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浅度相接双星的观测研究
Alternative TitleObservation and study on shallow-contact binaries
何家佳
Subtype博士
Thesis Advisor钱声帮
2009-06-01
Degree Grantor中国科学院研究生院(云南天文台)
Place of Conferral北京
Degree Discipline天体物理
Keyword浅度相接双星 测光观测 周期分析 双星物质交流 角动量损失 双星结构和演化
Abstract浅度相接双星是指相接度小于20%的大熊W(W UMa)型相接双星系统。它们是联系相接双星和半接双星的桥梁,其研究将对了解密近双星质量及角动量的交流和损失以及双星的演化链有着重要的意义。本文对一批样本双星进行了观测和分析,研究了这类特殊双星系统的结构特征和演化状态,同时对浅度相接双星进行了初步的统计分析,取得了如下的研究成果: 1.发现RV Psc和BI CVn是浅度相接的密近双星系统,相接度分别为5.8%和18.0%。且它们的轨道周期都存在长期的减小,减小率分别为-5.89x10-8天/年和-1.51 x 10-7天/年。浅度相接位型、高的质量比和轨道周期的长期减小表明这两颗样本双星是通过Case A的物质交流演化而来的,是刚形成的浅度相接双星系统。随着物质从主星向次星转移,主星的有效温度将会变低,同时质量比变大,轨道周期变小和相接度变大,RV Psc和BI CVn将演化成中度相接的相接双星系统。研究发现BI CVn的轨道周期在长期减小的基础上还叠加有一个振幅为0.0151天,周期为27.0年的周期性变化成分,揭示了系统中存在质量不小于0.58M⊙的第三天体,它的存在可能对这颗相接双星的形成起着重要作用。 2.发现浅度相接双星AE Phe的轨道周期在长期增加的基础上叠加有一个变幅为0.0041天,周期为9.30年的周期性变化。该小变幅周期性变化表明系统中存在极小质量的第三天体。同时解轨分析表明AE Phe是一颗相接度仅为14.6%的浅度相接双星。轨道周期的长期增加,增加率为+5.50 x 10-8天/年,表明系统中存在从次星到主星的物质转移,揭示了它的质量比将不断减小,轨道周期逐渐变长,而向着极浅度双星方向演化。 3.通过解轨分析发现DM Del是一颗主星充满洛希瓣而次星没有充满的半接双星,并发现它的轨道周期在长期减小的基础上叠加有一个振幅为0.0170天,周期为43.0年的周期性变化。DM Del主星充满的半接结构和轨道周期的长期减小揭示了它是处于Case A物质交流演化过程中的双星系统,并将演化成浅度相接双星。 4.发现中度相接双星BS Cas和RT LMi的轨道周期都在长期减小的基础上叠加一个周期变化成分。它们的相接度分别为27.5%和28.2%,轨道周期的减小率分别为:-1.51×10-7天/年和-1.64×10-8天/年。这些结果表明BS Cas和RT LMi是刚从浅度相接演化而来的样本,揭示了它们是浅度相接双星的后续天体。轨道周期的周期性变化,表明系统中存在第三天体,和BI CVn的情况一样,第三天体的存在可能对这两颗相接双星的形成起着重要的作用。同时还发现BS Cas和RT LMi的光变曲线都发生了明显的变化,表明子星上存在黑子的活动。 5.通过大量相接双星资料的分析发现:(1)超过50%的相接双星属于浅度相接双星;(2)光谱型越晚浅度相接双星所占得比例越大;(3)超过三分之二的浅度相接双星属于W次型。发现轨道周期长期增加和长期减小的浅度相接双星的相接度、周期、子星质量,质量比等没有相关性。
Other AbstractOvercontact binary is a kind of close binary where both components filling the critical Roche lobe and sharing a CCE(Common Convective Envelope). The degree of overcontact f is a physical quantity that describes how much the mass of the components fill the inner critical surface and the outer critical surface. Shallow-contact binary is a kind of system whose f is less than 20%. Shallow-contact binary is a bridge between the overcontact binary and the semi-detached binary. In this paper, some binaries were observed, analyzed. The shallow-contact binaries are studied statistically. The results are obtained as follow: 1. It is discovered that RV Psc and BI CVn are shallow-contact binaries with the period decreasing. Their degrees of overcontact and period decrease rates are 5.8% and 18.0%, -5.89x10-8days/year and -1.51 x10-7days/year, respectively. This indicated that the mass transfer from the primary to the secondary component. This suggests that they were formed from short-period detached binaries via a Case A mass transfer. As the shrinking of the Roche lobe continues (because of the decrease of the orbital period), the formation of a CCE will cause them evolve into normal overcontact binary stars. 2. We find AE Phe is a shallow-contact binary with the period increasing continuously at a rate of +5.50 x10-8days/year. The degree of overcontact of AE Phe is 14.6%. The long-term period increase may suggest that AE Phe is on the TRO-controlled stage of the evolutionary scheme. The long-term period increase, the shallow-contact configuration, and the astrophysical parameters of the binary system, all suggest that it is a shallow-contact binary on the thermal relaxation oscillation evolving into a detached binary. 3. It is found that DM Del is a semi-detached binary with a lobe-filling primary with period decrease rates -2.68 x10-7days/year. DM Del evolves into semi-detached configuration via AML and a Case A mass transfer occurs after the original more massive component filling its critical Roche lobe. The geometrical structure and the long-term period decrease suggest that DM Del may be a progenitor of overcontact binary or just in a broken-contact stage predicted by thermal relaxation oscillations. And DM Del will evolve into a shallow-contact binary with the period decreasing. 4. We find BS Cas and RT LMi are middle-contact binaries with the period decreasing continuously. Their degrees of overcontact and period decrease rates are 27.5% and 28.2%, -1.51 x10-7days/year and -1.64 x10-8days/year, respectively. The long-term orbital period decrease suggests that BS Cas and RT LMi are undergoing mass transfer from the primary component to the secondary one. With the mass transfers and accompanying angular momentum loss, the binaries will evolve into deeper contact configuration. 5. We find that more than 50% contact binaries belong to shallow-contact binaries; the later the spectral type, the more shallow-contact binaries; more than two thirds of shallow-contact binaries belong to W-type contact binaries.
Subject Area天文学
Pages133
Language中文
Document Type学位论文
Identifierhttp://ir.ynao.ac.cn/handle/114a53/5967
Collection双星与变星研究组
Recommended Citation
GB/T 7714
何家佳. 浅度相接双星的观测研究[D]. 北京. 中国科学院研究生院(云南天文台),2009.
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