Papers by silvia lorenz-martins
Cuadernos de Educación y Desarrollo
A Educação Inclusiva na perspectiva da Educação Especial está pautada na igualdade de possibilida... more A Educação Inclusiva na perspectiva da Educação Especial está pautada na igualdade de possibilidades e oportunidades da educação para todos. O ensino de Astronomia faz uso majoritariamente de aulas expositivas e de materiais didáticos visuais nas salas de aula. Sendo assim, alunos com deficiência visual podem encontrar barreiras educacionais no acesso às informações, já que necessitam de materiais adaptados a sua necessidade educacional específica. O grupo de pesquisas Universo Acessível, do Observatório do Valongo da Universidade Federal do Rio de Janeiro (UFRJ) junto com o grupo Ciência ao Alcance das Mãos do Instituto Benjamin Constant (IBC) tem desenvolvido em parceria diversos materiais acessíveis a fim de contornar a problemática apresentada no ensino de Astronomia para pessoas com deficiência visual. No âmbito dessa parceria foi produzido um material que aborda os movimentos Terra-Sol-Lua e seus efeitos voltado para alunos dos anos finais do Ensino Fundamental. O recurso didá...
Universo Acessível: expandindo os limites no ensino inclusivo
Fórum UFRJ em Revista
Universo Acessível – um projeto de ensino de astronomia para quem não pode ver com os olhos
A astronomia é uma ciência que em si sempre desperta nas pessoas um interesse especial e independ... more A astronomia é uma ciência que em si sempre desperta nas pessoas um interesse especial e independente de sua origem cultural ou social. Fato que se deve principalmente a questões ligadas a nossa própria existência e nosso lugar no Universo: Como surgiu o Universo? Qual o seu tamanho? São alguns exemplos desses questionamentos. Por seu caráter atrativo, ela é usada como agente motivador no ensino de outras ciências, tais como matemática, por exemplo. Na verdade, a astronomia pode ser considerada como um dos maiores motivadores para despertar o interesse de jovens para as áreas de ciência e tecnologia. De uma maneira geral, há diversos problemas no ensino de Ciências nos níveis Fundamental e Médio e isso se acentua no caso da Astronomia. Para pessoas cegas e com baixa visão, o ensino de Astronomia é ainda mais precário, pois carece de material específico, desenvolvido para suprir essa necessidade. Neste contexto, trabalhos em relevo com diferentes texturas e contraste de cores, impres...
Visitação ao Acervo do Observatório do Valongo/UFRJ: inclusão de visitas para deficientes visuais
O acervo do Observatório do Valongo/UFRJ retrata a história do Instituto: a sua fundação no Morro... more O acervo do Observatório do Valongo/UFRJ retrata a história do Instituto: a sua fundação no Morro de Santo Antônio, a instalação do curso ainda na Faculdade de Filosofia - Universidade do Brasil – sua transferência para o morro da Conceição. Portanto retrata o desenvolvimento do Observatório e também do curso de graduação em Astronomia. O acervo conta com instrumentos científicos que foram construídos entre 1880 e 1920, fotos e documentos desde a criação do Observatório da Escola Politécnica, predecessor do atual OV, em 1881. Desde 1997 o Observatório realiza trabalhos de conservação dos instrumentos e preservação da memória institucional. Em 2007 um convênio institucional com o MAST/MCTI propiciou a restauração e higienização dos instrumentos assim como sua identificação museológica com a criação de fichas técnicas e a publicação de um catálogo. Somado a isso, o acervo foi catalogado na Base Minerva e desenvolvemos um site a fim de expor virtualmente nosso acervo instrumental, mas ...
arXiv: Astrophysics, 2001
We discuss the possibilities of the BaSeL models in its lowest temperature boundary (Teff ~ 2500 ... more We discuss the possibilities of the BaSeL models in its lowest temperature boundary (Teff ~ 2500 K for cool giants) to provide the Teff of AGB stars. We present the first step of our work, by comparing our predictions for the AGB star R Fornacis with the results of Lorenz-Martins & Lefevre (1994) based on the dust spectral energy distribution.
Das Questões, Sep 20, 2018
Esse texto descreve em grandes linhas o projeto em desenvolvimento realizado no observatório do V... more Esse texto descreve em grandes linhas o projeto em desenvolvimento realizado no observatório do Valongo para ensino e divulgação de astronomia para pessoas com deficiência visual.
Etude des enveloppes des etoiles carbonees
Http Www Theses Fr, 1995
Des modeles d'enveloppes d'etoiles froides ont ete calcules pour un ensemble d'etoile... more Des modeles d'enveloppes d'etoiles froides ont ete calcules pour un ensemble d'etoiles carbonees. La methode de monte carlo a ete utilisee pour resoudre le probleme du transfert radiatif dans ces enveloppes. Les modeles ont ete calcules en considerant la presence de deux sortes de grains: le carbure de silicium (sic) et le carbone amorphe (ca). Noupouvons distinguer trois etapes differentes de la modelisation: (1) modelisation d'un ensemble de 9 etoiles carbonees en considerant que les deux sortes de grains sont formees a la meme distance de l'etoile centrale. (2) modelisation d'un ensemble de 32 etoiles carbonees, en considerant cette fois, la formation des differentes sortes de grains a differentes distances de l'etoile centrale. (3) modelisation d'un ensemble d'etoiles carbonees de type j, considerees comme une liaison entre les etoiles m et c dans la sequence evolutive msc. Les modeles donnent la temperature de l'etoile centrale et aussi quelques caracteristiques de l'enveloppe, comme par exemple son extension et son opacite d'extinction. La distribution de la temperature des grains et le rapport d'abondance sic/ca sont aussi obtenus. Des correlations entre le rapport d'abondance sic/ca, l'opacite de l'enveloppe et la periode de variation de l'etoile ont permis de mettre en evidence que la quantite relative de grains de sic, aux grains de ca, diminue avec le stade d'evolution des etoiles carbonees. A partir des modeles, des courbes de visibilite interferometriques ont ete calculees. Elles montrent que la visibilite varie beaucoup a travers la bande d'absorption. Des mesures interferometriques avec resolution spectrale permettraient d'obtenir le profil vrai des bandes d'absorption
Dissecting the bipolar PN Hubble 4
Hubble 4 is a well studied bipolar planetary nebula (PN). It is known to present off-axis spouts,... more Hubble 4 is a well studied bipolar planetary nebula (PN). It is known to present off-axis spouts, known as FLIERs (Fast Low-Ionization Emission Regions), which are inclined by 62 degrees with respect to the main bipolar structure, oriented roughly NS. Only few such objects are known; most FLIERs being aligned with the longest elongation axis of their PN. We retreived
The Spatial Distribution of Grains Around the Dual Chemistry Post-AGB Star Roberts 22
Post-AGB stars are among the most important sources of dust enrichment of the interstellar medium... more Post-AGB stars are among the most important sources of dust enrichment of the interstellar medium. Molster et al. (2002, A&A, 382, 184) investigated the mineralogy and occurrence of crystalline silicate grain features around evolved stars, and concluded that, for the sharpest featured sources, the grains are located in a cool circumstellar envelope, rather than in the matter outflows. As the
Proceedings of the International Astronomical Union, 2009
We present chemical abundances obtained by fitting synthetic spectra to the FEROS data of 12 C-J ... more We present chemical abundances obtained by fitting synthetic spectra to the FEROS data of 12 C-J stars, normal and silicate carbon one. The Li and 13C abundance, as well as the s-process elements abundance indicates no evidence of a diferent mechanism of formation between the two kinds of C-J stars. We also studied the α elements, and that suggests a scenario that put the carbon C-R stars as a possible progenitor of the beither C-J stars. We made also available a study of the radial velocity of some stars of the sample calculated at different epochs. That allowed us to make some discussion about the probable binary system of some silicon C-J carbon stars. Based on these abundances and radial velocities, we discuss possible evolutive sequences for the C-J.
Spectral Analysis of the Pre-WN Candidate HD 326823
The Astronomical Journal, 2007
We present a spectral analysis of the peculiar emission-line star HD 326823. As has been reported... more We present a spectral analysis of the peculiar emission-line star HD 326823. As has been reported in the literature, this object seems to be a rare, massive star entering the Wolf-Rayet (W-R) phase. In order to confirm its evolutionary status, we used the radiative transfer code CMFGEN to obtain its physical parameters and chemical abundances for the first time. By
Evolved stars in the MSX survey (Ortiz+, 2005)
Tables 1 to 3 contain MSX counterparts of carbon-rich stars, transition objects, and planetary ne... more Tables 1 to 3 contain MSX counterparts of carbon-rich stars, transition objects, and planetary nebulae, respectively. The main original catalogues used in the search are: Loup et al. (1993, Cat. ) for carbon-rich stars and Kimeswenger (2001, Cat. ) for planetary nebulae. The search was carried out within a radius of 10 arcseconds from the position listed in the original catalogues. (3 data files).
Monthly Notices of the Royal Astronomical Society, 2000
A set of 31 oxygen-rich stars has been modelled using corundum and silicate grains. These stars w... more A set of 31 oxygen-rich stars has been modelled using corundum and silicate grains. These stars were selected according to their dust-envelope class, as suggested by Little-Marenin and Little in 1990. Then 16 stars classified as Sil were modelled using silicate grains; 10 Broad class stars using corundum (Al 2 O 3) grains; and 5`Intermediate' class stars using two kinds of grain simultaneously: corundum and silicate. The temperature of the central stars and some characteristics of their circumstellar envelopes such as their extinction opacities and extensions were determined by fitting the flux curves. The corundum/silicate ratios as well as the energy distributions and temperature laws have been obtained. Based on the authors' results they suggest the existence of chemical and structural evolution of the modelled circumstellar dust shells. The temperature of the central stars and the temperature of the hottest grains decrease from Broad to Intermediate to Sil classes, while the inner radii and optical depths increase in this sequence.
Mass Loss from …, 2008
Our research aims to disentangle the evolutionary stage of the galactic unclassified B[e] star CD... more Our research aims to disentangle the evolutionary stage of the galactic unclassified B[e] star CD-42 • 11721. New high-and low-resolution optical spectroscopic data are used for a proper derivation of its stellar parameters. Based on these parameters and its location in the HR diagram, we favour a B[e] supergiant nature of CD-42 • 11721.
![Research paper thumbnail of The Optical and IR Properties of Southern Galactic UnclB [E] Stars: The Case of CD-42 11721](https://attachments.academia-assets.com/118079194/thumbnails/1.jpg)
Arxiv preprint astro-ph/ …, 2005
In the last few years, we had devoted our time to the study of a sample of southern unclB[e] star... more In the last few years, we had devoted our time to the study of a sample of southern unclB[e] stars. For most of them, there are few works in the literature, and their physical parameters are still very uncertain. Our research was concentrated on the analysis of the optical and IR data, making use of high (FEROS) and low (B&C) resolution spectra, obtained by us at ESO (La Silla, Chile) and LNA (Brazópolis, Brazil) and using public ISO and IRAS spectra. In this work we will present the results for a curious star: CD-42 • 11721. This object has a doubtful evolutionary stage, being either a pre-main sequence star (HAeB[e]) or an evolved star (supergiant B[e] or sgB [e]). This confusion concerning its nature is caused by the complete absence of reliable physical paramenters for this object, especially its distance. Our optical investigation could be splitted in two parts, a qualitative study based on the identification of the numerous emission lines present in the spectra and the classification of their line profiles, which indicate a non-spherically symmetric circumstellar environment, and a quantitative analysis of numerous forbidden lines, e.g. [Oi], [Oii], [Nii] and [Sii]. Assuming a typical circumstellar scenario for a sgB[e], i.e. a fast, low-density polar wind and a slow, high-density disc forming equatorial wind, we can reproduce very well the line luminosities of the forbidden lines. From this analysis, we can determine the mass loss rate of the star lying in the range from Ṁ ≃ (4.4 ± 0.8) × 10 -6 M ⊙ yr -1 to Ṁ ≃ (2.2 ± 0.4) × 10 -5 M ⊙ yr -1 , depending on the considered redenning. In addition, our IR study could also be splitted in two parts: the identification of several features in the SWS ISO spectrum, and the modeling of the SED of CD-42 • 11721. The first part shows the presence of many unindentified features and specially the presence of a mixed chemistry, i.e. C-and O-rich dust in the same circumstellar medium. The presence of specially C-rich dust could in principle favour a young nature, however this is not so clear, since also other evolved stars like e.g. LBVs, show this kind of dust. We have tried to model the SED, by using a numerical code written by us which considers a spherical circumstellar scenario. Although the answer concerning the evolutionary stage of CD-42 • 11721 is still not very clear, we believe that our analysis will improve the discussion about the nature of this curious star.
Desenvolvimento De Material Tátil Para O Ensino De Astronomia Para Alunos Cegos e Com Baixa Visão
The effects of rapid rotation and bi-stability upon the density contrast between the equatorial a... more The effects of rapid rotation and bi-stability upon the density contrast between the equatorial and polar directions of a B[e] supergiant are investigated. Based on a new slow solution for different high rotational radiation-driven winds and the fact that bi-stability allows a change in the line-force parameters (α, k, and δ), the equatorial densities are about 10 2-10 3 times higher than the polar ones. These values are in qualitative agreement with the observations. This calculation also permits to obtain the aperture angle of the disk.
Linhas do Fe II em B[e] supergigantes
Astronomia Para Todos - Programas e Projetos De Extensão Do Observatório Do Valongo
Juntamente com os cursos de graduacao e pos-graduacao em Astronomia, o Observatorio do Valongo te... more Juntamente com os cursos de graduacao e pos-graduacao em Astronomia, o Observatorio do Valongo tem desenvolvido inumeros projetos de extensao ao longo de sua historia. A interacao com a comunidade iniciou-se no comeco da decada de 1960, sob a forma de cursos de fotografia astronomica, visitacao publica e palestras de divulgacao da Astronomia para escolas dos niveis fundamental e medio. Na decada de 1970, a prestacao de servico a comunidade tornou-se bastante conhecida atraves do Servico da Hora, que fornecia a hora exata por ligacao telefonica com a utilizacao de um relogio atomico. Tambem tiveram grande apelo entre o publico as campanhas de observacao dos cometas Kohoutek, em 1973, e Halley, em 1986. A partir de 1998 as atividades de extensao passaram a ser tratadas como parte de um programa institucional, com coordenadoria propria. Houve a criacao de um programa de atividades noturnas para receber grupos de organizacoes nao governamentais. Devido ao sucesso alcancado, optou-se por...
Monthly Notices of the Royal Astronomical Society, 2017
The presence of dust comae on asteroids and centaurs is a phenomenon that became accepted in the ... more The presence of dust comae on asteroids and centaurs is a phenomenon that became accepted in the last decades and which challenges the traditional definitions of asteroids and comets. A possible way of improving the chances of discovery of active asteroids is to use large multicolour surveys or catalogues, like SDSS Moving Object Catalogue. In this paper, we analyse the effects of faint dust comae on asteroid spectra and then use it to investigate the effects that a faint dust comae would have over the spectrum, magnitude and radial profile of asteroids.
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Papers by silvia lorenz-martins