arXiv subjects

Mario Melita

Publications and source records attributed to Mario Melita.

5 recordsLinked to original sources

arXiv2020

The dynamical evolution of close-in binary systems formed by a super-Earth and its host star. Case of the Kepler-21 system

The aim of this work is to develop a formalism for the study of the secular evolution of a binary system which includes interaction due to the tides that each body imparts on the other. We also consider the influence of the $J_2$-related secular terms on the orbital evolution and the torque, caused by the triaxiality, on the rotational evolution, both of which are associated only to one of the bodies. We apply these set of equations to the study of the orbital and rotational evolution of a binary system composed of a rocky planet and its host star in order to characterize the dynamical evolution at work, particularly near spin-orbit resonances. We used the equations of motion that give the time evolution of the orbital elements and the spin rates of each body to study the time evolution of the Kepler-21 system as an example of how the formalism that we have developed can be applied. We obtained a set of equations of motion without singularities for vanishing eccentricities and inclinations. This set gives, on one hand, the time evolution of the orbital elements due to the tidal potentials generated by both members of the system as well as the triaxiality of one of them. On the other hand, it gives the time evolution of the stellar spin rate due to the corresponding tidal torque and of the planet's rotation angle due to both the tidal and triaxiality-induced torques. We found that for the parameters and the initial conditions explored here, the tidally and triaxiality-induced modifications of the tidal modes can be more significative than expected and that the time of tidal synchronization strongly depends on the values of the rheological parameters.

astro-ph.EP↗

arXiv2018

Multicolor Photometry of the Neptune Irregular Satellite Neso

We report on time series photometry of the faint Neptune irregular satellite Neso. Observations in the V, R, and I pass-bands were performed in photometric conditions at the Cerro Paranal observatory using the instrument FORS2, in the night of July 15th, 2010. Astrometry and photometry derived from these observations are presented here. The time coverage of about six hours does not allow to construct a light curve and derive a meaningful rotational period. However, we could derive new estimates of apparent magnitudes obtaining R=25.2 pm 0.2 mag in agreement with Brozovic, Jacobson, Sheppard (2011), and also V=25.6 pm 0.3 mag, and I=24.5 pm 0.3. In this way we could derive for the first time Neso colors, V-I=1.0 pm 0.4 mag, R-I=0.7 pm 0.4 mag and V-R=0.3 pm 0.4 mag. We compared those colors with those in Peixinho, Delsanti, Doressoundiram (2015). The color R-I appears to be slightly redder than the typical values for Centaurs and KBOs, the color V-I is in nice agreement with both populations. The large error-bars prevents from assigning Neso to any of the reference classes, just looking at Neso colors, although the data seem to suggest that we can rule out its membership in classes of resonant objects or Plutinos.

astro-ph.EP↗

arXiv2014

TTVs analysis in Southern Stars: the case of WASP-28

We present 4 new transit observations of the exoplanet WASP-28b observed between August 2011 and October 2013. Employing another 11 transits available in the literature we compute new ephemeris and redetermine the physical parameters of the star and the exoplanet. Considering 3 yrs of observations, we find no periodic TTVs or long-term variations of the inclination of the orbit, i, or the depth of the transit, k, that could be attributable to the presence of another planetary mass-body in the system. We also study the relations between i and k with different factors that characterize the light-curves. The fits suggest a possible weak correlation between k with the red noise factor, β, and the photometric noise rate, PNR, and a weak anticorrelation between i and PNR, although more points are needed to confirm these trends. Finally, the kinematic study suggests that WASP-28 is a thin disk star.

astro-ph.EP↗

arXiv2013

Rotational Characterization of Hayabusa II Target Asteroid (162173) 1999 JU3

The Japanese Space Agency's Hayabusa II mission is scheduled to rendezvous with and return a sample from the near-Earth asteroid (162173) 1999 JU3. Previous visible-wavelength spectra of this object show significant variability across multiple epochs which could be the result of a compositionally heterogeneous surface. We present new visible and near-infrared spectra to demonstrate that thermally altered carbonaceous chondrites are plausible compositional analogs, however this is a tentative association due to a lack of any prominent absorption features in our data. We have also conducted a series of high signal-to-noise visible-wavelength observations to investigate the reported surface heterogeneity. Our time series of visible spectra do not show evidence for variability at a precision level of a few percent. This result suggests two most likely possibilities. One, that the surface of 1999 JU3 is homogenous and that unaccounted for systematic effects are causing spectral variation across epochs. Or two, that the surface of 1999 JU3 is regionally heterogenous, in which case existing shape models suggest that any heterogeneity must be limited to terrains smaller than approximately 5% of the total surface area. These new observations represent the last opportunity before both the launch and return of the Hayabusa II spacecraft to perform ground-based characterization of this asteroid. Ultimately, these predictions for composition and surface properties will be tested upon completion of the mission.

astro-ph.EP↗

arXiv2008

Detection of period variations in extrasolar transiting planet OGLE-TR-111b

Two consecutive transits of planetary companion OGLE-TR-111b were observed in the I band. Combining these observations with data from the literature, we find that the timing of the transits cannot be explained by a constant period, and that the observed variations cannot be originated by the presence of a satellite. However, a perturbing planet with the mass of the Earth in an exterior orbit could explain the observations if the orbit of OGLE-TR-111b is eccentric. We also show that the eccentricity needed to explain the observations is not ruled out by the radial velocity data found in the literature.

astro-ph↗