Telluric standard stars are measured by X-shooter frequently during most nights to provide a representative reference for telluric absorption line correction, and also supply science-grade spectra of early-type and solar-type stars at different epochs.

The released products consist of extracted, wavelength-calibrated and flux-calibrated 1-dimensional spectra in tabular format following the established standard for ESO Science Data Products. There are normally spectra for all three X-shooter arms (UVB, VIS, NIR). They often come as multiple exposures with exposure times optimized “on the fly”. Often some of these exposures are saturated, and they should be carefully checked for quality. When downloaded, each spectrum comes with ancillary information related to quality control and observational circumstances, and with a preview plot. The data have been pipeline-processed with the best available calibration data. For more details please refer to the associated release description.

Telluric standard star spectra can be downloaded as Spectra Data Products from the X-shooter collection by querying using an object list, for example by using the Hipparcos catalogue, or via the query form.

Upper plot: An example combined, flux-calibrated, spectrum from all three arms of X-shooter. For this overview plot, the separate spectra have been rebinned (0.5 nm for UVB and VIS; 2nm for NIR). The individual spectra in the release come with the full resolution.