Searching for Structural Variability in Sgr A
Searching for Structural Variability in Sgr A
复制标题
DOI：
10.1002/asna.200385090
复制
发表时间：
2003-09
影响因子：
0.9
通讯作者：
Zhi-qiang Shen;M. Liang;K. Lo;M. Miyoshi
中科院分区：
文献类型：
--
作者：
Zhi-qiang Shen;M. Liang;K. Lo;M. Miyoshi
本文提出了一种模型拟合方法，用于估计描述VLBA观测到的SgrA*射电辐射的椭圆高斯模型的参数。通过在拟合幅度的同时(隐含地)使用幅度闭合关系，该程序可以最大限度地减少毫米波长VLBI测量中的校准误差，这对我们正在进行的搜索SGR A*结构可变性的努力至关重要。对7个历时的λ7mMVLBA观测的初步结果似乎表明，在7年的时间里(1994年-2001年)，至少有一个历元的源视结构有变化的迹象。由于VLBA南北方向的空间分辨率较差，在确定短轴时存在很大的不确定性，这些结果是提示性的，但并不是决定性的。这证明了在未来的λ7mmVLBA观测中增加NRAO GBT天线的必要性，这将使南北分辨率提高3倍。
A model fitting procedure for estimating the parameters of an elliptical Gaussian model that describes the radio emission of Sgr A* observed by the VLBA is presented. By (implicitly) using the amplitude closure relation while fitting the amplitude, the procedure can minimize the calibration errors in millimeter wavelength VLBI measurements, which are crucial to our ongoing effort to search for the structural variability in Sgr A*. The preliminary results from the application to seven-epoch λ7mm VLBA observations seem to show the sign of change to the source apparent structure in at least one epoch over the period of 7 years (1994–2001). Because of the large uncertainties in the determination of minor axis caused mainly by the poor spatial resolution along the north-south direction with the VLBA, these results are suggestive but not conclusive. This demonstrates the necessity of adding the NRAO GBT antenna to the future λ7mm VLBA observations, which can greatly improve the resolution in the north-south by a factor of 3.