Dust and the nature of GQ Lupi B

Observations of the dust in the GQ Lupi system suggest there is a compact dust disk around GQ Lupi A, it is fairly low mass with a radius of about 50 AU. This argues against the formation of GQ Lupi in situ as a planet. There is also no evidence for an inner companion that could have scattered GQ Lupi B to its current wide separation.

Further evidence that this is a star + brown dwarf binary system?

Likely. Moreover 21 Mj planet seems unlikely to be planetary.

Some constraints on the orbit of the companion, as well as a measurement of it's v sin i, which is rather low compared to 2M1207b and Bet Pic b.

The slow spin of the young sub-stellar companion GQ Lupi b and its orbital configuration
http://arxiv.org/abs/1607.00012

Quote :

The spin of a planet or brown dwarf is related to the accretion process, and therefore studying spin can help promote our understanding of the formation of such objects. We present the projected rotational velocity of the young sub-stellar companion GQ Lupi b, along with its barycentric radial velocity. The directly imaged exoplanet or brown dwarf companion joins a small but growing ensemble of wide-orbit sub-stellar companions with a spin measurement. The GQ Lupi system was observed at high spectral resolution (R ~ 100000), and in the analysis we made use of both spectral and spatial filtering to separate the signal of the companion from that of the host star. We detect both CO (S/N=11.6) and H2O (S/N=7.7) in the atmosphere of GQ Lupi b by cross-correlating with model spectra, and we find it to be a slow rotator with a projected rotational velocity of 5.3+0.9−1.0 km/s. The slow rotation is most likely due to its young age of < 5 Myr, as it is still in the process of accreting material and angular momentum. We measure the barycentric radial velocity of GQ Lupi b to be 2.0±0.4 km/s, and discuss the allowed orbital configurations and their implications for formation scenarios for GQ Lupi b.