We present the analysis of four hours of spectroscopic observations of NGC 6946 with the SITELLE Imaging Fourier Transform Spectrometer on the Canada-France-Hawaii Telescope, acquired to search for supernova light echoes from its ten modern supernovae. We develop a novel spectroscopic search method: identifying negatively sloped continua in the narrow-band SN3 filter as candidate highly-broadened P-Cygni profiles in the H$\alpha$ line, which would be characteristic of the spectra of supernovae ejecta. We test our methodology by looking for light echoes from any of the ten supernovae observed in NGC 6946 in the past 100 years. We find no evidence of light echoes above the survey surface brightness limit of 1$\times$10$^{-15}$erg/s/cm$^2$/arcsec$^2$.

中文翻译：

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使用 SITELLE 在 NGC 6946 中寻找超新星光回波

我们使用加拿大-法国-夏威夷望远镜上的 SITELLE 成像傅立叶变换光谱仪对 NGC 6946 的四小时光谱观测进行了分析，该望远镜用于搜索来自其十颗现代超新星的超新星光回波。我们开发了一种新的光谱搜索方法：将窄带 SN3 滤波器中的负斜连续体识别为 H$\alpha$ 线中候选的高度加宽的天鹅座 P-Cygni 剖面，这将是超新星喷射物光谱的特征。我们通过寻找过去 100 年来在 NGC 6946 中观察到的十颗超新星中任何一颗的光回波来测试我们的方法。我们没有发现光回波高于 1$\times$10$^{-15}$erg/s/cm$^2$/arcsec$^2$ 的调查表面亮度限制的证据。