| We present OH maser observations of a sample of 62 IRAS-selected proto-planetary nebula (PPN) candidates, and CO observations of the 29 sources in this sample which are brighter than 25 Jy in the IRAS 25 mum band. Sixteen sources have been detected in (J=1-0) or (J=2-1). We observed and detected two sources in (J=3-2). We have detected sixteen sources (four of which are CO sources) in the 1612 MHz transition of OH. Half of these are also detected at 1667 and/or 1665 MHz. The CO and OH spectra are characteristic of emission from an expanding circumstellar shell, with an average expansion velocity of ~15 kms. The OH maser sources are not variable over a period of one to five years, with only a few exceptions. Several OH sources show multiple components in their spectra, sometimes strongly circularly polarized. One double-peak OH maser source, IRAS 20406+2953, shows an enigmatic variability in circular polarization. |
Comments:
Spectral type was set to:
""S"", where only one peak was found.
""D"", where two peaks were found.
IRAS 17580-3111: Additional lines listed in Table 2 belong to IRAS 17579-3121 (blend).
Velocity resolution: 0.6 and 0.9 km/s
Upper limit for non-detections: <0.5 Jy (3σ)
If appropriate, upper limits for all transitions were calculated from the OH 1612 rms noise given in Table 1.
The observation with the strongest flux was taken, if several were listed
Left circular polarized peak flux was taken, if both polarizations were listed
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