Observations at the 43 GHz SiO (v=1 and 2, J=1-0) transitions were made
using the Parkes radio telescope during the period September 16-21, 1993.
At 43 GHz the inner 16.7 m of the 64 m reflector is effectively used and,
with an aperture efficiency of 34%, the telescope sensitivity is . The beam size at 43 GHz is
. Telescope pointing
errors are less than
(rms) in right ascension and declination.
We used the CSIRO 43 GHz maser superheterodyne receiver, giving typical system
temperatures in the range (SSB). All observations were
made in horizontal
linear polarization. The instantaneous bandwidth of the maser RF amplifier was
about 100 MHz, precluding simultaneous observations of the v=1 and v=2
transitions.
Measured fluxes were corrected for atmospheric attenuation using the form
, where Z is the telescope zenith angle and
, the vertical attenuation, was taken as 0.1. During the first few days of
the observations the weather was unstable with clouds and occasional rain
showers making the calibration uncertain. Apart from the data taken during
unstable weather conditions, we estimate that the flux values are accurate to
.
Spectra were obtained using a 1024-channel autocorrelator configured to give a
velocity coverage of , and a resolution before
smoothing of
. Off-line Hanning smoothing was
subsequently applied, resulting in a resolution of
.
Low-order baseline corrections have been applied to the spectra.
The 86 GHz SiO (v=1, J=2-1) observations were performed on various occasions between 1991 and 1995 using the 15m Swedish-ESO Submillimetre Telescope (SEST) and the Onsala Space Observatory 20 m telescope.
The beamwidth of the SEST is at 86 GHz, and the pointing
accuracy is estimated to be better than
(rms). The telescope was
used in a dual beam switch mode with the source alternately placed in the
two beams, a method that yields very flat baselines. The beam separation was
about
. The aperture efficiency of the telescope at 86 GHz is
62%, which gives a conversion factor of
.
The receiver was a dual (linear) polarization Schottky receiver with a typical
system temperature above the atmosphere of (SSB). Only the
horizontally
polarized receiver was used. Calibration was done with a standard chopper wheel
method and the flux values are estimated to be accurate to
.
Spectra were taken with an acousto optical spectrometer (AOS) with a bandwidth of
86 MHz (resulting in a velocity coverage of ), a
channel separation of 43 kHz, and a resolution of 80 kHz. The spectra were
subsequently smoothed by adding the spectrometer channels together four by
four, resulting in a velocity resolution of about
.
The Onsala 20 m telescope has a beamwidth of at 86 GHz, and the
pointing accuracy is estimated to be better than
(rms). The
telescope was used in a dual beam switch mode with a beam separation of
about
. The aperture efficiency of the telescope at 86 GHz is
0.5, which gives a conversion factor of
.
The receiver was a horizontally, linearly polarized SIS receiver with a
typical system temperature above the atmosphere of (SSB).
Calibration was done with a standard chopper wheel method and the flux
values are estimated to be accurate to
.
Spectra were taken with a multichannel filterbank with a bandwidth of 64 MHz,
resulting in a velocity coverage of , and a channel
separation of 250 kHz, which corresponds to a velocity resolution of
.