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 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 The Gaseous Envelope Structure of the Eclipsing Binary System V448 Cyg

1992 ◽  
Vol 135 ◽  
pp. 333-335
Author(s):  
G.V. Manilova (Volkova)
Keyword(s):  
Binary System ◽  
Mass Loss ◽  
Mass Flow ◽  
Stellar Wind ◽  
Primary Component ◽  
Circumstellar Envelope ◽  
Hot Stars ◽  
Eclipsing Binary ◽  
Uncommon Case ◽  
Gaseous Envelope

V448 Cyg (HD 190967 = BD+34°3871) represents rather an uncommon case, where the primary component (indicated by stronger lines in the combined spectrum) is the star exhibiting mass loss. The system has a circumstellar envelope, formed by mass flow from a primary component filling its Roche lobe, and by a stellar wind that is stimulated by the duplicity of this system of two hot stars (BO Ib + O9.5 V — see Glazunova et al. 1963). Ultraviolet, polarimetric, and spectral observations of V448 Cyg permitted us to form a model of the structure and parameters of this system’s circumstellar envelope.

scholarly journals The Mass Loss Rate — Period Relation in Carbon Miras

1995 ◽  
Vol 155 ◽  
pp. 141-142
Author(s):  
Martin Groenewegen
Keyword(s):  
Mass Loss ◽  
Radiation Pressure ◽  
Linear Relation ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Pulsation Period ◽  
Sudden Increase ◽  
Period Relation ◽  
Dust Mass ◽  
Rate Period

AbstractThe relation between mass loss rate and pulsation period in carbon Miras is discussed. The dust mass loss rate is very low (about 2 10−10 M⊙yr) up to about P = 380 days, where there is a sudden increase. For P > 400 days there is a linear relation between log and P. The change in the mass loss rate near 380 days may be related to radiation pressure on dust becoming effective in driving the outflow.

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 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 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.

scholarly journals Mass loss from metal-poor stars

1981 ◽  
Vol 59 ◽  
pp. 297-300
Author(s):  
C. Chiosi ◽  
G. Bertelli ◽  
E. Nasi ◽  
L. Greggio
Keyword(s):  
Mass Loss ◽  
Radiation Pressure ◽  
Loss Rate ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
Rate Relationship ◽  
Effective Temperatures ◽  
Hr Diagram ◽  
Pressure Driven

1. IntroductionIt is essential to consider the effect of mass loss to understand the distribution of supergiant stars in the HR diagram. This research concerns the evolution of massive stars with X=0.700 and Z=0.001 during the phases up to central Heexhaustion with the inclusion of mass loss. Such low value of Z has been chosen in order to allow a comparison with the supergiant stars of SMC. The rate of mass loss is formulated as in Chiosi, Nasi and Sreenivasan (1978). More specifically, in the range of high effective temperatures, we adopt the mass-loss rate relationship for radiation pressure driven wind of Castor, Abbott and Klein (1975), whereas in the range of low effective temperatures we assume the mass loss rate to be driven by the acoustic flux mechanism of Fusi Pecci and Renzini (1975).

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