Method for tilt correction of calibration lines in high-resolution spectra

Abstract

Technological advancement has led to improvement in the design capabilities of astronomical spectrographs, allowing for high-precision spectroscopy, thereby expanding the realms of observational astronomy. High-resolution spectrographs use echelle gratings that operate in higher orders, giving more detailed spectra. Often, curvature and tilted lines are observed in the spectra, arising due to the design trade-offs of the respective spectrographs. Removal of these artifacts can help avoid wrong flux calculation and line centroid position misinterpretation, which can aid in a better prediction of the wavelength calibration model. In this paper we present a postprocessing technique that we developed to correct the observed curvature and tilt in the spectra. We have demonstrated the correction technique on Fabry–Perot and Th-Ar calibration spectra obtained from a Hanle echelle spectrograph, a Magellan Inamori Kyocera Echelle spectrometer, and a X-Shooter spectrograph.