Stellar Absolute Fluxes and Energy Distributions from 0.32 to 4.0 μM

Abstract

The absolute fluxes and energy distributions of stars are the foundation of the calibration of fundamental effective temperatures and bolometric corrections. In this paper I will review recent progress in the calibration of absolute fluxes and energy distributions in the visual and IR parts of the spectrum. In the visual, the calibration of the absolute flux and energy distribution of Vega has settled down well, and the remaining difficulties include the lack of a worldwide common list of brighter secondary standard stars, the lack of enough satisfactory fainter secondary standard stars and the possibility of variability in Vega. In the IR, the process of arriving at a dependable and accurate calibration, and of linking it to commonly used photometric systems, is in its infancy. A final, and rather special problem, is the question of the calibration of the Sun. The Sun is a special case both because it is so well studied astrophysically and because its extreme brightness makes it very difficult to calibrate photometrically. Some progress has recently been made on the calibration of the absolute flux and energy distribution of the Sun, and I will discuss this work.