When a planet transits in front of its host star, a fraction of its light is blocked, decreasing the observed flux from the star. The same is expected to occur when observing the stellar radio flux. However, at radio wavelengths, the planet also radiates, depending on its temperature, and thus modifies the transit depths. We explore this scenario simulating the radio lightcurves of transits of hot-Jupiters, Kepler-17b and WASP-12b, around solar-like stars. We calculated the bremsstrahlung radio emission at 17, 100, and 400 GHz originated from the star, considering a solar atmospheric model. The planetary radio emission was calculated modelling the planets in two scenarios: as a blackbody or with a dense and hot extended atmosphere. In both cases the planet radiates and contributes to the total radio flux. For a blackbody planet, the transit depth is in the order of 2-4% and it is independent of the radio frequency. Hot-Jupiters planets with atmospheres appear bigger and brighter in radio, thus having a larger contribution to the total flux of the system. Therefore, the transit depths are larger than in the case of blackbody planets, reaching up to 8% at 17 GHz. Also the transit depth is frequency-dependent. Moreover, the transit caused by the planet passing behind the star is deeper than when the planet transits in front of the star, being as large as 18% at 400GHz. In all cases, the contribution of the planetary radio emission to the observed flux is evident when the planet transits behind the star.

中文翻译：

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无线电波长下的行星凌日：热木星扩展大气层的二次日食

当一颗行星在其主恒星前方运行时，它的一小部分光被阻挡，从而减少了观察到的来自恒星的通量。在观测恒星无线电通量时，预计也会发生同样的情况。然而，在无线电波长下，这颗行星也会根据其温度进行辐射，从而改变凌日深度。我们探索了这种模拟热木星 Kepler-17b 和 WASP-12b 围绕类太阳恒星凌日的射电光曲线的场景。考虑到太阳大气模型，我们计算了源自恒星的 17、100 和 400 GHz 的轫致辐射射电辐射。行星无线电发射是在两种情况下对行星进行建模的：作为黑体或具有密集而炎热的大气层。在这两种情况下，行星都会辐射并贡献总无线电通量。对于黑体行星，传输深度约为 2-4%，与射频无关。有大气层的热木星行星在无线电中显得更大更亮，因此对系统总通量的贡献更大。因此，凌日深度大于黑体行星的情况，在 17 GHz 时可达 8%。此外，传输深度与频率有关。而且，行星从恒星后面经过造成的凌日比行星在恒星前面过境要深，在400GHz时高达18%。在所有情况下，当行星在恒星后面运行时，行星无线电发射对观测通量的贡献是显而易见的。因此对系统的总通量有更大的贡献。因此，凌日深度大于黑体行星的情况，在 17 GHz 时可达 8%。此外，传输深度与频率有关。而且，行星从恒星后面经过造成的凌日比行星在恒星前面过境的深度要深，在400GHz时可达18%。在所有情况下，当行星在恒星后面运行时，行星无线电发射对观测通量的贡献是显而易见的。因此对系统的总通量有更大的贡献。因此，凌日深度大于黑体行星的情况，在 17 GHz 时可达 8%。此外，传输深度与频率有关。而且，行星从恒星后面经过造成的凌日比行星在恒星前面过境的深度要深，在400GHz时可达18%。在所有情况下，当行星在恒星后面运行时，行星无线电发射对观测通量的贡献是显而易见的。在 400GHz 时高达 18%。在所有情况下，当行星在恒星后面运行时，行星无线电发射对观测通量的贡献是显而易见的。在 400GHz 时高达 18%。在所有情况下，当行星在恒星后面运行时，行星无线电发射对观测通量的贡献是显而易见的。