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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/6096

    Title: 長期監測吸積驅動毫秒波霎SAX J1808.4-3658之時變性質;Long-term monitoring for timing properties of the accretion-powered millisecond pulsar SAX J1808.4-3658
    Authors: 蔡兆陽;Chao-Yang Tsai
    Contributors: 天文研究所
    Keywords: 時變性質;波霎;毫秒波霎;SAX J1808.4-3658;millisecond pulsar;pulsar;RXTE
    Date: 2006-06-21
    Issue Date: 2009-09-22 10:13:09 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 本論文使用1998-2005年RXTE的觀測數據, 針對第一個被發現的吸積驅動毫秒波霎(Accretion-powered millisecond pulsar) SAX J1808.43658, 做長時間之監測以求得軌道週期的演化,以及找尋吸積力矩(Accretion torque)。 SAX J1808.4-3658是個低質量X光雙星系統,在1996年爆發時才被BeppoSAX望遠鏡發現, 不過直到1998年再度爆發時,才被偵測有波霎的現象(RXTE望遠鏡觀測)。此系統距離地球約2.5kpc, 自轉頻率401Hz,軌道週期2小時。除了1998年外,2000年、2002年與2005年此星體約每隔2年爆發一次, 此三次爆發RXTE望遠鏡都做了觀測。 為了求出這幾年最好的自轉與軌道參數,我們先利用了軌道運動造成的都卜勒效應求出參數初步值, 再利用此參數做相位分析(我們把光子抵達時間對一個考慮中子星自轉與軌道的變動頻率做疊合來得到相位)以獲得最佳的參數值, 我們在1998年與2002年測得一致的投影軌道半徑(project radius) asini 分別是 62.814(2)lt-ms 與 62.811(2)lt-ms , 除此之外我們也測量到這兩年的軌道週期,分別是 7249.1558(9)s 與 7249.158(1)s , 因此我們測量到此系統的軌道週期變化率(Orbital period derivative)為 (7 ± 4)× 10^{-8} 1/yr , 這和典型低質量X光雙星的軌道週期變化率 10^{-7}~ 10^{-8} 1/yr 一致,不過2000年與2005年的爆發因為都是迷你爆發, 使我們無法偵測到明顯的脈衝(pulsation)現象,因此無法得到更精確的軌道週期變化率, 有趣的是我們在1998年測到自轉變慢的吸積力矩 -3.15(1)× 10^-12 Hz/s , 這個值比典型理論值( ~10^-14 Hz/s )大兩個數量級。 We present our analysis results of the spin and orbital properties of the first discovered accretion-powered millisecond pulsar SAX J1808.4-3658 observed by Rossi X-ray Timing Explorer (RXTE) during its 1998 and 2002 outbursts. The event arrival times are initially folded with an ephemeris consist of the neutron star spin frequency evolution plus the effect from the circular orbital motion and the parameters are then further refined according to the variation of the pulse phase. We obtain the binary barycenter neutron star spin frequency of ν=400.975210324(2)Hz , the orbital period of Porb = 7249.158(1)s and the project radius asini = 62.811(2)lt-ms from 2002 data. For the 1998 outburst, we get consistent project radius of asini = 62.814(2)lt-ms but significantly different orbital period (Porb = 7249.1558(9)s ), which indicates that the orbital period derivative is ~ (7 ± 4) × 10-8 1/yr. No pulsation is able to significant detect for 2000 and 2005 outbursts due to their low fluxes. In addition, the pulse phase variation of 1998 outburst shows a large spin-down rate of -3.15(1) × 10^-12 Hz s^-1, about a factor of 100 larger than the theoretical expectation value (~10^-14 Hz s^-1), whereas no clear spin frequency derivative during 2002 outburst.
    Appears in Collections:[天文研究所] 博碩士論文

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