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 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.

Observations of High Rotational CO Lines in Post–Asymptotic Giant Branch Stars and Planetary Nebulae

1997 ◽  
Vol 476 (1) ◽  
pp. 319-326 ◽  
Author(s):  
K. Justtanont ◽  
A. G. G. M. Tielens ◽  
C. J. Skinner ◽  
Michael R. Haas
Keyword(s):  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Giant Branch Stars

scholarly journals Carbon stars as standard candles – II. The median J magnitude as a distance indicator

2020 ◽  
Vol 501 (1) ◽  
pp. 933-947
Author(s):  
Javiera Parada ◽  
Jeremy Heyl ◽  
Harvey Richer ◽  
Paul Ripoche ◽  
Laurie Rousseau-Nepton
Keyword(s):  
Luminosity Function ◽  
Asymptotic Giant Branch ◽  
Distance Modulus ◽  
Asymptotic Giant Branch Stars ◽  
Luminosity Functions ◽  
Best Fitting ◽  
Distance Indicator ◽  
Ngc 6822 ◽  
The Given ◽  
Giant Branch Stars

ABSTRACT We introduce a new distance determination method using carbon-rich asymptotic giant branch stars (CS) as standard candles and the Large and Small Magellanic Clouds (LMC and SMC) as the fundamental calibrators. We select the samples of CS from the ((J − Ks)0, J0) colour–magnitude diagrams, as, in this combination of filters, CS are bright and easy to identify. We fit the CS J-band luminosity functions using a Lorentzian distribution modified to allow the distribution to be asymmetric. We use the parameters of the best-fitting distribution to determine if the CS luminosity function of a given galaxy resembles that of the LMC or SMC. Based on this resemblance, we use either the LMC or SMC as the calibrator and estimate the distance to the given galaxy using the median J magnitude ($\overline{J}$) of the CS samples. We apply this new method to the two Local Group galaxies NGC 6822 and IC 1613. We find that NGC 6822 has an ‘LMC-like’ CS luminosity function, while IC 1613 is more ‘SMC-like’. Using the values for the median absolute J magnitude for the LMC and SMC found in Paper I we find a distance modulus of μ0 = 23.54 ± 0.03 (stat) for NGC 6822 and μ0 = 24.34 ± 0.05 (stat) for IC 1613.

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