On the bend number of circular-arc graphs as edge intersection graphs of paths on a grid

Golumbic, Lipshteyn and Stern \cite{Golumbic-epg} proved that every graph can be represented as the edge intersection graph of paths on a grid (EPG graph), i.e., one can associate with each vertex of the graph a nontrivial path on a rectangular grid such that two vertices are adjacent if and only if the corresponding paths share at least one edge of the grid. For a nonnegative integer $k$, $B_k$-EPG graphs are defined as EPG graphs admitting a model in which each path has at most $k$ bends. Circular-arc graphs are intersection graphs of open arcs of a circle. It is easy to see that every circular-arc graph is a $B_4$-EPG graph, by embedding the circle into a rectangle of the grid. In this paper, we prove that every circular-arc graph is $B_3$-EPG, and that there exist circular-arc graphs which are not $B_2$-EPG. If we restrict ourselves to rectangular representations (i.e., the union of the paths used in the model is contained in a rectangle of the grid), we obtain EPR (edge intersection of path in a rectangle) representations. We may define $B_k$-EPR graphs, $k\geq 0$, the same way as $B_k$-EPG graphs. Circular-arc graphs are clearly $B_4$-EPR graphs and we will show that there exist circular-arc graphs that are not $B_3$-EPR graphs. We also show that normal circular-arc graphs are $B_2$-EPR graphs and that there exist normal circular-arc graphs that are not $B_1$-EPR graphs. Finally, we characterize $B_1$-EPR graphs by a family of minimal forbidden induced subgraphs, and show that they form a subclass of normal Helly circular-arc graphs

Exoplanet atmospheres with GIANO II. Detection of molecular absorption in the dayside spectrum of HD 102195b

The study of exoplanetary atmospheres is key to understand the differences between their physical, chemical and dynamical processes. Up to now, the bulk of atmospheric characterization analysis has been conducted on transiting planets. On some sufficiently bright targets, high-resolution spectroscopy (HRS) has also been successfully tested for non-transiting planets. We study the dayside of the non-transiting planet HD 102195b using the GIANO spectrograph mounted at TNG, demonstrating the feasibility of atmospheric characterization measurements and molecular detection for non-transiting planets with the HRS technique using 4-m class telescopes. The Doppler-shifted planetary signal changes on the order of many km/s during the observations, in contrast with the telluric absorption which is stationary in wavelength, allowing us to remove the contamination from telluric lines while preserving the features of the planetary spectrum. The emission signal from HD 102195b's atmosphere is then extracted by cross-correlating the residual spectra with atmospheric models. We detect molecular absorption from water vapor at 4.4$\sigma$ level. We also find convincing evidence for the presence of methane, which is detected at the 4.1$\sigma$ level. The two molecules are detected with a combined significance of 5.3$\sigma$, at a semi-amplitude of the planet radial velocity $K_P=128\pm 6$ km/s. We estimate a planet true mass of $M_P=0.46\pm 0.03~M_J$ and orbital inclination between 72.5 and 84.79$^{\circ}$ (1$\sigma$). Our analysis indicates a non-inverted atmosphere for HD 102195b, as expected given the relatively low temperature of the planet, inefficient to keep TiO/VO in gas phase. Moreover, a comparison with theoretical expectations and chemical model predictions corroborates our methane detection and suggests that the detected $CH_4$ and $H_2O$ signatures could be consistent with a low C/O ratio.Comment: 12 pages, 12 figures, accepted for publication in A&

Social representations of coronavirus/COVID-19 in Italy: Psychosocial anchoring to conspiracy beliefs, vaccine hesitancy, and the psychological dimension

From the societal approach of the Theory of Social Representations, this study aimed to investigate the social representations of coronavirus/COVID-19 among the Italian population. By means of an online questionnaire, 599 individuals participated in the research, with a mean age of 38.09 years (SD = 14.44), 62.1% being women. The instrument was composed of sociodemographic questions, free association technique for the inductive term “coronavirus/COVID-19” and scales on conspiracy beliefs, vaccine hesitancy, and psychological dimension. The results allowed us to identify four social representations: “Citizens driven by Social Representations anchored to factual Covid-19 pandemic data,” with lower vaccine hesitancy and conspiracy beliefs, and greater faith in science; “Citizens with low confidence in anti-pandemic preventive measures by government,” with lower agreement with restriction measures; “Emotional people,” with higher agreement with restriction measures and expression of psychological distress; and “Minority group of Citizens driven by denial of Covid-19,” with higher vaccine hesitancy and conspiracy beliefs. We discuss the different social representations identified from the psychological and psychosocial anchoring processes in the context of the COVID-19 pandemic

Improved parameters of seven Kepler giant companions characterized with SOPHIE and HARPS-N

Radial-velocity observations of Kepler candidates obtained with the SOPHIE and HARPS-N spectrographs have permitted unveiling the nature of the five giant planets Kepler-41b, Kepler-43b, Kepler-44b, Kepler-74b, and Kepler-75b, the massive companion Kepler-39b, and the brown dwarf KOI-205b. These companions were previously characterized with long-cadence (LC) Kepler data. Here we aim at refining the parameters of these transiting systems by i) modelling the published radial velocities (RV) and Kepler short-cadence (SC) data that provide a much better sampling of the transits, ii) performing new spectral analyses of the SOPHIE and ESPaDOnS spectra, and iii) improving stellar rotation periods hence stellar age estimates through gyrochronology, when possible. Posterior distributions of the system parameters were derived with a differential evolution Markov chain Monte Carlo approach. Our main results are as follows: a) Kepler-41b is significantly larger and less dense than previously found because a lower orbital inclination is favoured by SC data. This also affects the determination of the geometric albedo that is lower than previously derived: Ag < 0.135; b) Kepler-44b is moderately smaller and denser than reported in the discovery paper; c) good agreement was achieved with published Kepler-43, Kepler-75, and KOI-205 system parameters, although the host stars Kepler-75 and KOI-205 were found to be slightly richer in metals and hotter, respectively; d) the previously reported non-zero eccentricities of Kepler-39b and Kepler-74b might be spurious. If their orbits were circular, the two companions would be smaller and denser than in the eccentric case. The radius of Kepler-39b is still larger than predicted by theoretical isochrones. Its parent star is hotter and richer in metals than previously determined. [ABRIDGED]Comment: 17 pages, 9 figures, accepted for publication in Astronomy and Astrophysic

Exoplanet atmospheres with GIANO. I. Water in the transmission spectrum of HD 189733b

High-resolution spectroscopy (R $\ge$ 20,000) at near-infrared wavelengths can be used to investigate the composition, structure, and circulation patterns of exoplanet atmospheres. However, up to now it has been the exclusive dominion of the biggest telescope facilities on the ground, due to the large amount of photons necessary to measure a signal in high-dispersion spectra. Here we show that spectrographs with a novel design - in particular a large spectral range - can open exoplanet characterisation to smaller telescope facilities too. We aim to demonstrate the concept on a series of spectra of the exoplanet HD 189733 b taken at the Telescopio Nazionale Galileo with the near-infrared spectrograph GIANO during two transits of the planet. In contrast to absorption in the Earth's atmosphere (telluric absorption), the planet transmission spectrum shifts in radial velocity during transit due to the changing orbital motion of the planet. This allows us to remove the telluric spectrum while preserving the signal of the exoplanet. The latter is then extracted by cross-correlating the residual spectra with template models of the planet atmosphere computed through line-by-line radiative transfer calculations, and containing molecular absorption lines from water and methane. By combining the signal of many thousands of planet molecular lines, we confirm the presence of water vapour in the atmosphere of HD 189733 b at the 5.5-$\sigma$ level. This signal was measured only in the first of the two observing nights. By injecting and retrieving artificial signals, we show that the non-detection on the second night is likely due to an inferior quality of the data. The measured strength of the planet transmission spectrum is fully consistent with past CRIRES observations at the VLT, excluding a strong variability in the depth of molecular absorption lines.Comment: 10 pages, 8 figures. Accepted for publication in Astronomy & Astrophysics. v2 includes language editin

Índice padronizado de precipitação aplicado às condições de seca no Estado do Espírito Santo.

O Índice Padronizado de Precipitação (SPI) é um dos métodos mais utilizados para quantificação da seca. A fim de verificar a possibilidade de utilização do SPI no monitoramento das deficiências e excessos de precipitação na escala mensal, no Estado do Espírito Santo objetivou-se, neste trabalho, verificar o ajuste das séries temporais dessa variável meteorológica à distribuição gama em cinco localidades do Estado. Por meio dos testes de aderência Kolmogorov-Smirnov e qui-quadrado, as séries mensais de precipitação pluvial das localidades sob análise podem ser consideradas oriundas de uma população com distribuição gama incompleta, permitindo o uso do SPI no monitoramento das condições de seca meteorológica. Através de análises de autocorrelação e correlação-cruzada, observou-se que a principal característica das séries do SPI é sua grande variabilidade espaço-temporal, a qual indica que em uma mesma região meses extremamente secos podem ser precedidos e/ou seguidos de meses úmidos ou normais, e que distintos casos de seca podem ocorrer de forma aleatória, entre as localidades e em um mesmo período