2008A&A...487..645R


C.D.S. - SIMBAD4 rel 1.7 - 2019.12.06CET14:13:32

2008A&A...487..645R - Astronomy and Astrophysics, volume 487, 645-657 (2008/8-4)

On the reliability of mass-loss-rate estimates for AGB stars.

RAMSTEDT S., SCHOEIER F.L., OLOFSSON H. and LUNDGREN A.A.

Abstract (from CDS):

In the recent literature there has been some doubt as to the reliability of CO multi-transitional line observations as a mass-loss-rate estimator for AGB stars. Using new well-calibrated CO radio line observations, the main aim of the work presented here is to carefully evaluate the reliability of CO mass-loss-rate estimates for intermediate- to high-mass-loss-rate AGB stars with different photospheric chemistries.Mass-loss rates for 10 intermediate- to high-mass-loss-rate AGB stars are derived using a detailed non-LTE, non-local radiative transfer code based on the Monte-Carlo method to model the CO radio line intensities. The circumstellar envelopes are assumed to be spherically symmetric and formed by constant mass-loss rates. The energy balance is solved self-consistently and the effects of dust on the radiation field and thermal balance included. An independent estimate of the mass-loss rate is also obtained from the combination of dust radiative transfer modelling with a dynamical model of the gas and dust particles.We find that the CO radio line intensities and shapes are successfully reproduced for the majority of our objects when assuming a constant mass-loss rate. Moreover, the CO line intensities are only weakly dependent on the adopted micro-turbulent velocity, in contrast to recent claims in the literature. The two methods used in the present work to derive mass-loss rates are consistent within a factor of ∼3 for intermediate- to high-mass-loss-rate objects, indicating that this is a lower limit to the uncertainty in present mass-loss-rate estimates. We find a tentative trend with chemistry. Mass-loss rates from the dust/dynamical model are systematically higher than those from the CO model for the carbon stars and vice versa for the M-type stars. This could be ascribed to a discrepancy in the adopted CO/H2-abundance ratio, but we caution that the sample is small and systematic errors cannot be excluded.

Abstract Copyright:

Journal keyword(s): stars: AGB and post-AGB - stars: carbon - stars: late-type - stars: mass-loss

Simbad objects: 10

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Number of rows : 10

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 IRC +10011 OH* 01 06 25.9889735162 +12 35 52.890666456   20.7   18.26 14.01 M8 392 0
2 LEE 259 C* 03 26 29.5050382299 +47 31 48.463099623           N 165 0
3 V* IK Tau Mi* 03 53 28.8884898148 +11 24 21.865959095 16.99 17.03 13.39 7.29 3.20 M7-11 560 0
4 V* TX Cam Mi* 05 00 51.1569959503 +56 10 54.093107078       14.02   M9-9.5 326 0
5 V* GX Mon OH* 06 52 47.0411386021 +08 25 19.131304542   15.40 15.46 10.56   M9 104 0
6 IRC +10216 C* 09 47 57.406 +13 16 43.56     10.96     C9,5e 2109 0
7 V* RW LMi C* 10 16 02.2834693816 +30 34 18.977096332       15.27   C4,3e 377 0
8 IRC -10529 OH* 20 10 27.8733409252 -06 16 13.757843352         15.49 M: 130 0
9 RAFGL 3068 C* 23 19 12.607 +17 11 33.13           C 247 0
10 IRC +40540 C* 23 34 27.5215563443 +43 33 01.299562617     15.12     C8,3.5eJ 170 0

    Equat.    Gal    SGal    Ecl

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2019.12.06-14:13:32

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