We report the results of the Jansky Very Large Array (JVLA) observation of five massive protostars at 6 and 22.2 GHz. The aim of the study was to compare their current fluxes and positions with previous observations to search for evidence of variability. Most of the observed sources present the morphologies of a thermal core, hosting the protostar and exhibiting no proper motion, and associated non-thermal radio lobes that are characterised by proper motions and located away from the thermal core. Some of the protostars drive jets whose lobes have dissimilar displacement vectors, implying precession of the jets or the presence of multiple jet drivers. The jets of the protostars were found to have proper motions that lie in the range 170≤ v ≤650 kms−1, and precessions of periods 40≤ p ≤50 years and angles 2≤ α ≤10◦, assuming that their velocities v =500 kms−1. The core of one of the sources, S255 NIRS 3, which was in outburst at the time of our observations, showed a significant change in flux compared to the other sources. Its spectral index decreased during the outburst, consistent with the model of an expanding gas bubble. Modelling the emission of the outburst as that of a new non-thermal lobe that is emerging from a thermal core whose emission enshrouds that of the lobe also has the potential to account for the increase in flux and a decrease in the spectral index of the source’s outburst.

中文翻译：

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大质量原恒星射电连续发射的多历元研究

我们报告了对 6 GHz 和 22.2 GHz 的五颗大质量原恒星的 Jansky 甚大阵列 (JVLA) 观测结果。该研究的目的是将它们当前的通量和位置与以前的观察结果进行比较，以寻找变异的证据。大多数观测到的源呈现热核的形态，其中包含原恒星但没有自行运动，以及相关的非热射电瓣，其特征是自行运动并远离热核。一些原恒星驱动喷流，其叶瓣具有不同的位移矢量，这意味着喷流的进动或存在多个喷流驱动器。原恒星的喷流被发现在 170≤ v ≤650 kms−1 范围内有自行，进动周期为 40≤ p ≤50 年，角度 2≤ α ≤10°，假设它们的速度 v = 500 kms−1。其中一个源 S255 NIRS 3 的核心在我们观察时处于爆发状态，与其他源相比，其通量发生了显着变化。它的光谱指数在爆发期间下降，与膨胀的气泡模型一致。将爆发的发射建模为从热核中出现的新的非热瓣的发射，其发射覆盖了瓣的发射也有可能解释通量的增加和源的光谱指数的下降爆发。与膨胀气泡模型一致。将爆发的发射建模为从热核中出现的新的非热瓣的发射，其发射覆盖了瓣的发射也有可能解释通量的增加和源的光谱指数的下降爆发。与膨胀气泡模型一致。将爆发的发射建模为从热核中出现的新的非热瓣的发射，其发射覆盖了瓣的发射也有可能解释通量的增加和源的光谱指数的下降爆发。