scholarly journals The WR/WRProgenitor Number Ratio: Theory and Observations

1991 ◽  
Vol 143 ◽  
pp. 553-553
Author(s):  
D. Vanbeveren
Keyword(s):  
Mass Loss ◽  
Massive Star ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Mass Range ◽  
Theoretical Explanation ◽  
The Sun ◽  
Evolutionary Computations ◽  
Number Ratio ◽  
Observational Uncertainty

A direct comparison between the observed WR/WRprogenitor number ratio within 2.5 kpc from the sun and the predicted value (using evolutionary computations of single stars of Maeder and Meynet, 1987, A.&A.182, 243) reveals a discrepancy of at least a factor of two. In a previous study (Vanbeveren, 1990, A.&A. in press) I proposed a solution based on the incompleteness of the observed OB type star sample within 2.5 kpc from the sun. In this summary, I propose a theoretical explanation for the discrepancy. The theoretically predicted WR/WRprogenitor number ratio critically depends on the adopted M formalism in evolutionary computations during the red supergiant phase (RSG) of a massive star, especially in the mass range 20-40 M⊙. Since any M formalism predicts the mass loss rate with an uncertainty of at least a factor of two, I have tried to look for solutions for the WR/WRprogenitor problem by using different values of M during the RSG (in the mass range 20-40 M⊙); the M values and formalism that were adopted were always choosen within the observational uncertainty (i.e. within a factor of two when compared to the formalism used by Maeder and Meynet, 1987).

scholarly journals Mass loss via solar wind and coronal mass ejections during solar cycles 23 and 24

2019 ◽  
Vol 486 (4) ◽  
pp. 4671-4685 ◽  
Author(s):  
Wageesh Mishra ◽  
Nandita Srivastava ◽  
Yuming Wang ◽  
Zavkiddin Mirtoshev ◽  
Jie Zhang ◽  
...  
Keyword(s):  
Solar Wind ◽  
Mass Loss ◽  
Sunspot Number ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Occurrence Rate ◽  
The Sun ◽  
Solar Cycles ◽  
X Ray ◽  
X Ray Background

ABSTRACT Similar to the Sun, other stars shed mass and magnetic flux via ubiquitous quasi-steady wind and episodic stellar coronal mass ejections (CMEs). We investigate the mass loss rate via solar wind and CMEs as a function of solar magnetic variability represented in terms of sunspot number and solar X-ray background luminosity. We estimate the contribution of CMEs to the total solar wind mass flux in the ecliptic and beyond, and its variation over different phases of the solar activity cycles. The study exploits the number of sunspots observed, coronagraphic observations of CMEs near the Sun by SOHO/LASCO, in situ observations of the solar wind at 1 AU by WIND, and GOES X-ray flux during solar cycles 23 and 24. We note that the X-ray background luminosity, occurrence rate of CMEs and ICMEs, solar wind mass flux, and associated mass loss rates from the Sun do not decrease as strongly as the sunspot number from the maximum of solar cycle 23 to the next maximum. Our study confirms a true physical increase in CME activity relative to the sunspot number in cycle 24. We show that the CME occurrence rate and associated mass loss rate can be better predicted by X-ray background luminosity than the sunspot number. The solar wind mass loss rate which is an order of magnitude more than the CME mass loss rate shows no obvious dependency on cyclic variation in sunspot number and solar X-ray background luminosity. These results have implications for the study of solar-type stars.

scholarly journals Effect of a Dipole Magnetic Field on Stellar Mass-Loss

2016 ◽  
Vol 12 (S329) ◽  
pp. 242-245
Author(s):  
Chris Bard ◽  
Richard Townsend
Keyword(s):  
Magnetic Fields ◽  
Mass Loss ◽  
Large Scale ◽  
Massive Star ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Local Environment ◽  
Surface Mass ◽  
B Stars ◽  
Dipole Magnetic Field

AbstractMassive star winds greatly influence the evolution of both their host star and local environment though their mass-loss rates, but current radiative line-driven wind models do not incorporate any magnetic effects. Recent surveys of O and B stars have found that about ten percent have large-scale, organized magnetic fields. These massive-star magnetic fields, which are thousands of times stronger than the Sun’s, affect the inherent properties of their own winds by changing the mass-loss rate. To quantify this, we present a simple surface mass-flux scaling over the stellar surface which can be easily integrated to get an estimate of the mass-loss rate for a magnetic massive star. The overall mass-loss rate is found to decrease by factors of 2-5 relative to the non-magnetic CAK mass-loss rate.

scholarly journals The luminosity distribution of RSGs to test their mass-loss rate

2015 ◽  
Vol 11 (A29B) ◽  
pp. 454-454 ◽  
Author(s):  
Cyril Georgy ◽  
Sylvia Ekström
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Massive Star ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Red Supergiants ◽  
Loss Rates

AbstractThe red supergiant phase is an important phase of the evolution of massive star, as it mostly determines its final stages. One of the most important driver of the evolution during this phase is mass loss. However, the mass-loss rates prescription used for red supergiants in current stellar evolution models are still very inaccurate.Varying the mass-loss rate makes the star evolve for some time in yellow/blue regions of the HRD, modifying the number of RSGs in some luminosity ranges. Figure 1 shows how the luminosity distribution of RSGs is modified for various mass-loss prescriptions. This illustrates that it is theoretically possible to determine at least roughly what is the typical mass loss regime of RSGs in a stellar evolution perspective.

scholarly journals Progenitor for Type Ic Supernova 2007bi

2011 ◽  
Vol 7 (S279) ◽  
pp. 427-428
Author(s):  
Takashi Yoshida ◽  
Hideyuki Umeda
Keyword(s):  
Light Curve ◽  
Mass Loss ◽  
Loss Rate ◽  
Main Sequence ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
Mass Range ◽  
Stellar Mass ◽  
Core Collapse ◽  
Core Collapse Supernova

AbstractWe investigate the evolution of very massive stars with Z = 0.2 Z⊙ to constrain the progenitor of the extremely luminous Type Ic SN 2007bi. In order to reproduce the 56Ni amount produced in SN 2007bi, the range of the stellar mass at the zero-age main-sequence is expected to be 515 - 575M⊙ for pair-instability supernova and 110 - 280M⊙ for core-collapse supernova. Uncertainty in the mass loss rate affects the mass range appropriate for the explosion of SN 2007bi. A core-collapse supernova of a WO star evolved from a 110 M⊙ star produces sufficient radioactive 56Ni to reproduce the light curve of SN 2007bi.

scholarly journals Influence of Coronal Mass Ejections from the Red Dwarf Component on the Accretion Pattern in CVs and LMXBs

1995 ◽  
Vol 151 ◽  
pp. 195-196
Author(s):  
Roberto Minarini ◽  
Grigory Beskin
Keyword(s):  
Mass Loss ◽  
Coronal Mass Ejections ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Magnetic Activity ◽  
The Sun ◽  
Surface Mass ◽  
Red Dwarfs ◽  
Low Mass ◽  
Transient Events

Low-mass main sequence stars show a magnetic activity similar to the Sun and as a consequence they lose mass in the form of a variable stellar wind. In the latest spectral types (red dwarfs) the activity and the mass loss rate appear to increase by a large factor of ∼ 103 with respect to the solar case, reaching Ṁ ∼ 2 · 10−11 M⊙/yr (Badalyan & Livshits 1992, Katsova 1993). The same happens for coronal mass ejections (CMEs), which are the most relevant transient events of mass loss in these objects. In the Sun, these appear as bubbles of coronal material, with dimensions of some fraction of the solar surface, mass M ≃ 2 · 1014 - 2 · 1016 g and ejection velocity v ≃ 3 · 107 - 2 · 108 cm/s, with an instantaneous mass loss rate Ṁ ∽ 10−13 - 10−11 M⊙/yr (Wagner 1984). In red dwarfs, as recently observed, the ejection velocities are higher, up to v ≃ 3 · 108 cm/s and the mass loss rate can reach the value Ṁ ≃ 10−8 M⊙/yr (Mullan et al. 1989, Houdebine et al. 1990). In both cases, the observations suggest that a bubble expands, once ejected, with a velocity of several hundreds of km/s.

scholarly journals Simulations of solar wind variations during an 11-year cycle and the influence of north–south asymmetry

2018 ◽  
Vol 84 (5) ◽  
Author(s):  
B. Perri ◽  
A. S. Brun ◽  
V. Réville ◽  
A. Strugarek
Keyword(s):  
Solar Wind ◽  
Mass Loss ◽  
Loss Rate ◽  
Transport Model ◽  
Magnetic Energy ◽  
Mass Loss Rate ◽  
Phase Lag ◽  
The Sun ◽  
Flux Transport ◽  
South Asymmetry

We want to study the connections between the magnetic field generated inside the Sun and the solar wind impacting Earth, especially the influence of north–south asymmetry on the magnetic and velocity fields. We study a solar-like 11-year cycle in a quasi-static way: an asymmetric dynamo field is generated through a 2.5-dimensional (2.5-D) flux-transport model with the Babcock–Leighton mechanism, and then is used as bottom boundary condition for compressible 2.5-D simulations of the solar wind. We recover solar values for the mass loss rate, the spin-down time scale and the Alfvén radius, and are able to reproduce the observed delay in latitudinal variations of the wind and the general wind structure observed for the Sun. We show that the phase lag between the energy of the dipole component and the total surface magnetic energy has a strong influence on the amplitude of the variations of global quantities. We show in particular that the magnetic torque variations can be linked to topological variations during a magnetic cycle, while variations in the mass loss rate appear to be driven by variations of the magnetic energy.

scholarly journals The Influence of WR Like Stellar Wind Mass Loss Rates on the Evolution of Massive Core Helium Burning Stars

1991 ◽  
Vol 143 ◽  
pp. 555-555
Author(s):  
D. Vanbeveren
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Loss Rate ◽  
Phenomenological Study ◽  
Mass Loss Rate ◽  
Close Binaries ◽  
Evolutionary Computations ◽  
Helium Burning ◽  
Binary Nature ◽  
Convective Core

Evolutionary computations of massive close binaries (MCB) including the effects of stellar wind (SW) and convective core overshooting predict that all massive primaries with ZAMS mass larger than 10 M⊙ start their core helium burning phase (CHeB) as bare helium cores; the hydrogen rich layers are removed on a timescale of the order of 104 yrs as a consequence of Roche lobe overflow (RLOF). The CHeB remnant after RLOF resembles closely a zero age CHeB star and its further evolution is entirely independent from its binary nature. Similarly as has been done previously by Vanbeveren and Packet (1979, A.&A.80, 242), I have performed a phenomenological study on the evolution of massive hydrogen less CHeB stars including the effect of SW mass loss using updated M determinations of van der Hucht et al. (1986, A.&A.168, 111). The SW mass loss rate formalism used in the computations is based on the following requirements:

Sign in / Sign up

Export Citation Format

Share Document