Kappa Andromedae B: New Constraints on the Companion Mass, System Age and Further Multiplicity

I will report new results on the companion to the B9IV star kappa Andromedae, originally detected using adaptive optics and coronagraphy at Subaru Observatory, with an initially reported mass of 12.8 Jupiter masses. I will present the first spectrum of the companion, kappa And B, using the Project 1640 high-contrast imaging platform at Palomar Observatory. Comparison of our low-resolution YJH-band spectra to empirical brown dwarf spectra as well as synthetic models suggests an early-L spectral type and an effective temperature of 2000 K. Further, we use previously reported log(g) and effective temperature measurements of the host star to argue that the kappa Andromedae 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 Andromedae 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 Andromedae 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 Andromedae A is thus consistent with its slightly evolved luminosity class (IV) and we propose here that kappa Andromedae, 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 Andromedae B combined with our re-assesment of the system age implies a companion mass more consistent with a brown dwarf than a planetary mass companion.