Chemical composition of Galactic OB stars II. The fast rotator Z Oph

Z Oph, HD149757, is an O9.5 Vnn star with a very high projected rotational velocity (vsini >= 340 km\s). It is also a classical runaway star due to its high proper motion. We perform a quantitative analysis of its optical spectrum in order to measure important observables of the star such as its mass, effective temperature, luminosity and He, C, N, and O abundances. Comparing these observed values to those predicted by the rotating evolutionary models of the Geneva group we find that none of the two sets of models is capable of reproducing the characteristics of the star. Nevertheless, due to its runaway nature, the reason for this discrepancy may be that the star is not the result of the evolution of a single object, but the product of the evolution of a close binary system.Comment: Accepted for publication in A&

Relatório final de estágio pedagógico realizado na Escola Secundária Professor José Augusto Lucas

Este relatório consiste na reflexão sobre o percurso realizado ao longo do processo de estágio pedagógico na escola Secundária Professor José Augusto lucas. Este percurso concretizou-se numa história de superação de conflitos e barreiras que foram surgindo e que, de uma forma ou de outra, fui aprendendo a gerir e ultrapassar. Assim, este documento é uma narração desse percurso de um ano, em que cada situação é olhada através do meu espirito critico e reflexivo e suportada pela pesquisa teórica de que me pude valer. O objetivo do percurso é validar as minhas competências enquanto professora que procura o sucesso dos seus alunos e que domina os aspetos relacionados com a disciplina de Educação Física.This report is the reflection of the journey undertaken during the teaching practice process. This route traces a story of overcoming conflicts, and some barriers that emergerd and that , in one way or another, I’ve learn to manage and overcome . Thus, this document is an account of this journey of a year, where each situation is looked through my critical and reflective spirit and supported by a research that I’ve done. The objetive of the course is to validate my skills as a teacher who seek the success of their students and is trying to dominating aspects related to Physical Education

Stellar evolution with rotation and magnetic fields II: General equations for the transport by Tayler--Spruit dynamo

We further develop the Tayler--Spruit dynamo theory, based on the most efficient instability for generating magnetic fields in radiative layers of differentially rotating stars. We avoid the simplifying assumptions that either the $\mu$-- or the $T$--gradient dominates, but we treat the general case and we also account for the nonadiabatic effects, which favour the growth of the magnetic field. Stars with a magnetic field rotate almost as a solid body. Several of their properties (size of the core, MS lifetimes, tracks, abundances) are closer to those of models without rotation than with rotation only. In particular, the observed N/C or N/H excesses in OB stars are better explained by our previous models with rotation only than by the present models with magnetic fields that predict no nitrogen excesses. We show that there is a complex feedback loop between the magnetic instability and the thermal instability driving meridional circulation. This opens the possibility for further magnetic models, but at this stage we do not know the relative importance of the magnetic fields due to the Tayler instability in stellar interiors.Comment: 14 pages, 11 figures, accepted for publication in Astronomy and Astrophysic

A Arquitectura Religiosa Gótica em Portugal no Século XIV: o Tempo dos Experimentalismos

Tese apresentada para cumprimento dos requisitos necessários à obtenção do grau de Doutor em História da Arte MedievalCom este estudo sobre a arquitectura religiosa gótica no século XIV em Portugal pretende-se, acima de tudo, trazer para a luz e valorizar um tema que nos parece da maior importância e cujas análises até ao momento têm frequentemente relegado para segundo plano: o facto de o século XIV se apresentar com uma diversidade de tipologias arquitectónicas que leva ao questionamento da possibilidade desta centúria se afirmar como um momento de experimentação na arquitectura medieval portuguesa. Tal possibilidade marcou o ponto de partida de uma investigação centrada na tentativa de identificação, compreensão e distinção das diferentes tipologias, de forma a entender se as mesmas são herdeiras de uma arquitectura proveniente dos séculos anteriores ou se se estabelecem como modelos inovadores até então não ensaiados. Por outras palavras, tentar entender se nos encontramos ou não perante um período de experimentalismos. Paralelamente, e de forma a avaliar o verdadeiro peso desses experimentalismos, procurou definir-se se, para lá da sua existência, existe alguma tipologia "padrão" no século XIV português, uma tipologia que se possa considerar dominante e que se afirme sobre as restantes. Associado a este objectivo, surgiu-nos um terceiro: a tentativa de compreensão da importância que as diferentes ordens religiosas tiveram no desenvolvimento do gótico português, bem como o de tentar apreender de que forma a sua arquitectura se interliga. Pretendeu-se, assim, perceber se a cada ordem se pode associar uma determinada tipologia construtiva e, em caso afirmativo, se essa "tipologia de ordem" é rígida e exclusiva, se se pode considerar alguma ordem (ou ordens) religiosa como responsável por qualquer espécie de experimentalismo arquitectónico, "criando" a sua própria arquitectura ex nihilo, e até que ponto essa arquitectura extravasa para lá dela mesma e vai, ou não, influenciar construções que não pertençam a nenhuma ordem, como as igrejas paroquiais. Para a persecução destes objectivos selecionou-se um corpus arquitectónico diversificado e que permitisse uma visão abrangente da arquitectura religiosa dos séculos XIII e XIV, englobando vertentes distintas da mesma, como a arquitectura monástica e paroquial nas suas diversas tipologias ou os claustros, espaços privilegiados de experimentação

On the effective temperature scale of O stars

We rediscuss the temperature of O dwarfs based on new non-LTE line blanketed atmosphere models including stellar winds computed with the CMFGEN code of Hillier & Miller (1998). Compared to the latest calibration of Vacca et al. (1996), the inclusion of line blanketing leads to lower effective temperatures, typically by 4000 to 1500 K for O3 to O9.5 dwarf stars. The dependence of the Teff-scale on stellar and model parameters - such as mass loss, microturbulence, and metallicity - is explored, and model predictions are compared to optical observations of O stars. Even for an SMC metallicity we find a non-negligible effect of line blanketing on the Teff-scale. The temperature reduction implies downward revisions of luminosities by 0.1 dex and Lyman continuum fluxes Q0 by approximately 40% for dwarfs of a given spectral type.Comment: 6 pages, 4 figures. To be published in A&

The VLT-FLAMES survey of massive stars: Wind properties and evolution of hot massive stars in the LMC

[Abridged] We have studied the optical spectra of 28 O- and early B-type stars in the Large Magellanic Cloud, 22 of which are associated with the young star-forming region N11. Stellar parameters are determined using an automated fitting method, combining the stellar atmosphere code FASTWIND with the genetic-algorithm optimisation routine PIKAIA. Results for stars in the LH9 and LH10 associations of N11 are consistent with a sequential star formation scenario, in which activity in LH9 triggered the formation of LH10. Our sample contains four stars of spectral type O2, of which the hottest is found to be ~49-54 kK (cf. ~45-46 kK for O3 stars). The masses of helium-enriched dwarfs and giants are systematically lower than those implied by non-rotating evolutionary tracks. We interpret this as evidence for efficient rotationally-enhanced mixing, leading to the surfacing of primary helium and to an increase of the stellar luminosity. This result is consistent with findings for SMC stars by Mokiem et al. For bright giants and supergiants no such mass-discrepancy is found, implying that these stars follow tracks of modestly (or non-)rotating objects. Stellar mass-loss properties were found to be intermediate to those found in massive stars in the Galaxy and the SMC, and comparisons with theoretical predictions at LMC metallicity yielded good agreement over the luminosity range of our targets, i.e. 5.0 < log L/L(sun) < 6.1

The nature of the high Galactic latitude O-star HD93521: new results from X-ray and optical spectroscopy

Owing to its unusual location and its isolation, the nature of the high Galactic latitude O9.5Vp object HD93521 is still uncertain. We have collected X-ray and optical observations to characterize the star and its surroundings. X-ray images and spectra are analyzed to search for traces of a recent star formation event around HD93521 and to search for the signature of a possible compact companion. Optical echelle spectra are analysed with plane-parallel model atmosphere codes, assuming either a spherical star or a gravity darkened rotationally flattened star, to infer the effective temperature and surface gravity, and to derive the He, C, N and O abundances of HD93521. The X-ray images reveal no traces of a population of young low-mass stars coeval with HD93521. The X-ray spectrum of HD93521 is consistent with a normal late O-type star although with subsolar metallicity. No trace of a compact companion is found in the X-ray data. In the optical spectrum, He and N are found to be overabundant, in line with the effect of rotational mixing in this very fast rotator, whilst C and O are subsolar. A critical comparison with the properties of subdwarf OB stars, indicates that, despite some apparent similarities, HD93521 does not belong to this category. Despite some ambiguities on the runaway status of the star, the most likely explanation is that HD93521 is a Population I massive O-type star that was ejected from the Galactic plane either through dynamical interactions or a result of a supernova event in a binary system.Comment: Accepted for publication in Astronomy & Astrophysic