We present near-infrared spectroscopy of the 2022 eruption of the recurrent nova U Sco, over the period from 5.2 to 45.4 days after outburst. This is the most intensive infrared study of this nova. Our observations started early after the outburst and extended almost to the end of the ‘Super Soft’ X-ray phase. A major find is the presence of coronal lines from day 9.41, one of the earliest appearances of these in any nova, classical or recurrent. The temperature of the coronal gas is 7 × 105 K. There is also evidence for the presence of much cooler (≲ 2.5 × 104 K) gas. Remarkable changes are seen in the Hei 1.083μm line, the strength of which declines, then recovers, in anti-correlation with the X-ray behaviour. We conclude that shock ionisation is the dominant excitation mechanism for the coronal line emission. There is evidence in the infrared spectra for the presence of black body emission at ∼20000 K, which we tentatively identify with the irradiated secondary, and for free-free/free-bound emission. For the previously determined binary inclination of 82.○7, the implied ejection velocities are as high as 22000kms−1. These velocities appear unprecedented in nova outflows, and are comparable to those seen in supernovae, thereby marking U Sco as a truly remarkable object.
LISREL Analysis is suggested as a method of modeling relationships among variables to determine causality. LISREL is a computer program that uses a maximum-likelihood procedure to analyze structural equations. The variables in the tested hypotheses can be both directly observed variables and latent variables. LISREL was applied to the findings of a study in drug education research in order to provide a model. The constructed LISREL model was contrasted with the ANOVA-based model. The LISREL had greater explanatory value for dealing with antecedent variables present in complex human health behaviors.
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