Featureless stars: Flux Calibration for Extremely Large Telescopes

TL;DR

This paper identifies a network of 29 bright, featureless white dwarf stars with near-perfect blackbody spectra, providing a new standard for flux calibration in upcoming large telescopic surveys and high-precision cosmology.

Contribution

It introduces a set of 29 featureless white dwarf stars as calibration standards, addressing systematic uncertainties in flux calibration for next-generation telescopes.

Findings

Identified 29 bright featureless white dwarf stars suitable for calibration.

Computed systematic uncertainties and magnitude offsets for major surveys.

Included these standards in the PypeIt data reduction pipeline.

Abstract

The spectrophotometric flux calibration of recent spectroscopic surveys has reached a limiting systematic precision of approximately 1-3 percent, and is often biased near the wavelengths associated with H I Balmer absorption. As we prepare for the next generation of imaging and spectroscopic surveys, and high-precision cosmology experiments, we must find a way to address this systematic. Towards this goal, we have identified a global network of 29 bright (G < 17.5) featureless white dwarf stars that have a spectral energy distribution consistent with an almost pure blackbody form over the entire optical and near-infrared wavelength range. Based on this sample, we have computed the systematic uncertainty and AB magnitude offsets associated with Gaia, SDSS, SMSS, PanSTARRS, DES, and 2MASS, and we have also checked the consistency of our objects with both GALEX and WISE. The magnitude range of the featureless stars reported here are ideally suited to observations taken with the forthcoming generation of extremely large telescopes, as well as calibrating the survey data acquired by the Rubin, Euclid and Roman observatories. Finally, all of the high-precision spectrophotometric standard stars reported here have been included in the latest release of the PypeIt data reduction pipeline.