Technetium and the third dredge up in AGB stars - I. Field stars

  title={Technetium and the third dredge up in AGB stars - I. Field stars},
  author={Thomas Lebzelter and J. Hron},
  journal={Astronomy and Astrophysics},
Context. Technetium (Tc) is an unstable element synthesised via the s-process in deep layers of asymptotic giant branch (AGB) stars, making it a reliable indicator of both recent s-process activity and third dredge-up. Aims. We searched for Tc in a sample of bright oxygen-rich asymptotic giant branch (AGB) stars located in the outer galactic bulge. We test theoretical predictions of the luminosity limit for the onset of third dredge-up. Methods. Using high-resolution optical spectra obtained… Expand

Figures and Tables from this paper

UVES and CRIRES Spectroscopy of AGB Stars: Technetium and the Third Dredge-up
We present high-resolution UVES and CRIRES spectra of bright Oxygen-rich asymptotic giant branch (AGB) stars located in the outer galactic bulge. The UVES spectra were searched for absorption linesExpand
Correlation between technetium and lithium in a sample of oxygen-rich AGB variables ⋆
Context. 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 intoExpand
Spectral analysis of the barium central star of the planetary nebula Hen 2−39
Context. Barium stars are peculiar red giants characterized by an overabundance of the elements synthesized in the slow neutron-capture nucleosynthesis (s-process elements) along with an enrichmentExpand
AGB stars of the intermediate-age LMC cluster NGC 1846 II. Dredge up along the AGB
Aims. We investigate the change in the surface abundance of 12 C during the evolution along the AGB, aiming to constrain third dredge-up models. Methods. High-resolution, near-infrared spectra of aExpand
Period -- mass-loss rate relation of Miras with and without technetium
Aims: We report the discovery that Mira variables with and without absorption lines of the element technetium (Tc) occupy two different regions in a diagram of near- to mid-infrared colour versusExpand
Interplay between pulsation, mass loss, and third dredge-up: More about Miras with and without technetium
Context. We follow-up on a previous finding that AGB Mira variables containing the third dredge-up indicator technetium (Tc) in their atmosphere form a different sequence of K − [22] colour as aExpand
Carbon and oxygen isotopic ratios for nearby miras
C and O isotopic ratios are reported for a sample of 46 Mira and SRa-type variable AGB stars. Vibration-rotation 1st and 2nd overtone CO lines in 1.5 to 2.5 $\mu$m spectra were measured to deriveExpand
Galactic vs. extragalactic origin of the peculiar transient SCP 06F6
Abstract We study four scenarios for the SCP 06F6 transient event that was announced recently. Some of these were previously briefly discussed as plausible models for SCP 06F6, in particular with theExpand
We present rotational and radial velocities for a sample of 761 giants selected from the Hipparcos Catalogue to lie within 100 pc of the Sun. Our original goal was to examine stellar rotation inExpand
On the role of doubly-diffusive mixing in low-mass red giant branch stars
The purpose of this thesis is to investigate mixing in red-giant stars. Thanks particularly to the observations of globular clusters, it is clear that that standard stellar evolution fails toExpand


Nucleosynthesis and Mixing on the Asymptotic Giant Branch. III. Predicted and Observed s-Process Abundances
We present the results of s-process nucleosynthesis calculations for asymptotic giant branch (AGB) stars of different metallicities and different initial stellar masses (1.5 and 3 M☉), and we presentExpand
86 GHz SiO maser survey of late-type stars in the Inner Galaxy IV. Bolometric magnitudes
We present a study of DENIS, 2MASS, ISOGAL and MSX photometry for a sample of evolved latentype stars in the inner Galaxy, which we previously searched for 86 GHz SiO maser emission (Messineo et al.Expand
s-Process nucleosynthesis in carbon stars
We present the first detailed and homogeneous analysis of the s-element content in Galactic carbon stars of N type. Abundances of Sr, Y, Zr (low-mass s-elements, or ls), Ba, La, Nd, Sm, and CeExpand
Infrared stellar populations in the central parts of the Milky Way galaxy
Near- and mid-IR survey data from DENIS and ISOGAL are used to investigate the structure and formation history of the inner 10 ◦ (1.4 kpc) of the Milky Way galaxy. Synthetic bolometric correctionsExpand
A synthetic view on structure and evolution of the Milky Way
Since the Hipparcos mission and recent large scale surveys in the optical and the near-infrared, new constraints have been obtained on the structure and evolution history of the Milky Way. TheExpand
Evolution and Nucleosynthesis in Low-Mass Asymptotic Giant Branch Stars. I. Formation of Population I Carbon Stars
New models of thermally pulsing asymptotic giant branch (TP-AGB) stars of low mass and solar chemical composition are presented, namely, 1 ≤ M/M☉ ≤ 3, Z = 0.02, and Y = 0.28. The influence of variousExpand
Age and Metallicity Distribution of the Galactic Bulge from Extensive Optical and Near-IR Stellar Photometry
We present a new determination of the metallicity distribution, age, and luminosity function of the Galactic bulge stellar population. By combining near-IR data from the 2MASS survey, from the SOFIExpand
Long-period variables in the Large Magellanic Cloud. II. Infrared photometry, spectral classification, AGB evolution, and spatial distribution
Infrared JHK photometry and visual spectra have been obtained for a large sample of long-period variables (LPVs) in the Large Magellanic Cloud (LMC). Various aspects of the asymptotic giant branchExpand
MS and S stars with and without Tc.
The study fits the elemental abundances observed in MS and S giants using self-consistent models of nucleosynthesis and dredge-up for the TP-AGB evolutionary phases of low-mass stars. The initialExpand
High-mass-loss AGB Stars in the South Galactic Cap
Observations are presented for 61 Miras in the South Galactic Cap (b<−30°) which were selected on the basis of their IRAS 12/25-μm flux ratios as high-mass-loss candidates. JHKL photometry (over 1Expand