CLIcK: A Continuum and Line fitting Kit for circumstellar disks

Infrared spectroscopy with medium to high spectral resolution is essential to characterize the gas content of circumstellar disks. Unfortunately, conducting continuum and line radiative transfer of thermochemical disk models is too time-consuming to carry out large parameter studies. Simpler approaches using a slab model to fit continuum-subtracted spectra require the identification of either the global or local continuum. Continuum subtraction, particularly when covering a broad wavelength range, is challenging but critical in rich molecular spectra as hot (several hundreds K) molecular emission lines can also produce a pseudo continuum. In this work, we present CLIcK, a flexible tool to simultaneously fit the continuum and line emission. The continuum model presented by Dullemond, Dominik, and Natta, and a plane-parallel slab of gas in local thermodynamic equilibrium are adopted to simulate the continuum and line emission, respectively, both of them are fast enough for homogeneous studies of large disk samples. We applied CLIcK to fit the observed water spectrum of the AA Tau disk and obtained water vapor properties that are consistent with literature results. We also demonstrate that CLIcK properly retrieves the input parameters used to simulate the water spectrum of a circumstellar disk. CLIcK will be a versatile tool for the interpretation of future James Webb Space Telescope spectra.