ASYMPTOTIC GIANT BRANCH STARS MIGRATION FROM THE CENTRAL OF THE MILKY WAY GALAXY TO OUR SUN’S BIRTHPLACE AND ITS RELATION WITH SILICON CARBIDE GRAINS

2013 ◽  
Vol 1 (1) ◽  
pp. 1-9
Author(s):  
Abdelhadi
Keyword(s):  
Silicon Carbide ◽  
Milky Way ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Milky Way Galaxy ◽  
Giant Branch Stars

Finite Temperature Behavior of Carbon Atom Doped Silicon Clusters: Depressed Thermal Stabilities, Co-existing isomers, Reversible Dynamical Pathways and Fragmentation Channels

2021 ◽  
Author(s):  
Krati Joshi ◽  
Ashakiran Maibam ◽  
Sailaja Krishnamurty
Keyword(s):  
Silicon Carbide ◽  
Carbon Atom ◽  
Finite Temperature ◽  
Asymptotic Giant Branch ◽  
Temperature Behavior ◽  
Asymptotic Giant Branch Stars ◽  
Silicon Clusters ◽  
Thermal Stabilities ◽  
Doped Silicon ◽  
Giant Branch Stars

Silicon carbide clusters are significant due to their predominant occurrence in meteoric star dust, particularly in carbon rich asymptotic giant branch stars. Of late, they have also been recognized as...

scholarly journals The AMBRE project: a study of Li evolution in the Galactic thin and thick discs

2017 ◽  
Vol 606 ◽  
pp. A132 ◽  
Author(s):  
N. Prantzos ◽  
P. de Laverny ◽  
G. Guiglion ◽  
A. Recio-Blanco ◽  
C. C. Worley
Keyword(s):  
Milky Way ◽  
Asymptotic Giant Branch ◽  
Red Giants ◽  
Asymptotic Giant Branch Stars ◽  
Radial Migration ◽  
Stellar Sources ◽  
Stellar Envelopes ◽  
Giant Branch Stars ◽  
Simple Picture

Context. Recent observations suggest a double-branch behaviour of Li/H versus metallicity in the local thick and thin discs. This is reminiscent of the corresponding O/Fe versus Fe/H behaviour, which has been explained as resulting from radial migration in the Milky Way disc. Aims. We study here the role of radial migration in shaping these observations. Methods. We use a semi-analytical model of disc evolution with updated chemical yields and parameterised radial migration. We explore the cases of long-lived (red giants of a few Gy lifetime) and shorter-lived (asymptotic giant branch stars of several 108 yr) stellar sources of Li, as well as those of low and high primordial Li. We show that both factors play a key role in the overall Li evolution. Results. We find that the observed two-branch Li behaviour is only directly obtained in the case of long-lived stellar Li sources and low primordial Li. In all other cases, the data imply systematic Li depletion in stellar envelopes, thus no simple picture of the Li evolution can be obtained. This concerns also the reported Li/H decrease at supersolar metallicities.

scholarly journals Lifetimes of interstellar dust from cosmic ray exposure ages of presolar silicon carbide

2020 ◽  
Vol 117 (4) ◽  
pp. 1884-1889 ◽  
Author(s):  
Philipp R. Heck ◽  
Jennika Greer ◽  
Levke Kööp ◽  
Reto Trappitsch ◽  
Frank Gyngard ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Interstellar Medium ◽  
Interstellar Dust ◽  
Particle Flux ◽  
Cosmic Ray ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Exposure Ages ◽  
Giant Branch Stars ◽  
Cosmic Ray Exposure Ages

We determined interstellar cosmic ray exposure ages of 40 large presolar silicon carbide grains extracted from the Murchison CM2 meteorite. Our ages, based on cosmogenic Ne-21, range from 3.9 ± 1.6 Ma to ∼3 ± 2 Ga before the start of the Solar System ∼4.6 Ga ago. A majority of the grains have interstellar lifetimes of <300 Ma, which is shorter than theoretical estimates for large grains. These grains condensed in outflows of asymptotic giant branch stars <4.9 Ga ago that possibly formed during an episode of enhanced star formation ∼7 Ga ago. A minority of the grains have ages >1 Ga. Longer lifetimes are expected for large grains. We determined that at least 12 of the analyzed grains were parts of aggregates in the interstellar medium: The large difference in nuclear recoil loss of cosmic ray spallation products 3He and 21Ne enabled us to estimate that the irradiated objects in the interstellar medium were up to 30 times larger than the analyzed grains. Furthermore, we estimate that the majority of the grains acquired the bulk of their cosmogenic nuclides in the interstellar medium and not by exposure to an enhanced particle flux of the early active sun.

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