2001AJ....122.2013L

The 0.8-2.4 µm spectroscopy of the moderately fast Nova Sgr 1998=V4633 Sgr, obtained approximately 525 and 850 days after peak brightness, revealed an expanding, hydrogen-deficient shell of medium excitation level that increased with time. The strongest lines were He I and He II and the coronal line of [Si VI] 1.9641 µm. Also prominent were the lines of H I, and coronal [Ca VIII] 2.3205 µm and [Si VII] 2.4807 µm. Other lines included the [S III] lines at 0.9069 and 0.9532 µm and the coronal lines of [Al IX] 2.0444 µm and [Ti VI] 1.7155 µm. Five lines that frequently appear in novae spectra remain unidentified: 0.8926, 1.1114, 1.1900, 1.5545, and 2.1000±0.005 µm. All the observed lines were roughly 1800 km.s^–1 wide (FWHM), and no asymmetries or underlying plateaus were seen. The continuum was significantly shallower than a 1/λ⁴ blackbody emission (approximately stellar photosphere) and steepened with age.