频带4中uGMRT的极化约定
The Polarization Convention of the uGMRT in Band 4
摘要：
我们提出了一个实验，以了解极化公约采用的波段4（550- 900 MHz）的升级的巨型米波射电望远镜（uGMRT）。为此，我们在该波段对脉冲星B1702- 19进行了干涉测量和脉冲星模式观测，并将观测结果与用Lovell望远镜获得的已知Stokes $I$、$Q$、$U$、$V$廓线进行了比较。我们发现，从干涉测量和脉冲星模式的uGMRT得到的结果彼此一致。然而，尽管用uGMRT获得的斯托克斯$U$轮廓与用洛弗尔望远镜获得的轮廓相匹配，但斯托克斯$Q$和$V$却不匹配。这可以解释为，如果在该频带中的$X$和$Y$偶极子（从中导出$R$和$L$）被交换了w.r.t.国际天文学联合会公约。根据IEEE约定，交换使得uGMRT频带4的$RR^*$和$LL^*$分别为$LL^*$和$RR^*$。这意味着，如果我们需要将在uGMRT的频带4中获得的偏振测量与像Lovell、Parkes、甚大阵列等望远镜（所有望远镜都遵循IEEE用于定义右旋和左旋圆偏振的惯例）进行比较，则我们必须交换$RR^*$和$LL^*$，并且改变uGMRT数据的Stokes $Q$的符号。注意，这是uGMRT频带4的当前约定，并且一旦处理了偶极子的交换，将来可能会改变。一旦完成，将在另一份技术报告中通知。
英文摘要：
We present an experiment performed to understand the polarization convention adopted for band 4 (550--900 MHz) of the upgraded Giant Metrewave Radio Telescope (uGMRT). For that we observed the pulsar B1702--19 in this band, both in interferometry and pulsar modes, and compare the results with its already known Stokes $I$, $Q$, $U$, $V$ profiles obtained with the Lovell telescope. We find that the results obtained from interferometry and pulsar modes of the uGMRT agree with each other. However, although the Stokes $U$ profile obtained with the uGMRT match with that obtained by the Lovell telescope, Stokes $Q$ and $V$ do not. This can be explained if the $X$ and $Y$ dipoles in this band, from which $R$ and $L$ are derived, are swapped w.r.t. the IAU convention. The swapping makes $RR^*$ and $LL^*$ of the uGMRT band 4 to be $LL^*$ and $RR^*$ respectively according to the IEEE convention. This implies that if we need to compare polarization measurements obtained in band 4 of the uGMRT with telescopes like Lovell, Parkes, Very Large Array etc. (all follow IEEE convention for defining right and left hand circular polarization), we must interchange $RR^*$ and $LL^*$, and change the sign of Stokes $Q$ for the uGMRT data. Note that this is the current convention for uGMRT band 4, and is likely to change in future once the swapping of the dipoles is taken care of. Once it is done, it will be notified in another technical report.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
