利用參數化的方法研究低質量X光雙星系統 X1916-053 的X光dip之性質;Parameterization studies of the properties of the X-ray dips for Low-Mass X-ray binary X1916-053

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/6070

Title:	利用參數化的方法研究低質量X光雙星系統 X1916-053 的X光dip之性質;Parameterization studies of the properties of the X-ray dips for Low-Mass X-ray binary X1916-053
Authors:	胡欽評;Chin-Ping Hu
Contributors:	天文研究所
Keywords:	雙星;變星;低質量X光雙星系統;Variable Star;Binary;X-ray Binary
Date:	2005-06-22
Issue Date:	2009-09-22 10:12:46 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	X1916-053 是一個由中子星和白矮星組成的極緊密低質量X光雙星系統(ultra-compact Low Mass X-ray Binary)。它的X光``dip'的週期以及光學波段的光變週期只有些微的差距。我們利用了新的方法定義出dip的一些參數以利於對dip的特性做有系統研究。藉由這些研究，我們能更進一步了解雙星系統和吸積盤 (accretion disk) 的性質。在RXTE 1998年的觀測中，dip的寬度有明顯的4.87天的週期性變化，這個變化極可能是吸積盤做盤面進動(nodal precession)的週期。吸積盤的交點進動週期和雙星的軌道週期的``拍頻(beat frequency)'在1996年觀測中可以偵測得到。由``負超駝峰(negative superhump)'的模型加上吸積盤半徑是1:3共振半徑的假設，我們可以估計出雙星的質量比是0.045。這個值比由``超駝峰(positive superhump)'模型或是伴星充滿洛希瓣的預測稍微大了一些，但是仍在同一個數量級的合理範圍。結合了24年來的X光觀測資料，我們發現了雙星軌道週期對時間的一次微分項$dot{P}_{orb}/P_{orb}=(1.62 pm 0.34) imes 10^{-7} yr^{-1} $並且為X光dip建立一個二階的星曆表(ephemeris)。我們觀測到的軌道週期時變率與雙星演化的典型模型推導出來的不吻合。然而，由``輻射驅動 (radiation driven)'雙星演化的模型似乎可以解釋我們觀測到的量。但是由這個模型預測的大量質量外流卻從來沒有觀測到。從primary dips 和 secondary dips 的相位統計，我們得知 primary dip 比 secondary dip還要穩定。這個結果讓我們知道造成 primary dip 的隆起結構是位於吸積盤的外圍而不是在中間的環狀結構上。 X 1916-053 is an ultra-compact Low Mass X-ray Binary (LMXB) composed of a neutron star and a white dwarf. The period of recurrent X-ray dips and optical modulations are slightly and significantly different with each other. We have developed new methods to parameterize the dip to systematically study its variation to further understand the binary and accretion disk behavior. A 4.87 days periodic variation of the dip width, probably due to the nodal precession of the accretion disk, is clearly seen in the RXTE 1998 observations. The signal of the beat frequence of disk nodal precession and the orbital period is marginally detected in the RXTE 1996 data with epoch folding period search method. From the negative superhump model, the mass ratio can be estimated of $q=0.045$ with 1:3 resonance disk radius, which is larger than the mass ratio predicted by the superhump model or Roche-lobe filling secondary but in the same order. Combined with more than 24 years' historical data, we found an orbital period derivative $dot{P}_{orb}/P_{orb}=(1.62 pm 0.34) imes 10^{-7} yr^{-1}$ and established a quadratic ephemeris for the X-ray dips. The period derivative seems inconsistent with the prediction of standard model of orbital evolution. On the other hand, the radiation driven model may be proper to interpret the period derivative although the large mass outflow predicted by this model has never been observed in this system. From the statistic of dip phase of primary and secondary dips, we concluded that the primary dips are more stable than the secondary dips, which implies that the bulge which cause the primary dips should be on the outer edge of accretion disk instead of in the $1/2$ ring.
Appears in Collections:	[Graduate Institute of Astronomy] Electronic Thesis & Dissertation

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