Abstract
Narrow-band filters can detect emission and absorption line features from multiple sources in a field of view simultaneously without spectroscopy. However, it is difficult to estimate and subtract the continuum component from sources of different spectral slope, especially when the equivalent width of the target lines is small. For example, Cataclysmic Variables have equivalent widths of hydrogen recombination emission lines of about –10 to –100 angstroms, but many of the ones that have been detected by conventional NB filters so far have a large equivalent width. We have therefore constructed novel narrow-band filters with transmission bands on both sides of the central wavelengths of the Paβ (1.282 µm) and Brγ (2.167 µm) emission lines so that we can evaluate the continuum level more accurately than the conventional filters having transmission in only one side of the target line. We installed the narrow-band filters to the Simultaneous three-color InfraRed Imager for Unbiased Survey (SIRIUS) in the InfraRed Survey Facility (IRSF) telescope at South African Astronomical Observatory (SAAO), and evaluated their performance. We found that the narrow-band filters can detect emission line features with an equivalent width of several tens of angstroms. Thus, this filter set is useful for detecting emission line features from targets with small equivalent widths that have been difficult to detect with the conventional NB filter set.
Published Version
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