scholarly journals Post-AGB Discs from Common-Envelope Evolution

Galaxies ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 97 ◽  
Author(s):  
Robert Izzard ◽  
Adam Jermyn
Keyword(s):  
Stellar Population ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Population Synthesis ◽  
Common Envelope ◽  
Disc Model ◽  
Type Interaction ◽  
Orbital Periods ◽  
The Impact ◽  
Disc Formation

Post-asymptotic giant branch (post-AGB) stars with discs are all binaries. Many of these binaries have orbital periods between 100 and 1000 days so cannot have avoided mass transfer between the AGB star and its companion, likely through a common-envelope type interaction. We report on preliminary results of our project to model circumbinary discs around post-AGB stars using our binary population synthesis code binary_c. We combine a simple analytic thin-disc model with binary stellar evolution to estimate the impact of the disc on the binary, and vice versa, fast enough that we can model stellar population and hence explore the rather uncertain parameter space involved with disc formation. We find that, provided the discs form with sufficient mass and angular momentum, and have an inner edge that is relatively close to the binary, they can both prolong the life of their parent post-AGB star and pump the eccentricity of orbits of their inner binaries.

scholarly journals Direct constraints on the impact of TP-AGB stars on the SED of galaxies from near-infrared spectroscopy

2011 ◽  
Vol 7 (S284) ◽  
pp. 63-65 ◽  
Author(s):  
Stefano Zibetti ◽  
Anna Gallazzi ◽  
Stéphane Charlot ◽  
Anna Pasquali ◽  
Daniele Pierini
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Spectral Region ◽  
Stellar Population ◽  
Near Infrared ◽  
Agb Stars ◽  
Population Synthesis ◽  
Stellar Population Synthesis ◽  
Evolutionary Phase ◽  
The Impact

AbstractWe present new spectro-photometric NIR observations of 16 post-starburst galaxies especially designed to test for the presence of strong carbon features of thermally pulsing AGB (TP-AGB) stars, as predicted by recent models of stellar population synthesis. Selection based on clear spectroscopic optical features indicating the strong predominance of stellar populations with ages between 0.5 and 1.5 Gyr and redshift around 0.2 allows us to probe the spectral region that is most affected by the carbon features of TP-AGB stars (unaccessible from the ground for z ~ 0 galaxies) in the evolutionary phase when their impact on the IR luminosity is maximum. Nevertheless, none of the observed galaxies display such features. Moreover the NIR fluxes relative to optical are consistent with those predicted by the original Bruzual & Charlot (2003) models, where the impact of TP-AGB stars is much lower than has been recently advocated.

scholarly journals A new method to identify subclasses among AGB stars using Gaia and 2MASS photometry

2018 ◽  
Vol 616 ◽  
pp. L13 ◽  
Author(s):  
T. Lebzelter ◽  
N. Mowlavi ◽  
P. Marigo ◽  
G. Pastorelli ◽  
M. Trabucchi ◽  
...  
Keyword(s):  
Stellar Population ◽  
Chemical Properties ◽  
Large Magellanic Cloud ◽  
Asymptotic Giant Branch ◽  
Red Giants ◽  
Agb Stars ◽  
Population Synthesis ◽  
Stellar Population Synthesis ◽  
Low Mass ◽  
Spectral Ranges

Aims. We explore the wealth of high-quality photometric data provided by data release 2 (DR2) of the Gaia mission for long-period variables (LPVs) in the Large Magellanic Cloud (LMC). Our goal is to identify stars of various types and masses along the asymptotic giant branch. Methods. For this endeavour, we developed a new multi-band approach combining Wesenheit functions WRP,BP−RP and WKs,J−Ks in the Gaia BP, RP, and 2MASS J, Ks spectral ranges, respectively, and use a new diagram, (WRP,BP−RP − WKs,J−Ks) versus Ks, to distinguish between different kinds of stars in our sample of LPVs. We used stellar population synthesis models to validate our approach. Results. We demonstrate the ability of the new diagram to discriminate between O- and C-rich objects, and to identify low-mass, intermediate-mass, and massive O-rich red giants, as well as extreme C-rich stars. Stellar evolution and population synthesis models guide the interpretation of the results, highlighting the diagnostic power of the new tool to discriminate between stellar initial masses, chemical properties, and evolutionary stages.

Calibrating TP-AGB stellar models and chemical yields through resolved stellar populations in the Small Magellanic Cloud

2018 ◽  
Vol 14 (S343) ◽  
pp. 269-272
Author(s):  
Giada Pastorelli ◽  
Paola Marigo ◽  
Léo Girardi ◽  
Keyword(s):  
Mass Loss ◽  
Magellanic Cloud ◽  
Star Formation History ◽  
Agb Stars ◽  
Population Synthesis ◽  
Small Magellanic Cloud ◽  
Luminosity Functions ◽  
Formation History ◽  
Best Fitting ◽  
The Impact

AbstractMost of the physical processes driving the TP-AGB evolution are not yet fully understood and they need to be modelled with parameterised descriptions. We present the results of the on-going calibration of the TP-AGB phase based on a complete sample of AGB stars in the Small Magellanic Cloud (SAGE-SMC survey). We computed large grids of TP-AGB models with several combinations of third dredge-up and mass-loss prescriptions with the COLIBRI code. The SMC AGB population is modelled with the population synthesis code TRILEGAL according to the space-resolved star formation history derived with the deep photometry from the VISTA survey of the Magellanic Clouds. We put quantitative constraints on the efficiencies of the third dredge-up and mass loss by requiring the models to reproduce the star counts and the luminosity functions of the observed Oxygen-, Carbon-rich and extreme-AGB stars and we investigate the impact of the best-fitting prescriptions on the chemical yields.

scholarly journals Tracers of Star Formation in the Near Infrared

2009 ◽  
Vol 5 (S262) ◽  
pp. 383-384
Author(s):  
L. Martins ◽  
A. Ardila ◽  
R. Gruenwald ◽  
R. de Souza
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Near Infrared ◽  
Agb Stars ◽  
Population Synthesis ◽  
Near Ir ◽  
Stellar Population Synthesis ◽  
First Time ◽  
Absorption Features ◽  
Empirical Database

AbstractStarburst features in the optical are nowadays well known, but the use of this knowledge is not always possible (e.g. objects heavily obscured). In this case the near-IR is of unprecedented value. Recent models show that TP-AGB stars should dominate the NIR spectra of populations 0.3 to 2 Gyr old. While the optical spectra is insensitive to the presence of these stars, the near-IR changes dramatically. Not only does the absolute flux in the near-IR is affected, but also peculiar absorption features appear. These features can be used as indicators of 1 Gyr stellar population. In this work we used the IRTF Spex to create the first empirical database of NIR spectra of carefully selected starbursts, to test for the first time and in a consistent way the new stellar population models that account for the TP-AGB. The methodology used is to do stellar population synthesis in the optical and in the NIR, and compare the predictions of both spectral regions. We also compare the strength of important features of the TP-AGB stars, like the CN (1.1 microns) and CO (2.3 microns) bands with optical diagnostics.

scholarly journals TP-AGB stars in population synthesis models

2009 ◽  
Vol 5 (S262) ◽  
pp. 36-43 ◽  
Author(s):  
Paola Marigo ◽  
Léo Girardi ◽  
Alessandro Bressan ◽  
Bernhard Aringer ◽  
Marco Gullieuszik ◽  
...  
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Magellanic Clouds ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Population Synthesis ◽  
Future Developments ◽  
First Results ◽  
Nearby Galaxies ◽  
The Subject

AbstractIn spite of its relevance, the Thermally Pulsing Asymptotic Giant Branch (TP-AGB) phase is one of the most uncertain phases of stellar evolution, and a major source of disagreement between the results of different population synthesis models of galaxies. I will briefly review the existing literature on the subject, and recall the basic prescriptions that have been used to fix the contribution of TP-AGB stars to the integrated light of stellar populations. The simplicity of these prescriptions greatly contrasts with the richness of details provided by present-day databases of AGB stars in the Magellanic Clouds, which are now being extended to other nearby galaxies. I will present the first results of an ongoing study aimed at simulating photometry, chemistry, pulsation, mass loss, dust properties of AGB star populations in resolved and un-resolved galaxies. We test our predictions against observations from various surveys of the Magellanic Clouds (DENIS, 2MASS, OGLE, MACHO, Spitzer, and AKARI). I will discuss the implications and outline the plan of future developments.

scholarly journals The impact of close binary evolution on the properties of the WR-bump emission lines of Wolf-Rayet galaxies

2003 ◽  
Vol 212 ◽  
pp. 576-577
Author(s):  
Joris Van Bever ◽  
Dany Vanbeveren
Keyword(s):  
Mass Transfer ◽  
Neutron Stars ◽  
Supernova Explosion ◽  
Emission Lines ◽  
Close Binary ◽  
Population Synthesis ◽  
Common Envelope ◽  
Solar Metallicity ◽  
Binary Evolution ◽  
The Impact

We present the results of a study on the behaviour of the blue and red WR emission bumps (around 4650Å and 5808Å) and of the nebular contribution to He ii λ4686 in evolving young starburst regions (such as Wolf-Rayet galaxies), containing a non-negligible binary population. Calculations were made for solar metallicity and 1/20 solar. The population synthesis program uses an extended library of stellar evolutionary tracks of single stars and binaries, computed using the most recent stellar wind mass loss rates during RSG, LBV and WR stages. In the case of binaries, we account in detail for the effects of Roche lobe overflow, mass transfer and mass accretion, common envelope evolution, the spiral-in process, asymmetric kicks to neutron stars as a result of their supernova explosion, etc. This research is part of a more extensive project to explore every possible impact of massive binaries on stellar populations.

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 The eccentric behaviour of windy binary stars

2019 ◽  
Vol 629 ◽  
pp. A103 ◽  
Author(s):  
M. I. Saladino ◽  
O. R. Pols
Keyword(s):  
Mass Transfer ◽  
Binary Stars ◽  
Numerical Models ◽  
Orbital Evolution ◽  
Small Sample ◽  
Asymptotic Giant Branch ◽  
Tidal Effects ◽  
Orbital Parameters ◽  
Orbital Periods ◽  
The Impact

Carbon-enhanced metal-poor stars, CH stars, barium stars, and extrinsic S stars, among other classes of chemically peculiar stars, are thought to be the products of the interaction of low- and intermediate-mass binaries, which occurred when the most evolved star was in the asymptotic giant branch (AGB) phase. Binary evolution models predict that because of the large sizes of AGB stars, if the initial orbital periods of such systems are shorter than a few thousand days, their orbits should have circularised due to tidal effects. However, observations of the progeny of AGB binary stars show that many of these objects have substantial eccentricities, up to e ≈ 0.9. In this work we explore the impact of wind mass transfer on the orbital parameters of AGB binary stars by performing numerical simulations in which the AGB wind is modelled using a hydrodynamical code and the dynamics of the stars is evolved using an N-body code. We find that in most models the effect of wind mass transfer contributes to the circularisation of the orbit, but on longer timescales than tidal circularisation if e ≲ 0.4. For relatively low initial wind velocities and pseudo-synchronisation of the donor star, we find a structure resembling wind Roche-lobe overflow as the stars approach periastron. In this case, the interaction between the gas and the star is stronger than when the initial wind velocity is high and the orbit shrinks while the eccentricity decreases. In one of our models wind interaction is found to pump the eccentricity of the orbit on a similar timescale as tidal circularisation. However, since the orbit of this model is shrinking tidal effects will become stronger during the evolution of the system. Although our study is based on a small sample of models, it offers some insight into the orbital evolution of eccentric binary stars interacting via winds. A larger grid of numerical models for different binary parameters is needed to test if a regime exists where hydrodynamical eccentricity pumping can effectively counteract tidal circularisation, and if this can explain the puzzling eccentricities of the descendants of AGB binaries.

scholarly journals Spectroscopic binaries RV Tauri and DF Cygni

2019 ◽  
Vol 628 ◽  
pp. A40 ◽  
Author(s):  
Rajeev Manick ◽  
Devika Kamath ◽  
Hans Van Winckel ◽  
Alain Jorissen ◽  
Sanjay Sekaran ◽  
...  
Keyword(s):  
Orbital Period ◽  
Asymptotic Giant Branch ◽  
Spectroscopic Binaries ◽  
Spectral Energy ◽  
Pulsation Frequency ◽  
Photometric Variability ◽  
Orbital Inclination ◽  
Orbital Periods ◽  
The Impact

Context. Some RV Tauri stars show a long-term photometric variability in their mean magnitudes. DF Cygni (DF Cyg), the only RV Tauri star in the original Kepler field, and the prototype RV Tauri (RV Tau) are two such stars. Aims. The focus of this paper is on two famous but still poorly understood RV Tauri stars: RV Tau and DF Cyg. We aim to confirm their suspected binary nature and derive their orbital elements to investigate the impact of their orbits on the evolution of these systems. This research is embedded in a wider endeavour to study binary evolution of low- and intermediate-mass stars. Methods. The high amplitude pulsations were cleaned from the radial-velocity data to better constrain the orbital motion, allowing us to obtain accurate orbital parameters. We also analysed the photometric time series of both stars using a Lomb-Scargle periodogram. We used Gaia Data Release 2 (DR2) parallaxes in combination with the spectral energy distributions (SEDs) to compute their luminosities. These luminosities were complemented with the ones we computed using a period-luminosity-colour (PLC) relation for RV Tauri stars. The ratio of the circumstellar infrared (IR) flux to the photospheric flux obtained from the SEDs was used to estimate the orbital inclination of each system. Results. DF Cyg and RV Tau are binaries with spectroscopic orbital periods of 784 ± 16 days and 1198 ± 17 days, respectively. These orbital periods are found to be similar to the long-term periodic variability in the photometry, indicating that binarity indeed explains the long-term photometric variability. The SEDs of these systems indicate the presence of a circumbinary disc. Our line of sight grazes the dusty disc, which causes the photometric flux from the star to extinct periodically with the orbital period. Our derived orbital inclinations enabled us to obtain accurate companion masses for DF Cyg and RV Tau, and these were found to be 0.6 ± 0.1 M⊙ and 0.7 ± 0.1 M⊙, respectively. The derived luminosities suggest that RV Tau is a post asymptotic giant branch (post-AGB) binary, while DF Cyg is likely a post red giant branch (post-RGB) binary. Analysis of the Kepler photometry of DF Cyg revealed a power spectrum with side lobes around the fundamental pulsation frequency. This modulation corresponds to the spectroscopic orbital period and hence to the long-term photometric period. Finally we report on the evidence of high velocity absorption features related to the Hα profile in both objects, indicating outflows launched from around the companion.

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