Non-conservative evolution in Algols: where is the matter?
Non-conservative evolution in Algols: where is the matter?
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Algols 中的非保守进化：问题出在哪里？
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发表时间：
2015
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影响因子：
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通讯作者：
P. Camps
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作者：
R. Deschamps;K. Braun;A. Jorissen;L. Siess;M. Baes;P. Camps
上下文有收集间接证据表明非保守的演变在阿尔戈。然而，系统的质量损失率的观测约束较差，通常设置为一个自由参数的双星演化模拟。此外，系统性质量损失可能会导致观测信号，这些信号仍有待发现。在“热点”喷射机制中，一些最初从伴星星星通过吸积流转移的物质由于撞击物质在伴星表面释放的辐射能量而被驱逐出系统。本文的目的是从这个过程中检索可观察的数量，并将它们与观测进行比较。方法.我们研究了外流气体和可能存在的尘埃颗粒对光谱能量分布（SED）的影响。我们使用了一维等离子体程序Cloudy，并与三维蒙特-卡罗辐射传输程序Skirt的尘埃模拟结果进行了比较。的circumbinary质量分布和二进制参数计算与国家的最先进的二进制计算完成的Binstar演化代码。结果流出的物质降低了恒星SED在光学和紫外波段的连续通量水平。由于这种效应的时间依赖性，它可能有助于区分不同的喷射机制。尘埃，如果存在的话，即使在尘埃与气体的比率很低的情况下，也会导致观测到红外线的过量，并在距离星星很远的地方追踪到冷物质。通过在WISE星表中寻找这种尘埃发射，我们发现了少数Algol显示出红外过量，其中两个相当令人惊讶的物体SX Aur和CZ Vel。我们发现，一些二元B [e]星显示出相同的强巴耳末连续，我们预测与我们的模型。然而，系统质量损失的直接证据可能在真正的Algols中无法观察到，因为这些系统不再通过热点机制喷射质量。此外，由于流速高，流出的物质在几百年内就会消失。如果足够热，热点可能会产生高度电离的物种，如Siiv和可观察到的特征，这是典型的W Ser系统。结论.如果存在系统性质量损失，则会导致清晰的观察印记。这些特征并不存在于真正的藻藻中，而是存在于与之密切相关的天琴座β星、蛇形W星、双周期变星、共生藻和双星B[e]中。我们强调，需要进一步观察这些物体的系统质量损失是最有可能发生的。
Context. There is gathering indirect evidence suggesting 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 are stil l to be found. Aims. Within the ‘hotspot’ ejection mechanism, some of the materi al 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 impactin g material. The objective of this paper is to retrieve observable quanti ties from this process, and to compare them with observations. Methods. We investigate the impact of the outflowing gas and the possib le presence of dust grains on the spectral energy distributi on (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 are computed with state-of-the-art binary calculations done with the Binstar evolution code. Results. The outflowing material reduces the continuum flux-level of t he stellar SED in the optical and UV. Due to the timedependence of this effect, it may help to distinguish between different ejection mechanisms. Dust, if present, leads to obser vable infrared excesses even with low dust-to-gas ratios and traces the cold material at large distances from the star. By sear ching for such 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 dis sipates in a few hundred years. If hot enough, the hotspot may produce highly ionised species such as Siiv and observable characteristics that are typical of W Ser systems. Conclusions. Systemic mass loss, if present, leads to clear observationa l imprints. These signatures are not to be found in genuine Algols but in the closely relatedβ 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.