  We have previously analyzed sensitive mid-infrared observations to establish
that the Pipe Nebula has a very low star-formation efficiency. That study
focused on YSOs with excess infrared emission (i.e, protostars and pre-main
sequence stars with disks), however, and could have missed a population of more
evolved pre-main sequence stars or Class III objects (i.e., young stars with
dissipated disks that no longer show excess infrared emission). Evolved
pre-main sequence stars are X-ray bright, so we have used ROSAT All-Sky Survey
data to search for diskless pre-main sequence stars throughout the Pipe Nebula.
We have also analyzed archival XMM-Newton observations of three prominent areas
within the Pipe: Barnard 59, containing a known cluster of young stellar
objects; Barnard 68, a dense core that has yet to form stars; and the Pipe
molecular ring, a high-extinction region in the bowl of the Pipe. We
additionally characterize the X-ray properties of YSOs in Barnard 59. The ROSAT
and XMM-Newton data provide no indication of a significant population of more
evolved pre-main sequence stars within the Pipe, reinforcing our previous
measurement of the Pipe's very low star formation efficiency.
