An ALMA and MagAO Study of the Substellar Companion GQ Lup B^∗

Abstract

Multi-wavelength observations provide a complementary view of the formation of young, directly imaged planetmass companions. We report the ALMA 1.3 mm and Magellan adaptive optics Hα, ¢ i , ¢ z , and Y S observations of the GQ Lup system, a classical T Tauri star with a -M 10 40 Jup substellar companion at ∼110 au projected separation. We estimate the accretion rates for both components from the observed Hα fluxes. In our ∼0 05 resolution ALMA map, we resolve GQ Lup A's disk in thedust continuum, but no signal is found from the companion. The disk is compact, with a radius of ∼22 au, a dust mass of ∼6 M ⊕ , an inclination angle of ∼56°, and a very flat surface density profile indicative of a radial variation in dust grain sizes. No gaps or inner cavity are found in the disk, so there is unlikely a massive inner companion to scatter GQ Lup B outward. Thus, GQ Lup B might have formed in situ via disk fragmentation or prestellar core collapse. We also show that GQ Lup A's disk is misaligned with its spin axis, and possibly with GQ Lup B's orbit. Our analysis on the tidal truncation radius of GQ Lup A's disk suggests that GQ Lup B's orbit might have a low eccentricity.

The Young Substellar Companion ROXs 12 B: Near-infrared Spectrum, System Architecture, and Spin–Orbit Misalignment*

“…These subdisks produce a variety of observational signatures: ultraviolet excess emission from accretion of hot gas (Zhou et al 2014), hydrogen-line emission like Hα and Paβ (e.g., Bowler et al 2011;Wu et al 2015a), and thermal excess emission in the mid-infrared (Bailey et al 2013). Submillimeter emission from warm dust has only been detected for the ambiguous companion to FWTau (Caceres et al 2015;Kraus et al 2015) despite ongoing searches targeting several other disk-bearing substellar companions (e.g., MacGregor et al 2017;Wu et al 2017). …”

“…There is some evidence that the orbital axis of the brown dwarf companion GQ Lup B may be misaligned with both the stellar rotation axis and the stellar disk inclination (Ginski et al 2014;Schwarz et al 2016;MacGregor et al 2017;Wu et al 2017), although it is unclear how significant this potential spin-orbit misalignment is due to discrepancies in the rotation period and radius of the host star. HR 8799 is an excellent example of a system with increasingly robust constraints on the spin axis of the host star, orbital inclination of its four imaged planets, and inclination measurements for its multibelt debris disk.…”

An Upper Limit on the Mass of the Circumplanetary Disk for DH Tau b*

“…If the PMCs are formed from the gravitational collapse of the surrounding molecular cloud itself, and not formed in a circumstellar disk, we could expect the PMC to follow the same trend in theplanet to disk mass ratio as inthe parent starforming region. However, the relative disk to star/planetmass ratios do not appear to be correlated in binary systems, where the viscosity of the disk dictates the evolutionary timescales (e.g., Akeson & Jensen 2014;Wu et al 2017). This mechanism is not clearly supported by the DH Tau b and GQ Lup b observations.…”

“…CO emission showing a gas disk that extends outside of GQ Lup b. A recent multi-wavelength study of the GQ Lup system using both ALMA continuum observations and MagAO optical photometry of the companion show that the circumstellar disk of GQ Lup A is misaligned with the spin axis, possibly due to interaction with GQ Lup b (Wu et al 2017). GSC 0614-210: The circumplanetary disk around the 10 Myr old GSC 0614-210 B was not detected in ALMA continuum observations at 880 mm with a 3σ rms noise level of 0.22 mJy beam −1 .…”

2MASS J15491331-3539118: a new low-mass wide companion of the GQ Lup system

“…70. This BD companion was found to be actively accreting (Zhou et al 2014), suggesting the presence of a disc around it, although more recent observations show that the accretion is non-steady (Wu et al 2017).…”