SCExAO/CHARIS Near-infrared Direct Imaging, Spectroscopy, and Forward-Modeling of κ And b: A Likely Young, Low-gravity Superjovian Companion
Thayne Currie, Timothy D. Brandt, Taichi Uyama, Eric L. Nielsen, Sarah Blunt, Olivier Guyon, Motohide Tamura, Christian Marois, Kyle Mede, Masayuki Kuzuhara, Tyler D. Groff, Nemanja Jovanovic
We present SCExAO/CHARIS high-contrast imaging/JHK integral field spectroscopy of κ And b, a directly-imaged low-mass companion orbiting a nearby B9V star. We detect κ 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 (2016). κ And b's spectrum best resembles that of a low-gravity L0--L1 dwarf (L0--L1γ). Its spectrum and luminosity are very well matched by 2MASSJ0141-4633
... d several other 12.5--15 M_ J 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 M_ J), 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 κ And b down to ρ ∼ 0.3" (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 star's rotation axis. However, κ And b's semimajor axis is plausibly larger than 75 au and in a region where disk instability could form massive companions. Deeper κ 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 κ And b's chemistry and whether its spectrum provides an insight into its formation environment.