Spectrophotometric Libraries, Revised Photonic Passbands and Zero-points for UBVRI, Hipparcos and Tycho Photometry

TL;DR

This paper refines photonic passbands and zero-points for key photometric systems using spectrophotometric libraries, improving the accuracy of stellar magnitude measurements across multiple systems.

Contribution

It introduces revised photonic passbands and zero-points for UBVRI, Hipparcos, and Tycho systems based on extensive spectrophotometric data, aligning synthetic and catalog magnitudes.

Findings

Revised passbands improve synthetic photometry accuracy.

Zero-points are calibrated to match Hipparcos catalog magnitudes.

Comparison of zero-points across different photometric systems clarifies discrepancies.

Abstract

We have calculated improved photonic passbands for the UBV RI, Hipparcos and Tycho Hp,BT,VT standard systems using the extensive spectrophotometric libraries of NGSL and MILES. Using the Hp passband, we adjusted the absolute flux levels of stars in the spectrophotometric libraries so their synthetic Hp magnitudes matched the precise Hipparcos catalog value. Synthetic photometry based on the renormalized fluxes were compared to the standard UBVRI and BT, VT magnitudes and revised synthetic zero-points were determined. The Hipparcos and Tycho photometry system zero-points were also compared to the V magnitude zero-points of the SAAO UBVRI system, the homogenized UBV system and the Walraven V B system. The confusion in the literature concerning broadband magnitudes, fluxes, passbands and the choice of appropriate mean wavelengths is detailed and discussed in an appendix.