Kappa Andromedae: a super-Jupiter around a B-type star?

From the EPE bibliography section:

Direct Imaging Discovery of a ‘Super-Jupiter’ Around the late B-Type Star κ And
CARSON J., T6HALMANN C., JANSON M.,, KOZAKIS T., BONNEFOY M. & 51 additional authors

No link yet to the paper.

SIMBAD lists Kappa Andromedae as an A0V, but the MK measurements section also lists B9IVn, B8V and A0IV.

SIMBAD also lists it as a star in a double system and CCDM gives two additional components but I can't find any evidence that either is actually a member of the system. Eggleton+ (2008) lists it with a most probable multiplicity of 1.

Wow, Lazarus. This is really weird!

Now on arXiv.
http://arxiv.org/abs/1211.3744

So like HR 8799, it is also a probable member of the Columba association. Certainly another interesting datapoint to consider regarding deuterium-burning planets and non-fusing brown dwarfs.

Characterization of the gaseous companion κ Andromedae b: New Keck and LBTI high-contrast observations
http://arxiv.org/abs/1308.3859

The mass of b could be much higher than thought.

Well, "could". The weaker mass constraint is due to the conservative consideration that the star isn't a Columba MG member, leading to the age of the Pleiades as the upper limit. The paper shows that it is very likely a member, but suggests that more study of the northern sky for members is needed to be more certain.

Looks like Kappa Andromedae b is indeed much more massive than thought.

The Kappa Andromedae System: New Constraints on the Companion Mass, System Age & Further Multiplicity
http://arxiv.org/abs/1309.3372

Quote :

Kappa Andromedae is a B9IVn star at 52 pc for which a faint substellar companion separated by 55 AU was recently announced. In this work, we present the first spectrum of the companion, "kappa And B," using the Project 1640 high-contrast imaging platform. Comparison of our low-resolution YJH-band spectra to empirical brown dwarf spectra suggests an early-L spectral type. Fitting synthetic spectra from PHOENIX model atmospheres to our observed spectrum allows us to constrain the effective temperature to ~2000K, as well as place constraints on the companion surface gravity. Further, we use previously reported log(g) and effective temperature measurements of the host star to argue that the kappa And system has an isochronal age of 220 +/- 100 Myr, older than the 30 Myr age reported previously. This interpretation of an older age is corroborated by the photometric properties of kappa And B, which appear to be marginally inconsistent with other 10-100 Myr low-gravity L-dwarfs for the spectral type range we derive. In addition, we use Keck aperture masking interferometry combined with published radial velocity measurements to rule out the existence of any tight stellar companions to kappa And A that might be responsible for the system's overluminosity. Further, we show that luminosity enhancements due to a nearly "pole-on" viewing angle coupled with extremely rapid rotation is unlikely. Kappa And A is thus consistent with its slightly evolved luminosity class (IV) and we propose here that kappa And, with a revised age of 220 +/- 100 Myr, is an interloper to the 30 Myr Columba association with which it was previously associated. The photometric and spectroscopic evidence for kappa And B combined with our re-assesment of the system age implies a substellar companion mass of 50^{+16}_{-13} Jupiter Masses, consistent with a brown dwarf rather than a planetary mass companion.

Ah.

…Rats! Cuurse yoouu accordant kinematiiics!

…Sooooo.

The Age of the Directly-Imaged Planet Host Star κ Andromedae Determined From Interferometric Observations

Quote :

κ Andromedae, an early type star that hosts a directly imaged low mass companion, is expected to be oblate due to its rapid rotational velocity (vsini = ∼162 km s⁻¹). We observed the star with the CHARA Array's optical beam combiner, PAVO, measuring its size at multiple orientations and determining its oblateness. The interferometric measurements, combined with photometry and this vsini value are used to constrain an oblate star model that yields the fundamental properties of the star and finds a rotation speed that is ∼85% of the critical rate and a low inclination of ∼30°. Three modeled properties (the average radius, bolometric luminosity, and equatorial velocity) are compared to MESA evolution models to determine an age and mass for the star. In doing so, we determine an age for the system of 47⁺²⁷₋₄₀ Myr. Based on this age and previous measurements of the companion's temperature, the BHAC15 evolution models imply a mass for the companion of 22⁺⁸₋₉ MJ.

This group has previously applied this method to A-type stars in the UMa moving group (see here). Their results there were precise and consistent with other methods, which indicates that they are probably accurate. There is reason enough to take this result seriously.

If we harken back to the previously listed paper, even in the abstract it says:

Quote :

Further, we show that luminosity enhancements due to a nearly "pole-on" viewing angle coupled with extremely rapid rotation is unlikely.

This is exactly what is observed. (And hell, 30° degrees isn't even that close to pole-on)

The poor error bars on the age mostly stem from the poor constraint on the stellar (internal) metallicity, which is not truly observable for rapidly rotating AB stars. There may not be much possibility to improve on the errors until this effect is better understood.

Whether one can consider a ~22 M_J object a planet is perhaps not the important part here.

Finally, to quote:

Quote :

We note that a more recent age estimate of the Columba association by Bell et al. (2015) finds it to be 42⁺⁶_-4 Myr, which is in excellent agreement with our age estimate for κ And A. Despite its outlying Galactic Y position with respect to Columba (2.7σ, H13), the agreement in age suggests that its kinematic association with young nearby groups should be reconsidered.

Moderate-Resolution K-Band Spectroscopy of Substellar Companion κ Andromedae b
https://arxiv.org/abs/2009.08959