Browsing by Author "Biagiotti, F."

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    Star-spot activity, orbital obliquity, transmission spectrum, physical properties, and transit time variations of the HATS-2 planetary system
    (2024) Biagiotti, F.; Mancini, L.; Southworth, J.; Tregloan-Reed, J.; Naponiello, L.; Jorgensen, U. G.; Bach-Moller, N.; Basilicata, M.; Bonavita, M.; Bozza, V.; Burgdorf, M. J.; Dominik, M.; Jaimes, R. Figuera; Henning, Th.; Hinse, T. C.; Hundertmark, M.; Khalouei, E.; Longa-Pena, P.; Peixinho, N.; Rabus, M.; Rahvar, S.; Sajadian, S.; Skottfelt, J.; Snodgrass, C.; Jongen, Y.; Vignes, J. -p
    Aims. Our aim in this paper is to refine the orbital and physical parameters of the HATS-2 planetary system and study transit timing variations and atmospheric composition thanks to transit observations that span more than 10 yr and that were collected using different instruments and pass-band filters. We also investigate the orbital alignment of the system by studying the anomalies in the transit light curves induced by starspots on the photosphere of the parent star. Methods. We analysed new transit events from both ground-based telescopes and NASA's TESS mission. Anomalies were detected in most of the light curves and modelled as starspots occulted by the planet during transit events. We fitted the clean and symmetric light curves with the JKTEBOP code and those affected by anomalies with the PRISM+GEMC codes to simultaneously model the photometric parameters of the transits and the position, size, and contrast of each starspot. Results. We found consistency between the values we found for the physical and orbital parameters and those from the discovery paper and ATLAS9 stellar atmospherical models. We identified different sets of consecutive starspot-crossing events that temporally occurred in less than five days. Under the hypothesis that we are dealing with the same starspots, occulted twice by the planet during two consecutive transits, we estimated the rotational period of the parent star and, in turn the projected and the true orbital obliquity of the planet. We find that the system is well aligned. We identified the possible presence of transit timing variations in the system, which can be caused by tidal orbital decay, and we derived a low-resolution transmission spectrum.
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    The ultra-hot-Jupiter KELT-16 b: dynamical evolution and atmospheric properties
    (2022) Mancini, L.; Southworth, J.; Naponiello, L.; Basturk, O.; Barbato, D.; Biagiotti, F.; Bruni, I; Cabona, L.; D'Ago, G.; Damasso, M.; Erdem, A.; Evans, D.; Henning, Th; Ozturk, O.; Ricci, D.; Sozzetti, A.; Tregloan-Reed, J.; Yalcinkaya, S.
    We present broad-band photometry of 30 planetary transits of the ultra-hot-Jupiter KELT-16 b, using five medium-class telescopes. The transits were monitored through standard B, V, R, I filters and four were simultaneously observed from different places, for a total of 36 new light curves. We used these new photometric data and those from the TESS space telescope to review the main physical properties of the ICELT-16 planetary system. Our results agree with previous measurements but are more precise. We estimated the mid-transit times for each of these transits and combined them with others from the literature to obtain 69 epochs, with a time baseline extending over more than 4 yr, and searched for transit time variations. We found no evidence for a period change, suggesting a lower limit for orbital decay at 8 Myr, with a lower limit on the reduced tidal quality factor of Q(*)' > (1.9 +/- 0.8) x 10(5) with 95 per cent confidence. We built up an observational, low-resolution transmission spectrum of the planet, finding evidence of the presence of optical absorbers, although with a low significance. Using TESS data, we reconstructed the phase curve finding that KELT-16 b has a phase offset of 25.25 +/- 14.03 degrees E, a day- and night-side brightness temperature of 3190 +/- 61 K and 2668 +/- 56 K, respectively. Finally, we compared the flux ratio of the planet over its star at the TESS and Spitzer wavelengths with theoretical emission spectra, finding evidence of a temperature inversion in the planet's atmosphere, the chemical composition of which is preferably oxygen-rich rather than carbon-rich.