2001AJ....121..362R

Infrared spectroscopy from 0.8 to 2.5 µm is presented for the planetary nebula IC 5117. The emission lines of IC 5117 span a wide range of ionization that includes He II, [S III], [S II], [N I], and H₂. The reddening measured from the hydrogen lines is E(B-V)=0.79, most of which is probably interstellar in origin. The He/H abundance ratio is 0.113±0.015, with approximately 10% of the helium being doubly ionized. Using our measurements of [S II] and [S III] lines and published observations of [S IV], we find a sulfur abundance, relative to hydrogen, of N(S)/N(H)=7.8x10^–6, or approximately half the solar value. Fluxes and flux limits for several lines of molecular hydrogen are presented. Measurements of 1-0 transitions, together with the limits on 2-1 transitions, indicate T_vib~T_rot=1900 K, suggesting a purely collisional excitation mechanism. The ortho-to-para ratio is ∼3, a value that is also indicative of collisional excitation. The presence of [C I] λ9850 is consistent with previous studies of IC 5117 that indicated carbon is more abundant than oxygen. IC 5117 follows the trend of planetary nebulae that display bipolar outflows and H₂ emission to be carbon-rich. We confirm the results of Zhang & Kwok, who reported infrared continuum emission substantially in excess of that produced by the ionized gas. This emission is most likely due to hot dust (T∼1300 K) and accounts for roughly half of the continuum between 1.5 and 2 µm.