2003A&A...402..617W


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.03CET03:33:29

2003A&A...402..617W - Astronomy and Astrophysics, volume 402, 617-634 (2003/5-1)

Molecular abundances in carbon-rich circumstellar envelopes.

WOODS P.M., SCHOEIER F.L., NYMAN L.-A. and OLOFSSON H.

Abstract (from CDS):

A millimetre molecular line survey of seven high mass-loss rate carbon stars in both the northern and southern skies is presented. A total of 196 emission lines (47 transitions) from 24 molecular species were detected. The observed CO emission is used to determine mass-loss rates and the physical structure of the circumstellar envelope, such as the density and temperature structure, using a detailed radiative transfer analysis. This enables abundances for the remaining molecular species to be determined. The derived abundances generally vary between the sources by no more than a factor of five indicating that circumstellar envelopes around carbon stars with high mass-loss rates have similar chemical compositions. However, there are some notable exceptions. The most striking difference between the abundances are reflecting the spread in the 12C/13C-ratio of about an order of magnitude between the sample stars, which mainly shows the results of nucleosynthesis. The abundance of SiO also shows a variation of more than an order of magnitude between the sources and is on average more than an order of magnitude more abundant than predicted from photospheric chemistry in thermal equilibrium. The over-abundance of SiO is consistent with dynamical modelling of the stellar atmosphere and the inner parts of the wind where a pulsation-driven shock has passed. This scenario is possibly further substantiated by the relatively low amount of CS present in the envelopes. The chemistry occurring in the outer envelope is consistent with current photochemical models.

Abstract Copyright:

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

Simbad objects: 9

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Number of rows : 9

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 RAFGL 618 pA* 04 42 53.6245215366 +36 06 53.397219192   16.32   12.59   C-rich 963 0
2 RAFGL 4078 C* 07 45 02.4140089106 -71 19 45.852846228       15.92 12.72 C 47 0
3 IRC +10216 C* 09 47 57.40632 +13 16 43.5648     10.96     C9,5e 2178 0
4 V* RW LMi C* 10 16 02.2834693816 +30 34 18.977096332       15.27   C4,3e 382 0
5 RAFGL 4211 C* 15 11 41.4387312231 -48 19 58.763122448           C-rich 47 0
6 WOS 48 C* 15 23 05.0744336371 -51 25 58.881494593   17.85 16.66 14.51 10.18 C 121 1
7 V* V1610 Cyg pA* 21 02 18.27 +36 41 37.0           F5Iae 837 1
8 RAFGL 3068 C* 23 19 12.60744 +17 11 33.1332           C 256 0
9 IRC +40540 C* 23 34 27.5215563443 +43 33 01.299562617     15.12     C8,3.5eJ 171 0

    Equat.    Gal    SGal    Ecl

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2021.03.03-03:33:29

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