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THE ECLIPSING SYSTEM EP ANDROMEDAE AND ITS CIRCUMBINARY COMPANIONS

机译:坡地系统EP ANDROMEDAE及其循环附件

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We present new long-term CCD photometry for EP And acquired during the period 2007-2012. The light curves display total eclipses at primary minima and season-to-season light variability. Our synthesis for all available light curves indicates that the eclipsing pair is a W-type overcontact binary with parameters of q = 2.578, i = 833, ΔT?= 27?K, f = 28%, and l 3 = 2%-3%. The asymmetric light curves in 2007 were satisfactorily modeled by a cool spot on either of the eclipsing components from a magnetic dynamo. Including our 95 timing measurements, a total of 414?times of minimum light spanning about 82?yr was used for a period study. A detailed analysis of the eclipse timing diagram revealed that the orbital period of EP And has varied as a combination of an upward-opening parabola and two periodic variations, with cycle lengths of P 3 = 44.6?yr and P 4 = 1.834?yr and semi-amplitudes of K 3 = 0.0100?days and K 4 = 0.0039?days, respectively. The observed period increase at a fractional rate of +1.39?× 10–10 is in excellent agreement with that calculated from the W-D code and can be plausibly explained by some combination of mass transfer from the primary to the secondary star and angular momentum loss due to magnetic braking. The most reasonable explanation for both cycles is a pair of light-travel-time effects driven by the possible existence of a third and fourth component with projected masses of M 3 = 0.25 M ☉ and M 4 = 0.90 M ☉. The more massive companion could be revealed using high-resolution spectroscopic data extending over the course of a few years and could also be a binary itself. It is possible that the circumbinary objects may have played an important role in the formation and evolution of the eclipsing pair, which would cause it to have a short initial orbital period and thus evolve into an overcontact configuration by angular momentum loss.
机译:我们提出了用于EP的新型长期CCD光度法,并已在2007-2012年期间获得。光照曲线显示主要日食和季节不同时的日全食。我们对所有可用光曲线的综合表明,日蚀对是W型超接触二进制,其参数为q = 2.578,i = 833,ΔT?= 27?K,f = 28%和l 3 = 2%-3 %。 2007年的不对称光曲线通过磁发电机中任一蚀分量上的冷点令人满意地建模。包括我们的95个计时测量在内,总共414倍的最小光跨度约为82 yr被用于周期研究。对日食时序图的详细分析显示,EP And的轨道周期已作为向上开口的抛物线和两个周期性变化的组合而变化,周期长度为P 3 = 44.6?yr和P 4 = 1.834?yr,并且半振幅分别为K 3 = 0.0100?days和K 4 = 0.0039?days。观测到的周期以+1.39?×10-10的分数速率增长,与WD编码计算的周期非常吻合,并且可以用从初星到次星的质量转移和角动量损失的某种组合来解释。进行电磁制动。对于两个周期,最合理的解释是由可能存在的第三和第四分量引起的一对光程时间效应,投影质量为M 3 = 0.25 M M和M 4 = 0.90 M driven。可以使用扩展了数年的高分辨率光谱数据揭示更大质量的伴星,并且它本身也可以是二进制的。环绕物体可能在日食对的形成和演化中起了重要作用,这将导致其具有较短的初始轨道周期,并因此由于角动量损失而演变成过接触构型。

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