STARSFLUX an all-sky catalogue of absolute spectro-photometric calibrators from 0.3 to 30 μm

Obtaining accurate fluxes of faint sources from the ground in near- and mid-infrared wavelengths is challenging because of the rapidly changing atmospheric absorption. A common limitation is the lack of a nearby spectro-photometric calibrator. We present the STellar Absolute Reference Spectroscopic Flux Library (starsflux), an all-sky catalogue of calibrator spectra spanning 0.3–30 μm and comprising 64 484 stars; the target list is based on the Mid-infrared stellar Diameters and Fluxes compilation Catalogue (MDFC). starsflux combines Gaia DR3 stellar parameters with multiband photometry from space- and ground-based surveys and synthetic NewEra PHOENIX atmosphere models. We fit each observed stellar Spectral Energy Distribution (SED) with an interpolated model spectrum, an estimated diameter and estimated extinction to produce a flux-calibrated spectrum. The photometric diameter can be used for accurate calibration of interferometric observations. We validate the catalogue in three ways. First, starsflux angular radii agree closely with independent Gaia DR3 radii, with median |ΔR|/R_Gaia,DR3 ≃ 4.8 per cent⁠. Second, The integrated L band (2.8–4.2 μm) fluxes for 12 stars in common with the Cohen infrared standard agree with the Cohen values with a mean absolute percentage difference of 4.7 per cent ± 2.6 per cent. Finally we compare the starsflux near-UV/visible/near-IR spectra with the Gaia DR3 BP/RP spectra. The absolute spectrophotometric fluxes agree to approximately 3 per cent. The spectra in FITS format are available from the STARSFLUX webpage and will be submitted to VizieR.