Updates on the Ultraviolet Emission from Asymptotic Giant Branch Stars

2018 ◽  
Vol 14 (S343) ◽  
pp. 474-475
Author(s):  
Rodolfo Montez ◽  
Sofia Ramstedt ◽  
Joel H. Kastner ◽  
Wouter Vlemmings
Keyword(s):  
Galaxy Evolution ◽  
Initial Study ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Ultraviolet Emission ◽  
Uv Emission ◽  
The Galaxy ◽  
Chromospheric Emission ◽  
Giant Branch Stars

AbstractA comprehensive study of UV emission from asymptotic giant branch (AGB) stars with the Galaxy Evolution Explorer (GALEX) revealed that out of the 316 observed AGB stars, 57% were detected in the near-UV (NUV) bandpass and 12% were detected in the far-UV (FUV) bandpass (Montez et al. 2017). A cross-match between our sample and Gaia DR2 results in parallax estimates for 90% of the sample of AGB stars, compared to only 30% from Hipparcos. This increase allowed us to further probe trends and conclusions of our initial study. Specifically, that the detection of UV emission from AGB stars is subject to proximity and favorable lines of sight in our Galaxy. These improved results support the notion that some of the GALEX-detected UV emission is intrinsic to AGB stars, likely due to a combination of photospheric and chromospheric emission.

scholarly journals AGB Stars and the Observed Abundance of Neon in Planetary Nebulae

2003 ◽  
Vol 20 (4) ◽  
pp. 393-400 ◽  
Author(s):  
A. I. Karakas ◽  
J. C. Lattanzio
Keyword(s):  
Narrow Range ◽  
Planetary Nebulae ◽  
Large Magellanic Cloud ◽  
Stellar Mass ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
The Galaxy ◽  
Tight Correlation ◽  
Giant Branch Stars

AbstractAsymptotic giant branch stars are expected to produce 22Ne through the combined H and He burning that operates during their thermally pulsing evolution. However, observationally there is a fairly tight correlation between the O and Ne abundances as measured in planetary nebulae in various populations. In this paper we use recent detailed stellar evolutionary calculations for compositions appropriate to the Galaxy and the Large Magellanic Cloud, in an attempt to determine if the models are consistent with the observed abundances. We show that there is only a narrow range in stellar mass, about 2 to 4 M⊙ (lower for lower [Fe/H]) where 22Ne is produced in sufficient quantities to affect the total observed elemental neon abundance, which is mostly 20Ne. The models appear to be consistent with the observations, but a more thorough analysis is required.

Dust Structure Around Asymptotic Giant Branch Stars

2018 ◽  
Vol 14 (S343) ◽  
pp. 525-526 ◽  
Author(s):  
Devendra Raj Upadhyay ◽  
Lochan Khanal ◽  
Priyanka Hamal ◽  
Binil Aryal
Keyword(s):  
Inclination Angle ◽  
Asymptotic Giant Branch ◽  
Color Temperature ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Physical Conditions ◽  
The Core ◽  
Cavity Structure ◽  
Temperature Ranges ◽  
Giant Branch Stars

AbstractThis paper presents mass, temperature profile, and the variation of Planck’s function in different regions around asymptotic giant branch (AGB) stars. The physics of the interstellar medium (ISM) is extremely complex because the medium is very inhomogeneous and is made of regions with fairly diverse physical conditions. We studied the dust environment such as flux, temperature, mass, and inclination angle of the cavity structure around C-rich asymptotic giant branch stars in 60 μm and 100 μm wavelengths band using Infrared Astronomical Survey. We observed the data of AGB stars named IRAS 01142+6306 and IRAS 04369+4501. Flexible image transport system image was downloaded from Sky View Observatory; we obtained the surrounding flux density using software Aladin v2.5. The average dust color temperature and mass are found to be 25.08 K, 23.20 K and 4.73 × ;1026 kg (0.00024 M⊙), 2.58 × 1028 kg (0.013 M⊙), respectively. The dust color temperature ranges from 18.76 K ± 3.16 K to 33.21K ± K and 22.84 K ± 0.18 K to 24.48 K ± 0.63 K. The isolated cavity like structure around the AGB stars has an extension of 45.67 pc × 17.02 pc and 42.25 pc × 17.76 pc, respectively. The core region is found to be edge-on having an inclination angle of 79.46° and 73.99°, respectively.

scholarly journals Asymptotic Giant Branch Stars: Thermal Pulses, Carbon Production, and Dredge Up; Neutron Sources and s-Process Nucleosynthesis

1991 ◽  
Vol 145 ◽  
pp. 257-274
Author(s):  
Icko Iben
Keyword(s):  
Neutron Source ◽  
Lower Boundary ◽  
Source Model ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Core Mass ◽  
Convective Envelope ◽  
Thermal Pulses ◽  
Giant Branch Stars

A brief review is given of the structure of asymptotic giant branch (AGB) stars and of the characteristics of the thermal pulses which these stars experience. Following a pulse, model AGB stars with a large core mass easily dredge up fresh carbon, which is the main product of incomplete helium burning, and s-process isotopes, which are made as a consequence of the activation of the 22Ne neutron source. Model AGB stars of small core mass activate the 13C neutron source and produce s-process isotopes in nearly the solar system distribution. They also dredge up fresh carbon and s-process isotopes, but only if overshoot or some other form of “extra” mixing beyond the lower boundary of the convective envelope is invoked.

scholarly journals Obscured Asymptotic Giant Branch stars in the Magellanic Clouds

1999 ◽  
Vol 191 ◽  
pp. 567-572 ◽  
Author(s):  
Jacco Th. van Loon
Keyword(s):  
Magellanic Clouds ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Recent Advances ◽  
Giant Branch Stars

We report on some recent advances in the study and understanding of heavily obscured AGB stars in the Magellanic Clouds.

scholarly journals EVOLUTION OF THERMALLY PULSING ASYMPTOTIC GIANT BRANCH STARS. V. CONSTRAINING THE MASS LOSS AND LIFETIMES OF INTERMEDIATE-MASS, LOW-METALLICITY AGB STARS

2016 ◽  
Vol 822 (2) ◽  
pp. 73 ◽  
Author(s):  
Philip Rosenfield ◽  
Paola Marigo ◽  
Léo Girardi ◽  
Julianne J. Dalcanton ◽  
Alessandro Bressan ◽  
...  
Keyword(s):  
Mass Loss ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Low Metallicity ◽  
Giant Branch Stars

scholarly journals EVOLUTION OF THERMALLY PULSING ASYMPTOTIC GIANT BRANCH STARS. IV. CONSTRAINING MASS LOSS AND LIFETIMES OF LOW MASS, LOW METALLICITY AGB STARS

2014 ◽  
Vol 790 (1) ◽  
pp. 22 ◽  
Author(s):  
Philip Rosenfield ◽  
Paola Marigo ◽  
Léo Girardi ◽  
Julianne J. Dalcanton ◽  
Alessandro Bressan ◽  
...  
Keyword(s):  
Mass Loss ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Low Metallicity ◽  
Low Mass ◽  
Giant Branch Stars

scholarly journals High Resolution Radio and IR Observations of AGB Stars

2012 ◽  
Vol 8 (S287) ◽  
pp. 245-249
Author(s):  
W. Cotton ◽  
G. Perrin ◽  
R. Millan-Gabet ◽  
O. Delaa ◽  
B. Mennesson
Keyword(s):  
High Resolution ◽  
Molecular Layer ◽  
Asymptotic Giant Branch ◽  
Red Giants ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Near Ir ◽  
The Subject ◽  
Infrared Interferometry ◽  
Giant Branch Stars

AbstractAsymptotic Giant Branch Stars (AGB) are evolved, mass losing red giants with tenuous molecular envelopes which have been the subject of much recent study using infrared and radio interferometers. In oxygen rich stars, radio SiO masers form in the outer regions of the molecular envelopes and are powerful diagnostics of the extent of these envelopes. Spectroscopically resolved infrared interferometry helps constrain the extent of various species in the molecular layer. We made VLBA 7 mm SiO maser, Keck Interferometer near IR and VLTI/MIDI mid IR high resolution observations of the stars U Ari, W Cnc, RX Tau, RT Aql, S Ser and V Mon. This paper presents evidence that the SiO is depleted from the gas phase and speculate that it is frozen onto Al2O3 grains and that radiation pressure on these grains help drive the outflow.

scholarly journals Mass-Losing AGB Stars in the Magellanic Clouds

1993 ◽  
Vol 155 ◽  
pp. 319-319
Author(s):  
Neill Reid
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Planetary Nebula ◽  
Luminosity Function ◽  
Magellanic Clouds ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
The Future ◽  
Giant Branch Stars

Asymptotic giant branch stars are the immediate precursors to the planetary nebula stage of stellar evolution. It is clear that the latter stages of a stars life on the AGB are accompanied by either continuous or episodic mass-loss, with the final convulsion being the ejection of the envelope (the future planetary shell), the gradual exposure of the bare CO core and the rapid horizontal evolution to the blue in the H-R diagram. Thus, the structure of the planetary nebula luminosity function, particularly at the higher luminosities (although this phase is extremely rapid), is intimately tied to the luminosity function of the AGB.

scholarly journals Implications of Including AGB Dust in SPS Models

2015 ◽  
Vol 11 (A29B) ◽  
pp. 169-170
Author(s):  
Alexa Villaume ◽  
Charlie Conroy ◽  
Benjamin Johnson
Keyword(s):  
Galaxy Evolution ◽  
Dust Emission ◽  
Asymptotic Giant Branch ◽  
Circumstellar Dust ◽  
Agb Stars ◽  
Population Synthesis ◽  
Star Forming ◽  
The Galaxy ◽  
Ir Emission ◽  
Ir Light

AbstractThe IR emission from galaxies is a unique window into multiple aspects of galaxy evolution including star-formation rates, the age of galaxies, and galactic-scale dust processes. However, asymptotic giant branch (AGB) stars continue to introduce uncertainty into stellar population synthesis (SPS) models and limit our ability to interpret the IR light of galaxies. Here we focus on incorporating circumstellar dust around AGB stars in SPS models and understanding the extent to which they influence the IR light of galaxies. We find that the significance of the AGB dust contribution depends on the characteristics of the galaxy. For quiescent galaxies and metal-poor star forming galaxies, circumstellar dust emission can have a large effect, whereas for dusty star-forming galaxies the circumstellar emission is dwarfed by emission from dust in the ISM. The models with circumstellar dust also suggest, in agreement with previous work, that IR colors can be a powerful age diagnostic for older stellar systems. Models such as these will be essential for interpreting data that will be provided by JWST and other next generation IR facilities.

scholarly journals Thermally-pulsing asymptotic giant branch stars in the Magellanic Clouds

2008 ◽  
Vol 4 (S256) ◽  
pp. 385-390
Author(s):  
Paola Marigo ◽  
Léo Girardi ◽  
Alessandro Bressan ◽  
Martin A. T. Groenewegen ◽  
Bernhard Aringer ◽  
...  
Keyword(s):  
Magellanic Clouds ◽  
Asymptotic Giant Branch ◽  
Circumstellar Dust ◽  
Stellar Winds ◽  
Asymptotic Giant Branch Stars ◽  
Stellar Clusters ◽  
Agb Stars ◽  
Wide Range ◽  
Giant Branch Stars ◽  
Theoretical Project

AbstractWe present the latest results of a theoretical project aimed at investigating the properties of thermally-pulsing asymptotic giant branch (TP-AGB) stars in different host systems. For this purpose, we have recently calculated calibrated synthetic TP-AGB tracks — covering a wide range of metallicities (0.0001 ≤ Z ≤ 0.03) up to the complete ejection of the envelope by stellar winds (Marigo & Girardi 2007) — and used them to generate new sets of stellar isochrones (Marigo et al. 2008). The latter are converted to about 25 different photometric systems, including the mid-infrared filters of Spitzer and AKARI as the effect of circumstellar dust from AGB stars is taken into account. First comparisons with AGB data in the MC field and stellar clusters are discussed.

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