arXiv subjects

N. Todorovic

Publications and source records attributed to N. Todorovic.

3 recordsLinked to original sources

arXiv2026

Shape model and dynamical state of the asteroid (300) Geraldina: Implications for its possible ancient origin

In this study, we present a comprehensive photometric and physical characterisation of the main-belt asteroid (300) Geraldina. Our analysis includes determining its sidereal rotational period, shape modelling, spin-axis orientation, as well as dynamical and spectral properties. The investigation is based on two decades of archival photometry from the Bulgarian National Astronomical Observatory (BNAO) Rozhen, complemented by dense CCD lightcurve observations obtained since 2017 at the Astronomical Station Vidojevica (ASV), dense data from ALCDEF, and augmented with sparse-in-time measurements from Gaia Data Release 3 (DR3). By combining these heterogeneous datasets within and using the lightcurve inversion method, we confirmed the asteroid's prograde sense of rotation and obtained two symmetrically mirrored pole solutions for the asteroid model. Our dynamical studies show that (300) Geraldina remains stable in 100 Myr. Although close to the 2:1 mean-motion resonance with Jupiter, it is not captured into it during the observed time. Instead, it exhibits interactions with an unidentified high-order mean-motion resonance, which appears to contribute to its long-term stability. Its spectral type (C) with a primitive carbonaceous composition, in combination with low albedo and long-term stability, is consistent with the assumption that (300) Geraldina is an ancient asteroid.

astro-ph.EP↗

arXiv2024

The possible dual nature of the asteroid (12499) 1998 FR47

We present the R-band lightcurves of the Flora family asteroid (12499) 1998 FR47, obtained in 2022 at two different astronomical sites: Bulgarian National Astronomical Observatory Rozhen (MPC Code 071) and Astronomical Station Vidojevica (MPC Code C89). The quadramodal lightcurves reveal a rotation period of 6.172+/-0.003 h and an amplitude of about 0.44 mag. Using the lightcurve inversion method, with the combination of our dense lightcurves and the sparse data from Gaia DR3, we found the sidereal period, an indication of a retrograde rotation of (12499) and its low-convex resolution shape. Nonetheless, the unusual shape of the quadramodal lightcurve and its additional analysis reveals two possible periods, 3.0834+/-0.0085 h and 4.1245+/-0.0151 h, making the suspect that the asteroid might be a non-synchronised wide binary system. Spectral analysis of the asteroid using data from the GAIA DR3 shows that it is either an M- or an L-type object and maybe a piece of the first planetesimals to form in the Solar System protoplanetary disk. On the other hand, (12499)'s dynamical properties indicate a significantly shorter lifetime. The asteroid lies exactly on the chaotic border of the 7:4 mean motion resonance with Mars (7M:4), alternating between being in and out of it for almost 190 Myrs. During 200 Myrs of integration, (12499) visited other resonances in the Flora family, but it never became a Near Earth Object (NEO). Additional integration of fictive objects from the 7M:4 resonance showed a possibility of transportation to the NEO region already at about 20 Myrs.

astro-ph.EP↗

arXiv2004

Stability of Terrestrial Planets in the Habitable Zone of Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208

We have undertaken a thorough dynamical investigation of five extrasolar planetary systems using extensive numerical experiments. The systems Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208 were examined concerning the question of whether they could host terrestrial like planets in their habitable zones (=HZ). First we investigated the mean motion resonances between fictitious terrestrial planets and the existing gas giants in these five extrasolar systems. Then a fine grid of initial conditions for a potential terrestrial planet within the HZ was chosen for each system, from which the stability of orbits was then assessed by direct integrations over a time interval of 1 million years. The computations were carried out using a Lie-series integration method with an adaptive step size control. This integration method achieves machine precision accuracy in a highly efficient and robust way, requiring no special adjustments when the orbits have large eccentricities. The stability of orbits was examined with a determination of the Renyi entropy, estimated from recurrence plots, and with a more straight forward method based on the maximum eccentricity achieved by the planet over the 1 million year integration. Additionally, the eccentricity is an indication of the habitability of a terrestrial planet in the HZ; any value of e>0.2 produces a significant temperature difference on a planet's surface between apoapse and periapse. The results for possible stable orbits for terrestrial planets in habitable zones for the five systems are summarized as follows: for Gl 777 A nearly the entire HZ is stable, for 47 Uma, HD 72659 and HD 4208 terrestrial planets can survive for a sufficiently long time, while for Gl 614 our results exclude terrestrial planets moving in stable orbits within the HZ.

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