Seminario: presentazione tesi dottorato di G. Cracchiolo (UNIPA), Aula ore 15

When:
6 March 2023 @ 15:30 – 17:00
2023-03-06T15:30:00+01:00
2023-03-06T17:00:00+01:00

Google meet: https://meet.google.com/sxz-cctp-tsc

Speaker: Gianluca Cracchiolo (UNIPA)

Title: Mitigation of the impact of stellar activity on observations of transiting planets

Abstract: In the thesis I devolop different methods to correct the planetary transmission spectra for the effect of unocculted stellar spots. The methods are based on stellar activity models of increasing complexity, from models of spotted stars assuming a uniform stellar emission to models including the limb darkening effect. The correction strategies are developed for low-resolution observations from space and applied to simulations of observations with Ariel, the future space mission devoted to the observation of about 1000 exoatmospheres. These techniques are applied to the transit observation of the Super-Earth LHS 1140 b of December 2017, acquired with the WFC3/HST. The analysis shows that the out-of transit stellar spectrum can be fitted with a model of active star with a photospheric temperature of 3219 K and a spot distribution 400 K cooler and covering a fraction of 45-60% of the stellar disk, or with a model of quiet but cooler star (2916 K). In both cases, the derived planet’s transmission spectra are flat spectra, without any evidence of molecular absorption bands. A similar approach is used to model the TESS observations of V1298 Tau, a pre-mai sequence star hosting 4 exoplanets. I show that the stellar variability of V1298 Tau can be fitted with a 4-spot model, not evolving and rotating with the stellar surface. I correct the transit light curves of the 4 planets for the presence of spots (assumed to be not-crossed) and I estimate the effect that the same spots would cause on simultaneous observations in the K2 band. The results show that the effect is dependent on both the observation band and the spots’ configuration at the time of the transit.