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題名 | 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 the Timing Properties for the Accretion-powered Millisecond Pulsar SAX J1808.4-3658 |
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作者 | 蔡兆陽; 周翊; | 書刊名 | 臺北天文館學報 |
卷期 | 4 民95.12 |
頁次 | 頁9-16 |
分類號 | 323.85 |
關鍵詞 | 低質量X光雙星系統; 吸積驅動毫秒波霎; 千赫茲準週期震盪; 爆發準週期震盪; Low mass X-ray binary; Accretion-powered millisecond pulsar; Kilo-hertz quasi periodic oscillation; Burst quasi periodic oscillation; |
語文 | 中文(Chinese) |
中文摘要 | 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 J1808.4-3658,利用它在1998、2000、2002與2005年爆發時之RXTE的觀測資料做長時間之監測,以求得軌道週期的演化,以及找尋吸積力矩(Accretion torque)。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(projected radius) 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 yr-1,這和典型低質量X光雙星的軌道週期變化率10-7~10-8 yr-1一致,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。 |
英文摘要 | 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 projected radius = 62.811(2) lt-ms from 2002 data. For the 1998 outburst, we get consistent projected radius of = 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) × 10-8yr-1. No pulsation is significant detected 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. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。