本論文的目的是利用 4U 1323-62 和 4U 1254-69 光陷現象來估計其軌道週期演化。這兩個雙星系統有長達 26 年的X光觀測資料，我們使用了 ASCA、BeppoSAX、Chandra、EXOSAT、RXTE、Suzaku、XMM-Newton 觀測資料。我們參考 Hu et al. (2008) 中所提到的方法來決定光陷時間中點，並利用 O-C 方法估算軌道週期和軌道週期變化。
我們分析 4U 1323-62 和 4U 1254-69 的光陷相位演化並更新它們從 1980 年代到 2010 年代的軌道星曆表。4U 1323-62 和 4U 1254-69 更新後的軌道週期分別是 2.94191579(41) 小時和 3.9333372(15) 小時，但它們的軌道週期的變化率並不明顯，|Ṗ_orb/P_orb | 不超過 8.6 ⨉ 10^-8 yr^-1 和 3.1 × 10^-7 yr^-1 2sigma 上限)。在假設雙星系統質量守恆的情況下，我們可以從 |Ṗ_orb/P_orb | 推測出它們的 2sigma 吸積率上限分別為 2.8 × 10^-8 M_⊙/year 和 1.7 × 10^-7 M_⊙/year。此外，我們並從 Balucińska-church et al. (2009) 對於 4U 1323-62 所得到的光度 1 - 5.2 × 10^36 erg/s 和 Iaria et al. (2007) 對 4U 1254-69 所得到的光度 1.2 × 10^37 erg/s 推導出吸積率，其數值都遠小於我們由軌道週期所評估的吸積率上限。;4U 1323-62 and 4U 1254-69 are low mass X-ray binaries exhibiting X-ray burst and periodic X-ray dips. Both systems consist of a neutron star as accretor and a Roche lobe filled late type star as donor. They were discovered in 1970s. The dip period of 4U 1323-62 was first detected by Parmar et al. (1989) with a value of 2.932 ± 0.005 hr. For 4U 1254-69, Courvoisier et al. (1986) discovered a 3.99 ± 0.15 hr dipping period.
The purpose of this thesis is to study the orbital period evolutions using properties of dips for 4U 1323-62 and 4U 1254-69. The time span of X-ray observations of both sources are about 26 years performed by EXOSAT, ASCA, BeppoSAX, RXTE, Chandra, XMM-Newton and Suzaku. We used method proposed by Hu et al. (2008) to estimate dip center time and adopted Observed - Calculate method to measure the orbital periods and their derivatives.
We analyzed the dip phase evolutions of 4U 1323-62 and 4U 1254-69 and updated the orbital ephemeris of them from 1980s to 2010s. The orbital periods are refined as 2.94191579(41) hr for 4U 1323-62 and 3.9333372(15) hr for 4U 1254-69. No significant orbital period derivatives is detected for both sources with 2σ upper limits of |Ṗ_orb/P_orb | = 8.6 ⨉ 10^-8 yr^-1 and 3.1 × 10^-7 yr^-1 for 4U 1323-62 and 4U 1254-69, respectively. Under the assumption of conservation of the mass of the binary system, the mass accretion rates are no more than 2.8 × 10^-8 M_⊙/year 和 1.7 × 10^-7 M_⊙/year for 4U 1323-62 and 4U 1254-69, respectively (2σ upper limits). The derived accretion rates from the X-ray luminosities, 1 - 5.2 × 10^36 erg/s (Balucińska-church et al. 2009) for 4U 1323-62 and 1.2 × 10^37 erg/s (Iaria et al. 2007) for 4U 1254-69, are well below the corresponding upper limits from the evolutions of their orbital periods.
