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Average magnetic field measurements are presented for 62 M-dwarf members of the Pleiades open cluster, derived from Zeeman-enhanced Fe i lines in the H band. A Markov Chain Monte Carlo methodology was employed to model magnetic filling factors using Sloan Digital Sky Survey (SDSS) IV APOGEE high-resolution spectra, along with the radiative transfer code Synmast, MARCS stellar atmosphere models, and the APOGEE Data Release 17 spectral line list. There is a positive correlation between mean magnetic fields and stellar rotation, with slow-rotator stars (Rossby number, Ro > 0.13) exhibiting a steeper slope than rapid rotators (Ro < 0.13). However, the latter sample still shows a positive trend between Ro and magnetic fields, which is given by 〈 B 〉 = 1604 × Ro ^−0.20 . The derived stellar radii when compared with physical isochrones show that, on average, our sample shows radius inflation, with median enhanced radii ranging from +3.0% to +7.0%, depending on the model. There is a positive correlation between magnetic field strength and radius inflation, as well as with stellar spot coverage, correlations which together indicate that stellar spot-filling factors generated by strong magnetic fields might be the mechanism that drives radius inflation in these stars. We also compare our derived magnetic fields with chromospheric emission lines (H α , H β , and Ca ii K), as well as with X-ray and H α to bolometric luminosity ratios, and find that stars with higher chromospheric and coronal activity tend to be more magnetic.

Exoplanets hosting M dwarfs are the best targets to characterize Earth-like or super-Earth planetary atmospheres with the James Webb Space Telescope (JWST). We determine detailed stellar parameters ( T _eff , log g , and ξ ) and individual abundances of 12 elements for four cool M dwarfs hosting exoplanets TOI-1685, GJ 436, GJ 3470, and TOI-2445, scheduled for future observations by the JWST. The analysis utilizes high-resolution near-infrared spectra from the Sloan Digital Sky Survey IV APOGEE survey between 1.51 and 1.69 μ m. Based on 1D LTE plane-parallel models, we find that TOI-2445 is slightly metal poor ([Fe/H] = −0.16 ± 0.09 dex), while TOI-1685, GJ 436, and GJ 3470 are more metal rich ([Fe/H] = 0.06 ± 0.18, 0.10 ± 0.20, and 0.25 ± 0.15 dex, respectively). The derived C/O ratios for TOI-2445, TOI-1685, GJ 436, and GJ 3470 are 0.526 ± 0.027, 0.558 ± 0.097, 0.561 ± 0.029, and 0.638 ± 0.015, respectively. From the results for 28 M dwarfs analyzed homogeneously from Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra, we find exoplanet-hosting M dwarfs exhibit a C/O abundance ratio approximately 0.01–0.05 higher than those with nondetected exoplanets, at limits of a statistically significant offset. A linear regression of the [Fe/H] versus C/O distribution reveals a noticeable difference in the angular coefficient between FGK dwarfs (0.27) and M dwarfs (0.13). Assuming our abundance ratios of Ca/Mg, Si/Mg, Al/Mg, and Fe/Mg, we determine a mass of ${3.276}_{-0.419}^{+0.448}$ M _⊕ for TOI-2445 b, which has a density (6.793 ${}_{-0.099}^{+0.005}$ g cm ^−3 ) and core mass fraction (0.329 ${}_{-0.049}^{+0.028}$ ) very similar to Earth’s. We also present an atlas of 113 well-defined spectral lines to analyze M dwarfs in the H band and a comprehensive evaluation of uncertainties from variations in the atmospheric parameters, signal-to-noise ratio, and pseudocontinuum.

Stellar magnetic fields have a major impact on space weather around exoplanets orbiting low-mass stars. From an analysis of Zeeman-broadened Fe i lines measured in near-infrared SDSS/APOGEE spectra, mean magnetic fields are determined for a sample of 29 M dwarf stars that host closely orbiting small exoplanets. The calculations employed the radiative transfer code Synmast and MARCS stellar model atmospheres. The sample M dwarfs are found to have measurable mean magnetic fields ranging between ∼0.2 and ∼1.5 kG, falling in the unsaturated regime on the 〈 B 〉 versus P _rot plane. The sample systems contain 43 exoplanets, which include 23 from Kepler, nine from K2, and nine from Transiting Exoplanet Survey Satellite. We evaluated their equilibrium temperatures, insolation, and stellar habitable zones and found that only Kepler-186f and TOI-700d are inside the habitable zones of their stars. Using the derived values of 〈 B 〉 for the stars Kepler-186 and TOI-700 we evaluated the minimum planetary magnetic field that would be necessary to shield the exoplanets Kepler-186f and TOI-700d from their host star’s winds, considering reference magnetospheres with sizes equal to those of the present-day and young Earth, respectively. Assuming a ratio of 5% between large- to small-scale B -fields, and a young-Earth magnetosphere, Kepler-186f and TOI-700d would need minimum planetary magnetic fields of, respectively, 0.05 and 0.24 G. These values are considerably smaller than Earth’s magnetic field of 0.25 G ≲ B ≲ 0.65 G, which suggests that these two exoplanets might have magnetic fields sufficiently strong to protect their atmospheres and surfaces from stellar magnetic fields.

We present a spectroscopic analysis of a sample of 48 M-dwarf stars (0.2 M _⊙ < M < 0.6 M _⊙ ) from the Hyades open cluster using high-resolution H -band spectra from the Sloan Digital Sky Survey/Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. Our methodology adopts spectrum synthesis with LTE MARCS model atmospheres, along with the APOGEE Data Release 17 line list, to determine effective temperatures, surface gravities, metallicities, and projected rotational velocities. The median metallicity obtained for the Hyades M dwarfs is [M/H] = 0.09 ± 0.03 dex, indicating a small internal uncertainty and good agreement with optical results for Hyades red giants. Overall, the median radii are larger than predicted by stellar models by 1.6% ± 2.3% and 2.4% ± 2.3%, relative to a MIST and DARTMOUTH isochrone, respectively. We emphasize, however, that these isochrones are different, and the fractional radius inflation for the fully and partially convective regimes have distinct behaviors depending on the isochrone. Using a MIST isochrone there is no evidence of radius inflation for the fully convective stars, while for the partially convective M dwarfs the radii are inflated by 2.7% ± 2.1%, which is in agreement with predictions from models that include magnetic fields. For the partially convective stars, rapid rotators present on average higher inflation levels than slow rotators. The comparison with SPOTS isochrone models indicates that the derived M-dwarf radii can be explained by accounting for stellar spots in the photosphere of the stars, with 76% of the studied M dwarfs having up to 20% spot coverage, and the most inflated stars with ∼20%–40% spot coverage.

O artigo relembra a figura do cientista político argentino Guillermo O'Donnell (1936-2011) e reconsidera criticamente aspectos centrais de sua obra, particularmente sua tipologia de regimes autoritários modernos e suas análises da transição para e consolidação da democracia em países de experiência autoritária recente.An hommage in the form of a critical reflexion on Guillermo O'Donnell's (1936-2011) tipology of authoritarian regimes and his analysis of democratic transition and consolidation in countries of recent authoritarian experience.

O artigo analisa o processo de institucionalização partidária no Brasil pós-redemocratização. A formação do Partido dos Trabalhadores, e seu repetido enfrentamento eleitoral com o PSDB, aponta para um processo em andamento mas ainda incompleto: a criação, em torno dos dois partidos, de identificações político-partidárias estáveis que podem eventualmente redundar num sistema partidário simplificado e consolidado, com, entre outras coisas, a neutralização do êxito até aqui obtido pela postura excessivamente clientelista e pragmática que orienta o fragmentário enraizamento regional do PMDB.The article discusses the process of institutionalization of political parties in Brazil in the post-redemocratization period. The advent of the Worker's Party (PT), and its electoral disputes with the Brazilian Social Democracy Party (PSDB) point to an ongoing yet unaccomplished process: the emergence, in the orbit of both parties, of stable political-partidary identifications that could lead to a simplified and consolidated party system and the neutralization of the success of the excessively clientelistic and pragmatic orientation that characterizes Brazilian Democratic Movement Party's (PMDB) feeble regional roots.

O artigo examina alguns pressupostos psicossociológicos do nacionalismo quanto à identidade coletiva e às suas relações com o problema geral da igualdade. O nacionalismo "oficial" brasileiro do século passado e a "Teoria da dependência" são objeto de breve avaliação crítica, sobretudo à luz da nova dinâmica econômica global, além de confrontar-se o ânimo nacionalista com os anseios relacionados a um ideal pluralista.The article examines a few psychosociological aspects of nationalism in terms of collective identity and their relationship with the general problem of equality. The "official" Brazilian nationalism from last century and the "Dependence theory" are objects of a brief critical analysis in the light of the new global economic dynamics. Also, the national spirit and the longings for a pluralist ideal are confronted.

O artigo se dirige à conexão entre crises econômicas e a consolidação democrática na América Latina. Argumenta-se em favor de uma abordagem teoricamente ambiciosa, ante enfoques restritivos ou irracionalistas sobre as transições. O papel das crises conjunturais é relacionado à temática institucional (ou “constitucional”) da democracia, em sua articulação com o desenvolvimento capitalista. A lógica que parece emergir de uma aproximação entre as experiências da América Latina, na Europa Meridional, de outros autoritarismos e da derrocada do Leste Europeu é explorada de forma preliminar. Democracia; Transição

This article proposes a division of the concept of space in music into four spaces, namely the internal, external, intrinsic and extrinsic spaces. Having reviewed these concepts in texts from numerous authors and composers, we aggregate a variety of concepts into these four main categories of space in music. We also present possible transgressions of the boundaries of these concepts, with the understanding that these transgressions are common practice for contemporary composers. Currently, these practices of transgression tend to be confused because of the lack of a clear definition for the spaces in question.

This article aims to define the development of audiovisual electroacoustic music for virtual reality (VR) as an emerging artistic expression. Revisiting concepts and terminologies by several authors (Gibbs, 2007; Leite, 2004; Lima, 2011; Fry, 1920) in relation to the most diverse audiovisual manifestations, we consolidated Hill's definition (2010) and expanded it to a specific reproduction system, VR, as the most appropriate for our object of study. The maintenance of what we call extrinsic space (Henriksen, 2002) in this type of manifestation makes it possible to consolidate it as a musical parameter. First studies in audiovisual electroacoustic music for VR are presented as result of doctoral work.

Apresentamos neste trabalho o conceito de espaço extrínseco e, a partir de estudos bibliográficos relacionados ao desenvolvimento sintático e semântico do mesmo, assim como da prática de espacialização em tempo real e da composição de obras para sistemas multicanais, nos direcionamos para a estruturação do que denominamos de Unidades Semióticas Espaciais (USEs). Pretendidas como as menores unidades perceptíveis no domínio do espaço extrínseco capazes de produzir algum significado artístico, as USEs são uma proposta de ferramenta para composição e análise tanto de material sonoro quanto imagético. A partir da proposta de uma grafia para as USEs, apresentamos uma análise do espaço extrínseco de uma composição de música eletroacústica audiovisual realizada pelo autor. Avaliamos vantagens e desvantagens do procedimento adotado na conclusão.