J/A+A/641/A57 Oxygen-rich AGB IRAM spectra (Massalkhi+, 2020)
The abundance of S- and Si-bearing molecules in O-rich circumstellar envelopes
of AGB stars.
Massalkhi S., Agundez M., Cernicharo J., Velilla-Prieto L.
<Astron. Astrophys. 641, A57 (2020)>
=2020A&A...641A..57M 2020A&A...641A..57M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Molecular data ; Spectra, radio
Keywords: astrochemistry - molecular processes - stars: abundances -
stars: AGB and post-AGB - circumstellar matter
Abstract:
We aim to determine the abundances of SiO, CS, SiS, SO, and SO2 in a
large sample of oxygen-rich asymptotic giant branch (AGB) envelopes
covering a wide range of mass loss rates to investigate the potential
role that these molecules could play in the formation of dust in these
environments. We surveyed a sample of 30 oxygen-rich AGB stars in the
λ 2mm band using the IRAM 30m telescope. We performed
excitation and radiative transfer calculations based on the large
velocity gradient (LVG) method to model the observed lines of the
molecules and to derive their fractional abundances in the observed
envelopes. We detected SiO in all 30 targeted envelopes, as well as
CS, SiS, SO, and SO 2 in 18, 13, 26, and 19 sources, respectively.
Remarkably, SiS is not detected in any envelope with a mass loss rate
below 10-6M☉/yr, whereas it is detected in all envelopes with
mass loss rates above that threshold. From a comparison with a
previous, similar study on C-rich sources, it becomes evident that the
fractional abundances of CS and SiS show a marked differentiation
between C-rich and O-rich sources, being two orders of magnitude and
one order of magnitude more abundant in C-rich sources, respectively,
while the fractional abundance of SiO turns out to be insensitive to
the C/O ratio. The abundance of SiO in O-rich envelopes behaves
similarly to C-rich sources, that is, the denser the envelope the
lower its abundance. A similar trend, albeit less clear than for SiO,
is observed for SO in O-rich sources. The marked dependence of CS and
SiS abundances on the C/O ratio indicates that these two molecules
form more efficiently in C- than O-rich envelopes. The decline in the
abundance of SiO with increasing envelope density and the tentative
one for SO indicate that SiO and possibly SO act as gas-phase
precursors of dust in circumstellar envelopes around O-rich AGB stars.
Description:
The FITS file contains the spectra of the SiO 3-2, SiS 8-7, CS 3-2,
SO 33-22, SO2 82,6-81,7, SO2 51,5-404_,
SO2 42,2-41,3 and SO2 22,0-21,1 lines of the 30
oxygen-rich AGB stars observed with the IRAM 30m telescope that are
shown in Figure 1 in the article.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
spectra.dat 55 240 List of spectra available in oslines.fits file
oslines.fits 2880 100 Oxygen stars line fits table
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See also:
J/A+AS/97/729 : JHKL'M Observations of O-Rich late-type star (Le Bertre 1993)
J/A+AS/107/445 : Envelopes of oxygen-rich AGB stars (Hashimoto, 1994)
J/A+A/314/896 : IR fluxes & photometry of oxygen-rich stars (Le Sidaner+ 1996)
J/A+AS/146/437 : IR spectra of oxygen-rich evolved stars (Speck+, 2000)
J/A+A/572/A42 : SagDIG carbon and oxygen stars (Momany+, 2014)
J/ApJ/794/81 : Oxygen-rich AGB stars maser & infrared studies (Yung+, 2014)
J/A+A/626/A112 : Halo oxygen-rich AGB stars catalog (Mauron+, 2019)
Byte-by-byte Description of file: spectra.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Star Star name
14- 28 A15 --- Line Line
31- 41 E11.5 deg RAdeg Right ascension (J2000)
44- 55 E12.5 deg DEdeg Declination (J2000)
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Acknowledgements:
Sarah Massalkhi, sarah.massalkhi(at)csic.es
(End) Patricia Vannier [CDS] 27-Aug-2020