  We present far-IR/sub-mm imaging and spectroscopy of 49 Ceti, an unusual
circumstellar disk around a nearby young A1V star. The system is famous for
showing the dust properties of a debris disk, but the gas properties of a
low-mass protoplanetary disk. The data were acquired with the Herschel Space
Observatory PACS and SPIRE instruments, largely as part of the "Gas in
Protoplanetary Systems" (GASPS) Open Time Key Programme. Disk dust emission is
detected in images at 70, 160, 250, 350, and 500 \mu m; 49 Cet is significantly
extended in the 70 \mu m image, spatially resolving the outer dust disk for the
first time. Spectra covering small wavelength ranges centered on eight atomic
and molecular emission lines were obtained, including [OI] 63 \mu m and [CII]
158 \mu m. The CII line was detected at the 5\sigma\ level - the first
detection of atomic emission from the disk. No other emission lines were seen,
despite the fact that the OI line is the brightest one observed in Herschel
protoplanetary disk spectra (Meeus et al. 2012; Dent et al. 2013). We present
an estimate of the amount of circumstellar atomic gas implied by the CII
emission. The new far-IR/sub-mm data fills in a large gap in the previous
spectral energy distribution (SED) of 49 Cet. A simple model of the new SED
confirms the two-component structure of the disk: warm inner dust and cold
outer dust that produces most of the observed excess. Finally, we discuss
preliminary thermochemical modeling of the 49 Cet gas/dust disk and our
attempts to match several observational results simultaneously. Although we are
not yet successful in doing so, our investigations shed light on the
evolutionary status of the 49 Cet gas, which might not be primordial gas but
rather secondary gas coming from comets.
