–1 arcsec^–2 in R through H bands and ∼10^–2 arcsec^–2 in K and L' bands, showing a blue color. Together with other systems, we summarized the multiband reflectance for nine systems. We also identified a varying disk geometry structure, and a shadow that vanished between June and August in 2015.
Conclusions. Motivated by broadband observations, the deployment of the latest technologies could yield higher-resolution reflection spectra, thereby informing the dust composition of disks in scattered light in the future. With multi-epoch observations, variable shadows have the potential to deepen our insight into the dynamic characteristics of inner disk regions.