The unusual nature of nova HR Delphini 1967.

Unlike most other classical novae HR Del had a very slow final rise to maximum light, with special spectroscopic properties. There is no reason to believe that its development after maximum was not fairly normal and interpretable in terms of an optically thick wind, as for other novae. However, the pre-maximum development suggests very low velocities near an almost stationary photosphere, unlike for the majority of classical novae in this stage. These properties indicate that HR Del only marginally satisfied the conditions for a thermonuclear runaway.