4U2127+119 是一個低質量 X 光雙星系統 (low mass X-ray binary, LMXB) ，由一顆中子星 (neutron star) 及一顆殼層剝落的巨星 (stripped giant) 。hyperref[Aurière1984]{Aurière et al. (1984)} 首次透過可見光波段對 4U2127+119 進行觀測，hyperref[Ilovaisky1993]{Ilovaisky et al. (1993)} 測量出 4U2127+119 的軌道週期 $P_{orb} = 0.713014(1)$ 天並建立線性星曆表 (linear ephemeris) ，hyperref[Homer1998]{Homer \& Charles (1998)} 更新觀測資料，得出軌道週期變化率 $\dot{P}/{P} \sim 9 \times 10^{-7} (yr^{-1})$ 並建立二階星曆表 (quadratic ephemeris) 。

本論文的目的是透過 4U2127+119 的光陷 (dip) 現象推算其軌道週期演化，進一步了解具吸積盤暈 (Accretion Disc Corona, ADC) 結構之低質量 X 光雙星系統的演化過程。從 1977 到 2024 年共 47 年的 X 光觀測，包括 ASCA 、 BeppoSAX 、 Chandra 、 EXOSAT 、 Ginga 、 HEAO-1 、 MAXI 、 RXTE 、 XMM-Newton 的觀測資料，我們將光陷作為相位基準點 (fiducial point) ，首先利用多重正弦擬合 (multi-sinusoidal fitting) 找出光陷的相位位置，再以蒙地卡羅模擬 (Monte Carlo simulation) 求出光陷相位的誤差，最終根據線性及二次曲線模型求得軌道參數。

經由新的觀測資料，從線性模型中得出軌道週期為 $0.71302140(32)$ 天，在二階模型中，得到軌道週期變化率為 $\dot{P}/P$ 為 $(1.42 \pm 1.01) \times 10^{-7}(yr^{-1})$ ，表示我們並未測到明顯軌道週期變化率，其 $2 \sigma$ 上限為 $2.02 \times 10^{-7}(yr^{-1})$。具有吸積盤暈結構的低質量 X 光雙星系統中，其內部光度 (intrinsic luminosity, $L_{int}$) 會接近愛丁頓光度 (Eddington luminosity, $L_{Edd}$)，藉由分析不同內部光度與軌道週期變化率的關係， 4U2127+119 傾向於質量比較低的結果( $q$ 介於 0.06 到 0.19 )，與 \hyperref[van Zyl2004]{van Zyl et al. (2004)} 得出的結果相符。

4U2127+119 is a low mass X-ray binary (LMXB) system composed of a neutron star and a stripped giant. \hyperref[Aurière1984]{Aurière et al. (1984)} first investigated its orbital period evolution by using optical observations. \hyperref[Ilovaisky1993]{Ilovaisky et al. (1993)} measured the orbital period of 4U2127+119 to be $P_{orb} = 0.713014(1)$ days and established a linear ephemeris. \hyperref[Homer1998]{Homer \& Charles (1998)} updated the observation data, derived an orbital period derivative of
$\dot{P}/{P} \sim 9 \times 10^{-7} (yr^{-1})$ and constructed a quadratic ephemeris.

The purpose of this study is to estimate the orbital period evolution of 4U2127+119 through its X-ray dip, to further understand the evolution process of LMXB systems with an accretion disc corona (ADC) structure. We analyzed 47 years of X-ray observations from 1977 to 2024, including data from ASCA, BeppoSAX, Chandra, EXOSAT, Ginga, HEAO-1, MAXI, RXTE, and XMM-Newton. Selecting X-ray dip as a fiducial point, we applied multi-sinusoidal fitting to determine the phase. Subsequently, we used Monte Carlo simulation to estimate the error. Finally, orbital parameters were derived based on linear and quadratic models.

With more observation data, the linear model yielded an orbital period of $0.71302140(32)$ days. For the quadratic model, we obtained an orbital period derivative $\dot{P}/P=(1.42\pm1.01) \times 10^{-7}(yr^{-1})$, indicating that we did not detect a significant orbital period change, with $2\sigma$ upper limit of $2.02 \times 10^{-7}(yr^{-1})$. In LMXB systems with an ADC structure, the intrinsic luminosity $L_{int}$ is believed to approach the Eddington luminosity $L_{Edd}$ . By classifying the relationship between different intrinsic luminosities and the orbital period derivative, we concluded that tends to be a lower mass ratio(q ranging from 0.06 to 0.19), consistent with the results obtained by \hyperref[van Zyl2004]{van Zyl et al. (2004)}.

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