Calibrated griz magnitudes of Tycho stars: All-sky photometric calibration using bright stars

TL;DR

This paper presents a method to calibrate all-sky griz magnitudes for bright stars using spectral templates, achieving 5% accuracy and enabling precise photometric calibration with multiple stars.

Contribution

It introduces a new all-sky catalog of calibrated griz magnitudes for bright stars based on spectral template fitting, improving calibration efficiency.

Findings

Single-star calibration accuracy around 0.08-0.12 mag.

Using ~10 stars reduces errors to about 0.02-0.04 mag.

Method enables accurate calibration when multiple stars are observed.

Abstract

Photometric calibration to 5% accuracy is frequently needed at arbitrary celestial locations; however, existing all-sky astronomical catalogs do not reach this accuracy and time consuming photometric calibration procedures are required. I fit the Hipparcos B_T and V_T magnitudes along with the 2MASS J, H, and K magnitudes of Tycho-2 catalog-stars with stellar spectral templates. From the best fit spectral template derived for each star, I calculate the synthetic SDSS griz magnitudes and constructed an all-sky catalog of griz magnitudes for bright stars (V<12). Testing this method on SDSS photometric telescope observations, I find that the photometric accuracy for a single star is usually about 0.12, 0.12, 0.10 and 0.08 mag (1 sigma), for the g, r, i, and z-bands, respectively. However, by using ~10 such stars, the typical errors per calibrated field (systematic + statistical) can be reduced to about 0.04, 0.03, 0.02, and 0.02,mag, in the g, r, i, and z-bands, respectively. Therefore, in cases for which several calibration stars can be observed in the field of view of an instrument, accurate photometric calibration is possible.