Simultaneous observations of maser lines of 28SiO in evolved stars *
J.R. Pardo 1, 2, 3,
J. Cernicharo 4, 2,
E. González-Alfonso 5, 2 and
V. Bujarrabal 2
Received 21 May 1997 / Accepted 7 August 1997
We present simultaneous observations of several rotational lines of 28SiO in the v=1, 2, 3, and 4 vibrationally excited states toward O-rich evolved stars. All the data were taken in a relatively short period of 65 days, which allows a comparative study of the 28SiO maser lines intensities and profiles.
The observed differences concerning intensity and line shape among the different maser lines suggest that infrared overlaps deeply affect the pumping of some SiO masers. We qualitatively discuss this effect with consideration to the IR overlaps at 8 m between the various SiO isotopomers and between 28SiO and water vapor.
Key words: stars: AGB, post-AGB masers stars: circumstellar matter radio-lines: stars
* Tables 5 to 16 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (22.214.171.124) or via http://cdsweb.u-strasbg.fr/Abstract.htlm.
Send offprint requests to: J.R. Pardo
© European Southern Observatory (ESO) 1998
Online publication: November 24, 1997