scholarly journals (Sub)stellar companions shape the winds of evolved stars

Science ◽  
2020 ◽  
Vol 369 (6510) ◽  
pp. 1497-1500 ◽  
Author(s):  
L. Decin ◽  
M. Montargès ◽  
A. M. S. Richards ◽  
C. A. Gottlieb ◽  
W. Homan ◽  
...  
Keyword(s):  
Planetary Nebula ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Asymptotic Giant Branch ◽  
Binary Interaction ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Evolved Stars ◽  
Intermediate Mass Stars ◽  
Evolutionary Scenario

Binary interactions dominate the evolution of massive stars, but their role is less clear for low- and intermediate-mass stars. The evolution of a spherical wind from an asymptotic giant branch (AGB) star into a nonspherical planetary nebula (PN) could be due to binary interactions. We observed a sample of AGB stars with the Atacama Large Millimeter/submillimeter Array (ALMA) and found that their winds exhibit distinct nonspherical geometries with morphological similarities to planetary nebulae (PNe). We infer that the same physics shapes both AGB winds and PNe; additionally, the morphology and AGB mass-loss rate are correlated. These characteristics can be explained by binary interaction. We propose an evolutionary scenario for AGB morphologies that is consistent with observed phenomena in AGB stars and PNe.

scholarly journals Wind morphology around cool evolved stars in binaries

2020 ◽  
Vol 637 ◽  
pp. A91 ◽  
Author(s):  
I. El Mellah ◽  
J. Bolte ◽  
L. Decin ◽  
W. Homan ◽  
R. Keppens
Keyword(s):  
Mass Loss ◽  
Adaptive Mesh Refinement ◽  
Loss Rate ◽  
Main Sequence ◽  
Mass Loss Rate ◽  
Large Fraction ◽  
Orbital Plane ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Evolved Stars

Context. The late evolutionary phase of low- and intermediate-mass stars is strongly constrained by their mass-loss rate, which is orders of magnitude higher than during the main sequence. The wind surrounding these cool expanded stars frequently shows nonspherical symmetry, which is thought to be due to an unseen companion orbiting the donor star. The imprints left in the outflow carry information about the companion and also the launching mechanism of these dust-driven winds. Aims. We study the morphology of the circumbinary envelope and identify the conditions of formation of a wind-captured disk around the companion. Long-term orbital changes induced by mass loss and mass transfer to the secondary are also investigated. We pay particular attention to oxygen-rich, that is slowly accelerating, outflows in order to look for systematic differences between the dynamics of the wind around carbon and oxygen-rich asymptotic giant branch (AGB) stars. Methods. We present a model based on a parametrized wind acceleration and a reduced number of dimensionless parameters to connect the wind morphology to the properties of the underlying binary system. Thanks to the high performance code MPI-AMRVAC, we ran an extensive set of 72 three-dimensional hydrodynamics simulations of a progressively accelerating wind propagating in the Roche potential of a mass-losing evolved star in orbit with a main sequence companion. The highly adaptive mesh refinement that we used, enabled us to resolve the flow structure both in the immediate vicinity of the secondary, where bow shocks, outflows, and wind-captured disks form, and up to 40 orbital separations, where spiral arms, arcs, and equatorial density enhancements develop. Results. When the companion is deeply engulfed in the wind, the lower terminal wind speeds and more progressive wind acceleration around oxygen-rich AGB stars make them more prone than carbon-rich AGB stars to display more disturbed outflows, a disk-like structure around the companion, and a wind concentrated in the orbital plane. In these configurations, a large fraction of the wind is captured by the companion, which leads to a significant shrinking of the orbit over the mass-loss timescale, if the donor star is at least a few times more massive than its companion. In the other cases, an increase of the orbital separation is to be expected, though at a rate lower than the mass-loss rate of the donor star. Provided the companion has a mass of at least a tenth of the mass of the donor star, it can compress the wind in the orbital plane up to large distances. Conclusions. The grid of models that we computed covers a wide scope of configurations: We vary the terminal wind speed relative to the orbital speed, the extension of the dust condensation region around the cool evolved star relative to the orbital separation, and the mass ratio, and we consider a carbon-rich and an oxygen-rich donor star. It provides a convenient frame of reference to interpret high-resolution maps of the outflows surrounding cool evolved stars.

Variability, Pulsations and Mass Loss of Evolved Stars

2017 ◽  
Vol 14 (S339) ◽  
pp. 95-97
Author(s):  
S. Höfner
Keyword(s):  
Mass Loss ◽  
Chemical Elements ◽  
Building Blocks ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Long Period ◽  
Evolved Stars ◽  
Intermediate Mass Stars ◽  
Recent Developments

AbstractEvolved low- and intermediate-mass stars that have reached the Asymptotic Giant Branch (AGB) phase tend to show pronounced long-period variability due to large-amplitude pulsations. Those pulsations are considered to play a key role in triggering mass loss through massive dusty winds. The winds enrich the surrounding interstellar medium with newly-produced chemical elements and dust grains, providing building blocks for new generations of stars and planets. Considerable efforts are being made to understand the physics of AGB stars, and to develop quantitative models. This talk gave a brief summary of recent developments, with references to the literature.

scholarly journals AGB Winds with Gas-Dust Drift in Stellar Evolution Codes

Universe ◽  
2021 ◽  
Vol 7 (5) ◽  
pp. 113
Author(s):  
Lars Mattsson ◽  
Christer Sandin
Keyword(s):  
Stellar Evolution ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Carbon Star ◽  
Intermediate Mass ◽  
Future Directions ◽  
Physical Description ◽  
Intermediate Mass Stars ◽  
Dust Component ◽  
Improved Model

A significant fraction of new metals produced in stars enter the interstellar medium in the form of dust grains. Including dust and wind formation in stellar evolution models of late-stage low- and intermediate-mass stars provides a way to quantify their contribution to the cosmic dust component. In doing so, a correct physical description of dust formation is of course required, but also a reliable prescription for the mass-loss rate. Here, we present an improved model of dust-driven winds to be used in stellar evolution codes and insights from recent detailed numerical simulations of carbon-star winds including drift (decoupling of dust and gas). We also discuss future directions for further improvement.

scholarly journals Nucleosynthesis of Light-Element Isotopes in Evolved Stars Experiencing Extended Mixing

2009 ◽  
Vol 26 (3) ◽  
pp. 161-167 ◽  
Author(s):  
S. Palmerini ◽  
M. Busso ◽  
E. Maiorca ◽  
R. Guandalini
Keyword(s):  
Mass Transport ◽  
Isotopic Composition ◽  
Light Element ◽  
Asymptotic Giant Branch ◽  
Red Giants ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Evolved Stars ◽  
Magnetic Buoyancy ◽  
Slow Mixing

AbstractWe present computations of nucleosynthesis in red giants and Asymptotic Giant Branch (AGB) stars of Population I experiencing extended mixing. The assumed physical cause for mass transport is the buoyancy of magnetized structures, according to recent suggestions. The peculiar property of such a mechanism is to allow for both fast and slow mixing phenomena, as required for reproducing the spread in Li abundances displayed by red giants and as discussed in an accompanying paper. We explore here the effects of this kind of mass transport on CNO and intermediate-mass nuclei and compare the results with the available evidence from evolved red giants and from the isotopic composition of presolar grains of AGB origin. It is found that a good general accord exists between predictions and measurements; in this framework we also show which type of observational data best constrains the various parameters. We conclude that magnetic buoyancy, allowing for mixing at rather different speeds, can be an interesting scenario to explore for explaining together the abundances of CNO nuclei and of Li.

scholarly journals Warm CO in evolved stars from the THROES catalogue

2019 ◽  
Vol 622 ◽  
pp. A123 ◽  
Author(s):  
J. M. da Silva Santos ◽  
J. Ramos-Medina ◽  
C. Sánchez Contreras ◽  
P. García-Lario
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Asymptotic Giant Branch ◽  
Strong Line ◽  
Order Estimate ◽  
Evolved Stars ◽  
Flux Variability ◽  
The Impact ◽  
Loss Rates

Context. This is the second paper of a series making use of Herschel/PACS spectroscopy of evolved stars in the THROES catalogue to study the inner warm regions of their circumstellar envelopes (CSEs). Aims. We analyse the CO emission spectra, including a large number of high-J CO lines (from J = 14–13 to J = 45–44, ν = 0), as a proxy for the warm molecular gas in the CSEs of a sample of bright carbon-rich stars spanning different evolutionary stages from the asymptotic giant branch to the young planetary nebulae phase. Methods. We used the rotational diagram (RD) technique to derive rotational temperatures (Trot) and masses (MH2) of the envelope layers where the CO transitions observed with PACS arise. Additionally, we obtained a first order estimate of the mass-loss rates and assessed the impact of the opacity correction for a range of envelope characteristic radii. We used multi-epoch spectra for the well-studied C-rich envelope IRC+10216 to investigate the impact of CO flux variability on the values of Trot and MH2. Results. The sensitivity of PACS allowed for the study of higher rotational numbers than before indicating the presence of a significant amount of warmer gas (∼200 − 900 K) that is not traceable with lower J CO observations at submillimetre/millimetre wavelengths. The masses are in the range MH2 ∼ 10−2 − 10−5 M⊙, anticorrelated with temperature. For some strong CO emitters we infer a double temperature (warm T¯rot ∼ 400 K and hot T¯rot ∼ 820 K) component. From the analysis of IRC+10216, we corroborate that the effect of line variability is perceptible on the Trot of the hot component only, and certainly insignificant on MH2 and, hence, the mass-loss rate. The agreement between our mass-loss rates and the literature across the sample is good. Therefore, the parameters derived from the RD are robust even when strong line flux variability occurs, and the major source of uncertainty in the estimate of the mass-loss rate is the size of the CO-emitting volume.

scholarly journals Evolutionary timescales from the AGB to the CSPNe phase

2018 ◽  
Vol 14 (S343) ◽  
pp. 36-46
Author(s):  
Marcelo M. Miller Bertolami
Keyword(s):  
White Dwarf ◽  
New Physics ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Intermediate Mass Stars

AbstractThe transition from the asymptotic giant branch (AGB) to the final white dwarf (WD) stage is arguably the least understood phase in the evolution of single low- and intermediate-mass stars (0.8 ≲ MZAMS/M⊙ ≲ 8…10). Here we briefly review the progress in the last 50 years of the modeling of stars during the post-AGB phase. We show that although the main features, like the extreme mass dependency of post-AGB timescales were already present in the earliest post-AGB models, the quantitative values of the computed post-AGB timescales changed every time new physics was included in the modeling of post-AGB stars and their progenitors. Then we discuss the predictions and uncertainties of the latest available models regarding the evolutionary timescales of post-AGB stars.

scholarly journals Stellar wind models of central stars of planetary nebulae

2020 ◽  
Vol 635 ◽  
pp. A173 ◽  
Author(s):  
J. Krtička ◽  
J. Kubát ◽  
I. Krtičková
Keyword(s):  
Mass Loss ◽  
White Dwarf ◽  
Planetary Nebula ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Planetary Nebulae ◽  
Terminal Velocity ◽  
Asymptotic Giant Branch ◽  
Central Stars ◽  
Loss Rates

Context. Fast line-driven stellar winds play an important role in the evolution of planetary nebulae, even though they are relatively weak. Aims. We provide global (unified) hot star wind models of central stars of planetary nebulae. The models predict wind structure including the mass-loss rates, terminal velocities, and emergent fluxes from basic stellar parameters. Methods. We applied our wind code for parameters corresponding to evolutionary stages between the asymptotic giant branch and white dwarf phases for a star with a final mass of 0.569 M⊙. We study the influence of metallicity and wind inhomogeneities (clumping) on the wind properties. Results. Line-driven winds appear very early after the star leaves the asymptotic giant branch (at the latest for Teff ≈ 10 kK) and fade away at the white dwarf cooling track (below Teff = 105 kK). Their mass-loss rate mostly scales with the stellar luminosity and, consequently, the mass-loss rate only varies slightly during the transition from the red to the blue part of the Hertzsprung–Russell diagram. There are the following two exceptions to the monotonic behavior: a bistability jump at around 20 kK, where the mass-loss rate decreases by a factor of a few (during evolution) due to a change in iron ionization, and an additional maximum at about Teff = 40−50 kK. On the other hand, the terminal velocity increases from about a few hundreds of km s−1 to a few thousands of km s−1 during the transition as a result of stellar radius decrease. The wind terminal velocity also significantly increases at the bistability jump. Derived wind parameters reasonably agree with observations. The effect of clumping is stronger at the hot side of the bistability jump than at the cool side. Conclusions. Derived fits to wind parameters can be used in evolutionary models and in studies of planetary nebula formation. A predicted bistability jump in mass-loss rates can cause the appearance of an additional shell of planetary nebula.

scholarly journals Monash Chemical Yields Project (Monχey) Element production in low- and intermediate-mass stars

2015 ◽  
Vol 11 (A29B) ◽  
pp. 164-165
Author(s):  
Carolyn Doherty ◽  
John Lattanzio ◽  
George Angelou ◽  
Simon W. Campbell ◽  
Ross Church ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Heavy Element ◽  
Internal Surface ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Galactic Chemical Evolution ◽  
Intermediate Mass ◽  
Mixing Processes ◽  
Intermediate Mass Stars ◽  
Solar Metallicity

AbstractThe Monχey project will provide a large and homogeneous set of stellar yields for the low- and intermediate- mass stars and has applications particularly to galactic chemical evolution modelling. We describe our detailed grid of stellar evolutionary models and corresponding nucleosynthetic yields for stars of initial mass 0.8 M⊙ up to the limit for core collapse supernova (CC-SN) ≈ 10 M⊙. Our study covers a broad range of metallicities, ranging from the first, primordial stars (Z = 0) to those of super-solar metallicity (Z = 0.04). The models are evolved from the zero-age main-sequence until the end of the asymptotic giant branch (AGB) and the nucleosynthesis calculations include all elements from H to Bi. A major innovation of our work is the first complete grid of heavy element nucleosynthetic predictions for primordial AGB stars as well as the inclusion of extra-mixing processes (in this case thermohaline) during the red giant branch. We provide a broad overview of our results with implications for galactic chemical evolution as well as highlight interesting results such as heavy element production in dredge-out events of super-AGB stars. We briefly introduce our forthcoming web-based database which provides the evolutionary tracks, structural properties, internal/surface nucleosynthetic compositions and stellar yields. Our web interface includes user- driven plotting capabilities with output available in a range of formats. Our nucleosynthetic results will be available for further use in post processing calculations for dust production yields.

scholarly journals Constraining ν-process production of fluorine through cosmic ray nucleosynthesis

2019 ◽  
Vol 490 (3) ◽  
pp. 4307-4316 ◽  
Author(s):  
Keith A Olive ◽  
Elisabeth Vangioni
Keyword(s):  
Stellar Evolution ◽  
Massive Star ◽  
Cosmic Ray ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Intermediate Mass Stars ◽  
Star Production ◽  
Low Metallicity ◽  
Galactic Cosmic Ray

ABSTRACT Fluorine is massive enough that it is not considered to be a light (Z ≤ 5) element, yet compared to its near neighbours, C, N, O, and Ne, it is far underproduced in the course of stellar evolution, making its origin more complex. In fact, the abundance of fluorine is the lowest among all elements between Z = 5 and 21 and is roughly 3–4 orders of magnitude below that of C, N, O, and Ne. There are several plausible sources for F beyond standard stellar evolution. These include the production in the asymptotic giant branch phase (AGB) in intermediate-mass stars, production in Wolf–Rayet stars, and the production through neutrino spallation in supernovae. The latter, known as the ν-process, is an important source for 11B, and may contribute to the abundance of 7Li as well. We combine a simple model of Galactic chemical evolution with a standard Galactic cosmic ray nucleosynthesis model to treat self-consistently the evolution of the Li, Be, and B isotopes. We include massive star production of F, as well as contributions from AGB stars, and the ν-process. Given the uncertainties in neutrino energies in supernovae, we normalize the ν-process using the observed 11B/10B ratio as a constraint. As a consequence, we are able to determine the relative importance of each contribution to the F abundance. We find that although the ν-process dominates at early times (low metallicity), the present-day F abundance is found to originate primarily from AGB stars.

scholarly journals SMBH Luminosity in the Starburst Environment

2009 ◽  
Vol 5 (S267) ◽  
pp. 336-336
Author(s):  
Sergiy Silich ◽  
Guillermo Tenorio-Tagle ◽  
Filiberto Hueyotl-Zahuantitla ◽  
Jan Palouš ◽  
Richard Wünsch
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Accretion Rate ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
Intermediate Mass ◽  
Star Forming ◽  
Intermediate Mass Stars

We claim that in the starburst environment there is no accretion of the ISM onto the BH and thus, in such cases, the BH luminosity is regulated by the mass-loss rate from massive stars in the star forming region. We calculate the accretion rate and show that it is usually small during the superwind stage and grows at the post-starburst stage, when the matter reinserted by intermediate–mass stars remains gravitationally bound and fuels the central BH.

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