Hα Flux Extraction from Continuum-Dominated Sources Using a Simplified Three-Filter Method

초록

This paper introduces a simple and reliable photometric calibration method to extract Hα line flux from narrowband images. The equivalent width of the Hα line (EW_<sub>Hα<\sub>) is derived using two- and simplified three-filter methods. Synthetic photometry of CALSPEC stars demonstrates the dependency of EW_<sub>Hα<\sub> on the <i>V - R</i> color, described by a skewed Gaussian function within -0.1 < <i>V - R</i> < 0.7. Systematic errors of the two- and three-filter methods are analyzed under 0%–10% <i>R</i>-band flux contamination. Although the three-filter method underestimates EW_<sub>Hα<\sub> by 10%, it exhibits less scatter compared to the two-filter method. The simplified three-filter method was validated with the Landolt SA 107 field and surpasses the two-filter method in terms of precision and accuracy. Additionally, applying our method to V960 Mon yields EW_<sub>Hα<\sub> consistent with high-resolution spectroscopic results.

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