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The planet Mercury is predominantly made up of an iron core, covered by a comparatively thin silicate layer, which has led to the idea that this configuration is the product of mantle stripping by a giant impact. In the literature, a classical hit-and-run impact has been explored in which a roughly Mars-mass proto-Mercury collides with an Earth-mass target, losing large parts of its mantle. However, such hit-and-run collisions between proto-planets of very different masses are rare in N-body simulations of terrestrial planet formation. On the other hand, hit-and-run collisions involving similar mass bodies appear to be more frequent. Our aim here is to investigate the conditions under which collisions of similar mass bodies are able to form a Mercury-like planet, fulfilling the necessary constraints in terms of mass and composition (silicate-to-iron mass ratio). We perform a series of smooth particle hydrodynamics (SPH) collision simulations. Our results show that it is possible to obtain Mercury-analogues from hit-and-run collisions involving a proto-Mercury roughly twice the mass of Mercury and targets of comparable mass (between 1 and 4 times higher), as long as the impact parameters (impact angle and velocity) are properly adjusted according to a set of well established scaling laws, while remaining compatible with the values typically observed in N-body simulations.

The 99942 Apophis close encounter with Earth in 2029 may provide information about asteroid's physical characteristics and measurements of Earth's effects on the asteroid surface. In this work, we analysed the surface and the nearby dynamics of Apophis. The possible effects of its 2029 encounter on the surface and environment vicinity are also analysed. We consider a 340 metres polyhedron with a uniform density (1.29 g$\cdot$cm$^{-3}$, 2.2 g$\cdot$cm$^{-3}$ and 3.5 g$\cdot$cm$^{-3}$). The slope angles are computed, as well their variation that arises during the close approach. Such variation reaches 4$^{\circ}$ when low densities are used in our simulations and reaches 2$^{\circ}$ when the density is high. The zero-velocity curves, the equilibrium points, and their topological classification are obtained. We found four external equilibrium points and two of them are linearly stable. We also perform numerical simulations of bodies orbiting the asteroid, taking into account the irregular gravitational field of Apophis and two extra scenarios of perturbations: the solar radiation pressure and the Earth's perturbation during the close approach. The radiation pressure plays an important role in the vicinity of the asteroid, only cm-sized particles survived for the time of integration. For densities of 2.2 g$\cdot$cm$^{-3}$ and 3.5 g$\cdot$cm$^{-3}$, a region of 5 cm radius particles survived for 30 years of the simulation, and for 1.29 g$\cdot$cm$^{-3}$, only particles with 15 cm of radius survived. The ejections and collisions are about 30-50 times larger when the close encounter effect is added, but around 56-59% of particles still survive the encounter., Comment: 17 pages, 15 figures

The sailboat region was first identified by Giuliatti Winter, et al. (2010) exploring the Pluto-Charon binary system, they identifed this unexpected stable region of S-type orbits around the dwarfplanet Pluto located at a = (0.5d, 0.7d) and e = (0.2, 0.9), where a and e are the initial valuesof semi-major axis and eccentricity of particles, respectively and d is the separation of the binary.The sailboat is associated with a family ”BD” of periodic orbits derived from the planar, circular,restricted three-body problem. In this work, we analyzed through numerical simulations the structureand stability of sailboat in hypothetical systems with different values of mass ratio and for severalorbital configurations.To constrain the orbital parameters for sailboat regions, we numerically simulated several ellipticthree-body problem, exploring a large range of initial conditions. We adopt dimensionless systemsand the configuration for each simulation include a test particle in S-type orbit around the primarybody and gravitational disturbed by the secondary massive body. We set the central body as a pointof mass and a secondary with a mass equivalent to the mass ratio of the binary system (µ), with itsradius (r s ) defined as 10% of their Hill radius.We created hypothetical systems with different mass ratio in the interval µ = [0.01, 0.30] in steps∆µ = 0.01. The test particles were randomly distributed with semimajor axis in a = [0.45, 0.7],considering 1 the distance between the two main bodies, the eccentricities varied from 0 to 0.99, andinitially the argument of the pericentre and inclination was set as 0º. We numerically integrated usingthe REBOUND package and IAS15 integrator (Rein & Spiegel 2014) for 10 4 orbital periods of thebinary.We analyzed the behaviour of the sailboat according to the eccentricity e of the secondary body,looking for the maximum value for which the particles remain stable. A final set of simulations wasperformed for different values of inclinations and argument of pericenter in order to determine theextreme values for the stability.Our results show the sailboat is robust and it exists for µ = [0.01,0.27] and for large intervalsof the argument of pericentre and inclination. This region of stability reaches its maximum sizewith an argument of pericenter at 0 ◦ and 180 ◦ . The sailboat region also is present for values ofinclination > 60º and existing even retrogrades orbits in the systems with µ > 0.08.The numerical results also showed that little changes in the eccentricity of the secondary body issufficient to vanish the sailboat region, for binaries system with µ > 0.12, the sailboat exists just forvalues of e < 0.05.

The dynamical evolution of the Prometheus and Pandora pair of satellites is chaotic, with a short 3.3 years Lyapunov time. It is known that the anti-alignment of the apses line of Prometheus and Pandora, which occurs every 6.2 years, is a critical configuration that amplifies their chaotic dynamical evolution. However, the mutual interaction between Prometheus and Pandora is not enough to explain the longitudinal lags observed by the Hubble Space Telescope. The main goal of the current work is to identify the main contributors to the chaotic dynamical evolution of the Prometheus-Pandora pair beyond themselves. Therefore, in this work, we first explore the sensibility of this dynamical system to understand it numerically and then build numerical experiments to reach our goals. We identified that almost all major satellites of the Saturn system play a significant role in the evolution of Prometheus' and Pandora's orbits., Comment: 8 pages, 6 figures

Full list of authors: Morgado, B. E.; Sicardy, B.; Braga-Ribas, F.; Desmars, J.; Gomes-Júnior, A. R.; Bérard, D.; Leiva, R.; Ortiz, J. L.; Vieira-Martins, R.; Benedetti-Rossi, G.; Santos-Sanz, P.; Camargo, J. I. B.; Duffard, R.; Rommel, F. L.; Assafin, M.; Boufleur, R. C.; Colas, F.; Kretlow, M.; Beisker, W.; Sfair, R.; Snodgrass, C.; Morales, N.; Fernández-Valenzuela, E.; Amaral, L. S.; Amarante, A.; Artola, R. A.; Backes, M.; Bath, K. -L.; Bouley, S.; Buie, M. W.; Cacella, P.; Colazo, C. A.; Colque, J. P.; Dauvergne, J. -L.; Dominik, M.; Emilio, M.; Erickson, C.; Evans, R.; Fabrega-Polleri, J.; Garcia-Lambas, D.; Giacchini, B. L.; Hanna, W.; Herald, D.; Hesler, G.; Hinse, T. C.; Jacques, C.; Jehin, E.; Jørgensen, U. G.; Kerr, S.; Kouprianov, V.; Levine, S. E.; Linder, T.; Maley, P. D.; Machado, D. I.; Maquet, L.; Maury, A.; Melia, R.; Meza, E.; Mondon, B.; Moura, T.; Newman, J.; Payet, T.; Pereira, C. L.; Pollock, J.; Poltronieri, R. C.; Quispe-Huaynasi, F.; Reichart, D.; de Santana, T.; Schneiter, E. M.; Sieyra, M. V.; Skottfelt, J.; Soulier, J. F.; Starck, M.; Thierry, P.; Torres, P. J.; Trabuco, L. L.; Unda-Sanzana, E.; Yamashita, T. A. R.; Winter, O. C.; Zapata, A.; Zuluaga, C. A.--This is an Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited., Context. The Centaur (10199) Chariklo has the first ring system discovered around a small object. It was first observed using stellar occultation in 2013. Stellar occultations allow sizes and shapes to be determined with kilometre accuracy, and provide the characteristics of the occulting object and its vicinity. Aims. Using stellar occultations observed between 2017 and 2020, our aim is to constrain the physical parameters of Chariklo and its rings. We also determine the structure of the rings, and obtain precise astrometrical positions of Chariklo. Methods. We predicted and organised several observational campaigns of stellar occultations by Chariklo. Occultation light curves were measured from the datasets, from which ingress and egress times, and the ring widths and opacity values were obtained. These measurements, combined with results from previous works, allow us to obtain significant constraints on Chariklo's shape and ring structure. Results. We characterise Chariklo's ring system (C1R and C2R), and obtain radii and pole orientations that are consistent with, but more accurate than, results from previous occultations. We confirm the detection of W-shaped structures within C1R and an evident variation in radial width. The observed width ranges between 4.8 and 9.1 km with a mean value of 6.5 km. One dual observation (visible and red) does not reveal any differences in the C1R opacity profiles, indicating a ring particle size larger than a few microns. The C1R ring eccentricity is found to be smaller than 0.022 (3σ), and its width variations may indicate an eccentricity higher than ~0.005. We fit a tri-axial shape to Chariklo's detections over 11 occultations, and determine that Chariklo is consistent with an ellipsoid with semi-axes of 143.8-1.5+1.4, 135.2-2.8+1.4, and 99.1-2.7+5.4 km. Ultimately, we provided seven astrometric positions at a milliarcsecond accuracy level, based on Gaia EDR3, and use it to improve Chariklo's ephemeris. © B. E. Morgado et al. 2021., This work was carried out within the “Lucky Star” umbrella that agglomerates the efforts of the Paris, Granada and Rio teams, which is funded by the European Research Council under the European Community’s H2020 (ERC Grant Agreement No. 669416). This research made use of SORA, a python package for stellar occultations reduction and analysis, developed with the support of ERC Lucky Star and LIneA/Brazil, within the collaboration Rio-Paris-Granada teams. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Part of this research is suported by INCT do e-Universo, Brazil (CNPQ grants 465376/2014-2). Based in part on observations made at the Laboratório Nacional de Astrofísica (LNA), Itajubá-MG, Brazil. The data include observations taken by the MiNDSTEp team at the Danish 1.54 m telescope at ESO’s La Silla observatory” and “UGJ acknowledges funding from the European Union H2020-MSCA-ITN-2019 under grant no. 860470 (CHAMELEON) and from the Novo Nordisk Foundation Interdisciplinary Synergy Programme grant no. NNF19OC0057374. TRAPPIST-South is funded by the Belgian Fund for Scientific Research (Fond National de la Recherche Scientifique, FNRS) under the grant PDR T.0120.21. The authors acknowledge the use of Sonja Itting-Enke’s C14 telescope and the facilities at the Cuno Hoffmeister Memorial Observatory (CHMO). The following authors acknowledge the respective CNPq grants: BEM 150612/2020-6; FB-R 314772/2020-0; RV-M 304544/2017-f5, 401903/2016-8; JIBC 308150/2016-3 and 305917/2019-6; MA 427700/2018-3, 310683/2017-3, 473002/2013-2. G.B.R. acknowledges CAPES-FAPERJ/PAPDRJ grant E26/203.173/2016 and CAPES-PRINT/UNESP grant 88887.571156/2020-00, MA FAPERJ grant E-26/111.488/2013 and ARGJr FAPESP grant 2018/11239-8. J.L.O., P.S.-S., R.D., and N.M. acknowledge financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709), from Spanish project AYA2017-89637-R, and from FEDER. P.S.-S. acknowledges financial support by the Spanish grant AYA-RTI2018-098657-J-I00 “LEO-SBNAF” (MCIU/AEI/FEDER, UE). E. Jehin is a Belgian FNRS Senior Research Associate. R.S. and O.C.W. acknowledge FAPESP grant 2016/24561-0 and CNPq grant 305210/2018-1. T.C.H. acknowledges financial support from the National Research Foundation (NRF; No. 2019R1I1A1A01059609).

Full list of authors: Rommel, F. L.; Braga-Ribas, F.; Desmars, J.; Camargo, J. I. B.; Ortiz, J. L.; Sicardy, B.; Vieira-Martins, R.; Assafin, M.; Santos-Sanz, P.; Duffard, R.; Fernández-Valenzuela, E.; Lecacheux, J.; Morgado, B. E.; Benedetti-Rossi, G.; Gomes-Júnior, A. R.; Pereira, C. L.; Herald, D.; Hanna, W.; Bradshaw, J.; Morales, N. Brimacombe, J.; Burtovoi, A.; Carruthers, T.; de Barros, J. R.; Fiori, M.; Gilmore, A.; Hooper, D.; Hornoch, K.; Jacques, C.; Janik, T.; Kerr, S.; Kilmartin, P.; Winkel, Jan Maarten; Naletto, G.; Nardiello, D.; Nascimbeni, V.; Newman, J.; Ossola, A.; Pál, A.; Pimentel, E.; Pravec, P.; Sposetti, S.; Stechina, A.; Szakáts, R.; Ueno, Y.; Zampieri, L.; Broughton, J.; Dunham, J. B.; Dunham, D. W.; Gault, D.; Hayamizu, T.; Hosoi, K.; Jehin, E.; Jones, R.; Kitazaki, K.; Komžík, R.; Marciniak, A.; Maury, A.; Mikuž, H.; Nosworthy, P.; Fábrega Polleri, J.; Rahvar, S.; Sfair, R.; Siqueira, P. B.; Snodgrass, C.; Sogorb, P.; Tomioka, H.; Tregloan-Reed, J.; Winter, O. C., Context. Trans-Neptunian objects (TNOs) and Centaurs are remnants of our planetary system formation, and their physical properties have invaluable information for evolutionary theories. Stellar occultation is a ground-based method for studying these distant small bodies and has presented exciting results. These observations can provide precise profiles of the involved body, allowing an accurate determination of its size and shape. Aims. The goal is to show that even single-chord detections of TNOs allow us to measure their milliarcsecond astrometric positions in the reference frame of the Gaia second data release (DR2). Accurate ephemerides can then be generated, allowing predictions of stellar occultations with much higher reliability. Methods. We analyzed data from various stellar occultation detections to obtain astrometric positions of the involved bodies. The events published before the Gaia era were updated so that the Gaia DR2 stellar catalog is the reference, thus providing accurate positions. Events with detection from one or two different sites (single or double chord) were analyzed to determine the event duration. Previously determined sizes were used to calculate the position of the object center and its corresponding error with respectto the detected chord and the International Celestial Reference System propagated Gaia DR2 star position. Results. We derive 37 precise astrometric positions for 19 TNOs and four Centaurs. Twenty-one of these events are presented here for the first time. Although about 68% of our results are based on single-chord detection, most have intrinsic precision at the submilliarcsecond level. Lower limits on the diameter of bodies such as Sedna, 2002 KX14, and Echeclus, and also shape constraints on 2002 VE95, 2003 FF128, and 2005 TV189 are presented as valuable byproducts. Conclusions. Using the Gaia DR2 catalog, we show that even a single detection of a stellar occultation allows improving the object ephemeris significantly, which in turn enables predicting a future stellar occultation with high accuracy. Observational campaigns can be efficiently organized with this help, and may provide a full physical characterization of the involved object, or even the study of topographic features such as satellites or rings. © 2020 ESO., This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior - Brasil (CAPES) - Finance Code 001 and the National Institute of Science and Technology of the e-Universe project (INCT do e-Universo, CNPq grant 465376/2014-2). The following authors acknowledge the respective CNPq grants: F.B.-R. 309578/2017-5; R.V.-M. 304544/2017-5, 401903/2016-8; J.I.B.C. 308150/2016-3; M.A. 427700/2018-3, 310683/2017-3, 473002/2013-2; O.C.W. 305210/2018-1. The following authors acknowledge the respective grants: B.E.M. thanks the CAPES/Cofecub-394/2016-05 grant; G.B-R. acknowledges CAPES-FAPERJ/PAPDRJ grant E26/203.173/2016; M.A. acknowledges FAPERJ grant E-26/111.488/2013; A.R.G.Jr acknowledges FAPESP grant 2018/11239-8; O.C.W. and R.S. acknowledge FAPESP grant 2016/24561-0. D.N. acknowledges support from the French Centre National d'Etudes Spatiales (CNES). K.H. and P.P. were supported by the project R.V.O.: 67985815. A.P. and R.S. received support from the K-125015 grant of the National Research, Development and Innovation Office (NKFIH, Hungary). Partial funding of the computational infrastructure and database servers are received from the grant KEP-7/2018 of the Hungarian Academy of Sciences. Some of the results were based on observations taken at the 1.6m telescope on Pico dos Dias Observatory of the National Laboratory of Astrophysics (LNA/Brazil). Some data are based on observations collected at the Copernicus and Schmidt telescopes (Asiago, Italy) of the INAF-Astronomical Observatory of Padova. This work was carried out within the "Lucky Star" umbrella that agglomerates the efforts of the Paris, Granada and Rio teams, which is funded by the European Research Council under the European Community's H2020 (ERC Grant Agreement No. 669416). This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium).Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. TRAPPIST is a project funded by the Belgian FNRS under grant FRFC 2.5.594.09.F and the ARC grant for Concerted Research Actions, financed by the Wallonia-Brussels Federation. E.J. is a FNRS Senior Research Associate. We would like to acknowledge financial support by the Spanish grant AYA-RTI2018-098657-JI00 "LEO-SBNAF" (MCIU/AEI/FEDER, U.E.) and the financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709). Also, AYA2017-89637-R and FEDER funds are acknowledged. We are thankful to the following observers who participated and provided data for respective events as listed in Table B.1: Orlando A. Naranjo from Universidad de Los Andes, Merida/VEN; Faustino Organero from La Hita Observatory - Toledo/ESP.

Transneptunian Objects (TNOs) are the remnants of our planetary system and can retain information about the early stages of the Solar System formation. Stellar occultation is a ground-based method used to study these distant bodies which have been presenting exciting results mainly about their physical properties. The big TNO called 2002 MS4 was discovered by Trujillo, C. A., & Brown, M. E., in 2002 using observations made at the Palomar Observatory (EUA). It is classified as a hot classical TNO, with orbital parameters a = 42 AU, e = 0.139, and i = 17.7º. Using thermal measurements with PACS (Herschel) and MIPS (Spitzer Space Telescope) instruments, Vilenius et al. 2012 obtained a radius of 467 +/- 23.5 km and an albedo of 0.051. Predictions of stellar occultations by this body in 2019 were obtained using the Gaia DR2 catalogue and NIMA ephemeris (Desmars et al. 2015) and made available in the Lucky Star web page (https://lesia.obspm.fr/lucky-star/). Four events were observed in South America and Canada. The first stellar occultation was detected on 09 July 2019, resulting in two positives and four negatives chords, including a close one which proven to be helpful to constrain the body’s size. This detection also allowed us to obtain a precise astrometric position that was used to update its ephemeris and improve the predictions of the following events. Two of them were detected on 26 July 2019, separated by eight hours. The first event was observed from South America and resulted in three positive detections, while the second, observed from Canada, resulted in a single chord. Another double chord event was observed on 19 August 2019 also from Canada. Due to its size, it is expected that 2002 MS4 is in hydrostatic equilibrium. Thirouin, A. 2013 obtained a rotational light curve of 2002 MS4 and determined two possible periods (7.33 h and 10.44 h) with low amplitude variation (0.05 +/- 0.01 mag). Admitting that it has a Maclaurin shape, the projected limb in the sky plane for Earth-based observers should be the same in the 09 July and 26 July events. The multi-chord detection allows determining an interval of parameters for size and shape. Considering that the same figure should have been observed in the 09 July event, we could use the both chords and the negative observations to constrain its physical parameters. With that, we could determine that 2002 MS4 has an equivalent radius of 385 +/- 1 km (Figure 1). Our results indicate that this TNO is about 100 km smaller in diameter than the value obtained by Vilenius et al. 2012, implying an albedo of 0.076 (Hv = 4.0 +/- 0.6) . The astrometric positions derived from these data were also helpful to improve forthcoming stellar occultations, in special the one crossing Europe on 08 August this year. More data from stellar occultations and observations of rotational light curves will help to confirm these results and assumptions. Acknowledgements: F.L.R is thankful for the support of the CAPES scholarship. The following authors acknowledge the respective CNPq grants: F.B-R 309578/2017-5; R.V-M 304544/2017-5, 401903/2016-8; J.I.B.C. 308150/2016-3; M.A 427700/2018-3, 310683/2017-3, 473002/2013-2. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001 and the National Institute of Science and Technology of the e-Universe project (INCT do e-Universo, CNPq grant 465376/2014-2). G.B-R acknowledges CAPES-FAPERJ/PAPDRJ grant E26/203.173/2016, M.A FAPERJ grant E-26/111.488/2013 and A.R.G-Jr FAPESP grant 2018/11239-8. B.E.M thanks the CAPES/Cofecub-394/2016-05 grant. P.S-S. acknowledges financial support by the Spanish grant AYA-RTI2018-098657-J-I00 "LEO-SBNAF" (MCIU/AEI/FEDER, UE). We would like to acknowledge financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofı́sica de Andalucı́a (SEV-2017-0709) and the financial support by the Spanish grant AYA-2017-84637-R. Part of the results were based on observations taken at the 1.6 m telescope on Pico dos Dias Observatory of the National Laboratory of Astrophysics (LNA/Brazil). Part of this work was carried out within the “Lucky Star" umbrella that agglomerates the efforts of the Paris, Granada and Rio teams. It is funded by the European Research Council under the European Community’s H2020 (2014-2020/ERC Grant Agreement No. 669416). This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. References Assafin, M. et al. PRAIA - Platform for Reduction of Astronomical Images Automatically. In: Tanga, P.; Thuillot, W. (Ed.). Gaia follow-up network for the solar system objects : Gaia FUN-SSO workshop proceedings, held at IMCCE -Paris Observatory, France, November 29 - December 1, 2010 / edited by Paolo Tanga, William Thuillot.- ISBN 2-910015-63-7, p. 85-88. [S.l.: s.n.], 2011. p. 85–88. Desmars, J. et al. Orbit determination of trans-Neptunian objects and Centaurs for the prediction of stellar occultations. Astronomy & Astrophysics, v. 584, p. A96, dez. 2015. Thirouin, A. Study of Trans-Neptunian Objects using photometric techniques and numerical simulations. Dissertation. Editorial de la Universidad de Granada. Spain, 2013. Trujillo, C. A., Brown, M. E., Minor Planet Electronic Circulars – MPEC 2002-W27. Disponível em: \url{https://minorplanetcenter.net//iau/mpec/K02/K02W27.html}. Vilenius, E. “TNOs are cool”: a survey of the trans-Neptunian region. VI. Herschel/PACS observations and thermal modelling of 19 classical Kuiper belt objects. Astronomy & Astrophysics. v. 541, A94, 2012.

Introduction Asteroids are reminiscent bodies of the Solar System that are irregularly shaped, though some of them are nearly spheroidal. Despite of their irregular shape, some asteroids have similar characteristics. The spinning-top asteroids are characterized as oblate shapes with a pronounced equatorial bulge, as well as their fast rotation. To understand the dynamics around these asteroids, we calculate the equilibrium points [1] of some spinning-top bodies, considering their irregular shape. The equilibrium points are points where there is a balance between the gravitational and centrifugal forces. Thus, when the body is spinning faster, the equilibrium points may be closer to the body, and some of them could touch the body's surface or even be inside the body. Besides the location of the equilibrium points, we also examined their topological structure according to the eigenvalues of the characteristic equation in the complex plane. Location and classification of the equilibrium points We considered a set of spinning-top asteroids to compute their respective equilibrium points: the Alpha bodies of the triples systems 2001 SN263 [2] and 1994 CC [3], the Alpha body of the binary system 1999 KW4 [4], the asteroids 2008 EV5 [5,6], Ryugu [7] and the retrograde model of the asteroid 1950 DA [8,9]. In this study, we identified that the Alpha body from the triple system 2001 SN263 has the larger number of equilibrium points, with 13 points. Among these points, the E13 point is the central one, the point E5 is an inner point and the remaining are close to the surface of the body, as if they were contouring the surface (Fig. 1). The Alpha bodies from the systems 1994 CC and 1999 KW4, the asteroids 2008 EV5, and Ryugu have seven equilibrium points. In the same way as the equilibrium points of the 2001 SN263 Alpha, the equilibrium points of the Alpha bodies from the systems 1994 CC and 1999 KW4 are close to or inner to their surfaces. For the Alpha 1994 CC, only one equilibrium point is outside of the body. The asteroids Ryugu and 2008 EV5 also have points close to the surfaces. However, these points are not so close as the other bodies analyzed in this study. Since the rotation period of Ryugu is slower (7.63262 hours) it is expected that its points are not so close to the surface. For the asteroid 1950 DA we calculated the equilibrium points for different bulk densities (3.5 g cm⁻³ to 1.0 g cm⁻³). We find nine equilibrium points for the larger bulk density and in this case all points are close to the surface. However, as we decrease the bulk density, the equilibrium points move closer to the body's surface, even going inside the body for the smaller densities. Consequently, the number of points decreases, reaching the case of having only a single equilibrium point. In this case, the cohesive forces are important to keep the body's shape [9]. In terms of topological classification, we verified some similarities among all the points we calculated. All the odd points are classified as Saddle-Centre-Centre, while the even points are divided into two classifications: Sink-Source-Centre and Centre-Centre-Centre, being the Centre-Centre-Centre the only linearly stable points. Figure 1: Location of equilibrium points of the body Alpha from the triple system 2001 SN263 in the XY plane. Acknowledgments This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brazil (CAPES) - Finance Code 001, CNPQ (Proc. 305210/2018-1) and FAPESP (Proc. 2016/24561-0 and Proc. 2019/23963-5), CNPQ (Proc. 305737/2015-5). References [1] Jiang, Yu, et al. "Orbits and manifolds near the equilibrium points around a rotating asteroid." Astrophysics and Space Science 349.1 (2014): 83-106. [2] Becker, T. M. et al. Physical modeling of triple near-Earth Asteroid (153591) 2001 SN263 from radar and optical light curve observations. Icarus, [s.l.], v.248, p.499-515, mar. 2015. Elsevier BV. Elsevier BV. [3] Brozović, M. et al. Radar and optical observations and physical modeling of triple near-Earth Asteroid (136617) 1994 CC. Icarus, [s.l.],v. 216, n. 1, p.241-256, nov. 2011. Elsevier BV. [4] Ostro, S. J. et al. Radar Imaging of Binary Near-Earth Asteroid (66391) 1999 KW4. Science, [s.l.], v. 314, n. 5803, p.1276-1280, 24 nov. 2006. American Association for the Advancement of Science (AAAS). [5] Busch, M. W. et al. Radar observations and the shape of near-Earth asteroid 2008 EV5. Icarus, [s.l.], v. 212, n. 2, p.649-660. 2011. Elsevier BV. [6] Tardivel, S., P. Sánchez, and D. J. Scheeres. ”The Story of 2008 EV5-Evidence of Fission.”Lunar and Planetary Science Conference. Vol. 47. 2016. [7] Watanabe, S. et al. Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu—A spinning top-shaped rubble pile. Science, [s.l.], 19 mar. 2019a. American Association for the Advancement of Science (AAAS). [8] Busch, M. W., et al. "Physical modeling of near-Earth Asteroid (29075) 1950 DA." Icarus 190.2 (2007): 608-621. [9] Rozitis, B .et al. "Cohesive forces prevent the rotational breakup of rubble-pile asteroid (29075) 1950 DA." Nature 512.7513 (2014): 174-176.

The (153591) 2001 SN263 asteroid system, target of the first Brazilian interplanetary space mission, is one of the known three triple systems within the population of NEAs. One of the mission objectives is to collect data about the formation of this system. The analysis of these data will help in the investigation of the physical and dynamical structures of the components (Alpha, Beta and Gamma) of this system, in order to find vestiges related to its origin. In this work, we assume the irregular shape of the 2001 SN263 system components as uniform density polyhedra and computationally investigate the gravitational field generated by these bodies. The goal is to explore the dynamical characteristics of the surface and environment around each component. Then, taking into account the rotational speed, we analyze their topographic features through the quantities geometric altitude, tilt, geopotential, slope, surface accelerations, among others. Additionally, the investigation of the environment around the bodies made it possible to construct zero-velocity curves, which delimit the location of equilibrium points. The Alpha component has a peculiar number of 12 equilibrium points, all of them located very close to its surface. In the cases of Beta and Gamma, we found four equilibrium points not so close to their surfaces. Then, performing numerical experiments around their equilibrium points, we identified the location and size of just one stable region, which is associated with an equilibrium point around Beta. Finally, we integrated a spherical cloud of particles around Alpha and identified the location on the surface of Alpha were the particles have fallen., Comment: 22 pages, 16 figures

In this work, we study the dynamics of particles around Bennu. The goal is to understand the stability, evolution, and final outcome of the simulated particles around the asteroid. According to the results, the particle sizes can be divided into two main groups depending on their behavior. Particles smaller than a centimeter are quickly removed from the system by solar radiation pressure, while the dynamics of particles larger than a few centimeters is dominated by the gravitational field of Bennu. Because of its shape and spin period, Bennu has eight equilibrium points around it. The structure of the phase space near its equatorial surface is directly connected to these equilibrium points. Therefore, we performed numerical simulations to obtain information about the orbital evolution near the equilibrium points. The results show that most of the particles larger than a few centimeters fall in the equatorial region close to the Kingfisher area or close to the region diametrically opposite to it. In contrast, almost none of these particles fall in the equatorial region close to the Osprey area. In addition, we also performed computational experiments considering a spherical cloud of particles initially orbiting Bennu. Most of the particles in prograde orbits fall on the surface within our integration period, which was limited to 1.14 years. The particles preferentially fall near high-altitude regions at low equatorial latitudes and close to the north pole. The mid-latitudes are those more depleted of falls, as in the Nightingale and Sandpiper areas., Comment: 33 pages, 13 figures and 4 tables. Accepted for publication by "Exploration of the Activity of Asteroid (101955) Bennu", a special edition of the Journal of Geophysical Research: Planets. Simulation codes available on https://github.com/a-amarante. Animated movies of simulation results available from https://www.youtube.com/playlist?list=PLepZc10dZiUouELKD7w-3eZ4XOspuVgnm

Radar observations show that (16) Psyche is one of the largest and most massive asteroids of the M-class located in the main belt, with a diameter of approximately 230 km. This fact makes Psyche a unique object since observations indicated an iron-nickel composition. It is believed that this body may be what was left of a metal core of an early planet that would have been fragmented over millions of years due to violent collisions. In this work we study a variety of dynamical aspects related to the surface, as well as, the environment around this asteroid. We use computational tools to explore the gravitational field generated by this body, assuming constant values for its density and rotation period. We then determine a set of physical and dynamical characteristics over its entire surface. The results include the geometric altitude, geopotential altitude, tilt, slope, among others. We also explore the neighborhood around the asteroid (16) Psyche, so that the location and linear stability of the equilibrium points were found. We found four external equilibrium points, two of them linearly stable. We confirmed the stability of these points by performing numerical simulations of massless particles around the asteroid, which also showed an asymmetry in the size of the stable regions. In addition, we integrate a cloud of particles in the vicinity of (16) Psyche in order to verify in which regions of its surface the particles are most likely to collide., Comment: 19 pages

Made available in DSpace on 2022-04-28T19:44:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-08-01 The young star PDS110 in the Ori OB1a association underwent two similar eclipses in 2008 and 2011, each of which lasted for a period of at least 25 days. One plausible explanation for these events is that the star was eclipsed by an unseen giant planet (named PDS110b) circled by a ring system that fills a large fraction of its Hill sphere. Through thousands of numerical simulations of the three-body problem, we constrain the mass and eccentricity of this planet as well the size and inclination of its ring, parameters that are not well determined by the observational data alone. We carried out a broad range of different configurations for the PDS110b ring system and ruled out all that did not match with the observations. The result shows that the ring system could be prograde or retrograde; the preferred solution is that the ring has an inclination lower than 60° and a radius between 0.1 and 0.2 au and that the planet is more massive than 35 MJup and has a low eccentricity (

Progress in astrometry and orbital modelling of planetary moons in the last decade enabled better determinations of their orbits. These studies need accurate positions spread over extended periods. We present the results of the 2014-2015 Brazilian campaign for 40 mutual events from 47 observed light curves by the Galilean satellites plus one eclipse of Amalthea by Ganymede. We also reanalysed and updated results for 25 mutual events observed in the 2009 campaign. All telescopes were equipped with narrow-band filters centred at 889 nm with a width of 15 nm to eliminate the scattered light from Jupiter. The albedos' ratio was determined using images before and after each event. We simulated images of moons, umbra, and penumbra in the sky plane, and integrated their fluxes to compute albedos, simulate light curves and fit them to the observed ones using a chi-square fitting procedure. For that, we used the complete version of the Oren-Nayer reflectance model. The relative satellite positions mean uncertainty was 11.2 mas ($\sim$35 km) and 10.1 mas ($\sim$31 km) for the 2014-2015 and 2009 campaigns respectively. The simulated and observed \textsc{ascii} light curve files are freely available in electronic form at the \textit{Natural Satellites DataBase} (NSDB). The 40/25 mutual events from our 2014-2015/2009 campaigns represent a significant contribution of 17%/15% in comparison with the PHEMU campaigns lead by the IMCCE. Besides that, our result for the eclipse of Amalthea is only the 4$^{th}$ such measurement ever published after the three ones observed by the 2014-2015 international PHEMU campaign. Our results are suitable for new orbital/ephemeris determinations for the Galilean moons and Amalthea., 14 pages, 8 figures and 5 tables

Context. Bright stellar positions are now known with an uncertainty below 1 mas thanks to Gaia DR2. Between 2019-2020, the Galactic plane will be the background of Jupiter. The dense stellar background will lead to an increase in the number of occultations, while the Gaia DR2 catalogue will reduce the prediction uncertainties for the shadow path. Aims. We observed a stellar occultation by the Galilean moon Europa (J2) and propose a campaign for observing stellar occultations for all Galilean moons. Methods. During a predicted period of time, we measured the light flux of the occulted star and the object to determine the time when the flux dropped with respect to one or more reference stars, and the time that it rose again for each observational station. The chords obtained from these observations allowed us to determine apparent sizes, oblatness, and positions with kilometre accuracy. Results. We present results obtained from the first stellar occultation by the Galilean moon Europa observed on 2017 March 31. The apparent fitted ellipse presents an equivalent radius of 1561.2 $\pm$ 3.6 km and oblatenesses 0.0010 $\pm$ 0.0028. A very precise Europa position was determined with an uncertainty of 0.8 mas. We also present prospects for a campaign to observe the future events that will occur between 2019 and 2021 for all Galilean moons. Conclusions. Stellar occultation is a suitable technique for obtaining physical parameters and highly accurate positions of bright satellites close to their primary. A number of successful events can render the 3D shapes of the Galilean moons with high accuracy. We encourage the observational community (amateurs included) to observe the future predicted events., Comment: 10 pages, 16 figures, 4 tables, A&A Letter doi:10.1051/0004-6361/201935500

PDS 110 is a young disk-hosting star in the Orion OB1A association. Two dimming events of similar depth and duration were seen in 2008 (WASP) and 2011 (KELT), consistent with an object in a closed periodic orbit. In this paper we present data from a ground-based observing campaign designed to measure the star both photometrically and spectroscopically during the time of predicted eclipse in September 2017. Despite high-quality photometry, the predicted eclipse did not occur, although coherent structure is present suggesting variable amounts of stellar flux or dust obscuration. We also searched for RV oscillations caused by any hypothetical companion and can rule out close binaries to 0.1 $M_\odot$. A search of Sonneberg plate archive data also enabled us to extend the photometric baseline of this star back more than 50 years, and similarly does not re-detect any deep eclipses. Taken together, they suggest that the eclipses seen in WASP and KELT photometry were due to aperiodic events. It would seem that PDS 110 undergoes stochastic dimmings that are shallower and shorter-duration than those of UX Ori variables, but may have a similar mechanism., Comment: Accepted to MNRAS; 12 pages, 7 figures; Supplementary photometric data in zipped latex source as all_photometry.csv

The technique of mutual approximations accurately gives the central instant at the maximum apparent approximation of two moving natural satellites in the sky plane. This can be used in ephemeris fitting to infer the relative positions between satellites with high precision. Only the mutual phenomena -- occultations and eclipses -- may achieve better results. However, mutual phenomena only occur every six years in the case of Jupiter. Mutual approximations do not have this restriction and can be observed at any time along the year as long as the satellites are visible. In this work, we present 104 central instants determined from the observations of 66 mutual approximations between the Galilean moons carried out at different sites in Brazil and France during the period 2016--2018. For 28 events we have at least two independent observations. All telescopes were equipped with a narrow-band filter centred at 889 nm with a width of 15 nm to eliminate the scattered light from Jupiter. The telescope apertures ranged between 25--120 cm. For comparison, the precision of the positions obtained with classical CCD astrometry is about 100 mas, for mutual phenomena it can achieve 10 mas or less and the average internal precision obtained with mutual approximations was 11.3 mas. This new kind of simple, yet accurate observations can significantly improve the orbits and ephemeris of Galilean satellites and thus be very useful for the planning of future space missions aiming at the Jovian system., Comment: 12 pages, 7 figures

Made available in DSpace on 2021-06-25T11:43:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-01 FWF Austrian Science Fund DFG German Science Foundation project High Performance and Cloud Computing Group at the Zentrum fur Datenverarbeitung of the University of Tubingen, Germany state of Baden-Wurttemberg through bwHPC, Germany German Research Foundation (DFG) We present the second release of the now open source smoothed particle hydrodynamics code miluphcuda. The code is designed to run on Nvidia CUDA capable devices. It handles one to three dimensional problems and includes modules to solve the equations for viscid and inviscid hydrodynamical flows, the equations of continuum mechanics using SPH, and self-gravity with a Barnes-Hut tree. The covered material models include different porosity and plasticity models. Several equations of states, especially for impact physics, are implemented. The basic ideas of the numerical scheme are presented, the usage of the code is explained and its versatility is shown by means of different applications. The code is hereby publicly available. (C) 2020 Elsevier B.V. All rights reserved. Inst Astron & Astrophys, Morgenstelle 10, D-72076 Tubingen, Germany Univ Vienna, Dept Astrophys, Tuerkenschanzstr 17, A-1180 Vienna, Austria Technion Israel Inst Technol, Phys Dept, IL-3200002 Haifa, Israel South Ural State Univ, 9-115 Zababachina, Snezhinsk 456776, Chelyabinsk Reg, Russia Sao Paulo State Univ, BR-01049010 Guaratingueta, SP, Brazil Aix Marseille Univ, 3 Pl Victor Hugo, F-13003 Marseille, France Johannes Kepler Univ Linz, Inst Machine Learning, Altenberger Str 69, A-4040 Linz, Austria Sao Paulo State Univ, BR-01049010 Guaratingueta, SP, Brazil FWF Austrian Science Fund: S 11603-N16 DFG German Science Foundation project: 398488521 German Research Foundation (DFG): INST 37/935-1 FUGG

Made available in DSpace on 2018-12-11T17:35:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The Cassini spacecraft found a new and unique ring that shares the trajectory of Janus and Epimetheus, co-orbital satellites of Saturn. Performing image analysis, we found this to be a continuous ring. Its width is between 30% and 50% larger than previously announced. We also verified that the ring behaves like a firefly. It can only be seen from time to time, when Cassini, the ring, and the Sun are arranged in a particular geometric configuration, in very high phase angles. Otherwise, it remains in the dark, invisible to Cassini's cameras. Through numerical simulations, we found a very short lifetime for the ring particles, less than a couple of decades. Consequently, the ring needs to be constantly replenished. Using a model of particle production due to micrometeorites impacts on the surfaces of Janus and Epimetheus, we reproduce the ring, explaining its existence and the firefly behavior. São Paulo State University - UNESP Grupo de Dinâmica Orbital and Planetologia Universidade Federal Do Paraná UFPr PR São Paulo State University - UNESP Grupo de Dinâmica Orbital and Planetologia FAPESP: 2011/08171-3 FAPESP: 2016/24561-0

Made available in DSpace on 2018-12-11T16:53:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-04-21 The G ring arc hosts the smallest satellite of Saturn, Aegaeon, observed with a set of images sent by Cassini spacecraft. Along with Aegaeon, the arc particles are trapped in a 7:6 corotation eccentric resonance with the satellite Mimas. Due to this resonance, both Aegaeon and the arc material are confined to within 60° of corotating longitudes. The arc particles are dust grains which can have their orbital motions severely disturbed by the solar radiation force. Our numerical simulations showed that Aegaeon is responsible for depleting the arc dust population by removing them through collisions. The solar radiation force hastens these collisions by removing most of the 10 μm sized grains in less than 40 yr. Some debris released from Aegaeon's surface by meteoroid impacts can populate the arc. However, it would take 30 000 yr for Aegaeon to supply the observed amount of arc material, and so it is unlikely that Aegaeon alone is the source of dust in the arc. Univ. Estadual Paulista -UNESP Grupo de Dinâmica Orbital e Planetologia Univ. Estadual Paulista -UNESP Grupo de Dinâmica Orbital e Planetologia

In 2014, the discovery of two well-defined rings around the Centaur (10199) Chariklo were announced. This was the first time that such structures were found around a small body. In 2015, it was proposed that the Centaur (2060) Chiron may also have a ring. In a previous study, we analyzed how close encounters with giant planets would affect the rings of Chariklo. The most likely result is the survival of the rings. In the present work, we broaden our analysis to (2060) Chiron. In addition to Chariklo, Chiron is currently the only known Centaur with a presumed ring. By applying the same method as \cite{araujo2016}, we performed numerical integrations of a system composed of 729 clones of Chiron, the Sun, and the giant planets. The number of close encounters that disrupted the ring of Chiron during one half-life of the study period was computed. This number was then compared to the number of close encounters for Chariklo. We found that the probability of Chiron losing its ring due to close encounters with the giant planets is about six times higher than that for Chariklo. Our analysis showed that, unlike Chariklo, Chiron is more likely to remain in an orbit with a relatively low inclination and high eccentricity. Thus, we found that the bodies in Chiron-like orbits are less likely to retain rings than those in Chariklo-like orbits. Overall, for observational purposes, we conclude that the bigger bodies in orbits with high inclinations and low eccentricities should be prioritized., Comment: 8 pages, 3 figures, accepted for publication in MNRAS

Among the current population of the 81 known trans-Neptunian binaries (TNBs), only two are in orbits that cross the orbit of Neptune. These are (42355) Typhon-Echidna and (65489) Ceto-Phorcys. In the present work, we focused our analyses on the temporal evolution of the Typhon-Echidna binary system through the outer and inner planetary systems. Using numer- ical integrations of the N-body gravitational problem, we explored the orbital evolutions of 500 clones of Typhon, recording the close encounters of those clones with planets. We then analysed the effects of those encounters on the binary system. It was found that only 22% of the encounters with the giant planets were strong enough to disrupt the binary. This binary system has an ~3.6% probability of reaching the terrestrial planetary region over a time scale of approximately 5.4 Myr. Close encounters of Typhon-Echidna with Earth and Venus were also registered, but the probabilities of such events occurring are low (~0.4%). The orbital evolution of the system in the past was also investigated. It was found that in the last 100 Myr, Typhon might have spent most of its time as a TNB crossing the orbit of Neptune. Therefore, our study of the Typhon-Echidna orbital evolution illustrates the possibility of large cometary bodies (radii of 76 km for Typhon and 42 km for Echidna) coming from a remote region of the outer Solar System and that might enter the terrestrial planetary region preserving its binarity throughout the journey., Comment: 10 pages, 8 figures

Impacts of micrometeoroids on the surfaces of the plutonian small satellites Nix and Hydra can generate dust particles. Even in this region so far from the Sun these tiny ejected particles are under the effects of the solar radiation pressure. In this work, we investigate the orbital evolution of the escaping ejecta from both the small satellites under the effects of the radiation pressure combined with the gravitational effects of Pluto, Charon, Nix and Hydra. The mass production rate of micron-sized dust particles generated by micrometeoroids hitting the satellites is obtained, and numerical simulations are performed to derive the lifetime of the ejecta. These pieces of information allow us to estimate the optical depth of a putative ring, which extends from the orbits of Nix to Hydra. The ejected particles, between the orbits of Nix and Hydra, form a wide ring of about 16 000 km. Collisions with the massive bodies and escape from the system are mainly determined by the effects of the solar radiation pressure. This is an important loss mechanism, removing 30 per cent of the initial set of 1 μm-sized particles in 1 yr. The surviving particles form a ring too faint to be detectable with the derived maximum optical depth of 4 × 10 −11 .

The Centaur population is composed by minor bodies wandering between the giant planets and that frequently perform close gravitational encounters with these planets, which leads to a chaotic orbital evolution. Recently, the discovery of two well-defined narrow rings was announced around the Centaur 10199 Chariklo. The rings are assumed to be in the equatorial plane of Chariklo and to have circular orbits. The existence a well-defined system of rings around a body in such perturbed orbital region poses an interesting new problem. Are the rings of Chariklo stable when perturbed by close gravitational encounters with the giant planets? Our approach to address this question consisted of forward and backward numerical simulations of 729 clones of Chariklo, with similar initial orbits, for a period of 100 Myrs. We found, on average, that each clone suffers along its lifetime more than 150 close encounters with the giant planets within one Hill radius of the planet in question. We identified some extreme close encounters able to significantly disrupt or to disturb the rings of Chariklo. About 3% of the clones lose the rings and about 4% of the clones have the ring significantly disturbed. Therefore, our results show that in most of the cases (more than 90%) the close encounters with the giant planets do not affect the stability of the rings in Chariklo-like systems. Thus, if there is an efficient mechanism that creates the rings, then these structures may be common among these kinds of Centaurs., Comment: 11 pages. Accepted for publication in APj

Two new companions to the Pluto-Charon binary system have been detected in 2005 by Weaver et al. These small satellites, named Nix and Hydra, are located beyond Charon's orbit. Although they are small when compared to Charon, their gravitational perturbations can decrease the stability of the external region (beyond Charon's orbit). The dynamical structure of this external region is analysed by numerically simulating a sample of particles under the gravitational effects of Pluto, Charon, Nix and Hydra. As expected the effects of Nix and Hydra decrease the external stable region. Agglomerates of particles can survive even after 10 5 orbital periods of the binary in some regions, such as coorbital to Nix and Hydra and between their orbits. We also analysed the effects of hypothetical satellites on the orbital evolution of Nix and Hydra in order to constrain an upper limit size. Some hypothetical satellites can be coorbital to Nix or Hydra without provoking any significant gravitational effects on them.

The Cassini-Huygens arrival into the Saturnian system brought a large amount of data about the satellites and rings. Two diffuse rings were found in the region between the A ring and Prometheus. R/2004 S1 is coorbital to Atlas and R/2004 S2 is close to Prometheus. In this work we analysed the closest approach between Prometheus and both rings. As a result we found that the satellite removes particles from R/2004 S2 ring. Long-term numerical simulations showed that some particles can cross the F ring region . The well known region of the F ring, where small satellites are present and particles are being taking from the ring, gains a new insight with the presence of particles from R/2004 S2 ring. The computation of the Lyapunov Characteristic Exponent reveled that the R/2004 S2 ring lies in a chaotic region while R/2004 S1 ring and Atlas are in a stable region. Atlas is responsible for the formation of three regimes in the R/2004 S1 ring, as expected for a satellite embedded in a ring.

Hitherto, rings have been found exclusively around the four giant planets in the Solar System. Rings are natural laboratories in which to study dynamical processes analogous to those that take place during the formation of planetary systems and galaxies. Their presence also tells us about the origin and evolution of the body they encircle. Here we report observations of a multichord stellar occultation that revealed the presence of a ring system around (10199) Chariklo, which is a Centaur-that is, one of a class of small objects orbiting primarily between Jupiter and Neptune-with an equivalent radius of 124â â 9â kilometres (ref. 2). There are two dense rings, with respective widths of about 7 and 3 kilometres, optical depths of 0.4 and 0.06, and orbital radii of 391 and 405 kilometres. The present orientation of the ring is consistent with an edge-on geometry in 2008, which provides a simple explanation for the dimming of the Chariklo system between 1997 and 2008, and for the gradual disappearance of ice and other absorption features in its spectrum over the same period. This implies that the rings are partly composed of water ice. They may be the remnants of a debris disk, possibly confined by embedded, kilometre-sized satellites. © 2014 Macmillan Publishers Limited. Fil: Braga Ribas, F.. Observatório Nacional; Brasil Fil: Sicardy, B.. Universite Pierre et Marie Curie; Francia Fil: Ortiz, J.L.. Consejo Superior de Investigaciones Científicas; España Fil: Snodgrass, C.. Max Planck Institute for Solar System Research; Alemania Fil: Roques, F.. Universite Pierre et Marie Curie; Francia Fil: Vieira Martins, R.. Centre National de la Recherche Scientifique; Francia. Universidade Federal do Rio de Janeiro; Brasil Fil: Camargo, J.I.B.. Ministério de Ciencia, Tecnologia e Innovacao. Observatorio Nacional; Brasil Fil: Assafin, M.. Universidade Federal do Rio de Janeiro; Brasil Fil: Duffard, R.. Consejo Superior de Investigaciones Científicas; España Fil: Jehin, E.. Université de Liège; Bélgica Fil: Pollock, J.. Appalachian State University; Estados Unidos Fil: Leiva, R.. Pontificia Universidad Católica de Chile; Chile. Universidad Católica de Chile; Chile Fil: Emilio, M.. Universidade Estadual de Ponta Grossa; Brasil Fil: MacHado, D.I.. Universidade Estadual Do Oeste Do Pará; Brasil Fil: Colazo, C.. Universidad Nacional de Córdoba; Argentina. Ministerio de Educación de la Provincia de Córdoba; Argentina Fil: Lellouch, E.. Universite Pierre et Marie Curie; Francia Fil: Skottfelt, J.. University of Copenhagen; Dinamarca. Geological Museum; Dinamarca Fil: Gillon, M.. Université de Liège; Bélgica Fil: Ligier, N.. Universite Pierre et Marie Curie; Francia Fil: Maquet, L.. Universite Pierre et Marie Curie; Francia Fil: Benedetti Rossi, G.. Ministério de Ciencia, Tecnologia e Innovacao. Observatorio Nacional; Brasil Fil: Gomes, A. Ramos. Universidade Federal do Rio de Janeiro; Brasil Fil: Kervella, P.. Universite Pierre et Marie Curie; Francia Fil: Monteiro, H.. Instituto de Física e Química; Brasil Fil: Sfair, R.. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Moutamid, M. El. Universite Pierre et Marie Curie; Francia. Centre National de la Recherche Scientifique; Francia Fil: Tancredi, G.. Observatorio Astronómico Los Molinos; Uruguay. Universidad de la República; Uruguay Fil: Spagnotto, J.. Observatorio El Catalejo la Pampa; Argentina Fil: Maury, A.. San Pedro de Atacama Celestial Explorations; Chile Fil: Morales, N.. Consejo Superior de Investigaciones Científicas; España Fil: Gil Hutton, Ricardo Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico ; Argentina Fil: Roland, S.. Observatorio Astronómico Los Molinos; Uruguay Fil: Ceretta, A.. Universidad de la República; Uruguay. Observatorio del IPA; Uruguay Fil: Gu, S.-H.. Chinese Academy of Sciences; República de China Fil: Wang, X.-B.. Chinese Academy of Sciences; República de China Fil: Harpsøe, K.. University of Copenhagen; Dinamarca. Geological Museum; Dinamarca Fil: Rabus, M.. Universidad Católica de Chile; Chile. Pontificia Universidad Católica de Chile; Chile. Max Planck Institute for Astronomy; Alemania Fil: Manfroid, J.. Université de Liège; Bélgica Fil: Opitom, C.. Université de Liège; Bélgica Fil: Vanzi, L.. Pontificia Universidad Católica de Chile; Chile. Universidad Católica de Chile; Chile Fil: Mehret, L.. Universidade Estadual de Ponta Grossa; Fil: Lorenzini, L.. Polo Astronômico Casimiro Montenegro Filho; Brasil Fil: Schneiter, E.M.. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Iate-conicet; Argentina Fil: Melia, R.. Universidad Nacional de Córdoba; Argentina Fil: Lecacheux, J.. Universite Pierre et Marie Curie; Francia Fil: Colas, F.. Centre National de la Recherche Scientifique; Francia Fil: Vachier, F.. Centre National de la Recherche Scientifique; Francia Fil: Widemann, T.. Universite Pierre et Marie Curie; Francia Fil: Almenares, L.. Universidad de la República; Uruguay. Observatorio Astronomico Los Molinos; Uruguay Fil: Sandness, R.G.. San Pedro de Atacama Celestial Explorations; Chile Fil: Char, F.. Universidad de Antofagasta; Chile Fil: Perez, V.. Universidad de la República; Uruguay. Observatorio Astronomico Los Molinos; Uruguay Fil: Lemos, P.. Universidad de la República; Uruguay. Observatorio Astronomico Los Molinos; Uruguay Fil: Martinez, N.. Universidad de la República; Uruguay. Observatorio Astronomico Los Molinos; Uruguay Fil: Jørgensen, U.G.. Universidad de Copenhagen; Dinamarca Fil: Dominik, M.. University of St. Andrews; Reino Unido Fil: Roig, F.. Ministério de Ciencia, Tecnologia e Innovacao. Observatorio Nacional; Brasil Fil: Reichart, D.E.. University of North Carolina; Estados Unidos Fil: Lacluyze, A.P.. University of North Carolina; Estados Unidos Fil: Haislip, J.B.. University of North Carolina; Estados Unidos Fil: Ivarsen, K.M.. University of North Carolina; Estados Unidos Fil: Moore, J.P.. University of North Carolina; Estados Unidos Fil: Frank, N.R.. University of North Carolina; Estados Unidos Fil: Garcia Lambas, Diego Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentina

Image photometry reveals that the F ring is approximately twice as bright during the Cassini tour as it was during the Voyager flybys of 1980 and 1981. It is also three times as wide and has a higher integrated optical depth. We have performed photometric measurements of more than 4,800 images of Saturn's F ring taken over a five-year period with Cassini's Narrow Angle Camera. We show that the ring is not optically thin in many observing geometries and apply a photometric model based on single-scattering in the presence of shadowing and obscuration, deriving a mean effective optical depth tau = 0.033. Stellar occultation data from Voyager PPS and Cassini VIMS validate both the optical depth and the width measurements. In contrast to this decades-scale change, the baseline properties of the F ring have not changed significantly from 2004 to 2009. However, we have investigated one major, bright feature that appeared in the ring in late 2006. This transient feature increased the ring's overall mean brightness by 84% and decayed with a half-life of 91 days., Comment: 27 pages, 12 figures, 2 tables

International audience; The light curves of mutual eclipses and occultations between the natural satellites of a planet allow us to obtain high-precision position and relative motion from differential photometry, enough to detect weak orbital disturbing forces, such as tidal forces. The observations are made during the equinoxes of the planet.We studied 25 light curves observed in Brazil during the 2009 campaign of the Galilean satellites’ mutual phenomena. A narrow-band filter centred at 890 nm was used, strongly attenuating the Jupiter's scattered light. We fitted the occultation and eclipse light curves using semi-analytical models that take into account the gradual decrease of light over the shadow, the solar limb darkening and the solar phase angle. The Oren–Nayar reflexive model was used to map the inhomogeneous light scattering on the surface of the satellites. For the first time it is used in a work about mutual events. Here, we include the study that made us decide for this model.We measured the impact parameter, relative velocity and central instant with average precisions of 7.46 km (2.2 mas), 0.08 km s−1 (0.02 mas s−1) and 0.42 s (6.13 km), respectively. The fit precision of the normalized light-curve fluxes ranged between 0.4 and 4.4 per cent.

Made available in DSpace on 2013-08-28T14:07:39Z (GMT). No. of bitstreams: 1 WOS000270638600038.pdf: 543187 bytes, checksum: 28c619d7ae59fdd70481d560fb02a2a8 (MD5) Made available in DSpace on 2013-09-30T18:11:18Z (GMT). No. of bitstreams: 2 WOS000270638600038.pdf: 543187 bytes, checksum: 28c619d7ae59fdd70481d560fb02a2a8 (MD5) WOS000270638600038.pdf.txt: 34751 bytes, checksum: 0853c739ecfc9d0c00fcbd666a8c125a (MD5) Previous issue date: 2009-10-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:28:02Z No. of bitstreams: 2 WOS000270638600038.pdf: 543187 bytes, checksum: 28c619d7ae59fdd70481d560fb02a2a8 (MD5) WOS000270638600038.pdf.txt: 34751 bytes, checksum: 0853c739ecfc9d0c00fcbd666a8c125a (MD5) Made available in DSpace on 2014-05-20T13:28:02Z (GMT). No. of bitstreams: 2 WOS000270638600038.pdf: 543187 bytes, checksum: 28c619d7ae59fdd70481d560fb02a2a8 (MD5) WOS000270638600038.pdf.txt: 34751 bytes, checksum: 0853c739ecfc9d0c00fcbd666a8c125a (MD5) Previous issue date: 2009-10-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The mu and nu rings of Uranus form a secondary ring-moon system with the satellites Puck, Mab, Portia, and Rosalind. These rings are tenuous and dominated by micrometric particles, which can be strongly disturbed by dissipative forces, such as the solar radiation pressure. In the region of these rings, the solar radiation force and the planetary oblateness change the orbital evolution of these dust particles significantly. In this work, we performed a numerical analysis of the orbital evolution of a sample of particles with radii of 1, 3, 5, and 10 mu m under the influence of these perturbations, combined with the gravitational interaction with the close satellites. As expected, the Poynting-Robertson component of the solar radiation force causes the collapse of the orbits on a timescale between 3.1 x 10(5) and 3.6 x 10(6) years, while the radiation pressure causes an increase in the eccentricity of the particles. The inclusion of Uranus's oblateness prevents a large variation in the eccentricity, confining the particles in the region of the rings. The encounters with the close satellites produce variations in the semimajor axis of the particles, leading them to move inward and outward within the ring region. These particles can either remain within the region of the rings or collide with a neighbouring satellite. The number of collisions depends on the size of both the particles and the satellites, and the radial width of the ring. For the time span analysed, the percentage of particles that collide with a satellite varies from 43% to 94% for the. ring, and from 12% to 62% for the mu ring. Our study shows that all collisions with Portia and Rosalind have the value of impact velocity comparable to the escape velocity, which could result in the deposition of material onto the surface of the satellite. Collisions between Puck and particles larger than 1 mu m also occur at an impact velocity comparable to the value of the escape velocity. The exception is Mab, which is hit by particles with velocities several times larger than the escape velocity. These collisions are energetic enough to eject material and supply material to the mu ring. However, only a few particles (3%) collide with the surface of the satellite Mab at such a velocity. UNESP São Paulo State Univ, BR-12516410 Guaratingueta, SP, Brazil UNESP São Paulo State Univ, BR-12516410 Guaratingueta, SP, Brazil

Made available in DSpace on 2013-08-28T14:13:41Z (GMT). No. of bitstreams: 1 WOS000266112600031.pdf: 739262 bytes, checksum: 3ab2b63aff9c6d365c9d69a43479acfc (MD5) Made available in DSpace on 2013-09-30T18:11:17Z (GMT). No. of bitstreams: 2 WOS000266112600031.pdf: 739262 bytes, checksum: 3ab2b63aff9c6d365c9d69a43479acfc (MD5) WOS000266112600031.pdf.txt: 22922 bytes, checksum: 3e0499754c79d37fa6a7d9dc2a6b462a (MD5) Previous issue date: 2009-06-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:28:00Z No. of bitstreams: 2 WOS000266112600031.pdf: 739262 bytes, checksum: 3ab2b63aff9c6d365c9d69a43479acfc (MD5) WOS000266112600031.pdf.txt: 22922 bytes, checksum: 3e0499754c79d37fa6a7d9dc2a6b462a (MD5) Made available in DSpace on 2014-05-20T13:28:00Z (GMT). No. of bitstreams: 2 WOS000266112600031.pdf: 739262 bytes, checksum: 3ab2b63aff9c6d365c9d69a43479acfc (MD5) WOS000266112600031.pdf.txt: 22922 bytes, checksum: 3e0499754c79d37fa6a7d9dc2a6b462a (MD5) Previous issue date: 2009-06-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Saturn's F ring has been the subject of study due to its peculiar structure and the proximity to two satellites, named Prometheus (interior) and Pandora (exterior to the ring), which cause perturbations to the ring particles. Early results from Voyager data have proposed that the ring is populated with centimetre- and micrometre-sized particles. The Cassini spacecraft also detected a less dense part in the ring with width of 700 km. Small particles suffer the effects of solar radiation. Burns et al. showed that due to effects of one component of the solar radiation, the Poynting-Robertson drag, a ring particle will decay in the direction of the planet in a time much shorter than the age of the Solar system. In this work, we have analysed a sample of dust particles (1, 3, 5 and 10 mu m) under the effects of solar radiation, the Poynting-Robertson drag and the radiation pressure components and the gravitational effects of the satellites Prometheus and Pandora. In this case, the high increase of the eccentricity of the particles leads almost all of them to collide with the outer edge of the A ring. The inclusion of the oblateness of Saturn in this system significantly changes the outcome, since the large variation of the eccentricity is reduced by the oblateness effect. As a result, there is an increase in the lifetime of the particle in the envelope region. Our results show that even the small dust particles, which are very sensitive to the effects of solar radiation, have an orbital evolution similar to larger particles located in the F ring. The fate of all particles is a collision with Prometheus or Pandora in less than 30 years. on the other hand, collisions of these particles with moonlets/clumps present in the F ring could change this scenario. UNESP São Paulo State Univ, BR-12516410 Guaratingueta, SP, Brazil UNESP São Paulo State Univ, BR-12516410 Guaratingueta, SP, Brazil

Context. We previously analysed how the solar radiation force combined with the planetary oblateness changes the orbital evolution of a sample of dust particles located at the secondary ring system of Uranus. Both effects combined with the gravitational perturbations of the close satellites lead to the depletion of these dust particles through collisions on the surfaces of these satellites on a timescale of hundreds of years. Aims. In this work we investigate if the impacts of interplanetary dust particles (IDPs) onto Mab’s surface can produce sufficient particles to replenish the μ ring population. Methods. We first analysed through numerical simulations the evolution of a sample of particles ejected from the surface of Mab and computed the lifetime of the grains when the effects of the solar radiation pressure and the planetary oblateness are taken into account. Then we estimated the mass production rate due to the impacts of IDPs following a previously established algorithm, and used this value to determine the time necessary to accumulate an amount of particles comparable with the mass of the μ ring. Results. Based on an estimate of the flux of interplanetary particles and on the surface properties of Mab it is expected that the satellite supplies material to the ring at a rate of ∼ 3g /s. Meanwhile, our numerical model showed that the ejected particles are removed from the system through collisions with the satellite, and the mean lifetime of the grains may vary from 320 to 1500 years, depending on the radius of the particle. Conclusions. The time necessary to accumulate the mass of the μ ring via ejection from Mab is much shorter than the mean lifetime of the particles, and a stationary regime is not reached. If the ring is kept in a steady state, other effects such as the electromagnetic force and/or the existence of additional bodies may play a significant role in the dust balance, but the current lack of information about the environment renders modelling these effects unfeasible.

Universidade Tecnológica Federal do Paraná (UTFPR) O estudo dos pequenos corpos do Sistema Solar pode revelar informações sobre as circunstâncias de formação do sistema. Dentre estes objetos, os Troianos despertam especial interesse. Encontrados nos pontos de equilíbrio de Lagrange L4 e L5 ao longo da órbita de alguns planetas, possivelmente preservam algumas características que remontam a formação do Sistema Solar (NESVORNY, 2021). Este trabalho buscou refinar os conhecimentos a respeito da forma de (624) Hektor, o maior Troiano do planeta Júpiter, por meio da técnica de inversão de curva de luz (KAASALAINEN et al., 1992a,b) combinada com ocultações estelares. Situado no ponto L4, (624) Hektor foi descoberto em 1907 e possui diâmetro aparente estimado em 233 km (MARCHIS et al., 2006; HANUS, 2015; ROZEHNAL et al., 2016). Ao todo analisamos 93 curvas de luz de rotação observadas entre os anos de 1957 e 2020, sendo que as mais recentes foram obtidas neste trabalho, a partir de observações realizadas no Observatório do Pico dos Dias. Por meio da análise destes dados foi possível obter o período rotacional de P = 6,920509 h ± 0,000001 h, que foi utilizado na técnica de inversão de curva de luz, procedimento que considera dentre outras propriedades o espalhamento da superfície do objeto e suas características rotacionais. Tal procedimento foi realizado com o uso do software Convexinv (ĎURECH, 2010) e os resultados obtidos permitiram estimar as coordenadas do polo de rotação (λ = 332° ± 10° e = -27° ± 10°) e um possível formato convexo representado por um poliedro com 1.018 faces e 2.032 vértices, porém de volume adimensional. Estes resultados foram utilizados como parâmetro para o software ADAM (VIIKINKOSKI, 2015), que combinou as 93 curvas de luz com 10 cordas de ocultação obtidas em 2019 e outras 5 obtidas em 2020 pelo Grupo do Rio. A combinação das curvas de luz com as ocultações permitiu refinar a determinação da forma, e o modelo não convexo gerado, com 800 faces e 402 vértices, com polo λ = 334° ± 10° e = -25° ± 10°, e diâmetro volumétrico equivalente de 193 km ± 20 km, o que permitiu estimar a densidade de (624) Hektor como ρ = 2,11 g/cm³ + 0,65. Estes resultados são comparados com aqueles já disponíveis na literatura e, em especial, com o formato bilobal sugerido por Marchis et al. (2006), que não é compatível com as cordas de ocultação observadas e, portanto, é refutado pelos resultados deste trabalho. Espera-se que este estudo possa contribuir para a pesquisa de pequenos corpos ao apresentar meios de determinar características físicas precisas para estes objetos, colaborando assim para o esforço da compreensão sobre as condições primordiais na qual este e possivelmente outros objetos se formaram e evoluíram. Espera-se ainda que os resultados possam ser somados àqueles que serão obtidos pela missão Lucy (NASA), de lançamento previsto para outubro de 2021, que estudará outros 6 Troianos de Júpiter entre 2025 e 2033. The study of the Solar System’s small bodies can reveal information about the circumstances of the system’s formation. Among these objects, the Trojans are of special interest. Found at the Lagrange equilibrium points L4 and L5 along the orbits of a planet, they possibly preserve some features that date back to the formation of the Solar System (NESVORNY, 2021). This work aims to refine the knowledge about the shape of (624) Hektor, the largest Trojan of the planet Jupiter, through the light curve inversion technique (KAASALAYEN et al., 1992a,b) combined with stellar occultations. Situated at point L4, (624) Hektor was discovered in 1907 and has an estimated diameter of 233 km (MARCHIS et al., 2006; HANUS, 2015; ROZEHNAL et al., 2016). We analyzed 93 rotational light curves observed between 1957 and 2020, being the most recent obtained during this work, based on observations carried out at the Pico dos Dias Observatory. Through the analysis of these data, it was possible to obtain the rotational period of P = 6.920509 h ± 0.000001 h, which was used in the light curve inversion technique, a procedure that considers, among other properties, the scattering of the object’s surface and its rotational characteristics. This procedure was performed using the Convexinv software (ĎURECH, 2010) and the results obtained allowed us to estimate the coordinates of the rotation pole (λ = 331.80° ± 10° and = -27.00° ± 10°) and a possible convex shape represented by a 1018 polyhedron faces and 2032 vertices, but with a dimensionless volume. These results were used as a parameter for the ADAM software (VIIKINKOSKI, 2015), which combined the 93 light curves with 10 chords from a stellar occultation observed in 2019 and another 5 obtained in 2020 by the Rio Group. The combination of light curves with the occultations chords allowed to refine the shape determination, and the non-convex model generated, with 800 faces and 402 vertices, with pole λ = 334° ± 10° and = -25° ± 10°, and equivalent volumetric diameter of 193 km ± 20 km, which allowed to estimate the density of (624) Hektor as ρ = 2.11 + 0.65 g/cm³. These results are compared with those already available in the literature and, in particular, with the bilobal format suggested by Marchis et al. (2006), which is not compatible with the observed occultation chords and, therefore, is refuted by the results of this work. We hoped that this study can contribute to the research of small bodies by presenting ways to determine precise physical characteristics for these irregular objects, thus contributing to the effort to understand the primordial conditions in which these and possibly other objects formed and evolved. It is also expected that these results add to those that will be obtained by the Lucy mission (NASA), scheduled for launch in October 2021, which will study other 6 Trojans of Jupiter between 2025 and 2033.

Os objetos Centauros são corpos menores do Sistema Solar que orbitam o Sol entre as órbitas de Júpiter e Netuno. O primeiro Centauro descoberto foi (2060) Chiron, provisoriamente designado como 1977 UB. Assim como outros Centauros descobertos posteriormente, Chiron apresentou atividade cometária e coma em observações nos anos 1988 e 1989, o que lhe rendeu também a designação de cometa (95/P Chiron). Em ocultações estelares ocorridas na década de 90, estruturas na região mais interna da coma foram interpretadas como jatos colimados de material sendo expelido pelo núcleo. Estruturas também foram observadas em uma ocultação em 2011, onde a simetria dessas estruturas em torno do centro de (2060) Chiron levantou a hipótese de que o objeto pode estar rodeado por sistema de anéis. Este trabalho contém a investigação sobre o tamanho, forma e a busca por estruturas no entorno do objeto Centauro (2060) Chiron nas curvas de luz de duas ocultações estelares nos últimos dois anos. Em 28 de Novembro de 2018, o Centauro (2060) Chiron ocultou uma estrela com magnitude G ∼ 17,2. Dados foram adquiridos com sucesso no Observatório Astronômico da África do Sul (SAAO), com uma detecção do núcleo do objeto. Com uma duração de 31,3 ± 0,2 segundos, o tamanho da corda foi estimado em 179,8 ± 1,4 km. Na ocultação estelar ocorrida em 08 de Setembro de 2019, (2060) Chiron ocultou uma estrela com magnitude G ∼ 16,5. As observações foram feitas em cinco locais distribuídos, dois na Bélgica e dois na França obtiveram sucesso, um telescópios na Espanha obteve uma corda negativa próxima a sombra do corpo. Como todos os telescópios no evento de 2019 eram de médio porte, os dados apresentaram baixa razão sinalruído e portanto não foi possível buscar por eventos secundários nas curvas de luz. Apesar disso, essa ocultação multi-cordas permitiu determinar restrições para o tamanho e forma do objeto. Neste trabalho, além de apresentarmos pela primeira vez restrições ao tamanho e forma de Chiron, usamos os dados obtidos na ocultação de 2018 para realizar uma busca pelos anéis propostos, determinar limites para a detecção de qualquer material ou outra estrutura no plano equatorial, ou difuso distribuido radialmente, orbitando (2060) Chiron. Centaurs are minor bodies in the Solar System that orbit the Sun between Jupiter and Neptune’s orbits. The first Centaur discovered was (2060) Chiron, when it received the provisional designation of 1977 UB. Like other Centaurs discovered later, Chiron exhibited cometary activity and coma in observations in the years 1988 and 1989, which also earned it the designation of a comet (95/P Chiron). In stellar occultations in the ’90s, structures in the inner coma were interpreted as collimated jets of material expelled by the nucleus. Symmetric structures around the center of (2060) Chiron were also observed in an occultation in 2011, raising the hypothesis that a ring system may surround the object. This work contains the investigation about the size, shape and the search for structures around the Centaur (2060) Chiron in the light curves of two stellar occultations in the last two years. On November 28, 2018, (2060) Chiron occulted a G ∼ 17.2 magnitude star. Data was successfully acquired at the South African Astronomical Observatory (SAAO) with the detection of the object’s nucleus. With a 31.3±0.2 seconds duration, the chord size is estimated at 179.8±1.4 km. In the stellar occultation on September 8, 2019, (2060) Chiron occulted a star with magnitude R ∼ 16.5. The observations were made in five sites in Europe; two positive ones in Belgium, two positive ones in France and one telescope in Spain obtained a negative chord close to the body’s shadow. As all telescopes were medium-sized, the data showed a low signal-to-noise ratio, só it was impossible to search for secondary events in the light curves of the 2019 event. Despite this, this multi-chord occultation allowed to constrains the size and shape of the object. In this work, in addition to presenting, for the first time, restrictions to the size and shape of Chiron, we use the data obtained in the 2018 occultation to perform a search for the proposed rings, determining limits for the detection of any material or other structure in the equatorial plane, or radially diffuse, orbiting (2060) Chiron.

Submitted by Tiago Francisco Lins Leal Pinheiro (francisco.pinheiro@unesp.br) on 2019-05-06T01:52:54Z No. of bitstreams: 1 mestrado.pdf: 3868742 bytes, checksum: 06c6e9e3c862a6459a8e89932c7c86fd (MD5) Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2019-05-06T11:43:25Z (GMT) No. of bitstreams: 1 pinheiro_tfll_me_guara.pdf: 3868742 bytes, checksum: 06c6e9e3c862a6459a8e89932c7c86fd (MD5) Made available in DSpace on 2019-05-06T11:43:25Z (GMT). No. of bitstreams: 1 pinheiro_tfll_me_guara.pdf: 3868742 bytes, checksum: 06c6e9e3c862a6459a8e89932c7c86fd (MD5) Previous issue date: 2019-03-08 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A estrela PDS110 (HD290380) com idade aproximada de 10 milhões de anos, apresentou dois eclipses ocorridos em 2008 e 2011, com duração de 25 dias e queda de aproximadamente 26 % na luminosidade da estrela. Outra estrela J1407 (1SWASP J140747.93-39454.6) apresentou uma complexa série de eclipses com 56 dias de duração. As hipóteses dadas a esses dois eventos foram a passagem da borda de um disco planetário ou um disco circunstelar de uma anã marrom. Neste trabalho foi analisada a natureza desses possíveis sistemas de anéis ao redor de um exoplaneta gigantesco não observado, que teria ocultado essas estrelas. Para estudar o sistema PDS110b, devido ao grande número de variáveis envolvidas ainda desconhecidas neste problema como, por exemplo, massa e excentricidade do planeta, inclinação e extensão do disco, foram criados diversos modelos numéricos considerando a interação gravitacional entre a estrela, o planeta e a partícula do anel. Desta forma foi possível refinar os intervalos dos parâmetros predeterminados através dos dados observacionais, que seriam compatíveis com o eclipse observado. Os resultados indicam que provavelmente os eclipses teriam ocorrido por um planeta com massa entre 50 e 70 MJup, em uma orbita quase circular (ePDS110b < 0,05) e o semieixo maior de 2 ua. O sistema de anel ao redor do PDS110b, teria uma extensão radial de ~ 0,2 ua, significativamente maior que o raio de Roche do planeta e um forte indicio da presença de satélites. Ao analisar o sistema de anéis do J1407b, após a exclusão de algumas propostas do corpo eclipsante ser uma estrela secundária, os estudos propõem um extenso sistema de anéis, formado por no mínimo 37 diferentes anéis e uma possível exolua com massa proporcional a Terra, localizada em uma falha observada em 0,4 ua de distância do planeta. Uma abordagem semelhante a realizada no sistema PDS110b foi aplicada também para o J1407b, assumindo a hipótese que eclipse se deu pela passagem de um exoplaneta gigante gasoso de 10 a 100 MJup e semieixo maior > 3 ua. Os melhores resultados mostram que J1407b possivelmente tem uma massa maior que 50 MJup, aJ1407b = [4 - 5,6] ua, período orbital entre 8,3 e 11,6 anos e eJ1407b = [0,3 - 0,4]. O anel tem 0,3 ua de extensão radial, muito maior que o raio de Roche do planeta, o que colabora com a explicação da formação de satélites nas suas falhas. The star PDS110 (HD290380) is approximately 10 millions years old, underwent two eclipses observed in 2008 and 2011 in the surrounding 25 days with a depth 26 % in the star's luminosity. Other star J1407 (1SWASP J140747.93-39454.6) underwent a complex series of eclipses that lasted 56 days. The hypothesis could explain those events are the transit of the edge one disc circumplanetary or circumstelar (brown dwarf). In this work, we analyzed the nature of a possible ring system around these giant exoplanets would have occulted the star. To study the PDS110b system, in the reason to the large number of unknown variable involved in this problem like: mass and the eccentricity of the PDS110b, inclination and size of the disc, we created a several numerical models considering the only gravitational interactions between the star, the planet and the particle of the ring. We managed to restrict the interval of the parameters predetermined by the observational data. The best models indicate a planet's mass between [50 - 70] MJup, in the quasi circular orbit (ePDS110b < 0,05) and semi major axis of 2 ua. The ring system around the PDS110b, probably has ~ 0,2 ua of radial extension. To analyze the ring system around J1407b, after excluded some proposals of the eclipsing body to be a secundary star, the studies propose an extensive ring system with radius of 0,6 ua, formed by at least 37 different rings and one possible exomoon with mass proportional to Earth, located at the gap observed at 0.4 ua from the planet. A similar approach to that carried out in the PDS110b system we also applied to J1407b, assuming the hypothesis that eclipse happened by the transit of an gaseous giant exoplanet from 10 to 100 MJup and a semi major axis axis > 2,2 ua. The best show that J1407b probably has a mass > 50 MJup, aJ1407b = [4 - 5,6] ua, orbital period between 8,3 and 11,6 years and eJ1407b = [0,2 - 0,4]. The ring has 0.3 ua of radial extension, much larger than the radius of Roche of the planet, which collaborates with the explanation of the formation of satellites in their gaps. CAPES: 001

Submitted by Victor Corrêa Lattari (victor.lattari@unesp.br) on 2019-04-24T23:13:44Z No. of bitstreams: 1 dissertacao-victor.pdf: 8106747 bytes, checksum: 36602ebcf0893a17f916457a12b48aa6 (MD5) Rejected by Pamella Benevides Gonçalves null (pamella@feg.unesp.br), reason: Solicitamos que realize correções na submissão seguindo as orientações abaixo: Após apresentar o TCC e realizar as correções da banca. Solicitar a ficha catalográfica http://www2.feg.unesp.br/#!/biblioteca/trabalho-conclusao-de-curso/ depois acrescentar ao trabalho após a folha de rosto. Agradecemos a compreensão on 2019-04-25T12:55:45Z (GMT) Submitted by Victor Corrêa Lattari (victor.lattari@unesp.br) on 2019-04-25T20:09:00Z No. of bitstreams: 1 dissertacao-victor.pdf: 8106747 bytes, checksum: 36602ebcf0893a17f916457a12b48aa6 (MD5) Rejected by Pamella Benevides Gonçalves null (pamella@feg.unesp.br), reason: Solicitamos que realize correções na submissão seguindo as orientações abaixo: Solicitar a ficha catalográfica http://www2.feg.unesp.br/#!/biblioteca/trabalho-conclusao-decurso/ depois acrescentar ao trabalho após a folha de rosto. Agradecemos a compreensão on 2019-04-26T15:28:21Z (GMT) Submitted by Victor Corrêa Lattari (victor.lattari@unesp.br) on 2019-04-29T00:55:01Z No. of bitstreams: 1 dissertacao.pdf: 8732417 bytes, checksum: b4ea096042f5e6dfea8ac8452122a76a (MD5) Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2019-04-29T11:40:01Z (GMT) No. of bitstreams: 1 lattari_vc_me_guara.pdf: 8732417 bytes, checksum: b4ea096042f5e6dfea8ac8452122a76a (MD5) Made available in DSpace on 2019-04-29T11:40:01Z (GMT). No. of bitstreams: 1 lattari_vc_me_guara.pdf: 8732417 bytes, checksum: b4ea096042f5e6dfea8ac8452122a76a (MD5) Previous issue date: 2019-02-28 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A formação de alguns arcos dos anéis planetários pode estar relacionada às colisões de partículas interplanetárias com seus satélites, fragmentando-os e produzindo corpos menores. De modo sucessivo, estes fragmentos podem sofrer novas colisões e eventualmente gerar partículas de poeira. Por outro lado, os corpos macroscópicos (da ordem de metros) imersos no anel podem colidir entre si e aglutinar- se de modo a gerar novos objetos maiores. A existência destes arcos é creditada a presença de um satélite perturbador que os confina em um ressonância de corrotação. No caso do arco do anel G de Saturno, este é confinado por uma uma ressonância excêntrica 7:6 de corrotação com o satélite Mimas. Hedman et al. (2010) citam que o arco do anel G é majoritariamente composto por partículas da ordem de micrômetros. Neste caso, as forças perturbativas, tais como a pressão de radiação e a força eletromagnéticas, são significativas e tendem a reduzir o tempo de vida destas partículas nesta região. Para explicar a estabilidade do arco Hedman et al. (2010) utilizaram o pequeno satélite Aegaeon (imerso no arco) que poderia ser uma fonte do material das partículas micrométricas imersas no arco via colisões de partículas interplanetárias com Aegaeon. Entretanto, Madeira et al. (2018) exploraram o efeito da pressão de radiação solar e mostraram que o tempo de vida das partículas micrométricas no arco é menos de 40 anos e que o satélite Aegaeon não poderia ser fonte de material e manter a quantidade de poeira no arco via colisões de partículas interplanetárias. Isto, levantou a hipótese de que outro mecanismo de reposição de poeira deveria ser considerado. Tal mecanismo pode ser explicado a partir dados do instrumento LEMMS (Magnetospheric Imaging Instrument’s LowEnergy, em português "Instrumento de Imagem Magnetosférica para Baixas Energias") da sonda Casssini que detectou uma queda mais acentuada na energia dos elétrons no arco, inferindo que deva existir uma população de corpos da ordem de metros imersos no arco. Neste trabalho será analisado o comportamento de corpos macroscópicos existentes em arcos planetários investigando suas evoluções temporais e os possíveis satélites a serem criados investigando a influência do raio físico e da densidade do número de corpos. Além disso, será analisada a produção de poeira gerada devido a colisões super-catastróficas entre os corpos macroscópicos com o objetivo de verificar se estes podem ser o mecanismo de reposição de poeira no arco. Por fim, neste trabalho foi mostrado que é possível manter a população de poeira no arco do anel G através das colisões super-catastróficas entre os corpos macroscópicos imersos no arco e com isso manter o sistema estável por mais de 300 anos e que o satélite Aegaeon não é relevante para a produção de poeira do arco. Some planetary rings exhibit denser regions called arcs, and the existence of these arcs is credited by the presence of a disturbing satellite that confines the particles in a corotation resonance. The formation of the planetary ring arc can be related with the collisions between interplanetary particles with an embedded satellite, or the break up of a moon into minor bodies. Successively, these bodies may experience new collisions that eventually create dust particles. Meanwhile, the macroscopic bodies can collide among themselves and merge, resulting in large bodies. For the Saturn’s G ring’s arc, it is confined by a 7:6 corotation resonance with the satellite Mimas. Hedman et al. (2010) showed this arc is composed mostly of micrometers particles, a configuration that perturbative forces are significant and decrease the lifetime of the structure. To explain the stability of this arc, they proposed that the satellite Aegaeon could be a source of the material of the dust by collisions within interplanetary particles. However, Madeira et al. (2018) studied the solar radiation pressure and showed that the lifetime of the particles in less than 40 years and that the satellite Aegaeon cannot be a source. Therefore, another mechanism is necessary to explain the arc. To do so, one can use information derived by the LEMMS (Magnetospheric Imaging Instrument’s LowEnergy), an instrument from that Cassini spacecraft that detected an energy drop from electrons in this region, inferring that there must be a population of bodies of the order of meters immersed in the G ring arc. In this work, we analyzed the dynamics of macroscopic bodies immersed in planetary arcs, studying through numerical simulations their temporal evolution and the likelihood of moon formation. Moreover, it will be analyzed the dust produced by super-catastrophic collisions between these bodies, aiming to create a stable system and verify if this mechanism can be sufficient to maintain the dust detected in the G ring arc. Our results indicate that it is possible to keep the dust population in the arc through the super-catastrophic collisions between the macroscopic bodies immersed in the arc and keep the system stable for more than 300 years. Furthermore, we conclude that Aegaeon is not relevant to the production of arc dust. CAPES: 1684418

Submitted by EDUARDO CARVALHO PINHEIRO (eduardouefsfisica@gmail.com) on 2018-06-16T14:41:39Z No. of bitstreams: 1 EDUARDO C PINHEIRO (CORRIGIDO).pdf: 8170783 bytes, checksum: 56414824629dcd48a286b9b0d37a40b3 (MD5) Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2018-06-18T13:15:27Z (GMT) No. of bitstreams: 1 pinheiro_ec_me_guara_par.pdf: 298459 bytes, checksum: d05f4a0861c9d18f714319dce0838f83 (MD5) Made available in DSpace on 2018-06-18T13:15:27Z (GMT). No. of bitstreams: 1 pinheiro_ec_me_guara_par.pdf: 298459 bytes, checksum: d05f4a0861c9d18f714319dce0838f83 (MD5) Previous issue date: 2018-04-17 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Detritos espaciais (DE) são objetos que possuem altas velocidades e são capazes de inviabilizar o sucesso de missões espaciais, caso venham a colidir com veículos espaciais, além de colocar em risco a segurança dos astronautas. O nosso modelo matemático é baseado, inicialmente, nas equações dinâmicas derivadas de Clohessy-Wiltshire (1960). Estas equações regem o movimento relativo entre dois corpos e seu uso é apropriado aqui porque descrevemos o movimento relativo entre um veículo espacial e um DE. Dado ao fato de soluções do modelo linear apresentar vários fatoriais resultou em algumas dificuldades nas simulações computacionais, mas obtivemos êxito em contornar essas dificuldades e conseguimos implementar manobras evasivas usando o modelo linear. Space debris (DE) are objects that have high speeds and are capable of unfeasible space missions successful if they collide with space vehicles, as well as endangering the safety of astronauts. Our mathematical model is based initially on the dynamic equations derived from Clohessy-Wiltshire (1960). These equations govern the relative motion between two bodies and their use is appropriate here because we describe the relative motion between a space vehicle and an ED. Due to the fact that solutions of the linear model have several factorials, some difficulties were encountered in the computational simulations, but we succeeded in getting around these difficulties and we were able to implement evasive maneuvers using the linear model.