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Full list of authors: Santos-Sanz, P.; Ortiz, J. L.; Sicardy, B.; Benedetti-Rossi, G.; Morales, N.; Fernández-Valenzuela, E.; Duffard, R.; Iglesias-Marzoa, R.; Lamadrid, J. L.; Maícas, N.; Pérez, L.; Gazeas, K.; Guirado, J. C.; Peris, V.; Ballesteros, F. J.; Organero, F.; Ana-Hernández, L.; Fonseca, F.; Alvarez-Candal, A.; Jiménez-Teja, Y. Vara-Lubiano, M.; Braga-Ribas, F.; Camargo, J. I. B.; Desmars, J.; Assafin, M.; Vieira-Martins, R.; Alikakos, J.; Boutet, M.; Bretton, M.; Carbognani, A.; Charmandaris, V.; Ciabattari, F.; Delincak, P.; Fuambuena Leiva, A.; González, H.; Haymes, T.; Hellmich, S.; Horbowicz, J.; Jennings, M.; Kattentidt, B.; Kiss, Cs; Komžík, R.; Lecacheux, J.; Marciniak, A.; Moindrot, S.; Mottola, S.; Pal, A.; Paschalis, N.; Pastor, S.; Perello, C.; Pribulla, T.; Ratinaud, C.; Reyes, J. A.; Sanchez, J.; Schnabel, C.; Selva, A.; Signoret, F.; Sonbas, E.; Alí-Lagoa, V.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., We predicted a stellar occultation of the bright star Gaia DR1 4332852996360346368 (UCAC4 385-75921) (mV = 14.0 mag) by the centaur 2002 GZ32 for 2017 May 20. Our latest shadow path prediction was favourable to a large region in Europe. Observations were arranged in a broad region inside the nominal shadow path. Series of images were obtained with 29 telescopes throughout Europe and from six of them (five in Spain and one in Greece) we detected the occultation. This is the fourth centaur, besides Chariklo, Chiron, and Bienor, for which a multichord stellar occultation is reported. By means of an elliptical fit to the occultation chords, we obtained the limb of 2002 GZ32 during the occultation, resulting in an ellipse with axes of 305 ± 17 km × 146 ± 8 km. From this limb, thanks to a rotational light curve obtained shortly after the occultation, we derived the geometric albedo of 2002 GZ32 (pV = 0.043 ± 0.007) and a 3D ellipsoidal shape with axes 366 km × 306 km × 120 km. This shape is not fully consistent with a homogeneous body in hydrostatic equilibrium for the known rotation period of 2002 GZ32. The size (albedo) obtained from the occultation is respectively smaller (greater) than that derived from the radiometric technique but compatible within error bars. No rings or debris around 2002 GZ32 were detected from the occultation, but narrow and thin rings cannot be discarded. © 2020 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society., P.S-S. acknowledges financial support by the Spanish grant AYA-RTI2018-098657-J-I00 'LEO-SBNAF' (MCIU/AEI/FEDER, UE). PS-S, JLO, NM, and RD 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 Astrofisica de Andalucia (SEV-2017-0709), they also acknowledge the financial support by the Spanish grant AYA-2017-84637-R and the Proyecto de Excelencia de la Junta de Andalucia J.A. 2012-FQM1776. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). The research leading to these results has received funding from the European Union's Horizon 2020 Research and Innovation Programme, under Grant Agreement no. 687378, as part of the project `Small Bodies Near and Far' (SBNAF). Part of the research leading to these results has received funding from the European Research Council under the European Community's H2020 (2014-2020/ERC Grant Agreement no. 669416 `LUCKY STAR'). E.F-V. acknowledges funding through the Preeminant Postdoctoral Program of the University of Central Florida. Part of the data were collected during the photometric monitoring observations with the robotic and remotely controlled observatory at the University of Athens Observatory -UOAO (Gazeas 2016). F.J.B. acknowledges financial support by the Spanish grant AYA2016-81065-C2-2-P. A.A-C. acknowledges support from FAPERJ (grant E26/203.186/2016) and CNPq (grants 304971/20162 and 401669/2016-5). A.C. acknowledges the use of the main telescope of theAstronomical Observatory of the Autonomous Region of the Aosta Valley (OAVdA). C.K. has been supported by the grants K125015 and GINOP-2.3.2-15-2016-00003 of the National Research, Development and Innovation Office, Hungary (NKFIH). T.P. and R.K. acknowledge support from the project ITMS No. 26220120029, based on the Research and development program financed from the European Regional Development Fund and from the Slovak Research and Development Agency -the contract No. APVV-150458. We are grateful to the CAHA and OSN staffs. This research is partially based on observations collected at Centro Astronomico Hispano-Aleman (CAHA) at Calar Alto, operated jointly by Junta de Andalucia and Consejo Superior de Investigaciones Cientificas (IAA-CSIC). This research was also partially based on observation carried out at the Observatorio de Sierra Nevada (OSN) operated by Instituto de Astrofisica de Andalucia (CSIC). This article is also based on observations made with the Liverpool Telescope operated on the island of La Palma by the Instituto de Astrofisica de Canarias in the Spanish Roque de losMuchachos Observatory. Partially based on observations made with the Tx40 telescope at the Observatorio Astrofisico de Javalambre in Teruel, a Spanish Infraestructura Cientifico-Tecnica Singular (ICTS) owned, managed and operated by the Centro de Estudios de Fisica del Cosmos de Arag on (CEFCA). Tx40 is funded with the Fondos de Inversiones de Teruel (FITE). 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.

KIC 8462852 stood out among more than 100,000 stars in the Kepler catalogue because of the strange features of its light curve: a wide, asymmetric dimming taking up to 15 per cent of the light at D793 and a period of multiple, narrow dimmings happening approximately 700 days later. Several models have been proposed to account for this abnormal behaviour, most of which require either unlikely causes or a finely-tuned timing. We aim at offering a relatively natural solution, invoking only phenomena that have been previously observed, although perhaps in larger or more massive versions. We model the system using a large, ringed body whose transit produces the first dimming and a swarm of Trojan objects sharing its orbit that causes the second period of multiple dimmings. The resulting orbital period is $T\approx12$ years, with a semi-major axis $a\approx6$ au. Our model allows us to make two straightforward predictions: we expect the passage of a new swarm of Trojans in front of the star starting during the early months of 2021, and a new transit of the main object during the first half of 2023., Comment: 5 pages, 2 figures. v3: Accepted for publication in MNRAS Letters

One of the basic tenets of exobiology is the need for a liquid substratum in which life can arise, evolve, and develop. The most common version of this idea involves the necessity of water to act as such a substratum, both because that is the case on Earth and because it seems to be the most viable liquid for chemical reactions that lead to life. Other liquid media that could harbor life, however, have occasionally been put forth. In this work, we investigate the relative probability of finding superficial seas on rocky worlds that could be composed of nine different, potentially abundant, liquids, including water. We study the phase space size of habitable zones defined for those substances. The regions where there can be liquid around every type of star are calculated by using a simple model, excluding areas within a tidal locking distance. We combine the size of these regions with the stellar abundances in the Milky Way disk and modulate our result with the expected radial abundance of planets via a generalized Titius-Bode law, as statistics of exoplanet orbits seem to point to its adequateness. We conclude that seas of ethane may be up to nine times more frequent among exoplanets than seas of water, and that solvents other than water may play a significant role in the search for extrasolar seas., This work has been funded by projects AYA2013-48623-C2-2 and AYA2016-81065-C2-2 from the Spanish Ministerio de Economía y Competitividad and PrometeoII/2014/060 from the Generalitat Valenciana (Spain).

Tell Bartolo Luque and Fernando Ballesteros how far the Sun is from the Earth, and they will tell you the size of the Universe.

Gravitation is one of the main forces of nature and is a fundamental factor for the habitability of the cosmos. Not only it is the main source of structures in a universe that, without it, would be only a faint soup of gases, but it is the main engine for creating stars and worlds, to make these planets inhabitable and to impose structural and functional limits on the organisms that can be developed in them.

A novel class of graphs, here named quasiperiodic, are const ructed via application of the Horizontal Visibility algorithm to the time series generated along the quasiperiodic route to chaos. We show how the hierarchy of mode-locked regions represented by the Far ey tree is inherited by their associated graphs. We are able to establish, via Renormalization Group (RG) theory, the architecture of the quasiperiodic graphs produced by irrational winding numbers with pure periodic continued fraction. And finally, we demonstrate that the RG fixed-point degree distributions are recovered via optimization of a suitably defined graph entropy

The original ALHAMBRA catalogue contained over 400 000 galaxies selected using a synthetic F814W image, to the magnitude limit AB(F814W) ≈ 24.5. Given the photometric redshift depth of the ALHAMBRA multiband data (〈 z〉 = 0.86) and the approximately I-band selection, there is a noticeable bias against red objects at moderate redshift.We avoid this bias by creating a new catalogue selected in the Ks band. This newly obtained catalogue is certainly shallower in terms of apparent magnitude, but deeper in terms of redshift, with a significant population of red objects at z > 1. We select objects using the Ks band images, which reach an approximate AB magnitude limit Ks ≈ 22. We generate masks and derive completeness functions to characterize the sample. We have tested the quality of the photometry and photometric redshifts using both internal and external checks. Our final catalogue includes ≈95 000 sources down to Ks ≈ 22, with a significant tail towards high redshift. We have checked that there is a large sample of objects with spectral energy distributions that correspond to that of massive, passively evolving galaxies at z > 1, reaching as far as z ≈ 2.5. We have tested the possibility of combining our data with deep infrared observations at longer wavelengths, particularly Spitzer IRAC data. © 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society., This work was mainly supported by the Spanish Ministry for Economy and Competitiveness and FEDER funds through grants AYA2010-22111-C03-02 and AYA2013-48623-C2-2, and by the Generalitat Valenciana through project PrometeoII 2014/060. We also acknowledge support from the Spanish Ministry for Economy and Competitiveness and FEDER funds through grants AYA2012-39620, AYA2013-40611-P, AYA2013-42227-P, AYA2013-43188-P, AYA2013-48623-C2-1, ESP2013-48274, AYA2014-58861-C3-1, Junta de Andalucia grants TIC114, JA2828, P10-FQM-6444, and Generalitat de Catalunya project SGR-1398. BA has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 656354. PTI acknowledges support from CONICYT Chile grant FONDECYT 3140542.

Time series are proficiently converted into graphs via the horizontal visibility (HV) algorithm, which prompts interest in its capability for capturing the nature of different classes of series in a network context. We have recently shown [1] that dynamical systems can be studied from a novel perspective via the use of this method. Specifically, the period-doubling and band-splitting attractor cascades that characterize unimodal maps transform into families of graphs that turn out to be independent of map nonlinearity or other particulars. Here we provide an in depth description of the HV treatment of the Feigenbaum scenario, together with analytical derivations that relate to the degree distributions, mean distances, clustering coefficients, etc., associated to the bifurcation cascades and their accumulation points. We describe how the resultant families of graphs can be framed into a renormalization group scheme in which fixed-point graphs reveal their scaling properties. These fixed points are then re-derived from an entropy optimization process defined for the graph sets, confirming a suggested connection between renormalization group and entropy optimization. Finally, we provide analytical and numerical results for the graph entropy and show that it emulates the Lyapunov exponent of the map independently of its sign., 19 pages, 11 figures, accepted for publication in Chaos

The recently formulated theory of horizontal visibility graphs transforms time series into graphs and allows the possibility of studying dynamical systems through the characterization of their associated networks. This method leads to a natural graph-theoretical description of nonlinear systems with qualities in the spirit of symbolic dynamics. We support our claim via the case study of the period-doubling and band-splitting attractor cascades that characterize unimodal maps. We provide a universal analytical description of this classic scenario in terms of the horizontal visibility graphs associated with the dynamics within the attractors, that we call Feigenbaum graphs, independent of map nonlinearity or other particulars. We derive exact results for their degree distribution and related quantities, recast them in the context of the renormalization group and find that its fixed points coincide with those of network entropy optimization. Furthermore, we show that the network entropy mimics the Lyapunov exponent of the map independently of its sign, hinting at a Pesin-like relation equally valid out of chaos., Comment: Published in PLoS ONE (Sep 2011)

The visibility algorithm has been recently introduced as a mapping between time series and complex networks. This procedure allows us to apply methods of complex network theory for characterizing time series. In this work we present the horizontal visibility algorithm, a geometrically simpler and analytically solvable version of our former algorithm, focusing on the mapping of random series (series of independent identically distributed random variables). After presenting some properties of the algorithm, we present exact results on the topological properties of graphs associated with random series, namely, the degree distribution, the clustering coefficient, and the mean path length. We show that the horizontal visibility algorithm stands as a simple method to discriminate randomness in time series since any random series maps to a graph with an exponential degree distribution of the shape P(k)=(1/3)(2/3)(k-2), independent of the probability distribution from which the series was generated. Accordingly, visibility graphs with other P(k) are related to nonrandom series. Numerical simulations confirm the accuracy of the theorems for finite series. In a second part, we show that the method is able to distinguish chaotic series from independent and identically distributed (i.i.d.) theory, studying the following situations: (i) noise-free low-dimensional chaotic series, (ii) low-dimensional noisy chaotic series, even in the presence of large amounts of noise, and (iii) high-dimensional chaotic series (coupled map lattice), without needs for additional techniques such as surrogate data or noise reduction methods. Finally, heuristic arguments are given to explain the topological properties of chaotic series, and several sequences that are conjectured to be random are analyzed.

In this work we present a simple and fast computational method, the visibility algorithm , that converts a time series into a graph. The constructed graph inherits several properties of the series in its structure. Thereby, periodic series convert into regular graphs, and random series do so into random graphs. Moreover, fractal series convert into scale-free networks, enhancing the fact that power law degree distributions are related to fractality, something highly discussed recently. Some remarkable examples and analytical tools are outlined to test the method's reliability. Many different measures, recently developed in the complex network theory, could by means of this new approach characterize time series from a new point of view.