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 (+21 others)
2018 Astronomical Journal  
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
more » ... 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.
doi:10.3847/1538-3881/aae9ea fatcat:ctqufhjspjetfdd7bsrmvud3rq