2001ApJ...548L..77L

1612 MHz observations of the OH/IR star IRAS 18455+0448 in 1998 June showed that its peak intensity had faded by a factor of 20 from its 2.09 Jy discovery intensity in 1988. Its peak intensity, when observed at constant resolution, has faded exponentially since by a further factor of 10, with an e-folding time of 319 days. This decline is seemingly inexorable, even though the main line OH masers are as yet largely unaffected, as the correlation between the expansion velocities and periods of OH/IR stars suggests a likely period of ∼400 days for 18455+0448 as a long-period variable, and our observations cover 706 days. We argue that extant data are best understood if we are witnessing an early stage in the expansion of a fossil circumstellar shell around 18455+0448, prior to it becoming a planetary nebula.