A Correction for IUE UV Flux Distributions from Comparisons with CALSPEC

TL;DR

This paper presents a correction to align IUE UV flux distributions with the more accurate CALSPEC standard, improving the consistency of archival UV data for future astronomical research.

Contribution

It provides a calibration correction that places IUE fluxes onto the CALSPEC scale, enhancing the accuracy of UV flux measurements from archival data.

Findings

IUE fluxes are repeatable within 4-10% in sensitive regions.

The average flux correction has a precision of 2-3%.

The corrected IUE flux scale aligns with the current UV standard.

Abstract

A collection of spectral energy distributions (SEDs) is available in the Hubble Space Telescope (HST) CALSPEC database that is based on calculated model atmospheres for pure hydrogen white dwarfs (WDs). A much larger set (~100,000) of UV SEDs covering the range (1150-3350A) with somewhat lower quality are available in the IUE database. IUE low-dispersion flux distributions are compared with CALSPEC to provide a correction that places IUE fluxes on the CALSPEC scale. While IUE observations are repeatable to only 4-10% in regions of good sensitivity, the average flux corrections have a precision of 2-3%. Our re-calibration places the IUE flux scale on the current UV reference standard and is relevant for any project based on IUE archival data, including our planned comparison of GALEX to the corrected IUE fluxes. IUE SEDs may be used to plan observations and cross-calibrate data from future missions, so the IUE flux calibration must be consistent with HST instrumental calibrations to the best possible precision.