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arXiv 1405.5658astro-ph.SR
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观测系统V404 Lyr:光的传播时间和剑鱼座γ星的脉动

The Eclipsing System V404 Lyr: Light-Travel Times and Gamma Doradus Pulsations

Jae Woo Lee, Seung-Lee Kim, Kyeongsoo Hong, Chung-Uk Lee, Jae-Rim Koo

摘要:

我们目前的物理性质的V404天琴座表现出日食的时间变化和多周期脉动的所有历史数据,包括开普勒观测。对2,922个最小历元的详细分析表明,轨道周期通过一个向上张开的抛物线和两个正弦曲线变化而变化,周期分别为$P_3$ =649 d和$P_4$ = 2,154 d,半振幅分别为$K_3$ =193 s和$K_4$ =49 s。长期周期的增加可以解释为二次到一次质量传递和角动量损失的组合。对这两个正弦曲线最合理的解释是由于两个投影质量分别为$M_3$ =0.47 M $_\odot$和$M_4$ =0.047 M $_\odot$的环联星天体产生的一对光旅行时间效应。第三体参数与用W-D二进制程序计算的结果一致。当轨道倾角大于43 $^\circ$时,第四颗星的质量在$\sim$ 0.07 M $_\odot$的氢燃烧极限内,这意味着它是一颗棕矮星。通过在次级分量中加入冷斑,得到了满意的开普勒光变曲线模型。结果表明,近距离的食对是半分离的,但近接触的,配置;主填充约93%的限制瓣,比叶填充的次级更大。从开普勒数据中减去合成食曲线后,对光残差进行了多频分析。这表明天琴座V404的主要组成部分是一颗$γ$ Dor型脉动星,在1.85 $-$ 2.11 d $^{-1}$范围内有7个脉动频率,振幅为1.38 $-$ 5.72 mmag,脉动常数为0.24 $-$ 0.27 d。这七个频率被明确地确定为高阶低阶重力模式振荡,可能是通过潮汐相互作用激发的。

英文摘要:

We present the physical properties of V404 Lyr exhibiting eclipse timing variations and multiperiodic pulsations from all historical data including the Kepler observations. Detailed analyses of 2,922 minimum epochs showed that the orbital period has varied through a combination with an upward-opening parabola and two sinusoidal variations, with periods of $P_3$=649 d and $P_4$=2,154 d and semi-amplitudes of $K_3$=193 s and $K_4$=49 s, respectively. The secular period increase could be interpreted as a combination of the secondary to primary mass transfer and angular momentum loss. The most reasonable explanation for both sinusoids is a pair of light-travel-time effects due to two circumbinary objects with projected masses of $M_3$=0.47 M$_\odot$ and $M_4$=0.047 M$_\odot$. The third-body parameters are consistent with those calculated using the W-D binary code. For the orbital inclinations higher than 43$^\circ$, the fourth component has a mass within the hydrogen-burning limit of $\sim$0.07 M$_\odot$, which implies that it is a brown dwarf. A satisfactory model for the Kepler light curves was obtained through applying a cool spot to the secondary component. The results demonstrate that the close eclipsing pair is in a semi-detached, but near-contact, configuration; the primary fills approximately 93% of its limiting lobe and is larger than the lobe-filling secondary. Multiple frequency analyses were applied to the light residuals after subtracting the synthetic eclipsing curve from the Kepler data. This revealed that the primary component of V404 Lyr is a $γ$ Dor type pulsating star, exhibiting seven pulsation frequencies in the range of 1.85$-$2.11 d$^{-1}$ with amplitudes of 1.38$-$5.72 mmag and pulsation constants of 0.24$-$0.27 d. The seven frequencies were clearly identified as high-order low-degree gravity-mode oscillations which might be excited through tidal interaction.

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