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Transmission spectroscopy has been proven to be the most powerful technique in detecting and characterizing atmospheres of exoplanets. So far, mostly ground and space-based multi-band transit photometry have been used to retrieve the exoplanets' broadband transmission spectra. An alternative technique has been proposed for retrieving the broadband transmission spectra using chromatic Rossiter-McLaughlin observation. This technique has been used only once for exoplanet HD189733b using HARPS observation in the visible range. I will present the result we obtained from our new CARMENES spectroscopic observation (both VIS and NIR arms) during one transit of HD189733b. We found a strong agreement between the retrieved transmission spectra from CARMENES and HARPS in the overlapping wavelength range. By combining HARPS and CARMENES VIS and NIR observations, for the first time, we obtained the widest broadband transmission spectra from ground-based observations which is comparable to the one obtained from HST and Spitzer observations. We found a clear signature of haze in the atmosphere of HD189733b as indicated by the presence of Rayleigh scattering slope in transmission spectra, however our result suggested much hazier atmosphere in comparison to the previous studies. Moreover, we demonstrated how a single transit CARMENES observation could provide important information about the stellar active regions’ properties (such as their temperature contrast), which are crucial information in order to mitigate the stellar activity effect on the retrieved transmission spectra.

Measuring the color dependent Rossiter-McLaughlin effect from 0.38 to 1.71 micrometer using ground based observations