2010A&A...510A..62U


Query : 2010A&A...510A..62U

2010A&A...510A..62U - Astronomy and Astrophysics, volume 510, A62-62 (2010/2-1)

Correlation between technetium and lithium in a sample of oxygen-rich AGB variables.

UTTENTHALER S. and LEBZELTER T.

Abstract (from CDS):

The elements technetium and lithium are two important indicators of internal nucleosynthesis and mixing in late-type stars. Studying their occurrence and abundance can give deep insight into the structure and evolution in the late phases of the stellar life cycle. The aims of this paper are: 1) to revisit the Tc content of a sample of oxygen-rich (M-type) asymptotic giant branch (AGB) variables and 2) to increase the number of such stars for which the Li abundance has been measured to provide constraints on the theoretical models of extra-mixing processes. To this end, we analysed high-resolution spectra of 18 sample stars for the presence of absorption lines of Tc and Li. The abundance of the latter was determined by comparing the observed spectra to hydrostatic MARCS model spectra. Bolometric magnitudes were established from near-IR photometry and pulsation periods. We correct the classification with respect to the presence of Tc for a number of stars. We reclassify the star V441 Cyg as Tc-rich, and the unusual Mira star R Hya, as well as W Eri, as Tc-poor. The abundance of Li, or an upper limit to it, was determined for all of the sample stars. In all stars with Tc we also detected Li. Most of them have a Li content slightly below the solar photospheric value, except for V441 Cyg, which is super-Li rich with ∼1000 times the solar abundance. We also found that, similar to Tc, a lower luminosity limit seems to exist for the presence of Li. We conclude that the higher Li abundance found in the cooler and higher luminosity objects could stem from a Li production mechanism operating on the thermally pulsing AGB. The stellar mass might have a crucial influence on this (extra mixing) production mechanism. Our findings for R Hya and V441 Cyg have some important consequences for these intriguing objects. It was speculated that the declining pulsation period of R Hya is caused by a recent thermal pulse (TP). While not detecting Tc does not rule out a TP, it indicates that the TPs are not strong enough to drive 3DUP in R Hya. The pieces of evidence concerning the mass of V441 Cyg are not entirely conclusive. It could either be a low-mass, intrinsic S-star that produced its large amount of Li by extra-mixing processes, or an intermediate-mass star (M>4M) undergoing Li production via hot bottom burning.

Abstract Copyright:

Journal keyword(s): stars: AGB and post-AGB - stars: abundances - stars: evolution - stars: interiors - stars: individual: R Hya - stars: individual: V441 Cyg

Simbad objects: 23

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Number of rows : 23
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* W Cet S* 00 02 07.3895453546 -14 40 33.034389419 16.64 16.09 14.46 9.14 5.38 S5.5-7/1.5-3e 82 0
2 V* R And S* 00 24 01.9473999328 +38 34 37.326131071 10.61 9.36 7.39 4.45 2.30 S5-7/4-5e 342 0
3 V* U Cet Mi* 02 33 43.6697702618 -13 08 54.469099918   9.70 6.80     M3.5-6e 94 0
4 V* R Hor Mi* 02 53 52.7746504509 -49 53 22.732999275     3.92 4.99 1.51 M5-7e 175 0
5 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 6020 1
6 V* T Hor Mi* 03 00 52.1203742682 -50 38 31.873928537 11.19 10.14 8.69     M2/3e 61 0
7 V* TW Hor C* 03 12 33.1606201355 -57 19 17.571043687   7.93 5.71 3.78 2.40 C-N5IIIb: 127 0
8 V* W Eri Mi* 04 11 31.0251887897 -25 08 02.296637329   10.62 7.50   8.20 M7e 112 1
9 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15530 1
10 V* R Hya Mi* 13 29 42.7818674 -23 16 52.774679 7.26 6.58 4.97 2.27 -0.15 M6-9e 467 0
11 V* S Vir Mi* 13 33 00.1102954182 -07 11 41.038747753 8.87 7.96 6.68     M6-7e 174 0
12 V* ER Vir LP* 14 06 41.6447865101 -14 12 17.601305804   8.16 6.61     M4III 39 0
13 V* RU Hya Mi* 14 11 34.3986121 -28 53 07.408925   11.38 7.20     M6.5e 122 0
14 V* EV Vir LP* 14 13 09.7750234947 -13 51 35.744605288   8.43 6.88     M4-M4.5II-III 51 0
15 V* RS Vir Mi* 14 27 16.3931666073 +04 40 41.085779853   10.27 7.00     M8 202 0
16 V* Y Lib Mi* 15 11 41.30861 -06 00 41.3727   11.587 10.450     M5.5e 76 0
17 V* T Sgr S* 19 16 14.4369275919 -16 58 17.074185822   11.81 7.10     S4.5-6/5.5-6e 128 0
18 V* V441 Cyg S* 20 27 08.1155249428 +36 33 06.493962762   12.04 9.80     S4,6 46 0
19 V* U Mic Mi* 20 29 15.7816020581 -40 25 01.266705049   11.76 10.89     M5/7e 71 0
20 V* S Gru Mi* 22 26 05.4746654015 -48 26 18.743971332 7.72 7.35 6.00 8.89   M8(III)e 78 1
21 V* T Tuc Mi* 22 40 33.4801530347 -61 33 13.542562990   10.02 7.50     M5e 40 0
22 V* Y Scl LP* 23 09 05.5603140187 -30 08 02.144630134   9.86 8.70     M6III 47 0
23 NAME Galactic Bulge reg ~ ~           ~ 3656 0

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2021.09.17-18:28:58

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