摘要：We present κ Andromeda b's photometry and astrometry taken with Subaru/SCExAO+HiCIAO and Keck/NIRC2, combined with recently published SCExAO/CHARIS low-resolution spectroscopy and published thermal infrared photometry to further constrain the companion's atmospheric properties and orbit.The Y/Y−K colors of κ And b are redder than field dwarfs, consistent with its youth and lower gravity.Empirical comparisons of its Y-band photometry and CHARIS spectrum to a large spectral library of isolated field dwarfs reaffirm the conclusion from Currie et al.that it likely has a low gravity but admit a wider range of most plausible spectral types (L0–L2).Our gravitational classification also suggests that the best-fit objects for κ And b may have lower gravity than those previously reported.Atmospheric models lacking dust/clouds fail to reproduce its entire 1–4.7 μm spectral energy distribution (SED), and cloudy atmosphere models with temperatures of ~1700–2000 K better match κ And b data.Most well-fitting model comparisons favor 1700–1900 K, a surface gravity of log(g) ~ 4–4.5, and a radius of 1.3–1.6 RJup; the best-fit model (Drift-Phoenix) yields the coolest and lowest-gravity values: Teff = 1700 K and log g = 4.0.An update to κ And b's orbit with ExoSOFT using new astrometry spanning 7 yr reaffirms its high eccentricity (0.77 ± 0.08).We consider a scenario where unseen companions are responsible for scattering κ And b to a wide separation and high eccentricity.If three planets, including κ And b, were born with coplanar orbits, and one of them was ejected by gravitational scattering, a potential inner companion with mass gsim10 MJup could be located at lesssim25 au.
