Ynogk: a new public code for calculating null geodesics in the kerr spacetime
Ynogk: a new public code for calculating null geodesics in the kerr spacetime
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DOI：
10.1088/0067-0049/207/1/6
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发表时间：
2013-05
影响因子：
8.7
通讯作者：
Xiao-lin Yang;Jian-cheng Wang
中科院分区：
文献类型：
--
作者：
Xiao-lin Yang;Jian-cheng Wang
在Dexter和Agol工作的基础上，我们提出了一个新的公开代码，用于快速计算Kerr时空中的零测地线。使用维尔斯特拉斯和雅可比的椭圆函数，我们表示所有的坐标和仿射参数的解析和数值函数的参数p，这是一个积分值沿着测地线。这是我们的代码和以前类似代码的主要区别。这种处理的优点是，关于转折点的信息不需要由用户预先指定，并且许多应用，例如成像、线轮廓的计算和反射器-发射器问题，成为寻根问题。所有的椭圆积分计算卡尔森的椭圆积分方法在Dexter & Agol，这保证了我们的代码的快速计算速度。Cunningham和Barnham给出的计算运动常数的公式得到了推广，它使人们能够容易地处理发射者或观察者与中心紧凑物体有任意距离和相对于中心紧凑物体的运动状态的情况。代码的验证已经通过文献中玩具问题的应用程序进行了广泛的测试。FORTRAN源代码可以从我们的网站http://www1.ynao.ac.cn/~yangxl/yxl.html上免费下载。
Following the work of Dexter & Agol, we present a new public code for the fast calculation of null geodesics in the Kerr spacetime. Using Weierstrass's and Jacobi's elliptic functions, we express all coordinates and affine parameters as analytical and numerical functions of a parameter p, which is an integral value along the geodesic. This is the main difference between our code and previous similar ones. The advantage of this treatment is that the information about the turning points does not need to be specified in advance by the user, and many applications such as imaging, the calculation of line profiles, and the observer-emitter problem, become root-finding problems. All elliptic integrations are computed by Carlson's elliptic integral method as in Dexter & Agol, which guarantees the fast computational speed of our code. The formulae to compute the constants of motion given by Cunningham & Bardeen have been extended, which allow one to readily handle situations in which the emitter or the observer has an arbitrary distance from, and motion state with respect to, the central compact object. The validation of the code has been extensively tested through applications to toy problems from the literature. The source FORTRAN code is freely available for download on our Web site http://www1.ynao.ac.cn/~yangxl/yxl.html.