Characterizing the Protolunar Disk of the Accreting Companion GQ Lupi B
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).
- Publication:
-
The Astronomical Journal
- Pub Date:
- December 2021
- DOI:
- 10.3847/1538-3881/ac2c7f
- arXiv:
- arXiv:2110.04307
- Bibcode:
- 2021AJ....162..286S
- Keywords:
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- 14;
- 185;
- 387;
- 1241;
- 1425;
- 2167;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 28 pages, 11 figures, accepted for publication in AJ