| Description |
We have found during our GT line survey of IRC+10216 and the search
for hydrides (OT1 proposal) that some molecular lines present a
strong intensity variation with time due to the role of infrared pumping.
For some lines the intensity change in six months reaches a factor 3
(CCH). We have checked that the effect is not instrumental and than it
arises from physical processes ignored so far in the radiative transfer
models.
We propose to observe the CCH and HNC lines within bands 1a-5b of HIFI
every four months (three observing slots) to allow a detailed study of the
variation of thermal molecular emission, and dust emission, in this prototype
of AGB C-rich object. The settings will also provide, as a bonus, many lines of
SiO, SiS, CS, HCN, CO and 13CO for which intensity variations of up to 30% have
been found. In addition, a few specificc settings for HCN and CO will complete
the observations. SPIRE and PACS observations will complement, with lower spectral
resolution, the whole spectrum of each of these molecules and will provide a
global view of the total intensity change of these lines with time. A crude
estimate of the distance could be also obtained from the observed time lags between
the blue and red parts of the line profiles observed with HIFI. |
