scholarly journals Local environments of SNe Ic and Ic-BL

2015 ◽  
Vol 11 (A29B) ◽  
pp. 278-279
Author(s):  
Jonatan Selsing ◽  
Lise Christensen ◽  
Christina Thöne ◽  
Maryam Modjaz
Keyword(s):  
Mass Loss ◽  
Stellar Populations ◽  
Initial Mass ◽  
Stellar Winds ◽  
Sample Type ◽  
Companion Star ◽  
Physical Conditions ◽  
Local Environments ◽  
Local Explosion ◽  
Dependent Mass

AbstractWe have observed the local explosion environments of a sample Type Ic and Type Ic-BL Supernove (SNe) selected from both targeted and non-targeted surveys using VLT/VIMOS in IFU-mode. It is believed that by probing the local surroundings of the parent stellar populations of these types of SNe, valuable information can be gained about the physical conditions, which affect the type of SNe produced. The different kinds of SNe produced are determined by the initial mass and metallicity of the stellar progenitor, as well as by the metallicity-dependent mass loss in the stellar winds at the end phase of their evolution and the interaction with a sufficiently close companion star.

scholarly journals An ultraviolet view of stellar winds

1979 ◽  
Vol 83 ◽  
pp. 63-80
Author(s):  
Theodore P. Snow
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Stellar Winds ◽  
Physical Conditions ◽  
The Past ◽  
Theoretical Predictions ◽  
Time Variations ◽  
Types Of Information ◽  
Ultraviolet Observations

Ultraviolet observations of mass-loss effects in O stars have, over the past decade, revealed a broad picture of a phenomenon whose extent was only partially evident from earlier ground-based observations. Ultraviolet resonance lines of a variety of ionization stages of several common elements provide a comprehensive probe of the low-density, extended winds. Three general types of information have been derived from ultraviolet spectroscopy of mass-loss profiles: (1) the nature of the stars which experience mass loss via radiatively-driven winds; (2) the physical conditions in the winds; and (3) variability in the outflow, which in turn may yield clues to the origins of the winds. Observations and results in each of these areas are reviewed, and some new results are included. A good correlation of mass loss rate and luminosity is indicated by the data, in agreement with theoretical predictions. Time variations in the P Cygni profiles may be quite common, with variability on times of hours or longer. Anticipated new observations, which should be possible with existing and planned instrumentation, are described.

scholarly journals The mass-loss before the end: two luminous blue variables with a collimated stellar wind

2016 ◽  
Vol 12 (S329) ◽  
pp. 69-73
Author(s):  
C. Agliozzo ◽  
C. Trigilio ◽  
C. Buemi ◽  
P. Leto ◽  
G. Umana ◽  
...  
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Stellar Winds ◽  
Companion Star ◽  
Luminous Blue Variables ◽  
Fast Rotation ◽  
Complex Mass

AbstractWe gathered a multiwavelength dataset of two well-known LBVs. We found a complex mass-loss, with evidence of variability, such as has been seen previously. In addition, our data reveal signatures of collimated stellar winds. We propose a new scenario for these two stars where the nebula shaping is influenced by the presence of a companion star and/or fast rotation.

scholarly journals New models for the rapid evolution of the central star of the Stingray Nebula

2021 ◽  
Author(s):  
T M Lawlor
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Planetary Nebula ◽  
Rapid Evolution ◽  
Central Star ◽  
Asymptotic Giant Branch ◽  
Initial Mass ◽  
Thermal Pulse ◽  
The Past ◽  
New Models

Abstract We present stellar evolution calculations from the Asymptotic Giant Branch (AGB) to the Planetary Nebula (PN) phase for models of initial mass 1.2 M⊙ and 2.0 M⊙ that experience a Late Thermal Pulse (LTP), a helium shell flash that occurs following the AGB and causes a rapid looping evolution between the AGB and PN phase. We use these models to make comparisons to the central star of the Stingray Nebula, V839 Ara (SAO 244567). The central star has been observed to be rapidly evolving (heating) over the last 50 to 60 years and rapidly dimming over the past 20–30 years. It has been reported to belong to the youngest known planetary nebula, now rapidly fading in brightness. In this paper we show that the observed timescales, sudden dimming, and increasing Log(g), can all be explained by LTP models of a specific variety. We provide a possible explanation for the nebular ionization, the 1980’s sudden mass loss episode, the sudden decline in mass loss, and the nebular recombination and fading.

scholarly journals Hot and cold running water: understanding evolved star winds

2017 ◽  
Vol 13 (S336) ◽  
pp. 347-350
Author(s):  
A. M. S. Richards ◽  
M. D. Gray ◽  
A. Baudry ◽  
E. M. L. Humphreys ◽  
S. Etoka ◽  
...  
Keyword(s):  
Mass Loss ◽  
Circumstellar Envelope ◽  
Number Density ◽  
Running Water ◽  
Physical Conditions ◽  
Evolved Stars ◽  
Order Of Magnitude ◽  
Homogeneous Regions ◽  
Maser Sources

AbstractOutstanding problems concerning mass-loss from evolved stars include initial wind acceleration and what determines the clumping scale. Reconstructing physical conditions from maser data has been highly uncertain due to the exponential amplification. ALMA and e-MERLIN now provide image cubes for five H2O maser transitions around VY CMa, at spatial resolutions comparable to the size of individual clouds or better, covering excitation states from 204 to 2360 K. We use the model of Gray et al. 2016, to constrain variations of number density and temperature on scales of a few au, an order of magnitude finer than is possible with thermal lines, comparable to individual cloud sizes or locally almost homogeneous regions. We compare results with the models of Decin et al. 2006 and Matsuura et al. 2014 for the circumstellar envelope of VY CMa; in later work this will be extended to other maser sources.

scholarly journals Stellar Populations and Mass Loss in M15: ASpitzer Space TelescopeDetection of Dust in the Intracluster Medium

2006 ◽  
Vol 132 (4) ◽  
pp. 1415-1425 ◽  
Author(s):  
Martha L. Boyer ◽  
Charles E. Woodward ◽  
Jacco Th. van Loon ◽  
Karl D. Gordon ◽  
A. Evans ◽  
...  
Keyword(s):  
Mass Loss ◽  
Stellar Populations ◽  
Intracluster Medium

scholarly journals What Do We Really Know About the Winds of Massive Stars?

2007 ◽  
Vol 3 (S250) ◽  
pp. 89-96
Author(s):  
D. John Hillier
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Standard Theory ◽  
Stellar Winds ◽  
X Rays ◽  
X Ray ◽  
Stellar Photosphere ◽  
Weak Winds ◽  
Ionization Balance ◽  
Loss Rates

AbstractThe standard theory of radiation driven winds has provided a useful framework to understand stellar winds arising from massive stars (O stars, Wolf-Rayet stars, and luminous blue variables). However, with new diagnostics, and advances in spectral modeling, deficiencies in our understanding of stellar winds have been thrust to the forefront of our research efforts. Spectroscopic observations and analyses have shown the importance of inhomogeneities in stellar winds, and revealed that there are fundamental discrepancies between predicted and theoretical mass-loss rates. For late O stars, spectroscopic analyses derive mass-loss rates significantly lower than predicted. For all O stars, observed X-ray fluxes are difficult to reproduce using standard shock theory, while observed X-ray profiles indicate lower mass-loss rates, the potential importance of porosity effects, and an origin surprisingly close to the stellar photosphere. In O stars with weak winds, X-rays play a crucial role in determining the ionization balance, and must be taken into account.

scholarly journals Clumps in stellar winds

2014 ◽  
Vol 1 ◽  
pp. 39-41 ◽  
Author(s):  
J. S. Vink
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Stellar Winds ◽  
Present Evidence ◽  
Close Proximity ◽  
Stellar Photosphere ◽  
Loss Rates

Abstract. We discuss the origin and quantification of wind clumping and mass–loss rates (Ṁ), particularly in close proximity to the Eddington (Γ) limit, relevant for very massive stars (VMS). We present evidence that clumping may not be the result of the line-deshadowing instability (LDI), but that clumps are already present in the stellar photosphere.

scholarly journals Chandra Study of the Cepheus B Star‐forming Region: Stellar Populations and the Initial Mass Function

2006 ◽  
Vol 163 (2) ◽  
pp. 306-334 ◽  
Author(s):  
Konstantin V. Getman ◽  
Eric D. Feigelson ◽  
Leisa Townsley ◽  
Patrick Broos ◽  
Gordon Garmire ◽  
...  
Keyword(s):  
Stellar Populations ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Star Forming

scholarly journals Synthetic spectra of young starbursts: exploring the metallicity dependence

1999 ◽  
Vol 193 ◽  
pp. 485-486
Author(s):  
A. de Koter ◽  
S.R. Heap ◽  
D.J. Hillier ◽  
D. I. Hubeny
Keyword(s):  
Uv Spectra ◽  
Initial Mass ◽  
Stellar Winds ◽  
Synthetic Spectra ◽  
First Results

We present first results of fully synthetic UV spectra of young starbursts. With this we mean that the spectra used to model the OB and WN stars result from unified non-LTE model atmospheres, in which stellar winds are accounted for. An important aim of this project is to construct meaningful models for young starbursts at low metallicities. We discuss the presence of He II emission as a function of maximum initial mass and age of the burst.

The final 105 years of stellar AGB evolution in the presence of a pulsating, dust-induced “superwind”

1999 ◽  
Vol 191 ◽  
pp. 389-394
Author(s):  
K.-P. Schröder ◽  
J.M. Winters ◽  
E. Sedlmayr
Keyword(s):  
Radiative Transfer ◽  
Mass Loss ◽  
Stellar Evolution ◽  
Mass Range ◽  
Initial Mass ◽  
Temperature Sensitive ◽  
Dust Formation ◽  
Time Step ◽  
Thermal Pulse ◽  
Loss Rates

We have computed mass-loss histories and tip-AGB stellar evolution models in the presence of a dust-induced, carbon-rich “superwind”, in the initial mass-range of 1.1 to about 2.5 solar masses and for nearly solar composition (X=0.28, Y=0.70, Z=0.02). Consistent, actual mass-loss rates are used in each time-step, based on pulsating and “dust-driven” stellar wind models for carbon-rich stars (Fleischer et al. 1992) which include a detailed treatment of dust-formation, radiative transfer and wind acceleration. Our tip-AGB mass-loss rates reach about 4 · 10−5M⊙yr−1 and become an influencial factor of stellar evolution.Heavy outflows of 0.3 to 0.6 M⊙ within only 2 to 3·104 yrs, exactly as required for PN-formation, occur with tip-AGB models of an initial stellar mass Mi ≳ 1.3M⊙. The mass-loss of our “superwind” varies strongly with effective temperature (Ṁ ∝ T−8eff, see Arndt et al. 1997), reflecting the temperature-sensitive micro-physics and chemistry of dust-formation and radiative transfer on a macroscopic scale. Furthermore, a thermal pulse leads to a very short (100 to 200 yrs) interruption of the “superwind” of these models.For Mi ≲ 1.1M⊙, our evolution models fail to reach the (Eddington-like) critical luminosity Lc required by the radiatively driven wind models, while for the (initial) mass-range in-between, with the tip-AGB luminosity LtAGB near Lc, thermal pulses drive bursts of “superwind”, which could explain the outer shells found with some PN's. In particular, a burst with a duration of only 800 yrs and a mass-loss of about 0.03 M⊙, occurs right after the last AGB thermal pulse of a model with Mi ≈ 1.1M⊙. There is excellent agreement with the thin CO shells found by Olofsson et al. (e.g., 1990, 1998) around some Mira stars.

Sign in / Sign up

Export Citation Format

Share Document