2020A&A...641A..57M


C.D.S. - SIMBAD4 rel 1.7 - 2020.12.05CET00:51:36

2020A&A...641A..57M - Astronomy and Astrophysics, volume 641A, 57-57 (2020/9-1)

The abundance of S- and Si-bearing molecules in O-rich circumstellar envelopes of AGB stars.

MASSALKHI S., AGUNDEZ M., CERNICHARO J. and VELILLA-PRIETO L.

Abstract (from CDS):


Aims. 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.
Methods. We surveyed a sample of 30 oxygen-rich AGB stars in the λ 2 mm band using the IRAM 30m telescope. We performed excitation and radiative transfer calculations based on the large velocity gradient method to model the observed lines of the molecules and to derive their fractional abundances in the observed envelopes.
Results. We detected SiO in all 30 targeted envelopes, as well as CS, SiS, SO, and SO2 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 .
Conclusions. 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.

Abstract Copyright: © ESO 2020

Journal keyword(s): astrochemistry - molecular processes - stars: abundances - stars: AGB and post-AGB - circumstellar matter

VizieR on-line data: <Available at CDS (J/A+A/641/A57): spectrum.dat oslines.fits>

Status at CDS : Tables of objects will be appraised for possible ingestion in SIMBAD.

Simbad objects: 32

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Number of rows : 32

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 V* KU And Mi* 00 06 52.7551927308 +43 05 02.356209801       14.12   M10 75 0
2 IRC +10011 OH* 01 06 25.9889735162 +12 35 52.890666456   20.7   18.26 14.01 M8 403 0
3 BD+06 319 PM* 02 02 38.6352807560 +07 40 36.500821146   10.92 9.84     M8 25 0
4 * omi Cet Mi* 02 19 20.79210 -02 58 39.4956   7.63 6.53 5.03   M5-9IIIe+DA 1449 0
5 V* IK Tau Mi* 03 53 28.8884898148 +11 24 21.865959095 16.99 17.03 13.39 7.29 3.20 M7-11 582 0
6 V* R Dor AB* 04 36 45.59127 -62 04 37.7974 7.84 6.98 5.40 2.71 -0.44 M8III:e 295 0
7 V* TX Cam Mi* 05 00 51.1569959503 +56 10 54.093107078       14.02   M9-9.5 333 0
8 IRC +50137 Mi* 05 11 19.4489549676 +52 52 33.222548186           M10 171 0
9 IRC +70066 Mi* 05 46 44.3250774318 +69 58 24.408023024           M9.5 76 0
10 V* AP Lyn Mi* 06 34 33.3973987916 +60 56 27.785534488   12.51 11.15 11.90   M7+ 108 0
11 V* GX Mon OH* 06 52 47.0411386021 +08 25 19.131304542   15.40 15.46 10.56   M9 107 0
12 V* R LMi Mi* 09 45 34.2832012840 +34 30 42.836146420   10.96 9.99     M6.5-9e 311 0
13 V* R Leo Mi* 09 47 33.4839808805 +11 25 43.823283729 9.22 8.94 7.53 3.39 0.12 M7-9e 882 1
14 IRC +10216 C* 09 47 57.40632 +13 16 43.5648     10.96     C9,5e 2164 0
15 V* R Crt AB* 11 00 33.8541158313 -18 19 29.574953304   10.33 9.80     M7/8III 198 0
16 V* BK Vir AB* 12 30 21.0150535628 +04 24 59.159360514 9.60 8.82 7.28     M7-III: 133 0
17 V* RT Vir AB* 13 02 37.9836301550 +05 11 08.360733054 10.07 9.07 7.41     M8III 299 0
18 V* SW Vir AB* 13 14 04.3908742003 -02 48 25.155302846 9.24 8.52 6.85     M7III: 249 0
19 V* R Hya Mi* 13 29 42.7818674 -23 16 52.774679 7.26 6.58 4.97 2.27 -0.15 M6-9e 464 0
20 V* W Hya Mi* 13 49 02.0018313132 -28 22 03.532006894   8.97 7.70     M7.5-9e 607 0
21 V* RX Boo AB* 14 24 11.6240733185 +25 42 13.381760051   9.23 8.60     M7.5-M8 421 0
22 V* S CrB Mi* 15 21 23.9560807971 +31 22 02.567988144 7.51 7.15 5.80     M6.5-8e 335 0
23 V* X Her AB* 16 02 39.1738474892 +47 14 25.258160301   7.64 6.58     M6III 225 0
24 IRC +10365 Mi* 18 37 19.2595666948 +10 25 42.492197977           M9 137 0
25 OH 26.5 +0.6 OH* 18 37 32.50920 -05 23 59.1936           ~ 286 0
26 IRC -30398 AB* 18 59 13.8657889129 -29 50 20.243409063   14.35 14.19 15.46   M9 43 0
27 V* RR Aql Mi* 19 57 36.0628075265 -01 53 11.322802573     7.80     M7.5e 281 2
28 V* V1943 Sgr AB* 20 06 55.2458545503 -27 13 29.754314126   9.25 8.04     M7/8III 70 0
29 IRC -10529 OH* 20 10 27.8733409252 -06 16 13.757843352         15.49 M: 134 0
30 V* T Cep Mi* 21 09 31.7832206157 +68 29 27.190142015 9.15 8.82 7.33     M6-9e 365 0
31 V* EP Aqr AB* 21 46 31.8467491729 -02 12 45.901666975   7.93 6.78     M7-III: 217 0
32 V* R Cas Mi* 23 58 24.8700291935 +51 23 19.691977266 6.71 6.63 4.80     M6.5-9e 683 0

    Equat.    Gal    SGal    Ecl

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2020.12.05-00:51:36

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