NEAR-INFRARED EMISSION LINES OF V723 CASSIOPEIAE (NOVA CASSIOPEIAE 1995)

摘要

Near-infrared spectroscopy (0.8-2.5 μm) from two epochs is presented for the very slow nova V723 Cassio-peiae (=Nova Cassiopeiae 1995). Its bright, comparatively narrow emission lines (FWHM ～ 500 km s~(-1)) make it ideal for determining wavelengths of unidentified emission lines that appear in the nebular/coronal stages of novae. We present wavelengths for 16 previously unobserved or unidentified features and search for identifications by looking for coincidences with known atomic transitions. For a candidate transition, the likely abundance of the parent ion is considered and then a collisional, fluorescent, or recombination process capable of exciting the feature is sought. Four of the lines are identified in this manner, all of them collision-ally excited, forbidden transitions. One of these, [Ti Ⅶ] λ22050, is a new coronal line that de-excites directly to the ground state. Three other lines are associated with transitions from collisionally excited, low-lying, metastable levels of Fe~(+5). Of the remaining unidentified features, five, with wavelengths of 8926, 11110, 11900, 15545, and 20996 A, have been observed in other novae. Comparing the time development of these features with the [S Ⅷ] λ9913 coronal line indicates that all have parent ions of lower excitation (<280 eV) than S~(+7).