Structure of gas flows in Z And in quiescence and during outbursts

Bisikalo, D. V.; Boyarchuk, A. A.; Kilpio, E. Yu.; Кузнецов, О. А.

doi:10.1134/1.1529260

Cited by 21 publications

(24 citation statements)

References 13 publications

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“…In this case the ratio of the two values is about 70. One possible reason for the increase of the accretion rate was proposed by Bisikalo et al (2002). They theoretically considered the evolution of the gas flow in the vicinity of the accretor of Z And and reached the conclusion that the accretion rate can strongly increase as a result of a change of the velocity of the cool giant wind.…”

Section: Discussionmentioning

confidence: 99%

Broad-band multicolour observations of the symbiotic binary Z And during quiescence and its activity at the end of 2002

Tomov

Tomova

Taranova

2004

A&A

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Abstract. Broad-band UBVRJHKLM photometry of the classical symbiotic binary system Z And obtained at the time of the light maximum of its small-amplitude brightening at the end of 2002 as well as at four epochs before and after this brightening is analysed. The parameters of the symbiotic nebula were obtained from its spectral energy distribution at the epochs of the quiescent state of the system using the energy distribution of the stellar components derived in a previous investigation. The continuum analysis based on the data during the active phase shows that the energy distribution of the compact secondary was changed very little -it remained a hot object emitting mostly in the UV, as in the quiescent state. On the basis of this result the brightening is supposed to be due to a slow expansion to about two times its quiescent size. The possibility of hydrogen burning at the surface of the secondary during quiescence is discussed.

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Section: Discussionmentioning

confidence: 99%

Broad-band multicolour observations of the symbiotic binary Z And during quiescence and its activity at the end of 2002

Tomov

Tomova

Taranova

2004

A&A

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“…For transition from quiescent to active state it is necessary to provide an increase in the accretion rate on a rather long time interval corresponding to the characteristic time of the outburst development (∼100 days). Earlier, in [21], a mechanism providing the required accretion rate increase in the system has been proposed on the basis of 2D calculations. According to this mechanism even minor change of the donor's wind velocity is enough for the accretion regime to change.…”

Section: Discussionmentioning

confidence: 99%

“…It should be noted that the time scale of the accretion rate increase should correspond to the characteristic time of outburst development (∼ 100 days). Such behaviour of the accretion rate in a binary system is possible in the framework of the mechanism proposed in [21] using results of 2D gasdynamic modelling. The main idea of the mechanism is that even minor variations in the donor's wind velocity is enough to lead to the accretion regime changefrom disc accretion to wind accretion.…”

Section: If For Some Reasonmentioning

confidence: 99%

Three-dimensional gas-dynamical modeling of changes in the flow structure during the transition from the quiescent to the active state in symbiotic stars

et al. 2005

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The results of 3D modelling of the flow structure in the classical symbiotic system Z Andromedae are presented. Outbursts in systems of this type occur when the accretion rate exceeds the upper limit of the steady burning range. Therefore, in order to realize the transition from a quiescent to an active state it is necessary to find a mechanism able to sufficiently increase the accretion rate on a time scale typical to the duration of outburst development.Our calculations have confirmed the transition mechanism from quiescence to outburst in classic symbiotic systems suggested earlier on the basis of 2D calculations (Bisikalo et al, 2002). The analysis of our results have shown that for wind velocity of 20 km/s an accretion disc forms in the system. The accretion rate for the solution with 1 2 the disc is ∼ 22.5 − 25% of the mass loss rate of the donor, that is, ∼ 4.5 − 5 · 10 −8 M ⊙ /yr for Z And. This value is in agreement with the steady burning range for white dwarf masses typically accepted for this system. When the wind velocity increases from 20 to 30 km/s the accretion disc is destroyed and the matter of the disc falls onto the accretor's surface. This process is followed by an approximately twofold accretion rate jump. The resulting accretion rate growth is sufficient for passing the upper limit of the steady burning range, thereby bringing the system into an active state. The time during which the accretion rate is above the steady burning value is in a very good agreement with observations.The analysis of the results presented here allows us to conclude that small variations in the donor's wind velocity can lead to the transition from the disc accretion to the wind accretion and, as a consequence, to the transition from quiescent to active state in classic symbiotic stars.

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“…Small variations in the accretion rate can lead the accretor to expand at approximately constant bolometric luminosity (Mikolajewska & Kenyon 1992), which was assumed to be the most probable scenario for the optical outbursts of Z And (Fernandez-Castro et al 1995). Bisikalo et al (2002) have modelled the evolution of the gas flow in the vicinity of the hot compact component of Z And, which accretes matter of the wind of the cool giant. They have considered the dependence of the accretion rate on the wind velocity.…”

Section: Discussionmentioning

confidence: 99%

Mass ejection by the symbiotic binary Z And during its 2000–2002 outburst

Tomov

Taranova²,

Tomova

2003

A&A

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Abstract. Broad-band UBV JHKLM data have been obtained at the time of the quiescent orbital photometric maximum of the classical symbiotic binary system Z And and at some epochs of its 2000-2002 active phase. The data of the active phase are related to the time of the optical maximum and after it when the star was returning to quiescence. Broad-band quiescent RI photometry from the literature was also used to obtain the parameters of the cool component of this binary. All of these data suggest that the hot compact component has undergone a major expansion and the emission measure of the circumbinary nebula has also increased. Some mechanisms for interpretation of the outburst are reviewed.

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Structure of gas flows in Z And in quiescence and during outbursts

Cited by 21 publications

References 13 publications

Broad-band multicolour observations of the symbiotic binary Z And during quiescence and its activity at the end of 2002

Broad-band multicolour observations of the symbiotic binary Z And during quiescence and its activity at the end of 2002

Three-dimensional gas-dynamical modeling of changes in the flow structure during the transition from the quiescent to the active state in symbiotic stars

Mass ejection by the symbiotic binary Z And during its 2000–2002 outburst

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