scholarly journals The Circumstellar Structure Around Supernovae

1988 ◽  
Vol 101 ◽  
pp. 15-18
Author(s):  
P. Lundqvist ◽  
C. Fransson
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Time Dependent ◽  
Temperature Structure ◽  
Radio Observations ◽  
Turn On ◽  
Sn 1987A ◽  
Circumstellar Medium

AbstractThe time dependent ionization and temperature structure of the circumstellar medium around supernovae has been calculated, in order to interpret recent supernova radio observations. For a stellar wind origin of the circumstellar medium, we relate the time of radio turn-on to the progenitor mass loss rate. We also show that large column densities for the UV resonance lines are expected. The results are applied to SN 1979c, SN 1980k and SN 1987A.

scholarly journals λ And: a post-main-sequence wind from a solar-mass star

2020 ◽  
Vol 500 (3) ◽  
pp. 3438-3453
Author(s):  
D Ó Fionnagáin ◽  
A A Vidotto ◽  
P Petit ◽  
C Neiner ◽  
W Manchester IV ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Mass Loss ◽  
Stellar Wind ◽  
Loss Rate ◽  
Main Sequence ◽  
Mass Loss Rate ◽  
Mass Star ◽  
Radio Observations ◽  
Solar Mass ◽  
5 Ghz

ABSTRACT We investigate the wind of λ And, a solar-mass star that has evolved off the main sequence becoming a subgiant. We present spectropolarimetric observations and use them to reconstruct the surface magnetic field of λ And. Although much older than our Sun, this star exhibits a stronger (reaching up to 83 G) large-scale magnetic field, which is dominated by the poloidal component. To investigate the wind of λ And, we use the derived magnetic map to simulate two stellar wind scenarios, namely a ‘polytropic wind’ (thermally driven) and an ‘Alfven-wave-driven wind’ with turbulent dissipation. From our 3D magnetohydrodynamics simulations, we calculate the wind thermal emission and compare it to previously published radio observations and more recent Very Large Array observations, which we present here. These observations show a basal sub-mJy quiescent flux level at ∼5 GHz and, at epochs, a much larger flux density (>37 mJy), likely due to radio flares. By comparing our model results with the radio observations of λ And, we can constrain its mass-loss rate $\dot{M}$. There are two possible conclusions. (1) Assuming the quiescent radio emission originates from the stellar wind, we conclude that λ And has $\dot{M} \simeq 3 \times 10^{-9}$ M⊙ yr −1, which agrees with the evolving mass-loss rate trend for evolved solar-mass stars. (2) Alternatively, if the quiescent emission does not originate from the wind, our models can only place an upper limit on mass-loss rates, indicating that $\dot{M} \lesssim 3 \times 10^{-9}$ M⊙ yr −1.

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 Radio observations and the mass flow rate of α Cyg (A2Ia)

1981 ◽  
Vol 59 ◽  
pp. 61-64
Author(s):  
B. Wolf ◽  
O. Stahl ◽  
W.J. Altenhoff
Keyword(s):  
Mass Loss ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
Growth Analysis ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
The Other ◽  
Radio Flux ◽  
Radio Observations ◽  
Lower Mass

From the free-free excess at 10μ. Barlow and Cohen (1977) (hereafter referred to as BC) derived a mass loss rate of 6.9 10-7 M⊙ yr-1 for α Cyg. They predicted a 10 GHz radio flux of 2.2 mJy. On the other hand Praderie et al. (1980) derived a considerable lower mass loss rate of 1.1 10 -8 ≤Ṁ ≤ 7 10-8 M ⊙ yr-1 from a curve of growth analysis of the envelope ultraviolet Fell-lines of α Cyg. Radio observations are desirable to make a decision about these discrepant results. Therefore we observed α Cyg at 15 GHz with the 100 m telescope of the MPIfR at Effelsberg. The observations are discussed together with recent VLA data of Abbott et al. (1980).

Time dependent contribution of char oxidation and flame heat feedback on the mass loss rate of timber

2020 ◽  
pp. 103058
Author(s):  
David Morrisset ◽  
Rory M. Hadden ◽  
Alastair I. Bartlett ◽  
Angus Law ◽  
Richard Emberley
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Time Dependent ◽  
Char Oxidation

scholarly journals Radio Emission from WR Stars

1982 ◽  
Vol 99 ◽  
pp. 221-224 ◽  
Author(s):  
David E. Hogg
Keyword(s):  
Simple Model ◽  
Radio Emission ◽  
Mass Loss ◽  
Flux Density ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Large Array ◽  
Radio Observations ◽  
Very Large Array

In principle radio observations of WR stars offer the best possibility of determining the rate of mass loss, since for a simple model of the extended atmosphere the mass loss rate depends primarily on quantities—the flux density, the velocity, and the distance—which are observable (Barlow 1979). Until now, detections of Wolf-Rayet stars have been limited by the sensitivity and resolution of available telescopes. The advent of the Very Large Array makes a search for emission from a large number of these stars feasible.

scholarly journals Atmospheric Diagnostics of Wolf-Rayet Stars

1988 ◽  
Vol 108 ◽  
pp. 148-149
Author(s):  
C. Doom
Keyword(s):  
Mass Loss ◽  
Optical Depth ◽  
Stellar Wind ◽  
Free Parameter ◽  
Loss Rate ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
Terminal Velocity ◽  
Accurate Data ◽  
Slowly Varying Function

Wolf-Rayet (WR) stars are the descendants of massive stars that have lost their hydrogen rich envelope. Recently more accurate data on WR stars have become available: mass-loss rates (van der Hucht et al. 1986), radii and luminosities (Underhill 1983, Nussbaumer et al. 1982).It may therefore be worthwhile to investigate if combinations of observed parameters shed some light on the structure of the extended stellar wind of WR stars.In many WR stars the photosphere is situated in the stellar wind. We assume that the wind is stationary and isotropic. Further we assume a velocity law v(r)=v∞(1−Rs/r)β where v∞ is the terminal velocity of the wind in km/s, Rs is the radius where the wind acceleration starts and β > 0 is a free parameter. We can then easily compute the level R in the wind where the photosphere is located (de Loore et al. 1982): R is the solution of the equation 6.27 10−9 τat R v∞/ = fβ(Rs/R) where τat is the optical depth at the photosphere (2/3 or 1), (>0) is the mass loss rate in M⊙/yr and fβ > 1 is a slowly varying function (Doom 1987).

scholarly journals The dichotomy of atmospheric escape in AU Mic b

2020 ◽  
Vol 498 (1) ◽  
pp. L53-L57
Author(s):  
S Carolan ◽  
A A Vidotto ◽  
P Plavchan ◽  
C Villarreal D’Angelo ◽  
G Hazra
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Evaporation Rate ◽  
Loss Rate ◽  
Extreme Ultraviolet ◽  
Mass Loss Rate ◽  
Young Star ◽  
Planetary Atmosphere ◽  
The Other ◽  
Atmospheric Escape

ABSTRACT Here, we study the dichotomy of the escaping atmosphere of the newly discovered close-in exoplanet AU Microscopii (AU Mic) b. On one hand, the high extreme-ultraviolet stellar flux is expected to cause a strong atmospheric escape in AU Mic b. On the other hand, the wind of this young star is believed to be very strong, which could reduce or even inhibit the planet’s atmospheric escape. AU Mic is thought to have a wind mass-loss rate that is up to 1000 times larger than the solar wind mass-loss rate ($\dot{\mathrm{ M}}_\odot$). To investigate this dichotomy, we perform 3D hydrodynamics simulations of the stellar wind–planetary atmosphere interactions in the AU Mic system and predict the synthetic Ly α transits of AU Mic b. We systematically vary the stellar wind mass-loss rate from a ‘no wind’ scenario to up to a stellar wind with a mass-loss rate of $1000~\dot{\mathrm{ M}}_\odot$. We find that, as the stellar wind becomes stronger, the planetary evaporation rate decreases from 6.5 × 1010  g s−1 to half this value. With a stronger stellar wind, the atmosphere is forced to occupy a smaller volume, affecting transit signatures. Our predicted Ly α absorption drops from $\sim 20{{\ \rm per\ cent}}$ in the case of ‘no wind’ to barely any Ly α absorption in the extreme stellar wind scenario. Future Ly α transits could therefore place constraints not only on the evaporation rate of AU Mic b, but also on the mass-loss rate of its host star.

Mass flow and evolution of UW Canis Majoris

1979 ◽  
Vol 83 ◽  
pp. 281-286
Author(s):  
Yoji Kondo ◽  
George E. McCluskey ◽  
Jürgen Rahe
Keyword(s):  
Mass Loss ◽  
Mass Flow ◽  
Radiation Pressure ◽  
Stellar Wind ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Primary Component ◽  
Uv Spectrum ◽  
Solar Mass ◽  
Eclipsing Binary

The far-UV spectrum of the eclipsing binary UW CMa (O7f + O-B) had earlier been utilized to derive a mass-loss rate of about 10−6 to 10−5 solar mass per year. The mass flow seems to be basically in the form of a stellar wind emanating from the O7f primary component, with radiation pressure as the controlling factor. The main characteristics that make UW CMa a possible progenitor of a Wolf-Rayet system are discussed.

scholarly journals Effects of the stellar wind on the Ly α transit of close-in planets

2020 ◽  
Vol 500 (3) ◽  
pp. 3382-3393
Author(s):  
S Carolan ◽  
A A Vidotto ◽  
C Villarreal D’Angelo ◽  
G Hazra
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Escape Rate ◽  
Stellar Winds ◽  
Solar Mass ◽  
Atmospheric Escape ◽  
Exchange Processes ◽  
Sonic Surface

ABSTRACT We use 3D hydrodynamics simulations followed by synthetic line profile calculations to examine the effect increasing the strength of the stellar wind has on observed Ly α transits of a hot Jupiter (HJ) and a warm Neptune (WN). We find that increasing the stellar wind mass-loss rate from 0 (no wind) to 100 times the solar mass-loss rate value causes reduced atmospheric escape in both planets (a reduction of 65 per cent and 40 per cent for the HJ and WN, respectively, compared to the ‘no wind’ case). For weaker stellar winds (lower ram pressure), the reduction in planetary escape rate is very small. However, as the stellar wind becomes stronger, the interaction happens deeper in the planetary atmosphere, and, once this interaction occurs below the sonic surface of the planetary outflow, further reduction in evaporation rates is seen. We classify these regimes in terms of the geometry of the planetary sonic surface. ‘Closed’ refers to scenarios where the sonic surface is undisturbed, while ‘open’ refers to those where the surface is disrupted. We find that the change in stellar wind strength affects the Ly α transit in a non-linear way (note that here we do not include charge-exchange processes). Although little change is seen in planetary escape rates (≃ 5.5 × 1011 g s−1) in the closed to partially open regimes, the Ly α absorption (sum of the blue [−300, −40 km s−1] and red [40, 300 km s−1] wings) changes from 21 to 6 per cent as the stellar wind mass-loss rate is increased in the HJ set of simulations. For the WN simulations, escape rates of ≃ 6.5 × 1010 g s−1 can cause transit absorptions that vary from 8.8 to 3.7 per cent, depending on the stellar wind strength. We conclude that the same atmospheric escape rate can produce a range of absorptions depending on the stellar wind and that neglecting this in the interpretation of Ly α transits can lead to underestimation of planetary escape rates.

scholarly journals Wind inhibition by X-ray irradiation in HMXBs: the influence of clumping and the final X-ray luminosity

2018 ◽  
Vol 620 ◽  
pp. A150 ◽  
Author(s):  
J. Krtička ◽  
J. Kubát ◽  
I. Krtičková
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Terminal Velocity ◽  
High Mass ◽  
Small Scale ◽  
X Rays ◽  
X Ray ◽  
X Ray Binaries

Context. In wind-powered X-ray binaries, the radiatively driven stellar wind from the primary may be inhibited by the X-ray irradiation. This creates the feedback that limits the X-ray luminosity of the compact secondary. Wind inhibition might be weakened by the effect of small-scale wind inhomogeneities (clumping) possibly affecting the limiting X-ray luminosity. Aims. We study the influence of X-ray irradiation on the stellar wind for different radial distributions of clumping. Methods. We calculate hot star wind models with external irradiation and clumping using our global wind code. The models are calculated for different parameters of the binary. We determine the parameters for which the X-ray wind ionization is so strong that it leads to a decrease of the radiative force. This causes a decrease of the wind velocity and even of the mass-loss rate in the case of extreme X-ray irradiation. Results. Clumping weakens the effect of X-ray irradiation because it favours recombination and leads to an increase of the wind mass-loss rate. The best match between the models and observed properties of high-mass X-ray binaries (HMXBs) is derived with radially variable clumping. We describe the influence of X-ray irradiation on the terminal velocity and on the mass-loss rate in a parametric way. The X-ray luminosities predicted within the Bondi-Hoyle-Lyttleton theory agree nicely with observations when accounting for X-ray irradiation. Conclusions. The ionizing feedback regulates the accretion onto the compact companion resulting in a relatively stable X-ray source. The wind-powered accretion model can account for large luminosities in HMXBs only when introducing the ionizing feedback. There are two possible states following from the dependence of X-ray luminosity on the wind terminal velocity and mass-loss rate. One state has low X-ray luminosity and a nearly undisturbed wind, and the second state has high X-ray luminosity and exhibits a strong influence of X-rays on the flow.

Sign in / Sign up

Export Citation Format

Share Document