Water and Methanol Maser Survey of Protostars in the Orion Molecular
  Cloud Complex
  The results of a maser survey toward ninety-nine protostars in the Orion
molecular cloud complex are presented. The target sources are low-mass
protostars identified from infrared observations. Single-dish observations were
carried out in the water maser line at 22 GHz and the methanol class I maser
lines at 44, 95, and 133 GHz. Most of the detected sources were mapped to
determine the source positions. Five water maser sources were detected, and
they are excited by HH 1-2 VLA 3, HH 1-2 VLA 1, L1641N MM1/3, NGC 2071 IRS 1/3,
and an object in the OMC 3 region. The water masers showed significant
variability in intensity and velocity with time scales of a month or shorter.
Four methanol emission sources were detected, and those in the OMC 2 FIR 3/4
and L1641N MM1/3 regions are probably masers. The methanol emission from the
other two sources in the NGC 2071 IRS 1-3 and V380 Ori NE regions are probably
thermal. For the water masers, the number of detections per protostar in the
survey region is about 2%, which suggests that the water masers of low-mass
protostars are rarely detectable. The methanol class I maser of low-mass
protostars is an even rarer phenomenon, with a detection rate much smaller than
1%.
