Scexao/Charis near-infrared direct imaging, spectroscopy, and forward-modeling of k And B: A likely young, low-gravity superjovian companion

We present SCExAO/CHARIS high-contrast imaging/JHK integral field spectroscopy of k And b, a directly-imaged low-mass companion orbiting a nearby B9V star. We detect k And b at a high signal-to-noise and extract high precision spectrophotometry using a new forward-modeling algorithm for (A-)LOCI complementary to KLIP-FM developed by Pueyo et al. (2016). k And bfs spectrum best resembles that of a low-gravity L0.L1 dwarf (L0.L1). Its spectrum and luminosity are very well matched by 2MASSJ0141-4633 and several other 12.5.15 MJ free floating members of the 40 Myr-old Tuc-Hor Association, consistent with a system age derived from recent interferometric results for the primary, a companion mass at/near the deuterium-burning limit (13+12 .2 MJ), and a companion-to-primary mass ratio characteristic of other directly-imaged planets (q ∼ 0.005+0.005 .0.001). We did not unambiguously identify additional, more closely-orbiting companions brighter and more massive than k And b down to ∼ 0.ŒŒ3 (15 au). SCExAO/CHARIS and complementary Keck/NIRC2 astrometric points reveal clockwise orbital motion. Modeling points towards a likely eccentric orbit: A subset of acceptable orbits include those that are aligned with the starfs rotation axis. However, k And bfs semimajor axis is plausibly larger than 75 au and in a region where disk instability could form massive companions. Deeper k And high-contrast imaging and low-resolution spectroscopy from extreme AO systems like SCExAO/CHARIS and higher resolution spectroscopy from Keck/OSIRIS or, later, IRIS on the Thirty Meter Telescope could help clarify k And bfs chemistry and whether its spectrum provides an insight into its formation environment.