2017A&A...606A..20P


C.D.S. - SIMBAD4 rel 1.7 - 2021.05.15CEST23:48:47

2017A&A...606A..20P - Astronomy and Astrophysics, volume 606A, 20-20 (2017/10-1)

Rubidium and zirconium abundances in massive Galactic asymptotic giant branch stars revisited.

PEREZ-MESA V., ZAMORA O., GARCIA-HERNANDEZ D.A., PLEZ B., MANCHADO A., KARAKAS A.I. and LUGARO M.

Abstract (from CDS):

Context. Luminous Galactic OH/IR stars have been identified as massive (>4-5M) asymptotic giant branch (AGB) stars experiencing hot bottom burning and Li production. Their Rb abundances and [Rb/Zr] ratios, as derived from classical hydrostatic model atmospheres, are significantly higher than predictions from AGB nucleosynthesis models, posing a problem for our understanding of AGB evolution and nucleosynthesis.
Aims. We report new Rb and Zr abundances in the full sample (21) of massive Galactic AGB stars, previously studied with hydrostatic models, by using more realistic extended model atmospheres.
Methods. For this, we use a modified version of the spectral synthesis code Turbospectrum and consider the presence of a circumstellar envelope and radial wind in the modelling of the optical spectra of these massive AGB stars. The Rb and Zr abundances are determined from the 7800Å Rb I resonant line and the 6474Å ZrO bandhead, respectively, and we explore the sensitivity of the derived abundances to variations of the stellar (Teff) and wind (M, β and vexp) parameters in the pseudo-dynamical models. The Rb and Zr abundances derived from the best spectral fits are compared with the most recent AGB nucleosynthesis theoretical predictions.
Results. The Rb abundances derived with the pseudo-dynamical models are much lower (in the most extreme stars even by ∼1-2 dex) than those derived with the hydrostatic models, while the Zr abundances are similar. The Rb I line profile and Rb abundance are very sensitive to the wind mass-loss rate M (especially for M≳10–8M/yr) but much less sensitive to variations of the wind velocity-law (β parameter) and the expansion velocity vexp(OH).
Conclusions. We confirm the earlier preliminary results based on a smaller sample of massive O-rich AGB stars, suggesting that the use of extended atmosphere models can solve the discrepancy between the AGB nucleosynthesis theoretical models and the observations of Galactic massive AGB stars. The Rb abundances, however, are still strongly dependent on the wind mass-loss M, which, unfortunately, is unknown in these AGB stars. Accurate mass-loss rates M (e.g. from rotationally excited lines of the CO isotopologues in the radio domain) in these massive Galactic AGB stars are needed in order to break the model's degeneracy and obtain reliable (non-model-dependent) Rb abundances in these stars.

Abstract Copyright: © ESO, 2017

Journal keyword(s): stars: AGB and post-AGB - stars: atmospheres - stars: abundances - stars: evolution - stars: late-type - nuclear reactions, nucleosynthesis, abundances - nuclear reactions, nucleosynthesis, abundances

Simbad objects: 29

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Number of rows : 29

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 IC 1613 GiC 01 04 54.2 +02 08 00   10.42 10.01 9.77   ~ 1132 2
2 IRC +10011 OH* 01 06 25.9889735162 +12 35 52.890666456   20.7   18.26 14.01 M8 406 0
3 IRC +30021 Mi* 01 11 15.9342978462 +30 38 06.242372347       13.73   M10 75 0
4 OH 127.8 -0.0 OH* 01 33 51.21 +62 26 53.2           M9III 175 0
5 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5935 1
6 V* SY Men Mi* 04 39 16.0902563395 -74 21 41.877310784           ~ 29 0
7 V* T Lep Mi* 05 04 50.8454453444 -21 54 16.512268623   10.99 7.40     M6ev 137 0
8 V* U Dor Mi* 05 10 08.8409471173 -64 19 04.275078260   11.86 8.10     M8IIIe 57 0
9 IRC +50137 Mi* 05 11 19.4489549676 +52 52 33.222548186           M10 172 0
10 IRC +60154 OH* 05 19 52.1463197882 +63 15 54.958140641       16.24   M9 61 0
11 V* AP Lyn Mi* 06 34 33.3973987916 +60 56 27.785534488   12.51 11.15 11.90   M7+ 108 0
12 IRAS 07222-2005 * 07 24 24.4239414946 -20 11 56.087791598         12.26 M9: 8 0
13 V* MQ Vel OH* 09 21 18.4675119754 -45 30 56.812932834           M7/9S? 10 0
14 V* VZ Vel Mi* 10 28 11.0076814307 -51 11 07.681516278   11.96 10.87     M7 21 0
15 IRAS 14266-4211 OH* 14 29 51.6406239932 -42 25 06.400946684           ~ 8 0
16 V* S CrB Mi* 15 21 23.9560807971 +31 22 02.567988144 7.51 7.15 5.80     M6.5-8e 337 0
17 V* FS Lib Mi* 16 00 23.7719822775 -12 20 57.345091415     15     M7/9 51 0
18 V* V1012 Her Mi* 16 05 28.8975098573 +42 10 29.500104454           M8 20 0
19 V* V345 Nor Mi* 16 06 51.6831694675 -52 04 34.788509382     14.10     ~ 10 1
20 V* V850 Oph Mi* 17 06 10.8067628842 -10 28 59.156924497     15     M8 20 0
21 OH 26.5 +0.6 OH* 18 37 32.50920 -05 23 59.1936           O-rich 286 0
22 V* V3952 Sgr Mi* 18 45 51.3310415431 -17 17 59.657932290   12.77 11.61     M9 25 0
23 IRC -20540 OH* 19 08 54.9265603412 -22 14 18.578913052     17 14.58 10.55 M8: 74 0
24 OH 44.8 -2.3 OH* 19 21 36.6418599501 +09 27 56.536908744           ~ 84 0
25 IRAS 19426+4342 OH* 19 44 16.5 +43 49 20           ~ 5 0
26 IRC +10451 Mi* 20 07 43.0497066113 +06 03 11.963724548           M9 35 0
27 IRC -10529 OH* 20 10 27.8733409252 -06 16 13.757843352         15.49 M: 135 0
28 V* RT Mic Mi* 20 37 22.9227553351 -30 10 26.147769889           O-rich 13 0
29 NSV 25875 OH* 22 19 27.48 +59 51 21.7           ~ 134 0

    Equat.    Gal    SGal    Ecl

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2021.05.15-23:48:47

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