Study of Orbital and Pulsation Properties of Accretion-Powered Millisecond Pulsar XTE J1814-338

• Main Authors: Yi-Ying Chung, 鍾怡音
• Other Authors: 周翊
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/49982019101091076482

碩士 === 國立中央大學 === 天文研究所 === 95 === The fifth known accretion-powered millisecond pulsar (AMP) XTE J1814-338 was discovered by Rossi X-ray Timing Explorer (RXTE) in June 2003 during its outburst. In this thesis, we study its orbital and pulsation properties based on the observations by RXTE. It is believed that emission on the neutron star surface is mainly composed of a Comptonized and blackbody components, and pulsar pulsations reflect the emission properties. Before we investigate pulsation properties, it is essential to determine fine orbital and spin parameters in order to resolve pulse structures. We first carried out pulse arrival-time analysis based on the non-burst events within energy range 2-10 keV using differential correction technique, and derived barycentric pulsar frequency $ u = $314.35610897(9) Hz, orbital period 4.27464545(7) hr, and 390.623(2) lt-ms projected radius. Our analysis of pulsar phase evolution in the initial 23 days shows that the pulsar has a spin frequency derivative $dot u = -4.1(2) imes 10^{-13} m Hz s^{-1}$, and a second frequency derivative $ddot u = 2.9(1) imes 10^{-19} m Hz s^{-2}$. After folding RXTE/PCA and HEXTE photon events within 2 - 50 keV using the best orbital and spin ephemerids obtained in the first part of analysis, we were able to find the pulses show energy-dependent phase delays, where soft energy pulses lag high energy pulses for up to $sim$ 50 $mu m s$ between 2-10 keV, which is common in known AMPs; in addition, we also found hard pulses lag soft ones between 10-50 keV. While the soft lags are mainly caused by Doppler boosting effect that distorts the Comptonizing pulse component with fan-like emission pattern, we propose that "hard lags" between 10 - 50 keV are likely attributed to Compton upscattering by the hot electron gas in accretion shock region.