Exoplanets are everywhere in the Galaxy. Yet, we know so little about them. To unveil their properties, I study their atmospheres.
My current research focuses on hot gas giant exoplanets. I observe their atmospheres with the most sensitive ground-based high dispersion Echelle spectrographs, and with the Hubble Space Telescope and the James Webb Space Telescope from space. I also model their atmospheric structure, creating synthetic spectra that I compare with observaions. In this way, I determine the properties of observed planets including temperature profile, abundances of elements, cloudiness and winds.
As of November 2020 I am eployed at the Osservatorio Astrofisico di Arcetri. Here, I carry out my research and I take action to build an inclusive and diverse work environment, which I consider key to perform excellent science.
KELT-9 b (4,000 K) is strongly irradiated by its A0-type stellar host (10,000 K). It's atmosphere is so hot that neutral iron is abundant in gas phase. I and my collaborators have identified iron lines in the dayside of the planet thanks to the high spectral resolution of HARPS-N. We were the first to show that, in ultra-hot Jupiters, iron acts like ozone on Earth, absorbing stellar light and heating the upper atmospheric layers.
Building on our previous detection of neutral iron (see box above), my collaborators and I designed an innovative method to look for variations with phase in the intensity and Doppler-shift of neutral iron lines. We found results that confirm 3D models of climate of the hottest planets: a symmetric line intensity around the point closest to the star, likely indicative of a symmetric thermal structure, and winds flowing directly from the day-side to the night-side. The lack of an eastward jet likely indicates that the planet's magnetic field is strongly interacting with its ionosphere!
The detailed shape of individually resolved spectral lines from gases in a planet atmosphere teaches reveals its properties. In this work, we introduce the Multi-nested Eta Retrieval Code (MERC), which determines atmospheric winds in the upper atmosphere of hot planets based on their sodium doublet lines. We find that strong updrafts of 40 km s$^{-1}$ blow material from the lower towards the upper atmosphere.
I and my collaborators have designed a new method to establish whether an atmopsphere is cloudy or not. This method removes the need to go to space to perform this measurement, by comparing the strength of lines belonging to different spectral bands of the same molecular species. We can finally do cloud-spotting in exoplanets with more affordable observations!
Space telescopes and ground-based echelle spectrographs are very different instruments, and probe different part of exoplanet atmosphere.In this paper, I present the $^\pi \eta$ framework to simultaneously model both kinds of data. I and my collaborators show the power of this approach, by measuring clouds and water in the lower part of the atmosphere (with the Hubble Space Telescope), and sodium and a thermospheric inversion in the upper part of the atmosphere (with HARPS-N)
If you are interested in my science, or the research activities in my institution, feel free to contact me.