PW Vulpeculae - a dust-poor DG Herculis?

The paper reports 2.3-19.5 micron infrared photometry of the very slow nova PW Vul during August 12, 1984 to October 19, 1986. Some aspects of the eruptions of PW Vul and DQ Her were similar in detail, but differing physical conditions in the ejecta caused dust formation to proceed at vastly different efficiencies in the two novae. It is argued that, although an optically thin dust shell eventually condensed in the ejecta of PW Vul, the dust formation process was severely suppressed compared to classical DQ Her novae. Expansion of the pseudophotosphere implies a very slow ejection speed which is consistent with the long dust formation time. Several effects which could have suppressed the grain growth process are discussed. The nova remnant emitted between 500 and 40,000 solar luminosities 812 days after the eruption. Comparison of the photometric data for PW Vul with recent measurements of its sister nova, QU Vul, implies that the presence of silicate emission and strong fine structure line emission during the late stages of PW Vul's development cannot be completely ruled out. 43 references