Living Around Active Stars Proceedings IAU Symposium No. 328, 2016 D. Nandy, A. Valio & P. Petit, eds. c  International Astronomical Union 2017 doi:10.1017/S1743921317003854 The inﬂuence of eclipses in the stellar radio emission Caius Lucius Selhorst 1,2 and Adriana Valio 3 1 NAT - N´ ucleo de Astrof´ ısica Te´orica - Universidade Cruzeiro do Sul S˜ ao Paulo, SP, Brazil email: caiuslucius@gmail.com 2 IP&D - Universidade do Vale do Para´ ıba - UNIVAP S˜ ao Jos´ e dos Campos, SP, Brazil 3 CRAAM - Universidade Presbiteriana Mackenzie, S˜ ao Paulo, SP, Brazil Abstract. Here we simulate the shape of a planetary transit observed at radio wavelengths. The simulations use a light curve of the K4 star HAT-P-11 and its hot Jupiter companion as proxy. From the HAT-P-11 optical light curve, a prominent spot was identiﬁed (1.10 R P and 0.6 IC ). On the radio regime, the limb brighting of 30% was simulated by a quadratic function, and the active region was assumed to have the same size of the optical spot. Considering that the planet size is 6.35% of the the stellar radius, for the quiet star regions the transit depth is smaller than 0.5%, however, this value can increase to ∼ 2% when covering an active region with 5.0 times the quiet star brightness temperature. Keywords. Eclipses - Stars: activity - Radio Continnum: stars 1. Introduction Since the discovery of the ﬁrst exoplanets in the nineties, the number of conﬁrmed ones exceed 3500 at this time (http://exoplanet.eu). Part of this success can be addressed to dedicated projects like HARPS and Kepler. Some of these exoplanets can observed by the dimming of the light from the parent star during the planetary transit (e.g., Alonso et al. 2004). Besides planet detection, the transit can be used to detect spots on the stellar surface (Silva 2003) and estimate the stelar activity (Silva-Valio et al. 2010). Despite the great number of exoplanets, the observations are still restricted to the optical wavelengths range. Although recently, a transit observation was reported in X- ray (Poppenhaeger et al. 2013), with interesting results indicating that the hot Jupiters atmosphere can be broader in X-ray than the observed in the optical. In Selhorst et al. 2013, the authors considered the physical contributions of the plan- etary transits observations at radio frequencies. However, the attempts to detect the ex- oplanet radio emission were restricted to trying to observe the emission from the planet atmosphere, but, without success (e.g., Hallinan et al. 2013). Here, we present a simple model to estimate the inﬂuence of eclipses in the stellar radio emission based on the observed optical light curves. 2. Simulations To model the optical limb darkening observed in the stellar light curves, Silva 2003 used the following quadratic function: I (μ)/I (1) = 1 − w 1 (1 − μ) − w 2 (1 − μ) 2 , where μ is the cosine of the angle between the line of sight and the normal to the local stellar surface. 305 https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921317003854 Downloaded from https://www.cambridge.org/core. IP address: 44.197.234.82, on 13 Aug 2021 at 16:53:17, subject to the Cambridge Core terms of use, available at