A spectroscopic study of the Algol-type binaries S Equulei and KO Aquilae: absolute parameters and mass transfer

Soydugan, F.; Frasca, A.; Soydugan, E.; Catalano, S.; Demirçan, Osman; İbanoǧlu, C.

doi:10.1111/j.1365-2966.2007.12065.x

Cited by 20 publications

(16 citation statements)

References 46 publications

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“…The data of Panchatsaram & Abhyankar (1981) yield a detached system and have therefore been disregarded. dP dt is taken from Panchatsaram & Abhyankar (1981) and Soydugan et al (2007). This system has an accretion disc with R disc ≈ 1.5 × R g .…”

Section: Ko Aqlmentioning

confidence: 99%

Spin-up and hot spots can drive mass out of a binary

Greve¹,

Loore²,

Mennekens³

2008

A&A

100

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Context. The observed distribution of orbital periods of Algols with a B-type primary at birth agrees fairly well with the prediction from conservative theory. Conservative evolution fails, however, to produce the rather large fraction of Algols observed with a high mass-ratio, especially: q ∈ [0.4-0.6]. Aims. In order to keep Algols for a longer time with a higher mass-ratio without disturbing the distribution of orbital periods too much, interacting binaries have to lose a significant fraction of their total mass without losing much angular momentum before or during Algolism. We propose a mechanism that meets both requirements. Methods. In the case of direct impact the gainer spins up: sometimes up to critical velocity. Equatorial material on the gainer is therefore less bound. A similar statement applies to material located at the edge of an accretion disc. The incoming material moreover creates a hot spot in the area of impact. The sum of the rotational and radiative energy of hot spot material depends on the masstransfer-rate. The sum of both energies overcomes the binding energy at a well defined critical value of the mass-transfer-rate. As long as the transfer-rate is smaller than this critical value RLOF happens conservatively. But as soon as the critical rate is exceeded the gainer will acquire no more than the critical value and RLOF runs into a liberal era. Results. Low-mass binaries never achieve mass-transfer-rates larger than the critical value. Intermediate-mass binaries evolve mainly conservatively but mass will be blown away from the system during the short era of rapid mass-transfer soon after the onset of RLOF. We have calculated the evolution of binaries with a 9 M primary and a 5.4 M companion over a range of initial orbital periods, covering case-A RLOF. Mass-loss from the system is achieved during direct impact only. Conclusions. We find systems that show Algolism for more than ten million years. RLOF occurs almost always conservatively. Only during some 20 000 years the gainer is not capable of grasping all the material that comes from the donor. The mass-ratio q ∈ [0.4-0.6] which was hardly populated by conservative evolution now contains Algols for a significant fraction of their existence.

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Section: Ko Aqlmentioning

confidence: 99%

Spin-up and hot spots can drive mass out of a binary

Greve¹,

Loore²,

Mennekens³

2008

A&A

100

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“…stellar surface and increase the luminosity locally. This hotspot is observed in some Algol-like stars (e.g., Banks et al 1990;Weiland et al 1995;Richards & Albright 1999, in case of direct accretion on the stellar surface and Harmanec 2002; Soydugan et al 2007 in case of accretion on the edge of a disc).…”

Section: Introductionmentioning

confidence: 99%

Non-conservative evolution in Algols: where is the matter?

Deschamps

Braun

Jorissen

et al. 2015

A&A

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Context. There is indirect evidence of non-conservative evolutions in Algols. However, the systemic mass-loss rate is poorly constrained by observations and generally set as a free parameter in binary-star evolution simulations. Moreover, systemic mass loss may lead to observational signatures that still need to be found. Aims. Within the "hotspot" ejection mechanism, some of the material that is initially transferred from the companion star via an accretion stream is expelled from the system due to the radiative energy released on the gainer's surface by the impacting material. The objective of this paper is to retrieve observable quantities from this process and to compare them with observations. Methods. We investigate the impact of the outflowing gas and the possible presence of dust grains on the spectral energy distribution (SED). We used the 1D plasma code Cloudy and compared the results with the 3D Monte-Carlo radiative transfer code Skirt for dusty simulations. The circumbinary mass-distribution and binary parameters were computed with state-of-the-art binary calculations done with the Binstar evolution code. Results. The outflowing material reduces the continuum flux level of the stellar SED in the optical and UV. Because of the timedependence of this effect, it may help to distinguish between different ejection mechanisms. If present, dust leads to observable infrared excesses, even with low dust-to-gas ratios, and traces the cold material at large distances from the star. By searching for this dust emission in the WISE catalogue, we found a small number of Algols showing infrared excesses, among which the two rather surprising objects SX Aur and CZ Vel. We find that some binary B[e] stars show the same strong Balmer continuum as we predict with our models. However, direct evidence of systemic mass loss is probably not observable in genuine Algols, since these systems no longer eject mass through the hotspot mechanism. Furthermore, owing to its high velocity, the outflowing material dissipates in a few hundred years. If hot enough, the hotspot may produce highly ionised species, such as Si iv, and observable characteristics that are typical of W Ser systems. Conclusions. If present, systemic mass loss leads to clear observational imprints. These signatures are not to be found in genuine Algols but in the closely related β Lyraes, W Serpentis stars, double periodic variables, symbiotic Algols, and binary B[e] stars. We emphasise the need for further observations of such objects where systemic mass loss is most likely to occur.

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“…It is clear that the observed gainers are underluminous compared to the theoretical counterparts, as was previously noted by Soydugan et al (2007). The evolution of a close binary can be divided into two distinct phases: an initial phase of fast mass transfer (increasingṀ) on a thermal timescale, and a later phase of slower mass transfer (decreasingṀ) on a nuclear timescale (e.g.…”

Section: Comparison With Single Star Evolutionmentioning

confidence: 59%

“…TheṀ for RZ Cas was derived from O-C curves. For KO Aql and S Equ, we use the results of Soydugan et al (2007). All these are given in Table 1.…”

Section: Introductionmentioning

confidence: 99%

On the origin and evolutionary state of RZ Cassiopeiae, KO Aquilae, and S Equulei

Mennekens

Greve

Yungelson

2008

A&A

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Aims. We determine the present evolutionary state and the restrictions on the initial mass ratios of RZ Cas, KO Aql and S Equ. Methods. We compare mass-gaining stars with evolutionary models of single stars with the same mass and subsequently compare them with accretion tracks from simultaneous conservative binary evolution. Results. The gainers are in an early main sequence stage (X c > 0.5), with KO Aql being almost unevolved (assuming quasi-thermal equilibrium). The initial donor/gainer mass ratios M di /M gi must be larger than three to obtain the present mass and luminosity of the gainers.

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A spectroscopic study of the Algol-type binaries S Equulei and KO Aquilae: absolute parameters and mass transfer

Cited by 20 publications

References 46 publications

Spin-up and hot spots can drive mass out of a binary

Spin-up and hot spots can drive mass out of a binary

Non-conservative evolution in Algols: where is the matter?

On the origin and evolutionary state of RZ Cassiopeiae, KO Aquilae, and S Equulei

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