Observations of O VI Emission from the Diffuse Interstellar Medium toward ℓ = 113°, b = 71°

Emission from O VI (λλ1032, 1038) in the diffuse interstellar medium was observed in two, long Far Ultraviolet Spectroscopic Explorer (FUSE) observations at ℓ ≃ 1130 and b ≃ 707 (near the quasar HS 1307+4617). The observed intensities are 2580 ± 380 (random) ±360 (systematic) and 1100 ± 160 (random) ±160 (systematic) photons cm^-2 s^-1 sr^-1 in the 1032 and 1038 Å emission lines, respectively. The electron density, thermal pressure, and depth of the emitting gas are calculated from the observed intensities. The velocity of the emitting material is about +10 km s^-1 relative to the local standard of rest and less than +30 km s^-1 relative to the H I along the line of sight. The similarity suggests that the highly ionized gas is quiescent and not recently shock heated. Emission from the C II 3 s² S_1/2 to 2p² P_3/2 transition at 1037 Å is also observed, and upper limits are placed on the intensities of ultraviolet line emission from C I, C III, N I, N II, Mg II, Si II, S II, S III, S IV, S VI, Fe II, and Fe III.