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Arxiv: Mid-Infrared Spectrum of the Disk around the Forming Companion GQ Lup B Revealed by JWST/MIRI Published: 4/10/2024 6:18:29 PM Updated: 4/10/2024 6:18:29 PM

Paper abstract: GQ Lup B is a forming brown dwarf companion (M~10-30~M_J) showingevidence for an infrared excess associated with a disk surronding the companionitself. Here we present mid-infrared (MIR) observations of GQ Lup B with theMedium Resolution Spectrograph (MRS) on JWST, spanning 4.8-11.7~\mum. Weremove the stellar contamination using reference differential imaging based onprincipal component analysis (PCA), demonstrating that the MRS can performhigh-contrast science. Our observations provide a sensitive probe of the disksurrounding GQ Lup B. We find no sign of a silicate feature, similar to otherdisk surrounding very low mass objects, which likely implies significant graingrowth (a_{\mathrm{min}}\gtrsim5~\mum), and potentially dust settling.Additionally, we find that if the emission is dominated by an inner wall, thedisk around the companion might have an inner cavity larger than the one set bysublimation. Conversely, if our data probe the emission from a thin flat disk,we find the disk to be very compact. More observations are required to confirmthis finding and assess the vertical structure of the disk. This approach pavesthe path to the future study of circumplanetary disks and their physicalproperties. Our results demonstrate that MIR spectroscopic observations canreveal the physical characteristics of disks around forming companions,providing unique insights into the formation of giant planets, brown dwarfs andtheir satellites.