Characterizing the Protolunar Disk of the Accreting Companion GQ Lupi B

December 2021 • 2021AJ....162..286S

Authors • Stolker, Tomas • Haffert, Sebastiaan Y. • Kesseli, Aurora Y. • van Holstein, Rob G. • Aoyama, Yuhiko • Brinchmann, Jarle • Cugno, Gabriele • Girard, Julien H. • Marleau, Gabriel-Dominique • Meyer, Michael R. • Milli, Julien • Quanz, Sascha P. • Snellen, Ignas A. G. • Todorov, Kamen O.

Abstract • GQ Lup B is a young and accreting, substellar companion that appears to drive a spiral arm in the circumstellar disk of its host star. We report high-contrast imaging observations of GQ Lup B with VLT/NACO at 4-5 μm and medium-resolution integral field spectroscopy with VLT/MUSE. The optical spectrum is consistent with an M9 spectral type, shows characteristics of a low-gravity atmosphere, and exhibits strong Hα emission. The H - M' color is ≳1 mag redder than field dwarfs with similar spectral types, and a detailed analysis of the spectral energy distribution (SED) from optical to mid-infrared wavelengths reveals excess emission in the L', NB4.05, and M' bands. The excess flux is well described by a blackbody component with T _disk ≈ 460 K and R _disk ≈ 65 R _J and is expected to trace continuum emission from small grains in a protolunar disk. We derive an extinction of A _V ≈ 2.3 mag from the broadband SED with a suspected origin in the vicinity of the companion. We also combine 15 yr of astrometric measurements and constrain the mutual inclination with the circumstellar disk to 84 ± 9 deg, indicating a tumultuous dynamical evolution or a stellar-like formation pathway. From the measured Hα flux and the estimated companion mass, M _p ≈ 30 M _J, we derive an accretion rate of $\dot{M}\approx {10}^{-6.5}\,{M}_{{\rm{J}}}\,{\mathrm{yr}}^{-1}$ . We speculate that the disk is in a transitional stage in which the assembly of satellites from a pebble reservoir has opened a central cavity while GQ Lup B is in the final stages of its formation. ∗Based on observations collected under ESO programmes 0101.C-0502(B), 0102.C-0649(A), and 0103.C-0524(A).

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• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2021AJ....162..286S
• PDF https://iopscience.iop.org/article/10.3847/1538-3881/ac2c7f/pdf
• PREPRINT http://arxiv.org/abs/2110.04307
• DATA http://archive.eso.org/bin/ads2eso?2021AJ....162..286S
• DATA https://irsa.ipac.caltech.edu/bibdata/2021/S/2021AJ....162..286S.html
• ELECTR https://iopscience.iop.org/article/10.3847/1538-3881/ac2c7f