基于反射信号提取的双星系统轨道估算  

A Method of Estimating the Orbit of a Binary-Star System from Extracted Reflected Signals

作　　者：高扬[1,2] 周建锋[1,2] 

机构地区：[1]清华大学工程物理系天体物理中心,北京100084 [2]粒子技术与辐射成像教育部重点实验室(清华大学),北京100084

出　　处：《天文研究与技术》2015年第1期1-8,共8页Astronomical Research & Technology

基　　金：国家自然科学基金(11173038;11373025);清华大学自主科研计划(20111081102)资助

摘　　要：在观测双星系统时,接收的信号包含伴星反射成分。反射信号的时延可以给出伴星的位置、运动等信息,提取反射信号可以实现双星系统的轨道估算。利用相关函数,可实现对反射信号的提取,但由于双星的相对运动,直接对接收信号进行自相关运算不能提取反射信号。提出了一种基于对接收信号在时域做变换的方法,计算接收信号与变换后信号的互相关函数,可以解决运动情形下反射信号的提取。利用MATLAB对具体的情形进行了模拟,成功地提取了反射信号,验证了该方法的有效性。Received signals from a binary-star system include signals reflected by the companion star. The time delay of reflected signals is related to the position and velocity of the companion star, so that the reflected signals after being extracted can be used to estimate the orbit of the binary-star system. In principle reflected signals can be extracted from the Auto-Correlation Function （ACF） of a received-signal sequence. However, a straightforward extraction is out of reach because of the relative motion within a binary-star system. In this paper we propose a method based on mapping the received signals in the time domain to those in a time-delay domain. Reflected signals can be extracted by calculating cross-correlation functions between raw received signals and signals in the time-delay domain after the mapping. We search for the peak value of cross- correlation coefficients within the space of parameters describing the binary-system orbit. The peak value is related to the values of the orbital elements. This allows system. We have successfully tested the method through finding the orbital-parameter values of a binary-star MATLAB simulations. Our simulations are for an X- ray binary system with an edge-on orbital plane, X-ray binary systems are usually rather luminous, which makes our method more easily applicable. There are 4 parameters needed to describe the elliptical-orbit motion of an X-ray binary system. These are the semi-axis, the eccentricity, the area swept per unit time by the line section from the centroid to the companion, and the initial polar angle of the companion. We finally discuss the influence of the reflection coefficient on the effectiveness of the method. We expect that our method is more effective for X-ray binary systems whose accretion processes are via Roche-lobe overflows than for other cases. This is based on some simple estimates and a case study of the X-ray binary system GRS1915＋105.

关 键 词：双星 时延估计 相关函数 参数空间 

分 类 号：P1[天文地球—天文学]