SiO rotation-vibration bands in cool giants II. The behaviour of SiO bands in AGB stars

Details SiO rotation-vibration bands in cool giants II. The behaviour of SiO bands in AGB stars SiO rotation-vibration bands in cool giants II. The behaviour of SiO bands in AGB stars

Feb 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999a%26a...342..799a&link_type=abstract

Astronomy and Astrophysics, v.342, p.799-808 (1999)

Astronomy and Astrophysics

Astrophysics

28

Infrared: Stars, Stars: Agb And Post-Agb, Stars: Late-Type, Stars: Fundamental Parameters, Stars: Atmospheres

Scientific paper

The first overtone rotation-vibration transitions of SiO give rise to prominent bandheads in the wavelength range between 4.0 and 4.5 mu m. In order to study the behaviour of these features in AGB stars we observed the 3.94 to 4.12 mu m spectra for a sample of 23 oxygen-rich late-type variables. In contrast to the SRb objects, the Miras show a very large scatter of the equivalent widths of the SiO bands. Despite their cool temperatures some of them have only weak or no SiO absorption, which seems to be related to their strong pulsations producing a large variability of the features. When comparing the band intensities with photometric data, we found a general decrease with bluer IRAS (12-25) colors. However, this trend may only reflect the different behaviour of the Miras and SRb stars in our sample. We did not discover any correlation of the equivalent widths with the effective temperatures derived from (J-K), or with the (K-12) color and the IRAS-LRS class, both of which can be regarded as a rough measure for the thickness of the circumstellar shell. In Paper I of this series (Aringer et al. \cite{siop}) we have shown that synthetic spectra calculated from hydrostatic MARCS atmospheres are successful in reproducing the observed band intensities of giants with spectral types earlier than about M5 III and M2 II\@. However, they generally predict too strong features for very cool and extended objects, as they are discussed in this work. And they fail completely when it comes to Miras with weak or no SiO absorption. These stars are dominated by dynamical phenomena and, not surprisingly, they can therefore not be described by hydrostatic structures. Thus, we have also computed synthetic spectra based on experimental dynamical models. Although they still have some shortcomings, we demonstrate that, in principle, they are able to explain the whole range of equivalent widths of the observed SiO bandheads and their variations. Based on observations made at the European Southern Observatory (ESO), La Silla (Chile)}

Affiliated with

Also associated with

No associations

Rating

SiO rotation-vibration bands in cool giants II. The behaviour of SiO bands in AGB stars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with SiO rotation-vibration bands in cool giants II. The behaviour of SiO bands in AGB stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and SiO rotation-vibration bands in cool giants II. The behaviour of SiO bands in AGB stars will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1027789