scholarly journals AGB mass loss

2011 ◽  
Vol 7 (S283) ◽  
pp. 71-78
Author(s):  
Lee A. Willson ◽  
Qian Wang
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Central Star ◽  
Constant Mass ◽  
Single Star ◽  
The Core ◽  
Maximum Mass Loss ◽  
Loss Formula ◽  
Remnant Mass

AbstractMass loss on the AGB removes most of the envelope and leaves a compact remnant to become a white dwarf and perhaps first the central star of a planetary nebula. The envelope mass provides an upper limit on the material available to form the PN, and the terminal mass loss rate plus the small remnant mass left on the core determines how much of that would still be available to form the PN after the star has evolved far enough to the blue. Given a mass loss formula based on observations or models, we can find the deathline where −dMstar/dt = (M/L) dL/dt and can find the contours of constant mass loss rate on a plot of M vs. L. From such plots we can derive the mass available for a PN and the lowest mass single star that can produce a PN of a given mass. However, some details important for PN formation remain uncertain, including the maximum mass loss rate achieved and the envelope mass left when AGB mass loss ceases.

scholarly journals Author Correction: Reduction of the maximum mass-loss rate of OH/IR stars due to unnoticed binary interaction

2019 ◽  
Vol 3 (5) ◽  
pp. 462-462
Author(s):  
L. Decin ◽  
W. Homan ◽  
T. Danilovich ◽  
A. de Koter ◽  
D. Engels ◽  
...  
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Binary Interaction ◽  
Maximum Mass ◽  
Ir Stars ◽  
Maximum Mass Loss

scholarly journals On the significance of mass loss for the evolution of massive stars

1981 ◽  
Vol 59 ◽  
pp. 265-270
Author(s):  
L.R. Yungelson ◽  
A.G. Massevitch ◽  
A.V. Tutukov
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Loss Rate ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
Hydrogen Burning ◽  
B Stars ◽  
The Core ◽  
Input Parameters ◽  
Satisfactory Theory

It is shown that mass loss by stellar wind with rates observed in O, B-stars cannot change qualitatively their evolution in the core hydrogen-burning stage. The effects, that are usually attributed to the mass loss, can be explained by other causes: e.g., duplicity or enlarged chemically homogeneous stellar cores.The significance of mass loss by stellar wind for the evolution of massive stars was studied extensively by numerous authors (see e.g. Chiosi et al. (1979) and references therein). However, the problem is unclear as yet. There does not exist any satisfactory theory of mass loss by stars. Therefore one is usually forced to assume that mass loss rate depends on some input parameters.

scholarly journals Chemical content of the circumstellar envelope of the oxygen-rich AGB star R Doradus

2018 ◽  
Vol 609 ◽  
pp. A63 ◽  
Author(s):  
M. Van de Sande ◽  
L. Decin ◽  
R. Lombaert ◽  
T. Khouri ◽  
A. de Koter ◽  
...  
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Central Star ◽  
High Mass ◽  
Circumstellar Envelope ◽  
Gaussian Profile ◽  
Macro Scale ◽  
Abundance Profile ◽  
Envelope Model

Context. The stellar outflows of low- to intermediate-mass stars are characterised by a rich chemistry. Condensation of molecular gas species into dust grains is a key component in a chain of physical processes that leads to the onset of a stellar wind. In order to improve our understanding of the coupling between the micro-scale chemistry and macro-scale dynamics, we need to retrieve the abundance of molecules throughout the outflow. Aims. Our aim is to determine the radial abundance profile of SiO and HCN throughout the stellar outflow of R Dor, an oxygen-rich AGB star with a low mass-loss rate. SiO is thought to play an essential role in the dust-formation process of oxygen-rich AGB stars. The presence of HCN in an oxygen-rich environment is thought to be due to non-equilibrium chemistry in the inner wind. Methods. We analysed molecular transitions of CO, SiO, and HCN measured with the APEX telescope and all three instruments on the Herschel Space Observatory, together with data available in the literature. Photometric data and the infrared spectrum measured by ISO-SWS were used to constrain the dust component of the outflow. Using both continuum and line radiative transfer methods, a physical envelope model of both gas and dust was established. We performed an analysis of the SiO and HCN molecular transitions in order to calculate their abundances. Results. We have obtained an envelope model that describes the dust and the gas in the outflow, and determined the abundance of SiO and HCN throughout the region of the stellar outflow probed by our molecular data. For SiO, we find that the initial abundance lies between 5.5 × 10-5 and 6.0 × 10-5 with respect to H2. The abundance profile is constant up to 60 ± 10 R∗, after which it declines following a Gaussian profile with an e-folding radius of 3.5 ± 0.5 × 1013 cm or 1.4 ± 0.2 R∗. For HCN, we find an initial abundance of 5.0 × 10-7 with respect to H2. The Gaussian profile that describes the decline starts at the stellar surface and has an e-folding radius re of 1.85 ± 0.05 × 1015 cm or 74 ± 2 R∗. Conclusions. We cannot unambiguously identify the mechanism by which SiO is destroyed at 60 ± 10 R∗. The initial abundances found are higher than previously determined (except for one previous study on SiO), which might be due to the inclusion of higher-J transitions. The difference in abundance for SiO and HCN compared to high mass-loss rate Mira star IK Tau might be due to different pulsation characteristics of the central star and/or a difference in dust condensation physics.

scholarly journals Stellar Pulsation: (I) Analysis of Stability of Envelope

1993 ◽  
Vol 134 ◽  
pp. 167-168
Author(s):  
Yu Zhi-Yao
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Life Time ◽  
Circumstellar Envelope ◽  
Constant Mass ◽  
Mira Variable ◽  
Stellar Pulsation ◽  
Analysis Of Stability

AbstractThe life-time of the star on AGB is approximately 6 × 104 yr. We divide it into front half and back half of AGB (including to optical Mira variable and OH/IR star) according to their evolution character. The observations show that the star has non-pulsation, but constant mass loss rate (~ 5 × 10−7M⊙ yr−1) on front half of AGB. Its circumstellar envelope is formed. When the star has pulsation on back half of AGB, its mass loss rate is relative with time, and increases gradually. In this time the star is on the stage of optical Mira variable. When the mass loss rate reaches the value of ~ 3 × 10−6M⊙ yr−1, the star evoluted from the stage of optical variable into the stage of radio bright OH/IR star. On the end of AGB the mass loss rate reaches ~10−4M⊙ yr−1. (Band and Habing 1983, Hermen and Habing 1985).

scholarly journals Formation of a planetary nebula by continuous mass loss

1981 ◽  
Vol 59 ◽  
pp. 345-346
Author(s):  
A. Harpaz ◽  
A. Kovetz
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Central Star ◽  
Red Giants ◽  
Giant Star ◽  
Continuous Mass ◽  
Red Giant ◽  
Significant Mass Loss ◽  
Significant Mass

The evolution of a 1.2Mʘ star along the asymptotic branch with continuous mass loss is presented, showing that this mass loss leads to the formation of a PN with a typical central star in its center.A former investigation (Harpaz and Kovetz, 1980) has shown that mechanisms for PN creation based on sudden violent processes are not likely to work in the envelope of a red giant star. On the other hand, significant mass loss from red giants was observed as a general phenomenon.We have followed the evolution of a 1.2Mʘ star along the asymptotic branch, including in the evolutionary calculations a mass loss according to Reimers’ empirical formula. It was found that towards the end of this stage, the mass loss rate was about 2.7xl0-6Mʘ/y, which is consistent with the formation of a typical PN within 30,000 years. When the mass content of the hydrogen rich envelope dropped to 1.5x10-3Mʘ, the star began to contract rapidly, forming a typical central star of 0.6Mʘ

scholarly journals Evolution of 1–5 Mm⊙ Stars by Mass Loss

1993 ◽  
Vol 155 ◽  
pp. 478-478
Author(s):  
E. Vassiliadis ◽  
P.R. Wood
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Main Sequence ◽  
Mass Loss Rate ◽  
Star Clusters ◽  
Magellanic Clouds ◽  
Pulsation Period ◽  
Agb Stars ◽  
Loss Formula ◽  
Loss Rates

Stars of mass 1–5 MM⊙ and composition Y=0.25 and Z=0.016 have been evolved from the main-sequence to the white dwarf stage with an empirical mass loss formula based on observations of mass loss rates in AGB stars. This mass loss formula (Wood 1990) causes the mass loss rate to rise exponentially with pulsation period on the AGB until superwind rates are achieved, where these rates correspond to radiation pressure driven mass loss rates. The formula was designed to reproduce the maximum periods observed for optically-visible LPVs and it also reproduces extremely well the maximum AGB luminosities observed in star clusters in the Magellanic Clouds (see Vassiliadis and Wood 1992 for details).

scholarly journals The estimate of hot Jupiter mass loss rate in the interaction with CME from a solar type star

2015 ◽  
Vol 11 (S320) ◽  
pp. 224-229
Author(s):  
Dmitry V. Bisikalo ◽  
Alexander A. Cherenkov ◽  
Pavel V. Kaygorodov
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Type Star ◽  
Dynamic Simulations ◽  
Solar Type ◽  
Mass Ejection ◽  
Maximum Mass Loss ◽  
Solar Type Star ◽  
Hot Jupiter

AbstractWe consider the influence of a coronal mass ejection (CME) of a solar type star on the mass loss rate of a hot Jupiter exoplanet. We have conducted 3D numerical gas-dynamic simulations of the planet's atmosphere that interacts with CME. Using the results of these simulations we have estimated the specific parameters that influence the mass loss rate. Based on the assumption that CME totally sweeps away part of the planet's gaseous envelope located outside the Roche lobe we estimated the maximum mass loss rate. Finally, we have considered the dependence of mass loss rate on the frequency of CMEs in course of star's evolution.

scholarly journals Radiation driven winds from CV accretion disks

1997 ◽  
Vol 163 ◽  
pp. 782-782 ◽  
Author(s):  
Daniel Proga ◽  
Janet E. Drew ◽  
James M. Stone
Keyword(s):  
Mass Loss ◽  
Radiation Field ◽  
Surface Brightness ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Cataclysmic Variables ◽  
Central Star ◽  
Disk Structure ◽  
Two Parameters ◽  
Initial Results

AbstractWe present some initial results of our numerical, 2D hydrodynamical models of line driven flows from the accretion disk in cataclysmic variables. We assume the disk radiation pressure pushes out the isothermal material from a flat, geometrically thin, Keplerian disk.We calculate the disk radiation field using the surface brightness of a standard “α disk” (Shakura & Sunyaev 1973). We do not include a bright boundary layer in the calculations. We approximate the total radiative line acceleration, adopting the formalism due to Castor, Abbott, & Klein (1975). We use our generalized 2D version of their force multiplier. The multiplier is still described by two parameters representing the number of lines and the ratio of optically thin to optically thick lines. The main modification of the original CAK force multiplier is in the depth parameter, which is now a function of the gradients of two velocity components instead of the single velocity gradient as in the ID case.We investigate how the disk structure and mass loss rate depend on the disk and central star luminosity, and boundary conditions such as the disk density.We find that transonic flows from disks do not relax toward steady states. However, their time averaged properties become constant after some time. Our models show that most of mass loss originates from close to the central star – a few stellar radii. Models without a central star radiation field produce flows more vertical than models in which one is present. However, other global, time averaged properties of flows such as the total wind mass, the wind mass loss rate, and velocity are similar. The ratio between the wind mass loss and disk accretion rate increases rapidly with the accrection rate.

Experimental investigation of fire propagation in single live shrubs

2017 ◽  
Vol 26 (1) ◽  
pp. 58 ◽  
Author(s):  
Jing Li ◽  
Shankar Mahalingam ◽  
David R. Weise
Keyword(s):  
Wind Speed ◽  
Mass Loss ◽  
Bulk Density ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Flame Height ◽  
Maximum Mass ◽  
Gas Temperature ◽  
Fire Behaviour ◽  
Maximum Mass Loss

This work focuses broadly on individual, live shrubs and, more specifically, it examines bulk density in chaparral and its combined effects with wind and ignition location on the resulting fire behaviour. Empirical functions to predict bulk density as a function of height for 4-year-old chaparral were developed for two typical species of shrub fuels in southern California, USA, namely chamise (Adenostoma fasciculatum Hook & Arn.) and manzanita (Arctostaphylos spp. Adans.). Fuel beds of chamise foliage and small-diameter branches were burned in an open-topped wind tunnel. Three levels of bulk density, two ignition locations and two wind speeds were examined, focusing on overall fire behaviour. Mean maximum mass loss rate, elapsed time at which maximum mass loss rate occurred, flame height, flame angle, peak gas temperature and its peak change rate were measured. The mean maximum mass loss rate was not significantly affected by wind speed, ignition location, bulk density or moisture content. Both wind speed and ignition location significantly affected the time that maximum mass loss rate occurred. Only wind speed affected flame height and flame angle. The peak gas temperature within the shrub burning area was found to be mostly affected by the bulk density.

scholarly journals Mass loss from central stars of planetary nebulae

1981 ◽  
Vol 59 ◽  
pp. 45-50
Author(s):  
Mario Perinotto ◽  
Piero Benvenuti ◽  
Carla Cacciari
Keyword(s):  
Mass Loss ◽  
Planetary Nebula ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Planetary Nebulae ◽  
Central Star ◽  
High Resolution Spectrum ◽  
Preliminary Evaluation ◽  
Associated Mass ◽  
Central Stars

AbstractFrom a high resolution spectrum taken with IUE, the central star of the planetary nebula IC 2149 is found to exibit a wind with edge velocity of 1440 ± 100 km s-1. Our preliminary evaluation of the associated mass loss rate gives 10-8 M0 yr-1. Other planetary nebulae nuclei are studied with low resolution IUE spectra and indications are found of mass loss rates consistent with the above value.

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