Cohen Offr, Moschou Sofia-Paraskevi, Glocer Alex, Sokolov Igor V, Mazeh Tsevi, Drake Jeremy J, Garraffo C, Alvarado-GÓmez J D
Lowell Center for Space Science and Technology, University of Massachusetts Lowell 600 Suffolk St., Lowell, MA 01854, USA.
Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, Massachusetts, USA.
Astron J. 2018 Nov;156(5). doi: 10.3847/1538-3881/aae1f2. Epub 2018 Oct 17.
The search for exoplanets in the radio bands has been focused on detecting radio emissions produced by the interaction between magnetized planets and the stellar wind (auroral emission). Here we introduce a new tool, which is part of our MHD stellar corona model, to predict the ambient coronal radio emission and its modulations induced by a close planet. For simplicity, the present work assumes that the exoplanet is stationary in the frame rotating with the stellar rotation. We explore the radio flux modulations using a limited parameter space of idealized cases by changing the magnitude of the planetary field, its polarity, the planetary orbital separation, and the strength of the stellar field. We find that the modulations induced by the planet could be significant and observable in the case of hot Jupiter planets - above 100% modulation with respect to the ambient flux in the 10 - 100 range in some cases, and 2-10% in the frequency bands above 250 for some cases. Thus, our work indicates that radio signature of exoplanets might not be limited to low-frequency radio range. We find that the intensity modulations are sensitive to the planetary magnetic field polarity for short-orbit planets, and to the stellar magnetic field strength for all cases. The new radio tool, when applied to real systems, could provide predictions for the frequency range at which the modulations can be observed by current facilities.
在射电波段寻找系外行星一直聚焦于探测磁化行星与恒星风相互作用产生的射电辐射（极光辐射）。在此，我们引入一种新工具，它是我们磁流体动力学恒星日冕模型的一部分，用于预测由近距离行星引起的日冕环境射电辐射及其调制。为简单起见，本研究假设系外行星在随恒星自转的参考系中是静止的。我们通过改变行星磁场强度、其极性、行星轨道间距以及恒星磁场强度，在理想化情况的有限参数空间内探索射电流量调制。我们发现，对于热木星行星，行星引起的调制可能很显著且可观测到——在某些情况下，在10 - 100范围内相对于环境流量的调制超过100%，在某些情况下，在高于250的频段中为2 - 10%。因此，我们的研究表明系外行星的射电特征可能不限于低频射电范围。我们发现，强度调制对于短轨道行星的行星磁场极性以及所有情况下的恒星磁场强度都很敏感。当应用于实际系统时，这种新的射电工具可以为当前设施能够观测到调制的频率范围提供预测。
