Characterizing U-Ne hollow cathode lamps at near-IR wavelengths for the CARMENES survey

摘要

Hollow cathode lamps of U and Th are the standard frequency calibrators in astronomical spectrographs. In an effort to optimize precision radial velocity measurements at near-IR wavelengths for the CARMENES survey, we are characterizing 12 commercial U-Ne hollow cathode lamps using a high resolution Fourier Transform Spectrograph and an InGaAs detector to analyze the wavelength range between 950 and 1700 nm. We have recorded spectral atlases of U-Ne operated at 8, 10 and 12 mA, which are typical values used at astronomical observatories in order to maximize lamp lifetimes. In addition to the spectral atlas, we analyze properties like warm-up times, average intensities from lines of different elements, positions and the width of emission lines, and blends. None of our lamps show strong peculiarities in the spectra or significant contamination. The identification of the uranium lines is based on the line widths and consistent with the Redman et al. (2011) catalog. Our line list can add a significant number of lines particularly in the range around 9000 cm~(-1) (1.1 μm) where the catalog is incomplete because of limited detector sensitivity. We are able to identify the elements emitting additional lines by measuring the line width. The increased number of U lines at wavelengths relevant to radial velocity surveys can yield a significant improvement in the accuracy of radial velocity measurements.