of the objects with stellar contamination. This example shows that a peak near the expected O VI position is present at a low level, but its interpretation is uncertain. Many hot stars contain P-Cygni wind features of varying strengths and shapes that could produce some O VI emission. On the other hand, some SNR emission could be present at an undetermined level and be masked by the variable stellar continuum. In cases such as this (indicated in Table 2), our ability to place limits on O VI are made inherently more difficult.

Thus, the quality of the upper limits varies based on the achieved integration times for each object and whether stellar contamination is present. Also, the unknown velocity widths for the undetected objects makes placing a specific upper limit rather arbitrary. We choose to adopt the method of Dixon, Sankrit, & Otte (2006), who have determined upper limits for a wide range of $\fuse$ data empirically, assuming a width appropriate for a filled LWRS aperture and the LiF1 channel, viz.

$$\rm U(1032) ~=~ \frac{273.1}{\sqrt{t_{exp}}}$$

where $\rm t_{exp}$ is the night exposure time in s, and U(1032) is a 3$\sigma$ upper limit at $\lambda$1032 in units of 1000 Line Units 