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Planetary transits with the ALMA radio interferometer

Grant number: 13/21523-1
Support type:Regular Research Grants - Publications - Scientific article
Duration: November 01, 2013 - April 30, 2014
Field of knowledge:Physical Sciences and Mathematics - Astronomy
Principal Investigator:Caius Lucius Selhorst
Grantee:Caius Lucius Selhorst
Home Institution: Instituto de Pesquisa e Desenvolvimento (IP&D). Universidade do Vale do Paraíba (UNIVAP). São José dos Campos , SP, Brazil


Planetary transits are commonly observed at visible wavelengths. Here we investigate the shape of a planetary transit observed at radio wavelengths. Solar maps at 17 GHz are used as a proxy for the stellar eclipse by several sizes of planets from Super-Earths to Hot Jupiters. The relative depth at mid transit is the same as observed at visible wavelengths, but the limb brightening of the stellar disk at 17 GHz is clearly seen in the shape of the transit light curve. Moreover, when the planet occults an active region the depth of the transit decreases even further, depending on the brightness of the active region relative to the surrounding disk. For intense active region, with 50 times the brightness temperature of the surrounding disk, the decrease can supersede the unperturbed transit depth depending on the size of the eclipsing planet. For a Super-Earth (Rp = 0.02Rs) crossing, the decrease in intensity is 0.04%, increasing to 0.86% in the case when a strong active region is present. On the other hand, for a hot Jupiter with Rp = 0.17Rs, the unperturbed transit depth is 3% increasing to 4.7% when covering this strong active region. This kind of behavior can be verified with observation of planetary transits with the ALMA radio interferometer. (AU)