About accretion disk of a binary system

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Discussion Overview

The discussion revolves around the mechanisms of mass exchange in X-ray binary systems, particularly focusing on Roche-lobe overflow and stellar winds as methods of mass transfer to a black hole candidate. Participants explore the differences in luminosity behavior between these two mechanisms, questioning the reasons behind periodic outbursts in Roche-lobe overflow systems compared to the continuous nature of wind-fed systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that Roche-lobe overflow systems typically exhibit periodic outbursts, while wind-fed systems are persistently luminous.
  • Another participant suggests that the continuous nature of stellar winds is dependent on the variability of the star itself.
  • A participant questions the relationship between the period of luminosity in Roche-lobe overflow systems and the orbital period of the companion star.
  • It is proposed that interactions within the material in Roche-lobe overflow might lead to the generation of periodic bunches of material.
  • One participant points out that the timescales of years or decades for Roche-lobe overflow are longer than typical orbital periods, indicating a possible complexity in mass accretion dynamics near Lagrangian points.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms and implications of mass transfer in binary systems, with no consensus reached regarding the relationship between luminosity periods and orbital periods.

Contextual Notes

The discussion highlights potential limitations in understanding the dynamics of mass transfer, including the dependence on the definitions of mechanisms and the complexity of interactions at Lagrangian points.

jtceleron
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In an X-ray binary system, in which one of the two objects is black hole candidate, there are several ways to exchange mass.
A paper states that" their host systems are mass-exchange binaries containing a nondegenerate star that supplies gas to the black hole via a stellar wind or via Roche-lobe overflow in a stream that emanates from the inner Lagrangian point. The mass-donor star in the Roche-lobe overflow systems is typically a low mass (~one sun mass) sun-like star, and the X-ray source is transient, alternating between yearlong outbursts and years or decades of quiescence. the wind-fed X-ray source, on the other hand, are fueled by massive hot stars( larger than 10 times of sun mass) and are persistently luminous."

I wonder why the Roche-lobe overflow has a period while the other mechanism has not.
 
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Wind is continuous, as long as the star itself is not variable.
For Roche-lobe overflow, I have to guess: The material can interact with itself, this might generate bunches in some way.
 
mfb said:
Wind is continuous, as long as the star itself is not variable.
For Roche-lobe overflow, I have to guess: The material can interact with itself, this might generate bunches in some way.

what is the difference of the two in mechanism? Does the period of luminosity relate to the period of orbit of the companion star? but if so, why does the stellar wind one not have a period of luminosity.
 
Years or even decades is longer than orbital periods if Roche-lobe overflow is relevant.
Maybe you can have some mass accretion near the lagrange points.
 

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