2001A&A...368..969S


Query : 2001A&A...368..969S

2001A&A...368..969S - Astronomy and Astrophysics, volume 368, 969-993 (2001/3-4)

Models of circumstellar molecular radio line emission. Mass loss rates for a sample of bright carbon stars.

SCHOEIER F.L. and OLOFSSON H.

Abstract (from CDS):

Using a detailed radiative transfer analysis, combined with an energy balance equation for the gas, we have performed extensive modelling of circumstellar CO radio line emission from a large sample of optically bright carbon stars, originally observed by Olofsson et al. (1993ApJS...87..267O). Some new observational results are presented here. We determine some of the basic parameters that characterize circumstellar envelopes (CSEs), e.g., the stellar mass loss rate, the gas expansion velocity, and the kinetic temperature structure of the gas. Assuming a spherically symmetric CSE with a smooth gas density distribution, created by a continuous mass loss, which expands with a constant velocity we are able to model reasonably well 61 of our 69 sample stars. The derived mass loss rates depend crucially on the assumptions in the circumstellar model, of which some can be constrained if enough observational data exist. Therefore, a reliable mass loss rate determination for an individual star requires, in addition to a detailed radiative transfer analysis, good observational constraints in the form of multi-line observations and radial brightness distributions. In our analysis we use the results of a model for the photodissociation of circumstellar CO by Mamon et al. (1988ApJ...328..797M). This leads to model fits to observed radial brightness profiles that are, in general, very good, but there are also a few cases with clear deviations, which suggest departures from a simple r–2 density law. The derived mass loss rates span almost four orders of magnitude, from ∼5x10–9M/yr up to ∼2x10–5M/yr, with the median mass loss rate being ∼3x10–7M/yr. We estimate that the mass loss rates are typically accurate to ∼50% within the adopted circumstellar model. The physical conditions prevailing in the CSEs vary considerably over such a large range of mass loss rates. Among other things, it appears that the dust-to-gas mass ratio and/or the dust properties change with the mass loss rate. We find that the mass loss rate and the gas expansion velocity are well correlated, and that both of them clearly depend on the pulsational period and (with larger scatter) the stellar luminosity. Moreover, the mass loss rate correlates weakly with the stellar effective temperature, in the sense that the cooler stars tend to have higher mass loss rates, but there seems to be no correlation with the stellar C/O-ratio. We conclude that the mass loss rate increases with increased regular pulsation and/or luminosity, and that the expansion velocity increases as an effect of increasing mass loss rate (for low mass loss rates) and luminosity. Five, of the remaining eight, sample stars have detached CSEs in the form of geometrically thin CO shells. The present mass loss rates and shell masses of these sources are estimated. Finally, in three cases we encounter problems using our model. For two of these sources there are indications of significant departures from overall spherical symmetry of the CSEs. Carbon stars on the AGB are probably important in returning processed gas to the ISM. We estimate that carbon stars of the type considered here annually return ∼0.05M of gas to the Galaxy, but more extreme carbon stars may contribute an order of magnitude more. However, as for the total carbon budget of the Galaxy, carbon stars appear to be of only minor importance.

Abstract Copyright:

Journal keyword(s): stars: AGB and post-AGB - stars: carbon - circumstellar matter - stars: late-type - radio lines: stars

Simbad objects: 68

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Number of rows : 68
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 V* WZ Cas C* 00 01 15.8567946264 +60 21 19.025920224 8.77 9.47 7.13     C-N7III: 310 0
2 V* VX And C* 00 19 54.0161311920 +44 42 33.895984824   12.23 7.80     C-J4.5 154 0
3 V* HV Cas C* 01 11 03.4682297496 +53 43 40.246817376     12.90     C4,3e 79 0
4 Case 44 C* 01 13 44.5492749600 +62 57 36.056361096     13.71     C6,3 45 0
5 V* Z Psc C* 01 16 05.0304050160 +25 46 09.689905056 12.85 9.46 6.84     C-N5 171 0
6 V* R Scl C* 01 26 58.0939182720 -32 32 35.439234828 17.26 9.59 5.72 3.69 2.30 C-N5+ 315 0
7 V* R For C* 02 29 15.3077617632 -26 05 55.646585700   12.94 7.50     C4,3e 188 0
8 V* TW Hor C* 03 12 33.1599109680 -57 19 17.577229512   7.93 5.71 3.78 2.40 C-N5IIIb: 128 0
9 LEE 259 C* 03 26 29.5037418864 +47 31 48.551540844           N 170 0
10 HD 232820 C* 03 41 29.5964236008 +51 30 11.728132920   12.14 8.140     C5,5_MS4 67 0
11 V* U Cam C* 03 41 48.1758504744 +62 38 54.395692404   11.5 11.00     C-N5 238 0
12 V* ST Cam C* 04 51 13.3487495016 +68 10 07.637629620   9.77 9.20     C-N5 141 0
13 V* TT Tau C* 04 51 31.2645256728 +28 31 36.866648748   11.0 10.20     C-N5+ 90 0
14 V* R Lep C* 04 59 36.3486921120 -14 48 22.502479140 15.06 13.51 7.76 4.90 3.42 C7,6e 326 0
15 V* W Ori C* 05 05 23.7190712856 +01 10 39.454639032 16.36 9.52 6.10 3.83 2.35 C-N5 280 0
16 V* S Aur C* 05 27 07.4585545416 +34 08 58.849073880   13.48 8.20     C-N5+ 121 0
17 V* W Pic C* 05 43 13.8305960304 -46 27 13.825873188   12.52 11.80     C-J5 64 0
18 V* Y Tau C* 05 45 39.4101366456 +20 41 42.148590324 15.71 9.90 6.90 4.69 3.19 C-N5- 217 1
19 V* TU Gem C* 06 10 53.1027504240 +26 00 53.311175640   10.688 8.694 7.400   C-N5+ 112 0
20 V* BL Ori C* 06 25 28.1742350712 +14 43 19.172149392 11.64 8.31 6.00 4.28 2.98 C-N5- 192 0
21 V* UU Aur C* 06 36 32.8371036984 +38 26 43.819021608   7.89 5.25 3.31 1.90 C-N5- 296 1
22 V* NP Pup C* 06 54 26.6835568896 -42 21 56.058521256   8.49 6.27 4.55 3.28 C-N4.5 76 0
23 V* CL Mon C* 06 55 36.6904592496 +06 22 43.179553200   12.69 11.00     C-J:6 90 0
24 V* R Vol C* 07 05 36.2081474688 -73 00 52.034502960   14.24 8.70     Ce 81 0
25 V* RY Mon C* 07 06 56.4753359184 -07 33 26.505848700   11.94 7.50     C-N5 91 0
26 V* W CMa C* 07 08 03.4360567560 -11 55 23.796162984 13.44 8.98 6.56 4.86 3.51 C-N5 117 0
27 V* X Cnc C* 08 55 22.8819374952 +17 13 52.583009880   9.63 6.40 4.29 2.90 C-N4.5 263 1
28 IRC +10216 C* 09 47 57.40632 +13 16 43.5648     10.96     C9,5e 2246 0
29 V* Y Hya C* 09 51 03.7177289688 -23 01 02.351120088 17.75 10.45 6.63     C-N4.5III: 109 0
30 V* X Vel C* 09 55 26.1116280096 -41 35 12.779975508   10.29 10.30 7.13 8.80 C-N3 65 0
31 V* SZ Car C* 09 59 51.7122271872 -60 13 06.041587944   10.6 10.00     C-N4.5 40 0
32 V* RW LMi C* 10 16 02.2777043904 +30 34 19.045098516       15.27   C4,3e 386 0
33 V* XZ Vel C* 10 17 27.9828337512 -50 05 49.947761508   12.90 12.00     C-N:5 26 0
34 V* CZ Hya C* 10 27 18.0392692104 -25 32 56.305848336   12.44 9.71 10.55   Ce 53 0
35 V* U Ant C* 10 35 12.8510147472 -39 33 45.324020448 15.32 8.22 5.38 3.18 1.86 C-N3 142 0
36 V* U Hya C* 10 37 33.2729535 -13 23 04.352923 13.29 7.51 4.82 3.05 1.78 C-N5 291 0
37 V* VY UMa C* 10 45 04.0305312384 +67 24 40.979062260 12.91 8.34 5.95 4.20 2.94 C-N5 194 0
38 V* SS Vir C* 12 25 14.3948245008 +00 46 10.946740368 15.84 10.79 6.60     C-N4.5: 199 1
39 V* Y CVn C* 12 45 07.8260815656 +45 26 24.926308404 14.03 7.41 4.87 3.12 1.74 C-N5 468 0
40 V* RY Dra C* 12 56 25.9112361600 +65 59 39.811665876 15.56 9.44 6.34 4.34 2.91 C-N3III: 232 0
41 V* V1302 Cen C* 13 58 17.1148962816 -56 21 11.298686220   10.43 7.44     C 30 0
42 V* V996 Cen C* 14 14 07.3492293528 -53 55 55.167963528   10.55 7.25     C 37 0
43 V* X TrA C* 15 14 19.1755012584 -70 04 46.113298104 15.88 9.19 5.81     C5,5 111 0
44 V* V CrB C* 15 49 31.3121978280 +39 34 17.892629256     6.90     C6,2e_MS3 255 0
45 V* TW Oph C* 17 29 43.6639675104 -19 28 22.866171888   12.95 8.79 7.54 8.70 C-N5 113 0
46 V* T Dra C* 17 56 23.3288487384 +58 13 06.783372804   18.08 7.20     C6,2e 182 0
47 V* T Lyr C* 18 32 20.0767626264 +36 59 55.635218376   12.74 7.84 7.30   C-J4:p 177 1
48 V* DR Ser C* 18 47 21.0231862728 +05 27 18.606270960   13.39 10.40     C5,4 72 0
49 V* S Sct C* 18 50 20.0367791256 -07 54 27.429169356 13.93 9.89 6.80     C-N5 202 0
50 V* V Aql C* 19 04 24.1544971752 -05 41 05.444321424   11.09 6.90     C-N5 208 0
51 V* V1942 Sgr C* 19 19 09.5936050560 -15 54 30.030582960 13.53 9.20 6.86 5.05 3.67 C-N5+ 71 0
52 V* UX Dra C* 19 21 35.5182299784 +76 33 34.557161688   8.81 5.94     C-N5 195 0
53 V* AQ Sgr C* 19 34 18.9945475487 -16 22 27.048908541 13.85 9.48 6.70     C-N5 114 0
54 V* TT Cyg C* 19 40 57.0158460384 +32 37 05.756696400   10.43 10.20     C-N5- 195 0
55 C* 2792 C*? 19 46 59.8 +31 39 41           ~ 5 0
56 V* RT Cap C* 20 17 06.5287791168 -21 19 04.466353512   12.92 8.90     C6,4 121 0
57 V* U Cyg C* 20 19 36.5946317760 +47 53 39.096681828   11.85 5.90     C9,2e 229 0
58 V* V Cyg C* 20 41 18.2676815496 +48 08 28.810980420   14.05 7.70     C7,4eJ 298 0
59 V* RV Aqr C* 21 05 51.7376905368 -00 12 42.121057536     11.5     C6,3e 100 0
60 V* T Ind C* 21 20 09.4835040168 -45 01 18.808630176 12.08 8.33 6.00     C7,2 86 0
61 V* Y Pav C* 21 24 16.7499375384 -69 44 01.960245204 12.63 9.23 6.41     C7,3 80 0
62 LEE 228 C* 21 34 07.4785393032 +39 04 15.918662712   16.72 11.90     C7,2e 110 0
63 V* S Cep C* 21 35 12.8233100592 +78 37 28.185141792   12.13 7.40     C7,3e 254 0
64 V* V460 Cyg C* 21 42 01.0830893088 +35 30 36.719916552 12.97 8.32 5.84 4.10 2.71 C-N5 206 1
65 V* RV Cyg C* 21 43 16.3287822384 +38 01 02.979540552   12.01 10.80     C-N5: 127 0
66 LEE 338 C* 21 44 28.7966422416 +73 38 04.892089668   13.27 9.82 8.47   C6-,3e 55 0
67 IRC +40540 C* 23 34 27.5185864392 +43 33 01.323347256     15.12     C8,3.5eJ 174 0
68 * 19 Psc C* 23 46 23.5164473376 +03 29 12.519049272 10.95 7.62 5.02 3.19 1.82 C-N6 439 0

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2022.08.09-13:02:30

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