Planet at Chi Draconis ?

Magnetic field and radial velocities of the star Chi Draconis A
https://arxiv.org/abs/1709.08777

Quote :

We present high-resolution spectropolarimetric observations of the spectroscopic binary Chi Dra. Spectral lines in the spectrum of the main component Chi Dra A show variable Zeeman displacement, which confrms earlier suggestions about the presence of a weak magnetic field on the surface of this star. Within about 2 years of time base of our observations, the longitudinal component BL of the magnetic field exhibits variation from -11.5 +/- 2.5 G to +11.1 +/- 2.1 G with a period of about 23 days. Considering the rotational velocity of Chi DraA in the literature and that newly measured in this work, this variability may be explained by the stellar rotation under the assumption that the magnetic field is globally stable. Our new measurements of the radial velocities (RV) in high-resolution I-spectra of Chi Dra A refined the orbital parameters and reveal persistent deviations of RVs from the orbital curve. We suspect that these deviations may be due to the in uence of local magnetically generated spots, pulsations, or a Jupiter-size planet orbiting the system.

They propose a hot Jupiter around Chi Draconis A as a possible explanation to RV residuals, but they can't rule out magnetic activity of course. A hot Jupiter around a member of a binary system with a period of 0.8 years would be rather interesting, too.

I don't see that a planet is a particularly likely possibility. Maybe Chi Draconis has cold circumbinary planets, but S-type planets would be surprising.

Lazarus wrote:

I don't see that a planet is a particularly likely possibility. Maybe Chi Draconis has cold circumbinary planets, but S-type planets would be surprising.

Why not both?

Periastron for Chi Draconis AB is about 0.5 AU, the stable zone for circumstellar orbits will be substantially smaller. There do seem to be some S-type planets in surprisingly close binaries (e.g. Kepler-693, which has been claimed to have a binary companion with a periastron of about 1.5 AU), but as far as I'm aware these do not seem to be particularly common.