Contents of: VI/111/./abstract/MBARLOW_OH.abs

The following document lists the file abstract/MBARLOW_OH.abs from catalogue VI/111.
A plain copy of the file (without headers/trailers) may be downloaded.

These observations aim to directly investigate, for the first time, the
operation of the proposed IR radiative pump mechanism for the OH maser
emission observed from cool AGB and supergiant stars. The proposed OH
maser pump scheme involves absorption in the 34.6um and 53.3um doublets
from the OH 2Pi(3/2) J = 3/2 ground rotational state state, to excited
2Pi(1/2) rotational states, followed by a cascade network back to the
ground state, involving the emission of photons at 98.7, 163.2 and 79.1um;
and at 48.7, 96.3 and 119.2um, leading to inversion of the ground state
hyperfine state populations and maser emission. The 34.6 and 53.3um
pump lines will be observed with the SWS and LWS Fabry-Perots (FPs),
respectively, while all the predicted cascade lines will be observed
with the LWS FPs.
The proposal requests time to supplement observations begun in the LWS
Consortium's GT programme MBARLOW.HIRES. Originally, the OH lines from 15
stars were to be observed with the LWS and SWS FPs. However, the decreased
in-flight sensitivities of the LWS and SWS, due to the higher than expected
particle hit-rates, led to a large increase in the required exposure times.
As a result only two sources (the F8Ia supergiant IRC+10420 and the archetype
OH/IR star WX Psc = IRC+10011) can now be observed within the 14 hours
available in the LWS HIRES programme. We request sufficient time to add four
more bright archetypal OH maser sources to the sample, namely the mainline
(Type I) OH maser source W Hya (a semi-regular variable), the mixed 1612 MHz
and mainline (Type I/II) maser source IK Tau (a Mira variable), the very red
OH/IR source OH26.5+0.6 (a very strong 1612 MHz, or Type II, OH maser source)
and NML Cyg, an extremely luminous non-variable M supergiant Type II OH maser
source. Our GT OH observations of WX Psc unfortunately have a relatively low
scheduling priority (Grade 4). Since the required observation time is lengthy,
they thus have a low probability of getting scheduled. We therefore request
an upgrade of the Priority of this source to 1 (=Grade 8).

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