Model for the coma of Comet Halley, based on the Astron ultraviolet spectrophotometry

International Nuclear Information System (INIS)

Boiarchuk, A.A.; Grinin, V.P.; Petrov, P.P.; Sheikhet, A.I.; Zvereva, A.M.

1986-01-01

The development of a model of the Comet Halley coma from spectral and photometric data is described. Spectra in the 1500-3500 A range and photometric scans at the 3085 A and 2190 A in the (0-0) band of the OH and CO(+) molecules were obtained by the UV telescope of the satellite Astron on December 3, 13, and 23, 1985. Surface-brightness profiles of the coma in the (0-0) band of OH, NH, and CS molecules are derived. The source and formation of these molecules, the lifetime of their radicals, the radial velocity of their parent molecules, and the water-molecule sublimation rate are computed and examined. The basic characteristics of the comet observed from the UV data are compared to the properties of other comets. It is observed that Comet Halley is similar to other large short-period comets. 29 references

A refração atmosférica e os seus problemas nas observações astronômicas

OpenAIRE

Guilherme de Almeida

2014-01-01

http://dx.doi.org/10.5007/2175-7941.2014v31n2p410 Quando apontamos um telescópio na direção de um astro, estamos quase sempre a apontar numa direção mais acima, devido à refração da luz que atravessa a atmosfera da Terra. O fenômeno da refração atmosférica tem diversas implicações prejudiciais nas observações astronômicas, que serão objeto deste artigo.

The Meanings of Astronomical Observation: An Analysis on the Basis of Relationship with Knowledge. (Spanish Title: Los Sentidos de la Observación Astronómica: un Análisis sobre la Base de la Relación con el Saber.) Os Sentidos da Observação Astronômica: Uma Análise com Base na Relação com o Saber

Science.gov (United States)

Klein, Alberto Eduardo; de Mello Arruda, Sergio; Meneghello Passos, Marinez; Vinicius Domenes Zapparoli, Ferdinando

2010-12-01

This article presents results of a research which aimed to understand the meanings that people construct for astronomical observation. The subjects, students and school teachers, initially received some instruction on how to view astronomical objects through the telescope. After the observation was realized, they were interviewed. The data analysis allowed the creation of 12 categories, later interpreted on the basis of relationship with knowledge (relation to the world, with himself and with others), as presented by Bernard Charlot. Este artículo presenta los resultados de una investigación que tuvo como objetivo comprender los sentidos que las personas construyen para la observación astronómica. Los sujetos, los estudiantes y maestros de escuela, recibieron inicialmente algunas instrucciones sobre cómo ver los objetos astronómicos a través del telescopio. Al término de la observación, fueron entrevistados. El análisis de datos permitió la creación de 12 categorías que más tarde fueron interpretadas sobre la base de la relación con el conocimiento (relación con el mundo, consigo mismo y con los demás), tal como presentado por Bernard Charlot. Este artigo apresenta resultados de uma pesquisa que objetivou entender quais os sentidos que as pessoas constroem para a observação astronômica. Os sujeitos da pesquisa, estudantes e professores do ensino médio, receberam inicialmente alguma instrução sobre como visualizar os objetos astronômicos através do telescópio. Após a realização da observação, eles foram entrevistados. A análise dos dados permitiu a elaboração de 12 categorias que foram posteriormente interpretadas com base nas relações com o saber (relação com o mundo, consigo mesmo e com o outro), conforme apresentadas por Bernard Charlot.

A refração atmosférica e os seus problemas nas observações astronômicas

Directory of Open Access Journals (Sweden)

Guilherme de Almeida

2014-05-01

Full Text Available http://dx.doi.org/10.5007/2175-7941.2014v31n2p410 Quando apontamos um telescópio na direção de um astro, estamos quase sempre a apontar numa direção mais acima, devido à refração da luz que atravessa a atmosfera da Terra. O fenômeno da refração atmosférica tem diversas implicações prejudiciais nas observações astronômicas, que serão objeto deste artigo.

Enfoque CTSA no ensino de astronomia: uma investigação de possibilidades por meio da astronáutica

OpenAIRE

Teixeira, Claudio Henrique da Silva [UNESP

2013-01-01

O ensino da astronomia e astronáutica no Brasil, referente à formação de professores, extensão universitária e currículo do ensino básico, pode ter um novo enfoque e uma nova ênfase dada dos seus conteúdos e abordagens. Desde a década de sessenta, currículos de ensino de ciências com ênfase em CTSA - ciência, tecnologia, sociedade e ambiente - vêm sendo desenvolvidos no mundo inteiro. Tais currículos apresentam como objetivo central preparar os alunos para o exercício da cidadania e caracteri...

Nonlinear two-stream interaction between a cold, relativistic electron beam and a collisional plasma-Astron experiment

International Nuclear Information System (INIS)

Newberger, B.S.; Thode, L.E.

1979-05-01

Experiments on the two-stream instability of a relativistic electron beam propagating through a neutral gas, carried out with the Lawrence Livermore Laboratory Astron beam, have been analyzed using a nonlinear saturation model for a cold beam. The behavior of the observed microwave emission due to the instability is in good agreement with that of the beam energy loss. Collisions on the plasma electrons weaken the nonlinear state of the instability but do not stabilize the mode. The beam essentially acts as if it were cold, a result substantiated by linear theory for waves propagating along the beam. In order to predict the effect of both beam momentum scatter and plasma electron collisions on the stability of the mode in future experiments a full two-dimensional linear theory must be developed

Astronomical Perception of the Secondary School's Students in São Paulo's State School in Suzano City. (Spanish Title: Percepción Astronómica de Alumnos de la Enseñanza Media de la Red Estatal de San Pablo en la Ciudad de Suzano.) Percepção Astronômica de um Grupo de Alunos do Ensino Médio da Rede Estadual de São Paulo da Cidade de Suzano

Science.gov (United States)

França de Oliveira, Edilene; Voelzke, Marcos Rincon; Amaral, Luis Henrique

2007-12-01

Although Astronomy is one of the oldest Sciences in the world and many of its concepts are popular, it is possible to observe that a major part of the students do not know about them. This work aims to analyse the basic knowledge of the secondary school's students of a state school in the city of Suzano, related to the astronomical phenomena, which surround them. It was carried out a questionnaire of multiple choice to 34 students from the first grade, night classes, of the state school Batista Renzi. From the sample, 34 students, only 29.4% of them could understand the succession of the days; 20.6% could explain the seasons of the year and 20.6% had some idea about celestial objects nearer to the Earth. In turn, 67.6% correctly classified the Sun as a star; 55.9% related the Big Bang to the origin of Universe; only 20.6% identified the light-year as an unit of distance and 32.4% recognized a falling star as a meteor. The actual analysis was expanded to more 310 students of other classes, grades and periods of the same school. In this first stage, it can be noted the students' little discernment of the astronomical events and mainly the great confusion about the appropriate meaning of popular astronomical terms. Aunque la Astronomía es una de las ciencias más antiguas de la humanidad y muchos de los conceptos astronómicos son populares, se observa que una parcela significativa de los estudiantes se encuentra al margen de estas informaciones. El presente trabajo pretende analizar el nivel de conocimiento básico de los alumnos de la Enseñanza Media de la Red Estatal de la ciudad de Suzano con relación a los fenómenos astronómicos que los rodean. Con este objetivo fue elaborado un formulario constando de preguntas de selección múltipla, aplicado en el primer año nocturno de la Escuela Estatal Batista Renzi. En un universo de 34 alumnos se constató que solamente 29,4% comprendían la sucesión de los días; 20,6% explicaron correctamente las estaciones del

Como os Alunos do Ensino Médio da Rede Estadual de São Paulo obtém Conhecimentos Astronômicos?

Science.gov (United States)

da Cunha, W. S.; Voelzke, M. R.; Amaral, L. H.

2005-08-01

Atualmente vivencia-se um mundo globalizado onde os computadores e a internet permitiram um acesso rápido e seguro a todo tipo de informação e conhecimento. O presente trabalho visa analisar a maneira pela qual alunos de segundo grau da rede estadual da cidade de São Paulo obtiveram, caso tenham, conhecimentos básicos de astronomia quanto aos fenômenos celestes que os rodeiam, tais como a sucessão dos dias e das estações do ano, além de questioná~los sobre fatos genéricos tais como: o que vem a ser o Sol, o Big Bang, o que ocasionou a extinção dos dinossauros. Para tanto foi elaborado um formulário constando de questões de múltipla escolha, o qual foi aplicado no primeiro colegial diurno da Escola Estadual Guilherme de Almeida. Num espaço amostral de 44 alunos constatou-se que 41% dos alunos adquiriram seus conhecimentos astronômicos na escola e 59% através da mídia em geral. Neste mesmo espaço amostral apenas 11% dos alunos usaram computadores na escola, 41% na residência, 5% no trabalho e 43% não utilizaram. O presente estudo revelou também que para 50% dos alunos o professor jamais utilizou um programa de computador a respeito de astronomia ou fez alguma apresentação sobre o tema. Embora em sua fase inicial este estudo revela claramente que a maioria dos alunos não obtém na escola seus conhecimentos astronômicos, estes provém de fontes não especificamente didático-pedagógicas tais como filmes e revistas populares que não raramente geram conhecimentos incompletos e em muitos casos inclusive falhos.

Qual o Papel da Escola e da Mídia na Obtenção dos Conhecimentos Astronômicos?

Science.gov (United States)

da Cunha, W. S.; Voelzke, M. R.; Amaral, L. H.

2007-08-01

É amplamente reconhecido que as pessoas em geral têm grande fascínio e interesse pela Astronomia. Por outro lado, o conteúdo dessa área incluído no ensino formal está longe de ser abrangente e suficiente para suprir a demanda. Esse interesse permite aperfeiçoar a divulgação e o ensino não formal de Astronomia através da mídia aliando a adequação do conteúdo à expectativa das pessoas. A reforma do Currículo Básico da Escola Pública da maioria dos Estados brasileiros tem introduzido Astronomia desde a pré-escola até o Ensino Médio. Num estudo realizado com 1180 alunos do Ensino Médio de seis escolas estaduais, revelou-se através da aplicação de um formulário contendo questões que abordavam conhecimentos básicos em Astronomia, como foram adquiridos tais conhecimentos e à infra-estrutura da escola. Para 66,1% dos entrevistados o professor já fez alguma apresentação a respeito de Astronomia. O presente estudo revelou também que 54,4% dos alunos entrevistados adquiriram seus conhecimentos astronômicos na escola, 18,4% através da televisão e 27,1% afirmaram que seus conhecimentos foram obtidos através de outros tipos de mídia (internet, livros didáticos, filmes e revistas). Embora o estudo revele claramente que há certo equilíbrio no meio em que os alunos obtiveram seus conhecimentos astronômicos, a mídia busca não somente sua difusão, mas a disponibilização desse conhecimento de maneira correta, que às vezes, não é atingido, apresentando conceitos sem fundamentação e incorretos. Por outro lado, no dia-a-dia escolar, é comum encontrar professores que vêm para as aulas com concepções prévias, que podem diferir substancialmente das idéias a serem ensinadas, dificultando o aprendizado de futuros conceitos científicos. Uma avaliação criteriosa, avaliando as dificuldades dos professores em determinar o sentido correto dos conceitos e observando a metodologia que utilizam no ensino, poderá proporcionar uma melhor

Péndulos astronómicos y cronómetros marinos de la armada: el observatorio de San Fernando y los antecedentes del patrón nacional de tiempo (1753-1957

Directory of Open Access Journals (Sweden)

González González, Francisco José

1998-06-01

Full Text Available This article is a brief review on the precision clocks in use by the Spanish Navy during the XVIII, XIX and XX centuries. It deals with the introduction in Spain of marine chronometers needed for the application of the new techniques of astronomical navigation and also, with the evolution of the methods for time keeping and determination by astronomical pendulum clocks. Both facts placed the Navy and its Observatory in a good starting position for future activity in the field of the scientific study of time in our country.

Este artículo presenta un breve estudio sobre los relojes de precisión usados por la Armada española durante los siglos XVIII, XIX y XX. Se trata, por una parte, sobre la introducción en España de los cronómetros marinos, necesarios para la aplicación de las nuevas técnicas de navegación astronómica. Se estudia, además, la evolución del sistema de determinación y conservación de la hora mediante péndulos astronómicos, origen del servicio horario del Observatorio de San Femando. Ambas vertientes sitúan a la Marina, y a su Observatorio, en un lugar preferente en los trabajos relacionados con el cómputo científico del tiempo en nuestro país.

A Reappraising of Cosmography: the Interface Between Astronomical and Geographic Studies. (Breton Title: Releitura do Conceito de Cosmografia: a Interface Entre os Estudos Astronômicos e Geográficos.) Una Relectura del Concepto de Cosmografía: la Interfase Entre los Estudios Astronómicos y Geográficos

Science.gov (United States)

Azevedo Sobreira, Paulo Henrique

2012-12-01

The concept of "Cosmography" is in disuse since the 80s of the last century, but the astronomical themes previously discussed in the school subjects of Geography and Cosmography remain in current textbooks. The use of term "Cosmography" was rescued in this research, and the study of its re-signification prompted the appearance of the term Geographic Cosmography. The Geographic Cosmography is a field of studies of the Geography, whose set of knowledge and skills is predominantly scholar. It studies the interface between terrestrial and celestial knowledge, and assigns a geographic significance to them. It examines human and natural relationships with Sidereal Space and its consequences for society and nature. O conceito de "Cosmografia" está em desuso desde os anos 80 do século XX, mas os temas astronômicos anteriormente abordados nas disciplinas escolares de Cosmografia e de Geografia permanecem nos atuais livros didáticos. O uso do termo "Cosmografia" foi resgatado nesta pesquisa e o estudo de sua ressignificação proporcionou o surgimento do termo Cosmografia Geográfica. A Cosmografia Geográfica é um campo de estudos da Geografia, cujo conjunto de conhecimentos e habilidades é predominantemente escolar. Estuda a interface entre os conhecimentos terrestres e os celestes e lhes atribui significância geográfica. Analisa as relações humanas e naturais com o Espaço Sideral e suas consequências para a sociedade e a natureza. Aunque el concepto de "Cosmografía" no se usa desde la década de los '80 del siglo pasado, los temas astronómicos que se enseñaban anteriormente en las asignaturas escolares de Cosmografía y de Geografía permanecen en los actuales libros didácticos. El uso del término "Cosmografía" fue rescatado en esta investigación y el estudio de su resignificación proporcionó el surgimiento del término Cosmografía Geográfica. La Cosmografía Geográfica es un campo de estudio de la Geografía, donde el conjunto de conocimientos y

PSR B0329+54: substructure in the scatter-broadened image discovered with RadioAstron on baselines up to 330 000 km

Science.gov (United States)

Popov, Mikhail V.; Bartel, Norbert; Gwinn, Carl R.; Johnson, Michael D.; Andrianov, Andrey; Fadeev, Evgeny; Joshi, Bhal Chandra; Kardashev, Nikolay; Karuppusamy, Ramesh; Kovalev, Yuri Y.; Kramer, Michael; Rudnitskiy, Alexey; Shishov, Vladimir; Smirnova, Tatiana; Soglasnov, Vladimir A.; Zensus, J. Anton

2017-02-01

We have resolved the scatter-broadened image of PSR B0329+54 and detected a substructure within it. These results are not influenced by any extended structure of a source but instead are directly attributed to the interstellar medium. We obtained these results at 324 MHz with the ground-space interferometer RadioAstron, which included the Space Radio Telescope, ground-based Westerbork Synthesis Radio Telescope and 64-m Kalyazin Radio Telescope on baseline projections up to 330 000 km in 2013 November 22 and 2014 January 1 to 2. At short 15 000 to 35 000 km ground-space baseline projections, the visibility amplitude decreases with baseline length, providing a direct measurement of the size of the scattering disc of 4.8 ± 0.8 mas. At longer baselines, no visibility detections from the scattering disc would be expected. However, significant detections were obtained with visibility amplitudes of 3 to 5 per cent of the maximum scattered around a mean and approximately constant up to 330 000 km. These visibilities reflect a substructure from scattering in the interstellar medium and offer a new probe of ionized interstellar material. The size of the diffraction spot near Earth is 17 000 ± 3 000 km. With the assumption of turbulent irregularities in the plasma of the interstellar medium, we estimate that the effective scattering screen is located 0.6 ± 0.1 of the distance from the Earth towards the pulsar.

Análise dos Conceitos Astronômicos Apresentados por Professores de Algumas Escolas Estaduais Brasileiras

Science.gov (United States)

Voelzke, Marcos Rincon; Gonzaga, Edson Pereira

2011-12-01

A razão para o desenvolvimento deste trabalho baseia-se no fato de que muitos professores da Educação Básica (EB) não lidam com conceitos relacionados à astronomia, e quando o fazem eles simplesmente seguem livros didáticos que podem conter erros conceituais. Como é de conhecimento geral a astronomia é um dos conteúdos a serem ensinados na EB fazendo parte dos Parâmetros Curriculares Nacionais e das Propostas Curriculares do Estado de São Paulo, mas é um fato, que vários pesquisadores apontam, a existência de muitos problemas no ensino da astronomia. Com o propósito de minimizar algumas dessas deficiências foi realizado um trabalho de pesquisa com a utilização de questionários pré e pós pesquisa, para tanto foi desenvolvido um Curso de Extensão Universitária para professores da Diretoria de Ensino Regional (DE) que abrange Mauá, Ribeirão Pires e Rio Grande da Serra (no Estado de São Paulo) com os seguintes objetivos: levantar concepções alternativas; subsidiar os professores por meio de palestras, debates e workshops, e verificar o sucesso da aprendizagem após o curso, adotando-se como referência, para a análise dos resultados, os dicionários de Língua Portuguesa (FERREIRA, 2004) e Enciclopédico de Astronomia e Astronáutica (MOURĀO, 1995). Portanto, dezesseis questões foram aplicadas antes e após o curso, assim pode-se verificar após a pesquisa que 100,0% dos professores sabiam os nomes das fases da Lua, 97,0% entenderam que o Sistema Solar é composto por oito planetas, 78,1% foram capazes de explicar como ocorre um eclipse lunar, um eclipse solar e um solstício, 72,7% sabiam como explicar a ocorrência das estações do ano; 64,5% explicaram corretamente a ocorrência do equinócio, 89,7% foram capazes de definir adequadamente o termo cometa; 63,6% definiram asteróide, 54,5% meteoro, 58,1% galáxia, e 42,4% planeta. Os resultados obtidos indicam uma aprendizagem significativa por parte dos participantes.

PSR B0329+54: Statistics of Substructure Discovered within the Scattering Disk on RadioAstron Baselines of up to 235,000 km

Science.gov (United States)

Gwinn, C. R.; Popov, M. V.; Bartel, N.; Andrianov, A. S.; Johnson, M. D.; Joshi, B. C.; Kardashev, N. S.; Karuppusamy, R.; Kovalev, Y. Y.; Kramer, M.; Rudnitskii, A. G.; Safutdinov, E. R.; Shishov, V. I.; Smirnova, T. V.; Soglasnov, V. A.; Steinmassl, S. F.; Zensus, J. A.; Zhuravlev, V. I.

2016-05-01

We discovered fine-scale structure within the scattering disk of PSR B0329+54 in observations with the RadioAstron ground-space radio interferometer. Here we describe this phenomenon, characterize it with averages and correlation functions, and interpret it as the result of decorrelation of the impulse-response function of interstellar scattering between the widely separated antennas. This instrument included the 10 m Space Radio Telescope, the 110 m Green Bank Telescope, the 14 × 25 m Westerbork Synthesis Radio Telescope, and the 64 m Kalyazin Radio Telescope. The observations were performed at 324 MHz on baselines of up to 235,000 km in 2012 November and 2014 January. In the delay domain, on long baselines the interferometric visibility consists of many discrete spikes within a limited range of delays. On short baselines it consists of a sharp spike surrounded by lower spikes. The average envelope of correlations of the visibility function shows two exponential scales, with characteristic delays of {τ }1=4.1+/- 0.3 μ {{s}} and {τ }2=23+/- 3 μ {{s}}, indicating the presence of two scales of scattering in the interstellar medium. These two scales are present in the pulse-broadening function. The longer scale contains 0.38 times the scattered power of the shorter one. We suggest that the longer tail arises from highly scattered paths, possibly from anisotropic scattering or from substructure at large angles.

Power Spectrum Density of Stochastic Oscillating Accretion Disk GB ...

Indian Academy of Sciences (India)

J., 672, 40. Harko, T., Mocanu, G. R. 2012, Mon. Not. R. Astron. Soc., 421, 3102. Jauncey, D. L., Macquart, J. P. 2001, Astron. Astrophys., 370, L9. Kato, S. 2001, Publ. Astron. Soc. Jpn., 53, 1. Leung, C. S., Wei, J. Y., Harko, T. et al. 2011a, J. Astrophys. Astr., 32, 189. Leung, C. S., Wei, J. Y., Kovacs, Z. et al. 2011b, Res. Astron.

Mediciones de irradiancia solar y capa de ozono durante el eclipse de Sol de 1994 en el Observatorio Astronómico de Rosario, Argentina

Science.gov (United States)

Piacentini, R. D.; Micheletti, M. I.

We show results of measurements made during the Sun's eclipse of November 3, 1994, in Observatorio Astronómico de Rosario (32o 57' S, 60o 37' W, 25 m a.s.l.). The eclipse begin at 8:41 local hour, reached its maximum with 77% of the surface covered at 9:51 and finished at 11:04. The direct solar irradiance of 300 nm and 313 nm were able to be measured, due to the fact that during the whole period the sky remained completed uncovered (zero percent cloudiness). The measurements were made with the portable ozonometer developed by Tocho and co-workers. They show the characterictic decrease due to the occultation of the source, which is approximately proportional to the surface's diminution. When crossing the earth's atmosphere to arrive to the observation point, these irradiances are affected mainly by the ozone layer, specially the irradiance at lower wavelength, what let it to determine by comparison the thickness of this layer. The total ozone thickness distributed between the troposphere and the stratosphere shows an oscillation, whose amplitude, since the occurence of the maximum of occulation, has a mean value of 4%, and whose period is of approximately 2100 seconds, being both numbers considerably larger than the ones registred by Mims III y Mims (Geophysical Research Letters, 20, 367, 1993) during the eclipse of July 11, 1991 and by Tocho, Da Silva y Rivas (XVIII Quadriennial Ozone Symposiom, Italy, September, 1996) during the same eclipse analyzed in the present work, but observed in Salta. As complementary results, we measured the global irradiance and the ambient temperature during this astronomical event.

Sobre os céus e as marés do Pacífico: as observações astronômicas do jesuíta Nicolás Mascardi (Chile, século XVII

Directory of Open Access Journals (Sweden)

Eliane Cristina Deckmann Fleck

2014-12-01

Full Text Available A atuação da Companhia de Jesus na América espanhola e portuguesa constitui-se em tema de várias investigações e obras, nas quais merece destaque a dedicação de seus religiosos ao ensino e à catequese. Alguns membros da Ordem, no entanto, se dedicaram, também, a observações de fenômenos naturais, da fauna e da flora nativas e, ainda, a aspectos da geografia dos territórios em que atuaram, legando-nos uma série de estudos informados através de cartas, relatórios ou obras. Nosso propósito neste artigo é o de apresentar e analisar os registros que o padre jesuíta italiano Nicolás Mascardi fez de suas observações astronômicas e, em especial, do estudo que realizou sobre as marés do arquipélago de Chiloé durante os anos em que atuou na então Vice-Província Jesuítica do Chile, no século XVII.

List of Registered Participants

Indian Academy of Sciences (India)

user1

Heald, George. ASTRON heald@astron.nl. Hoeft, Matthias. Thueringer Landessternwarte Tautenburg hoeft@tls-tautenburg.de. Ishwara Chandra, C. H.. NCRA-TIFR ishwar@ncra.tifr.res.in. Johnston-Hollitt, Melanie. School of Chemical & Physical Sciences. Melanie.Johnston-Hollitt@vuw.ac.nz. Jacob, Joe. Newman College.

The nature of dark matter

Energy Technology Data Exchange (ETDEWEB)

Kirillov, A.A. [Institute for Applied Mathematics and Cybernetics, 10 Uljanova Str., Nizhny Novgorod 603005 (Russian Federation)]. E-mail: ka98@mail.ru

2006-01-19

The observed strong dark-to-luminous matter coupling [F. Donato, et al., astro-ph/0403206, Mon. Not. R. Astron. Soc., submitted for publication; G. Gentile, et al., Mon. Not. R. Astron. Soc. 351 (2004) 903; D.T.F. Weldrake, et al., Mon. Not. R. Astron. Soc. 340 (2003) 12; W.J.G. de Blok, A. Bosma, Astron. Astrophys. 385 (2002) 816; O. Gerhard, et al., Astrophys. J. 121 (2001) 1936; A. Borriello, et al., Mon. Not. R. Astron. Soc. 341 (2003) 1109] suggests the existence of a some functional relation between visible and DM sources which leads to biased Einstein equations. We show that such a bias appears in the case when the topological structure of the actual Universe at very large distances does not match properly that of the Friedman space. We introduce a bias operator {rho}{sub DM}=B-bar {rho}{sub vis} and show that the simple bias function b=1/(4{pi}r{sub 0}r{sup 2}){theta}(r-r{sub max}) (the kernel of B-bar ) allows to account for all the variety of observed DM halos in astrophysical systems. In galaxies such a bias forms the cored DM distribution with the radius R{sub C}{approx}R{sub opt} (which explains the recently observed strong correlation between R{sub C} and R{sub opt} [F. Donato, et al., astro-ph/0403206, Mon. Not. R. Astron. Soc., submitted for publication]), while for a point source it produces the logarithmic correction to the Newton's potential (which explains the observed flat rotation curves in spirals). Finally, we show that in the theory suggested the galaxy formation process leads to a specific variation with time of all interaction constants and, in particular, of the fine structure constant.

A Hot White Dwarf Luminosity Function from the Sloan Digital Sky Survey

Science.gov (United States)

2009-01-01

Berro, E., Torres, S., & Catalan, S. 2008, ApJ, 682, L109 Ivezic, Z., Lupton, R. H., Schlegel, D., et al. 2004, Astron. Nachrichten , 325, 583...et al. 2002, AJ, 123, 485 Tucker, D., Kent, S., Richmond, M. W., et al. 2006, Astron. Nachrichten , 327, 821 Vennes, S. 1999, ApJ, 525, 995 Vennes, S

NASA's Astronant Family Support Office

Science.gov (United States)

Beven, Gary; Curtis, Kelly D.; Holland, Al W.; Sipes, Walter; VanderArk, Steve

2014-01-01

During the NASA-Mir program of the 1990s and due to the challenges inherent in the International Space Station training schedule and operations tempo, it was clear that a special focus on supporting families was a key to overall mission success for the ISS crewmembers pre-, in- and post-flight. To that end, in January 2001 the first Family Services Coordinator was hired by the Behavioral Health and Performance group at NASA JSC and matrixed from Medical Operations into the Astronaut Office's organization. The initial roles and responsibilities were driven by critical needs, including facilitating family communication during training deployments, providing mission-specific and other relevant trainings for spouses, serving as liaison for families with NASA organizations such as Medical Operations, NASA management and the Astronaut Office, and providing assistance to ensure success of an Astronaut Spouses Group. The role of the Family Support Office (FSO) has modified as the ISS Program matured and the needs of families changed. The FSO is currently an integral part of the Astronaut Office's ISS Operations Branch. It still serves the critical function of providing information to families, as well as being the primary contact for US and international partner families with resources at JSC. Since crews launch and return on Russian vehicles, the FSO has the added responsibility for coordinating with Flight Crew Operations, the families, and their guests for Soyuz launches, landings, and Direct Return to Houston post-flight. This presentation will provide a summary of the family support services provided for astronauts, and how they have changed with the Program and families the FSO serves. Considerations for future FSO services will be discussed briefly as NASA proposes one year missions and beyond ISS missions. Learning Objective: 1) Obtain an understanding of the reasons a Family Support Office was important for NASA. 2) Become familiar with the services provided for astronauts and their families and how they changed with the Program and family needs.

On the Maximum Separation of Visual Binaries M. I. Nouh1,∗ & M. A. ...

Indian Academy of Sciences (India)

Stars, http://www.ad.usno.navy.mil/wds/orb6/orb6.html. Kuiper, G. P. 1935, Publ. Astron. Soc. Pacific., 47(15), 12. Öpik, E. 1924, Publ. Obs. Astro. Univ. Tartu., 25, 6. Press, W. H., Teukolsky, S. A., Vetterling, W. H., Flannery, B.P. 1992, Numerical Recipes. (Cambridge Univ. Press). Reed, B. C. 1984, J. R. Astron. Soc. Can.

Influencia de la marea astronómica sobre las variaciones del nivel del Río Negro en la zona de Carmen de Patagones

Directory of Open Access Journals (Sweden)

Enrique D'Onofrio

2010-12-01

Full Text Available El Río Negro, límite natural entre las provincias de Buenos Aires y Río Negro, es uno de los ríos más importantes de la Patagonia que desemboca en el Océano Atlántico. Es navegable desde su desembocadura hasta Carmen de Patagones por embarcaciones de hasta 2,04 m de calado, dificultándose por irregularidades en la profundidad aguas arriba. La onda de marea proveniente del océano Atlántico ingresa al río haciendo que este adopte un régimen semidiurno hasta Carmen de Patagones. El conocimiento de la onda de marea en este tramo del río es de fundamental importancia para la calibración de modelos numéricos, el perfeccionamiento de los sistemas de alerta de inundaciones y la toma de decisiones relacionadas con el manejo costero. En este trabajo se analizan cuatro series de mediciones de marea, dos obtenidas en el hidrómetro de Carmen de Patagones con una duración de 608 y 731 días, una de 77 días proveniente de un mareómetro instalado en el kilómetro 18 del río y una de 79 días obtenida con un sensor de presión fondeado en proximidades de Punta Redonda (desembocadura del Río Negro. Se calculan y comparan los espectros de potencia de las alturas observadas en los tres sitios para detectar los cambios energéticos producidos en la banda de frecuencias correspondientes a la marea astronómica. De su comparación surge que la energía de las componentes semidiurnas y diurnas disminuye un 22% y un 45% respectivamente desde la desembocadura del Río Negro hasta Carmen de Patagones. En contraposición se observa un ligero aumento de la energía correspondiente a las frecuencias de las componentes cuarto diurnas. Esto se debe fundamentalmente a procesos no lineales inducidos por aguas someras y a irregularidades en la morfología del fondo del río. Para obtener las amplitudes y épocas de la marea se realizan análisis armónicos por el método de cuadrados mínimos. Las amplitudes de las componentes diurnas en Carmen de Patagones

A3. 408 MHz radio continuum flux at mod(b) 0

International Nuclear Information System (INIS)

Haslam, C.G.T.

1983-01-01

The map shows the radio continuum brightness at a frequency of 408 MHz (lambda73 cm). The atlas of the all-sky survey published by Haslam et al. contains data from four surveys, made with the Jodrell Bank Mk I (anticenter region), the Bonn 100-m (-8 0 0 ), the Parkes 64-m (southern sky), and the Jodrell Bank Mk I A (north celestial pole region) telescopes. The respective references for the four component surveys are Haslam, Quigley, and Salter, 1970, Mon. Not. R. Astron. Soc. 147, 405; Haslam, Wilson, Graham, and Hunt, 1974, Astron. Astrophys. Suppl. Ser. 13, 359; Haslam, Wilson, Cooke, Cleary, Graham, Wilelebinski, and Day, 1975, Proc. ASA 2 (6), 331; and Haslam, Klein, Salter, Stoffel, Wilson, Cleary, Cooke, and Thomasson, 1981, Astron. Astrophys. 100, 209. The angular resolution of the original data base is 0 0 .85. For the map in galactic coordinates produced here, the data have been smoothed and placed on a 2 0 rectangular grid. The contours represent brightness temperature labelled in Kelvins. (Auth.)

Astronomía en la cultura

Science.gov (United States)

López, A.; Giménez Benitez, S.; Fernández, L.

La Astronomía en la Cultura es el estudio interdisciplinario a nivel global de la astronomía prehistórica, antigua y tradicional, en el marco de su contexto cultural. Esta disciplina abarca cualquier tipo de estudios o líneas de investigación en que se relacione a la astronomía con las ciencias humanas o sociales. En ella se incluyen tanto fuentes escritas, relatos orales como fuentes arqueológicas, abarcando entre otros, los siguientes temas: calendarios, observación práctica, cultos y mitos, representación simbólica de eventos, conceptos y objetos astronómicos, orientación astronómica de tumbas, templos, santuarios y centros urbanos, cosmología tradicional y la aplicación ceremonial de tradiciones astronómicas, la propia historia de la astronomía y la etnoastronomía (Krupp, 1989) (Iwaniszewski, 1994). En nuestro trabajo abordamos la historia y situación actual de esta disciplina, sus métodos y sus relaciones con otras áreas de investigación.

Pre-astronomica navigation in antiquity: the use of birds for nautical orientation | La navegación pre-astronómica en la antigüedad: utilización de pájaros en la orientación náutica

Directory of Open Access Journals (Sweden)

José María Luzón Nogué

1986-12-01

Full Text Available This paper deals with the use of birds (ravens and doves as attendants of the sailors to search the coast from the sea. This use is documented since the III millennium B. C. in the Aegean Sea. The possibilities and limitations of this art of sailing are very important to the cultural interrelationship in the Mediterranean. An experience performed in 1986 has allowed us to verify the efficiency of the birds to guide sailors in high sea. The astronomical orientation assumes the possibility of big return routes, which are radically changing the cultural and economic panorama of the Mediterranean since the I millennium B. C. | El presente estudio reúne los datos referentes a la utilización de pájaros (preferentemente cuervos y palomas como auxiliares de los navegantes, para buscar la costa desde alta mar. Su utilización está documentada desde el tercer milenio a. C. en Oriente y durante el segundo milenio a. C. en el Egeo. De las posibilidades y limitaciones de esta forma de navegar depende en gran medida la interrelación cultural en el Mediterráneo. Un experimento practicado realizado en 1986 permite comprobar la eficacia de la suelta de aves para orientar a los navegantes que se pierden en alta mar. La orientación astronómica supone la posibilidad de grandes rutas de ida y vuelta que van a cambiar radicalmente el panorama cultural y económico del Mediterráneo a partir del primer milenio a. C.

Percepção astronómica de um grupo de alunos do ensino médio de uma escola da rede estadual de São Paulo

Science.gov (United States)

de Oliveria, E. F.; Voelzke, M. R.

2009-03-01

Sendo a Astronomia uma das cièncias mais antigas da humanidade, e considerando sua importáncia histórica e cultural, é de extrema releváncia que tópicos relacionados a ela sejam tratados nas escolas. Embora os Parámetros Curriculares Nacionais do Ensino Médio (PCN-EM) e as Orientaçiacute;es Complementares aos Parámetros (PCN+) apontem a importáncia de uma abordagem significativa de conceitos relacionados à Astronomia nas aulas de Física, muitos estudantes terminam o Ensino Médio (EM) sem compreender a razão de certos acontecimentos de origem celeste, ainda que estes façam parte de seu cotidiano e sejam alvos da curiosidade natural dos jovens. Da observação dessa curiosidade em alunos de uma escola pública paulista, na cidade de Suzano, surgiu o interesse em investigar os conhecimentos básicos em Astronomia dos alunos do Ensino Médio desta escola, constituindo-se este como principal objetivo desta pesquisa. Para tanto foi elaborado um questionário de múltipla escolha aplicado inicialmente a 34 alunos do primeiro ano e, posteriormente, a mais 310, distribuídos entre as très séries do Ensino Médio dos períodos matutino e noturno. Dessa forma, observou-se que 73,9% dos estudantes identificaram o Sol como sendo uma estrela, 67,1% mostraram compreender a sucessão entre dia e noite e 52,3% relacionaram o Big Bang à origem do Universo. Em contrapartida, apenas 34,5% relacionaram as estaçíes do ano à inclinação do eixo de rotação da Terra, 21,3% indicaram a influència gravitacional simultánea da Lua e do Sol como responsável pelo fenòmeno das marés, 24,5% indicaram corretamente quais são os objetos celestes mais próximos da Terra, 36,1% identificaram ano-luz como uma medida de distáncia e 34,2% reconheceram as estrelas cadentes como meteoros, evidenciando-se assim o pequeno discernimento dos estudantes quanto aos fenòmenos e termos astronòmicos do cotidiano. Além disso, foram comparadas as respostas de alun! os de diferentes s

La geodesia y la investigación científica en la Francia del Siglo XIX la medición del arco de meridiano franco-argelino (1870-1895

Directory of Open Access Journals (Sweden)

Martina Schiavon

2004-07-01

Full Text Available En el siglo XIX la geodesia era fundamental para la astronómia y las ciencias de la tierra (cartografía, geología, geofísica y también para las disciplinas militares. En las opéraciones de medida de un arco de meridiano, de paralelo o de la posición astronómica de una estación geodésica, los oficiales militares han utilizado en el terreno las "técnicas" materiales y conceptuales que fueron creadas para observar las estrellas. En consecuencia, ellos han adaptado y modificado los conocimientos característicos del observatorio para medir los objetos terrestres. Sin embargo, los historiadores han raramente investigado la geodesia como una actividad del observatorio astronómico. En este articulo, considerando la geodesia como una actividad humana y una disciplina en la cual el astronomo y el oficial militar colaboraron, me propongo explorar los trabajos de terreno en geodesia y mostrar que las medidas de precisión de terreno constituyen una esfera sociológica, material y cognitiva por excelencia. Tomaré como ejemplo la medida de un arco de meridiano realizada bajo la dirección del capitán Francois Perrier, en Francia y Argelia entre 18701' 1895. PAIABRAS erAVES. Geodesia, medida y cultura de la precisión, ejército, XIX siglo, Francia

The Tayler instability at low magnetic Prandtl numbers: between chiral symmetry breaking and helicity oscillations

International Nuclear Information System (INIS)

Weber, Norbert; Galindo, Vladimir; Stefani, Frank; Weier, Tom

2015-01-01

The Tayler instability is a kink-type, current driven instability that plays an important role in plasma physics but might also be relevant in liquid metal applications with high electrical currents. In the framework of the Tayler–Spruit dynamo model of stellar magnetic field generation (Spruit 2002 Astron. Astrophys. 381 923–32), the question of spontaneous helical (chiral) symmetry breaking during the saturation of the Tayler instability has received considerable interest (Zahn et al 2007 Astron. Astrophys. 474 145–54; Gellert et al 2011 Mon. Not. R. Astron. Soc. 414 2696–701; Bonanno et al 2012 Phys. Rev. E 86 016313). Focusing on fluids with low magnetic Prandtl numbers, for which the quasistatic approximation can be applied, we utilize an integro-differential equation approach (Weber et al 2013 New J. Phys.15 043034) in order to investigate the saturation mechanism of the Tayler instability. Both the exponential growth phase and the saturated phase are analysed in terms of the action of the α and β effects of mean-field magnetohydrodynamics. In the exponential growth phase we always find a spontaneous chiral symmetry breaking which, however, disappears in the saturated phase. For higher degrees of supercriticality, we observe helicity oscillations in the saturated regime. For Lundquist numbers in the order of one we also obtain chiral symmetry breaking of the saturated magnetic field. (paper)

Adventures in order and chaos : a scientific autobiography

Science.gov (United States)

Contopoulos, George

The field of Order and Chaos had a remarkable expansion in the last 50 years. The main reason was the use of computers, and the development of new theoretical methods that we call now 'the theory of chaos'. The author describes this fascinating period in a relaxed and sometimes humorous autobiographical way. He relates his interactions with many people in dynamical astronomy and he quotes several anecdotes from these interactions. He refers also to his experiences when he served in various international positions, such as general secretary of the IAU and chairman of the journal Astronomy and Astrophysics. In recent years the theory of chaos has been extended to new areas, like relativity, cosmology and quantum mechanics and it continues expanding in almost all branches of physics. The book describes many important ideas in this field in a simple way. It refers also to problems of more general interest, like writing papers and giving lectures and the interaction of authors and referees. Finally it gives some useful prospects for the future of dynamical astronomy and related fields. George Contopoulos, PhD U.Athens1953; Professor of Astronomy U.Thessaloniki 1957-75; U.Athens 1975-96; Emeritus 1996-; Member, Academy of Athens 1997-. Visiting Professor Yale U., Harvard U., MIT, Cornell U., U.Chicago, U.Maryland, U. Florida, Florida State U., U. Milan; Res. Associate, Yerkes Obs., Inst.Adv.Study Princeton, Inst.Space Studies, Goddard Flight Center, Columbia U., ESO. Author or Editor of 15 books, and about 250 papers on Galactic Dynamics, Relativity and Celestial Mechanics. Positions held: Gen.Secretary of the IAU; Director General Nat.Obs.of Greece, Pres.Hellenic Astron.Soc.; Nat.Representative of Greece in NATO, etc. Distinctions: Amer. Astron.Soc. Brouwer Prize; U.Chicago, Honorary Doctor's Degree; IAU, Pres. Commission 33 (Galaxy); Member Academia Europaea; Associate Royal Astron. Soc.; Chairman of the European Journal "Astronomy and Astrophysics"; Assoc. Editor of

Segundo Catálogo Estelar del Hemisferio Sur con Astrolabio Fotoeléctrico PAII

Science.gov (United States)

Manrique, W. T.; Podestá, R. C.; Alonso, E.; Actis, E. V.; Pacheco, A. M.; Bustos, G.; Lizhi, L.; Zezhi, W.; Fanmiao, Z.; Hongqi, W.; Perdomo, R.

Recordamos que entre el Observatorio Astronómico ``Félix Aguilar'', el Observatorio Astronómico de Beijing y el Observatorio Astronómico de La Plata, se ha convenido en desarrollar un Proyecto de Investigación conjunto, para la observación sistemática de estrellas en el Hemisferio Sur, con el objeto de la elaboración de un Catálogo Estelar Global utilizando un Astrolabio Fotoeléctrico PAII del Observatorio de Beijing, que ha sido usado con éxito en la República de China. En este trabajo se presenta el Segundo Catálogo Estelar del Hemisferio Sur, derivado de las observaciones realizadas con el PAII instalado en el OAFA, durante el períiodo Febrero de 1992 a Marzo de 1997. En este lapso se han observado mas de 400000 pasajes estelares, obteniéndose las correcciones Δ α y Δ δ de 5241 estrellas del FK4, FK5, FK5 Ext., SRS, CAMC y GC. Las precisiones medias son del orden de ± 3,2 ms en ascensión recta y ±0."057 en declinación. Rango de magnitudes : 2,0 a 11,5 Rango de declinaciones : -3o a -60o Epoca Media : 1994.9 Se analizan los residuos en función de la magnitud y tipo espectral, correcciones de grupo y frecuencia de distribución Δ α y Δ δ.

Studies of Clump Structure of Photodissociation Regions at ...

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

1992); Meixner & Tielens (1993); Robert & Pagani (1993); Bennet et al. (1994); ..... Castets, A., Duvert, G., Durtey, A., Bally, J., Langer, W. D., Wilson, R. W. 1990, Astron. ... Spitzer Jr., 1978, Physical Processes in the Interstellar Matter (John Wiley).

VizieR Online Data Catalog: Identifications of Sonneberg variables (Kinnunen+, 1999-2000)

Science.gov (United States)

Kinnunen, T.; Skiff, B. A.

2002-09-01

The list below is a continuation of a series providing accurate positions and identifications for variables appearing on the MVS charts (Hoffmeister, 1957, Mitt. Verdander. Sterne, No. 245). The variables here were first described by Hoffmeister (1949, Astron. Abh. Ergaenzungshefte z.d. Astron. Nach., 12, no. 1, A3) in the difficult-to-find ``Ergaenzungshefte'' to the Astronomische Nachrichten, and are the first group from a collection of some 1440 variables from this publication. Details about the identification procedure and table layout are contained in the first report of our series (Kinnunen & Skiff, 2000IBVS.4862....1K). We are grateful to librarians Antoinette Beiser (Lowell) and Brenda Corbin (U. S. Naval Observatory, Washington) for providing a photocopy of the Hoffmeister survey; ``bibliothecaire extraordinaire'' Suzanne Laloe (Obs. Paris-Meudon) advised on how this obscure journal should be cited. (3 data files).

Fulltext PDF

Indian Academy of Sciences (India)

S. Seetha

variety of celestial sources, using satellite-based astron- ... India's first dedicated astronomy satellite –. Astrosat, is ... pose for and study different types of target sources of scientific interest ... lite after launch is provided in the last article. In order ...

Knowledge Architect : A Tool Suite for Managing Software Architecture Knowledge

NARCIS (Netherlands)

Liang, Peng; Jansen, Anton; Avgeriou, Paris

2009-01-01

Management of software architecture knowledge (AK) is vital for improving an organization’s architectural capabilities. To support the architecting process within our industrial partner: Astron, the Dutch radio astronomy institute, we implemented the Knowledge Architect (KA): a tool suite for

Spectroscopic Variability of Supergiant Star HD14134, B3Ia

Indian Academy of Sciences (India)

Y. M. Maharramov

2017-06-19

Jun 19, 2017 ... the hot supergiant HD14134 studied in the present paper has a mass-loss rate of ...... tific program for the priority fields of research of the. National .... emission-line stars in the Large Magellanic Cloud, Astron. Astrophys., 158 ...

Gravitational lensing statistics with extragalactic surveys; 2, Analysis of the Jodrell Bank-VLA Astrometric Survey

NARCIS (Netherlands)

Helbig, P.; Marlow, D. R.; Quast, R.; Wilkinson, P. N.; Browne, I. W. A.; Koopmans, L. V. E.

1999-01-01

Published in: Astron. Astrophys. Suppl. Ser. 136 (1999) no. 2, pp.297-305 citations recorded in [Science Citation Index] Abstract: We present constraints on the cosmological constant $lambda_{0}$ from gravitational lensing statistics of the Jodrell Bank-VLA Astrometric Survey (JVAS). Although this

Erratum: Erratum to: Realistic interpretation of quantum mechanics and encounter-delayed-choice experiment

Science.gov (United States)

Long, GuiLu; Qin, Wei; Yang, Zhe; Li, Jun-Lin

2018-05-01

In our article [1] we made a mistake in citing ref. [32], which is the same as ref. [28]. We now replace ref. [32] with the correct reference "L. Hao, D. Liu, and G. L. Long, Sci. China Phys. Mech. Astron. 53, 1765 (2010)" [2].

Field #3 of the Palomar-Groningen Survey; 1, Variable stars at the edge of the Sagittarius dwarf galaxy

NARCIS (Netherlands)

Schultheis, M.

1996-01-01

Submitted to: Astron. Astrophys. Abstract: A catalogue is presented with variable (RR Lyrae, semiregular and Mira) stars located inside field #3 of the Palomar-Groningen Survey, at the outer edge of the Sagittarius dwarf galaxy. One of the semiregular variables is a carbon star, comparable with

Mergers between elliptical galaxies and the thickening of the Fundamental Plane

NARCIS (Netherlands)

González-Garciá, A. C.; Albada, T. S. van

2003-01-01

Published in: Mon. Not. R. Astron. Soc. 342 (2003) L36 citations recorded in [Science Citation Index] Abstract: We have carried out computer simulations to study the effect of merging on the fundamental plane (FP) relation. Initially, systems are spherical Jaffe models following a simple scaling

LOFAR - low frequency array

NARCIS (Netherlands)

Bentum, Marinus Jan; Gunst, André

Nog een paar maanden en dan wordt de grootste radiotelescoop ter wereld officieel geopend: LOFAR, de ‘Low Frequency Arraÿ'.LOFAR is een nieuwe radiotelescoop die in Nederland gebouwd wordt door ASTRON, de Stichting Astronomisch Onderzoek in Nederland. Met LOFAR heeft Nederland er straks een uniek

The LOFAR Pulsar Data Pipeline

NARCIS (Netherlands)

Alexov, A.; Hessels, J.; Mol, J.D.; Stappers, B.; van Leeuwen, J.

2010-01-01

The LOw Frequency ARray (LOFAR) for radio astronomy is being built in the Netherlands by ASTRON, with extensions throughout Europe. LOFAR operates at radio frequencies below 250 MHz. The project is an interferometric array of radio antennas grouped into stations that are distributed over an area of

A ring galaxy at z = 1 lensed by the cluster Abell 370

NARCIS (Netherlands)

Soucail, G.; Kneib, J. P.; Bézecourt, J.; Metcalfe, L.; Altieri, B.; Borgne, J. F. le

1999-01-01

Published in: Astron. Astrophys. 343 (1999) L70 citations recorded in [Science Citation Index] Abstract: We present a study of a very peculiar object found in the field of the cluster-lens Abell 370. This object displays, in HST imaging, a spectacular morphology comparable to nearby ring-galaxies.

Evaluation of Cardiovascular Risk Scores Applied to NASA's Astronant Corps

Science.gov (United States)

Jain, I.; Charvat, J. M.; VanBaalen, M.; Lee, L.; Wear, M. L.

2014-01-01

In an effort to improve cardiovascular disease (CVD) risk prediction, this analysis evaluates and compares the applicability of multiple CVD risk scores to the NASA Astronaut Corps which is extremely healthy at selection.

IAA : Información y actualidad astronómica (29)

OpenAIRE

Toro, José Carlos del; López de Lacalle, Silbia; Claret dos Santos, Antonio; García, Emilio José; Alberdi, Antxón; Garrido, Rafael; Gorosabel, Javier; Márquez, Isabel; Jaramillo, José Luis; Santos Sanz, Pablo; Osorio, Mayra

2009-01-01

Sumario : Sunrise, una aventura polar.-- Nuestra tormentosa estrella.-- ¿Son válidos los modelos de atmósferas estelares?.-- ¿Viajaremos más rápido que la luz?.-- HISTORIAS DE ASTRONOMÍA. Últimas tardes con Hipatia.-- DECONSTRUCCIÓN Y otros ENSAYOS. Edwin Hubble.-- EL “MOBY DICK” DE... Antxon Alberdi (IAA-CSIC).-- ACTUALIDAD.-- Betelgeuse en ebullición.-- ¿Qué supone el hallazgo de glicina en el cometa 81P/Wild?.-- ¿Existe el cinturón de Gould?.-- Cosmología d...

Proceedings of Colloquium 110 of the International Astronomical Union on Library and Information Services in Astronomy Held in Washington, DC on 26 July- 1 August 1988

Science.gov (United States)

1989-01-01

executive overview, IBM System Service, Stuttgart. 2. Doyen, P., 1987. Analyse d’opportunite et aspects fonctionnels d’une gestion integree par un systeme...Inst. di Astron. Tucson, AZ 85726-6732 Campus do Vale Citta. Universitaria 90049 Porto Alegre RS Viale A. Doris Mo. Vagiawari Alladi BRAZIL 1-95125

Astronomical Observations by Speckle Interferometry.

Science.gov (United States)

1986-06-12

commonly -been noted [Heintz (101)] that it was Karl *, Schwarzchild who iui 1895 [ Schwarzschild (190)] made the first measure- ments of binary stars...J. Lett 163. Michelson, A A, Pease. F. G. 1921. Ap. 280: L23 J. 53: 249 190. Schwarzschild . K. 1896. Astron. Nadir. 164. Morgan. B. L., lieddoes. 1

Statistical Methods in Physical Oceanography: Proceedings of ’Aha Huliko’a Hawaiian Winter Workshop Held in Manoa, Hawaii on January 12-15, 1993

Science.gov (United States)

1993-11-01

theories of turbulence and the e expansion. Phys. Fluids, 30, 2021-2029. FORSTER, D., NELSON, D.R., AND STEPHEN , M.J., 1977: Large distance and long-time...Branover and Y. Unger, Vol. 149, Progress in Astron. and Aeron., AIAA, pp. 159-164. STARR, V.P., 1968: Physics of Negative Viscosity Phenomena. Mc- Graw Hill

On Modeling the Kelvin–Helmholtz Instability in Solar Atmosphere I ...

Indian Academy of Sciences (India)

explained in terms of unstable m = −3 MHD mode. We also describe ... (2009). In other words, ..... Thus, we are convinced to accept the expanded definition of the CME suggested in. Vourlidas et al. .... The authors focused on the stability and oscillatory ...... Cavus, H., Kazkapan, D. 2013, New Astron., 25, 85–94. Chandra, R.

Strong lensing probability in TeVeS (tensor-vector-scalar) theory

Science.gov (United States)

Chen, Da-Ming

2008-01-01

We recalculate the strong lensing probability as a function of the image separation in TeVeS (tensor-vector-scalar) cosmology, which is a relativistic version of MOND (MOdified Newtonian Dynamics). The lens is modeled by the Hernquist profile. We assume an open cosmology with Ωb = 0.04 and ΩΛ = 0.5 and three different kinds of interpolating functions. Two different galaxy stellar mass functions (GSMF) are adopted: PHJ (Panter, Heavens and Jimenez 2004 Mon. Not. R. Astron. Soc. 355 764) determined from SDSS data release 1 and Fontana (Fontana et al 2006 Astron. Astrophys. 459 745) from GOODS-MUSIC catalog. We compare our results with both the predicted probabilities for lenses from singular isothermal sphere galaxy halos in LCDM (Lambda cold dark matter) with a Schechter-fit velocity function, and the observational results for the well defined combined sample of the Cosmic Lens All-Sky Survey (CLASS) and Jodrell Bank/Very Large Array Astrometric Survey (JVAS). It turns out that the interpolating function μ(x) = x/(1+x) combined with Fontana GSMF matches the results from CLASS/JVAS quite well.

Journal of Astrophysics and Astronomy | Indian Academy of Sciences

Indian Academy of Sciences (India)

2016-01-27

Jan 27, 2016 ... Paul D. Nuñez1 Marek Nowakowski2. Department of Physics & Astronomy, University of Utah, 115 S 1400 E, Salt Lake City, UT 84112 and Observatorio Astronómico, Universidad Sergio Arboleda, Cll. 74 No. 14–14, Bogotá, Colombia. Departamento de Física, Universidad de los Andes, Cra. 1E No.

The Large Scale Magnetic Field and Sunspot Cycles

Indian Academy of Sciences (India)

tribpo

Financial support for this work comes from the Russian Fund Basic Research, Grant. 99 02 16200 and 00 02 16355, INTAS 98 1088 and NRA 98 OSS 08. References. Makarov, V. I., Tlatov, A. G. 1999, in Proceedings of the 9th Meeting on Solar Physics (Italy),. 125. Makarov, V. I., Tlatov, A. G. 2000, Astron. Rep., (in press).

Alfabetización en Astronomía de docentes de Educación Primaria y de Educación Secundaria en La Plata

Science.gov (United States)

De Biasi, M. S.; Orellana, R. B.

2014-10-01

La educación de este siglo tiene como uno de sus retos alcanzar la alfabetización cientfica de todos los ciudadanos para que comprendan y tomen decisiones sobre el mundo natural y sus cambios originados por la actividad humana utilizando el conocimiento científico. En esta misión los docentes de los niveles obligatorios de enseñanza juegan un papel clave por su rol de agentes multiplicadores del conocimiento. Se requiere, entonces de una adecuada alfabetización en ciencias de los docentes o, como mínimo, que dominen los temas científicos a enseñar. En el campo de la Astronomía, numerosas investigaciones han señalado que maestros de primaria y estudiantes de profesorados poseen una escasa formación en estos temas (Camino 1995 y 1999, Gangui 2010), que frecuentemente presentan a los alumnos concepciones alternativas o no científicas de los fenómenos astronómicos cotidianos (Kriner 2004, Vega Navarro 2007, Gangui et al 2010); a lo que se suma la presentación confusa o errónea de algunos temas astronómicos en los textos escolares (Kriner 2004). Desde 2011, la Facultad de Ciencias Astronómicas y Geofísicas, UNLP, ofrece un curso de capacitación destinado a fortalecer y actualizar los contenidos académicos y didácticos de los docentes del distrito La Plata utilizando diversas estrategias didácticas. Los contenidos comprenden los temas astronómicos de los diseños curriculares vigentes. La evaluación diagnóstica de los conocimientos previos de los docentes cursantes sobre los contenidos de mayor presencia en los diseños curriculares mostró resultados similares a las investigaciones arriba mencionadas. Referente a los movimientos de la Tierra, en promedio, el 54% poseía conceptos erróneos y el 16% no los sabía; con referencia a la Luna el 56% poseía conceptos erróneos y un 4% no los sabía. Los resultados del curso mostraron que el 95% de los docentes revirtió sus conceptos previos erróneos, que adquirió criterios para la búsqueda de

Long-term Periodicity Analysis of Polarization Variation for Radio ...

Indian Academy of Sciences (India)

Kochanev, P. Yu., Gabuzda, D. C. 1998, In: Radio Emission From Galactic and Extragalactic. Compact Sources (eds) Zensus, J. A., Taylor, G. B., Wrobel, J. M., San Francisco: ASP, p. 273. Lomb, N. R. 1976, ApS&S, 39, 447. Mead, A. R. G., Ballard, K. R., Brand, P. W. J. L. et al. 1990, Astron. Astrophys. Suppl. Ser.,. 83, 183.

Instalación de un nuevo telescopio robótico en la estación de altura Cesco

Science.gov (United States)

Schwartz, M. A. Perna, P.; Mauas, P.; Veltri, A.; Hereñú, H.

In this paper we present the works done for the installation of a 16 inches reflector telescope at the Carlos U. Cesco high altitude station of the Observatorio Astronómico Félix Aguilar; San Juan; Argentina. We describe the implementation of the software and hardware needed for the remote control of the instrument and its future robotization. FULL TEXT IN SPANISH

Establishing the Empirical Relationship Between Non-Science Majoring Undergraduate Learners' Spatial Thinking Skills and Their Conceptual Astronomy Knowledge. (Spanish Title: Estableciendo Una Relación Empírica Entre el Razonamiento Espacial de los Estudiantes de Graduación de Carreras no Científicas y su Conocimento Conceptual de la Astronomía.) Estabelecendo Uma Relação Empírica Entre o RacioCínio Espacial dos Estudantes de Graduação EM Carreiras Não Científicas e Seu Conhecimento Conceitual da Astronomia

Science.gov (United States)

Heyer, Inge; Slater, Stephanie J.; Slater, Timothy F.

2013-12-01

The astronomy education community has tacitly assumed that learning astronomy is a conceptual domain resting upon spatial thinking skills. As a first step to formally identify an empirical relationship, undergraduate students in a non-major introductory astronomy survey class at a mediumsized, Ph.D. granting, mid-western US university were given pre- and post-astronomy conceptual diagnostics and spatial reasoning diagnostics, Instruments used were the "Test Of Astronomy Standards" and "What Do You Know?" Using only fully matched data for analysis, our sample consisted of 86 undergraduate non-science majors. Students' normalized gains for astronomy surveys were low at .26 and .13 respectively. Students' spatial thinking was measured using an instrument designed specifically for this study. Correlations between the astronomy instruments' pre- to post-course gain scores and the spatial assessment instrument show moderate to strong relationships suggesting the relationship between spatial reasoning and astronomy ability can explain about 25% of the variation in student achievement. La comunidad de educación en astronomía ha supuesto de forma tácita que el aprendizaje de la astronomía consiste en un dominio conceptual fundamentado en el razonamiento espacial. Como un primer paso para identificar formalmente una relación empírica entre estas dos cosas, utilizamos como muestra los estudantes de graduación de carreras no científicas de un curso experimental en una universidad norteamericana del medioeste de porte mediano con programa de Doctorado em curso, en el cual estos estudiantes se sometieron a un diagnóstico de razonamiento espacial y conceptos astronómicos antes e después del mismo. Las herramientas utilizadas fueron el Test Of Astronomy Standards (TOAST) y el cuestionario What do you know? Utilizando solo los datos completamente consistentes para este análisis, nuestra muestra consistió en 86 estudantes de graduación. Las mejoras, depués de

Analysis of atmospheric pressure and temperature effects on cosmic ray measurements

Science.gov (United States)

de MendonçA, R. R. S.; Raulin, J.-P.; Echer, E.; Makhmutov, V. S.; Fernandez, G.

2013-04-01

In this paper, we analyze atmospheric pressure and temperature effects on the records of the cosmic ray detector CARPET. This detector has monitored secondary cosmic ray intensity since 2006 at Complejo Astronómico El Leoncito (San Juan, Argentina, 31°S, 69°W, 2550 m over sea level) where the geomagnetic rigidity cutoff, Rc, is ~9.8 GV. From the correlation between atmospheric pressure deviations and relative cosmic ray variations, we obtain a barometric coefficient of -0.44 ± 0.01 %/hPa. Once the data are corrected for atmospheric pressure, they are used to analyze temperature effects using four methods. Three methods are based on the surface temperature and the temperature at the altitude of maximum production of secondary cosmic rays. The fourth method, the integral method, takes into account the temperature height profile between 14 and 111 km above Complejo Astronómico El Leoncito. The results obtained from these four methods are compared on different time scales from seasonal time variations to scales related to the solar activity cycle. Our conclusion is that the integral method leads to better results to remove the temperature effect of the cosmic ray intensity observed at ground level.

Astronomia nos anos iniciais do Ensino Fundamental: uma parceria entre universidade e escola

Directory of Open Access Journals (Sweden)

Alexandre Barai

2016-12-01

Full Text Available http://dx.doi.org/10.5007/2175-7941.2016v33n3p1009   Este trabalho descreve a experiência de interação e parceria entre uma escola e um dos campi da Universidade Federal de São Carlos (UFSCar, ambos localizados em Araras-SP, com o objetivo de ensinar e divulgar conhecimentos de astronomia e astronáutica entre alunos dos cinco primeiros anos do Ensino Fundamental. Esta iniciativa utilizou-se da Olimpíada Brasileira de Astronomia e Astronáutica como evento motivador para a exploração do tema. As ações foram divididas em duas frentes: um curso de aperfeiçoamento para professores da escola realizado por professores da universidade e palestras ministradas para os alunos por estudantes da UFSCar sob orientação dos professores da universidade e dos coordenadores da escola. Dos resultados observados, constatamos a importância do estreitamento da distância escola-universidade, promovendo ações de aprendizagem para ambos e ajudando a elevar o nível de ensino desde o infantil ao superior.

Secondary resonances and the boundary of effective stability of Trojan motions

Science.gov (United States)

Páez, Rocío Isabel; Efthymiopoulos, Christos

2018-02-01

One of the most interesting features in the libration domain of co-orbital motions is the existence of secondary resonances. For some combinations of physical parameters, these resonances occupy a large fraction of the domain of stability and rule the dynamics within the stable tadpole region. In this work, we present an application of a recently introduced `basic Hamiltonian model' H_b for Trojan dynamics (Páez and Efthymiopoulos in Celest Mech Dyn Astron 121(2):139, 2015; Páez et al. in Celest Mech Dyn Astron 126:519, 2016): we show that the inner border of the secondary resonance of lowermost order, as defined by H_b, provides a good estimation of the region in phase space for which the orbits remain regular regardless of the orbital parameters of the system. The computation of this boundary is straightforward by combining a resonant normal form calculation in conjunction with an `asymmetric expansion' of the Hamiltonian around the libration points, which speeds up convergence. Applications to the determination of the effective stability domain for exoplanetary Trojans (planet-sized objects or asteroids) which may accompany giant exoplanets are discussed.

Strong lensing probability in TeVeS (tensor–vector–scalar) theory

International Nuclear Information System (INIS)

Chen Daming

2008-01-01

We recalculate the strong lensing probability as a function of the image separation in TeVeS (tensor–vector–scalar) cosmology, which is a relativistic version of MOND (MOdified Newtonian Dynamics). The lens is modeled by the Hernquist profile. We assume an open cosmology with Ω b = 0.04 and Ω Λ = 0.5 and three different kinds of interpolating functions. Two different galaxy stellar mass functions (GSMF) are adopted: PHJ (Panter, Heavens and Jimenez 2004 Mon. Not. R. Astron. Soc. 355 764) determined from SDSS data release 1 and Fontana (Fontana et al 2006 Astron. Astrophys. 459 745) from GOODS-MUSIC catalog. We compare our results with both the predicted probabilities for lenses from singular isothermal sphere galaxy halos in LCDM (Lambda cold dark matter) with a Schechter-fit velocity function, and the observational results for the well defined combined sample of the Cosmic Lens All-Sky Survey (CLASS) and Jodrell Bank/Very Large Array Astrometric Survey (JVAS). It turns out that the interpolating function μ(x) = x/(1+x) combined with Fontana GSMF matches the results from CLASS/JVAS quite well

The Double–Double Radio Galaxy 3C293 S. A. Joshi1,∗ , S. Nandi2 ...

Indian Academy of Sciences (India)

prominent hot-spot in the north-western lobe as well as the age of the inner double structure suggests that the interruption of jet activity is <. ∼0.1 Myr. References. Beswick R.J., Peck A.B., Taylor G.B., Giovannini G. 2004, Mon. Not. R. Astron. Soc., 352, 49. Joshi S.A., Nandi S., Saikia D.J., Ishwara-Chandra C.H., Konar C.

Los cometas de Atawallpa: acerca del papel de las profecías en la política del Estado Inka

Directory of Open Access Journals (Sweden)

Mariusz Ziólkowski

1988-12-01

Full Text Available En este artículo quisiera detenerme sólo sobre el eventual impacto que pudieron haber tenido el calendario estatal inca y las profecías basadas  en la interpretación de los fenómenos astronómicos extraordinarios, en la actitud que tomaron los dirigentes del Imperio, y especialmente Atawallpa, frente a los españoles.

Erratum: Spiral structure in the accretion disc of the binary IP Pegasi

Science.gov (United States)

Steeghs, D.; Harlaftis, E. T.; Horne, Keith

1998-05-01

The paper `Spiral structure in the accretion disc of the binary IP Pegasi' was published in Mon. Not. R. Astron. Soc. 290, L28-L32 (1997). Figs 1 and 2 of the paper (grey-scale images) did not reproduce well, and are reprinted here (Fig. 1 overleaf). Colour versions of the images are available on the World Wide Web:http://www-star.st-and.ac.uk/^~ds10/spirals.html

Collateral Damage to Satellites from an EMP Attack

Science.gov (United States)

2010-08-01

field into regions of weak magnetic field [Stern. 1989, and references therein]. Birkeland’s work captured the interest of auroral researcher Stormer ...dipole magnetic field [ Stormer , 1907]. Although mathematically elegant, Stormer theory did not prove the existence of radiation belts; it set the stage...Based on work by Stormer , Alfven, and others, and on his experience with the Astron thermonuclear device, N. Christofolis in October 1957 suggested

Effects of Long Duration Spaceflight on Venous and Arterial Compliance in Astronants

Science.gov (United States)

Platts, Steven; Ribeiro, L. Christine

2014-01-01

1. Project Overview Visual impairment and intracranial pressure (VIIP) is a spaceflight-associated medical condition affecting at least a third of American astronauts who have flown International Space Station (ISS) missions. VIIP is defined primarily by visual acuity deficits and anatomical changes to eye structures. In some astronauts, eye-related changes do not revert back to the preflight state upon return to Earth. Our team will study some of the possible causes for this syndrome. This will be achieved by reviewing previous astronaut data for factors that may predispose astronauts to higher rates of developing this syndrome or greater severity of symptoms. Additionally, we will conduct 3 separate experiments that will characterize vessels in the head and neck and measure the effects of the experimental conditions on ocular structures and function. 2. Technical Summary The primary objective of this study is to determine whether vascular compliance is altered by spaceflight and whether such adaptations are related to the incidence of the VIIP. In particular, we will measure ocular parameters and vascular compliance in vessels of the head and neck in astronauts who have no spaceflight experience (Ground), in astronauts before, during, and after spaceflight (Flight), and in bed rest subjects with conditions similar to spaceflight (Bed Rest). Additionally, we will analyze astronaut data from the Lifetime Surveillance of Astronaut Health (LSAH) archives to determine which factors might be predictive of the development of VIIP (Data Mining). The project will be conducted in four separate, but related parts. Hypothesis The central hypothesis of this proposal is that exposure to the spaceflight environment aboard the ISS may lead to development of the VIIP syndrome (increased intracranial pressure and impaired visual acuity) and that this may be related to alterations in venous and/or arterial compliance in the head and neck. Specific Aims 1. To determine whether noninvasive measures of venous and arterial compliance are altered by long-duration spaceflight exposure in ISS astronauts and whether these changes are related to the development of the VIIP syndrome. (Flight) 2. To determine whether previous spaceflight experience predispose astronauts to lower venous compliance and/or the development of the VIIP syndrome. (Ground + Flight) 3. To use a 14-day, 6deg head-down-tilt bed rest as a model of spaceflight, to evaluate the effect of aging on vascular compliance using a subject population similar to younger (25-35 yr) and older (45-55 yr) astronaut cohorts. (Bed Rest) 4. To determine what factors contribute to lower venous compliance and/or the development of the VIIP syndrome in astronauts. (Data Mining) 3. Earth Applications This research may inform the mechanisms that regulate blood/fluid flow in and out of the brain in the head and neck. This information may help with understanding of the mechanisms behind idiopathic intracranial hypertension. 4. Link to NASA Taskbook Entry Not Yet Available

Study of the Local Horizon. (Spanish Title: Estudio del Horizonte Local.) Estudo do Horizonte Local

Science.gov (United States)

Ros, Rosa M.

2009-12-01

The study of the horizon is fundamental to easy the first observations of the students at any education center. A simple model, to be developed in each center, allows to easy the study and comprehension of the rudiments of astronomy. The constructed model is presented in turn as a simple equatorial clock, other models (horizontal and vertical) may be constructed starting from it. El estudio del horizonte es fundamental para poder facilitar las primeras observaciones de los alumnos en un centro educativo. Un simple modelo, que debe realizarse para cada centro, nos permite facilitar el estudio y la comprensión de los primeros rudimentos astronómicos. El modelo construido se presenta a su vez como un sencillo modelo de reloj ecuatorial y a partir de él se pueden construir otros modelos (horizontal y vertical). O estudo do horizonte é fundamental para facilitar as primeiras observações dos alunos num centro educativo. Um modelo simples, que deve ser feito para cada centro, permite facilitar o estudo e a compreensão dos primeiros rudimentos astronômicos. O modelo construído apresenta-se, por sua vez, como um modelo simples de relógio equatorial e a partir dele pode-se construir outros modelos (horizontal e vertical)

The Universe Observation Center: an educational center devoted to Astronomy in Catalonia

Science.gov (United States)

Fernández, D.

The Universe Observation Center (in Catalan language, Centre d'Observació de l'Univers, COU) is located in close proximity to the Montsec Astronomical Observatory (Observatori Astronòmic del Montsec, OAM), in eastern Catalonia (Spain). Both centers comprise the Montsec Astronomical Park (Parc Astronòmic Montsec, PAM), managed by the Consorci del Montsec. Montsec Mountain remains the finest location for astronomical observation in Catalonia, as demonstrated by a site-testing campaign conducted by the Astronomy and Meteorology Department of the University of Barcelona. The COU consists of a Central Building (including a permanent exhibition and three classrooms possessing broadband Internet access), the Telescope Park (two astronomical domes equipped with medium-size telescopes, a coelostat for solar observation, and a portable telescope park), the Eye of Montsec (a digital planetarium and, at the same time, an extremely innovative platform for sky observation) and the Garden of the Universe (a tour of the land surrounding the COU, visiting several areas within it). The COU will offer to the Spanish academic community a host of fascinating and unique activities in the fields of astronomy and geology. The Center is open not only to students (from primary school through university), but also to amateur astronomers, people interested in science and the general public.

TIPTOPbase: the Iron Project and the Opacity Project Atomic Database

Science.gov (United States)

Mendoza, Claudio; Nahar, Sultana; Pradhan, Anil; Seaton, Micheal; Zeippen, Claude

2001-05-01

The Opacity Project, the IRON Project, and the RmaX Network (The Opacity Project Team, Vol.1,2), IOPP, Bristol (1995,1996); Hummer et al., Astron. Astrophys. 279, 298 (1993) are international computational efforts concerned with the production of high quality atomic data for astrophysical applications. Research groups from Canada, France, Germany, UK, USA and Venezuela are involved. Extensive data sets containing accurate energy levels, f-values, A-values, photoionisation cross sections, collision strengths, recombination rates, and opacitites have been computed for cosmically abundant elements using state-of-the-art atomic physics codes. Their volume, completeness and overall accuracy are presently unmatched in the field of laboratory astrophysics. Some of the data sets have been available since 1993 from a public on-line database service referred to as TOPbase (Cunto et al Astron. Astrophys. 275), L5 (1993), ( http://cdsweb.u-strasbg.fr/OP.html at CDS France, and http://heasarc.gsfc.nasa.gov/topbase, at NSAS USA). We are currently involved in a major effort to scale the existing database services to develop a robust platform for the high-profile dissemination of atomic data to the scientific community within the next 12 months. (Partial support from the NSF and NASA is acknowledged.)

Ajuste de parámetros libres en teorías de campos camaleones a partir de espectros de nubes moleculares galácticas y experimentos terrestres

Science.gov (United States)

Teppa Pannia, F. A.; Landau, S. J.

Resultados recientes, basados en el análisis de espectros moleculares de nubes galácticas a través del método del amoníaco, han arrojado nuevos límites sobre la variación del parámetro adimensional μ=m_e /m_p. Los resultados indican Δ μ/μ = (μ_{obs}-μ_{lab})/μ_{lab}= (2.2± 0.4_{est} ±0.3_{sist}) times 10 ^{-8}, en acuerdo con una variación no nula de dicha cantidad (Levshakov et al. 2010). En este trabajo, motivado por los datos astronómicos, estudiamos la solución lineal del modelo teórico fenomenológico de campo escalar camaleón, presentado por Mota y Shaw (2007), que predice variaciones en μ. Con el fin de cotejar estas predicciones con los resultados observacionales, utilizamos datos de experimentos terrestres que testean violaciones al Principio de Equivalencia para analizar el valor de los parámetros libres presentes en el modelo. El trabajo realizado muestra que la solución estudiada no se puede ajustar a los datos experimentales, sugiriendo que el modelo lineal debe ser descartado para explicar las observaciones astronómicas. FULL TEXT IN SPANISH

Optical emissions from an ionized channel produced by an electron beam

International Nuclear Information System (INIS)

Fessenden, T.J.

1977-01-01

Quantitative measurements of the visible light generated by the Astron beam (5 MeV, 400 A) in passing through 500 torr air and nitrogen are reported. Experiments show that in the presence of the beam, the light is from .01 to 0.1 percent sun's brightness. After the beam, the light decays extremely rapidly. The size and position of the beam in the gas can be determined from observations of the channel light

Ondas gravitacionales de choque

OpenAIRE

Ranea Sandoval, Ignacio Francisco

2010-01-01

En este trabajo monográfico se presenta un breve resumen relacionado con las ondas gravitacionales y con la teoría general de la relatividad. Realizado esto se presenta una adaptación de trabajos científicos asociados con un fenómeno conocido como ondas gravitacionales de choque. Trabajo final de Introducción a la Astrofísica de Agujeros Negros. Facultad de Ciencias Astronómicas y Geofísicas

100 anys després, el desastre del Titànic troba nous culpables

OpenAIRE

Marco Soler, Enric

2012-01-01

100 anys després de l'enfonsament del Titànic, l'article revisa, des d'un punt de vista astronòmic, la influència de l'alineació lunisolar de gener de 1912 sobre el desastre marítim. 100 years after the sinking of the Titanic, the article reviews, from an astronomical point of view, the influence of the lunisolar alignment of January 1912 on the maritime disaster.

Acoustic Metadata Management and Transparent Access to Networked Oceanographic Data Sets

Science.gov (United States)

2015-09-30

Transparent Access to Networked Oceanographic Data Sets Marie A. Roch Dept. of Computer Science San Diego State University 5500 Campanile Drive San...specific technologies for processing Excel spreadsheets and Access databases. The architecture (Figure 4) is based on a client-server model...Keesey, M. S., Lieske, J. H., Ostro, S. J., Standish, E. M., and Wimberly, R. N. (1996). "JPL’s On-Line Solar System Data Service," B. Am. Astron

Double C-NOT attack and counterattack on `Three-step semi-quantum secure direct communication protocol'

Science.gov (United States)

Gu, Jun; Lin, Po-hua; Hwang, Tzonelih

2018-07-01

Recently, Zou and Qiu (Sci China Phys Mech Astron 57:1696-1702, 2014) proposed a three-step semi-quantum secure direct communication protocol allowing a classical participant who does not have a quantum register to securely send his/her secret message to a quantum participant. However, this study points out that an eavesdropper can use the double C-NOT attack to obtain the secret message. To solve this problem, a modification is proposed.

Essays on Eclipses, Transits and Occultations as Teaching Tools in the Introductory Astronomy College Course. (Spanish Title: Ensayos sobre Eclipses, Tránsitos y Ocultaciones Como Herramientas de Enseñanza en el Curso Universitario Introductorio a la Astronomía.) Ensaios sobre Eclipses, Trânsitos e Ocultações Como Ferramentas de Ensino em um Curso Universitário Introdutório de Astromomia

Science.gov (United States)

Dcruz, Noella L.

2014-07-01

We occasionally include projects in our learner-centered introductory astronomy college course to enable non-science major students explore some astronomical concepts in more detail than otherwise. Such projects also highlight ongoing or upcoming astronomical events. We hope that students will feel more interested in astronomy through projects tied to astronomical events. In Spring 2012, we offered short essays focused on eclipses, transits and occultations to promote the rare transit of Venus that occurred on June 5th, 2012. We asked students to write two short essays from three that were offered. The essays contained descriptive and conceptual parts. They were meant to serve as teaching tools. 62% of 106 essays from 55 students earned A, B or C grades. 21% of 47 feedback survey respondents felt the essays increased their interest in astronomy. 49% of respondents felt that the essays were not educationally beneficial and should not be offered again. The most common written response to our survey indicated that students need more guidance and better preparation in writing successful essays. Since students found the conceptual parts of the essays difficult, in the future we will provide relevant activities prior to essay deadlines to help students create successful essays. Ocasionalmente, incluimos proyectos en nuestro curso de introducción a la astronomía universitario centrado en el alumno para permitir que los estudiantes de carreras no científicas exploren algunos conceptos astronómicos en más detalle que lo habitual. Estos proyectos también ponen en relevancia eventos astronómicos en curso o futuros. Esperamos que los estudiantes se sientan más interesados en la astronomía a través de proyectos vinculados a eventos astronómicos. En el período de primavera de 2012 (EUA), propusimos breves ensayos centrados en los eclipses, tránsitos y ocultaciones para promover el raro tránsito de Venus que se produjo el 5 de junio de 2012. Le pedimos a los

High energy neutrinos from astrophysical accelerators of cosmic ray nuclei

Science.gov (United States)

Anchordoqui, Luis A.; Hooper, Dan; Sarkar, Subir; Taylor, Andrew M.

2008-02-01

Ongoing experimental efforts to detect cosmic sources of high energy neutrinos are guided by the expectation that astrophysical accelerators of cosmic ray protons would also generate neutrinos through interactions with ambient matter and/or photons. However, there will be a reduction in the predicted neutrino flux if cosmic ray sources accelerate not only protons but also significant numbers of heavier nuclei, as is indicated by recent air shower data. We consider plausible extragalactic sources such as active galactic nuclei, gamma ray bursts and starburst galaxies and demand consistency with the observed cosmic ray composition and energy spectrum at Earth after allowing for propagation through intergalactic radiation fields. This allows us to calculate the expected neutrino fluxes from the sources, normalized to the observed cosmic ray spectrum. We find that the likely signals are still within reach of next generation neutrino telescopes such as IceCube.PACS95.85.Ry98.70.Rz98.54.Cm98.54.EpReferencesFor a review, see:F.HalzenD.HooperRep. Prog. Phys.6520021025A.AchterbergIceCube CollaborationPhys. Rev. Lett.972006221101A.AchterbergIceCube CollaborationAstropart. Phys.262006282arXiv:astro-ph/0611063arXiv:astro-ph/0702265V.NiessANTARES CollaborationAIP Conf. Proc.8672006217I.KravchenkoPhys. Rev. D732006082002S.W.BarwickANITA CollaborationPhys. Rev. Lett.962006171101V.Van ElewyckPierre Auger CollaborationAIP Conf. Proc.8092006187For a survey of possible sources and event rates in km3 detectors see e.g.,W.BednarekG.F.BurgioT.MontaruliNew Astron. Rev.4920051M.D.KistlerJ.F.BeacomPhys. Rev. D742006063007A. Kappes, J. Hinton, C. Stegmann, F.A. Aharonian, arXiv:astro-ph/0607286.A.LevinsonE.WaxmanPhys. Rev. Lett.872001171101C.DistefanoD.GuettaE.WaxmanA.LevinsonAstrophys. J.5752002378F.A.AharonianL.A.AnchordoquiD.KhangulyanT.MontaruliJ. Phys. Conf. Ser.392006408J.Alvarez-MunizF.HalzenAstrophys. J.5762002L33F.VissaniAstropart. Phys.262006310F

Developing an Optical Lunar Occultation Measurement Reduction System for Observations at Kaau Observatory

Science.gov (United States)

Malawi, Abdulrahman A.

2013-06-01

We present here a detailed explanation of the reduction method that we use to determine the angular diameters of the stars occulted by the dark limb of the moon. This is a main part of the lunar occultation observation program running at King Abdul Aziz University observatory since late 1993. The process is based on the least square model fitting method of analyzing occultation data, first introduced by Nather et al. (Astron. J. 75:963, 1970).

The properties of radio ellipticals

International Nuclear Information System (INIS)

Sparks, W.B.; Disney, M.J.; Rodgers, A.W.

1984-01-01

Optical and additional radio data are presented for the bright galaxies of the Disney and Wall survey (1977 Mon. Not. R. Astron. Soc. 179, 235). These data form the basis of a statistical comparison of the properties of radio elliptical galaxies to radio-quiet ellipticals. The correlations may be explained by the depth of the gravitational potential well in which the galaxy resides governing the circumstances under which an elliptical galaxy rids itself of internally produced gas. (author)

Energy Levels, wavelengths and hyperfine structure measurements of Sc II

Science.gov (United States)

Hala, Fnu; Nave, Gillian

2018-01-01

Lines of singly ionized Scandium (Sc II) along with other Iron group elements have been observed [1] in the region surrounding the massive star Eta Carinae [2,3] called the strontium filament (SrF). The last extensive analysis of Sc II was the four-decade old work of Johansson & Litzen [4], using low-resolution grating spectroscopy. To update and extend the Sc II spectra, we have made observation of Sc/Ar, Sc/Ne and Sc/Ge/Ar hollow cathode emission spectrum on the NIST high resolution FT700 UV/Vis and 2 m UV/Vis/IR Fourier transform spectrometers (FTS). More than 850 Sc II lines have been measured in the wavelength range of 187 nm to 3.2 μm. connecting a total of 152 energy levels. The present work also focuses to resolve hyperfine structure (HFS) in Sc II lines. We aim to obtain accurate transition wavelengths, improved energy levels and HFS constants of Sc II. The latest results from work in progress will be presented.Reference[1] Hartman H, Gull T, Johansson S and Smith N 2004 Astron. Astrophys. 419 215[2] Smith N, Morse J A and Gull T R 2004 Astrophys. J. 605 405[3] Davidson K and Humphreys R M 1997 Annu. Rev. Astron. Astrophys. 35[4] Johansson S and Litzén U 1980 Phys. Scr. 22 49

Understanding the Effects of Long-duration Space Flight on Astronant Functional Task Performance

Science.gov (United States)

Bloomberg, Jacob J.; Batson, Crystal D.; Buxton, Roxanne E.; Feiveson, Al H.; Kofman, Igor S.; Lee, Stuart M. C.; Miller, Chris A.; Mulavara, Ajitkumar P.; Peters, Brian T.; Phillips, Tiffany;

IERS Conventions (2010)

Science.gov (United States)

2010-01-01

2MASS near-IR catalog (ɛ>) provides accurate positions of over 470 million stars at individual mean epochs (around 2000), however, without proper motions...An overview of other current and future, ground- and space-based densification projects is given at ɜ>. 3http://www.ipac.caltech.edu/ 2mass /releases...and proper motions on the ICRS. Combining USNO-B1.0 and the Two Micron All Sky Survey ( 2MASS ),” Astron. J., 139(6), pp. 2440–2447, doi: 10.1088/0004

Quantitative Measurements of Daytime Near Infrared Sky Brightness at the AEOS 3.6 m Telescope

Science.gov (United States)

2014-09-01

photometric filters. In the case of the 1250 nm filter, the quoted results reflect the brightness that would be seen through a standard 2MASS J filter [9...brightness per unit wavelength through the broader 2MASS filter with 162 nm bandpass. Given the known colors of the star, we estimate this error to be...Megeath, S. T. “Spectral irradiance calibration in the infrared. XIV. The absolute calibration of 2MASS ,” Astron. J., 126, 1090–1096 (2003) [10] Jim

Herramientas libres para modelar software Free tools to model software

Directory of Open Access Journals (Sweden)

Mauro Callejas Cuervo Óscar Yovany Baquero Moreno

2010-11-01

Full Text Available Observación acerca del  software libre y de suimplicación en procesos de desarrollo de  softwarecon herramientas 4G por parte de entidades opersonas sin capitales astronómicos y sin lamentalidad acaparadora de dominar el mercado conproductos costosos que las hagan multimillonarias yque no ofrecen una garantía real, ni la posibilidadsiquiera de conocer el  software por el que se hapagado, y mucho menos de modificarlo si no cumplenuestras expectativas.

2000 NRL Review

Science.gov (United States)

2000-01-01

extensive back files maintained as bound volumes or on microfilm; and a research reports collection of more than one million items stored in paper , micro...thousands of research reports, and NRL publications including press re- leases, journal articles, and conference papers . InfoWeb also links users to another...MHz with the Very Large Array,” Astron. J. 106, 2218-2228 (1993). 2 F.N. Owen, J.A. Eilek, and N.E. Kassim, “The Virgo Cluster and the M 87 Radio Halo

Seguimiento fotométrico de tránsitos exoplanetarios

Science.gov (United States)

Char, F.; Unda-Sanzana, E.; Kipping, D.; Colazo, C.; Núñez, R.; Guzzo, P.; Schneiter, M.; Colque, J. P.

The Unidad de Astronomía of the Universidad de Antofagasta (Chile) has begun a collaboration with the University College London, the Observatorio Astronómico de Córdoba and the Instituto de Astronomía Teórica y Experimental at Universidad Nacional de Córdoba, to enlarge a rich database of exoplanetary transits, with the efforts from both profesional and amateur astronomers. These data will be used to test Transit Timing Variations (TTVs) and help to improve the existing exoplanet databases. FULL TEXT IN SPANISH

The McLean-Watson line strength formula and its implementation

International Nuclear Information System (INIS)

Hey, J D

2009-01-01

We consider the application of the line strength formula recently derived by Watson (2006 J. Phys. B: At. Mol. Opt. Phys. 39 L291) to transitions between states of high principal quantum number in hydrogenic atoms and ions (Rydberg-Rydberg transitions). Apparent difficulties in the implementation of this formula are overcome by the use of recurrence relations derived by the ladder operator technique of Infeld and Hull (1951 Rev. Mod. Phys. 23 21), and set out in an earlier paper by the present author (2006 J. Phys. B: At. Mol. Opt. Phys. 39 2641). The use of the McLean-Watson formula for such cases is illustrated by the determination of the radiative lifetimes for levels with n ∼ 1000 and comparison of present results with approximate formulae. Interest in this work on the radial matrix elements for large n and n' is related both to measurements of radio recombination lines from tenuous space plasmas, e.g. Stepkin et al (2007 Mon. Not. R. Astron. Soc. 374 852) and to the calculation of Stark broadening for such spectra, e.g. Gigosos et al (2007 Astron. Astrophys. 466 1189), Stambulchik et al (2007 Phys. Rev. E 75 016401) and Stambulchik and Maron (2008 J. Phys. B: At. Mol. Opt. Phys. 41 095703). In addition, we discuss the question of inaccuracy caused by the omission of fine structure in such calculations, and the numerical stability of the recurrence relations used to implement the line strength formulae.

Calidad de Imagen del Telescopio UNAM212

Science.gov (United States)

Cobos, F. J.; Teiada de Vargas, C.

1987-05-01

El telescopio UNAM2l2, del Observatorio Astronómico Nacional, situado en la Sierra de San Pedro Mártir (Baja California, México), cumplira en un futuro muy cercano siete años de uso para fines de investigación astronómica. Aunque en este tiempo no se ha efectuado un estudio sistemático acerca de su comportamiento óptico y de los factores que influyen en la calidad de las imágenes, se han realizado pruebas diversas, estudios parciales y reuniones especificas, cuyos resultados no siempre se han difundido ampliamente y generalmente no se han presentado por escrito. Es por ello que hemos creido necesario intentar una recopilación de la información existente para poder con ella establecer un diagnóstjco que, aunque no sea definitivo, sirva de base para futuros trabajos tendientes a optimizar el comportamiento óptico del telescopio. Es evidente que un buen número de las conclusiones que se presentan son resultado del trabajo de muchas personas ó de esfuerzos colectivos. Asimismo, hemos tratado de localizar información bibliográfica que pueda ser de utilidad. Nuestro objetivo primordial ha consistido en centrarnos en la óptica del telescopio y su calidad, pero también se han considerado otros aspectos que puedan afectar las imágenes obtenidas tales como: celda del primario, `seeing' local y externo, flexiones posibles en la estructura mecánica del telescopio, etc.

Shrinking of Binaries in a WIMPY Background at the Galactic Center

Science.gov (United States)

Hills, J. G.

2001-12-01

The nature of the dark matter in the Galactic Halo is still not clear. Constraints can be placed on it; e.g., it cannot be in baryons less massive than about 1022 grams (Hills, 1986, Astron. J. 92, 595). It may be in elementary weakly interacting massive particles, WIMPS. Apart from providing most of the mass of the Galaxy, the only known significant dynamical effect of WIMPS is to cause a gradual shrinking of tightly bound binaries (Hills 1983, Astron. J. 88, 1269) as they interact with the background soup of WIMPS. This effect may be observable in binaries close to the Galactic Center if a significant fraction of the mass density near the central black hole is from WIMPS. The requisite binaries would have to have orbital velocities greater than the local velocity dispersion of the WIMPS relative to the binary. The velocity dispersion increases near the black hole. The binary cannot be too close to the black hole or its tidal field will breakup the binary. If the local WIMP density is 107 g/cm3, the fractional rate of reduction in the binary orbital period is about 5 x 10-10/yr for a binary having a semimajor axis equal to 3 solar radii in a soup of WIMPS having a velocity dispersion of 200 km/s relative to the binary. This gradual erosion of the binary period may be detectable, particularly, if one of the binary components is a pulsar.

Cenários unificados para a expansão acelerada do Universo

OpenAIRE

Leila Lobato Graef

2015-01-01

Nos encontramos atualmente em um momento histórico privilegiado para a cosmologia. Na última década, o grande progresso das observações astronô- micas permitiu que diversos modelos cosmológicos pudessem ser testados com grande precisão. Com uma série de resultados observacionais sendo lançados, obtivemos informações valiosas sobre a expansão acelerada do universo primitivo e a expansão acelerada atual. Em sua essência, tais esforços observacionais buscam esclarecer algumas das questões mais ...

Formación de los planetas gigantes del Sistema Solar

OpenAIRE

Guilera, Octavio Miguel

2014-01-01

El estudio de los sistemas planetarios es uno de los temas fundamentales de las ciencias astronómicas. El interés en nuestro Sistema Solar surgió en tiempos remotos. Hace casi dos décadas, Mayor y Queloz (1995) detectaron el primer planeta extrasolar en órbita alrededor de una estrella de tipo solar. Este notable descubrimiento ha hecho surgir desde entonces un enorme interés en el estudio de sistemas planetarios en general. Esta Tesis es una continuación natural de un proyecto de i...

Procesos para una Astronomía que le aporte a Colombia

OpenAIRE

Duque Escobar, Gonzalo

2011-01-01

Se ha validado el Plan Nacional de Desarrollo Tecnológico en Astronomía 2011-2030, para el Plan Estratégico 2009-2012 de la Comisión Colombiana del Espacio CCE, por el Grupo de Astronáutica, Astronomía y Medicina Aeroespacial. Esperamos que el grupo de astrónomos convocado, responsable de la investigación centrado en procesos científicos existentes y no en distractores, pueda señalar las acciones pertinentes e identificar los recursos necesarios, para hacer viable un desarrollo científico y t...

Astronomia diurna

OpenAIRE

Gangui, Alejandro

2017-01-01

Durante los equinoccios, la secuencia temporal de las sombras proyectadas por cada uno de los puntos que forman cualquier objeto sigue una línea recta de oeste a este. Una construcción simple con hilos y un gnomon puede ser utilizada para materializar el plano de la proyección local del ecuador celeste, lo que nos ofrece una manera de calcular nuestra latitud astronómica durante el día con alta precisión. Se presenta un experimento que se puede realizar en horario diurno para ayudar a los est...

Studying AGN Jets At Extreme Angular Resolution

Science.gov (United States)

Bruni, Gabriele

2016-10-01

RadioAstron is a 10m antenna orbiting on the Russian Speckt-R spacecraft, launched in 2011. Performing radio interferometry with a global array of ground telescopes, it is providing record angular resolution. The Key Science Project on AGN polarization is exploiting it to study in great detail the configuration of magnetic fields in AGN jets, and understand their formation and collimation. To date, the project has already achieved the highest angular resolution image ever obtained in Astronomy, and detected brightness temperatures exceeding the ones predicted by theory of AGN.

Tearing instability in cylindrical plasma configuration

International Nuclear Information System (INIS)

Zelenyj, L.M.

1979-01-01

The effect of the neutral-layer cylindrical geometry on the development of the tearing instability has been investigated in detail. The increments of the instability for all the regimes have been found. The influence of cylindrical effects becomes manifesting itself at small, as compared to the layer characteristic thickness, distances from the axis, and, finally, the electron regime of the instability development transforms into an ion one. The results obtained are of interest for studying the plasma stability in the devices of the ''Astron'' type and in magnetospheres of cosmic objects

Application of Three-Dimensional Models for the Teaching of Time Zones. (Breton Title: Aplicação de Modelos Tridimensionais Para o Ensino de Fusos Horários.) Aplicación de Modelos Tridimensionales Para la Enseñanza de Husos Horarios

Science.gov (United States)

Azevedo Sobreira, Paulo Henrique

2012-07-01

There are several interesting astronomical topics that must be addressed in the High School and Elementary/Middle School in the disciplines of Geography and of Sciences. Among them, the topic of time zones which is one of the most important to understand the correlation of the Earth's rotation and its implications on daily activities of citizens in local scale, regional and global scales which involve problems of time differences. For the teaching of time zones in the lessons of Geography, for example, there are bi-dimensional representations of thematic maps of world time zones, textbooks and atlas. It happens that teachers face some difficulties to permit its students to view three-dimensionally this astronomical phenomenon from the textbooks available in schools. The aim of this paper is to present two proposals with low-cost materials, which allow the preparation of three-dimensional models for the teaching of time zones. Há vários temas astronômicos interessantes que devem ser trabalhados nos Ensinos Médio e Fundamental, nas disciplinas de Geografia e de Ciências. Entre eles, o tema dos fusos horários que é um dos mais importantes para se correlacionar a rotação da Terra e suas implicações nas atividades cotidianas dos cidadãos em escala local, regional e global, que envolvem problemas de diferenças horárias. Para o ensino dos fusos horários nas aulas de Geografia, por exemplo, há representações bidimensionais de mapas temáticos de fusos horários mundiais, nos livros didáticos e nos atlas. Ocorre que os professores enfrentam algumas dificuldades para possibilitar aos seus alunos a visão tridimensional deste fenômeno astronômico, a partir dos materiais didáticos disponíveis nas escolas. O objetivo deste trabalho é apresentar duas propostas para a confecção de materiais de baixo custo, que possibilitem a elaboração de modelos tridimensionais para o ensino dos fusos horários. Hay algunos temas astronómicos interesantes que se

Learning Astronomy by Playing in a Park. (Spanish Title: Aprender AstronoMía Jugando en Una Plaza.) Aprender Astronomia Brincando em Uma Praça

Science.gov (United States)

Camino, Néstor

2012-12-01

Some public-square games are presented in this paper, considered as didactic modules to help children imagine astronomical processes, based on the concept that learning in Astronomy should be developed to strengthen the relationship of our body with three-dimensional space and time, much in the same way we experience when observing the actual sky, holding a permanent "dialogue" between the actual world and what is to be learned. The games presented (merry-go-rounds and slides) were designed to work on the astronomical concepts related to the translation of the Earth around the Sun, the phases of the Moon and gravity, and on what is perceived by an observer about those phenomena. The description of each game, their physical and astronomical foundations, and a critical comment about their didactical importance are the key parts of the paper. Finally, a recommendation is given about the role teachers should play to be essential partners in the process of learning Astronomy by means of the interaction with these games. Se presentan en este trabajo algunos juegos de plaza, considerados como módulos didácticos para imaginar procesos astronómicos, a partir de la concepción de que el aprendizaje en Astronomía debe desarrollarse fortaleciendo la relación del propio cuerpo con el espacio tridimensional y con el tiempo, tal como se vive al observar el cielo, construyendo un "diálogo" entre el mundo real y los aprendizajes a construir. Los juegos presentados (calesitas y toboganes) fueron diseñados para trabajar sobre la traslación de la Tierra en torno al Sol, las fases de la Luna y la gravedad, y sobre lo que un observador percibe de los mismos. Se da la descripción de cada juego, se discuten sus fundamentos físicos y astronómicos, y se desarrolla una crítica didáctica de los mismos. Finalmente, se comenta el rol que deberían tener los docentes en el acompañamiento a los aprendices en el proceso de interacción con los juegos presentados. Apresentam-se neste

La Enseñanza/Aprendizaje del Modelo Sol-Tierra Análisis de la Situación Actual y Propuesta de Mejora Para la Formación de los Futuros Profesores de Primaria

Science.gov (United States)

Martínez Sebastià, Bernat

2004-12-01

This work is an extened summary of the autor's PhD thesis. It deals with the teaching of astronomy (day/night, seasons) in primary school. At first, students teachers' undestanding of astronomical concepts related to Sun-Earth system have been analysed. Taking into account the results of the previous analysis and using a socio-constructivist approach a teaching sequence has been designed. This sequence has been tested with different groups of students teachers showing an improvement in their undestanding of elementary astronomical concepts. El trabajo que presentamos es un resumen extenso de la tesis doctoral del autor. El enfoque utilizado ha sido tratar de ligar la investigación sobre las ideas, razonamientos y obstáculos de los profesores de primaria con la planificación de la enseñanza del modelo Sol-Tierra que permite explicar el ciclo día/noche y las estaciones. En primer lugar, se ha procedido a realizar un análisis crítico de los resultados que se obtienen en el aprendizaje de los contenidos astronómicos en la enseñanza habitual. En segundo lugar se ha diseñado un curriculum potencialmente superador de esta situación desde una orientación que concibe la enseñanza y el aprendizaje como un proceso de construcción de conocimientos en una estructura problematizada. Finalmente, esta secuencia didáctica ha sido experimentada con diferentes grupos de estudiantes de magisterio, mostrando una mejora relevante en la comprensión de los conceptos astronómicos fundamentales.

Polarimetric survey of main-belt asteroids. II. Results for 58 B- and C-type objects

Science.gov (United States)

Gil-Hutton, R.; Cañada-Assandri, M.

2012-03-01

Aims: We present results of a polarimetric survey of main-belt asteroids at Complejo Astronómico el Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. Methods: The data were obtained with the Torino and CASPROF polarimeters at the 2.15m telescope. The Torino polarimeter is an instrument that allows simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation. Results: The survey began in 2003, and up to 2009 data on a sample of more than 170 asteroids were obtained. In this paper the results for 58 B- and C-type objects are presented, most of them polarimetrically observed for the first time. Using these data we find phase-polarization curves and polarimetric parameters for these taxonomic classes. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.Tables 1 and 2 are available in electronic form at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/539/A115

Projeto observatórios virtuais: educação através de telescópios robóticos

Science.gov (United States)

Santana, P. H. S.; Shida, R. Y.

2003-08-01

O principal objetivo do projeto Observatórios Virtuais é o ensino na área de ciências através de atividades práticas desenvolvidas em colaboração entre instituições de pesquisa em astronomia e escolas de ensino médio e fundamental. Este ano deverá ser concluída a implantação do programa piloto de estudos, pesquisas e observação astronômica direta, com utilização em tempo real de telescópios robóticos, que assim funcionarão como "observatórios virtuais". O objetivo pedagógico das atividades práticas baseadas nas imagens atronômicas é desenvolver as habilidades e competências dos alunos no uso do método científico. Para isso, serão realizados projetos interdisciplinares, a partir de observações astronômicas, já que a astronomia é uma área interdisciplinar por excelência. Essas atividades terão níveis diferenciados de complexidade, que podem ser adequados aos vários graus do ensino e realidades regionais. Será dada ênfase ao desenvolvimento e aplicação em São Paulo, onde atua a equipe do IAG/USP. Como resultados apresentados no presente trabalho, temos a criação de um software em português para o processamento de imagens obtidas através de CCDs e a elaboração de material para as atividades educacionais relacionadas.

Comportamiento de la cromósfera solar en la línea H-alfa durante el período enero/05-agosto/06

Science.gov (United States)

Missio, H.; Davoli, D.; Aquilano, R.

Using the instrument at Observatorio Astronómico Municipal de Rosario (OAMR), we analyze the solar chromospheric activity during the period January/05-August/06. The instrument is a Carl Zeiss refractor telescope of 150 mm aperture and 2250 mm of focal distance with a monochromatic filter in the H-alpha line. We take as proxy for the solar activity the area covered by chromospheric ``plages''. The measurements are done using photographic registers. We describe our technique and the results obtained. We observe a decrease of solar activity that corresponds to the end of cycle 23. FULL TEXT IN SPANISH

Avances en la automatización del Telescopio Horacio Ghielmetti

Science.gov (United States)

Schwartz, M. A.; Mauas, P.; Melita, M.; Buccino, A. P.; Pellizza, L.; Petrucci, R.; Jofré, E.; Perna, P.; Pereira, M.; Fernandez, G.; Godoy, R.; Pereyra, P.; Pinto, J.

In this work we present the progress made in the last year related to the project of automation of the Meade 16" Horacio Ghielmetti Telescope (HGT), located on the Burek Hill of the Complejo Astronómico El Leoncito, San Juan, Argentina. With an experience of more than 6 months of working remotely, we summarize the problems we had and the solutions we adopted for the remote control of the HGT, we describe its current state, and we present some of the innovations we have to carry out in the near future. FULL TEXT IN SPANISH

Gravitational Rutherford scattering and Keplerian orbits for electrically charged bodies in heterotic string theory

International Nuclear Information System (INIS)

Villanueva, J. R.; Olivares, Marco

2015-01-01

Properties of the motion of electrically charged particles in the background of the Gibbons–Maeda–Garfinkle–Horowitz–Strominger black hole is presented in this paper. Radial and angular motions are studied analytically for different values of the fundamental parameter. Therefore, gravitational Rutherford scattering and Keplerian orbits are analyzed in detail. Finally, this paper complements previous work by Fernando for null geodesics (Phys Rev D 85:024033, 2012), Olivares and Villanueva (Eur Phys J C 73:2659, 2013) and Blaga (Automat Comp Appl Math 22:41–48, 2013; Serb Astron 190:41, 2015) for time-like geodesics

Modelling of charged satellite motion in Earth's gravitational and magnetic fields

Science.gov (United States)

Abd El-Bar, S. E.; Abd El-Salam, F. A.

2018-05-01

In this work Lagrange's planetary equations for a charged satellite subjected to the Earth's gravitational and magnetic force fields are solved. The Earth's gravity, and magnetic and electric force components are obtained and expressed in terms of orbital elements. The variational equations of orbit with the considered model in Keplerian elements are derived. The solution of the problem in a fully analytical way is obtained. The temporal rate of changes of the orbital elements of the spacecraft are integrated via Lagrange's planetary equations and integrals of the normalized Keplerian motion obtained by Ahmed (Astron. J. 107(5):1900, 1994).

Cámara CCD Directa con el Telescopio de 2.15 m del CASLEO: algunos diagnósticos

Science.gov (United States)

Cellone, S. A.

Se efectuaron algunas pruebas con la cámara CCD (+ Reductor Focal) instalada en el foco Cassegrain del Telescopio de 2.15 m del Complejo Astronómico El Leoncito (CASLEO). Las conclusiones más significativas son: Los tiempos de exposición efectivos difieren de los nominales en una fracción apreciable de segundo. En exposiciones de menos de 3 segundos, la iluminación no es pareja en todo el detector. En consecuencia, se recomiendan los pasos a seguir por los astrónomos tanto durante la observación como en la reducción de sus datos.

Gravitational Rutherford scattering and Keplerian orbits for electrically charged bodies in heterotic string theory

Energy Technology Data Exchange (ETDEWEB)

Villanueva, J.R. [Universidad de Valparaiso, Instituto de Fisica y Astronomia, Valparaiso (Chile); Centro de Astrofisica de Valparaiso, Valparaiso (Chile); Olivares, Marco [Universidad Diego Portales, Avenida Ejercito Libertador 441, Facultad de Ingenieria, Santiago (Chile)

2015-11-15

Properties of the motion of electrically charged particles in the background of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole is presented in this paper. Radial and angular motions are studied analytically for different values of the fundamental parameter. Therefore, gravitational Rutherford scattering and Keplerian orbits are analyzed in detail. Finally, this paper complements previous work by Fernando for null geodesics (Phys Rev D 85:024033, 2012), Olivares and Villanueva (Eur Phys J C 73:2659, 2013) and Blaga (Automat Comp Appl Math 22:41-48, 2013; Serb Astron 190:41, 2015) for time-like geodesics. (orig.)

Las escalas de la luz

OpenAIRE

Beckers, Benoit

2009-01-01

Variando con el paso del día y del año, la luz del Sol y del cielo modula, visual y energéticamente, los territorios, las ciudades y los edificios. ¿Cómo sintetizar y manejar en el proyecto estas informaciones donde se mezcla el azar de las nubes pasajeras con la regularidad astronómica de los trayectos solares? En cuanto a las herramientas de simulación, el mayor avance de estos últimos años se ha producido en los programas de renderización, con los cuales nos vemos forzados a construi...

Educación no formal

Science.gov (United States)

Tignanelli, H.

Se comentan en esta comunicación, las principales contribuciones realizadas en el campo de la educación en astronomía en los niveles primario, secundario y terciario, como punto de partida para la discusión de la actual inserción de los contenidos astronómicos en los nuevos contenidos curriculares de la EGB - Educación General Básica- y Polimodal, de la Reforma Educativa. En particular, se discuten los alcances de la educación formal y no formal, su importancia para la capacitación de profesores y maestros, y perspectivas a futuro.

Modelo numérico tri-dimensional linear da plataforma continental do Estado do Maranhão Linear three-dimensional numerical model of Maranhão State continental shelf

Directory of Open Access Journals (Sweden)

José Edson Rodrigues Pereira

1995-01-01

Full Text Available Um modelo numérico hidrodinámico tri-dimensional linear, do tipo Heaps, foi implementado para a plataforma continental do Estado do Maranhão, visando a simulação da circulação gerada por efeitos astronômicos e meteorológicos na área. O modelo foi processado para cinco condições, a fim de calcular a circulação na plataforma devida aos seguintes efeitos: componente de maré semi-diurna lunar principal (M2, composição das principais componentes astronômicas de maré na área, condições meteorológicas médias de verão, condições meteorológicas médias de inverno e forçantes de maré em períodos específicos de interesse. Mapas cotidais e elipses de correntes da componente M2 foram obtidos, sendo esta componente preponderante na circulação local. Elevações e correntes sazonais médias são, em geral, muito menores que as astronômicas, permitindo o uso apenas de forçantes de maré em previsões hidrodinámicas. As simulações do modelo foram satisfatórias na plataforma e menos precisas nas baías e áreas internas rasas, onde atrasos de fase significativos são observados, devido a efeitos de menor escala que a adotada pelo modelo.A linear three-dimensional hydrodynamical numerical model, Heaps type, was implemented to the continental shelf of Maranhão State, aiming the simulation of the circulation generated by astronomical and meteorological effects in that area. Five runs of the model were performed, in order to compute the circulation in the shelf due to the following effects: principal lunar semi-diurnal component (M2, composition of the principal astronomical components in the area, mean summer meteorological conditions, mean winter meteorological conditions and tidal forcing in specific periods of interest. M2 cotidal maps and currents ellipses were obtained, that one being the most important component in the tidal circulation. Mean seasonal elevations and currents are generally much smaller than the

Coupling the nongravitational forces and modified Newton dynamics for cometary orbits

Science.gov (United States)

Maquet, Lucie; Pierret, Frédéric

2015-04-01

In recent work [L. Blanchet and J. Novak, Mon. Not. R. Astron. Soc. 412, 2530 (2011); L. Blanchet and J. Novak, Testing MOND in the Solar System (2011); and M. Milgrom, Mon. Not. R. Astron. Soc. 399, 474 (2009)], the authors showed that modified Newton dynamics (MOND) has a non-negligible secular perturbation effect on planets with large semimajor axes (gaseous planets) in the Solar System. Some comets also have a very eccentric orbit with a large semimajor axis (Halley family comets) going far away from the Sun (more than 15 AU) in a low acceleration regime where they would be subject to MOND perturbation. They also approach the Sun very closely (less than 3 AU) and are affected by the sublimation of ices from their nucleus, triggering so-called nongravitational forces. The main goal of this paper is to investigate the effect of MOND perturbation on three comets with various orbital elements (2 P /Encke , 1 P /Halley and 153 P /Ikeya-Zhang ) and then compare it to the nongravitational perturbations. It is motivated by the fact that when fitting an outgassing model for a comet, we have to take into account all of the small perturbing effects to avoid absorbing these effects into the nongravitational parameters. Otherwise, we could derive a completely wrong estimation of the outgassing. For this work, we use six different forms of MOND functions and compute the secular variations of the orbital elements due to MOND and nongravitational perturbations. We show that, for comets with large semimajor axis, the MONDian effects are not negligible compared to the nongravitational perturbations.

Velocity-mass correlation of the O-type stars: model results

International Nuclear Information System (INIS)

Stone, R.C.

1982-01-01

This paper presents new model results describing the evolution of massive close binaries from their initial ZAMS to post-supernova stages. Unlike the previous conservative study by Stone [Astrophys. J. 232, 520 (1979) (Paper II)], these results allow explicitly for mass loss from the binary system occurring during the core hydrogen- and helium-burning stages of the primary binary star as well as during the Roche lobe overflow. Because of uncertainties in these rates, model results are given for several reasonable choices for these rates. All of the models consistently predict an increasing relation between the peculiar space velocities and masses for runaway OB stars which agrees well with the observed correlations discussed in Stone [Astron. J. 86, 544 (1981) (Paper III)] and also predict a lower limit at Mroughly-equal11M/sub sun/ for the masses of runaway stars, in agreement with the observational limit found by A. Blaauw (Bull. Astron. Inst. Neth. 15, 265, 1961), both of which support the binary-supernova scenario described by van den Heuvel and Heise for the origin of runaway stars. These models also predict that the more massive O stars will produce correspondingly more massive compact remnants, and that most binaries experiencing supernova-induced kick velocities of magnitude V/sub k/> or approx. =300 km s -1 will disrupt following the explosions. The best estimate for this velocity as established from pulsar observations is V/sub k/roughly-equal150 km s -1 , in which case probably only 15% if these binaries will be disrupted by the supernova explosions, and therefore, almost all runaway stars should have either neutron star or black hole companions

Polarimetric survey of main-belt asteroids⋆. III. Results for 33 X-type objects

Science.gov (United States)

Cañada-Assandri, M.; Gil-Hutton, R.; Benavidez, P.

2012-06-01

Aims: We present results of a polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (Casleo), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. Methods: The data were obtained with the Torino and CASPROF polarimeters at the 2.15 m telescope. The Torino polarimeter is an instrument that allows the simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation. Results: The survey began in 2003, and up to 2009 data of a sample of more than 170 asteroids were obtained. In this paper the results for 33 X-type objects are presented, several of them are being polarimetrically observed for the first time. Using these data we found polarization curves and polarimetric parameters for different groups among this taxonomic class and that there are objects with very different albedo in the sub-classes of the X taxonomic complex. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/542/A11

The extreme blazar AO 0235+164 as seen by extensive ground and space radio observations

Science.gov (United States)

Kutkin, A. M.; Pashchenko, I. N.; Lisakov, M. M.; Voytsik, P. A.; Sokolovsky, K. V.; Kovalev, Y. Y.; Lobanov, A. P.; Ipatov, A. V.; Aller, M. F.; Aller, H. D.; Lahteenmaki, A.; Tornikoski, M.; Gurvits, L. I.

2018-04-01

Clues to the physical conditions in radio cores of blazars come from measurements of brightness temperatures as well as effects produced by intrinsic opacity. We study the properties of the ultra-compact blazar AO 0235+164 with RadioAstron ground-space radio interferometer, multifrequency VLBA, EVN, and single-dish radio observations. We employ visibility modelling and image stacking for deriving structure and kinematics of the source, and use Gaussian process regression to find the relative multiband time delays of the flares. The multifrequency core size and time lags support prevailing synchrotron self-absorption. The intrinsic brightness temperature of the core derived from ground-based very long baseline interferometry (VLBI) is close to the equipartition regime value. In the same time, there is evidence for ultra-compact features of the size of less than 10 μas in the source, which might be responsible for the extreme apparent brightness temperatures of up to 1014 K as measured by RadioAstron. In 2007-2016 the VLBI components in the source at 43 GHz are found predominantly in two directions, suggesting a bend of the outflow from southern to northern direction. The apparent opening angle of the jet seen in the stacked image at 43 GHz is two times wider than that at 15 GHz, indicating a collimation of the flow within the central 1.5 mas. We estimate the Lorentz factor Γ = 14, the Doppler factor δ = 21, and the viewing angle θ = 1.7° of the apparent jet base, derive the gradients of magnetic field strength and electron density in the outflow, and the distance between jet apex and the core at each frequency.

Nuevas aplicaciones científicas del telescopio astrográfico doble de la estación de altura Carlos U. Cesco (OAFA)

Science.gov (United States)

González, E. P. A.; Podesta, F.

2017-10-01

For the last 50 years, the Double Astrograph located at the Carlos U. Cesco station of the Observatorio Astronómico Felix Aguilar, San Juan, Argentina, was used for observations and research in the field of astrometry. The main programs involved the study of asteroid positions and proper motions of stars in the southern hemisphere, being the latter a long time project that is near completion from which the SPM4 catalog is the most recent version. In this paper, new scientific applications in the field of photometry that can be accomplished with this telescope are presented. These first attempts show the potential of the instrument for such tasks.

The Science Teachers and Their way of Thinking about Astronomy. (Spanish Title: Los Profesores de Ciencias y Sus Formas de Pensar la Astronomía.) Os Professores de Ciências e Suas Formas de Pensar a Astronomia

Science.gov (United States)

Leite, Cristina; Hosoume, Yassuko

2007-12-01

The research presented in this article is about the way science teachers from Elementary School think about astronomical elements. Its methodology is based on semi-structured interviews, which were video recorded. The research is centered in a three-dimensional perspective of astronomical Earth, the Sun, the Moon, the planets and the stars, and also the conceptions about sky and Universe. The esults indicate a Universe that contains: Sun, stars, planets and Moon; where the Solar System is a little part of the whole. Sometimes they think that the Solar System is the Universe. The objects are in the sky or in the Universe, which, for many of them, is only the space above the Earth. The flat shape of astronomical objects and the spatial structure of the Universe are striking features. Many of them think that Sun and stars are different: the Sun is a hot object and the stars are cold ones. These results worry us and they certainly indicate how urgent it is to plan Professional Development in Astronomy for teachers, after all the PCN's emphasize that this subject is important to be taught. El objeto de investigación de este artículo es la manera de pensar sobre los elementos de la Astronomía de los profesores de Ciencias en la enseñanza fundamental. La metodología consiste en entrevistas semi-estructuradas, filmadas en video y centradas en la tridimensionalidad de los elementos astronómicos, para posibilitar un mapeamiento de las concepciones sobre las formas y dimensiones de la Tierra, del Sol, de la Luna, de los planetas y de las estrellas, como también de la concepción de cielo y de Universo en su totalidad. Los resultados indican un Universo conteniendo: Sol, estrellas, planetas y Luna, donde el Sistema Solar se ubica como parte. Algunas veces, el Universo es concebido como el propio Sistema Solar. Los objetos están en el cielo o en el Universo, que, para muchos, se restringe al espacio que está arriba de la Tierra. La forma plana de los objetos astron

Testing cosmology from fundamental considerations: Is the Friedmann universe intrinsically flat

Science.gov (United States)

Mitra, Abhas

2014-02-01

Recently Melia and Shevchuk (Mon Not R Astron Soc 419:2579,2012) (MS) have proposed the so-called cosmology where the "Gravitational Horizon" of the universe is equal to the distance travelled by light since "Big Bang". Here we would like to see whether the basic claim is correct or not because MS have not given any cogent derivation for the same. Essentially we will compare the twin expressions for the Einstein energy momentum complex (EMC) of the Friedmann universe obtained by using an appropriate superpotential and also by a direct method. To enable a meaningful comparison of the twin expressions, both are computed by using the same quasi-Cartesian coordinates. We however do not claim that Einstein EMC is superior to many other routes of defining EM of a self-gravitating system. In fact, for static isolated spherical syatems, the idea of a coordinate independent field energy of Lynden-Bell and Katz (Mon Not R Astron Soc 213:21, 1985) might be quite physically significant. Yet, here, we use Einstein EMC because (i) our system is non-static and not isolated one (ii) our primary aim is not find any absolute value of EM, and, finally, (iii) only Einstein pseudo-tensor offers equivalent twin expressions for EM which one can be equated irrespective of any physical significance. Following such comparison of equivalent twin expressions of Einstein energy, we find an exact proof as to why Friedmann universe must be spatially flat even though, mathematically one can conceive of curved spaces in any dimension. Additionally, it follows that, apparently, the scale factor as insisted by proposition. Nonetheless, because of close similarity of this form, , with the (vacuum) Milne metric, and also because of implied unphysical equation of state, cosmology is unlikely to represent the physical universe.

Variations of Synchrotron Radio Emissions from Jupiter's Inner Radiation Belt

Science.gov (United States)

Lou, Y.-Q.

2017-09-01

Variations of Synchrotron Radio Emissions from Jupiter's Inner Radiation Belt Yu-Qing Lou* Physics Department, Tsinghua Centre for Astrophysics (THCA), Tsinghua-National Astronomical Observatories of China (NAOC) joint Research Centre for Astrophysics, Tsinghua University, Beijing 100084, China We describe the basic phenommenology of quasi-periodic 40 minute (QP-40) polar burst activities of Jupiter and their close correlation with the solar wind speed variations at the Jovian magnetosphere. Physically, relativistic electrons of QP-40 bursts most likely come from the circumpolar regions of the inner radiation belt (IRB) which gives off intense synchroton radio emissions in a wide wavelength range. Such relativistic electron bursts also give rise to beamed low-frequency radio bursts along polar magnetic field lines with distinct polarizations from Jupiter's two polar regions. Jovian aurora activities are expected to be also affected by such QP-40 burst activities. We present evidence of short-term (typical timescales shorter than an hour) variabilities of the IRB at 6cm wavelength and describe recent joint radio telescope observation campaign to monitor Jupiter in coordination with JUNO spacecraft. Except for low-frequency polarization features, we anticipate JUNO to detect QP-40 activities from both polar regions during the arrival of high-speed solar wind with intermittency. References 1. Y.-Q. Lou, The Astrophysical Journal, 548, 460 (2001). 2. Y.-Q. Lou, and C. Zheng, Mon. Not. Roy. Astron. Soc. Letters, 344, L1 (2003). 3. Y.-Q. Lou, H. G. Song, Y.Y. Liu, and M. Yang, Mon. Not. Roy. Astron. Soc. Letters, 421, L62 (2012). 4. Y.-Q. Lou, Geophysical Research Letters, 23, 609 (1996). 5. Y.-Q. Lou, Journal of Geophysical Research, 99, 14747 (1994). 6. G. R. Gladstone, et al., Nature, 415, 1000 (2002).

Inauguração do Telescópio SOAR

Science.gov (United States)

Steiner, João

2004-04-01

A comunidade astronômica brasileira de há muito almeja ter a sua disposição um instrumento científico com o qual possa fazer pesquisa de vanguarda e manter a competitividade científica a nível internacional. Hoje este sonho se torna uma realidade. O Brasil tem tido uma política de pesquisa e de pós-graduação bem sucedida. Estamos formando 7000 doutores por ano e produzimos 1,5% da ciência mundial. Nosso desafio, hoje, é associar a esta capacidade de gerar conhecimento também a capacidade de usar o conhecimento em beneficio da sociedade. A Astronomia não é exceção. Temos 7 programas de pós-graduação em nível de doutorado e 11 em nível de mestrado. O telescópio SOAR será o principal instrumento que sustentará estes programas nas próximas décadas. A inauguração do telescópio SOAR simboliza de forma concreta e decidida o apoio do MCT, do CNPq e da FAPESP para o financiamento à pesquisa básica em nosso país. O Laboratório Nacional de Astrofísica, criado a cerca de 20 anos pelo CNPq, a par do Laboratório Nacional de Luz Sincrotron, são até hoje, os únicos laboratórios nacionais do Brasil e ambos voltados basicamente ao avanço do conhecimento. Os vinte anos de existência do LNA foram decisivos para a estruturação da comunidade astronômica no Brasil e para a construção das parcerias como o SOAR.

Probing modifications of general relativity using current cosmological observations

International Nuclear Information System (INIS)

Zhao Gongbo; Bacon, David J.; Koyama, Kazuya; Nichol, Robert C.; Song, Yong-Seon; Giannantonio, Tommaso; Pogosian, Levon; Silvestri, Alessandra

2010-01-01

We test general relativity (GR) using current cosmological data: the CMB from WMAP5 [E. Komatsu et al. (WMAP Collaboration), Astrophys. J. Suppl. Ser. 180, 330 (2009)], the integrated Sachs-Wolfe (ISW) effect from the cross correlation of the CMB with six galaxy catalogs [T. Giannantonio et al., Phys. Rev. D 77, 123520 (2008)], a compilation of supernovae (SNe) type Ia including the latest Sloan Digital Sky Survey SNe [R. Kessler et al., Astrophys. J. Suppl. Ser. 185, 32 (2009).], and part of the weak lensing (WL) data from the Canada-Franco-Hawaii Telescope Legacy Survey [L. Fu et al., Astron. Astrophys. 479, 9 (2008); M. Kilbinger et al., Astron. Astrophys. 497, 677 (2009).] that probe linear and mildly nonlinear scales. We first test a model in which the effective Newtonian constant μ and the ratio of the two gravitational potentials, η, transit from the GR value to another constant at late times; in this case, we find that GR is fully consistent with the combined data. The strongest constraint comes from the ISW effect which would arise from this gravitational transition; the observed ISW signal imposes a tight constraint on a combination of μ and η that characterizes the lensing potential. Next, we consider four pixels in time and space for each function μ and η, and perform a principal component analysis, finding that seven of the resulting eight eigenmodes are consistent with GR within the errors. Only one eigenmode shows a 2σ deviation from the GR prediction, which is likely to be due to a systematic effect. However, the detection of such a deviation demonstrates the power of our time- and scale-dependent principal component analysis methodology when combining observations of structure formation and expansion history to test GR.

Polarimetric survey of main-belt asteroids. I. Results for fifty seven S-, L-, and K-type objects

Science.gov (United States)

Gil-Hutton, R.; Cañada-Assandri, M.

2011-05-01

Aims: We present the first results of a polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (Casleo), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties, similar to those shown by the asteroid (234) Barbara. Methods: The data were obtained with the Torino and CASPROF polarimeters at the 2.15 m telescope. The Torino polarimeter is an instrument that allows the simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation. Results: The survey began in 2003, and up to 2009 data on a sample of more than 170 asteroids were obtained. In this paper the results of 57 S-, L-, and K-type objects are presented, most of them are being polarimetrically observed for the first time. Using these data we find phase-polarization curves and polarimetric parameters for these taxonomic classes. Furthermore, we also find two candidates, (397) Vienna and (458) Hercynia, that could have a phase-polarization curve with a large inversion angle. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/A+A/529/A86

The Universe Observing Center a modern center to teach and communicate astronomy

Science.gov (United States)

Ribas, Salvador J.

2011-06-01

The Universe Observing Center is one of the parts of the Parc Astronòmic Montsec (PAM). PAM is an initiative of the Catalan government, through the Consorci del Montsec (Montsec Consortium), to take advantage of the capabilities and potential of the Montsec region to develop scientific research, training and outreach activities, particularly in the field of Astronomy. The choice of the Montsec mountains to install the PAM was motivated by the magnificent conditions for observing the sky at night; the sky above Montsec is the best (natural sky free of light pollution) in Catalonia for astronomical observations. The PAM has two main parts: the Observatori Astronòmic del Montsec (OAdM) and the Universe Observing Center (COU). The OAdM is a professional observatory with an 80-cm catadioptric telescope (Joan Oró Telescope). This telescope is a robotic telescope that can be controlled from anywhere in the world via the Internet. The COU is a large multipurpose center which is intended to become an educational benchmark for teaching and communicate astronomy and other sciences in Catalonia. The management of the COU has three main goals: 1) Teach primary and secondary school students in our Educational Training Camp. 2) Teach university students housing the practical astronomy lectures of the universities. 3) Communicate astronomy to the general public. The COU comprises special areas for these purposes: the Telescopes Park with more than 20 telescopes, a coelostat for solar observations and two dome containing full-automated telescopes. The most special equipment is ``The Eye of Montsec'', with its 12m dome containing a multimedia digital planetarium and a platform for direct observation of the sky and the environment. During 2009 we expect around 10000 visitors in Montsec area to enjoy science with Montsec dark skies and an special natural environment.

Polarimetric survey of main-belt asteroids. IV. New results from the first epoch of the CASLEO survey

Science.gov (United States)

Gil-Hutton, R.; Cellino, A.; Bendjoya, Ph.

2014-09-01

Aims: We present results of a polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. Methods: The data were obtained using the Torino and CASPROF polarimeters at the 2.15m telescope. The Torino polarimeter is an instrument that allows simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation. Results: The survey began in 1995, and until 2012 data on a large sample of asteroids were obtained. We here present and analyze the unpublished results for 129 asteroids of different taxonomic types, 56 which were polarimetrically observed for the first time. We find that the asteroids (402) Chloe and (729) Watsonia are Barbarians, and asteroid (269) Justitia shows a phase - polarization curve that seems to have a small inversion angle. Data obtained in UBVRI colors allow us to sketch an analysis of the wavelength dependence of the degree of linear polarization for 31 asteroids, in spite of some large error bars in some cases. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/569/A122

Ciclos climáticos e causas naturais das mudanças do clima

Directory of Open Access Journals (Sweden)

Marcos José de Oliveira

2018-01-01

Full Text Available A periódica mudança climática na Terra pode ser explicada por um número reduzido de fatores terrestres e astronômicos. Nas escalas anual/diária, o clima obedece aos movimentos de translação e de rotação. Ciclos climáticos de períodos médios (décadas/séculos/milênios relacionam-se a mudanças na radiação solar, provocadas pela influência de grandes planetas do Sistema Solar. As oscilações oceânicas (ordem decadal são possivelmente causadas por influências planetárias e lunares. Ciclos climáticos longos (dezenas a centenas de milhares de anos são causados por variações nos parâmetros da órbita da Terra (excentricidade, obliquidade e precessão. Eventos de impacto de grandes corpos no planeta e extinções em massa de espécies advêm de superciclos (dezenas de milhões de anos provocados pela oscilação vertical do Sistema Solar em relação ao plano galáctico. Tectonismo, vulcanismo e a evolução de supercontinentes exibem superciclos (centenas de milhões de anos induzidos pelo deslocamento do Sistema Solar ao redor do centro da Via Láctea e pela variação de raios cósmicos. Fatores astronômicos permeiam praticamente todas as ordens dos ciclos climáticos e atuam direta ou indiretamente nos processos bio-geo-oceânico-atmosféricos. Conclui-se que o clima na Terra é caracterizado por ciclos controlados astronomicamente pela Lua, o Sol, os planetas, o Sistema Solar e, até mesmo, a Galáxia.

Cosmology and the Subgroups of Gamma-ray Bursts

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A. Mészáros

2011-01-01

Full Text Available Both short and intermediate gamma-ray bursts are distributed anisotropically in the sky (Mészáros, A. et al. ApJ, 539, 98 (2000, Vavrek, R. et al. MNRAS, 391, 1 741 (2008. Hence, in the redshift range, where these bursts take place, the cosmological principle is in doubt. It has already been noted that short bursts should be mainly at redshifts smaller than one (Mészáros, A. et al. Gamma-ray burst: Sixth Huntsville Symp., AIP, Vol. 1 133, 483 (2009; Mészáros, A. et al. Baltic Astron., 18, 293 (2009. Here we show that intermediate bursts should be at redshifts up to three.

Perspectivas Futuras para o Observatório do Pico dos Dias

Science.gov (United States)

Bruch, Albert

2004-02-01

Com o Observatório Gemini plenamente operacional e o telescópio SOAR iniciando suas operações em breve, a astronomia observacional brasileira encontra-se no auge de uma transformação profunda que terá um impacto grave no Observatório do Pico dos Dias - OPD. Refletimos aqui sobre a natureza desse impacto e estratégias para manter a competitividade do OPD. Não queremos apresentar receitas prontas, mas idéias que poderão servir como base de discussão sobre o uso inteligente dos telescópios do OPD como parte do conjunto de instrumentos disponíveis à comunidade astronômica brasileira.

Integrated spectral study of small angular diameter galactic open clusters

Science.gov (United States)

Clariá, J. J.; Ahumada, A. V.; Bica, E.; Pavani, D. B.; Parisi, M. C.

2017-10-01

This paper presents flux-calibrated integrated spectra obtained at Complejo Astronómico El Leoncito (CASLEO, Argentina) for a sample of 9 Galactic open clusters of small angular diameter. The spectra cover the optical range (3800-6800 Å), with a resolution of ˜14 Å. With one exception (Ruprecht 158), the selected clusters are projected into the fourth Galactic quadrant (282o evaluate their membership status. The current cluster sample complements that of 46 open clusters previously studied by our group in an effort to gather a spectral library with several clusters per age bin. The cluster spectral library that we have been building is an important tool to tie studies of resolved and unresolved stellar content.

Jeans' criterion and nonextensive velocity distribution function in kinetic theory

International Nuclear Information System (INIS)

Du Jiulin

2004-01-01

The effect of nonextensivity of self-gravitating systems on the Jeans' criterion for gravitational instability is studied in the framework of Tsallis statistics. The nonextensivity is introduced in the Jeans problem by a generalized q-nonextensive velocity distribution function through the equation of state of ideal gas in nonextensive kinetic theory. A new Jeans' criterion is deduced with a factor √(2/(5-3q)) that, however, differs from that one in [Astron. Astrophys. 396 (2002) 309] and new results of gravitational instability are analyzed for the nonextensive parameter q. An understanding of physical meaning of q and a possible seismic observation to find astronomical evidence for a value of q different from unity are also discussed

The CASLEO Polarimetric Survey of Main Belt Asteroids: Updated results

Science.gov (United States)

Gil-Hutton, R.; Cellino, A.; Cañada-Assandri, M.

2011-10-01

We present updated results of the polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (Casleo), San Juan, Argentina, using the 2.15 m telescope and the Torino and CASPROF polarimeters. The goals of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids belonging to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. The survey began in 2003, and data for a sample of more than 170 asteroids have been obtained, most of them having been polarimetrically observed for the first time. Using these data we find phase-polarization curves and polarimetric parameters for several taxonomic classes.

Time Resolved Precision Differential Photometry with OAFA's Double Astrograph

Science.gov (United States)

González, E. P. A.; Podestá, F.; Podestá, R.; Pacheco, A. M.

2018-01-01

For the last 50 years, the Double Astrograph located at the Carlos U. Cesco station of the Observatorio Astronómico Félix Aguilar (OAFA), San Juan province, Argentina, was used for astrometric observations and research. The main programs involved the study of asteroid positions and proper motions of stars in the Southern hemisphere, being the latter a long time project that is near completion from which the SPM4 catalog is the most recent version (Girard et al. 2011). In this paper, new scientific applications in the field of photometry that can be accomplished with this telescope are presented. These first attempts show the potential of the instrument for such tasks.

En el lado oscuro de la luna

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Ricardo Rodríguez Morales

2001-09-01

Full Text Available En 1970, a escasos meses de concluida la hazaña que llevó al hombre por primera vez a la Luna, la Unión Astronómica Internacional bautizaba con el nombre del colombiano Julio Garavito Armero un cráter selenita -situado a 48 grados de latitud sur y 157 grados de longitud este; tiene un diámetro de unos 80 km y se encuentra rodeado por un escarpado de unos 3.000 m con un fondo casi plano- en el lado oculto de la Luna. Tal vez seas esta la razón por la que todavía la obra de Garavito Armero no sea visible para sus compatriotas.

Concepciones alternativas sobre Astronomía de profesorado español en formación

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María-Mercedes Varela-Losada

2015-12-01

Full Text Available ResumenEl proceso de enseñanza y aprendizaje de la Astronomía parece entrañar importantes dificultades, particularmente propiciando la generación de concepciones alternativas, como han mostrado numerosas investigaciones procedentes de diferentes contextos. El objetivo de este estudio es indagar sobre concepciones alternativas de profesorado en formación relacionadas con aspectos astronómicos, investigando si en el marco español aparecen los mismos esquemas alternativos que en otros contextos. Los resultados ponen en evidencia que el alumnado mencionado posee un gran número de concepciones alternativas sobre astronomía básica y que estas son similares a las encontradas en otros países.

`Site Testing' en la Puna de Atacama

Science.gov (United States)

Recabarren, P.; Mosconi, M.

We present a report of the activities developed by the IATE group from the Observatorio Astronómico de Córdoba and astronomers from the Pontificia Universidad Católica de Chile, from 14 till 22. of April of 2000. We have made seeing and meteorological measurements and a topographical prospecting in order to characterize the environmental conditions in Cerro Toco (5574m), in the region of the Puna de Atacama. The seeing measurements were made with a DIMM (Differential Image Motin Monitor) camera. The seeing measurements during 20. and 21. of April gave an average value of 0.85 arc seconds. We think that more places in the region should be studied.

Deciphering the embedded wave in Saturn's Maxwell ringlet

Science.gov (United States)

French, Richard G.; Nicholson, Philip D.; Hedman, Mathew M.; Hahn, Joseph M.; McGhee-French, Colleen A.; Colwell, Joshua E.; Marouf, Essam A.; Rappaport, Nicole J.

2016-11-01

The eccentric Maxwell ringlet in Saturn's C ring is home to a prominent wavelike structure that varies strongly and systematically with true anomaly, as revealed by nearly a decade of high-SNR Cassini occultation observations. Using a simple linear "accordion" model to compensate for the compression and expansion of the ringlet and the wave, we derive a mean optical depth profile for the ringlet and a set of rescaled, background-subtracted radial wave profiles. We use wavelet analysis to identify the wave as a 2-armed trailing spiral, consistent with a density wave driven by an m = 2 outer Lindblad resonance (OLR), with a pattern speed Ωp = 1769.17° d-1 and a corresponding resonance radius ares = 87530.0 km. Estimates of the surface mass density of the Maxwell ringlet range from a mean value of 11g cm-2 derived from the self-gravity model to 5 - 12gcm-2 , as inferred from the wave's phase profile and a theoretical dispersion relation. The corresponding opacity is about 0.12 cm2 g-1, comparable to several plateaus in the outer C ring (Hedman, M.N., Nicholson, P.D. [2014]. Mont. Not. Roy. Astron. Soc. 444, 1369-1388). A linear density wave model using the derived wave phase profile nicely matches the wave's amplitude, wavelength, and phase in most of our observations, confirming the accuracy of the pattern speed and demonstrating the wave's coherence over a period of 8 years. However, the linear model fails to reproduce the narrow, spike-like structures that are prominent in the observed optical depth profiles. Using a symplectic N-body streamline-based dynamical code (Hahn, J.M., Spitale, J.N. [2013]. Astrophys. J. 772, 122), we simulate analogs of the Maxwell ringlet, modeled as an eccentric ringlet with an embedded wave driven by a fictitious satellite with an OLR located within the ring. The simulations reproduce many of the features of the actual observations, including strongly asymmetric peaks and troughs in the inward-propagating density wave. We argue that

Astronomía gamma con telescopios Cherenkov: hacia un observatorio astronómico abierto a la comunidad

Science.gov (United States)

Rovero, A. C.

Gamma-ray astronomy is opening the way to a universe far more energetic than anyone could have imagined half a century ago. The understanding of the processes of nature which carry a large portion of the energy in the universe, has astrophysical and cosmological implications. The next gen- eration of Cherenkov telescopes, an order of magnitude more sensitive and with higher resolution than the current systems, will mean a significant step forward for ground-based gamma-ray astronomy. This paper presents the current status of this field as well as the next generation of telescopes in this energy range, which are being designed for the first international observa- tory open to the astronomical community. The Cherenkov Telescope Array project and the Argentine sites proposed for the southern observatory are described in this paper. FULL TEXT IN SPANISH

Comportamiento de la cromósfera solar en la línea H-alpha durante el ciclo 23

Science.gov (United States)

Davoli, D.; Aquilano, R.; Missio, H.

Using the instrumental of the Observatorio Astronómico Municipal de Rosario (OAMR), we analyze the solar chromospheric activity during an approximate period of 11 years. The instrument is a Carl Zeiss refractor telescope of 150 mm aperture and 2250 mm of focal distance with monochromatic filter in the H-alpha line. We take as proxy for the solar activity the area covered by chromospheric plages. Simultaneously, we determine the relative wolf number from observations of the solar photosphere. We describe our technique and the results obtained. We observe 2 maxima of solar activity in the years 2000 and 2001 respectively, and a later decrease of this activity with low average values starting around 2006 that corresponds to the end of cycle 23. FULL TEXT IN SPANISH

Detecting signatures of cosmological recombination and reionization in the cosmic radio background

Science.gov (United States)

Subrahmanyan, Ravi; Shankar Narayana Rao, Udaya; Sathyanarayana Rao, Mayuri; Singh, Saurabh

2015-08-01

Evolution of the baryons during the Epochs of cosmological Recombination and Reionization has left traces in the cosmic radio background in the form of spectral distortions (Sunyaev & Chluba 2008 Astron. Nachrichten, 330, 657; Pritchard & Loeb 2012 Rep Prog Phys 75(8):086901). The spectral signature depends on the evolution in the ionization state in hydrogen and helium and on the spin temperature of hydrogen. These probe the physics of energy release beyond the last scattering surface at redshifts exceeding 1090 and the nature of the first sources and gas evolution down to redshift about 6. The spectral distortions are sensitive to the nature of the first stars, ultra-dwarf galaxies, accreting compact objects, and the evolving ambient radiation field: X-rays and UV from the first sources. Detection of the all-sky or global spectral distortions in the radio background is hence a probe of cosmological recombination and reionization.We present new spectral radiometers that we have purpose designed for precision measurements of spectral distortions at radio wavelengths. New antenna elements include frequency independent and electrically small fat-dipole (Raghunathan et al. 2013 IEEE TAP, 61, 3411) and monopole designs. Receiver configurations have been devised that are self-calibratable (Patra et al. 2013 Expt Astron, 36, 319) so that switching of signal paths and of calibration noise sources provide real time calibration for systematics and receiver noise. Observing strategies (Patra et al. arXiv:1412.7762) and analysis methods (Satyanarayana Rao et al. arXiv:1501.07191) have been evolved that are capable of discriminating between the cosmological signals and the substantially brighter foregrounds. We have also demonstrated the value of system designs that exploit advantages of interferometer detection (Mahesh et al. arXiv:1406.2585) of global spectral distortions.Finally we discuss how the Square Kilometer Array stations may be outfitted with precision spectral

Polarimetric survey of main-belt asteroids. V. The unusual polarimetric behavior of V-type asteroids

Science.gov (United States)

Gil-Hutton, R.; López-Sisterna, C.; Calandra, M. F.

2017-03-01

Aims: We present the results of a polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. Methods: The data were obtained using the CASPROF and CASPOL polarimeters at the 2.15 m telescope. The CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation and CASPOL is a polarimeter based on a CCD detector, which allows us to observe fainter objects with better signal-to-noise ratio. Results: The survey began in 1995 and data on a large sample of asteroids were obtained until 2012. A second period began in 2013 using a polarimeter with a more sensitive detector in order to study small asteroids, families, and special taxonomic groups. We obtained 55 polarimetric measurements for 28 V-type main belt asteroids, all of them polarimetrically observed for the first time. The data obtained in this survey let us find polarimetric parameters for (1459) Magnya and for a group of 11 small V-type objects with similar polarimetric behavior. These polarization curves are unusual since they show a shallow minimum and a small inversion angle in comparison with (4) Vesta, although they have a steeper slope at α0. This polarimetric behavior could be explained by differences in the regoliths of these asteroids. The observations of (2579) Spartacus, and perhaps also (3944) Halliday, indicate a inversion angle larger than 24-25°. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.

Los modelos etnomatemáticos de representación cosmogónica en los pueblos indígenas Americanos

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Alejandro Jaén Rojas

2015-01-01

Full Text Available El propósito en este artículo es el de mostrar y analizar diversas formas de representación que utilizaron o, utilizan aun los indígenas americanos de diversas culturas. Algunas formas de representación, consideradas comúnmente como motivos decorativos, parecen responder a un sistema lógico muy preciso, que podría tener el propósito central de expresar y guardar conocimientos cosmogónicos. Para tal efecto, los indígenas de diversos pueblos, recurrieron a estructuras y formas de representación matemáticas, que les permitían guardar conocimientos astronómicos, calendáricos, de las cosechas, censos, entre otros, y luego expresarlos como mitos, integrados dentro de su espacio cosmogónico. Resulta sorprendente ver como algunas formas de representación, como las grecas escalonadas, pasan de una cultura a otra, desde Alaska hasta la Patagonia, en lo que parecen ser modelos de representación, que se difundieron muchos siglos antes de la llegada de los españoles a América. La razón por la cual, estos modelos de representación se generalizan, a lo largo de distancias enormes y entre los pueblos más diversos, es porque son conocimientos que surgen ligados a los tejidos. Hasta donde sabemos, casi la totalidad de los indígenas tejían en algodón o diversas fibras, con lo cual, una vez iniciado el proceso de guardar informaciones todos ellos contaron con una base simple y sólida para fortalecer el proceso de recopilación de datos, y guardarlos con precisión. Muchos son los ejemplos de cómputos realizados con mecates, al estilo de los quipus suramericanos. En el arte de tejer surgen conocimientos matemáticos que les permitieron guardar informaciones muy variadas: calendáricas, astronómicas, culturales, entre otras, que luego eran expresadas como una visión de mundo, una cosmogonía.

Russian Virtual Observatory: Data Sources

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Malkov O.

2016-03-01

Full Text Available The purpose of this review is to analyze main directions of creation and functioning of major data sources developed by Russian astronomers or with their participation and to compare them with the worldwide trends in these fields. We discuss astronomical space missions of the past, present, and future (Astron, INTEGRAL, WSO-UV, Spectrum Roentgen Gamma, Lyra-B, high-quality photometric atlases and catalogues, and spectroscopic data sources, primarily VALD and the global VAMDC framework for the maintenance and distribution of atomic and molecular data. We describe collection, analysis, and dissemination of astronomical data on minor bodies of the Solar System and on variable stars. Also described is the project joining data for all observational types of binary and multiple stars, Binary star DataBase (BDB.

Angular Momentum Transport in Turbulent Flow between Independently Rotating Cylinders

International Nuclear Information System (INIS)

Paoletti, M. S.; Lathrop, D. P.

2011-01-01

We present measurements of the angular momentum flux (torque) in Taylor-Couette flow of water between independently rotating cylinders for all regions of the (Ω 1 , Ω 2 ) parameter space at high Reynolds numbers, where Ω 1 (Ω 2 ) is the inner (outer) cylinder angular velocity. We find that the Rossby number Ro=(Ω 1 -Ω 2 )/Ω 2 fully determines the state and torque G as compared to G(Ro=∞)≡G ∞ . The ratio G/G ∞ is a linear function of Ro -1 in four sections of the parameter space. For flows with radially increasing angular momentum, our measured torques greatly exceed those of previous experiments [Ji et al., Nature (London), 444, 343 (2006)], but agree with the analysis of Richard and Zahn [Astron. Astrophys. 347, 734 (1999)].

THE POPULARIZATION OF ASTRONOMY IN THE TEACHING OF GEOGRAPHY: an experience in the middle and high school

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Márcio Balbino Cavalcante

2012-12-01

Full Text Available It is a very old man's concern to know the mysteries of the universe. Geography is defined as the study of the relationship between space and society, is, par excellence, discipline and interdisciplinary teaching should focus on various aspects of society and nature. The present study was aimed to popularize astronomy in Geography lessons of elementary and secondary public and private schools of the municipality the of Passa e Fica/RN, with reference to the achievement of the Olympiad of Astronomy and Astronautics - OBA, sponsored by the Institute Physics - UERJ in partnership with the Sociedade Astronômica Brasileira (SAB and the Agência Espacial Brasileira (AEB. The achievement of this Article, the following steps were undertaken: literature search and mapping, field survey;-class ride to Centro de Lançamento de Foguetes da Barreira do Inferno, em Natal/RN; lectures, telescopic observations, workshops for carrying out activities practices such as the sundial, replica rocket, compass; classroom discussion of the data collected, the material made with exposure and mobilization involving the school community and the Government. According to the results, interdisciplinary work between geography and astronomy produced a privileged space for the construction and popularization of scientific knowledge founded on the reality experienced by the student, always with a critical and constructive, which often is ignored in school work. RESUMO: É muito antiga a preocupação do homem em conhecer os mistérios do universo. A Geografia é definida como o estudo das relações entre o espaço e as sociedades, é, por excelência, uma disciplina interdisciplinar e seu ensino deve enfocar diversos aspectos da sociedade e da natureza. O presente trabalho teve objetivo de popularizar a Astronomia nas aulas de Geografia dos ensinos fundamental e médio das escolas públicas e particulares do município de Passa e Fica/RN; tendo como referência a realiza

Spectrophotometric intracutaneous analysis for differential diagnosis of pigmented skin lesions

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Е. V. Filonenko

2013-01-01

Full Text Available The non-invasive diagnosis of pigmented skin lesions by spectrophotometric intracutaneous analysis (SIA-scopy using device for dermatoscopy (SIAscope V by Astron Clinica, Ltd was approved in P.A.Herzen Moscow Cancer Research Institute. The method is based on analysis of light interaction with wavelength of 440–960 nm anf human skin, which is recorded by change of image on scan. The comparative analysis of SIA-scopy and histological data in 327 pigmented skin lesions in 147 patients showed, that SIA had high diagnostic efficiency for cutaneous melanoma: the sensitivity was 96%, specifity – 94%, diagnostic accuracy – 94%. For study of malignant potential of pigmented lesions by SIA-scopy the most informative capacity was obtained for assessment of melanin in papillary dermis, status of blood vessels and collagen fibres (SIA-scans 3, 4, 5.

RADIOASTRON OBSERVATIONS OF THE QUASAR 3C273: A CHALLENGE TO THE BRIGHTNESS TEMPERATURE LIMIT

Energy Technology Data Exchange (ETDEWEB)

Kovalev, Y. Y.; Kardashev, N. S.; Voitsik, P. A.; Kovalev, Yu. A.; Lisakov, M. M.; Sokolovsky, K. V. [Astro Space Center of Lebedev Physical Institute, Profsoyuznaya 84/32, 117997 Moscow (Russian Federation); Kellermann, K. I. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States); Lobanov, A. P.; Zensus, J. A.; Anderson, J. M.; Bach, U.; Kraus, A. [Max-Planck-Institute for Radio Astronomy, Auf dem Hügel 69, D-53121 (Germany); Johnson, M. D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gurvits, L. I. [Joint Institute for VLBI ERIC, P.O. Box 2, 7990 AA Dwingeloo (Netherlands); Jauncey, D. L. [CSIRO Astronomy and Space Sciences, Epping, NSW 1710 (Australia); Ghigo, F. [National Radio Astronomy Observatory, Rt. 28/92, Green Bank, WV 24944-0002 (United States); Ghosh, T.; Salter, C. J. [Arecibo Observatory, NAIC, HC3 Box 53995, Arecibo, Puerto Rico, PR 00612 (United States); Petrov, L. Yu. [Astrogeo Center, 7312 Sportsman Drive, Falls Church, VA 22043 (United States); Romney, J. D. [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801-0387 (United States)

2016-03-20

Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of 10{sup 11.5} K. Relativistic boosting can increase its observed value, but apparent brightness temperatures much in excess of 10{sup 13} K are inaccessible using ground-based very long baseline interferometry (VLBI) at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as small as 26 μas (2.7 light months) and brightness temperature in excess of 10{sup 13} K. These measurements challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive black holes and require a much higher Doppler factor than what is determined from jet apparent kinematics.

New International Agreements About Space Techniques Among Argentina, China and France

Science.gov (United States)

Pacheco, A. M.; Podestá, R.; Actis, E.; Adarvez, S.; Quinteros, J.; Li, J.; Saunier, J.; Podestá, F.; Ramos, F.; Aguilera, J.; Sosa, G.; Hauser, D.

2018-01-01

The International Earth Rotation and Reference Systems (IERS) is in charge of defining and materializing celestial reference systems (ICRS - ICRF) and terrestrial reference systems (ITRS - ITRF). In order to perform this task it uses data from the following techniques: Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite System (GNSS) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). Nowadays, the Observatorio Astronómico Félix Aguilar (OAFA) has two instruments with these advanced techniques: SLR and a permanent GNSS station. In the nearby future a 40 m diameter radio telescope will be available that will be operated in VLBI mode along with a DORIS buoy which will be co-localized with a SLR telescope and GNSS antennas. In this way OAFA will become a zero station, first class, of the ITRF 2014 frame.

SUPERFAST THERMALIZATION OF PLASMA

Science.gov (United States)

Chang, C.C.

1962-06-12

A method is given for the superfast thermalization of plasma by shock conversion of the kinetic energy stored in rotating plasma rings or plasmoids colliding at near supersonic speeds in a containment field to heat energy in the resultant confined plasma mass. The method includes means for generating rotating plasmoids at the opposite ends of a Pyrotron or Astron containment field. The plasmoids are magnetically accelerated towards each other into the opposite ends of time containment field. During acceleration of the plasmoids toward the center of the containment field, the intensity of the field is sequentially increased to adiabatically compress the plasmoids and increase the plasma energy. The plasmoids hence collide with a violent shock at the eenter of the containment field, causing the substantial kinetic energy stored in the plasmoids to be converted to heat in the resultant plasma mass. (AEC)

Cálculo da latitude e direção dos pólos pela projeção da trajetória circular das estrelas

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Julierme Wagner da Penha

2009-08-01

Full Text Available Muitas vezes, a gente olha para o céu e admira a beleza das estrelas, até contamos, mas nem imaginamos que podemos estudar estes astros luminosos, bem como nos localizarmos por meio deles, assim como faziam os navegadores do passado. Na verdade, esta atividade é uma das mais antigas estudadas pelo homem. Este trabalho mostra um método novo e simplificado para determinar tanto a coordenada da latitude astronômica e a direção do Pólo Norte ou do Sul, por meio da observação de estrelas. A idéia é que esse método possa ser utilizado sem a prévia informação do anuário astronômico, bem como sem a prévia escolha do astro a ser observado. O método tem originado do princípio de que, caso tivéssemos um astro localizado exatamente na posição do pólo sul, seria suficiente posicionar o instrumento e visar o astro para determinar a latitude (altura do pólo elevado, independentemente do horário de observação, pois, o mesmo não teria movimento aparente algum. Portanto, este método sugere que, após a escolha do astro, o mesmo deverá ser observado, no mínimo em três posições diferentes. Projetando estas trajetórias em um plano perpendicular ao eixo terrestre rotação da Terra no pólo, tem-se várias circunferências concêntricas. O centro desta circunferência seria a posição exata do pólo. Determinando o centro da circunferência determina-se também a latitude e a direção dos pólos. Pode-se concluir que o método apresentado é viável para determinação da latitude e da direção dos pólos, pois os resultados encontrados foram satisfatórios.

Proving the Orbits of the Galilean Moons Through Astrophotography. (Spanish Title: Comprobando Las Órbitas de Las Lunas Galileanas a Través de la Astrofotografía.) Evidenciando as Órbitas das Luas Galileanas Atravéd da Astrofotografia

Science.gov (United States)

Iachel, Gustavo

2009-12-01

An activity related to the observation of the Galilean moons and to amateur astrophotography is presented in this work. Through the reading of excerpts of the book Sidereus Nuncius (Sidereal Messenger), by Galileo, it is possible to trace a methodology to observe the planet and its natural satellites and, with the aid of the astrophotography, to analyze the field recordings. Moreover, it is possible to compare the images obtained after plotting the relative positions of these moons to prove their orbits. This activity can be conducted by teachers, students and amateur astronomers, in order to develop their capabilities of observation of astronomical phenomena. Se presenta en este trabajo una actividad relacionada a la observación de las lunas Galileanas y a la astrofotografía amateur. A través de la lectura de tramos de la obra Sidereus Nuncius (El Mensajero Sideral) de Galileo, es posible trazar una metodología para la observación del planeta y de sus satélites naturales y, con el auxilio de la astrofotografía, analizar las anotaciones de campo. Además, es posible comparar las imágenes obtenidas con el gráfico de las posiciones relativas de estas lunas para comprobar sus órbitas. Esa actividad puede ser realizada por maestros, estudiantes y astrónomos amateurs, de forma a desarrollar sus capacidades de observación de los fenómenos astronómicos. Uma atividade relacionada à observação das luas Galileanas e à astrofotografia amadora é apresentada neste trabalho. Através da leitura de trechos da obra Sidereus Nuncius (Mensageiro Sideral), de Galileu, é possível traçar uma metodologia para a observação do planeta e de seus satélites naturais e, com o auxílio da astrofotografia, analisar as anotações de campo. Além disso, é possível comparar as imagens obtidas com o gráfico das posições relativas destas luas para evidenciar suas órbitas. Essa atividade pode ser realizada por professores, estudantes e astrônomos amadores, de forma a

Astronomy Teaching and Teachers Continuing Education: the Interdisciplinarity during a Total Lunar Eclipse. (Spanish Title: Enseñanza de la Astronomía y la Formación Continua de Profesores: la Interdisciplinariedad Durante un Eclipse Total de Luna.) Educação EM Astronomia E Formação Continuada de Professores: a Interdisciplinaridade Durante um Eclipse Lunar TOTAL

Science.gov (United States)

Langhi, Rodolfo

2009-07-01

This paper describes how 67 teachers from 23 cities, could awaken, in students, the scientific interest, using a natural astronomical phenomenon: a total lunar eclipse. Before and after of eclipse, meetings for continuing education were characterized by interdisciplinarity of astronomy and the importance of these observations. Working groups were formed by teachers and students, who organized the survey data, mobilizing the people in their cities. The results point ways about how to provide the scientific culture and the motivation to learn science in students, using approaches between the following communities: scientific, amateur and school. En este artículo se describe cómo 67 profesores de 23 ciudades, despertó el interés científico en los estudiantes mediante un fenómeno astronómico: un eclipse total de Luna. Antes y después del eclipse, reuniones para la formación continua se centraron en la interdisciplinariedad de la astronomía, y la importancia de las observaciones de este tipo de fenómeno. Profesores y estudiantes formaron grupos de trabajo para investigar datos durante el eclipse, con el participación de la comunidad en sus ciudades. Los resultados apuntan a las opciones que conducen a la cultura científica y la motivación para aprender la ciencia, utilizando las relaciones de los siguientes grupos: científicos, aficionados y la escuela. Este texto relata como 67 professores, provenientes de 23 cidades, puderam despertar, nos alunos, o interesse científico utilizando um fenômeno natural astronômico: um eclipse lunar total. O evento foi precedido e procedido por encontros de formação continuada, onde se caracterizou a interdisciplinaridade da astronomia e a importância das observações de fenômenos como estes. Grupos de trabalho foram formados por professores e alunos, que se organizaram para o levantamento conjunto de dados durante o fenômeno, além do envolvimento da comunidade em suas respectivas cidades. Os resultados apontam

Ensino de astronomia e óptica: é possível fazê-lo de forma contextualizada no nível médio?

Science.gov (United States)

Sobrinho, A. A.; Jafelice, L. C.

2003-08-01

Discutimos nossa participação em um curso de treinamento para professores de diversas disciplinas do ensino médio. Nossa preocupação básica foi desenvolver instrumentos educacionais adequados para levar à sala de aula, nesse nível de ensino, de forma contextualizada, questionamentos freqüentes dos alunos sobre astronomia e sua relação com tecnologia e sociedade. Encaminhamos questões como: a evolução da astronomia, suas relações com outros ramos do conhecimento humano e conseqüentes aplicações; avanços na tecnologia dos instrumentos ópticos versus a importância da observação do céu a olho nu; a relação entre olho humano, luneta e telescópio; e desenvolvimento da tecnologia espacial e sua influência em nosso cotidiano. Objetivamos com isto fazer um resgate histórico e pedagógico das aplicações e observações do céu no cenário escolar, destacando a relação entre eventos astronômicos, olho humano, instrumentos mediadores e suas contextualizações históricas e sociais. Produtos desta abordagem foram o desenvolvimento e a adaptação de práticas e materiais instrucionais diversos (e.g., "espelhos" de isopor e "raios luminosos" de bolinhas de gude; montagens envolvendo velas, lasers, lentes e espelhos; desmonte e análise de peças de um telescópio; etc.). Além disto, como outro resultado deste trabalho, elaboramos textos sobre história da astronomia e da óptica para atividades em classe. Com estas ações visamos facilitar a concretização de conceitos físicos envolvidos, exemplificar um ensino contextualizado e interdisciplinar motivado por temas astronômicos e favorecer que práticas e discussões feitas com os treinandos possam ser transpostas para a sala de aula. A reação dos professores às práticas propostas foi bastante positiva. Todos esses aspectos são discutidos em detalhe neste trabalho. (PPGECNM/UFRN; PRONEX/FINEP; NUPA/USP; Temáticos/FAPESP)

Supernovas, faros en el universo: medición de la distancia a ASASSN-15hx

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Ramona Núñez López

2016-12-01

Full Text Available Difícil pensar en un evento astronómico tan relevante y polifacético como la gigantesca explosión de supernova, que en breves segundos destruye su estrella, creando un gran número de elementos pesados. El inmenso brillo de las supernovas permite observarlas a enormes distancias, para así obtener información cosmológica. En este trabajo abordamos en general el tema de supernovas, enfocándonos luego al estudio de la supernova de tipo Ia ASASSN-15hx. Presentamos las observaciones realizadas en diferentes filtros y mostramos un método basado en el ancho de su curva de luz para estimar su distancia y corrimiento al rojo. Los valores obtenidos coinciden con información encontrada en la literatura y las incertidumbres obtenidas están dentro del rango de las encontradas con otros métodos.

La gravedad en Bruno, Kleper y Newton. la distribución de la materia y sus implicaciones cosmológicas

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M. Diego Pintado

2016-10-01

Full Text Available En este trabajo se describe en modo sucinto el papel fundamental y determinante del problema de la gravitación universal en la historia de la cosmología moderna, indagándose así mismo los factores que le dieron origen, principalmente la proposición de la formulación de la ley de gravedad, sus antecedentes, y a su vez se repasan los problemas astrofísicos, astronómicos y filosóficos de este nuevo esquema cosmológico. El esquema de esta monografía traza un breve examen epistemológico, luego un repaso por el origen y gestación del concepto de gravitación universal, y finalmente un análisis del desarrollo de la cosmología moderna, o newtoniana, entorno a los problemas implicados por la ley de gravedad.

THEORY AND SIMULATIONS OF REFRACTIVE SUBSTRUCTURE IN RESOLVED SCATTER-BROADENED IMAGES

Energy Technology Data Exchange (ETDEWEB)

Johnson, Michael D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gwinn, Carl R., E-mail: mjohnson@cfa.harvard.edu [Department of Physics, University of California, Santa Barbara, CA 93106 (United States)

2015-06-01

At radio wavelengths, scattering in the interstellar medium distorts the appearance of astronomical sources. Averaged over a scattering ensemble, the result is a blurred image of the source. However, Narayan and Goodman and Goodman and Narayan showed that for an incomplete average, scattering introduces refractive substructure in the image of a point source that is both persistent and wideband. We show that this substructure is quenched but not smoothed by an extended source. As a result, when the scatter-broadening is comparable to or exceeds the unscattered source size, the scattering can introduce spurious compact features into images. In addition, we derive efficient strategies to numerically compute realistic scattered images, and we present characteristic examples from simulations. Our results show that refractive substructure is an important consideration for ongoing missions at the highest angular resolutions, and we discuss specific implications for RadioAstron and the Event Horizon Telescope.

A photometric survey of Near-Earth Objects in support of the NEOShield-2 project

Science.gov (United States)

Ieva, S.; Dotto, E.; Mazzotta Epifani, E.; Perna, D.; Barucci, M. A.; Di Paola, A.; Micheli, M.; Perozzi, E.; Speziali, R.; Lazzarin, M.; Bertini, I.; Giunta, A.; Lazzaro, D.; Arcoverde, P.

2017-09-01

More than 85% of the 16,000 NEOs discovered up to now lack a physical characterization. The study of their physical properties is essential to define a proper mitigation scenario. One of the main aims of the NEOShield-2 project (2015-2017), financed by the European Community in the framework of the Horizon 2020 program, is therefore to retrieve physical properties of a wide number of NEOs, in order to design impact mitigation missions and assess the consequences of an impact on Earth. We present the results obtained during a 2-year Long-Term Program at the Telescopio Nazionale Galileo (TNG, La Palma, Spain), where we carried out BVRI photometry of about 150 NEOs, and the analysis of the phase curves obtained at the Campo Imperatore telescope (L'Aquila, Italy) and the Observatório Astronômico do Sertão de Itaparica (Nova Itacuruba, Brazil).

Visits to La Plata Observatory

Science.gov (United States)

Feinstein, A.

1985-03-01

La Plata Observatory will welcome visitors to ESO-La Silla that are willing to make a stop at Buenos Aires on their trip to Chile or on their way back. There is a nice guesthouse at the Observatory that can be used, for a couple of days or so, by astronomers interested in visiting the Observatory and delivering talks on their research work to the Argentine colleagues. No payments can, however, be made at present. La Plata is at 60 km from Buenos Aires. In the same area lie the Instituto de Astronomia y Fisica dei Espacio (IAFE), in Buenos Aires proper, and the Instituto Argentino de Radioastronomia (IAR). about 40 km from Buenos Aires on the way to La Plata. Those interested should contacl: Sr Decano Prof. Cesar A. Mondinalli, or Dr Alejandro Feinstein, Observatorio Astron6mico, Paseo dei Bosque, 1900 La Plata, Argentina. Telex: 31216 CESLA AR.

Distribución espacial de órbitas con diferentes grados de caoticidad en modelos autoconsistentes de satélites galácticos

Science.gov (United States)

Muzzio, J. C.; Mosquera, M.

En trabajos anteriores (Carpintero et al., Cel. Mech. Dynam. Astron. 85, 247, 2003), mostramos que las órbitas caóticas son muy importantes en los satélites galácticos. Sin embargo, los únicos modelos autoconsistentes de los que se disponía para ellos eran los de Heggie-Ramamani, cuya función de distribución depende sólo de la energía por lo que no mostraban diferencias entre las distribuciones de sus órbitas regulares y caóticas. Ahora, mediante una aproximación cuadrupolar, hemos logrado construir modelos autoconsistentes de satélites galácticos con distribuciones de velocidades anisotrópicas (lo que indica que sus funciones de distribución no dependen sólo de la energía) y hemos logrado revelar las diferencias entre las estructuras espaciales de las órbitas de distinta caoticidad.

Mesa redonda: Argentina en proyectos globales de investigaciones espaciales y astronómicas. Astronomía óptica en Argentina

Science.gov (United States)

Folatelli, G.

2016-08-01

This is a brief summary of the current status of observational astronomy in the optical range in Argentina, as seen by the author. This roundtable presentation aimed at setting off the discussion within the community about the issue of observational facilities and its posible solutions.

Peculiar Supernovae

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Milisavljevic, Dan; Margutti, Raffaella

2018-06-01

What makes a supernova truly "peculiar?" In this review we attempt to address this question by tracing the history of the use of "peculiar" as a descriptor of non-standard supernovae back to the original binary spectroscopic classification of Type I vs. Type II proposed by Minkowski (Publ. Astron. Soc. Pac., 53:224, 1941). A handful of noteworthy examples are highlighted to illustrate a general theme: classes of supernovae that were once thought to be peculiar are later seen as logical branches of standard events. This is not always the case, however, and we discuss ASASSN-15lh as an example of a transient with an origin that remains contentious. We remark on how late-time observations at all wavelengths (radio-through-X-ray) that probe 1) the kinematic and chemical properties of the supernova ejecta and 2) the progenitor star system's mass loss in the terminal phases preceding the explosion, have often been critical in understanding the nature of seemingly unusual events.

Introduction

Science.gov (United States)

Cheng, K. S.; Romero, Gustavo E.

In the last 15 years, gamma-ray astronomy has evolved from a promis-ing but rather exotic branch of astronomical science to become a mature field of research with its own well-defined referents: cosmic gamma-ray sources. These sources include some of the most extraordinary objects known to human beings: pulsars, active galactic nuclei, accreting black holes, supernova remnants, and gamma-ray bursts. A significant com-ponent of our current knowledge of such objects is the direct result of astronomical measurements of the high-energy photons they produce. Satellite-borne instruments that can detect gamma-rays in the Earth's orbit or in deep space and atmospheric air shower detectors that re-construct the energy and direction of high-energy photons through the Cherenkov light generated in particle showers produced in the Earth's atmosphere have been the basic exploratory tools of gamma-ray astron-omy. For many years, however, cosmic gamma-ray sources defied all attempts at their detection.

Injection, compression and stability of intense ion-rings

International Nuclear Information System (INIS)

Sudan, R.N.

1975-01-01

Recent advances in pulsed high power ion beam technology make possible the creation of intense ion-rings with strong self-magnetic fields by single pulse injection. Such ion rings have several uses in controlled fusion e.g., to produce a min parallel B parallel magnetic geometry with a mirror ratio much higher than is possible with external conductors. For even stronger ion rings a min parallel B parallel with closed lines of force (ASTRON type) can be created. For this purpose, since the ion energies required are much higher than are available from high power sources, magnetic compression can be utilized to increase the ion energy. The success of this scheme depends critically on the stability of the ion ring. The low frequency perturbations of the ring-plasma system is examined by means of a generalization of the energy principle which established sufficient conditions for stability. The high-frequency micro-instabilities and their nonlinear consequences are discussed in terms of conventional techniques

Relativistic viscous hydrodynamics for heavy-ion collisions with ECHO-QGP

CERN Document Server

Del Zanna, L; Inghirami, G; Rolando, V; Beraudo, A; De Pace, A; Pagliara, G; Drago, A; Becattini, F

2013-01-01

We present ECHO-QGP, a numerical code for $(3+1)$-dimensional relativistic viscous hydrodynamics designed for the modeling of the space-time evolution of the matter created in high energy nuclear collisions. The code has been built on top of the \\emph{Eulerian Conservative High-Order} astrophysical code for general relativistic magneto-hydrodynamics [\\emph{Del Zanna et al., Astron. Astrophys. 473, 11, 2007}] and here it has been upgraded to handle the physics of the Quark-Gluon Plasma. ECHO-QGP features second-order treatment of causal relativistic viscosity effects in both Minkowskian or Bjorken coordinates; partial or complete chemical equilibrium of hadronic species before kinetic freeze-out; initial conditions based on the optical Glauber model, including a Monte-Carlo routine for event-by-event fluctuating initial conditions; a freeze-out procedure based on the Cooper-Frye prescription. The code is extensively validated against several test problems and results always appear accurate, as guaranteed by th...

SLR and GPS spatial techniques in ITRF. Argentine results.

Science.gov (United States)

Actis, Eloy Vicente; Huang, Dongping; Márquez, Raúl; Adarvez, Sonia; Flores, Matías; Brizuela, Diego; Nievas, Jesica; Podestá, Ricardo; Pacheco, Ana M.; Rojas, Hernán Alvis; Yin, Zhiqiang; Li, Jinzeng; Han, Yanben; Liu, Weidong; Wang, Rui

2012-08-01

Along the late 30 years spatial geodetic techniques enable us to measure horizontal and vertical deformations of the Earth’s surface with a very high precision. Performing this task we made Satellite Laser Ranging (SLR), and Global Positioning System (GPS) observations in South America ILRS 7406 Station placed at Observatorio Astronómico Félix Aguilar (OAFA) in San Juan, Argentina, accomplishing a Cooperation Agreement between CAS - NAOC and OAFA - UNSJ. Trough LAGEOS II Satellite observations we obtain rectangular coordinates of San Juan ILRS Station in the Terrestrial Reference Frame (ITR 2000), standing out that Argentine Station data were included in the late arrangements ITRF given by International Earth Rotation and Reference System Service (IERS). Spatial and temporary variations of the epoch 2010 - 2011 were evaluated finding out remarkable displacements, of about a half meter, related with seismic events on the region. We confirm these deformations by means of GP S determinations referred to Permanent GPS Station placed nearby the SLR Station.

El círculo meridiano automático de San Fernando - San Juan. Sus primeros pasos en el hemisferio sur

Science.gov (United States)

Mallamaci, C. C.; Muiños, J. L.; Gallego, M.; Pérez, J. A.; Marmolejo, L.; Navarro, J. L.; Sedeño, J.; Vallejos, M.; Belizón, F.

Se informa sobre el estado actual del Círculo Meridiano Automático de San Fernando-San Juan. El instrumento (Grubb-Parson, de 178mm de abertura y 2665 mm de distancia focal) es gemelo del que se encuentra en las Islas Canarias, y fue instalado durante los meses de julio y agosto de 1996 en la estación astronómica ``Dr. C.U.Cesco" (El Leoncito, Barreal), a unos 200 km de distancia de la ciudad de San Juan, merced a un Convenio de Cooperación Científica, firmado en 1994 entre el ROA (España) y el OAFA (Argentina). En la actualidad se está llevando a cabo un programa de prueba cuyos resultados preliminares muestran que el telescopio está en buenas condiciones para observar estrellas de hasta magnitud aproximada 14.5, con buenos errores de observación (<0.12" en ascensión recta y declinación).

Experimental investigation of the trapping and energy loss mechanisms of intense relativistic electron rings in hydrogen gas and plasma

International Nuclear Information System (INIS)

Smith, A.C. Jr.

1977-01-01

The results of an experimental study on the trapping and energy loss mechanisms of intense, relativistic electron rings confined in Astron-like magnetic field geometries are presented. The work is subdivided into four sections: gas trapping; average ring electron energetics; plasma trapping, and hollow-beam cusp-injection into gas and plasma. The mechanisms by which the injected beam coalesces into a current ring in the existing Cornell RECE-Berta facility are considered. To investigate the nature of ring electron energy loss mechanisms following completion of the trapping process, a diagnostic was developed utilizing multi-foil X-ray absorption spectroscopy to analyze the Bremsstrahlung generated by the electrons as they impinge upon a thin tungsten wire target suspended in the circulating current. Finally, a set of preliminary experimental results is presented in which an annular electron beam was passed through a coaxial, non-adiabatic magnetic cusp located at one end of a magnetic mirror well

Optical Design of COATLI: A Diffraction-Limited Visible Imager with Fast Guiding and Active Optics Correction

Science.gov (United States)

Fuentes-Fernández, J.; Cuevas, S.; Watson, A. M.

2018-04-01

We present the optical design of COATLI, a two channel visible imager for a comercial 50 cm robotic telescope. COATLI will deliver diffraction-limited images (approximately 0.3 arcsec FWHM) in the riz bands, inside a 4.2 arcmin field, and seeing limited images (approximately 0.6 arcsec FWHM) in the B and g bands, inside a 5 arcmin field, by means of a tip-tilt mirror for fast guiding, and a deformable mirror for active optics, both located on two optically transferred pupil planes. The optical design is based on two collimator-camera systems plus a pupil transfer relay, using achromatic doublets of CaF2 and S-FTM16 and one triplet of N-BK7 and CaF2. We discuss the effciency, tolerancing, thermal behavior and ghosts. COATLI will be installed at the Observatorio Astronómico Nacional in Sierra San Pedro Mártir, Baja California, Mexico, in 2018.

Studies of relativistic effects with radioastron space mission

Directory of Open Access Journals (Sweden)

Zakharov A.F.

2007-01-01

Full Text Available In the review we discuss possible studies of GR phenomena such as gravitational microlensing and shadow analysis with the forthcoming RadioAstron space mission. It is well-known that gravitational lensing is a powerful tool in the investigation of the distribution of matter, including that of dark matter (DM. Typical angular distances between images and typical time scales depend on the gravitational lens masses. For the microlensing, angular distances between images or typical astrometric shifts are about 10-5 – 10-6 as1. Such an angular resolution will be reached with the space-ground VLBI interferometer, Radioastron. The basic targets for microlensing searches should be bright point-like radio sources at cosmological distances. In this case, an analysis of their variability and a reliable determination of microlensing could lead to an estimation of their cosmological mass density. Moreover, one could not exclude the possibility that non-baryonic dark matter could also form microlenses if the corresponding optical depth were high enough. It is known that in gravitationally lensed systems, the probability (the optical depth to observe microlensing is relatively high; therefore, for example, such gravitationally lensed objects, like CLASS gravitational lens B1600+434, appear the most suitable to detect astrometric microlensing, since features of photometric microlensing have been detected in these objects. However, to directly resolve these images and to directly detect the apparent motion of the knots, the Radioastron sensitivity would have to be improved, since the estimated flux density is below the sensitivity threshold, alternatively, they may be observed by increasing the integration time, assuming that a radio source has a typical core - jet structure and microlensing phenomena are caused by the superluminal apparent motions of knots. In the case of a confirmation (or a disproval of claims about microlensing in grav­itational lens

Polarimetric survey of main-belt asteroids. VI. New results from the second epoch of the CASLEO survey

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Gil-Hutton, R.; García-Migani, E.

2017-11-01

Aims: We present the results of a polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry and to estimate the diversity in the polarimetric properties of asteroids that belong to different taxonomic classes. Methods: The data were obtained using the CASPOL polarimeter at the 2.15 m telescope. CASPOL is a polarimeter based on a CCD detector and a Savart plate. The survey began in 1995 and data on a large sample of asteroids were obtained until 2012. A second period began in 2013 using a polarimeter with a more sensitive detector in order to study small asteroids, families, and special taxonomic groups. Results: We present and analyze the unpublished results for 128 asteroids of different taxonomic types, 55 of them observed for the first time. The observational data allowed us to find probable new cases of Barbarian objects but also two D-type objects, (565) Marbachia and (1481) Tubingia, that seem to have phase-polarization curves with a large inversion angle. The data obtained combined with data from the literature enabled us to find phase-polarization curves for 121 objects of different taxonomic types and to study the relations between several polarimetric and physical parameters. Using an approximation for the phase-polarization curve we found the index of refraction of the surface material and the scatter separation distance for all the objects with known polarimetric parameters. We also found that the inversion angle is a function of the index of refraction of the surface, while the phase angle where the minimum of polarization is produced provides information about the distance between scatter particles or, to some extent, the porosity of the surface. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la

Tidal-Induced Internal Ocean Waves as an Explanation for Enceladus' Tiger Stripe Pattern and Hotspot Activity

Science.gov (United States)

Vermeersen, B. L. A.; Maas, L. R.; van Oers, S.; Rabitti, A.; Jara-Orue, H.

2014-12-01

One of the most peculiar features on Saturn moon Enceladus is its so-called tiger stripe pattern at the geologically active South Polar Terrain (SPT), as first observed in detail by the Cassini spacecraft early 2005. It is generally assumed that the four almost parallel surface lines that constitute this pattern are faults in the icy surface overlying a confined salty water reservoir. Indeed, later Cassini observations have shown that salty water jets originate from the tiger stripes [e.g., Hansen et al., Science, 311, 1422-1425, 2006; Postberg et al., Nature, 474, 620-622, 2011]. More recently, Porco et al. [Astron. J., 148:45, Sep. 2014] and Nimmo et al. [Astron. J., 148:46, Sep. 2014] have reported strong evidence that the geysers are not caused by frictional heating at the surface, but that geysers must originate deeper in Enceladus' interior. Tidal flexing models, like those of Hurford et al., Nature, 447, 292-294, 2007, give a good match for the brightness variations Cassini observes, but they seem to fail to reproduce the exact timing of plume brightening. Although jet activity is thus strongly connected to tidal forcing, another mechanism must be involved as well. Last year, we formulated the original idea [Vermeersen et al., AGU Fall Meeting 2013, abstract #P53B-1848] that the tiger stripe pattern is formed and maintained by induced, tidally and rotationally driven, wave-attractor motions in the ocean underneath the icy surface of the tiger-stripe region. Such wave-attractor motions are observed in water tank experiments in laboratories on Earth and in numerical experiments [Maas et al., Nature, 338, 557-561, 1997; Drijfhout and Maas, J. Phys. Oceanogr., 37, 2740-2763, 2007; Hazewinkel et al., Phys. Fluids, 22, 107102, 2010]. The latest observations by Porco et al. and Nimmo et al. seem to be in agreement with this tidal-induced wave attractor phenomenon, both with respect to tiger stripe pattern and with respect to timing of hotspot activity. However, in

The Teaching of Astronomy in Uruguay. (Spanish Title: La Enseñanza de la Astronomía en Uruguay.) O Ensino da Astronomia no Uruguai

Science.gov (United States)

Pintos Ganón, Reina; Fernández, Julio Angel

2008-07-01

We present in this work the development of astronomy in Uruguay since the colony times up to the present, stressing in particular those aspects related to the formal as well as informal teaching of astronomy. The first antecedents of astronomical studies in our country go back to the beginnings of the XVIIIth century related to the scientific expeditions from Europe coming to our shores. The teaching of astronomy was generalized at the high school level as soon as the end of the XIXth century, while itsintroduction at the university level happened much later, around the middle of the last century. We analyze the current situation of this subject, its problems, and some measures to strengthen its development. Se presenta en este trabajo el desarrollo de la astronomía en el Uruguay desde la época colonial hasta el presente, destacando en particular los aspectos vinculados a su enseñanza tanto formal como informal. Los primeros antecedentes de estudios astronómicos datan de la época colonial relacionados con las expediciones científicas del Viejo Mundo que llegaban a nuestras costas. La enseñanza de la Astronomía se generalizó en el ámbito de los estudios secundarios ya a fines del siglo XIX, mientras que en la Universidad su arribo fue mucho más tardío, a mediados del siglo pasado. Se analiza la situación actual de esta disciplina, sus problemas, y algunas medidas para fortalecer su desarrollo. Apresentamos, neste trabalho, o desenvolvimento da Astronomia no Uruguai desde a época colonial até o presente, destacando em particular os aspectos vinculados ao seu ensino tanto formal quanto informal. Os primeiros antecedentes de estudos astronômicos em nosso país datam da época colonial relacionados com as expedições científicas do Velho Mundo que chegavam às nossas costas. O ensino da Astronomia se generalizou no âmbito dos estudos secundários já no final do século XIX, enquanto que sua introdução na universidade foi muito mais tardia, em

Taxonomía de asteroides y cometas basada en los espectros de Lyapunov

Science.gov (United States)

Tancredi, G.; Motta, V.; Froeschlé, C.

Estudiaremos dos familias de objetos que sufren encuentros cercanos con planetas, a saber: la familia de cometas de Júpiter (JF) y los asteroides cercanos a la Tierra (NEAs). El movimiento de estos objetos es caótico en una escala de tiempo corta. Más aún, debido a los cambios erráticos en los elementos orbitales, la comparación de los valores actuales da poca información acerca de la posible vinculación dinámica entre los objetos de una misma familia. Calculamos una estimación finita de los Exponentes Característicos de Lyapunov (LCE), los llamamos Indicadores Característicos de Lyapunov (LCI) para ambas familias y analizamos las características del espacio de fase donde tiene lugar el movimiento de estos objetos. Integrando en un período suficientemente largo (e.g. 20000 años), encontramos que el LCI alcanza un valor cuasi-constante. La mayoría de los miembros de ambas familias muestran una concentración de los tiempos de Lyapunov (inverso del LCI) de alrededor de 50-100 años (Tancredi, 1995, Astron & Astrop., 299, 288). La concentración de los tiempos de Lyapunov es mayor para la familia de Júpiter que para los NEAs. Entre estos últimos, la menor dispersión se da para aquellos que cruzan la órbita de la Tierra. Se demostró que el espectro de los `indicadores locales' (Froeschlé et. al., 1990, Cel. Mec. 56, 307) o ``números de estiramiento'' (Voglis and Contopoulos, 1994, J. Phys. A 26, 4899) (relacionados con el LCI) son invariantes y nos dan una información más completa sobre el comportamiento caótico. Mediante la comparación de espectros discutimos la similitud entre los objetos de una misma familia y analizamos las diferentes posibles rutas al caos. Los espectros se clasifican mediante la comparación de los momentos de las distribuciones de los `números de estiramiento'. Aplicamos un método de agrupamiento jerárquico (Zappala et. al., 1990, Astron. J. 100, 2030) para identificar ``familias'' de espectros (grupos de espectros

Astronomy Teaching in Argentina in the 19th Century. (Spanish Title: La Enseñanza de la Astronomía en la Argentina del Siglo XIX.) O Ensino de Astronomia na Argentina no Século XIX

Science.gov (United States)

Norberto Cornejo, Jorge; Santilli, Haydée

2010-12-01

Sarmiento believed that Copernican astronomy was one of the critical scientific disciplines to the formation of a "modern" citizen. In this work, we shall study astronomical science from two points of view: from the scientific knowledge and the educational presentation of such knowledge. Our study will address in Argentina in 19th century, starting from the initiative of Bernardino Rivadavia in 1821, who founded an astronomic observatory at Buenos Aires, until the first activities of the observatories at Córdoba and La Plata. On both lines, scientific and educative, we shall analyze the influence of positivist ideas. We shall highlight epistemological differences between both observatories, Córdoba's based on French positivism and La Plata's based on German positivism. We shall also show the different attitude of both observatories towards education. We shall see the way in which positivist ideas had great relevance in the training of elementary school teachers. We shall also establish the relevant influence of the socio-historical context over the astronomical development, and show that astronomy was a fundamental social factor at Argentina history. Domingo F. Sarmiento consideraba que la astronomía copernicana era una de las disciplinas científicas fundamentales para la conformación de un ciudadano "moderno". En este trabajo estudiaremos la ciencia astronómica desde dos vertientes: la referida específicamente al conocimiento científico y aquella vinculada con la presentación educativa de dicho conocimiento. Nuestro estudio se desarrollará en Argentina durante el siglo XIX, desde la iniciativa de Bernardino Rivadavia en 1821, de establecer en Buenos Aires un observatorio astronómico, hasta las primeras actividades de los observatorios de Córdoba y de La Plata. En ambas vertientes, científica y educativa, analizaremos la influencia de las ideas positivistas. Resaltaremos las diferencias epistemológicas entre los dos observatorios, orientado el primero

Origin and Evolution of the Cometary Reservoirs

Science.gov (United States)

Dones, Luke; Brasser, Ramon; Kaib, Nathan; Rickman, Hans

2015-12-01

underwent a dynamical instability that led to a flood of comets and asteroids throughout the Solar System (Gomes et al. in Nature 435:466-469, 2005b). In this scenario, it is somewhat a matter of luck whether an icy planetesimal ends up in the Kuiper Belt or Oort Cloud (Brasser and Morbidelli in Icarus 225:40-49, 2013), as a Trojan asteroid (Morbidelli et al. in Nature 435:462-465, 2005; Nesvorný and Vokrouhlický in Astron. J. 137:5003-5011, 2009; Nesvorný et al. in Astrophys. J. 768:45, 2013), or as a distant "irregular" satellite of a giant planet (Nesvorný et al. in Astron. J. 133:1962-1976, 2007). Comets could even have been captured into the asteroid belt (Levison et al. in Nature 460:364-366, 2009). The remarkable finding of two "inner Oort Cloud" bodies, Sedna and 2012 VP_{113}, with perihelion distances of 76 and 81 AU, respectively (Brown et al. in Astrophys. J. 617:645-649, 2004; Trujillo and Sheppard in Nature 507:471-474, 2014), along with the discovery of other likely inner Oort Cloud bodies (Chen et al. in Astrophys. J. Lett. 775:8, 2013; Brasser and Schwamb in Mon. Not. R. Astron. Soc. 446:3788-3796, 2015), suggests that the Sun formed in a denser environment, i.e., in a star cluster (Brasser et al. in Icarus 184:59-82, 2006, 191:413-433, 2007, 217:1-19, 2012b; Kaib and Quinn in Icarus 197:221-238, 2008). The Sun may have orbited closer or further from the center of the Galaxy than it does now, with implications for the structure of the Oort Cloud (Kaib et al. in Icarus 215:491-507, 2011).

Las manifestaciones naturales como indicadores del calendario bosquesino

Directory of Open Access Journals (Sweden)

Napoleón Vela Mendoza

2014-09-01

Full Text Available Este artículo presenta un inventario del conocimiento de los bosquesinos (habitantes rurales de la selva amazónica que viven en el bosque y del bosque y sus aguas de la región de bajo río Ucayali (Amazonia peruana sobre las manifestaciones astronómicas, climatológicas, hidrográficas y biológicas con las que se ubican en el ritmo de las estaciones y orientan sus actividades en el medio natural. Las poblaciones bosquesinas distinguen dos periodos o épocas: la época de vaciante o de sol, y la época de creciente o de lluvias. Estas épocas a su vez se dividen en cuatro estaciones principales: Verano chico (mayo-junio, aguas en descenso, Verano grande (julio-octubre, Invierno chico (noviembre-diciembre, inicio de la creciente e Invierno grande (enero-abril. Incluye un glosario con la identificación biológica y las definiciones de 183 nombres de animales, plantas y expresiones del español local.

Global positioning system theory and practice

CERN Document Server

Hofmann-Wellenhof, Bernhard; Collins, James

2001-01-01

This book is dedicated to Dr. Benjamin William Remondi for many reasons. The project of writing a Global Positioning System (GPS) book was con­ ceived in April 1988 at a GPS meeting in Darmstadt, Germany. Dr. Remondi discussed with me the need for an additional GPS textbook and suggested a possible joint effort. In 1989, I was willing to commit myself to such a project. Unfortunately, the timing was less than ideal for Dr. Remondi. Therefore, I decided to start the project with other coauthors. Dr. Remondi agreed and indicated his willingness to be a reviewer. I selected Dr. Herbert Lichtenegger, my colleague from the Technical University Graz, Austria, and Dr. James Collins from Rockville, Maryland, U.S.A. In my opinion, the knowledge ofthe three authors should cover the wide spectrum of GPS. Dr. Lichtenegger is a geodesist with broad experience in both theory and practice. He has specialized his research to geodetic astron­ omy including orbital theory and geodynamical phenomena. Since 1986, Dr. Lichteneg...

Fokker-Planck-Rosenbluth-type equations for self-gravitating systems in the 1PN approximation

International Nuclear Information System (INIS)

Ramos-Caro, Javier; Gonzalez, Guillermo A

2008-01-01

We present two formulations of Fokker-Planck-Rosenbluth-type (FPR) equations for many-particle self-gravitating systems, with first-order relativistic corrections in the post-Newtonian approach (1PN). The first starts from a covariant Fokker-Planck equation for a simple gas, introduced recently by Chacon-Acosta and Kremer (2007 Phys. Rev. E 76 021201). The second derivation is based on the establishment of an 1PN-BBGKY hierarchy, developed systematically from the 1PN microscopic law of force and using the Klimontovich-Dupree (KD) method. We close the hierarchy by the introduction of a two-point correlation function that describes adequately the relaxation process. This picture reveals an aspect that is not considered in the first formulation: the contribution of ternary correlation patterns to the diffusion coefficients, as a consequence of the nature of 1PN interaction. Both formulations can be considered as a generalization of the equation derived by Rezania and Sobouti (2000 Astron. Astrophys. 354 1110), to stellar systems where the relativistic effects of gravitation play a significant role

The "Cool Algol" BD+05 706 : Photometric observations of a new eclipsing double-lined spectroscopic binary

Science.gov (United States)

Marschall, L. A.; Torres, G.; Neuhauser, R.

1998-05-01

BVRI Observations of the star BD+05 706, carried out between January, 1997, and April 1998 using the 0.4m reflector and Photometrics CCD camera at the Gettysburg College Observatory, show that the star is an eclipsing binary system with a light curve characteristic of a class of semi-detached binaries known as the "cool Algols". These results are in good agreement with the previous report of BD+05 706 as a cool Algol by Torres, Neuhauser, and Wichmann,(Astron. J., 115, May 1998) who based their classification on the strong X-ray emission detected by Rosat and on a series of spectroscopic observations of the radial velocities of both components of the system obtained at the Oak Ridge Observatory, the Fred L. Whipple Observatory, and the Multiple Mirror Telescope. Only 10 other examples of cool Algols are known, and the current photometric light curve, together with the radial velocity curves obtained previously, allows us to derive a complete solution for the physical parameters of each component, providing important constraints on models for these interesting systems.

Simulación de la trayectoria de un cohete de dos etapas para posicionamiento de un nanosatélite en órbita

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Jhonathan Orlando Murcia Piñeros

2014-01-01

Full Text Available En el presente artículo se estudia el posible lanzamiento de un cohete de dos etapas impulsado por propelentes líquidos tipo RP-1 para transportar una carga útil de 4 kg equivalente a la masa de un nano-satélite de tres unidades de Cubesat. Se plantea el estudio con el diseño conceptual del cohete portador implementando un código computacional de optimización con la finalidad de reducir la masa al despegue y aumentar la velocidad. Se eligió como sitio de lanzamiento desde Colombia a la base del Grupo Aéreo del Oriente (GAORI en Marandúa, Vichada, dado que en la actualidad se realizan investigaciones en lanzamiento de cohetes y ha sido utilizado por universidades para el desarrollo de tales investigaciones. Los valores obtenidos anteriormente son introducidos en un código computacional en FORTRAN desarrollado en el Observatorio Astronómico de la Universidad Nacional de Colombia para obtener el comportamiento de la trayectoria de vuelo del cohete durante su fase de ascenso e inyección orbital.

Diagnostics for induction accelerators

International Nuclear Information System (INIS)

Fessenden, T.J.

1996-04-01

The induction accelerator was conceived by N. C. Christofilos and first realized as the Astron accelerator that operated at LLNL from the early 1960's to the end of 1975. This accelerator generated electron beams at energies near 6 MeV with typical currents of 600 Amperes in 400 ns pulses. The Advanced Test Accelerator (ATA) built at Livermore's Site 300 produced 10,000 Ampere beams with pulse widths of 70 ns at energies approaching 50 MeV. Several other electron and ion induction accelerators have been fabricated at LLNL and LBNL. This paper reviews the principal diagnostics developed through efforts by scientists at both laboratories for measuring the current, position, energy, and emittance of beams generated by these high current, short pulse accelerators. Many of these diagnostics are closely related to those developed for other accelerators. However, the very fast and intense current pulses often require special diagnostic techniques and considerations. The physics and design of the more unique diagnostics developed for electron induction accelerators are presented and discussed in detail

Central stars of planetary nebulae: New spectral classifications and catalogue

Science.gov (United States)

Weidmann, W. A.; Gamen, R.

2011-02-01

Context. There are more than 3000 confirmed and probable known Galactic planetary nebulae (PNe), but central star spectroscopic information is available for only 13% of them. Aims: We undertook a spectroscopic survey of central stars of PNe at low resolution and compiled a large list of central stars for which information was dispersed in the literature. Methods: We observed 45 PNs using the 2.15 m telescope at Casleo, Argentina. Results: We present a catalogue of 492 confirmed and probable CSPN and provide a preliminary spectral classification for 45 central star of PNe. This revises previous values of the proportion of CSPN with atmospheres poor in hydrogen in at least 30% of cases and provide statistical information that allows us to infer the origin of H-poor stars. Based on data collected at the Complejo Astronómico El Leoncito (CASLEO), which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina y Universidades Nacionales de La Plata, Córdoba y San Juan, Argentina.

Central stars of planetary nebulae. II. New OB-type and emission-line stars

Science.gov (United States)

Weidmann, W. A.; Gamen, R.

2011-07-01

Context. There are more than 3000 confirmed and probably known Galactic planetary nebulae (PNe), but central star spectroscopic information is available for only 13% of them. Aims: We have undertaken a spectroscopic survey of the central stars in PNe to identify their spectral types. Methods: We performed spectroscopic observations at low resolution with the 2-m telescope at CASLEO, Argentina. Results: We present the spectra of 46 central stars of PNe, most of them are OB-type and emission-line stars. Based on data collected at the Complejo Astronómico El Leoncito (CASLEO), which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina y Universidades Nacionales de La Plata, Córdoba y San Juan, Argentina.The reduced spectra (FITS files) are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/531/A172

Inflationary scenario from higher curvature warped spacetime

International Nuclear Information System (INIS)

Banerjee, Narayan; Paul, Tanmoy

2017-01-01

We consider a five dimensional warped spacetime, in presence of the higher curvature term like F(R) = R + αR 2 in the bulk, in the context of the two-brane model. Our universe is identified with the TeV scale brane and emerges as a four dimensional effective theory. From the perspective of this effective theory, we examine the possibility of ''inflationary scenario'' by considering the on-brane metric ansatz as an FRW one. Our results reveal that the higher curvature term in the five dimensional bulk spacetime generates a potential term for the radion field. Due to the presence of radion potential, the very early universe undergoes a stage of accelerated expansion and, moreover, the accelerating period of the universe terminates in a finite time. We also find the spectral index of curvature perturbation (n s ) and the tensor to scalar ratio (r) in the present context, which match with the observational results based on the observations of Planck (Astron. Astrophys. 594, A20, 2016). (orig.)

Observing the Future: Simulating Next-Generation Radio Telescopes with MeqTrees

Science.gov (United States)

Willis, A. G.

2008-08-01

Future radio telescopes such as the Square Kilometer Array (SKA) present us with a number of unprecedented challenges. To select a design that will be able to achieve the SKA requirements, we need good models of the instrument and the observed sky. This makes detailed SKA simulations a vital part of any design effort. The Measurement Equation (ME) that grew out of aips++ development provides a succinct mathematical framework in which a radio telescope and the observed sky may be described. The MeqTrees software package, originally developed at ASTRON for the purpose of calibrating the Low-Frequency Array (LOFAR), provides a flexible software system for implementing MEs of arbitrary structure and complexity, and for solving for arbitrary subsets of their parameters. This poster will examine how the ME and MeqTrees can be applied to SKA simulations. In particular we simulate an SKA pathfinder consisting of small dishes with phased-array focal-plane arrays mounted at the primary focus, and show some of the instrumental effects expected and their impact on observations.

Inflationary scenario from higher curvature warped spacetime

Energy Technology Data Exchange (ETDEWEB)

Banerjee, Narayan [Indian Institute of Science Education and Research Kolkata, Department of Physical Sciences, Nadia, West Bengal (India); Paul, Tanmoy [Indian Association for the Cultivation of Science, Department of Theoretical Physics, Kolkata (India)

2017-10-15

We consider a five dimensional warped spacetime, in presence of the higher curvature term like F(R) = R + αR{sup 2} in the bulk, in the context of the two-brane model. Our universe is identified with the TeV scale brane and emerges as a four dimensional effective theory. From the perspective of this effective theory, we examine the possibility of ''inflationary scenario'' by considering the on-brane metric ansatz as an FRW one. Our results reveal that the higher curvature term in the five dimensional bulk spacetime generates a potential term for the radion field. Due to the presence of radion potential, the very early universe undergoes a stage of accelerated expansion and, moreover, the accelerating period of the universe terminates in a finite time. We also find the spectral index of curvature perturbation (n{sub s}) and the tensor to scalar ratio (r) in the present context, which match with the observational results based on the observations of Planck (Astron. Astrophys. 594, A20, 2016). (orig.)

Conversations with Marcgrave: the Origin of Modern Astronomy in the Southern Hemisphere (Spanish Title: Conversando con Marcgrave: El Origen de la Astronomía Moderna en el Hemisferio Sur) Conversando Com Marcgrave: a Origem da Moderna Astronomia no Hemisfério Sul

Science.gov (United States)

Medeiros, Alexandre; Araújo, Fábio

2005-12-01

primer observatorio astronómico del hemisferio y autor de las primeras observaciones astronómicas sistemáticas utilizando telescopios de este lado del mundo. Nuestra "conversación" con Marcgrave es imaginada en el marco del Recife antiguo, lugar donde él vivió durante el período de Mauricio de Nassau, y reune algunos colegas profesores apasionados por la enseñanza de la Astronomía. La historia es contada, de esta forma, dentro de un clima ameno y hasta un poco divertido, si bien las informaciones históricas y conceptuales contenidas en ella están basadas en fuentes bibliográficas confiables, debidamente referenciadas al final del texto. Estas fuentes van desde la obra original de este científico, en la cual aparece su relato sobre la observación de un eclipse solar en Recife, pasando por obras clásicas respecto de él mismo, como la del profesor Juliano Moreira, hasta fuentes mucho más recientes como el influyente trabajo del profesor John North. Otros textos importantes referidos al período de la colonización holandesa en el Brasil, tales como las obras clásicas de Charles Boxer, Bouman y Boogaart entre otros, son también utilizados en la construcción de esta dramatización pedagógica que se refiere a un interesante capítulo de la Historia de la Astronomía. O ano de 2004 assinala os 400 anos do nascimento do conde Maurício de Nassau, um importante personagem da história do Brasil. O presente texto está relacionado com o período do domínio holandês em Pernambuco. O artigo tenta resgatar o começo do estudo da Astronomia no hemisfério Sul. Para tal, idealizamos uma dramatização de uma entrevista fictícia com o astrônomo alemão Georg Marcgrave, construtor do primeiro observatório astronômico deste hemisfério e autor das primeiras observações astronômicas sistemáticas com o uso de telescópios neste lado do mundo. Nossa "conversa" com Marcgrave é idealizada no cenário do Recife antigo, local em que ele viveu no período de Maur

Measurement of Reactions on 30P for Nova Nucleosynthesis

Science.gov (United States)

Ma, Z.; Guidry, M. W.; Hix, W. R.; Smith, M. S.

2003-05-01

-sur-Yvette: Editions Frontiere), 525(SMOKER). 3. Iliadis, C. et al., Astrophys. J. Suppl., 134,151(2001). 4. Snijders et al., 1987 Snijders, M. A. J., et al., Mon. Not. Roy. Astron. Soc., 228, 329(1987). 5. Andrea, J., Drechsel, H., Starrfield, S., Astron. Astrophys., 291,869(1994) *Managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.

Monitoreo del Clima Espacial desde Colombia mediante Radio-receptores Butterworth de Orden Superior

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Andrés Felipe Jaramillo Alvarado

2017-01-01

Full Text Available Contexto: las fulguraciones solares y las eyecciones de masa coronal liberan al espacio grandes cantidades de radiación que, al alcanzar las capas exteriores de la atmósfera terrestre, alteran sus características eléctricas. El conjunto de fenómenos derivados de esta interacción se conoce como clima espacial y sus consecuencias incluyen fallas en los sistemas de geolocalización, las telecomunicaciones, las operaciones vía satélite, el seguimiento espacial, la radionavegación y la sobrecarga de redes eléctricas. Método: en este trabajo se presenta el desarrollo de un radio receptor que permite adelantar el monitoreo del clima espacial desde Colombia. Además, se describe una metodología novedosa para el diseño de filtros analógicos de orden superior de característica Butterworth, a partir de la interconexión en paralelo de bancos de filtros de primero y segundo orden, obteniéndose la función de transferencia deseada. Resultados: el radio receptor desarrollado se instaló en la estación de monitoreo del clima espacial del Observatorio Astronómico de la Universidad Tecnológica de Pereira (OAUTP, Colombia, entrando en operación en diciembre de 2015. Desde esa fecha, el sistema ha registrado la actividad solar de forma ininterrumpida, detectando cuatro potentes explosiones solares clase C presentadas los días 15, 16 y 17 del mes de abril de 2016. Las señales recibidas por el radio receptor son enviadas a la base de datos global del Stanford Solar Center, de Stanford University, con el código UTP 0383. Conclusiones: el radio telescopio desarrollado permite al Observatorio Astronómico OAUTP adelantar el monitoreo del clima espacial y de la actividad solar, enviando la información recibida a repositorios de acceso público a nivel mundial. No existen otros receptores de radio de este tipo operando en la actualidad en países ecuatoriales, una región de la Tierra donde los efectos de la actividad solar pueden conducir a

Conservación de material histórico sobre papel en el Observatorio Astronómico de la Universidad Nacional de Córdoba

Science.gov (United States)

Laguzzi, N.; Tonini, A.; Andreoli, G.; Goldes, G.; Paolantonio, S.; Cequeira, F.; Landi, L.; Alba, J.

At the recently created Astronomical Museum ``Pte. Sarmiento - Dr. Benjamin Gould", the task of preventive conservation of historic documents has been faced. These materials include: 1) letters exchanged between national authorities and the directors of the Observatory, during the first decades (1870-1880-1890); b) original observation logs from these very first times, containing astrometrical and photometrical data; c) a variety of ancient books and papers; d) administrative documents. The state of conservation of this patrimony was varied: since well-conserved books and letters, to highly degraded logs. The observation logs written by B. Gould and the astronomers who followed him had been stocked in a safe with a permanent humidity of about 70 %, without any ventilation and exposed to the attack of insects of the family ``dermestidae." These conditions could not be worse for the conservation of paper. In order to stop the proccess of degradation and create a healthy environment for written-paper conservation, a team was formed with personnel belonging to the Cultural Area of the Municipality. The tasks being performed on the observation logs are: 1) an initial, mechanical cleaning, performed once the material is extracted from the contaminated safe: by these means, adult insects and pupas are removed 2) a stage of about two weeks of duration, in which the logs are mantained in a vacuum chamber, in orden to completely eliminate the adult, pupa and egg stage insects by anoxia 3) the final mechanical cleaning 4) storage in a clean location. In order to perform these tasks, we work in collaboration with the Environmental Observatory of the City, and the group of Material-Science Research of Fa.M.A.F. Regarding the letters, a mechanical cleaning was performed. After that, the letters were digitized by means of a scanner, inventoried, put inside acid-free polipropylene envelops and filed for conservation, protected from intense light and external sources of contamination. Copies of these letters will be included as exhibits.

Diagnostics for induction accelerators

International Nuclear Information System (INIS)

Fessenden, T.J.

1997-01-01

The induction accelerator was conceived by N. C. Christofilos and first realized as the Astron accelerator that operated at Lawrence Livermore National Laboratory (LLNL) from the early 1960s to the end of 1975. This accelerator generated electron beams at energies near 6 MeV with typical currents of 600 Amperes in 400-ns pulses. The Advanced Test Accelerator (ATA) built at Livermore close-quote s Site 300 produced 10,000-Ampere beams with pulse widths of 70 ns at energies approaching 50 MeV. Several other electron and ion induction accelerators have been fabricated at LLNL and Lawrence Berkeley National Laboratory (LBNL). This paper reviews the principal diagnostics developed through efforts by scientists at both laboratories for measuring the current, position, energy, and emittance of beams generated by these high-current, short-pulse accelerators. Many of these diagnostics are closely related to those developed for other accelerators. However, the very fast and intense current pulses often require special diagnostic techniques and considerations. The physics and design of the more unique diagnostics developed for electron induction accelerators are presented and discussed in detail. copyright 1997 American Institute of Physics

Stability of Multi-Planet Systems in the Alpha Centauri System

Science.gov (United States)

Lissauer, Jack J.

2017-01-01

We evaluate the extent of the regions within the alpha Centauri AB star system where small planets are able to orbit for billion-year timescales (Quarles & Lissauer 2016, Astron. J. 151, 111), as well as how closely-spaced planetary orbits can be within those regions in which individual planets can survive. Although individual planets on low inclination, low eccentricity, orbits can survive throughout the habitable zones of both stars, perturbations from the companion star imply that the spacing of planets in multi-planet systems within the habitable zones of each star must be significantly larger than the spacing of similar multi-planet systems orbiting single stars in order to be long-lived. Because the binary companion induces a forced eccentricity upon the orbits of planets in orbit around either star, appropriately-aligned circumstellar orbits with small initial eccentricities are stable to slightly larger initial semimajor axes than are initially circular orbits. Initial eccentricities close to forced eccentricities can have a much larger affect on how closely planetary orbits can be spaced, and therefore on how many planets may remain in the habitable zones, although the required spacing remains significantly higher than for planets orbiting single stars.

Foco Nasmyth para el telescopio 2,15mts. de CASLEO

Science.gov (United States)

Casagrande, A. R.

En principio, este proyecto intenta lograr el mayor aprovechamiento posible del instrumental que se dispone, buscando la manera de optimizar y hacer más eficiente el servicio que brinda el CASLEO a la comunidad astronómica. El mismo consiste en utilizar dispositivos ya existentes en el telescopio, y darle una utilidad. Tal es el caso del camino óptico destinado al foco Coude. Si tenemos en cuenta que disponemos de un tercer espejo Coude, con todos sus mecanismos automatizados, (actualmente sin uso), una distancia apropiada del plano focal, el espacio y el lugar físico necesario para instalar un periférico, es posible la habilitación de un foco Nasmyth en el telescopio 2,15mts. El hecho de contar con este nuevo foco, redundará en importantes beneficios. En primer lugar, posibilitará la observación, casi simultánea, con dos instrumentos. Otro aspecto a tener en cuenta, es que disminuirá el frecuente cambio del instrumental periférico, motivo este que degrada su ideal puesta a punto. Por último, también de interés, es de destacar su escaso costo de ejecución.

Spectroscopic determination of fundamental parameters of small angular diameter galactic open clusters

Science.gov (United States)

Ahumada, A. V.; Claria, J. J.; Bica, E.; Parisi, M. C.; Torres, M. C.; Pavani, D. B.

We present integrated spectra obtained at CASLEO (Argentina) for 9 galactic open clusters of small angular diameter. Two of them (BH 55 and Rup 159) have not been the target of previous research. The flux-calibrated spectra cover the spectral range approx. 3600-6900 A. Using the equivalent widths (EWs) of the Balmer lines and comparing the cluster spectra with template spectra, we determined E(B-V) colour excesses and ages for the present cluster sample. The parameters obtained for 6 of the clusters show good agreement with previous determinations based mainly on photometric methods. This is not the case, however, for BH 90, a scarcely reddened cluster, for which Moffat and Vogt (1975, Astron. and Astroph. SS, 20, 125) derived E(B-V) = 0.51. We explain and justify the strong discrepancy found for this object. According to the present analysis, 3 clusters are very young (Bo 14, Tr 15 and Tr 27), 2 are moderately young (NGC 6268 and BH 205), 3 are Hyades-like clusters (Rup 164, BH 90 and BH 55) and only one is an intermediate-age cluster (Rup 159).

Maximum gravitational-wave energy emissible in magnetar flares

Science.gov (United States)

Corsi, Alessandra; Owen, Benjamin J.

2011-05-01

Recent searches of gravitational-wave data raise the question of what maximum gravitational-wave energies could be emitted during gamma-ray flares of highly magnetized neutron stars (magnetars). The highest energies (˜1049erg) predicted so far come from a model [K. Ioka, Mon. Not. R. Astron. Soc.MNRAA40035-8711 327, 639 (2001), http://adsabs.harvard.edu/abs/2001MNRAS.327..639I] in which the internal magnetic field of a magnetar experiences a global reconfiguration, changing the hydromagnetic equilibrium structure of the star and tapping the gravitational potential energy without changing the magnetic potential energy. The largest energies in this model assume very special conditions, including a large change in moment of inertia (which was observed in at most one flare), a very high internal magnetic field, and a very soft equation of state. Here we show that energies of 1048-1049erg are possible under more generic conditions by tapping the magnetic energy, and we note that similar energies may also be available through cracking of exotic solid cores. Current observational limits on gravitational waves from magnetar fundamental modes are just reaching these energies and will beat them in the era of advanced interferometers.

Maximum gravitational-wave energy emissible in magnetar flares

International Nuclear Information System (INIS)

Corsi, Alessandra; Owen, Benjamin J.

2011-01-01

Recent searches of gravitational-wave data raise the question of what maximum gravitational-wave energies could be emitted during gamma-ray flares of highly magnetized neutron stars (magnetars). The highest energies (∼10 49 erg) predicted so far come from a model [K. Ioka, Mon. Not. R. Astron. Soc. 327, 639 (2001), http://adsabs.harvard.edu/abs/2001MNRAS.327..639I] in which the internal magnetic field of a magnetar experiences a global reconfiguration, changing the hydromagnetic equilibrium structure of the star and tapping the gravitational potential energy without changing the magnetic potential energy. The largest energies in this model assume very special conditions, including a large change in moment of inertia (which was observed in at most one flare), a very high internal magnetic field, and a very soft equation of state. Here we show that energies of 10 48 -10 49 erg are possible under more generic conditions by tapping the magnetic energy, and we note that similar energies may also be available through cracking of exotic solid cores. Current observational limits on gravitational waves from magnetar fundamental modes are just reaching these energies and will beat them in the era of advanced interferometers.

Impactos ambientais e sociais da Copa do Mundo de 2014

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Marilia Carla de Mello Gaia

2014-05-01

Full Text Available Desde a escolha do Brasil, em 2007, para sediar a Copa do Mundo de Futebol de 2014 e as Olimpíadas de 2016, este é um tema recorrente na mídia e em demais espaços de socialização dos brasileiros. Muitas discussões a cerca destes megaeventos esportivos envolvem os benefícios relacionados ao incentivo ao esporte nacional, ao incremento no turismo e na economia e às obras de infraestrutura (sistema de transporte urbano, aeroportos, arenas esportivas, comércio, etc.. A partir das manifestações populares em junho de 2013, principalmente, amplia-se em uma parcela da população brasileira um outro olhar sobre estes eventos esportivos, sobretudo os questionamentos relacionados às necessidades sociais da população em detrimento dos astronômicos investimentos financeiros e políticos para a Copa. Neste contexto, este artigo se destina a discutir alguns elementos envolvidos nos impactos sociais e ambientais da realização da Copa do Mundo de Futebol e das Olimpíadas no Brasil.

Impactos ambientais e sociais da Copa do Mundo de 2014 http://dx.doi.org/10.15601/1983-7631/rt.v7n12p59-66

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Marilia Carla de Mello Gaia

2014-05-01

Full Text Available Desde a escolha do Brasil, em 2007, para sediar a Copa do Mundo de Futebol de 2014 e as Olimpíadas de 2016, este é um tema recorrente na mídia e em demais espaços de socialização dos brasileiros. Muitas discussões a cerca destes megaeventos esportivos envolvem os benefícios relacionados ao incentivo ao esporte nacional, ao incremento no turismo e na economia e às obras de infraestrutura (sistema de transporte urbano, aeroportos, arenas esportivas, comércio, etc.. A partir das manifestações populares em junho de 2013, principalmente, amplia-se em uma parcela da população brasileira um outro olhar sobre estes eventos esportivos, sobretudo os questionamentos relacionados às necessidades sociais da população em detrimento dos astronômicos investimentos financeiros e políticos para a Copa. Neste contexto, este artigo se destina a discutir alguns elementos envolvidos nos impactos sociais e ambientais da realização da Copa do Mundo de Futebol e das Olimpíadas no Brasil.

On the jets, kinks, and spheromaks formed by a planar magnetized coaxial gun

International Nuclear Information System (INIS)

Hsu, S.C.; Bellan, P.M.

2005-01-01

Measurements of the various plasma configurations produced by a planar magnetized coaxial gun provide insight into the magnetic topology evolution resulting from magnetic helicity injection. Important features of the experiments are a very simple coaxial gun design so that all observed geometrical complexity is due to the intrinsic physical dynamics rather than the source shape and use of a fast multiple-frame digital camera which provides direct imaging of topologically complex shapes and dynamics. Three key experimental findings were obtained: (1) formation of an axial collimated jet [Hsu and Bellan, Mon. Not. R. Astron. Soc. 334, 257 (2002)] that is consistent with a magnetohydrodynamic description of astrophysical jets (2) identification of the kink instability when this jet satisfies the Kruskal-Shafranov limit, and (3) the nonlinear properties of the kink instability providing a conversion of toroidal to poloidal flux as required for spheromak formation by a coaxial magnetized source [Hsu and Bellan, Phys. Rev. Lett. 90, 215002 (2003)]. An interpretation is proposed for how the n=1 central column instability provides flux amplification during spheromak formation and sustainment, and it is shown that jet collimation can occur within one rotation of the background poloidal field

La astronomía de un humanista, Juan Andrés

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José Antonio SANDUVETE CHAVES

2009-11-01

Full Text Available RESUMEN: La páginas que siguen pretenden ofrecer una visión de conjunto del análisis que de la historia de la Astronomía realiza Juan Andrés, desde los orígenes de la humanidad hasta el siglo XVIII. Este análisis, incluido en su monumental obra Origen, progresos y estado actual de toda la literatura, destaca por su modernidad y precisión, constituyendo, por tanto, una interesante base de comparación entre la visión de la ciencia astronómica del humanismo ilustrado y la que pervive en la actualidad.ABSTRACT: The following pages attempt to offer a full view of the research into the history of astronomy made by Juan Andrés, from the beginning of human culture until the 18th century. This analysis, included in a broader work called Origen, progresos y estado de toda la literatura, stands out on account of its modern and precise ideas, thus representing an interesting knowledge base for comparing the view of astronomy during the Enlightenment with that of the present.

Programas de aplicación de agrometeorología para docencia e investigación

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Bombelli, Enrique

2009-01-01

Full Text Available Para el estudio de las Ciencias Meteorológicas y Climáticas aplicadas al agro, es necesario estimar procesos matemáticos y físicos para interpretar la interacción de los procesos atmosféricos y biológicos, los cuales se pueden automatizar haciendo énfasis en el análisis de los mismos. El presente trabajo tiene como objetivo mostrar las características de un software de aplicación utilizado para en la enseñanza de la Climatología Agrícola, que estima parámetros tales como: Radiación Astronómica y Global, diferentes metodologías de cálculo de la Evapotranspiración Potencial y el Balance Hidrológico Climático entre otros. El software Programas de aplicación de Agroclimatología, realizado en la Facultad de Agronomía de la Universidad de Buenos Aires, brinda al alumno un rápido manejo de resultados, con la posibilidad de realizar interpretaciones de distintas variables para diferentes localidades, de manera de poder visualizar y analizar los resultados que surgen de las distintas corridas.

Extracción de conocimiento en bases de datos astronómicas mediante redes de neuronas artificiales: aplicaciones en la misión Gaia

Science.gov (United States)

Fustes Villadóniga, Diego

2014-02-01

In the so-called IT era, the capabilities of data acquisition systems have increased to such an extent that it has become difficult to store all the information they produce, and analyse it. This explosion of data has recently appeared in the field of Astronomy, where an increasing number of objects are being observed on a regular basis. An example of this is the upcoming Gaia mission, which will pick up multiple properties of a billion stars, whose information will have a volume of approximately a petabyte. The analysis of a similar amount of information inevitably requires the development of new data analysis methods to extract all the knowledge it contains. This thesis is devoted to the development of data analysis methods to be integrated in the Gaia pipeline, such that knowledge can be extracted from the data collected by the mission. In order to analyze the data from the Gaia mission, the European Space Agency organized the Data Processing and Analysis Consortium (DPAC) which is composed of hundreds of scientists and engineers. DPAC is divided into eight Coordination Units (CUs). This thesis is dedicated to algorithm development in CU8, which is responsible for source classification and astrophysical parameters (AP) estimation. Methods based on Artificial Neural Networks (ANNs) are developed to perform the tasks related to two different work packages in CU8: the GSP-Spec package (GWP-823), and the OA package (GWP-836). The GSP-Spec package is responsible for estimating stellar APs by means of the Radial Velocity Spectrograph (RVS) spectrum. This work presents the development of one of the GSP-Spec modules, which is based on the application of feed-forward ANNs. A methodology is described, based on the optimization of genetic algorithms and aimed at obtaining an optimal set of configuration parameters for the ANN in each case, depending on the signal to noise ratio (SNR) in the RVS spectrum and on the type of star to parameterize. Furthermore, in order to improve the AP estimates, wavelet signal processing techniques, applied to the RVS spectrum, are studied. Despite the effectiveness shown by ANNs in estimating APs, in principle they lack the ability to provide an uncertainty value on these estimates, making it impossible to determine their reliability. Because of this, a new architecture for the ANN is presented in which the inputs and outputs are reversed, so that the ANN estimates the RVS spectrum from the APs. Such an architecture is called Generative ANN (GANN) and is applied to the AP estimation of a set of simulated RVS spectra for the Gaia mission, where it is more effective than the conventional ANN model, in the case of faint stars with low SNR. Finally, the GANN can be applied for obtaining the posterior probability of each of the APs according to the RVS spectrum, allowing for their more complete analysis. Given the nature of the Gaia mission, which is the first astronomical mission that will observe, in an unbiased way, the entire sky up to magnitude 20, a large number of outliers are expected. The OA package in CU8 handles the processing of this type of objects, which are defined as those that could not be reliably classified by the methods in the upstream classification packages. OA methods are based on the unsupervised learning of all outliers. Such learning has two parts: clustering and dimensionality reduction. The Self-Organizing Map (SOM) algorithm is selected as a basis for this learning. Its effectiveness is demonstrated when it is applied, with an optimal configuration, to the Gaia simulations. Furthermore, the algorithm is applied to real outliers from the SDSS catalog. Since a subsequent identification of the clusters obtained by the SOM is necessary, two different methods of identification are applied. The first method is based on the similarity between the SOM prototypes and the Gaia simulations, and the second method is based on the recovery of stored classifications in the SIMBAD catalog by cross-matching celestial coordinates. Thanks to the visualization of the SOM planes, and to both methods of identification, it is possible to distinguish between valid observations and observational artifacts. Furthermore, the method allows for the selection of objects of interest for follow-up observations, in order to determine their nature.

Mesa redonda: Argentina en proyectos globales de investigaciones espaciales y astronómicas. Uso científico de la Antena de Espacio Profundo DSA 3

Science.gov (United States)

Colazo, M.

2016-08-01

Argentine has 10 percent of the operative time available for the DSA 3 Antenna of the European Space Agency, installed in Malargüe, Mendoza. Here we present the history of the project and the current activities for the scientific use of the antenna.

Mapping the Region in the Nearest Star System to Search for Habitable Planets

Science.gov (United States)

Lissauer, Jack J.; Quarles, B.

2015-01-01

Circumstellar planets within the alpha Centauri AB star system have been suggested through formation models and recent observations, and ACESat (Belikov et al. AAS Meeting #225, #311.01, 2015) is a proposed space mission designed to directly image Earth-sized planets in the habitable zones of both of these stars. The alpha Centauri system is billions of years old, so planets are only expected to be found in regions where their orbits are long-lived. We evaluate the extent of the regions within the alpha Centauri AB star system where small planets are able to orbit for billion-year timescales and we map the positions in the sky plane where planets on stable orbits about either stellar component may appear. We confirm the qualitative results of Wiegert & Holman (Astron. J. 113, 1445, 1997) regarding the approximate size of the regions of stable orbits, which are larger for retrograde orbits relative to the binary than for prograde orbits. Additionally, we find that mean motion resonances with the binary orbit leave an imprint on the limits of orbital stability, and the effects of the Lidov-Kozai mechanism are also readily apparent. Overall, orbits in the habitable zones near the plane of the binary are stable, whereas high-inclination orbits are short-lived.

Development of a Lunar Scintillometer as part of the national large optical telescope site survey

Science.gov (United States)

Surendran, Avinash; Parihar, Padmakar S.; Banyal, Ravinder K.; Kalyaan, Anusha

2018-03-01

Ground layer turbulence is a very important site characterization parameter used to assess the quality of an astronomical site. The Lunar Scintillometer is a simple and effective site-testing device for measuring the ground layer turbulence. It consists of a linear array of photodiodes which are sensitive to the slight variations in the moon's brightness due to scintillation by the lower layers of the Earth's atmosphere. The covariance of intensity values between the non-redundant photodiode baselines can be used to measure the turbulence profile from the ground up to a height determined by the furthest pair of detectors. The six channel lunar scintillometer that has been developed at the Indian Institute of Astrophysics is based closely on an instrument built by the team led by Andrei Tokovinin of Cerro Tololo Inter-American Observatory (CTIO), Chile (Tokovinin et al., Mon. Not. R. Astron. Soc. 404(3), 1186-1196 2010). We have fabricated the instrument based on the existing electronic design, and have worked on the noise analysis, an EMI (Electromagnetic Induction) resistant PCB design and the software pipeline for analyzing the data from the same. The results from the instrument's multi-year campaign at Mount Saraswati, Hanle is also presented.

Telescopio Solar en Hα (HASTA)

Science.gov (United States)

Fernández Borda, R.; Francile, C.; Bagala, G.; Bauer, O.; Haerendel, G.; Rieger, E.; Rovira, M.

El Telescopio Solar en Hα (Hα Solar Telescope for Argentina (-HASTA-) fue recientemente instalado en la Estación Astronómica de Altura Carlos Ulrrico Cesco (OAFA) en El Leoncito. Este instrumento estudiará la evolución de las fulguraciones solares desde tierra con alta resolución temporal y espacial. HASTA es un telescopio refractor de 110 mm con una distancia focal de 165 cm, un filtro Lyot sintonizable (±1Å) con un ancho de banda de 0.3 Å y una cámara CCD de alta resolución (1280×1024 pixels). Todo el conjunto es controlado en forma remota por una PC, la cual además adquiere datos del Sistema de Posicionamiento Global (GPS) y de la estación meteorológica. Diseñado para detectar fulguraciones, el instrumento trabaja en dos modos (patrullaje y fulguración) con una resolución espacial de 1.5 arcseg por pixel y una resolución temporal de 2 seg. HASTA comenzó a operar en Mayo de 1998 y, junto con otros tres instrumentos solares, que se están instalando o se instalaron, harán de El Leoncito un polo de observación solar importante en el Hemisferio Sur.

The Stardust Interstellar Dust Collector and Stardust@home

Science.gov (United States)

Westphal, A. J.; Anderson, D.; Bastien, R.; Butterworth, A.; Frank, D.; Gainsforth, Z.; Kelley, N.; Lettieri, R.; Mendez, B.; Prasad, R.; Tsitrin, S.; von Korff, J.; Warren, J.; Wertheimer, D.; Zhang, A.; Zolensky, M.

2006-12-01

The Stardust sample return mission is effectively two missions in one. Stardust brought back to earth for analytical study the first solid samples from a known solar system body beyond the moon, comet Wild2. The first results of the analyses of these samples are reported elsewhere in this session. In a separate aerogel collector, Stardust also captured and has returned the first samples of contemporary interstellar dust. Landgraf et al. [1] has estimated that ~ 50 interstellar dust particles in the micron size range have been captured in the Stardust Interstellar Dust Collector. Their state after capture is unknown. Before analysis of these particles can begin, they must be located in the collector. Here we describe the current status of Stardust@home, the massively distributed public search for these tiny interstellar dust particles. So far more than 13,000 volunteers have collectively performed more than 10,000,000 searches in stacks of digital images of ~10% of the collector. We report new estimates of the flux of interplanetary dust at ~2 AU based on the results of this search, and will compare with extant models[2]. References: [1] Landgraf et al., (1999) Planet. Spac. Sci. 47, 1029. [2] Staubach et al. (2001) in Interplanetary Dust, E. Grün, ed., Astron. &Astro. Library, Springer, 2001.

D'' Layer Activation via Tidal Dissipation: A Link Between Non-Hydrostatic Ellipticity, Non-Chondritic Heat Flux, and Non-Plume Head Generation of Flood Basalts

Science.gov (United States)

Hager, B. H.; Mazarico, E.; Touma, J.; Wisdom, J.

2003-12-01

Quantitative understanding of Earth's heat budget has eluded a list of distinguished physicists and geochemists ranging from Lord Kelvin to Don L Anderson. The global heat flux is substantially greater than that generated by the estimated inventory of radioactive heat sources, so simple energy balance considerations demand an additional heat source. Secular cooling is commonly invoked to balance Earth's energy budget, but the required cooling rates are difficult to reconcile with both traditional convection calculations and petrologic estimates of ancient upper mantle temperatures. A non-geochemical heat source seems plausible. Indeed, Tuoma and Wisdom (Astron. J., 122, 2001) showed that tidal dissipation of rotational energy associated with resonant coupling could provide a substantial heat pulse to the CMB. D'' Layer Activation (DLA) by dumping of rotational energy could have important geodynamical consequences that we explore here. DLA could lead to a sudden (but modest) increase in the temperature of preexisting plumes, leading to a sudden increase in melt volume without the need for a troublesome plume head. The dissipation depends on non-hydrostatic CMB ellipticity, which itself is a result of mantle convection, leading to the possibility of an important feedback mechanism - DLA would lead to an increase in CMB ellipticity, further increasing the geodynamic importance of DLA.

On the shear instability in relativistic neutron stars

Science.gov (United States)

Corvino, Giovanni; Rezzolla, Luciano; Bernuzzi, Sebastiano; De Pietri, Roberto; Giacomazzo, Bruno

2010-06-01

We present new results on instabilities in rapidly and differentially rotating neutron stars. We model the stars in full general relativity and describe the stellar matter adopting a cold realistic equation of state based on the unified SLy prescription (Douchin and Haensel 2001 Astron. Astrophys. 380 151-67). We provide evidence that rapidly and differentially rotating stars that are below the expected threshold for the dynamical bar-mode instability, βc ≡ T/|W| ~= 0.25, do nevertheless develop a shear instability on a dynamical timescale and for a wide range of values of β. This class of instability, which has so far been found only for small values of β and with very small growth rates, is therefore more generic than previously found and potentially more effective in producing strong sources of gravitational waves. Overall, our findings support the phenomenological predictions made by Watts et al (2005 Astrophys. J. 618 L37) on the nature of the low-T/|W| instability as the manifestation of a shear instability in a region where the latter is possible only for small values of β. Furthermore, our results provide additional insight on shear instabilities and on the necessary conditions for their development.

On the shear instability in relativistic neutron stars

Energy Technology Data Exchange (ETDEWEB)

Corvino, Giovanni; Rezzolla, Luciano; Giacomazzo, Bruno [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Golm (Germany); Bernuzzi, Sebastiano [Theoretical Physics Institute, University of Jena, 07743 Jena (Germany); De Pietri, Roberto, E-mail: Giovanni.Corvino@roma1.infn.i [Physics Department, Parma University and INFN, Parma (Italy)

2010-06-07

We present new results on instabilities in rapidly and differentially rotating neutron stars. We model the stars in full general relativity and describe the stellar matter adopting a cold realistic equation of state based on the unified SLy prescription (Douchin and Haensel 2001 Astron. Astrophys. 380 151-67). We provide evidence that rapidly and differentially rotating stars that are below the expected threshold for the dynamical bar-mode instability, {beta}{sub c} {identical_to} T/|W| {approx_equal} 0.25, do nevertheless develop a shear instability on a dynamical timescale and for a wide range of values of {beta}. This class of instability, which has so far been found only for small values of {beta} and with very small growth rates, is therefore more generic than previously found and potentially more effective in producing strong sources of gravitational waves. Overall, our findings support the phenomenological predictions made by Watts et al (2005 Astrophys. J. 618 L37) on the nature of the low-T/|W| instability as the manifestation of a shear instability in a region where the latter is possible only for small values of {beta}. Furthermore, our results provide additional insight on shear instabilities and on the necessary conditions for their development.

Divulgación del Programa Consolider-GTC

Science.gov (United States)

Ruiz Zelmanovitch, N.; Mass Hesse, M.; Alfaro, E.

2013-05-01

The Gran Telescopio Canarias (GTC) is the biggest telescope of its class in the world. The CONSOLIDER INGENIO 2010-GTC project, First Science with the GTC: Spanish Astron- omy on the Forefront of the European Astronomy, funded by the Spanish Ministry of Science and Innovation, MICINN (now the Ministry of Economy and competitiveness, MINECO) has used the GTC to: (i) obtain leading science with its data, (ii) increase the involvement of the Spanish astronomical community in developing astronomical instrumentation, (iii) get an important Spanish participation in the new extremely large telescopes generation (ELTs), and (iv) make outreach and communicating to the society the main results. The project CONSOLIDER INGENIO 2010-GTC is structured and defined by objectives: 1) GTC: To optimize the GTC and its instruments; 2) SCIENCE: To develop leading science with the GTC; 3) E-ELT: To take advantage of the technological experience obtained with the GTC for the new generation of giant telescopes; 4) INSTRUMENTATION: To promote the Spanish participation in the new instrument developments for the GTC, VLT and the future ELTs; 5) EDUCATION: International School for Advanced Instrumentation (IScAI); and 6) OUTREACH: Outreach and communication of the project scientific results. This poster resumes five years of science communication around the Consolider-GTC project.

Cosmological implications of a large complete quasar sample.

Science.gov (United States)

Segal, I E; Nicoll, J F

1998-04-28

Objective and reproducible determinations of the probabilistic significance levels of the deviations between theoretical cosmological prediction and direct model-independent observation are made for the Large Bright Quasar Sample [Foltz, C., Chaffee, F. H., Hewett, P. C., MacAlpine, G. M., Turnshek, D. A., et al. (1987) Astron. J. 94, 1423-1460]. The Expanding Universe model as represented by the Friedman-Lemaitre cosmology with parameters qo = 0, Lambda = 0 denoted as C1 and chronometric cosmology (no relevant adjustable parameters) denoted as C2 are the cosmologies considered. The mean and the dispersion of the apparent magnitudes and the slope of the apparent magnitude-redshift relation are the directly observed statistics predicted. The C1 predictions of these cosmology-independent quantities are deviant by as much as 11sigma from direct observation; none of the C2 predictions deviate by >2sigma. The C1 deviations may be reconciled with theory by the hypothesis of quasar "evolution," which, however, appears incapable of being substantiated through direct observation. The excellent quantitative agreement of the C1 deviations with those predicted by C2 without adjustable parameters for the results of analysis predicated on C1 indicates that the evolution hypothesis may well be a theoretical artifact.

An Initial Meteoroid Stream Survey in the Southern Hemisphere Using the Southern Argentina Agile Meteor Radar (SAAMER)

Science.gov (United States)

Janches, D.; Hormaechea, J. L.; Brunini, C.; Hocking, W.; Fritts, D. C.

2013-01-01

We present in this manuscript a 4 year survey of meteor shower radiants utilizing the Southern Argentina Agile Meteor Radar (SAAMER). SAAMER, which operates at the southern most region of South America, is a new generation SKiYMET system designed with significant differences from typical meteor radars including high transmitted power and an 8-antenna transmitting array enabling large detected rates at low zenith angles. We applied the statistical methodology developed by Jones and Jones (Jones, J., Jones, W. [2006]. Month. Not. R. Astron. Soc. 367, 1050-1056) to the data collected each day and compiled the results into 1 composite representative year at 1 resolution in Solar Longitude. We then search for enhancements in the activity which last for at least 3 days and evolve temporally as is expected from a meteor shower. Using this methodology, we have identified in our data 32 shower radiants, two of which were not part of the IAU commission 22 meteor shower working list. Recently, SAAMER's capabilities were enhanced by adding two remote stations to receive meteor forward scatter signals from meteor trails and thus enable the determination of meteoroid orbital parameters. SAAMER started recording orbits in January 2012 and future surveys will focus on the search for unknown meteor streams, in particular in the southern ecliptic sky.

Novel matched amplifiers with low noise positive feedback. Part II: Resistive-capacitive feedback

Science.gov (United States)

Bruck, Y.; Zakharenko, V.

2010-02-01

This article is a continuation of consideration for an amplifier with resistive positive feedback (RPF) (Bruck (2008), 'Novel Matched LNA with Low Noise Positive Feedback. Part 1: General Features and Resistive Feedback', International Journal of Electronics, 95, 441-456). We propose here new configuration schematics of a transformer-less selective LNA with resistive-capacitive positive feedback (RCPF). A circuit of an amplifier with a transistor connected into a circuit with a common base (CB) configuration is analysed in detail. RCPF and RPF circuits are compared. It is shown that the LNA RCPF provides any pass-band, a good level of input and output matching, a minimum noise temperature which is significantly lower than that of the LNA RPF, a rather high linearity, and stability of amplification. The simulation results and some experimental data for the amplifiers intended for use in the LOFAR radiotelescope (Konovalenko et al. (2003), 'Thirty Element Array Antenna as a Prototype of a Huge Low-Frequency Radio Telescope,' Experimental Astronomy, 16, 149-164; Konovalenko (2007), 'Ukrainian Contribution to LOFAR', A scientific workshop, organised by LOFAR/ASTRON' Emmen, Netherlands, 23-27. http://www.lofar.org/workshop) are given. It is assumed that such devices are of a special interest for high-frequency integral circuits (IC).

Velocidades radiales en Collinder 121

Science.gov (United States)

Arnal, M.; Morrell, N.

Se han llevado a cabo observaciones espectroscópicas de unas treinta estrellas que son posibles miembros del cúmulo abierto Collinder 121. Las mismas fueron realizadas con el telescopio de 2.15m del Complejo Astronómico El Leoncito (CASLEO). El análisis de las velocidades radiales derivadas del material obtenido, confirma la realidad de Collinder 121, al menos desde el punto de vista cinemático. La velocidad radial baricentral (LSR) del cúmulo es de +17 ± 3 km.s-1. Esta velocidad coincide, dentro de los errores, con la velocidad radial (LSR) de la nebulosa anillo S308, la cual es de ~20 ± 10 km.s-1. Como S308 se encuentra físicamente asociada a la estrella Wolf-Rayet HD~50896, es muy probable que esta última sea un miembro de Collinder 121. Desde un punto de vista cinemático, la supergigante roja HD~50877 (K3Iab) también pertenecería a Collinder 121. Basándonos en la pertenencia de HD~50896 a Collinder 121, y en la interacción encontrada entre el viento de esta estrella y el medio interestelar circundante a la misma, se estima para este cúmulo una distancia del orden de 1 kpc.

Bodily tides near the 1:1 spin-orbit resonance: correction to Goldreich's dynamical model

Science.gov (United States)

Williams, James G.; Efroimsky, Michael

2012-12-01

Spin-orbit coupling is often described in an approach known as " the MacDonald torque", which has long become the textbook standard due to its apparent simplicity. Within this method, a concise expression for the additional tidal potential, derived by MacDonald (Rev Geophys 2:467-541, 1994), is combined with a convenient assumption that the quality factor Q is frequency-independent (or, equivalently, that the geometric lag angle is constant in time). This makes the treatment unphysical because MacDonald's derivation of the said formula was, very implicitly, based on keeping the time lag frequency-independent, which is equivalent to setting Q scale as the inverse tidal frequency. This contradiction requires the entire MacDonald treatment of both non-resonant and resonant rotation to be rewritten. The non-resonant case was reconsidered by Efroimsky and Williams (Cel Mech Dyn Astron 104:257-289, 2009), in application to spin modes distant from the major commensurabilities. In the current paper, we continue this work by introducing the necessary alterations into the MacDonald-torque-based model of falling into a 1-to-1 resonance. (The original version of this model was offered by Goldreich (Astron J 71:1-7, 1996). Although the MacDonald torque, both in its original formulation and in its corrected version, is incompatible with realistic rheologies of minerals and mantles, it remains a useful toy model, which enables one to obtain, in some situations, qualitatively meaningful results without resorting to the more rigorous (and complicated) theory of Darwin and Kaula. We first address this simplified model in application to an oblate primary body, with tides raised on it by an orbiting zero-inclination secondary. (Here the role of the tidally-perturbed primary can be played by a satellite, the perturbing secondary being its host planet. A planet may as well be the perturbed primary, its host star acting as the tide-raising secondary). We then extend the model to a

The Kinematics of the Permitted C ii λ 6578 Line in a Large Sample of Planetary Nebulae

Energy Technology Data Exchange (ETDEWEB)

Richer, Michael G.; Suárez, Genaro; López, José Alberto; García Díaz, María Teresa, E-mail: richer@astrosen.unam.mx, E-mail: gsuarez@astro.unam.mx, E-mail: jal@astrosen.unam.mx, E-mail: tere@astro.unam.mx [Instituto de Astronomía, Universidad Nacional Autónoma de México, Ensenada, Baja California (Mexico)

2017-03-01

We present spectroscopic observations of the C ii λ 6578 permitted line for 83 lines of sight in 76 planetary nebulae at high spectral resolution, most of them obtained with the Manchester Echelle Spectrograph on the 2.1 m telescope at the Observatorio Astronómico Nacional on the Sierra San Pedro Mártir. We study the kinematics of the C ii λ 6578 permitted line with respect to other permitted and collisionally excited lines. Statistically, we find that the kinematics of the C ii λ 6578 line are not those expected if this line arises from the recombination of C{sup 2+} ions or the fluorescence of C{sup +} ions in ionization equilibrium in a chemically homogeneous nebular plasma, but instead its kinematics are those appropriate for a volume more internal than expected. The planetary nebulae in this sample have well-defined morphology and are restricted to a limited range in H α line widths (no large values) compared to their counterparts in the Milky Way bulge; both these features could be interpreted as the result of young nebular shells, an inference that is also supported by nebular modeling. Concerning the long-standing discrepancy between chemical abundances inferred from permitted and collisionally excited emission lines in photoionized nebulae, our results imply that multiple plasma components occur commonly in planetary nebulae.

Monitoring Light Pollution on the Starlight Reserve of Montsec

Science.gov (United States)

Ribas, S. J.; Paricio, S.; Canal-Domingo, R.; Gustems, L.; Calvo, C. O.

2015-05-01

Montsec Mountains are a special protected place in Catalonia (NE of Iberian Peninsula). Since 2013 the site has been declared Starlight Reserve and Touristic Destination. In the last three years different projects took place in Montsec to evaluate the quality of night sky and the effects of Light Pollution of nearby (and not so nearby) municipalities. Using SQM techniques in RoadRunner configuration (installed on a car) we have evaluated all the region (1 600 km^2) and we determined the distribution of night sky brightness detecting some excellent areas with values around 21.5--22.0 mags. In addition we have evaluated the effects of the closest big city (Lleida with around 200 000 inhabitants) and we have estimated long distance effects of this city on the natural sky. The effect is detected on zenith up to 25 km away from the city. These data show the critical problem of the long-distance effects of LP on protected areas. To complete the monitoring of the region, a new SQM network is ongoing in cooperation with Parc Astronòmic Montsec and Catalan Service against Light Pollution. During 2014 six SQM permanent detectors are starting their measurements around the area of Montsec and major cities that affects this protected area. This data could be combined with meteorological data (clouds, humidity, etc) in some of the evaluation sites.

Morfología de la Coma del Cometa Hale - Bopp

Science.gov (United States)

Gil-Hutton, R.; Caballero, M.; Coldwell, G.; Cañada, M.; Godoy, G.; Trozzo, C.; Gómez, G.

Para lograr comprender plenamente los procesos físicos que se desarrollan en los núcleos cometarios y obtener un modelo que explique, no sólo su actividad, sino también sus efectos sobre la coma, es necesario obtener información detallada para el mayor número de cometas posible, siendo las características más interesantes para estudiar la ubicación de las regiones activas, la presencia de jets, las tasas de producción de gas y polvo y la interacción de la coma con el viento solar. En la actualidad, con técnicas de procesamiento de imágenes y tecnología CCD se pueden obtener este tipo de datos para cometas que ingresan al sistema solar interior y estudiar, de esta manera, la morfología de sus comas, tratando de correlacionar la actividad detectada con algún modelo teórico. En este trabajo se presenta un estudio parcial de la actividad desarrollada por el cometa Hale-Bopp, y sus efectos sobre la morfología de su coma, desde agosto de 1995 hasta la fecha en base a imágenes adquiridas con el telescopio de 0.76 m. de la Estación Astronómica Dr. Carlos Ulrrico Cesco.

Evolving coma abundances and detection of hypervolatiles in Jupiter-family comet 45P/Honda-Mrkos-Pajdusakova

Science.gov (United States)

Dello Russo, Neil; DiSanti, Michael A.; Kawakita, Hideyo; Shinnaka, Yoshiharu; Vervack, Ronald J.; Bonev, Boncho P.; Gibb, Erika L.; Roth, Nathan; McKay, Adam J.; Weaver, Harold A.; Cochran, Anita L.

2017-10-01

Two major shortcomings in chemically classifying comets at infrared wavelengths are a lack of hypervolatile (CO and CH4) detections in Jupiter-family comets and incomplete temporal coverage of comet chemistry, particularly at small heliocentric distances (Rh). We report post-perihelion volatile abundances in comet 45P/Honda-Mrkos-Pajdusakova with the high-resolution infrared spectrometer iSHELL at the NASA/IRTF on UT 6 - 8 January when Rh = 0.55 AU (DiSanti et al. 2017, Astron. J., in press), and with NIRSPEC at the Keck Observatory on UT 13 and 19 February when Rh = 1.0 and 1.1 AU, respectively. Favorable comet geocentric velocities enabled the detection of CO and CH4 in early January and 19 February. The relative abundance of CO is severely depleted whereas CH4 is typical to enriched in 45P when compared to comets from the Oort cloud. Significant differences are seen in relative abundances of species between January and February, notably in the ratio of C2H2/HCN. We explore whether the heliocentric distances of the measurements or seasonal changes primarily cause these differences by comparing to observations of C/2012 S1 ISON obtained over a similar range of heliocentric distances. NASA and NSF research grants support this work. We also acknowledge the expert support of the IRTF and Keck support staffs during these observations.

Interstellar scintillations of PSR B1919+21: space-ground interferometry

Science.gov (United States)

Shishov, V. I.; Smirnova, T. V.; Gwinn, C. R.; Andrianov, A. S.; Popov, M. V.; Rudnitskiy, A. G.; Soglasnov, V. A.

2017-07-01

We carried out observations of pulsar PSR B1919+21 at 324 MHz to study the distribution of interstellar plasma in the direction of this pulsar. We used the RadioAstron (RA) space radio telescope, together with two ground telescopes: Westerbork (WB) and Green Bank (GB). The maximum baseline projection for the space-ground interferometer was about 60 000 km. We show that interstellar scintillation of this pulsar consists of two components: diffractive scintillations from inhomogeneities in a layer of turbulent plasma at a distance z1 = 440 pc from the observer or homogeneously distributed scattering material to the pulsar; and weak scintillations from a screen located near the observer at z2 = 0.14 ± 0.05 pc. Furthermore, in the direction to the pulsar we detected a prism that deflects radiation, leading to a shift in observed source position. We show that the influence of the ionosphere can be ignored for the space-ground baseline. Analysis of the spatial coherence function for the space-ground baseline (RA-GB) yielded a scattering angle in the observer plane of θscat = 0.7 mas. An analysis of the time-frequency correlation function for weak scintillations yielded an angle of refraction in the direction to the pulsar θref, 0 = 110 ms and a distance to the prism zprism ≤ 2 pc.

A search for transit timing variations and orbital decay in WASP-46b

Science.gov (United States)

Petrucci, R.; Jofré, E.; Ferrero, L. V.; Cúneo, V.; Saker, L.; Lovos, F.; Gómez, M.; Mauas, P.

2018-02-01

We present 12 new transit observations of the exoplanet WASP-46b obtained with the 1.54-m telescope at Estación Astrofísica de Bosque Alegre (EABA, Argentina) and the 0.40-m Horacio Ghielmetti and 2.15-m Jorge Sahade telescopes at Complejo Astronómico El Leoncito (CASLEO, Argentina). We analyse them together with 37 light curves from the literature to re-determine the physical parameters and search for additional planets via transit timing variations (TTVs). We consider the 31 transits with uncertainties in their mid-transit times (e_T0) activity could be affecting the measured mid-transit times. This value of dispersion allows us to rule out the presence of additional bodies with masses larger than 2.3, 4.6, 7 and 9.3 M_{\\oplus} at the first-order mean-motion resonances 2:1, 3:2, 4:3 and 5:4 with the transiting planet, respectively. Despite the 6 yr baseline and a typical light-curve precision of 2 × 10-3, we find that we cannot significantly demonstrate a slow decrease of the orbital period of WASP-46b. We place a lower limit of Q⋆ > 7 × 103 on the tidal quality factor and determine that an additional 6 yr baseline is required to rule out Q⋆ < 105.

Ten years of SLR production in Argentina

Science.gov (United States)

Pacheco, A.; Podestá, R.; Yin, Z.; Liu, W.; Actis, E.; Adarvez, S.; Quinteros, J.; Podestá, F.

2017-07-01

SLR technique is a proved astro-geodetic art with a significant power to contribute to Earth and Space Sciences. Therefore, scientific applications of SLR System are able to perform multiple tasks in the fields of Astrometry, Geodesy and Geophysics. The results we show here were obtained from satellite observations made at SLR 7406 Station of Observatorio Astronómico Félix Aguilar (OAFA) in San Juan, Argentina. The telescope was installed early on 2006, in concordance with an International Cooperation Agreement between Universidad Nacional de San Juan, Argentina and Chinese Academy of Sciences. In this abstract we show the current research being done with ILRS 7406 station: Length of day (LOD) and Angular velocity of Earth Rotation, calculated weekly; Pole Motion. ILRS7406 is daily surveying Pole coordinates x and y; Tracking SLR to GNSS constellations. SLR System contributes to the adjustment and validation of satellite GALILEO, GPS, GLONASS, and BEIDOU orbits. Our station is nowadays member of the new ITRF 2014 frame, and these past years has been one of the 3 highest producing SLR Stations on the ILRS net, composed of about 40 stations distributed all around the world. The obtained results during this first 10 years of experience are useful to enhance the traditional collaboration between OAFA and international services such as ILRS, IERS and NASA.

LOFAR, the low frequency array

Science.gov (United States)

Vermeulen, R. C.

2012-09-01

LOFAR, the Low Frequency Array, is a next-generation radio telescope designed by ASTRON, with antenna stations concentrated in the north of the Netherlands and currently spread into Germany, France, Sweden and the United Kingdom; plans for more LOFAR stations exist in several other countries. Utilizing a novel, phased-array design, LOFAR is optimized for the largely unexplored low frequency range between 30 and 240 MHz. Digital beam-forming techniques make the LOFAR system agile and allow for rapid re-pointing of the telescopes as well as the potential for multiple simultaneous observations. Processing (e.g. cross-correlation) takes place in the LOFAR BlueGene/P supercomputer, and associated post-processing facilities. With its dense core (inner few km) array and long (more than 1000 km) interferometric baselines, LOFAR reaches unparalleled sensitivity and resolution in the low frequency radio regime. The International LOFAR Telescope (ILT) is now issuing its first call for observing projects that will be peer reviewed and selected for observing starting in December. Part of the allocations will be made on the basis of a fully Open Skies policy; there are also reserved fractions assigned by national consortia in return for contributions from their country to the ILT. In this invited talk, the gradually expanding complement of operationally verified observing modes and capabilities are reviewed, and some of the exciting first astronomical results are presented.

Progress in SLR-GPS co-location at San Juan (Argentina) station

Science.gov (United States)

Luis, Hernan; Rojas, Alvis; Adarvez, Sonia; Quinteros, Johana; Cobos, Pablo; Aracena, Andrés; Pacheco, Ana M.; Podestá, Ricardo; Actis, Eloy V.; Li, Jinzeng; Yin, Zhiqiang; Wang, Rui; Huang, Dongping; Márquez, Raúl

2012-08-01

From February, 2006, performing a Cooperation Agreement with National Astronomical Observatories of China (NAOC) of the Chinese Academy of Sciences (CAS), Observatorio Astronómico Félix Aguilar (OAFA) of Universidad Nacional de San Juan (UNSJ) is operating a SLR System (ILRS 7406 Station). From the beginning of 2012 a GPS Aztech - Micro Z CGRS is operative at the same place, which made the SLR - GPS co - location possible. The prior objective is to reach co - location between both techniques, so the Station became of 1st order in ITRF net. For that we study and adopt an appropriate strategy to select and place Survey Control Points that ensures higher precision in determination of 3D vectors between the selected reference point s. Afterwards we perform translocation tasks of receptor and antenna checking that the GPS verifies builder standards. Then we design and compensate survey control network, by means of software of our own draught. We expect to obtain definitive local ties with precision better than 3 mm, as suggested by IERS for co - located stations. There are very few stations with co - located spatial techniques in the Southern Hemisphere, so it is of great importance to have one in Argentina for improve our participation in IERS on the new realizations of ITRF from now on.

Mutual Events in the Uranian satellite system in 2007

Science.gov (United States)

Arlot, J. E.

2008-09-01

ones. The predictions of the mutual events has been made [5] and are also available at the web address: http://www.imcce.fr/phemu09. References [1] Laskar J., Jacobson R.A.. (1987) Astron. Astrophys, 188, 212-224. [2] Arlot J.E. et al. (2006) Astron. Astrophys., 456, 1173-1179. [3] Showalter M., Lissauer J. (2006) Science, 311, 973- 977. [4] Arlot J.E. (2008) Astron. Astrophys., 478, 285-298. [5] Arlot J.E. et al. (2008) Astron. Astrophys., 485, 293- 298.

Dynamical passage to approximate equilibrium shapes for spinning, gravitating rubble asteroids

Science.gov (United States)

Sharma, Ishan; Jenkins, James T.; Burns, Joseph A.

2009-03-01

Many asteroids are thought to be particle aggregates held together principally by self-gravity. Here we study — for static and dynamical situations — the equilibrium shapes of spinning asteroids that are permitted for rubble piles. As in the case of spinning fluid masses, not all shapes are compatible with a granular rheology. We take the asteroid to always be an ellipsoid with an interior modeled as a rigid-plastic, cohesion-less material with a Drucker-Prager yield criterion. Using an approximate volume-averaged procedure, based on the classical method of moments, we investigate the dynamical process by which such objects may achieve equilibrium. We first collapse our dynamical approach to its statical limit to derive regions in spin-shape parameter space that allow equilibrium solutions to exist. At present, only a graphical illustration of these solutions for a prolate ellipsoid following the Drucker-Prager failure law is available [Sharma, I., Jenkins, J.T., Burns, J.A., 2005a. Bull. Am. Astron. Soc. 37, 643; Sharma, I., Jenkins, J.T., Burns, J.A., 2005b. Equilibrium shapes of ellipsoidal soil asteroids. In: García-Rojo, R., Hermann, H.J., McNamara, S. (Eds.), Proceedings of the 5th International Conference on Micromechanics of Granular Media, vol. 1. A.A. Balkema, UK; Holsapple, K.A., 2007. Icarus 187, 500-509]. Here, we obtain the equilibrium landscapes for general triaxial ellipsoids, as well as provide the requisite governing formulae. In addition, we demonstrate that it may be possible to better interpret the results of Richardson et al. [Richardson, D.C., Elankumaran, P., Sanderson, R.E., 2005. Icarus 173, 349-361] within the context of a Drucker-Prager material. The graphical result for prolate ellipsoids in the static limit is the same as those of Holsapple [Holsapple, K.A., 2007. Icarus 187, 500-509] because, when worked out, his final equations will match ours. This is because, though the formalisms to reach these expressions differ, in statics

Maximum mass ratio of am CVn-type binary systems and maximum white dwarf mass in ultra-compact x-ray binaries (addendum - Serb. Astron. J. No. 183 (2011, 63

Directory of Open Access Journals (Sweden)

Arbutina B.

2012-01-01

Full Text Available We recalculated the maximum white dwarf mass in ultra-compact X-ray binaries obtained in an earlier paper (Arbutina 2011, by taking the effects of super-Eddington accretion rate on the stability of mass transfer into account. It is found that, although the value formally remains the same (under the assumed approximations, for white dwarf masses M2 >~0.1MCh mass ratios are extremely low, implying that the result for Mmax is likely to have little if any practical relevance.

OPTICAL SPECTROSCOPIC OBSERVATIONS OF GAMMA-RAY BLAZAR CANDIDATES. VI. FURTHER OBSERVATIONS FROM TNG, WHT, OAN, SOAR, AND MAGELLAN TELESCOPES

Energy Technology Data Exchange (ETDEWEB)

Álvarez Crespo, N.; Massaro, F. [Dipartimento di Fisica, Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino (Italy); Milisavljevic, D.; Paggi, A.; Smith, Howard A. [Harvard—Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Landoni, M. [INAF-Osservatorio Astronomico di Brera, Via Emilio Bianchi 46, I-23807 Merate (Italy); Chavushyan, V.; Patiño-Álvarez, V. [Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51-216, 72000 Puebla, México (Mexico); Masetti, N. [INAF—Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, I-40129, Bologna (Italy); Jiménez-Bailón, E. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 877, Ensenada, 22800 Baja California, México (Mexico); Strader, J.; Chomiuk, L. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Katagiri, H.; Kagaya, M. [College of Science, Ibaraki University, 2-1-1, Bunkyo, Mito 310-8512 (Japan); Cheung, C. C. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); D’Abrusco, R. [Department of Physical Sciences, University of Napoli Federico II, via Cinthia 9, I-80126 Napoli (Italy); Ricci, F.; La Franca, F. [Dipartimento di Matematica e Fisica, Università Roma Tre, via della Vasca Navale 84, I-00146, Roma (Italy); and others

2016-04-15

Blazars, one of the most extreme classes of active galaxies, constitute so far the largest known population of γ-ray sources, and their number is continuously growing in the Fermi catalogs. However, in the latest release of the Fermi catalog there is still a large fraction of sources that are classified as blazar candidates of uncertain type (BCUs) for which optical spectroscopic observations are necessary to confirm their nature and their associations. In addition, about one-third of the γ-ray point sources listed in the Third Fermi-LAT Source Catalog (3FGL) are still unassociated and lacking an assigned lower-energy counterpart. Since 2012 we have been carrying out an optical spectroscopic campaign to observe blazar candidates to confirm their nature. In this paper, the sixth of the series, we present optical spectroscopic observations for 30 γ-ray blazar candidates from different observing programs we carried out with the Telescopio Nazionale Galileo, William Herschel Telescope, Observatorio Astronómico Nacional, Southern Astrophysical Research Telescope, and Magellan Telescopes. We found that 21 out of 30 sources investigated are BL Lac objects, while the remaining targets are classified as flat-spectrum radio quasars showing the typical broad emission lines of normal quasi-stellar objects. We conclude that our selection of γ-ray blazar candidates based on their multifrequency properties continues to be a successful way to discover potential low-energy counterparts of the Fermi unidentified gamma-ray sources and to confirm the nature of BCUs.

A wide and collimated radio jet in 3C84 on the scale of a few hundred gravitational radii

Science.gov (United States)

Giovannini, G.; Savolainen, T.; Orienti, M.; Nakamura, M.; Nagai, H.; Kino, M.; Giroletti, M.; Hada, K.; Bruni, G.; Kovalev, Y. Y.; Anderson, J. M.; D'Ammando, F.; Hodgson, J.; Honma, M.; Krichbaum, T. P.; Lee, S.-S.; Lico, R.; Lisakov, M. M.; Lobanov, A. P.; Petrov, L.; Sohn, B. W.; Sokolovsky, K. V.; Voitsik, P. A.; Zensus, J. A.; Tingay, S.

2018-04-01

Understanding the formation of relativistic jets in active galactic nuclei remains an elusive problem1. This is partly because observational tests of jet formation models suffer from the limited angular resolution of ground-based very-long-baseline interferometry that has thus far been able to probe the structure of the jet acceleration and collimation region in only two sources2,3. Here, we report observations of 3C84 (NGC 1275)—the central galaxy of the Perseus cluster—made with an interferometric array including the orbiting radio telescope of the RadioAstron4 mission. The data transversely resolve the edge-brightened jet in 3C84 only 30 μas from the core, which is ten times closer to the central engine than was possible in previous ground-based observations5 and allows us to measure the jet collimation profile from 102 to 104 gravitational radii (rg) from the black hole. The previously found5, almost cylindrical jet profile on scales larger than a few thousand rg is seen to continue at least down to a few hundred rg from the black hole, and we find a broad jet with a transverse radius of ≳250 rg at only 350 rg from the core. This implies that either the bright outer jet layer goes through a very rapid lateral expansion on scales ≲102 rg or it is launched from the accretion disk.

New Insights into the Structure, Origin, and Evolution of Pluto and Charon

Science.gov (United States)

McKinnon, W. B.; Stern, A.; Weaver, H. A., Jr.; Spencer, J. R.; Nimmo, F.; Lisse, C. M.; Umurhan, O. M.; Moore, J. M.; Buie, M. W.; Porter, S.; Olkin, C.; Young, L. A.; Ennico Smith, K.

2015-12-01

The July 2015 New Horizons flyby has removed a long-standing obstacle to understanding the cosmogony of the Pluto-Charon system: the uncertain radius of Pluto. Combined with precise astrometric fits to the barycenter of the Pluto-Charon binary from HST observations of the more distant, small satellites (M. Brozović et al., Icarus 246, 317-329, 2015), the densities of both Pluto and Charon are now known. At the 10% level, the densities of Pluto and Charon are rather similar, as opposed to the more divergent density estimates of years past in which Charon was thought to be substantially icier. In the context of a giant impact origin for binaries, a rock-poor Charon corresponds to an iron-poor Moon in the terrestrial case, with differentiated precursors being implied in both cases. A rock-rich Charon, however, implies that the precursor impacting bodies were at most only partially differentiated — possessing relatively thin ice shells (R.M. Canup, Astron. J. 141, 35, 2011). This suggests some combination of relatively slow and/or late accretion in the ancestral Kuiper belt. A more rock-rich Charon also implies a more vigorous geological history, all other things being equal. For Pluto, the evolution to the surface of a substantial mass of supervolatile ices increases the likelihood that internal volatiles such as ammonia and methanol have been sequestered in an internal, aqueous layer (or ocean).

Applicability of meteor radiant determination methods depending on orbit type. I. High-eccentric orbits

Science.gov (United States)

Svoren, J.; Neslusan, L.; Porubcan, V.

1993-07-01

It is evident that there is no uniform method of calculating meteor radiants which would yield reliable results for all types of cometary orbits. In the present paper an analysis of this problem is presented, together with recommended methods for various types of orbits. Some additional methods resulting from mathematical modelling are presented and discussed together with Porter's, Steel-Baggaley's and Hasegawa's methods. In order to be able to compare how suitable the application of the individual radiant determination methods is, it is necessary to determine the accuracy with which they approximate real meteor orbits. To verify the accuracy with which the orbit of a meteoroid with at least one node at 1 AU fits the original orbit of the parent body, we applied the Southworth-Hawkins D-criterion (Southworth, R.B., Hawkins, G.S.: 1963, Smithson. Contr. Astrophys 7, 261). D0.2 the fit is rather poor and the change of orbit unrealistic. The optimal methods with the smallest values of D for given types of orbits are shown in two series of six plots. The new method of rotation around the line of apsides we propose is very appropriate in the region of small inclinations. There is no doubt that Hasegawa's omega-adjustment method (Hasegawa, I.: 1990, Publ. Astron. Soc. Japan 42, 175) has the widest application. A comparison of the theoretical radiants with the observed radiants of seven known meteor showers is also presented.

Determinación de miembros, binaridad y metalicidad de gigantes rojas en el cúmulo abierto de edad intermedia NGC 2354

Science.gov (United States)

Clariá, J. J.; Mermilliod, J. C.; Piatti, A. E.

We present new Coravel radial-velocity observations and photoelectric photometry in the UBV, DDO and Washington systems for a sample of red giant candidates in the field of the intermediate-age open cluster NGC 2354. Photometric membership probabilities show very good agrement with those obtained from Coravel radial velocities. The analysis of the photometric and kinematical data allow us to confirm cluster membership for 9 red giants, one of them being a spectroscopic binary, while 4 confirmed spectroscopic binaries appear to be probable members. We have also discovered 4 spectroscopic binaries not belonging to the cluster. A mean radial velocity of (33.40±0.27)km s-1 and a mean reddening E(B-V)= 0.13±0.03 were derived for the cluster giants. NGC 2354 has a mean ultraviolet excess =-0.03±0.01, relative to the field K giants, and a mean new cyanogen anomaly ΔCN=-0.035±0.007, both implying [Fe/H]≈-0.3. The moderately metal-poor character of NGC 2354 is confirmed using five different metal abundance indicators of the Washington system. The cluster giant branch is formed by a well defined clump of 7 stars and 4 stars with high membership probabilities seem to define an ascending giant branch. The whole red giant locus cannot be reproduced by any theoretical track. This paper will appear in Astron. & Astrophys. Suppl. (1999).

Design of VLBI Array in South America

Science.gov (United States)

Carrara, E. A.; Abraham, Z.

1990-11-01

RESUMEN. Estudiamos la localizaci6n 6ptima de estaciones de \\ ras' en territorlo brasileno. Con una red VLBI de estaciones reales y ficti- cias simulamos observaciones. Se usan los datos generados de estps ex- perimentos para obtener Ia distribuci6n de brillo de radiofuentes fic- ticias por medlo de tecaicas de mapeo bIbrido. Se concluye que l mejor localizaci6n de estacionee'VLBI futuras, tomando en cuenta las estacio- nes de EUA y de Europa, se encuentra en el Norte-Noreste de razll. El analisis de los datos se hizo con los programas de CALTECH, los cuales estan instalados en una computadora VAX del Departamento de Astronomla del Instituto Astron6mico y Geoflsico de la Universidad de Sa"'o Paulo. ABSTRACT: In this work we study the optimum localization for future VLBI stations in the Brazilian territory. With a VLBI network of real and fictitious stations we make simulations of observations. The data generated in these experiments are used to obtain brightness distribution of a fictitious radio source by the hybrid mapping techniques. We conclude that the best localization of a future VLBI station taking into account the addition of US and European Stations, is roughly in North-Northeast sites in Brazil. The analysis of the data is made with the software of CALTECH, which is installed in the VAX computer of the Astronomy Department of Instituto e Geofisico - USP. Key `{` : INSTRUMENTS - INTERFEROMETRY

Apoastron shift constraints on dark matter distribution at the Galactic Center

International Nuclear Information System (INIS)

Zakharov, A. F.; Nucita, A. A.; De Paolis, F.; Ingrosso, G.

2007-01-01

The existence of dark matter (DM) at scales of a few parsecs down to ≅10 -5 pc around the centers of galaxies and, in particular, in the Galactic Center region has been considered in the literature. Under the assumption that such a DM clump, principally constituted by nonbaryonic matter (like weakly interacting massive particles) does exist at the center of our galaxy, the study of the γ-ray emission from the Galactic Center region allows us to constrain both the mass and the size of this DM sphere. Further constraints on the DM distribution parameters may be derived by observations of bright infrared stars around the Galactic Center. Hall and Gondolo [J. Hall and P. Gondolo, Phys. Rev. D 74, 063511 (2006)] used estimates of the enclosed mass obtained in various ways and tabulated by Ghez et al. [A. M. Ghez et al., Astron. Nachr. 324, 527 (2003); A. M. Ghez et al., Astrophys. J. 620, 744 (2005)]. Moreover, if a DM cusp does exist around the Galactic Center it could modify the trajectories of stars moving around it in a sensible way depending on the DM mass distribution. Here, we discuss the constraints that can be obtained with the orbit analysis of stars (as S2 and S16) moving inside the DM concentration with the present and next generations of large telescopes. In particular, consideration of the S2 star apoastron shift may allow improving limits on the DM mass and size

Comparison of pressure profiles of massive relaxed galaxy clusters using the Sunyaev-Zel'dovich and x-ray data

International Nuclear Information System (INIS)

Bonamente, Massimiliano; Hasler, Nicole; Bulbul, Esra; Landry, David; Carlstrom, John E; Culverhouse, Thomas L; Gralla, Megan; Greer, Christopher; Hennessy, Ryan; Leitch, Erik M; Plagge, Thomas; Pryke, Clem; Hawkins, David; Lamb, James W; Muchovej, Stephen; Joy, Marshall; Kolodziejczak, Jeffery; Marrone, Daniel P; Miller, Amber; Mroczkowski, Tony

2012-01-01

We present the Sunyaev-Zel'dovich (SZ) effect observations of a sample of 25 massive relaxed galaxy clusters observed with the Sunyaev-Zel'dovich array (SZA), an eight-element interferometer that is part of the Combined Array for Research in Millimeter-wave Astronomy (CARMA). We performed an analysis of new SZA data and archival Chandra observations of this sample to investigate the integrated pressure—a proxy for cluster mass—determined from x-ray and SZ observations, two independent probes of the intra-cluster medium (ICM). This analysis makes use of a model for the ICM introduced by Bulbul (2010 Astrophys. J. 720 1038) which can be applied simultaneously to the SZ and x-ray data. With this model, we estimated the pressure profile for each cluster using a joint analysis of the SZ and x-ray data, and using the SZ data alone. We found that the integrated pressures measured from the x-ray and SZ data are consistent. This conclusion is in agreement with recent results obtained using WMAP and Planck data, confirming that SZ and x-ray observations of massive clusters detect the same amount of thermal pressure from the ICM. To test for possible biases introduced by our choice of model, we also fitted the SZ data using the universal pressure profile proposed by Arnaud (2010 Astron. Astrophys. 517 A92) and found consistency between the two models out to r 500 in the pressure profiles and integrated pressures. (paper)

Observações no âmbito dos "additional programs" do satélite COROT

Science.gov (United States)

Janot Pacheco, E.

2003-08-01

O satélite Fraco-europeu COROT fará fotometria de altissima precisão (pretende-se atingir uma parte em um milhão), grande campo (3x3 graus) e por longos períodos, de duas regiões pré-determinadas do céu, com 10 graus de raio. Suas finalidades básicas serão estudos em sismologia estelar e a procura de exoplanetas. A comunidade astronômica brasileira participará dessa missão espacial, com direitos iguais aos dos parceiros europeus. Isso se deve a que o satélite utilizará a estação de recepção de dados de Natal (INPE), 5 a 6 brasileiros participarão das equipes de software e cientistas do país atuarão na fase de pré-lançamento. Apresentamos nesta comunicação sugestões para a preparação de propostas de observações com COROT, no âmbito dos Programas Adicionais, que contemplam outros projetos que não de sismologia ou exoplanetas. As últimas definições técnicas e decisões tomadas na 4th Corot Week de junho último serão igualmente apresentadas, em particular quanto às regiões de observação escolhidas e quanto aos procedimentos a seguir para se propor observações.

Fluctuaciones interanuales a multidecádicas de la temperatura de verano en el centro-oeste de Argentina y procesos atmosféricos/oceánicos/astronómicos globales

Directory of Open Access Journals (Sweden)

Eduardo Andres Agosta

2008-12-01

Full Text Available La temperatura estival (octubre-marzo en la región Centro-Oeste de Argentina (COA, 28°-36°S y 65°-70°O tiene un comportamiento espacial coherente y temporal en fase, en escalas interanuales a interdecádicas (Agosta y otros 2004. Se encuentra que la temperatura del aire presenta cuasi-oscilaciones significativas en las bandas de 11 años y 18 años aproximadamente. La primera se vincula al forzante solar, la segunda, a los efectos de la transición climática de 1976/77 (IPCC, 2001. Esta transición afectó transitoriamente la variabilidad de baja frecuencia de la temperatura como fenómeno de interferencia sobre el cuasi-ciclo solar de 11 años dominante.The summer (Oct-Mar temperature in Central-West Argentina (CWA, 28°-36°S y 65°-70°W shows a behaviour spatially coherent and temporally in phase at interannual to interdecadal scales. (Agosta et al. 2004. It is found the air temperature shows significant cuasi-oscillations in the spectral bands of roughly 11-yr. and 18- yr. The former is linked to the solar forcing, the latter to the effects of the climate transition of the summer 1976/77 (IPCC 2001. This transition transitorily affected the low-frequency variability of the temperature as an interference phenomenon upon the cuasi-11-yr.-solar cycle domain.

Polarimetric purity and the concept of degree of polarization

Science.gov (United States)

Gil, José J.; Norrman, Andreas; Friberg, Ari T.; Setälä, Tero

2018-02-01

The concept of degree of polarization for electromagnetic waves, in its general three-dimensional version, is revisited in the light of the implications of the recent findings on the structure of polarimetric purity and of the existence of nonregular states of polarization [J. J. Gil et al., Phys Rev. A 95, 053856 (2017), 10.1103/PhysRevA.95.053856]. From the analysis of the characteristic decomposition of a polarization matrix R into an incoherent convex combination of (1) a pure state Rp, (2) a middle state Rm given by an equiprobable mixture of two eigenstates of R, and (3) a fully unpolarized state Ru -3 D, it is found that, in general, Rm exhibits nonzero circular and linear degrees of polarization. Therefore, the degrees of linear and circular polarization of R cannot always be assigned to the single totally polarized component Rp. It is shown that the parameter P3 D proposed formerly by Samson [J. C. Samson, Geophys. J. R. Astron. Soc. 34, 403 (1973), 10.1111/j.1365-246X.1973.tb02404.x] takes into account, in a proper and objective form, all the contributions to polarimetric purity, namely, the contributions to the linear and circular degrees of polarization of R as well as to the stability of the plane containing its polarization ellipse. Consequently, P3 D constitutes a natural representative of the degree of polarimetric purity. Some implications for the common convention for the concept of two-dimensional degree of polarization are also analyzed and discussed.

Frozen-wave instability in near-critical hydrogen subjected to horizontal vibration under various gravity fields.

Science.gov (United States)

Gandikota, G; Chatain, D; Amiroudine, S; Lyubimova, T; Beysens, D

2014-01-01

The frozen-wave instability which appears at a liquid-vapor interface when a harmonic vibration is applied in a direction tangential to it has been less studied until now. The present paper reports experiments on hydrogen (H2) in order to study this instability when the temperature is varied near its critical point for various gravity levels. Close to the critical point, a liquid-vapor density difference and surface tension can be continuously varied with temperature in a scaled, universal way. The effect of gravity on the height of the frozen waves at the interface is studied by performing the experiments in a magnetic facility where effective gravity that results from the coupling of the Earth's gravity and magnetic forces can be varied. The stability diagram of the instability is obtained. The experiments show a good agreement with an inviscid model [Fluid Dyn. 21 849 (1987)], irrespective of the gravity level. It is observed in the experiments that the height of the frozen waves varies weakly with temperature and increases with a decrease in the gravity level, according to a power law with an exponent of 0.7. It is concluded that the wave height becomes of the order of the cell size as the gravity level is asymptotically decreased to zero. The interface pattern thus appears as a bandlike pattern of alternate liquid and vapor phases, a puzzling phenomenon that was observed with CO2 and H2 near their critical point in weightlessness [Acta Astron. 61 1002 (2007); Europhys. Lett. 86 16003 (2009)].

What We Know Now: Synthesis for Understanding the Origin of the Pluto System

Science.gov (United States)

McKinnon, William B.; Stern, S. A.; Weaver, H. A.; Spencer, J. R.; Nimmo, F.; Lisse, C. M.; Umurhan, O. M.; Moore, J. M.; Buie, M. W.; Porter, S. B.; Olkin, C. B.; Young, L. A.; Ennico, K.

2015-11-01

The July 2015 New Horizons flyby has removed a long-standing obstacle to understanding the cosmogony of the Pluto-Charon system: the uncertain radius of Pluto. Combined with precise astrometric fits to the barycenter of the Pluto-Charon binary from HST observations of the more distant, small satellites (Brozovic et al., Icarus 246, 317-329, 2015), the densities of both Pluto and Charon are now known. At the 10% level, these densities are rather similar, as opposed to the more divergent density estimates of years past in which Charon was thought to be substantially icier. In the context of a “giant impact” origin, a rock-rich Charon implies that the precursor impacting bodies were at most only partially differentiated — possessing relatively thin ice shells (Canup, Astron. J. 141, 35, 2011). This suggests some combination of relatively slow and/or late accretion in the ancestral Kuiper belt. New Horizons has also shown that Nix and Hydra possess high albedos, consistent with ice-dominated compositions. Such compositions are consistent with a giant impact origin in which one or both precursor impacting bodies were partially differentiated, so that the small satellites ultimately formed from material ejected from ice-dominated surface layers (Peale and Canup, Treatise on Geophysics, 2nd Ed., chapter 10.17, 2015). We examine whether Pluto and Charon could actually possess the same bulk rock/ice ratio and whether this would allow for an alternate, non-giant-impact origin for the Pluto system.This work was supported by NASA's New Horizons project.

The nature of 50 Palermo Swift-BAT hard X-ray objects through optical spectroscopy

Science.gov (United States)

Rojas, A. F.; Masetti, N.; Minniti, D.; Jiménez-Bailón, E.; Chavushyan, V.; Hau, G.; McBride, V. A.; Bassani, L.; Bazzano, A.; Bird, A. J.; Galaz, G.; Gavignaud, I.; Landi, R.; Malizia, A.; Morelli, L.; Palazzi, E.; Patiño-Álvarez, V.; Stephen, J. B.; Ubertini, P.

2017-06-01

We present the nature of 50 hard X-ray emitting objects unveiled through an optical spectroscopy campaign performed at seven telescopes in the northern and southern hemispheres. These objects were detected with the Burst Alert Telescope (BAT) instrument onboard the Swift satellite and listed as of unidentified nature in the 54-month Palermo BAT catalogue. In detail, 45 sources in our sample are identified as active galactic nuclei of which, 27 are classified as type 1 (with broad and narrow emission lines) and 18 are classified as type 2 (with only narrow emission lines). Among the broad-line emission objects, one is a type 1 high-redshift quasi-stellar object, and among the narrow-line emission objects, one is a starburst galaxy, one is a X-ray bright optically normal galaxy, and one is a low ionization nuclear emission line region. We report 30 new redshift measurements, 13 confirmations and 2 more accurate redshift values. The remaining five objects are galactic sources: three are Cataclismic Variables, one is a X-ray Binary probably with a low mass secondary star, and one is an active star. Based on observations obtained from the following observatories: Cerro Tololo Interamerican Observatory (Chile); Astronomical Observatory of Bologna in Loiano (Italy); Observatorio Astronómico Nacional (San Pedro Mártir, Mexico); Radcliffe telescope of the South African Astronomical Observatory (Sutherland, South Africa); Sloan Digital Sky Survey; Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (Canary Islands, Spain) and New Technology Telescope (NTT) of La Silla Observatory, Chile.

Solaris: a global network of autonomous observatories in the southern hemisphere

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Kozłowski, S. K.; Sybilski, P.; Konacki, Maciej; Pawłaszek, R. K.; Ratajczak, Milena; Helminiak, K. G.

2014-07-01

We present Project Solaris, a network of four autonomous observatories in the Southern Hemisphere. The Project's primary goal is to detect and characterize circumbinary planets using the eclipse timing approach. This method requires high-cadence and long time-span photometric coverage of the binaries' eclipses, hence the observatories are located at sites having similar separation in longitude and nearly identical latitudes: South African Astronómical Observatory, Republic of South Africa (Solaris-1 and -2), Siding Spring Observatory, Australia (Solaris-3) and Complejo Astronomico El Leoncito, Argentina (Solaris-4). The headquarters coordinating and monitoring the network is based in Toruń, Poland. All four sites are operational as of December 2013. The instrument and hardware configurations are nearly identical. Each site is equipped with a 0.5-m Ritchey-Chrétien or Schmidt-Cassegrain optical tube assembly mounted on a direct-drive modified German equatorial mount along with a set of instruments. Computer, power and networking components are installed in rack cabinets. Everything is housed in sandwiched fiberglass clamshell 3.5-m diameter robotized domes. The Argentinian site is additionally equipped with a 20-ft office container. We discuss the design requirements of robotic observatories aimed to operate autonomously as a global network with concentration on efficiency, robustness and modularity. We also present a newly introduced spectroscopic mode of operation commissioned on the Solaris-1 telescope. Using a compact échelle spectrograph (20 000 resolution) mounted directly on the imaging train of the telescope, we are able to remotely acquire spectra. A fully robotic spectroscopic mode is planned for 2015.

Museo Arqueológico de Petroglifos y el fomento del turismo en Venezuela

Directory of Open Access Journals (Sweden)

Yamile Delgado De Smith

2005-11-01

Full Text Available El Complejo Arqueológico de Vigirima (Venezuela es el mayor yacimiento de Petroglifos de América y el único lugar continental que presenta alineamientos megalíticos. Sin embargo, es poco conocido y ha sido aún menos estudiado, quedando a la saga de los proyectos de conservación y preservación patrimonial emprendidos por los organismos supranacionales. Se efectuó un registro sistemático y la clasificación estilística de los glifos y caracteres pétreos del complejo arqueológico de Vigirima. El análisis de las técnicas de elaboración, del substrato y su distribución espacio temporal muestran que los mismos fueron elaborados con diversos grados de especificidad por los grupos humanos que crearon estas expresiones de arte rupestre. Los contenidos y estilos informan sobre una sociedad en estrecha dependencia y en equilibrio frente a la naturaleza, en cuya organización tribal, de carácter igualitario, tendría un rol importante: el Chaman como mediador hombre-naturaleza y la mujer como símbolo de la reproducción de la fuerza humana de trabajo. Se presentan, adicionalmente, elementos contextuales que permiten datar la antigüedad del yacimiento y las tradiciones míticas de carácter mágico-religioso o astronómico, que pudieron motivarlo y finalmente se proponen alternativas para su conservación y el fomento del turismo.

Discovery of a [WO] central star in the planetary nebula Th 2-A

Science.gov (United States)

Weidmann, W. A.; Gamen, R.; Díaz, R. J.; Niemela, V. S.

2008-09-01

Context: About 2500 planetary nebulae are known in our Galaxy but only 224 have central stars with reported spectral types in the Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (Acker et al. 1992; Acker et al. 1996). Aims: We have started an observational program aiming to increase the number of PN central stars with spectral classification. Methods: By means of spectroscopy and high resolution imaging, we identify the position and true nature of the central star. We carried out low resolution spectroscopic observations at CASLEO telescope, complemented with medium resolution spectroscopy performed at Gemini South and Magellan telescopes. Results: As a first outcome of this survey, we present for the first time the spectra of the central star of the PN Th 2-A. These spectra show emission lines of ionized C and O, typical in Wolf-Rayet stars. Conclusions: We identify the position of that central star, which is not the brightest one of the visual central pair. We classify it as of type [WO 3]pec, which is consistent with the high excitation and dynamical age of the nebula. Based on data collected at (i) the Complejo Astronómico El Leoncito (CASLEO), which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina y Universidades Nacionales de La Plata, Córdoba y San Juan, Argentina; (ii) the 6.5 m Magellan Telescopes at Las Campanas Observatory, Chile; (iii) the 8 m Gemini South Telescope, Chile.

Inclined asymmetric librations in exterior resonances

Science.gov (United States)

Voyatzis, G.; Tsiganis, K.; Antoniadou, K. I.

2018-04-01

Librational motion in Celestial Mechanics is generally associated with the existence of stable resonant configurations and signified by the existence of stable periodic solutions and oscillation of critical (resonant) angles. When such an oscillation takes place around a value different than 0 or π , the libration is called asymmetric. In the context of the planar circular restricted three-body problem, asymmetric librations have been identified for the exterior mean motion resonances (MMRs) 1:2, 1:3, etc., as well as for co-orbital motion (1:1). In exterior MMRs the massless body is the outer one. In this paper, we study asymmetric librations in the three-dimensional space. We employ the computational approach of Markellos (Mon Not R Astron Soc 184:273-281, https://doi.org/10.1093/mnras/184.2.273, 1978) and compute families of asymmetric periodic orbits and their stability. Stable asymmetric periodic orbits are surrounded in phase space by domains of initial conditions which correspond to stable evolution and librating resonant angles. Our computations were focused on the spatial circular restricted three-body model of the Sun-Neptune-TNO system (TNO = trans-Neptunian object). We compare our results with numerical integrations of observed TNOs, which reveal that some of them perform 1:2 resonant, inclined asymmetric librations. For the stable 1:2 TNO librators, we find that their libration seems to be related to the vertically stable planar asymmetric orbits of our model, rather than the three-dimensional ones found in the present study.

Cassini ISS Observations of Jupiter: An Exoplanet Perspective

Science.gov (United States)

West, Robert A.; Knowles, Benjamin

2017-10-01

Understanding the optical and physical properties of planets in our solar system can guide our approach to the interpretation of observations of exoplanets. Although some work has already been done along these lines, there remain low-hanging fruit. During the Cassini Jupiter encounter, the Imaging Science Subsystem (ISS) obtained an extensive set of images over a large range of phase angles (near-zero to 140 degrees) and in filters from near-UV to near-IR, including three methane bands and nearby continuum. The ISS also obtained images using polarizers. Much later in the mission we also obtained distant images while in orbit around Saturn. Some of these data have already been studied to reveal phase behavior (Dyudina et al., Astrophys. J.822, DOI: 10.3847/0004-637X/822/2/76; Mayorga et al., 2016, Astron. J. 152, DOI: 10.3847/0004-6256/152/6/209). Here we examine rotational modulation to determine wavelength and phase angle dependence, and how these may depend on cloud and haze vertical structure and optical properties. The existence of an optically thin forward-scattering and longitudinally-homogeneous haze overlying photometrically-variable cloud fields tends to suppress rotational modulation as phase angle increases, although in the strong 890-nm methane band cloud vertical structure is important. Cloud particles (non-spherical ammonia ice, mostly) have very small polarization signatures at intermediate phase angles and rotational modulation is not apparent above the noise level of our instrument. Part of this work was performed by the Jet Propulsion Lab, Cal. Inst. Of Technology.

South American regional ionospheric maps computed by GESA: A pilot service in the framework of SIRGAS

Science.gov (United States)

Brunini, C.; Meza, A.; Gende, M.; Azpilicueta, F.

2008-08-01

SIRGAS (Geocentric Reference Frame for the Americas) is an international enterprise of the geodetic community that aims to realize the Terrestrial Reference Frame in the America's countries. In order to fulfill this commitment, SIRGAS manages a network of continuously operational GNSS receivers totalling around one hundred sites in the Caribbean, Central, and South American region. Although the network was not planed for ionospheric studies, its potential to be used for such a purpose was recently recognized and SIRGAS started a pilot experiment devoted to establish a regular service for computing and releasing regional vertical TEC (vTEC) maps based on GNSS data. Since July, 2005, the GESA (Geodesia Espacial y Aeronomía) laboratory belonging to the Facultad de Ciencias Astronómicas y Geofísicas of the Universidad Nacional de La Plata computes hourly maps of vertical Total Electron Content (vTEC) in the framework of the SIRGAS pilot experiment. These maps exploit all the GNSS data available in the South American region and are computed with the LPIM (La Plata Ionospheric Model). LPIM implements a de-biasing procedure that improves data calibration in relation to other procedures commonly used for such purposes. After calibration, slant TEC measurements are converted to vertical and mapped using local-time and modip latitude. The use of modip latitude smoothed the spatial variability of vTEC, especially in the South American low latitude region and hence allows for a better vTEC interpolation. This contribution summarizes the results obtained by GESA in the framework of the SIRGAS pilot experiment.

Espectroscopía Espacial en el IR-Lejano

Science.gov (United States)

Goicoechea, Javier R.; Cernicharo, J.

Debido a la opacidad atmosférica, el dominio IR--lejano del espectro electromagnético ha sido la última ventana en ser utilizada por la Astrofísica Molecular. El potencial que supone abrir este nuevo rango de frecuencias a través de la espectroscopía molecular ha comenzado a ser explotado con el Infrared Space Observatory (ISO). La sensibilidad de la instrumentación embarcada en dicho satélite no tiene comparación alguna con las escasas misiones espaciales, o a bordo de aviones, realizadas con anterioridad a su lanzamiento. En particular, casi todo el rango operativo de ISO en el IR--lejano no había sido explorado. El espectro IR--lejano de las fuentes más representativas de la galaxia era desconocido y los principales emisores de radiación, las moléculas, estaban por identificar. Las observaciones en el IR--lejano están especialmente indicadas para el estudio del gas caliente en las nubes moleculares del medio interestelar y en el interior de las envolturas circunestelares alrededor de estrellas evolucionadas. Algunas de estas fuentes; Sgr B2 en el Centro Galáctico y las Proto--Nebulosas Planetarias, constituyen uno de los objetos más paradigmáticos en nuestra comprensión de la complejidad química de La Galaxia. En esta contribución se presentan los resultados espectroscópicos más importantes de algunas de estas fuentes astronómicas.

Precision mechanisms for optics in a vacuum cryogenic environment

Science.gov (United States)

Navarro, R.; Elswijk, E.; Tromp, N.; Kragt, J.; Kroes, G.; Hanenburg, H.; de Haan, M.; Schuil, M.; Teuwen, M.; Janssen, H.; Venema, L.

2017-11-01

To achieve superb stability in cryogenic optical systems, NOVA-ASTRON generally designs optical instruments on the basis of a 'no adjustments' philosophy. This means that in principle no corrections are possible after assembly. The alignment precision and consequently the performance of the instrument is guaranteed from the design, the tolerance analysis and the detailed knowledge of the material behavior and manufacturing process. This resulted in a higher degree of integrated optomechanical-cryogenic design with fewer parts, but with a higher part complexity. The 'no adjustments' strategy is successful because in the end the risk on instrument performance and project delays is much reduced. Astronomical instrument specifications have become more challenging over the years. Recent designs of the European Southern Observatory Very Large Telescope Interferometer (ESO VLTI) 4 Telescope combiner MATISSE include hundreds of optical components in a cryogenic environment. Despite the large number of optical components the alignment accuracy and stability requirements are in the order of nanometers. The 'no adjustments' philosophy would be too costly in this case, because all components would need to meet extremely tight manufacturing specifications. These specifications can be relaxed dramatically if cryogenic mechanisms are used for alignment. Several mechanisms have been developed: a tip-tilt mirror mechanism, an optical path distance mechanism, a slider mechanism, a bistable cryogenic shutter and a mirror mounting clip. Key aspects of these mechanisms are that the optical element and mechanism are combined in a compact single component, driven by e.g. self braking piezo actuators in order to hold position without power. The design, realization and test results of several mechanisms are presented in this paper.

Volatile Transport on Pluto: First Results from the 2013 Observing Season

Science.gov (United States)

Buratti, B. J.; Dalba, P. A.; Hicks, M.; Chu, D.; O'Neill, A.; Chesley, J. P.

2013-12-01

With the New Horizons spacecraft due to encounter Pluto in slightly less than two years, close scrutiny of this dwarf ice planet has begun in earnest. Ground-based observations are especially critical for context and for a larger temporal excursion. Seasonal transport of volatiles should occur on Pluto, and this transport should be detectable through changes in its rotational light curve, once all variations due to viewing geometry have been modeled. Giving the steady increase observed in Pluto's atmospheric pressure over the past two decades, associated sublimation of frost from the surface has likely occurred, as predicted by volatile transport models. Rotational light curves of Pluto through time have been created for static frost models based on images from the Hubble Space Telescope. These models, which account for changes in viewing geometry, have been compared with observed light curves obtained between 1950 and 2013. No evidence for transport was evident prior to 2000. Observations from 2002 (Buie et al., 2010, Astron. J. 139, 1128) and 2007-2008 (Hicks et al. 2008, B.A.A.S. 40, 460) suggest changes in the frost pattern on Pluto's surface. New observations of Pluto's light curve from the 2013 season from Table Mountain Observatory show no evidence for the large transport of volatiles on Pluto's surface. Our data are the first measurement of a large opposition surge on Pluto similar to that seen on other icy bodies. Both Buie et al. (2010) and our observations from the 2012-2013 seasons show that Pluto is becoming more red in color. This observation makes sense if nitrogen is being removed from the surface to uncover a red, photolyzed substrate of methane. Funded by NASA.

Distribution functions for a family of general-relativistic hypervirial models in the collisionless regime

Science.gov (United States)

Gauy, Henrique Matheus; Ramos-Caro, Javier

2018-03-01

By considering the Einstein-Vlasov system for static spherically symmetric distributions of matter, we show that configurations with constant anisotropy parameter β , leading to asymptotically flat spacetimes, have necessarily a distribution function (DF) of the form F =l-2 βξ (ɛ ) , where ɛ =E /m and l =L /m are the relativistic energy and angular momentum per unit rest mass, respectively. We exploit this result to obtain DFs for the general relativistic extension of the hypervirial family introduced by Nguyen and Lingam [Mon. Not. R. Astron. Soc. 436, 2014 (2013), 10.1093/mnras/stt1719], which Newtonian potential is given by ϕ (r )=-ϕo/[1 +(r /a )n]1 /n (a and ϕo are positive free parameters, n =1 ,2 ,… ). Such DFs can be written in the form Fn=ln -2ξn(ɛ ) . For odd n , we find that ξn is a polynomial of order 2 n +1 in ɛ , as in the case of the Hernquist model (n =1 ), for which F1∝l-1(2 ɛ -1 ) (ɛ-1 ) 2 . For even n , we can write ξn in terms of incomplete beta functions (Plummer model, n =2 , is an example). Since we demand that F ≥0 throughout the phase space, the particular form of each ξn leads to restrictions for the values of ϕo. For example, for the Hernquist model we find that 0 ≤ϕo≤2 /3 , i.e., an upper bounding value less than the one obtained for Nguyen and Lingam (0 ≤ϕo≤1 ), based on energy conditions.

Quasi-biennial modulation of solar neutrino flux: connections with solar activity

Science.gov (United States)

Vecchio, A.; Laurenza, M.; D'alessi, L.; Carbone, V.; Storini, M.

2011-12-01

A quasi-biennial periodicity has been recently found (Vecchio et al., 2010) in the solar neutrino flux, as detected at the Homestake experiment, as well as in the flux of solar energetic protons, by means of the Empirical Modes Decomposition technique. Moreover, both fluxes have been found to be significantly correlated at the quasi-biennial timescale, thus supporting the hypothesis of a connection between solar neutrinos and solar activity. The origin of this connection is investigated, by modeling how the standard Mikheyev-Smirnov-Wolfenstein (MSW) effect (the process for which the well-known neutrino flavor oscillations are modified in passing through the material) could be influenced by matter fluctuations. As proposed by Burgess et al., 2004, by introducing a background magnetic field in the helioseismic model, density fluctuations can be excited in the radiative zone by the resonance between helioseismic g-modes and Alfvén waves. In particular, with reasonable values of the background magnetic field (10-100 kG), the distance between resonant layers could be of the same order of neutrino oscillation length. We study the effect over this distance of a background magnetic field which is variable with a ~2 yr period, in agreement with typical variations of solar activity. Our findings suggest that the quasi-biennial modulation of the neutrino flux is theoretically possible as a consequence of the magnetic field variations in the solar interior. A. Vecchio, M. Laurenza, V. Carbone, M. Storini, The Astrophysical Journal Letters, 709, L1-L5 (2010). C. Burgess, N. S. Dzhalilov, T. I. Rashba, V., B.Semikoz, J. W. F. Valle, Mon. Not. R. Astron. Soc., 348, 609-624 (2004).

Metrics in Keplerian orbits quotient spaces

Science.gov (United States)

Milanov, Danila V.

2018-03-01

Quotient spaces of Keplerian orbits are important instruments for the modelling of orbit samples of celestial bodies on a large time span. We suppose that variations of the orbital eccentricities, inclinations and semi-major axes remain sufficiently small, while arbitrary perturbations are allowed for the arguments of pericentres or longitudes of the nodes, or both. The distance between orbits or their images in quotient spaces serves as a numerical criterion for such problems of Celestial Mechanics as search for common origin of meteoroid streams, comets, and asteroids, asteroid families identification, and others. In this paper, we consider quotient sets of the non-rectilinear Keplerian orbits space H. Their elements are identified irrespective of the values of pericentre arguments or node longitudes. We prove that distance functions on the quotient sets, introduced in Kholshevnikov et al. (Mon Not R Astron Soc 462:2275-2283, 2016), satisfy metric space axioms and discuss theoretical and practical importance of this result. Isometric embeddings of the quotient spaces into R^n, and a space of compact subsets of H with Hausdorff metric are constructed. The Euclidean representations of the orbits spaces find its applications in a problem of orbit averaging and computational algorithms specific to Euclidean space. We also explore completions of H and its quotient spaces with respect to corresponding metrics and establish a relation between elements of the extended spaces and rectilinear trajectories. Distance between an orbit and subsets of elliptic and hyperbolic orbits is calculated. This quantity provides an upper bound for the metric value in a problem of close orbits identification. Finally the invariance of the equivalence relations in H under coordinates change is discussed.

Anisotropic extinction distortion of the galaxy correlation function

International Nuclear Information System (INIS)

Fang Wenjuan; Hui Lam; Menard, Brice; May, Morgan; Scranton, Ryan

2011-01-01

Similar to the magnification of the galaxies' fluxes by gravitational lensing, the extinction of the fluxes by comic dust, whose existence is recently detected by [B. Menard, R. Scranton, M. Fukugita, and G. Richards, Mon. Not. R. Astron. Soc. 405, 1025 (2010).], also modifies the distribution of a flux-selected galaxy sample. We study the anisotropic distortion by dust extinction to the 3D galaxy correlation function, including magnification bias and redshift distortion at the same time. We find the extinction distortion is most significant along the line of sight and at large separations, similar to that by magnification bias. The correction from dust extinction is negative except at sufficiently large transverse separations, which is almost always opposite to that from magnification bias (we consider a number count slope s>0.4). Hence, the distortions from these two effects tend to reduce each other. At low z (< or approx. 1), the distortion by extinction is stronger than that by magnification bias, but at high z, the reverse holds. We also study how dust extinction affects probes in real space of the baryon acoustic oscillations (BAO) and the linear redshift distortion parameter β. We find its effect on BAO is negligible. However, it introduces a positive scale-dependent correction to β that can be as large as a few percent. At the same time, we also find a negative scale-dependent correction from magnification bias, which is up to percent level at low z, but to ∼40% at high z. These corrections are non-negligible for precision cosmology, and should be considered when testing General Relativity through the scale-dependence of β.

El Sistema de Referencia Celeste convencional de la IAU

Science.gov (United States)

Arias, E. F.

La Unión Astronómica Internacional (IAU) recomendó la adopción de un nuevo sistema de referencia celeste baricéntrico cuyo plano fundamental y origen de ascensiones rectas estén próximos, respectivamente, al ecuador y equinoccio dinámicos J2000.0. El nuevo sistema de referencia estará materializado por las posiciones J2000.0 de radiofuentes extragalácticas determinadas con la técnica de interferometría de larga línea de base (VLBI). El Working Group on Reference Frames de la IAU (WGRF) decidió adoptar (Grasse, 1995) al sistema de referencia celeste extragaláctico del Servicio Internacional de la Rotación Terrestre (IERS) como futuro sistema de referencia celeste convencional bajo el nombre International Celestial Reference System (ICRS) y encomendó su mantenimiento futuro al IERS. El marco de referencia que materializará al ICRS contiene posiciones precisas J2000.0 de más de 600 radiofuentes extragalácticas. Las coordenadas fueron ajustadas en una única solución VLBI en la cual se incluyeron todas las observaciones realizadas hasta octubre de 1995 con la técnica de adquisición de datos VLBI Mark III. Para minimizar los errores sistemáticos que pueden afectar la calidad del marco de referencia se introdujeron mejoras sustanciales en la modelización y en la selección de datos. Un subconjunto de objetos del marco de referencia se utilizó para referir las posiciones estelares determinadas con el satélite astrométrico Hipparcos al ICRS.

LM1-64: a Newly Reported Lmc-Pn with WR Nucleus

Science.gov (United States)

Pena, M.; Olguin, L.; Ruiz, M. T.; Torres-Peimbert, S.

1993-05-01

The object LM1-64 was reported by Lindsay & Mullan (1963, Irish Astron. J., 5, 51) as a probable PN in the LMC. Optical and UV spectra taken by us confirm that suggestion. LM1-64 is a high excitation planetary nebulae which shows evidence of having a WC central star. Broad stellar emission at lambda 4650 is detected in the optical spectrum obtained with the CTIO 4m telescope, in 1989. A UV spectrum in the range from 1200 Angstroms to 2000 Angstroms was obtained with IUE in 1990. We have measured all the emission line fluxes available and determined values for the physical conditions and chemical abundances of the nebular ionized gas. The derived values are T(OIII) = 14000K, log He/H = 11.05, log C/H = 9.48, log O/H = 8.55 and log Ne/H = 7.94. LM1-64 shows a large C enhancement in the envelope as result of the central star activity, while He, O and Ne are comparable to the average values reported for the LMC-PNe (Monk, Barlow & Clegg, 1988, MNRAS, 234, 583). We have estimated the He II Zanstra temperature of the central star to be ~ 80,000 K. This temperature is much higher than the values reported for the known LMC-PNe with WR nucleus that Monk et al. have classified as W4 to W8. The only other high temperature WR nucleus in a LMC-PN is N66 which recently showed evidence of undergoing a WR episode (Torres-Peimbert, Ruiz, Peimbert & Pe\\ na, 1993, IAU Symp. 155, eds. A. Acker & R. Weinberger, in press).

The Problem of Longitude in the 18th Century: Jorge Juan, Antonio de Ulloa and the Expedition of the Paris Academy of Sciences to the Kingdom of Peru

Science.gov (United States)

Gutiérrez, Manuel Pérez

2015-05-01

Jorge Juan and Antonio de Ulloa, naval officers of the Spanish Navy in the Midshipmen's Royal Academy were appointed to take part in one of the most important scientific expeditions of the 18th century. The question of the shape of the Earth, of vital importance for navigation, was solved by the Paris Academy of Sciences by request of Louis XV of France in 1735. The aim was to determine the form of the ellipsoid that Newton had described in the 17th century for any spherical and homogeneous body in rotation about an axis. Two expeditions were prepared for the geodetic measures of meridian arc both in high latitudes (Lapland, Finland) and in the equatorial zone (the Kingdom of Peru); Pierre Louis Maupertuis took charge of the northern expedition whereas the second one was charged to La Condamine, along with Jorge Juan and Antonio de Ulloa. The results obtained by the Spaniards were gathered in a publication: Observaciones astronómicas y físicas hechas en los Reinos del Perú. In it, they dedicate a chapter to the determination of astronomic longitude with the only technology that was providing certain precision at the moment: the simultaneous observation of the same astronomic phenomenon in two different places. Specifically, they explain in detail in Book III: Las Observaciones de la Inmersiones y Emersiones de los satélites de Júpiter, como asimismo de los eclipses de Luna; de las cuales de deduce la Longitud de los Lugares, incluyendo las correcciones a efectuar por la variación de la declinación diaria del Sol.

Luminous Infrared Galaxies. III. Multiple Merger, Extended Massive Star Formation, Galactic Wind, and Nuclear Inflow in NGC 3256

Science.gov (United States)

Lípari, S.; Díaz, R.; Taniguchi, Y.; Terlevich, R.; Dottori, H.; Carranza, G.

2000-08-01

We report detailed evidence for multiple merger, extended massive star formation, galactic wind, and circular/noncircular motions in the luminous infrared galaxy NGC 3256, based on observations of high-resolution imaging (Hubble Space Telescope, ESO NTT), and extensive spectroscopic data (more than 1000 spectra, collected at Estación Astrofísica de Bosque Alegre, Complejo Astronómico el Leoncito, Cerro Tololo InterAmerican Observatory, and IUE observatories). We find in a detailed morphological study (resolution ~15 pc) that the extended massive star formation process detected previously in NGC 3256 shows extended triple asymmetrical spiral arms (r~5 kpc), emanating from three different nuclei. The main optical nucleus shows a small spiral disk (r~500 pc), which is a continuation of the external one and reaches the very nucleus. The core shows blue elongated structure (50 pc×25 pc) and harbors a blue stellar cluster candidate (r~8 pc). We discuss this complex morphology in the framework of an extended massive star formation driven by a multiple merger process (models of Hernquist et al. and Taniguchi et al.). We study the kinematics of this system and present a detailed Hα velocity field for the central region (40''×40'' rmax~30''~5 kpc), with a spatial resolution of 1" and errors of +/-15 km s-1. The color and isovelocity maps show mainly (1) a kinematic center of circular motion with ``spider'' shape, located between the main optical nucleus and the close (5") mid-IR nucleus and (2) noncircular motions in the external parts. We obtained three ``sinusoidal rotation curves'' (from the Hα velocity field) around position angle (P.A.) ~55°, ~90°, and ~130°. In the main optical nucleus we found a clear ``outflow component'' associated with galactic winds plus an ``inflow radial motion.'' The outflow component was also detected in the central and external regions (rstandard models of photoionization, shocks, and starbursts). We present four detailed emission

Unveiling the formation and evolution of comets

Science.gov (United States)

Lasue, J.; Levasseur-Regourd, A. C.; Botet, R.; Coradini, A.; Desanctis, M. C.; Kofman, W.

2007-08-01

energy of the cometesimals and their probable re-accretion after collision events in the Kuiper Belt can be used to interpret the typical layered structure observed for comet 9P/Tempel 1 [10] and evaluate the tensile strengths inside the nucleus. Thermal evolution models of comet nuclei explain the current comet observations with the presence of primordial volatiles [11]. A quasi-3D approach (for non-spherically shaped comet nuclei) is used to interpret the current activity of comets in terms of initial characteristics, and to predict shape and internal stratification evolution of the nucleus. Tensile strength indications and activity predictions from such simulations will provide vital clues for the international Rosetta mission landing on the nucleus of comet 67P/Churyumov-Gerasimenko. During the Rosetta rendezvous, the CONSERT experiment will investigate the deep interior of the nucleus from measurements of the propagation delay of long wavelength radio waves [12]. The analysis and 3D reconstruction of the waves passing through the nucleus will put constraints on the materials constituting the comet and the inhomogeneities within the nucleus. While it is now established that nuclei have low densities and are significantly fragile, it will then be possible to better constrain their formation process and their evolution. [1] A'Hearn et al., Science 310, 258 (2005) [2] Samarasinha, Icarus 154, 540 (2001) [3] Trigo-Rodriguez and Llorca, Mon. Not. R. Astron. Soc. 372, 655 (2006) [4] A'Hearn and Combi, Icarus 187, 1 (2007) [5] Hanner and Bradley, In: Comets II, Festou, Keller, Weaver (eds), pp 555 (2004) [6] Brownlee et al., Science 314, 1711 (2006) [7] Lasue and Levasseur-Regourd, J. Quant. Spectros. Radiat. Transfer 100, 220-236 (2006) [8]Levasseur-Regourd et al., (2007), Planet Space Sci., doi:10.1016/j.pss.2006.11.014 in press. [9] Hörz et al., Science 314, 1716 (2006) [10] Belton et al., Icarus 187, 332 (2007) [11] DeSanctis et al., Astron. Astrophys. 444, 605 (2005

Disciplines and Professors of Astronomy in Undergraduate Physics Teachers Formation Courses in Brazilian Universities. (Spanish Title: Disciplinas y Profesores de Astronomia en los Cursos de Licenciatura en Física en Las Universidades Brasileñas.) Disciplinas e Professores de Astronomia Nos Cursos de Licenciatura em Física das Universidades Brasileiras

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Roberto, Artur Justiniano, Jr.; Reis, Thiago Henrique; dos Reis Germinaro, Daniel

2014-12-01

This article is the result of a research on basic training in Astronomy in physics degrees that performed the ENADE 2011 national examination. The objective was to identify whether there are disciplines of Astronomy in these courses, whether are mandatory or optional, its workload and when it is offered. The relationship between astronomers, physics degrees and disciplines of Astronomy was investigated. To perform this research we examined the results of ENADE 2011 and also the census of Brazilian Astronomical Society. As a result it is observed that in only 15% of the courses there is a mandatory subject of Astronomy, and therefore there is a high probability that 85% of physics teachers trained in 2011 have not had any discipline of Astronomy during their graduation. In addition, the data collected in this study shows a low number of members of SAB (Sociedade Astronômica Brasileira) among the surveyed courses. We have verified that the presence of astronomers in a given university does not imply to have a mandatory discipline of Astronomy in physics degrees at the same university. Este artículo es el resultado de una investigación sobre la formación básica en Astronomía en los cursos de Profesorado en Física que hicieron el examen nacional ENADE 2011. El objetivo del trabajo fue identificar se existen disciplinas de Astronomía en estos cursos, si son obligatorias u optativas, cuál es su carga horaria y el semestre en que son ofrecidas. Se investigó también la correlación entre astrónomos, los cursos de licenciatura en Física y las disciplinas de Astronomía. Para realizar esta investigación se utilizaron los datos del ENADE 2011 y también del censo de la Astronomía brasileña. Como resultado, se observó que en solo 15% de los cursos existe una disciplina obligatoria de Astronomía y que existe una grande probabilidad de que 85% de los profesores de Física formados en el año de 2011 no hayan cursado ninguna disciplina de Astronomía durante su

Waldmeier's Rules in the Solar and Stellar Dynamos

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Pipin, Valery; Kosovichev, Alexander

2015-08-01

The Waldmeier's rules [1] establish important empirical relations between the general parameters of magnetic cycles (such as the amplitude, period, growth rate and time profile) on the Sun and solar-type stars [2]. Variations of the magnetic cycle parameters depend on properties of the global dynamo processes operating in the stellar convection zones. We employ nonlinear mean-field axisymmetric dynamo models [3] and calculate of the magnetic cycle parameters, such as the dynamo cycle period, total magnetic and Poynting fluxes for the Sun and solar-type stars with rotational periods from 15 to 30 days. We consider two types of the dynamo models: 1) distributed (D-type) models employing the standard α - effect distributed in the whole convection zone, and 2) Babcock-Leighton (BL-type) models with a non-local α - effect. The dynamo models take into account the principal mechanisms of the nonlinear dynamo generation and saturation, including the magnetic helicity conservation, magnetic buoyancy effects, and the feedback on the angular momentum balance inside the convection zones. Both types of models show that the dynamo generated magnetic flux increases with the increase of the rotation rate. This corresponds to stronger brightness variations. The distributed dynamo model reproduces the observed dependence of the cycle period on the rotation rate for the Sun analogs better than the BL-type model. For the solar-type stars rotating more rapidly than the Sun we find dynamo regimes with multiple periods. Such stars with multiple cycles form a separate branch in the variability-rotation diagram.1. Waldmeier, M., Prognose für das nächste Sonnenfleckenmaximum, 1936, Astron. Nachrichten, 259,262. Soon,W.H., Baliunas,S.L., Zhang,Q.,An interpretation of cycle periods of stellar chromospheric activity, 1993, ApJ, 414,333. Pipin,V.V., Dependence of magnetic cycle parameters on period of rotation in nonlinear solar-type dynamos, 2015, astro-ph: 14125284

Saturn’s ring temperatures at equinox

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Spilker, Linda J.; Ferrari, C.; Morishima, R.

2013-10-01

Modeling the thermal emission of Saturn's rings is challenging due to the numerous heating sources as well as the structural properties of the disk and of the particles that are closely related. At equinox, however, the main rings are externally heated by Saturn alone and the problem is somewhat simplified. We test the abilities of our current models to reproduce the temperatures observed with the Cassini CIRS instrument around equinox in August 2009. A simple semi-analytic model which includes mutual shadowing effects can mostly explain the radial profile of the equinox ring temperatures, except the model predicts lower temperatures than those observed for the A ring. The temperature variation at a given saturnocentric radius is primarily caused by observational geometry variations relative to Saturn. The observed temperature increases with decreasing Saturn-ring-observer angle. In addition, we found evidence that the leading hemispheres of particles are warmer than the trailing hemispheres at least for the C ring and probably for the A and B rings as well. This is explained if some fraction of particles has spin rates lower than the synchronous rotation rate as predicted by N-body simulations. The spin model for a monolayer ring (Ferrari, C., Leyrat, C., 2006, Astron. Astrophys. 447, 745-760) can fit the temperature variations with spacecraft longitude observed in the C ring with currently known thermal properties and a mixing of slow and fast rotators. The multilayer model (Morishima, R., Salo, H., Ohtsuki, K., 2009, Icarus 201, 634-654) can reproduce the temperatures of the B and C rings but gives A ring temperatures that are significantly lower than those observed as does the simple semi-analytic model. More advanced models which take into account self-gravity wakes may explain the A ring temperature behavior.

VISIR upgrade overview and status

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Kerber, Florian; Käufl, Hans Ulrich; Baksai, Pedro; Dobrzycka, Danuta; Finger, Gert; Ives, Derek; Jakob, Gerd; Lagadec, Eric; Lundin, Lars; Mawet, Dimitri; Mehrgan, Leander; Moerchen, Margaret; Momany, Yazan; Moreau, Vincent; Pantin, Eric; Riquelme, Miguel; Siebenmorgen, Ralf; Silber, Armin; Smette, Alain; Taylor, Julian; van den Ancker, Mario; Venema, Lars; Weilenmann, Ueli; Yegorova, Irina

2012-09-01

We present an overview of the VISIR upgrade project. VISIR is the mid-infrared imager and spectrograph at ESO's VLT. The project team is comprised of ESO staff and members of the original VISIR consortium: CEA Saclay and ASTRON. The project plan is based on input from the ESO user community with the goal of enhancing the scientific performance and efficiency of VISIR by a combination of measures: installation of improved hardware, optimization of instrument operations and software support. The cornerstone of the upgrade is the 1k by 1k Si:As Aquarius detector array (Raytheon) which has demonstrated very good performance (sensitivity, stability) in the laboratory IR detector test facility (modified TIMMI 2 instrument). A prism spectroscopic mode will cover the N-band in a single observation. New scientific capabilities for high resolution and high-contrast imaging will be offered by sub-aperture mask (SAM) and phase-mask coronagraphic (4QPM/AGPM) modes. In order to make optimal use of favourable atmospheric conditions a water vapour monitor has been deployed on Paranal, allowing for real-time decisions and the introduction of a userdefined constraint on water vapour. Improved pipelines based on the ESO Reflex concept will provide better support to astronomers. The upgraded VISIR will be a powerful instrument providing background limited performance for diffraction-limited observations at an 8-m telescope. It will offer synergy with facilities such as ALMA, JWST, VLTI and SOFIA, while a wealth of targets is available from survey work (e.g. VISTA, WISE). In addition it will bring confirmation of the technical readiness and scientific value of several aspects of potential mid-IR instrumentation at Extremely Large Telescopes. The intervention on VISIR and installation of hardware has been completed in July and commissioning will take place during July and August. VISIR is scheduled to be available to the users starting Oct 2012.

Do cosmological data rule out f (R ) with w ≠-1 ?

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Battye, Richard A.; Bolliet, Boris; Pace, Francesco

2018-05-01

We review the equation of state (EoS) approach to dark sector perturbations and apply it to f (R ) gravity models of dark energy. We show that the EoS approach is numerically stable and use it to set observational constraints on designer models. Within the EoS approach we build an analytical understanding of the dynamics of cosmological perturbations for the designer class of f (R ) gravity models, characterized by the parameter B0 and the background equation of state of dark energy w . When we use the Planck cosmic microwave background temperature anisotropy, polarization, and lensing data as well as the baryonic acoustic oscillation data from SDSS and WiggleZ, we find B0<0.006 (95% C.L.) for the designer models with w =-1 . Furthermore, we find B0<0.0045 and |w +1 |<0.002 (95% C.L.) for the designer models with w ≠-1 . Previous analyses found similar results for designer and Hu-Sawicki f (R ) gravity models using the effective field theory approach [Raveri et al., Phys. Rev. D 90, 043513 (2014), 10.1103/PhysRevD.90.043513; Hu et al., Mon. Not. R. Astron. Soc. 459, 3880 (2016), 10.1093/mnras/stw775]; therefore this hints for the fact that generic f (R ) models with w ≠-1 can be tightly constrained by current cosmological data, complementary to solar system tests [Brax et al., Phys. Rev. D 78, 104021 (2008), 10.1103/PhysRevD.78.104021; Faulkner et al., Phys. Rev. D 76, 063505 (2007), 10.1103/PhysRevD.76.063505]. When compared to a w CDM fluid with the same sound speed, we find that the equation of state for f (R ) models is better constrained to be close to -1 by about an order of magnitude, due to the strong dependence of the perturbations on w .

El núcleo de instituciones científicas matritenses en el Paseo del Prado desde el siglo XVIII

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Baratas Díaz, Luis Alfredo

1996-06-01

Full Text Available Throughout second half of 18th century was constituted a scientific institutions centre around the “Paseo del Prado” (Royal Botanical Garden, Sciences Academy, Astronomic Observatory, General Hospital,.... The development of this scientific area suffered the vicissitudes and limitations that affected to the illustrated scientific policy. In 19th century the new educational and research centers establishment was scarce and laking of clear guidelines; the various projects to build a Sciences Faculty or the Arts and Trades School limited considerably the extension of the Royal Garden. In the first third of 20th century the constructing activity would be limited to the works in the Cajal Institute (plagued by misundestanding and upsetting and some constant remodeling works in the Velasco Museum and Royal Garden.

A lo largo de la segunda mitad del siglo XVIII se constituyó en torno al actual Paseo del Prado un importante núcleo de instituciones científicas (Real Jardín Botánico, Academia de Ciencias, Observatorio Astronómico, Hospital General,.... El desarrollo de este foco científico sufrió las vicisitudes y limitaciones que afectaron a la política científica ilustrada. En el siglo XIX el establecimiento de nuevos centros docentes en esta zona fue escaso y carente de una idea directriz; los diversos proyectos para edificar una Facultad de Ciencias o la Escuela de Artes y Oficios limitaron considerablemente la extensión del Real Jardín. En el primer tercio del siglo XX la actividad constructora se limitaría a las obras en el Instituto Cajal (plagadas de malentendidos y desajustes y unas constantes obras de remodelación en el Museo Velasco y el Jardín Botánico.

Expo 70 - Osaka, Japón

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Editorial, Equipo

1970-06-01

Full Text Available The following pavillions at the Expo-70 in Osaka are outstanding. The West German Exhibit, with a structure reminiscent of an astronomical observatory. The U.R.R.S. Pavillion, which is 109 m high, and has a tubular support. The Motor Car Industry Display, which involves two units and a tent like roof. The Festival Palace, within the representative zone of the Exhibition, and houses the official ceremonies in honour of the participating nations. The Tashida IHI Pavillion, whose structure includes the use of 1,338 interconnected tetrapods. The Takara Group Display, which is an abstract concept, consisting of a large number of cube space forms. The firm Takenaka Komuten Co. Ltd. has taken a very active part in the construction of 28 buildings, both Japanese and foreign.Destacan en la EXPO-70 los siguientes pabellones: el pabellón de la Alemania Occidental, con su estructura en forma de cúpula para observaciones astronómicas; el de la U.R.S.S., de 109 m de altura y estructura tubular; el de la Industria Automovilística, que consta de dos unidades y presenta una cubierta en forma de tienda de campaña; el palacio de Festivales, que forma parte de la zona representativa de la exposición; en él se desarrollan los actos dedicados a las naciones participantes; el pabellón Toshiba IHI, en cuya estructura se emplearon un total de 1.338 tetrápodos ensamblados; el pabellón del grupo Takara, diseñado con una concepción abstracta —a base de cubos—. La empresa «Takenaka Komuten, Co. Ltd.», ha intervenido eficazmente en la construcción de 28 pabellones, japoneses y extranjeros.

Origin of the Pluto-Charon system: Constraints from the New Horizons flyby

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McKinnon, William B.; Stern, S. A.; Weaver, H. A.; Nimmo, F.; Bierson, C. J.; Grundy, W. M.; Cook, J. C.; Cruikshank, D. P.; Parker, A. H.; Moore, J. M.; Spencer, J. R.; Young, L. A.; Olkin, C. B.; Ennico Smith, K.; New Horizons Geology, Geophysics; Imaging; Composition Theme Teams

2017-05-01

New Horizon's accurate determination of the sizes and densities of Pluto and Charon now permit precise internal models of both bodies to be constructed. Assuming differentiated rock-ice structures, we find that Pluto is close to 2/3 solar-composition anhydrous rock by mass and Charon 3/5 solar-composition anhydrous rock by mass. Pluto and Charon are closer to each other in density than to other large (≳1000-km diameter) Kuiper belt bodies. Despite this, we show that neither the possible presence of an ocean under Pluto's water ice shell (and no ocean within Charon), nor enhanced porosity at depth in Charon's icy crust compared with that of Pluto, are sufficient to make Pluto and Charon's rock mass fractions match. All four small satellites (Styx, Nix, Kerberos, Hydra) appear much icier in comparison with either Pluto or Charon. In terms of a giant impact origin, both these inferences are most consistent with the relatively slow collision of partly differentiated precursor bodies (Canup, Astrophys. J. 141, 35, 2011). This is in turn consistent with dynamical conditions in the ancestral Kuiper belt, but implies that the impact precursors themselves accreted relatively late and slowly (to limit 26Al and accretional heating). The iciness of the small satellites is not consistent with direct formation of the Pluto-Charon system from a streaming instability in the solar nebula followed by prompt collapse of gravitationally bound ;pebble piles,; a proposed formation mechanism for Kuiper belt binaries (Nesvorný et al., Astron. J. 140, 785-793, 2010). Growth of Pluto-scale bodies by accretion of pebbles in the ancestral Kuiper belt is not ruled out, however, and may be needed to prevent the precursor bodies from fully differentiating, due to buried accretional heat, prior to the Charon-forming impact.

Prediction and Confirmation of V-type Asteroids Beyond 2.5 AU Based on SDSS Colors

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Binzel, Richard P.; Masi, G.; Foglia, S.

2006-09-01

We apply a taxonomic classification system developed by Masi et al. (2006, submitted to Icarus) to identify C-, S-, and V-type asteroids present within the 3rd Release of the Sloan Digital Sky Survey Moving Object Catalog (SDSS MOC3). The classifications deduced by Masi et al. for 43,000 asteroids using SDSS colors are based on the taxonomy of Bus (1999; MIT Ph.D. thesis). To link SDSS colors to the Bus taxonomy, Masi et al. (2006) use 149 objects measured in common by both SDSS and the Small Main-Belt Asteroid Spectroscopic Survey (SMASS) (Bus and Binzel 2002, Icarus 158, 106). We report results of direct testing of SDSS V-type classification predictions for six objects, where the tests were performed by visible wavelength spectroscopy (Lazzaro et al. 2004, Icarus 172, 179) and target of opportunity near-infrared spectroscopy obtained using the NASA Infrared Telescope Facility (IRTF). Vesta-like spectra and a V-type taxonomy are confirmed for five of the six predicted V-type objects sampled. Most interestingly, the SDSS taxonomy correctly predicted the V-type spectral characteristics for asteroid (21238) 1995 WV7, a 6 km asteroid located far from Vesta across the 3:1 mean motion resonance at 2.54 AU. (Proper elements a,e,i: 2.54 AU, 0.14, and 10.8 deg.) Given the 2 km/sec ejection velocity required from Vesta to reach the current orbit, and the difficulty of migrating across the 3:1 resonance (at 2.5 AU) by a process such as Yarkovsky drift or via secular resonances (Carruba et al. 2005, Astron. Astrophys. 441, 819), asteroid 21238 may be a new candidate for a basaltic asteroid having no relationship to Vesta.

Cosmic Rays in Thunderstorms

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Buitink, Stijn; Scholten, Olaf; van den Berg, Ad; Ebert, Ute

2013-04-01

Cosmic Rays in Thunderstorms Cosmic rays are protons and heavier nuclei that constantly bombard the Earth's atmosphere with energies spanning a vast range from 109 to 1021 eV. At typical altitudes up to 10-20 km they initiate large particle cascades, called extensive air showers, that contain millions to billions of secondary particles depending on their initial energy. These particles include electrons, positrons, hadrons and muons, and are concentrated in a compact particle front that propagates at relativistic speed. In addition, the shower leaves behind a trail of lower energy electrons from ionization of air molecules. Under thunderstorm conditions these electrons contribute to the electrical and ionization processes in the cloud. When the local electric field is strong enough the secondary electrons can create relativistic electron run-away avalanches [1] or even non-relativistic avalanches. Cosmic rays could even trigger lightning inception. Conversely, strong electric fields also influence the development of the air shower [2]. Extensive air showers emit a short (tens of nanoseconds) radio pulse due to deflection of the shower particles in the Earth's magnetic field [3]. Antenna arrays, such as AERA, LOFAR and LOPES detect these pulses in a frequency window of roughly 10-100 MHz. These systems are also sensitive to the radiation from discharges associated to thunderstorms, and provide a means to study the interaction of cosmic ray air showers and the electrical processes in thunderstorms [4]. In this presentation we discuss the involved radiation mechanisms and present analyses of thunderstorm data from air shower arrays [1] A. Gurevich et al., Phys. Lett. A 165, 463 (1992) [2] S. Buitink et al., Astropart. Phys. 33, 1 (2010) [3] H. Falcke et al., Nature 435, 313 (2005) [4] S. Buitink et al., Astron. & Astrophys. 467, 385 (2007)

New relativistic effective interaction for finite nuclei, infinite nuclear matter, and neutron stars

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Kumar, Bharat; Patra, S. K.; Agrawal, B. K.

2018-04-01

We carry out the study of finite nuclei, infinite nuclear matter, and neutron star properties with the newly developed relativistic force, the Institute of Physics Bhubaneswar-I (IOPB-I). Using this force, we calculate the binding energies, charge radii, and neutron-skin thickness for some selected nuclei. From the ground-state properties of superheavy nuclei (Z =120 ), it is noticed that considerable shell gaps appear at neutron numbers N =172 , 184, and 198, manifesting the magicity at these numbers. The low-density behavior of the equation of state for pure neutron matter is compatible with other microscopic models. Along with the nuclear symmetry energy, its slope and curvature parameters at the saturation density are consistent with those extracted from various experimental data. We calculate the neutron star properties with the equation of state composed of nucleons and leptons in β -equilibrium, which are in good agreement with the x-ray observations by Steiner [Astrophys. J. 722, 33 (2010), 10.1088/0004-637X/722/1/33] and Nättilä [Astron. Astrophys. 591, A25 (2016), 10.1051/0004-6361/201527416]. Based on the recent observation of GW170817 with a quasi-universal relation, Rezzolla et al. [Astrophys. J. Lett. 852, L25 (2018), 10.3847/2041-8213/aaa401] have set a limit for the maximum mass that can be supported against gravity by a nonrotating neutron star in the range 2.01 ±0.04 ≲M (M⊙)≲2.16 ±0.03 . We find that the maximum mass of the neutron star for the IOPB-I parametrization is 2.15 M⊙ . The radius and tidal deformability of a canonical neutron star of mass 1.4 M⊙ are 13.2 km and 3.9 ×1036g cm2s2 , respectively.

Origin Of The Near-earth Asteroid Phaethon And The Geminids Meteor Shower

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de Leon, Julia; Campins, H.; Tsiganis, K.; Morbidelli, A.; Licandro, J.

2010-10-01

Asteroid (3200) Phaethon is a remarkable Near Earth Asteroid (NEA). It was the first asteroid associated with a meteor shower, namely the Geminid stream1. Phaethon's unusual orbit has a high inclination and a very low perihelion distance (0.14 AU). Its reflectance spectrum suggests a connection with primitive meteorites, best fitting with CI/CM carbonaceous chondrites2, aqueously altered and rich in hydrated silicates. However, its origin is not well determined. Recent studies suggest a connection with the population of main-belt comets3, classifying Phaethon as an activated asteroid. Here we show that the most likely source of Phaethon and the Geminids is the asteroid (2) Pallas, one of the largest asteroids in the main belt, which is surrounded by a collisional family, containing several Phaethon-sized objects. Pallas’ highly inclined orbit and surface composition, also primitive and with evidence of hydration4, support this connection. Our analysis reveals a striking similarity between Phaethon's visual spectrum and those of Pallas family members. Moreover, our numerical simulations show the existence of a robust dynamical pathway, connecting the orbital neighborhood of Pallas with that of Phaethon. In this respect, the Pallas family may constitute a source of primitive NEAs. (The author gratefully acknowledges support from the Spanish "Ministerio de Ciencia e Innovación" projects AYA2005-07808-C03-02 and AYA2008-06202-C03-02.) References 1. Whipple, F. L. 1983, IAU Circular, 3881 2. Licandro, J., Campins, H., Mothe-Diniz, T., Pinilla-Alonso, N. & de Leon, J. 2007, Astron. Astrophys. 461, 751-757 3. Hsieh, H. H., & Jewitt, D. 2006, Science, 312, 561-563 4. Rivkin, A. S., Howell, E. S., Vilas, F. & Lebofsky, L. A. in Asteroids III (eds Bottke, W. F., Cellino, A., Paolicchi, P. & Binzel, R. P.) 235-253 (Univ. Arizona Press, 2002).

Métodos de projeção para observação segura de eclipses solares

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Norma Teresinha Oliveira Reis

2012-04-01

Full Text Available http://dx.doi.org/10.5007/2175-7941.2012v29n1p81 Apresentamos um estudo sobre eclipses e uma atividade educacional para o nível básico sobre métodos de observação segura do Sol. Este artigo traz, ainda, informações históricas e conceitos científicos acerca de eclipses solares e lunares, bem como conceitos sobre clima espacial. Os eclipses solares são fenômenos astronômicos de rara beleza que chamam a atenção de pessoas de todas as idades. Por isso, é importante conscientizar a respeito dos riscos associados com a exposição direta dos olhos à radiação solar e apresentar métodos para sua observação segura. A observação incauta do Sol pode provocar danos visuais severos, inclusive deficiência visual total. Considerando que a incidência de tais danos aumenta durante a ocorrência de eclipses solares, diferentes métodos de observação foram investigados em termos de riscos, vantagens e desvantagens. Concluiu-se que os métodos de projeção são os mais adequados para a observação segura do Sol. Três aparatos de projeção de baixo custo e fácil montagem são apresentados. Eles permitem a observação segura de eclipses solares, contribuindo, dessa forma, para despertar o interesse de estudantes de nível básico para ciências espaciais e para a educação científico-tecnológica de uma forma geral.

Cycles of time in the Iberian culture: the astronomical orientation of the temple of El Tossal de Sant Miquel de Llíria

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Esteban, César

2006-06-01

Full Text Available We present an archaeoastronomical study of the temple of the Iberian settlement of El Tossal de Sant Miquel de Llíria (València. We find that the major axis of the building is oriented very close to the east-west cardinal axis. The entrance of the temple is pointing towards an outstanding mountain on the eastern horizon, where the sunrise around the equinoxes takes place. On the other hand, the absence of other constructions just in front of the cultic building seems to support the inference that the astronomical relation was intentional, because it would permit the observation of the sunrise from the temple. The existence of other nearby Iberian sanctuaries showing similar relations with the equinoxes (or a date very close to them strongly supports the importance of these solar dates in the Iberian ritual.

Presentamos un estudio arqueoastronómico del templo del poblado ibérico del Tossal de Sant Miquel de Llíria (Valencia. Encontramos que el eje mayor del edificio se encuentra orientado casi paralelo al eje cardinal este-oeste, con su entrada apuntando hacia una montaña singular del horizonte oriental donde se produce el orto solar alrededor de los equinoccios. Por otra parte, la ausencia de construcciones justo enfrente de la entrada del templo parece apoyar la intencionalidad de dicha relación astronómica, pues permitiría preservar la observación del fenómeno desde el edificio. La existencia de otros yacimientos ibéricos cercanos donde se han encontrado relaciones similares con los equinoccios (o una fecha muy cercana a éstos apunta, cada vez más claramente, hacia la idea de un especial protagonismo del paso del sol por los equinoccios en el calendario ritual ibérico.

Contribution of astrology in medicine -- a review.

Science.gov (United States)

Sharma, Bhuvnesh Kumar; Prasad, P V V; Narayana, A

2007-01-01

Astrology is the art of predicting or determining the influence of the planets and stars on human affairs. The origin of this word is from Greek word astron, star + logos (discourse). Both Ayurveda and Astrology have established a way of life in India since time immemorial. Highly advanced knowledge related to Astrology on medicine is preserved in Indian Holy scriptures and transmitted from generation to generation. Although both Astrology and medicine were developed as a part of religion in ancient India, astrological principles related to prevention, health care and relief from illness were applied as rituals (religious ceremonies). An astrologer gives guidance for taking medicines at suitable time for the best remedy of ailments. Even the medicinal herbs were collected and used at appropriate times for their efficacy. Astrology and Ayurveda are inseparable in human life. Role of the Astrology in healthy life and pathogenesis of the disease is well known to Indians. When a physician knows etiology of the disease, he attempts to treat the disease with specific medication, diet and life style and also avoiding causative factors. In a case where a physician is unable to understand the pathogenesis of the disease and to treat, the patient depends upon Astrology. Account of good and bad deeds during this life and previous lives, their consequences of health or ill health during this life which orderly, when, what and how will be clearly known through Astrology. It gives guidelines about welfare not only to human being but also to whole creation and also indicates about calamities and their solutions as possible extent. Hence a concise astrological evaluation related to prevention, health care, diagnosis and treatment of diseases is being presented in this article.

Health promotion, preventive and curative aspects of diseases in astrology.

Science.gov (United States)

Sharma, Bhuvnesh Kumar; Subhakta, P K J P; Narayana, A

2007-01-01

The whole universe is intermingling into a unit in the period of globalization. Different cultures, life-styles and sciences are co-operating with each other in this situation. World Health Organization is working towards collaborating all prevalent medical sciences for attainment of good health and family welfare for each and every individual by 2020. Astrology is a part of Indian heritage. Astrology means the art of predicting or determining the influence of the planets and stars on human affairs. The origin of this word is from Greek word astron, star + logos (discourse). The account of deeds of good and bad during the present life and previous lives, their consequences of health or ill health during this life i.e. what, when and how the things takes place will be clearly known through Astrology. Highly advanced knowledge related to Astrology on medicine is preserved in Indian scriptures and the knowledge was transmitted from generation to generation. It is also a good source for health promotion, preventive, curative and other medical aspects. Brief direction related to astrological medical aspects is also available in Ayurvedic literature (Carakasamhită, Suśrutasamhhită, Aşţăngasangraha, Aşţăngahŗdaya, Sărngadharasamhită , Băvaprakăśa etc.) Some Ayurvedic practitioners, scholars and scientists realize the need of astrological knowledge related to medicine in the present time. In ancient times physician, astrologer and purŏhita (Hindu priest) simultaneously looked after the health and family welfare of individual, families and country. Astrologer guides medication and suitable time for the better cure of ailments. Even the medicinal herbs were collected and treated at appropriate time for their efficacy. Astrology and Ayurvĕda are inseparable sciences of life. Hence, in this article, a concise astrological evaluation related to health promotion, preventive and curative aspects of Astrology is being presented.

Nebulosas planetárias galácticas: idades e cinemática

Science.gov (United States)

Lago, L. G.; Maciel, W. J.

2003-08-01

As nebulosas planetárias são formadas a partir de estrelas com massas entre 0.8 e 8 massas solares na sequência principal, formando um conjunto de objetos com idades e populações diferentes. Esse fato torna as nebulosas interessantes ao estudo da rotação galáctica, uma vez que as populações mais jovens devem estar claramente associadas ao disco fino da Galáxia, enquanto que as populações mais velhas estariam associadas ao disco espesso ou mesmo ao halo galáctico. Neste trabalho, utilizamos uma grande amostra de nebulosas com velocidades radiais conhecidas para determinar a curva de rotação da Galáxia. Para minimizar os erros decorrentes das incertezas nas distâncias, usamos quatro diferentes escalas estatísticas. Para a atribuição da idade dos objetos, utilizamos o método proposto recentemente por Maciel et al. (Astron. Astrophys. 397, 667, 2003), em um estudo da variação temporal dos gradientes de abundâncias. Com esse método, é possível obter uma classificação das nebulosas por grupos de idade, totalmente independente de outros sistemas de classificação, uma vez que as idades são estimadas individualmente, a partir das metalicidades das nebulosas. Nossos resultados são comparados com as previsões dos tipos de Peimbert, e mostram que os desvios médios das curvas obtidas são sensivelmente menores nos casos dos objetos mais jovens, associados ao disco fino, com relação aos objetos mais velhos do disco espesso, levando à determinação de uma curva de rotação semelhante à dos objetos de população I jovem. (CNPq)

Looking a gift horse in the mouth: Evaluation of wide-field asteroid photometric surveys

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Harris, Alan W.; Pravec, Petr; Warner, Brian D.

2012-09-01

It has recently become possible to do a photometric survey of many asteroids at once, rather than observing single asteroids one (or occasionally a couple) at a time. We evaluate two such surveys. Dermawan et al. (Dermawan et al. [2011]. Publ. Astron. Soc. Jpn. 63, S555-S576) observed one night on the Subaru 8.2 m telescope, and Masiero et al. (Masiero, J., Jedicke, R., Durech, J., Gwen, S., Denneau, L., Larsen, J. [2009]. Icarus 204, 145-171) observed six nights over 2 weeks with the 3.6 m CFHT. Dermawan claimed 83 rotation periods from 127 detected asteroids; Masiero et al. claimed 218 rotation periods from 828 detections. Both teams claim a number of super-fast rotators (P < 2.2 h) among main belt asteroids larger than 250 m diameter, some up to several km in diameter. This would imply that the spin rate distribution of main belt asteroids differs from like-sized NEAs, that there are larger super-fast rotators (monolithic asteroids) in the main belt than among NEAs. Here we evaluate these survey results, applying the same criteria for reliability of results that we apply to all results listed in our Lightcurve Database (Warner, B.D., Harris, A.W., Pravec, P. [2009a]. Icarus 202, 134-146). In doing so, we assigned reliability estimates judged sufficient for inclusion in statistical studies for only 27 out of 83 (33%) periods claimed by Dermawan, and only 87 out of 218 (40%) periods reported by Masiero et al.; none of the super-fast rotators larger than about 250 m diameter claimed by either survey received a reliability rating judged sufficient for analysis. We find no reliable basis for the claim of different rotation properties between main belt and near-Earth asteroids. Our analysis presents a cautionary message for future surveys.

OPTICAL SPECTROSCOPIC OBSERVATIONS OF GAMMA-RAY BLAZAR CANDIDATES. V. TNG, KPNO, AND OAN OBSERVATIONS OF BLAZAR CANDIDATES OF UNCERTAIN TYPE IN THE NORTHERN HEMISPHERE

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Álvarez Crespo, N.; Massaro, F. [Dipartimento di Fisica, Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino (Italy); Masetti, N. [INAF—Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, I-40129, Bologna (Italy); Ricci, F.; La Franca, F. [Dipartimento di Matematica e Fisica, Università Roma Tre, via della Vasca Navale 84, I-00146, Roma (Italy); Landoni, M. [INAF-Osservatorio Astronomico di Brera, Via Emilio Bianchi 46, I-23807 Merate (Italy); Patiño-Álvarez, V.; Chavushyan, V.; Torrealba, J. [Instituto Nacional de Astrofisica, Óptica y Electrónica, Apartado Postal 51-216, 72000 Puebla, México (Mexico); D’Abrusco, R.; Paggi, A.; Smith, Howard A. [Harvard—Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Jiménez-Bailón, E. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 877, Ensenada, 22800 Baja California, México (Mexico); Latronico, L. [Istituto Nazionale di Fisica Nucleare, Sezione di Torino, I-10125 Torino (Italy); Tosti, G. [Dipartimento di Fisica, Università degli Studi di Perugia, I-06123 Perugia (Italy)

2016-02-15

The extragalactic γ-ray sky is dominated by emission from blazars, a peculiar class of active galactic nuclei. Many of the γ-ray sources included in the Fermi-Large Area Telescope Third Source catalog (3FGL) are classified as blazar candidates of uncertain type (BCUs) because there are no optical spectra available in the literature to confirm their nature. In 2013, we started a spectroscopic campaign to look for the optical counterparts of the BCUs and of the unidentified γ-ray sources to confirm their blazar nature. Whenever possible we also determine their redshifts. Here, we present the results of the observations carried out in the northern hemisphere in 2013 and 2014 at the Telescopio Nazionale Galileo, Kitt Peak National Observatory, and Observatorio Astronómico Nacional in San Pedro Mártir. In this paper, we describe the optical spectra of 25 sources. We confirmed that all of the 15 BCUs observed in our campaign and included in our sample are blazars and we estimated the redshifts for three of them. In addition, we present the spectra for three sources classified as BL Lacs in the literature but with no optical spectra available to date. We found that one of them is a quasar (QSO) at a redshift of z = 0.208 and the other two are BL Lacs. Moreover, we also present seven new spectra for known blazars listed in the Roma-BZCAT that have an uncertain redshift or are classified as BL Lac candidates. We found that one of them, 5BZB J0724+2621, is a “changing look” blazar. According to the spectrum available in the literature, it was classified as a BL Lac, but in our observation we clearly detected a broad emission line that led us to classify this source as a QSO at z = 1.17.

Migration of Frosts from High-Albedo Regions of Pluto: what New Horizons Reveals

Science.gov (United States)

Buratti, Bonnie J.; Stern, S. A.; Weaver, Hal A.; Young, Leslie A.; Olkin, Cathy B.; Ennico, Kimberly; Binzel, Richard P.; Zangari, Amanda; Earle, Alissa M.

2015-11-01

With its high eccentricity and obliquity, Pluto should exhibit seasonal volatile transport on its surface. Several lines of evidence support this transport: doubling of Pluto’s atmospheric pressure over the past two decades (Young et al., 2013, Ap. J. 766, L22; Olkin et al., 2015, Icarus 246, 230); changes in its historical rotational light curve, once all variations due to viewing geometry have been modelled (Buratti et al., 2015; Ap. J. 804, L6); and changes in HST albedo maps (Buie et al., 2010, Astron. J. 139, 1128). New Horizons LORRI images reveal that the region of greatest albedo change is not the polar cap(s) of Pluto, but the feature informally named Tombaugh Regio (TR). This feature has a normal reflectance as high as ~0.8 in some places, and it is superposed on older, lower-albedo pre-existing terrain with an albedo of only ~0.10. This contrast is larger than any other body in the Solar System, except for Iapetus. This albedo dichotomy leads to a complicated system of cold-trapping and thermal segregation, beyond the simple picture of seasonal volatile transport. Whatever the origin of TR, it initially acted as a cold trap, as the temperature differential between the high and low albedo regions could be enormous, possibly approaching 20K, based on their albedo differences and assuming their normalized phase curves are similar. This latter assumption will be refined as the full New Horizons data set is returned.Over six decades of ground-based photometry suggest that TR has been decreasing in albedo over the last 25 years. Possible causes include changing insolation angles, or sublimation from the edges where the high-albedo material impinges on a much warmer substrate.Funding by the NASA New Horizons Project acknowledged.

Teaching of Astronomy: Scenarios of Teaching Practice in Elementary Schools. (Spanish Title: Enseñanza de la Astronomía: Semblanzas de la Práctica Docente en Educación Primaria.) Ensino de Astronomia: Cenários da Prática Docente no Ensino Fundamental

Science.gov (United States)

Marchi Gonzatti, Sônia Elisa; Spessatto De Maman, Andréia; Fernandes Borragini, Eliana; Kerber, Júlia Cristina; Haetinger, Werner

2013-12-01

atomización de los asuntos, aunque temas como movimientos de la Tierra y fenómenos astronómicos hayan sido citados por la mayoría de los participantes. En cuanto a las estrategias, se verifico que se emplean principalmente clases con el apoyo de recursos bidimensionales, como películas, textos, mapas y búsqueda en internet. Las principales dificultades fueron la falta de formación específica con respecto a los contenidos de Astronomía, y el nivel de abstracción exigido por los contenidos. De modo general, esos indicadores convergen para los resultados ya encontrados en otros estudios, en el que las deficiencias de la formación inicial de los profesores, o incluso su ausencia, dificulta el adecuado abordaje de la Astronomía en las clases. Neste trabalho são apresentados os principais resultados de uma investigação realizada no campo da Educação em Astronomia, com professores do ensino fundamental de duas regiões do Rio Grande do Sul. O objetivo do estudo foi caracterizar o cenário regional do ensino de Astronomia, estabelecendo um comparativo com o cenário nacional. Esse estudo abordou três questões: identificar os principais temas de astronomia trabalhados em sala de aula, as estratégias metodológicas e quais as dificuldades apresentadas pelos professores ao desenvolver sua prática. Quanto aos conteúdos, encontrouse uma pulverização dos assuntos abordados, embora temas como movimentos da Terra e fenômenos astronômicos tenham sido citados pela maioria dos participantes. Sobre estratégias, são utilizadas principalmente aulas com apoio de recursos bidimensionais, como filmes, textos, mapas e pesquisa na internet. As principais dificuldades foram: falta de formação específica em relação a conteúdos de Astronomia; nível de abstração dos conteúdos, que dificultam sua compreensão, tanto pelos alunos quanto pelos próprios professores. De maneira geral, esses indicadores convergem para resultados já encontrados em outros estudos que

More chips off of Asteroid (4) Vesta: Characterization of eight Vestoids and their HED meteorite analogs

Science.gov (United States)

Hardersen, Paul S.; Reddy, Vishnu; Roberts, Rachel; Mainzer, Amy

2014-11-01

Vestoids are generally considered to be fragments from Asteroid (4) Vesta that were ejected by past collisions that document Vesta's collisional history. Dynamical Vestoids are defined by their spatial proximity with Vesta (Zappala, V., Bendjoya, Ph., Cellino, A., Farinella, P., Froeschle', C. [1995]. Icarus 116, 291-314; Nesvorny, D. [2012]. Nesvorny HCM Asteroid Families V2.0. EAR-A-VARGBDET-5-NESVORNYFAM-V2.0. NASA Planetary Data System.). Taxonomic Vestoids are defined as V-type asteroids that have a photometric, visible-wavelength spectral, or other observational relationship with Vesta (Tholen, D.J., 1984. Asteroid Taxonomy from Cluster Analysis of Photometry. Ph.D. Thesis, University of Arizona, Tucson; Bus, S.J., Binzel, R.P. [2002]. Icarus 158, 106-145; Carvano, J., Hasselmann, P.H., Lazzaro, D., Mothe'-Diniz, T. [2010]. Astron. Astrophys. 510, A43). We define 'genetic Vestoids' as V-type asteroids that are probable fragments ejected from (4) Vesta based on the supporting combination of dynamical, near-infrared (NIR) spectral, and taxonomic evidence. NIR reflectance spectroscopy is one of the primary ground-based techniques to constrain an asteroid's major surface mineralogy (Burns, R.G. [1993a]. Mineralogical Applications of Crystal Field Theory. Cambridge University Press, Cambridge, UK, 551 p). Despite the reasonable likelihood that many dynamical and taxonomic Vestoids likely originate from Vesta, ambiguity exists concerning the fraction of these populations that are from Vesta as compared to the fraction of asteroids that might not be related to Vesta. Currently, one of the most robust techniques to identify the genetic Vestoid population is through NIR reflectance spectroscopy from ∼0.7 to 2.5 μm. The derivation of spectral band parameters, and the comparison of those band parameters with those from representative samples from the Howardite-Eucrite-Diogenite (HED) meteorite types, allows a direct comparison of their primary mineralogies

Difficulties of First Years Elementary School Teachers with the Teaching of Astronomy. (Breton Title: Dificuldades de Professores dos Anos Iniciais do Ensino Fundamental em Relação ao Ensino da Astronomia. ) Dificultades de LOS Profesores de los Primeros Años de la Escuela Primaria en Relación a la Enseñanza de la Astronomía

Science.gov (United States)

Langhi, Rodolfo; Nardi, Roberto

2005-12-01

This paper reports Primary School teachers' discourses analysis about their difficulties related to the teaching of Astronomy. It reports partial data of a master's level research carried out in the last two years, named "An exploratory study for inserting Astronomy in primary school teachers' education" (LANGHI, 2004). The study took into consideration students' and teachers' common sense conceptions about astronomical phenomena, conceptual mistakes in textbooks, and Astronomy's suggestions given by the PCN (Parâmetros Curriculares Nacionais - The Brazilian National Curriculum Standards). The paper aims to characterize teachers' difficulties, in order to provide subsides to the implementation of an initial or continuing education program. This study is justified by the fact that courses plans like these only will be adapted to the teacher's (and students') reality, if there is a primary investigation about what the teachers really need to know about Astronomy. This fact was possible here by the enunciations interpretation of a teachers' sample using semi-structured interviews, according to discourse analysis procedures. The research outcomes show difficulties related to factors like: those of personal order, methodological, on teacher's formation, educational infrastructure and other related to information sources for educators. Este artigo, que relata as dificuldades de professores em relação ao ensino da Astronomia, faz parte de um estudo exploratório para a inserção da Astronomia na formação de professores dos anos iniciais do Ensino Fundamental. Esse estudo leva em consideração as concepções alternativas de alunos e professores sobre fenômenos astronômicos, os erros conceituais em livros didáticos e as sugestões de conteúdos de Astronomia constantes nos PCN (Parâmetros Curriculares Nacionais). Caracterizar as dificuldades dos professores é a questão central deste texto, apontando para o objetivo de contribuir com subsídios para um futuro

CALIFA, the Calar Alto Legacy Integral Field Area survey. IV. Third public data release

Science.gov (United States)

Sánchez, S. F.; García-Benito, R.; Zibetti, S.; Walcher, C. J.; Husemann, B.; Mendoza, M. A.; Galbany, L.; Falcón-Barroso, J.; Mast, D.; Aceituno, J.; Aguerri, J. A. L.; Alves, J.; Amorim, A. L.; Ascasibar, Y.; Barrado-Navascues, D.; Barrera-Ballesteros, J.; Bekeraitè, S.; Bland-Hawthorn, J.; Cano Díaz, M.; Cid Fernandes, R.; Cavichia, O.; Cortijo, C.; Dannerbauer, H.; Demleitner, M.; Díaz, A.; Dettmar, R. J.; de Lorenzo-Cáceres, A.; del Olmo, A.; Galazzi, A.; García-Lorenzo, B.; Gil de Paz, A.; González Delgado, R.; Holmes, L.; Iglésias-Páramo, J.; Kehrig, C.; Kelz, A.; Kennicutt, R. C.; Kleemann, B.; Lacerda, E. A. D.; López Fernández, R.; López Sánchez, A. R.; Lyubenova, M.; Marino, R.; Márquez, I.; Mendez-Abreu, J.; Mollá, M.; Monreal-Ibero, A.; Ortega Minakata, R.; Torres-Papaqui, J. P.; Pérez, E.; Rosales-Ortega, F. F.; Roth, M. M.; Sánchez-Blázquez, P.; Schilling, U.; Spekkens, K.; Vale Asari, N.; van den Bosch, R. C. E.; van de Ven, G.; Vilchez, J. M.; Wild, V.; Wisotzki, L.; Yıldırım, A.; Ziegler, B.

2016-10-01

This paper describes the third public data release (DR3) of the Calar Alto Legacy Integral Field Area (CALIFA) survey. Science-grade quality data for 667 galaxies are made public, including the 200 galaxies of the second public data release (DR2). Data were obtained with the integral-field spectrograph PMAS/PPak mounted on the 3.5 m telescope at the Calar Alto Observatory. Three different spectral setups are available: I) a low-resolution V500 setup covering the wavelength range 3745-7500 Å (4240-7140 Å unvignetted) with a spectral resolution of 6.0 Å (FWHM) for 646 galaxies, II) a medium-resolution V1200 setup covering the wavelength range 3650-4840 Å (3650-4620 Å unvignetted) with a spectral resolution of 2.3 Å (FWHM) for 484 galaxies, and III) the combination of the cubes from both setups (called COMBO) with a spectral resolution of 6.0 Å and a wavelength range between 3700-7500 Å (3700-7140 Å unvignetted) for 446 galaxies. The Main Sample, selected and observed according to the CALIFA survey strategy covers a redshift range between 0.005 and 0.03, spans the color-magnitude diagram and probes a wide range of stellar masses, ionization conditions, and morphological types. The Extension Sample covers several types of galaxies that are rare in the overall galaxy population and are therefore not numerous or absent in the CALIFA Main Sample. All the cubes in the data release were processed using the latest pipeline, which includes improved versions of the calibration frames and an even further improved image reconstruction quality. In total, the third data release contains 1576 datacubes, including ~1.5 million independent spectra. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck-Institut für Astronomie (MPIA) and the Instituto de Astrofísica de Andalucía (CSIC).The spectra are available at http://califa.caha.es/DR3

Optimisation of centroiding algorithms for photon event counting imaging

International Nuclear Information System (INIS)

Suhling, K.; Airey, R.W.; Morgan, B.L.

1999-01-01

Approaches to photon event counting imaging in which the output events of an image intensifier are located using a centroiding technique have long been plagued by fixed pattern noise in which a grid of dimensions similar to those of the CCD pixels is superimposed on the image. This is caused by a mismatch between the photon event shape and the centroiding algorithm. We have used hyperbolic cosine, Gaussian, Lorentzian, parabolic as well as 3-, 5-, and 7-point centre of gravity algorithms, and hybrids thereof, to assess means of minimising this fixed pattern noise. We show that fixed pattern noise generated by the widely used centre of gravity centroiding is due to intrinsic features of the algorithm. Our results confirm that the recently proposed use of Gaussian centroiding does indeed show a significant reduction of fixed pattern noise compared to centre of gravity centroiding (Michel et al., Mon. Not. R. Astron. Soc. 292 (1997) 611-620). However, the disadvantage of a Gaussian algorithm is a centroiding failure for small pulses, caused by a division by zero, which leads to a loss of detective quantum efficiency (DQE) and to small amounts of residual fixed pattern noise. Using both real data from an image intensifier system employing a progressive scan camera, framegrabber and PC, and also synthetic data from Monte-Carlo simulations, we find that hybrid centroiding algorithms can reduce the fixed pattern noise without loss of resolution or loss of DQE. Imaging a test pattern to assess the features of the different algorithms shows that a hybrid of Gaussian and 3-point centre of gravity centroiding algorithms results in an optimum combination of low fixed pattern noise (lower than a simple Gaussian), high DQE, and high resolution. The Lorentzian algorithm gives the worst results in terms of high fixed pattern noise and low resolution, and the Gaussian and hyperbolic cosine algorithms have the lowest DQEs

La creación del mundo supralunar según Abraham Ibn Ezra: un estudio comparativo de sus dos comentarios a Génesis 1,14

Directory of Open Access Journals (Sweden)

Sela, Shlomo

2003-06-01

Full Text Available This article aims at elucidating Abraham Ibn Ezra's (ca. 1089 - ca. 1167 opinion about the creation of the supra-lunar world. A major and striking feature of Ibn Ezra's approach is that he did not find it convenient to address this issue, intimately related to the nature of the celestial bodies, in his astronomical or astrological treatises, but rather in his biblical commentaries. Therefore, we propose to concentrate our efforts on the meticulous study of the two commentaries which Ibn Ezra wrote on Genesis 1,14. As this verse focuses on the account of the creation of the heavenly bodies, we have assumed that the elusive Ibn Ezra could not have avoided revealing his view, or, at least, that we should have left some significant hints from which we may uncover his genuine opinion about the creation of the supra-lunar world.

El propósito de este artículo es averiguar la opinión de Abraham Ibn Ezra (ca. 1089 - ca. 1167 sobre lo relacionado con la creación del mundo supralunar. Una característica fundamental dei modus operandi de Ibn Ezra es que, si buscamos información acerca de su opinión sobre la creación del mundo, tanto sublunar como supralunar, no la hallaremos en sus tratados científicos astronómicos o astrológicos, sino precisamente en sus comentarios bíblicos. Por lo tanto, la metodología más adecuada consistirá en concentrar nuestros esfuerzos en el estudio meticuloso de sus dos comentarios a Génesis 1,14. Dado que este verso bíblico tiene como objetivo principal el relato y la descripción de la creación de las luminarias, pensamos que en ambos comentarios Ibn Ezra no pudo haber eludido dar su verdadera opinión -o al menos dejar alguna pista significativa- sobre la creación del mundo supralunar.

Use of supernovae light curves for testing the expansion hypothesis and other cosmological relations

International Nuclear Information System (INIS)

Rust, B.W.

1974-01-01

This thesis is primarily concerned with a test of the expansion hypothesis based on the relation Δt/sub obs/ = (1 + V/sub r//c)Δt/sub int/ where Δt/sub int/ is the time lapse characterizing some phenomenon in a distant galaxy, Δt/sub obs/ is the observed time lapse and V/sub r/ is the symbolic velocity of recession. If the red shift is a Doppler effect, the observed time lapse should be lengthened by the same factor as the wave length of the light. Many authors have suggested type I supernovae for such a test because of their great luminosity and the uniformity of their light curves, but apparently the test has heretofore never actually been performed. Thirty-six light curves were gathered from the literature and one (SN1971i) was measured. All of the light curves were reduced to a common (m/sub pg/) photometric system. The comparison time lapse, Δt/sub c/, was taken to be the time required for the brightness to fall from 0.5 m below peak to 2.5 m below peak. The straight line regression of Δt/sub c/ on V/sub r/ gives a correlation coefficient significant at the 93 percent level, and the simple static Euclidean hypothesis is rejected at that level. The regression line also deviates from the prediction of the classical expansion hypothesis. Better agreement was obtained using the chronogeometric theory of I. E. Segal ( []972 Astron. and Astrophys. 18, 143), but the scatter in the present data makes it impossible to distinguish between these alternate hypotheses at the 95 percent confidence level. The question of how many additional light curves would be needed to give definite tests is addressed. It is shown that at the present rate of supernova discoveries, only a few more years would be required to obtain the necessary data if light curves are systematically measured for the more distant supernovae. (Diss. Abstr. Int., B)

Black holes in binary stellar systems and galactic nuclei

International Nuclear Information System (INIS)

Cherepashchuk, A M

2014-01-01

In the last 40 years, following pioneering papers by Ya B Zeldovich and E E Salpeter, in which a powerful energy release from nonspherical accretion of matter onto a black hole (BH) was predicted, many observational studies of black holes in the Universe have been carried out. To date, the masses of several dozen stellar-mass black holes (M BH =(4−20)M ⊙ ) in X-ray binary systems and of several hundred supermassive black holes (M BH =(10 6 −10 10 )M ⊙ ) in galactic nuclei have been measured. The estimated radii of these massive and compact objects do not exceed several gravitational radii. For about ten stellar-mass black holes and several dozen supermassive black holes, the values of the dimensionless angular momentum a ∗ have been estimated, which, in agreement with theoretical predictions, do not exceed the limiting value a ∗ =0.998. A new field of astrophysics, so-called black hole demography, which studies the birth and growth of black holes and their evolutionary connection to other objects in the Universe, namely stars, galaxies, etc., is rapidly developing. In addition to supermassive black holes, massive stellar clusters are observed in galactic nuclei, and their evolution is distinct from that of supermassive black holes. The evolutionary relations between supermassive black holes in galactic centers and spheroidal stellar components (bulges) of galaxies, as well as dark-matter galactic haloes are brought out. The launch into Earth's orbit of the space radio interferometer RadioAstron opened up the real possibility of finally proving that numerous discovered massive and highly compact objects with properties very similar to those of black holes make up real black holes in the sense of Albert Einstein's General Relativity. Similar proofs of the existence of black holes in the Universe can be obtained by intercontinental radio interferometry at short wavelengths λ≲1 mm (the international program, Event Horizon Telescope). (100

Developing the Planetary Science Virtual Observatory

Science.gov (United States)

Erard, Stéphane; Cecconi, Baptiste; Le Sidaner, Pierre; Henry, Florence; Chauvin, Cyril; Berthier, Jérôme; André, Nicolas; Génot, Vincent; Schmitt, Bernard; Capria, Teresa; Chanteur, Gérard

2015-08-01

In the frame of the Europlanet-RI program, a prototype Virtual Observatory dedicated to Planetary Science has been set up. Most of the activity was dedicated to the definition of standards to handle data in this field. The aim was to facilitate searches in big archives as well as sparse databases, to make on-line data access and visualization possible, and to allow small data providers to make their data available in an interoperable environment with minimum effort. This system makes intensive use of studies and developments led in Astronomy (IVOA), Solar Science (HELIO), and space archive services (IPDA).The current architecture connects existing data services with IVOA or IPDA protocols whenever relevant. However, a more general standard has been devised to handle the specific complexity of Planetary Science, e.g. in terms of measurement types and coordinate frames. This protocol, named EPN-TAP, is based on TAP and includes precise requirements to describe the contents of a data service (Erard et al Astron & Comp 2014). A light framework (DaCHS/GAVO) and a procedure have been identified to install small data services, and several hands-on sessions have been organized already. The data services are declared in standard IVOA registries. Support to new data services in Europe will be provided during the proposed Europlanet H2020 program, with a focus on planetary mission support (Rosetta, Cassini…).A specific client (VESPA) has been developed at VO-Paris (http://vespa.obspm.fr). It is able to use all the mandatory parameters in EPN-TAP, plus extra parameters from individual services. A resolver for target names is also available. Selected data can be sent to VO visualization tools such as TOPCAT or Aladin though the SAMP protocol.Future steps will include the development of a connection between the VO world and GIS tools, and integration of heliophysics, planetary plasma and reference spectroscopic data.The EuroPlaNet-RI project was funded by the European

Distributed order reaction-diffusion systems associated with Caputo derivatives

Science.gov (United States)

Saxena, R. K.; Mathai, A. M.; Haubold, H. J.

2014-08-01

This paper deals with the investigation of the solution of an unified fractional reaction-diffusion equation of distributed order associated with the Caputo derivatives as the time-derivative and Riesz-Feller fractional derivative as the space-derivative. The solution is derived by the application of the joint Laplace and Fourier transforms in compact and closed form in terms of the H-function. The results derived are of general nature and include the results investigated earlier by other authors, notably by Mainardi et al. ["The fundamental solution of the space-time fractional diffusion equation," Fractional Calculus Appl. Anal. 4, 153-202 (2001); Mainardi et al. "Fox H-functions in fractional diffusion," J. Comput. Appl. Math. 178, 321-331 (2005)] for the fundamental solution of the space-time fractional equation, including Haubold et al. ["Solutions of reaction-diffusion equations in terms of the H-function," Bull. Astron. Soc. India 35, 681-689 (2007)] and Saxena et al. ["Fractional reaction-diffusion equations," Astrophys. Space Sci. 305, 289-296 (2006a)] for fractional reaction-diffusion equations. The advantage of using the Riesz-Feller derivative lies in the fact that the solution of the fractional reaction-diffusion equation, containing this derivative, includes the fundamental solution for space-time fractional diffusion, which itself is a generalization of fractional diffusion, space-time fraction diffusion, and time-fractional diffusion, see Schneider and Wyss ["Fractional diffusion and wave equations," J. Math. Phys. 30, 134-144 (1989)]. These specialized types of diffusion can be interpreted as spatial probability density functions evolving in time and are expressible in terms of the H-function in compact forms. The convergence conditions for the double series occurring in the solutions are investigated. It is interesting to observe that the double series comes out to be a special case of the Srivastava-Daoust hypergeometric function of two variables

Resistance of Wheat Accessions to the English Grain Aphid Sitobion avenae

Science.gov (United States)

Hu, Xiang-Shun; Liu, Ying-Jie; Wang, Yu-Han; Wang, Zhe; Yu, Xin-lin; Wang, Bo; Zhang, Gai-Sheng; Liu, Xiao-Feng; Hu, Zu-Qing; Zhao, Hui-Yan; Liu, Tong-Xian

2016-01-01

The English grain aphid, Sitobion avenae, is a major pest species of wheat crops; however, certain varieties may have stronger resistance to infestation than others. Here, we investigated 3 classical resistance mechanisms (antixenosis, antibiosis, and tolerance) by 14 wheat varieties/lines to S. avenae under laboratory and field conditions. Under laboratory conditions, alatae given the choice between 2 wheat varieties, strongly discriminated against certain varieties. Specifically, the ‘Amigo’ variety had the lowest palatability to S. avenae alatae of all varieties. ‘Tm’ (Triticum monococcum), ‘Astron,’ ‘Xanthus,’ ‘Ww2730,’ and ‘Batis’ varieties also had lower palatability than other varieties. Thus, these accessions may use antibiosis as the resistant mechanism. In contrast, under field conditions, there were no significant differences in the number of alatae detected on the 14 wheat varieties. One synthetic line (98-10-30, a cross between of Triticum aestivum (var. Chris) and Triticum turgidum (var. durum) hybridization) had low aphid numbers but high yield loss, indicating that it has high antibiosis, but poor tolerance. In comparison, ‘Amigo,’ ‘Xiaoyan22,’ and some ‘186Tm’ samples had high aphid numbers but low yield loss rates, indicating they have low antibiosis, but good tolerance. Aphid population size and wheat yield loss rates greatly varied in different fields and years for ‘98-10-35,’ ‘Xiaoyan22,’ ‘Tp,’ ‘Tam200,’ ‘PI high,’ and other ‘186Tm’ samples, which were hybrid offspring of T. aestivum and wheat related species. Thus, these germplasm should be considered for use in future studies. Overall, S. avenae is best adapted to ‘Xinong1376,’ because it was the most palatable variety, with the greatest yield loss rates of all 14 wheat varieties. However, individual varieties/lines influenced aphid populations differently in different years. Therefore, we strongly recommend a combination of

Two-halo term in stacked thermal Sunyaev-Zel'dovich measurements: Implications for self-similarity

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Hill, J. Colin; Baxter, Eric J.; Lidz, Adam; Greco, Johnny P.; Jain, Bhuvnesh

2018-04-01

The relation between the mass and integrated electron pressure of galaxy group and cluster halos can be probed by stacking maps of the thermal Sunyaev-Zel'dovich (tSZ) effect. Perhaps surprisingly, recent observational results have indicated that the scaling relation between integrated pressure and mass follows the prediction of simple, self-similar models down to halo masses as low as 1 012.5 M⊙ . Hydrodynamical simulations that incorporate energetic feedback processes suggest that gas should be depleted from such low-mass halos, thus decreasing their tSZ signal relative to self-similar predictions. Here, we build on the modeling of V. Vikram, A. Lidz, and B. Jain, Mon. Not. R. Astron. Soc. 467, 2315 (2017), 10.1093/mnras/stw3311 to evaluate the bias in the interpretation of stacked tSZ measurements due to the signal from correlated halos (the "two-halo" term), which has generally been neglected in the literature. We fit theoretical models to a measurement of the tSZ-galaxy group cross-correlation function, accounting explicitly for the one- and two-halo contributions. We find moderate evidence of a deviation from self-similarity in the pressure-mass relation, even after marginalizing over conservative miscentering effects. We explore pressure-mass models with a break at 1 014 M⊙, as well as other variants. We discuss and test for sources of uncertainty in our analysis, in particular a possible bias in the halo mass estimates and the coarse resolution of the Planck beam. We compare our findings with earlier analyses by exploring the extent to which halo isolation criteria can reduce the two-halo contribution. Finally, we show that ongoing third-generation cosmic microwave background experiments will explicitly resolve the one-halo term in low-mass groups; our methodology can be applied to these upcoming data sets to obtain a clear answer to the question of self-similarity and an improved understanding of hot gas in low-mass halos.

Reconstructing the dark sector interaction with LISA

Energy Technology Data Exchange (ETDEWEB)

Cai, Rong-Gen; Yang, Tao [CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. Box 2735, Beijing 100190 (China); Tamanini, Nicola, E-mail: cairg@itp.ac.cn, E-mail: nicola.tamanini@cea.fr, E-mail: yangtao@itp.ac.cn [Institut de Physique Théorique, CEA-Saclay, CNRS UMR 3681, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France)

2017-05-01

We perform a forecast analysis of the ability of the LISA space-based interferometer to reconstruct the dark sector interaction using gravitational wave standard sirens at high redshift. We employ Gaussian process methods to reconstruct the distance-redshift relation in a model independent way. We adopt simulated catalogues of standard sirens given by merging massive black hole binaries visible by LISA, with an electromagnetic counterpart detectable by future telescopes. The catalogues are based on three different astrophysical scenarios for the evolution of massive black hole mergers based on the semi-analytic model of E. Barausse, Mon. Not. Roy. Astron. Soc. 423 (2012) 2533. We first use these standard siren datasets to assess the potential of LISA in reconstructing a possible interaction between vacuum dark energy and dark matter. Then we combine the LISA cosmological data with supernovae data simulated for the Dark Energy Survey. We consider two scenarios distinguished by the time duration of the LISA mission: 5 and 10 years. Using only LISA standard siren data, the dark sector interaction can be well reconstructed from redshift z ∼1 to z ∼3 (for a 5 years mission) and z ∼1 up to z ∼5 (for a 10 years mission), though the reconstruction is inefficient at lower redshift. When combined with the DES datasets, the interaction is well reconstructed in the whole redshift region from 0 z ∼ to z ∼3 (5 yr) and z ∼0 to z ∼5 (10 yr), respectively. Massive black hole binary standard sirens can thus be used to constrain the dark sector interaction at redshift ranges not reachable by usual supernovae datasets which probe only the z ∼< 1.5 range. Gravitational wave standard sirens will not only constitute a complementary and alternative way, with respect to familiar electromagnetic observations, to probe the cosmic expansion, but will also provide new tests to constrain possible deviations from the standard ΛCDM dynamics, especially at high redshift.

Projeto educação em ciências com observatórios virtuais: a participação da Escola Moppe no período 2000-2003

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Wuensche, C. A.; Gavioli, E.; Oliveira, A. L. P. R. S.; da Silva, C.; Cardoso, H. P.; Estácio, S.

2003-08-01

O projeto Educação em Ciências com Observatórios Virtuais foi concebido pelo Instituto Astronômico e Geofísico da USP, agregando diversas instituições de ensino e pesquisa no país para desenvolver competências diversas na educação fundamental, média e superior utilizando a astronomia como ferramenta multidisciplinar. Este trabalho descreve a participação da MOPPE, escola-piloto do INPE no projeto, no período de 2000-2003. Serão apresentadas 1) a criação de um clube de ciências (1999 a 2001) cujo tema foi a colonização de Marte e 2) a ementa de astronomia trabalhada com as 7a. e 8a. séries do ensino fundamental. A proposta do projeto Colonizando Marte foi estudar diversos aspectos de uma missão interplanetária e construir experiementos que permitissem quantificar esses aspectos. Os resultados obtidos incluiram apresentações nas SBPC Jovem em 2000 e 2001. Discutiremos também as ementas de astronomia trabalhadas desde 2001 e o envolvimento dos alunos com atividades ligadas a astronomia, fora da aula de ciências. A inclusão de astronomia no currículo das últimas séries motivou a participação de mais alunos culminando com a conquista de duas medalhas para alunos da 7a. série na Olimpiada Brasileira de Astronomia em 2002. Houve também um aumento no número de participantes na OBA 2003 e nos projetos de astronomia mais elaborados nas Feira de Ciências de 2001 e 2002. Destacamos em 2003 a inclusão da MOPPE no projeto TIE - Telescopes in Education - da NASA, que utiliza o telescópio do Observatório de Mount Wilson (EUA) para observações remotas em projetos pedagógicos para o ensino de astronomia.

Multi-spectral remote sensing of the vortex formerly known as White Oval BA: Temperature structure and cloud properties

Science.gov (United States)

Orton, G.; Parrish, P.; Yanamandra-Fisher, P.; Baines, K.; Mousis, O.; Pantin, E.; Fujiyoshi, T.; Fuse, T.; Simon-Miller, A.

White Oval BA: Temperature structure and cloud properties G. Orton, P. Parrish, P. Yanamandra-Fisher, K. Baines (1), O. Mousis (2), E. Pantin (3), T. Fuse, T. Fujiyoshi (4), A. Simon-Miller (5) (1) Jet Propulsion Laboratory, Calif. Inst. of Technology, USA, (2) Obs. de Besancon, France, (3) C.E.A., France, (4) Subaru National Astron. Obs., Japan, (5) NASA Goddard Space Flight Center, USA. (Glenn.Orton@jpl.nasa.gov) White Oval BA, constituted from 3 predecessor vortices (known as Jupiter's "classical" White Ovals) after successive mergers in 1998 and 2000, became second-largest vortex in the atmosphere of Jupiter (and possibly the solar system) at the time of its formation. While it continues in this distinction, it required a name change after a 2005 December through 2006 February transformation which made it appear visually the same color as the Great Red Spot. Our campaign to understand the changes involved examination of the detailed color and wind field using Hubble Space Telescope instrumentation on several orbits in April. The field of temperatures, ammonia distribution and clouds were also examined using the mid-infrared VISIR camera/spectrometer on ESO's 8.2-m Very Large Telescope (3), the NASA Infrared telescope with the mid-infrared MIRSI instrument and the refurbished near-infrared facility camera NSFCam2. High-resolution images of the Oval were made before the color change with the COMICS mid-infrared facility on the Subaru telescope. We are using these data, and possibly others to be acquired during the summer, to characterize the extent to which changes in storm strength (vorticity, positive vertical motion) influenced (i) the depth from which colored cloud particles may have been "dredged up" from depth or (ii) the altitude to which particles may have been lofted and subject to high-energy UV radiation which caused a color change, as alternative explanations for the phenomenon. Clues to this will provide clues to the chemistry of Jupiter's cloud

Espectroscopia de candidatos a remanescentes de aglomerados abertos

Science.gov (United States)

Pavani, D. B.; Bica, E.; Ahumada, A. V.; Clariá, J. J.

2003-08-01

A pesquisa sobre remanescentes de aglomerados abertos tem despertado grande interesse. Seguindo esta tendência encontramos estudos teóricos e observacionais. Os primeiros baseiam-se em simulações numéricas buscando determinar fração de binárias e distâncias galatocêntricas, tempo de vida e conteúdo estelar. Estes estão relacionados à função inicial de massa e densidade de estrelas, ou seja, se ricos ou pobremente povoados, compactos ou esparsos. No caso observacional procuram-se identificar os remanescentes considerando-se que trazem estas assinaturas de seus percursores. No presente estudo empregamos espectroscopia para analisar oito concentrações pobremente povoadas, previamente classificadas como aglomerados abertos, sendo sete compactas e uma esparsa. As observações foram obtidas através do telescópio de 2,15 m do CASLEO em San Juan, Argentina, em turnos entre 2001 e 2003. Utilizamos uma câmara CCD contendo um chip Tektronics de 1024X1024 pixeis aliado a um espectrógrafo REOSC. O domínio espectral vai de 3700 a 7000 Å. As reduções foram realizadas no Observatório Astronômico de Córdoba (Argentina) usando pacotes IRAF padrões. Determinamos idades, avermelhamentos e tipos espectrais através de comparações com biblioteca de estrelas e de aglomerados. Em alguns casos nossos espectros estavam dominados por estrelas individuais às quais determinamos seus tipos espectrais. Aos oito objetos adicionamos mais cinco da literatura recente analisados via espectro ou diagrama cor-magnitude. O histograma resultante contém idades típicas entre 0.5 e 3 Ganos. Considerando que predominantemente estes objetos encontram-se na vizinhança solar e, portanto, não cruzaram muitas vezes o plano Galático esperamos que a diferença no tempo necessário para dissolução destes prováveis remanescentes seja em função de diferentes massas iniciais.

Cassini/CIRS Observations of Water Vapor in Titan's Stratosphere

Science.gov (United States)

Bjoraker, Gordon L.; Achterberg, R. K.; Anderson, C. M.; Samuelson, R. E.; Carlson, R. C.; Jennings, D. E.

2008-01-01

The Composite Infrared Spectrometer (CIRS) on the Cassini spacecraft has obtained spectra of Titan during most of the 44 flybys of the Cassini prime mission. Water vapor on Titan was first detected using whole-disk observations from the Infrared Space Observatory (Coustenis et al 1998, Astron. Astrophys. 336, L85-L89). CIRS data permlt the retrieval of the latitudinal variation of water on Titan and some limited information on its vertical profile. Emission lines of H2O on Titan are very weak in the CIRS data. Thus, large spectral averages as well as improvements in calibration are necessary to detect water vapor. Water abundances were retrieved in nadir spectra at 55 South, the Equator, and at 19 North. Limb spectra of the Equator were also modeled to constrain the vertical distribution of water. Stratospheric temperatures in the 0.5 - 4.0 mbar range were obtained by inverting spectra of CH4 in the v4 band centered at 1304/cm. The temperature in the lower stratosphere (4 - 20 mbar) was derived from fitting pure rotation lines of CH4 between 80 and 160/cm. The origin of H2O and CO2 is believed to be from the ablation of micrometeorites containing water ice, followed by photochemistry. This external source of water originates either within the Saturn system or from the interplanetary medium. Recently, Horst et al (J. Geophys. Res. 2008, in press) developed a photochemical model of Titan in which there are two external sources of oxygen. Oxygen ions (probably from Enceladus) precipitate into Titan's atmosphere to form CO at very high altitudes (1100 km). Water ice ablation at lower altitudes (700 km) forms H2O and subsequent chemistry produces CO2. CIRS measurements of CO, CO2, and now of H2O will provide valuable constraints to these photochemical models and - improve our understanding of oxygen chemistry on Titan.

Evaluación de la escala Borg de esfuerzo percibido aplicada a la rehabilitación cardiaca Instrument evaluation of Borg's perceived exertion scale in cardiac rehabilitation

Directory of Open Access Journals (Sweden)

Natalie Burkhalter

1996-12-01

Full Text Available La escala Borg de esfuerzo percibido mide la gama entera del esfuerzo que el individuo percibe al hacer ejercicio. Esta escala da criterios para hacerle ajustes a la intensidad de ejercicio, o sea, a la carga de trabajo, y así pronosticar y dictaminar las diferentes intensidades del ejercicio en los deportes y en la rehabilitación médica (BORG, 1982. También se puede usar tanto en el atletismo, en la astronáutica, la industria y ambientes militares, como en las situaciones cotidianas. El concepto del esfuerzo percibido es una valoración subjetiva que indica la opinión del sujeto respecto a la intensidad del trabajo realizado (MORGAN, 1973. El sujeto que hace el ejercicio debe asignar un número del 1 al 20, para representar la sensación subjetiva de la cantidad de trabajo desempeñado. La escala es una herramienta valiosa dentro del ámbito del desempeño humano, en que a menudo la consideración importante no es tanto "lo que haga el individuo" "sino" "lo que cree que hace" (MORGAN, 1973.Borg's perceived exertion scale measures the extent of perceived exertion which a person experiences during exercise. The perceived exertion scale is used to adjust exercise intensity (workload for predictions and prescriptions of exercise intensities in sports and medical rehabilitation (BORG, 1982. In addition, Borg's scale can be used in the athletic arena, space, industry, military settings, or under everyday circumstances. The concept of perceived exertion is a subjective rating, indicating the subject's opinion about the intensity of the work being performed (MORGAN, 1973. The task of exercising subjects is to assign a number (from 1-20 to represent the subjective sensation of the amount of work being performed. This is a valuable tool in human performance setting, where an important consideration is not "what the individual is doing, but what he thinks and is doing" (MORGAN, 1973.

Impact of seeing and host galaxy into the analysis of photo-polarimetric microvariability in blazars. Case study of the nearby blazars 1ES 1959+650 and HB89 2201+044

Science.gov (United States)

Sosa, M. S.; von Essen, C.; Andruchow, I.; Cellone, S. A.

2017-11-01

Blazars, a type of Active Galactic Nuclei, present a particular orientation of their jets close to the line of sight. Their radiation is thus relativistically beamed, giving rise to extreme behaviors, specially strong variability on very short timescales (I.e., microvariability). Here we present simultaneous photometric and polarimetric observations of two relatively nearby blazars, 1ES 1959+650 and HB89 2201+044, that were obtained using the Calar Alto Faint Object Spectrograph mounted at the 2.2 m telescope in Calar Alto, Spain. An outstanding characteristic of these two blazars is the presence of well resolved host galaxies. This particular feature allows us to produce a study of their intrinsic polarization, a measurement of the polarization state of the galactic nucleus unaffected by the host galaxy. To carry out this work, we computed photometric fluxes from which we calculated the degree and orientation of the blazars polarization. Then, we analyzed the depolarizing effect introduced by the host galaxy with the main goal to recover the intrinsic polarization of the galactic nucleus, carefully taking into consideration the spurious polarimetric variability introduced by changes in seeing along the observing nights. We find that the two blazars do not present intra-night photo-polarimetric variability, although we do detect a significant inter-night variability. Comparing polarimetric values before and after accounting for the host galaxies, we observe a significant difference in the polarization degree of about 1% in the case of 1ES 1959+650, and 0.3% in the case of HB89 2201+044, thus evidencing the non-negligible impact introduced by the host galaxies. We note that this host galaxy effect depends on the waveband, and varies with changing seeing conditions, so it should be particularly considered when studying frequency-dependent polarization in blazars. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated

Modeling of the Enceladus water vapor jets for interpreting UVIS star and solar occultation observations

Science.gov (United States)

Portyankina, Ganna; Esposito, Larry W.; Aye, Klaus-Michael; Hansen, Candice J.

2015-11-01

); Porco, C.C. et al. Astron. J. 148, 45 (2014); Spitale, J.N. et al. Nature 521, 57-60 (2015)

Investigation of the Hydantoin Monomer and its Interaction with Water Molecules

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Gruet, Sébastien; Perez, Cristobal; Schnell, Melanie

2017-06-01

K., and Ohishi M., Astron. Astrophys., Forthcoming article (

Descripción del coronógrafo a ser instalado en Argentina (MICA)

Science.gov (United States)

Stenborg, G.; Francile, C.; Schwenn, R.; Epple, A.; Rovira, M.

El ``Coronógrafo de espejo para Argentina'' es un telescopio solar terrestre a ser colocado en el Observatorio Astronómico Félix Aguilar (El Leoncito), antes de finalizar 1996, como parte de un programa de ciencia bilateral entre Alemania y Argentina. Eclipses fotográficos de alta resolución han revelado que la corona solar es altamente estructurada y variable. De hecho, está contínuamente deformada y moldeada por los movimientos convectivos de los extremos de los arcos magnéticos en la fotosfera, estando, en muchas oportunidades, afectada por explosivas liberaciones de energía. MICA, en conjunción con otros telescopios solares espaciales y terrestres, tratará de contribuir al entendimiento de cuestiones fundamentales de la física solar. Entre ellas: cómo la corona está siendo calentada, dónde y cómo el viento solar es acelerado, qué causa los transitorios coronales, etc. Para ello investigará la distribución de los parámetros del plasma y su evolución con el tiempo, la estructura espacial de la corona en fina y gran escala, procesos que ocurren en los transitorios coronales y factores que los disparan, etc. Para responder a estas cuestiones MICA observará la atmósfera solar por sobre el limbo entre 1.1 y 2 radios solares aproximadamente, usando un nuevo tipo de sistema coronográfico que permite suprimir el brillo del disco solar suficientemente bien, tomando las imágenes con una cámara CCD de 1024x1024 pixels, codificada en 12 bits, pudiendo el mismo ser operado en forma remota. En la presente exposición describiremos las características del instrumento, cómo será controlado y qué esperamos observar basados en las imágenes obtenidas por los telescopios de similares características LASCO C1 a bordo del SOHO y PICO (ubicado en el Observatorio de Pic du Midi, Francia).

Black holes in binary stellar systems and galactic nuclei

Science.gov (United States)

Cherepashchuk, A. M.

2014-04-01

In the last 40 years, following pioneering papers by Ya B Zeldovich and E E Salpeter, in which a powerful energy release from nonspherical accretion of matter onto a black hole (BH) was predicted, many observational studies of black holes in the Universe have been carried out. To date, the masses of several dozen stellar-mass black holes (M_BH = (4{-}20) M_\\odot) in X-ray binary systems and of several hundred supermassive black holes (M_BH = (10^{6}{-}10^{10}) M_\\odot) in galactic nuclei have been measured. The estimated radii of these massive and compact objects do not exceed several gravitational radii. For about ten stellar-mass black holes and several dozen supermassive black holes, the values of the dimensionless angular momentum a_* have been estimated, which, in agreement with theoretical predictions, do not exceed the limiting value a_* = 0.998. A new field of astrophysics, so-called black hole demography, which studies the birth and growth of black holes and their evolutionary connection to other objects in the Universe, namely stars, galaxies, etc., is rapidly developing. In addition to supermassive black holes, massive stellar clusters are observed in galactic nuclei, and their evolution is distinct from that of supermassive black holes. The evolutionary relations between supermassive black holes in galactic centers and spheroidal stellar components (bulges) of galaxies, as well as dark-matter galactic haloes are brought out. The launch into Earth's orbit of the space radio interferometer RadioAstron opened up the real possibility of finally proving that numerous discovered massive and highly compact objects with properties very similar to those of black holes make up real black holes in the sense of Albert Einstein's General Relativity. Similar proofs of the existence of black holes in the Universe can be obtained by intercontinental radio interferometry at short wavelengths \\lambda \\lesssim 1 mm (the international program, Event Horizon Telescope).

Precessing rotating flows with additional shear: stability analysis.

Science.gov (United States)

Salhi, A; Cambon, C

2009-03-01

We consider unbounded precessing rotating flows in which vertical or horizontal shear is induced by the interaction between the solid-body rotation (with angular velocity Omega(0)) and the additional "precessing" Coriolis force (with angular velocity -epsilonOmega(0)), normal to it. A "weak" shear flow, with rate 2epsilon of the same order of the Poincaré "small" ratio epsilon , is needed for balancing the gyroscopic torque, so that the whole flow satisfies Euler's equations in the precessing frame (the so-called admissibility conditions). The base flow case with vertical shear (its cross-gradient direction is aligned with the main angular velocity) corresponds to Mahalov's [Phys. Fluids A 5, 891 (1993)] precessing infinite cylinder base flow (ignoring boundary conditions), while the base flow case with horizontal shear (its cross-gradient direction is normal to both main and precessing angular velocities) corresponds to the unbounded precessing rotating shear flow considered by Kerswell [Geophys. Astrophys. Fluid Dyn. 72, 107 (1993)]. We show that both these base flows satisfy the admissibility conditions and can support disturbances in terms of advected Fourier modes. Because the admissibility conditions cannot select one case with respect to the other, a more physical derivation is sought: Both flows are deduced from Poincaré's [Bull. Astron. 27, 321 (1910)] basic state of a precessing spheroidal container, in the limit of small epsilon . A Rapid distortion theory (RDT) type of stability analysis is then performed for the previously mentioned disturbances, for both base flows. The stability analysis of the Kerswell base flow, using Floquet's theory, is recovered, and its counterpart for the Mahalov base flow is presented. Typical growth rates are found to be the same for both flows at very small epsilon , but significant differences are obtained regarding growth rates and widths of instability bands, if larger epsilon values, up to 0.2, are considered. Finally

Resolving the clumpy circumstellar environment of the B[e] supergiant LHA 120-S 35

Science.gov (United States)

Torres, A. F.; Cidale, L. S.; Kraus, M.; Arias, M. L.; Barbá, R. H.; Maravelias, G.; Borges Fernandes, M.

2018-05-01

. The outermost regions show a complex structure, outlined by fragmented clumps or partial-ring features of Ca II and O I. Additionally, we observe variations in the profiles of the only visible absorption features, the He I lines. Conclusions: We suggest that LHA 120-S 35 has passed through the red-supergiant (RSG) phase and evolves back bluewards in the Hertzsprung-Russell diagram. In this scenario, the formation of the complex circumstellar structure could be the result of the wind-wind interactions of the post-RSG wind with the previously ejected material from the RSG. The accumulation of material in the circumstellar environment could be attributed to enhanced mass-loss, probably triggered by stellar pulsations. However, the presence of a binary companion cannot be excluded. Finally, we find that LHA 120-S 35 is the third B[e] supergiant belonging to a young stellar cluster. Based on data acquired using (1) the du Pont Telescope at Las Campanas Observatory, Chile, under the programme CNTAC 2008-02 (PI: Barbá), (2) the MPG 2.2-m Telescope at La Silla Observatory, Chile, under the programme ID.: 094.A-9029(D) and under the agreement MPI-Observatório Nacional/MCTIC, Prog. ID.: 096.A-9030(A), (3) the J. Sahade 2.15-m Telescope at Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan, (4) the 8.1-m Telescope at Gemini South Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciěncia, Tecnologia e Inovacão (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), under the programme

The Understanding of Astronomy Concepts by Students from Basic Education of a Public School. (Spanish Title: El Entendimiento de Conceptos de Aastronmía Por Los Alumnos de Educación Básica en Una Escuela Pública.) O Entendimento de Conceitos de Astronomia Por Alunos da Educação Básica: O Caso de Uma Escola Pública Brasileira

Science.gov (United States)

Iria Machado, Daniel; dos Santos, Carlos

2011-07-01

We present the results obtained in a research on the comprehension of basic astronomical concepts, in which 561 students from fifth grade middle school to third grade high school of a public school of the city of Foz do Iguaçu (Brazil) took part. A test with 20 multiple-choice questions was applied to indentify the most common conceptions expressed by the students. This test was elaborated based on the literature about misconceptions and covered the following topics: the day-night cycle; the time zones; the seasons of the year; the phases of the Moon; the movement of the Moon; the apparent movement of the Sun in the celestial sphere; the eclipses; the dimensions and distances in the Universe; the brightness of the stars and its observation from Earth. Though a small progress was verified in the proportion of scientifically acceptable answers when comparing the eighth grade of middle school to the fifth, and the third grade of high school to the first, there was an overall predominance of alternative conceptions regarding most of the explored subjects, which persisted up to the last year of secondary school. The comparison to data found in this research made in other socio-cultural contexts revealed, in many aspects, similar notions and difficulties revealed by the students. Se presentan los resultados de una investigación sobre la comprensión de conceptos astronómicos básicos, en la cual participaron 561 estudiantes que cursaban entre el quinto grado de la enseñanza primaria y el tercer año de la enseñanza secundaria de una escuela pública de la ciudad de Foz do Iguaçu (Brasil). Se utilizó un test de 20 preguntas de opción múltiple para identificar las concepciones más comunes expresadas por los estudiantes. Este instrumento de recolección de datos se desarrolló en base a la literatura sobre las concepciones alternativas y trató los siguientes temas: el ciclo día-noche, los husos horarios, las estaciones del año, las fases de la Luna, el

The Shadow of a Gnomon Along a Year: Routine Observations and Teaching of Apparent Motion of the Sun and the Four Seasons. (Spanish Title: La Sombra de un Gnomon lo Largo de un Año: Observaciones de Rutina y la Enseñanza del Movimiento Aparente del Sol y Las Cuatro Estaciones.) A Sombra de um Gnômon ao Longo de um Ano: Observações Rotineiras e o Ensino do Movimento Aparente do Sol E das Quatro Estações

Science.gov (United States)

Trogello, Anderson Giovani; Danhoni Neves, Marcos Cesar; de Carvalho Rutz da Silva, Sani

2013-12-01

, al solsticio de junio, al equinoccio de septiembre y al solsticio de diciembre. Además, se dictaron clases teóricas en la sala de aula. Estos métodos buscaron construir conceptos en torno al movimiento aparente del Sol y la sucesión de las estaciones. Teniendo en cuenta los resultados de las actividades se aplicó una evaluación cuyos datos demuestran la existencia de un aprendizaje deseado por los estudiantes en cuanto a: el reconocimiento de los puntos cardinales, la descripción del movimiento solar aparente y la aparición de las estaciones y su alternancia a partir de observaciones astronómicas visuales sin instrumentos. Muitas concepções alternativas são reconhecidas entre os diversos grupos de estudantes, em especial nos da educação básica. Dentre elas, o movimento aparente do Sol, por mais quotidiano que seja, proporciona variadas interpretações. Deste modo, observar e registrar o movimento dos astros na abóboda celeste é uma tarefa necessária ao ensino de Astronomia. O trabalho que ora se apresenta propõe a apresentação dos resultados da observação do movimento aparente do Sol por intermédio da marcação da sombra de um gnômon vertical por alunos de uma turma do sexto ano do ensino fundamental de uma escola do campo do Paraná. O projeto em si ocorreu em quatro etapas, em datas próximas do equinócio de março, do solstício de junho, do equinócio de setembro e do solstício de dezembro. Além disso, foram desenvolvidas aulas teóricas em sala de aula. Tais métodos buscaram construir conceitos em torno da movimentação aparente do Sol e da alternância das estações do ano. Diante dos resultados provenientes das atividades desenvolvidas foi aplicada uma avaliação e os dados demonstraram um aprendizado desejado dos alunos quanto: ao reconhecimento dos pontos cardeais; à descrição do movimento solar aparente e a ocorrência das estações do ano e sua alternância a partir de observações astronômicas a olho nu.

On the calculation of line strengths, oscillator strengths and lifetimes for very large principal quantum numbers in hydrogenic atoms and ions by the McLean–Watson formula

International Nuclear Information System (INIS)

Hey, J D

2014-01-01

As a sequel to an earlier study (Hey 2009 J. Phys. B: At. Mol. Opt. Phys. 42 125701), we consider further the application of the line strength formula derived by Watson (2006 J. Phys. B: At. Mol. Opt. Phys. 39 L291) to transitions arising from states of very high principal quantum number in hydrogenic atoms and ions (Rydberg–Rydberg transitions, n > 1000). It is shown how apparent difficulties associated with the use of recurrence relations, derived (Hey 2006 J. Phys. B: At. Mol. Opt. Phys. 39 2641) by the ladder operator technique of Infeld and Hull (1951 Rev. Mod. Phys. 23 21), may be eliminated by a very simple numerical device, whereby this method may readily be applied up to n ≈ 10 000. Beyond this range, programming of the method may entail greater care and complexity. The use of the numerically efficient McLean–Watson formula for such cases is again illustrated by the determination of radiative lifetimes and comparison of present results with those from an asymptotic formula. The question of the influence on the results of the omission or inclusion of fine structure is considered by comparison with calculations based on the standard Condon–Shortley line strength formula. Interest in this work on the radial matrix elements for large n and n′ is related to measurements of radio recombination lines from tenuous space plasmas, e.g. Stepkin et al (2007 Mon. Not. R. Astron. Soc. 374 852), Bell et al (2011 Astrophys. Space Sci. 333 377), to the calculation of electron impact broadening parameters for such spectra (Watson 2006 J. Phys. B: At. Mol. Opt. Phys. 39 1889) and comparison with other theoretical methods (Peach 2014 Adv. Space Res. in press), to the modelling of physical processes in H II regions (Roshi et al 2012 Astrophys. J. 749 49), and the evaluation bound–bound transitions from states of high n during primordial cosmological recombination (Grin and Hirata 2010 Phys. Rev. D 81 083005, Ali-Haïmoud and Hirata 2010 Phys. Rev. D 82 063521

Hα3: an Hα imaging survey of HI selected galaxies from ALFALFA. II. Star formation properties of galaxies in the Virgo cluster and surroundings

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Gavazzi, G.; Fumagalli, M.; Fossati, M.; Galardo, V.; Grossetti, F.; Boselli, A.; Giovanelli, R.; Haynes, M. P.

2013-05-01

on observations taken at the observatory of San Pedro Martir (Baja California, Mexico), belonging to the Mexican Observatorio Astronómico Nacional.

Formation of interstellar anions

Science.gov (United States)

Senent, Maria Luisa

2012-05-01

Formation of interstellar anions: M.L. Senent. The recent detection of negative charged species in the ISM1 has instigated enthusiasm for anions in the astrophysical community2. Many of these species are new and entail characterization. How they are formed in astrophysical sources is a question of major relevance. The anion presence in ISM was first predicted theoretically on the basis of electron affinities and on the negative linear chain molecular stabilities. Although very early, they were considered in astrochemical models3-4, their discovery is so recent because their abundances seem to be relatively low. These have to be understood in terms of molecular stabilities, reaction probabilities and radiative and collisional excitations. Then, we present our theoretical work on even carbon chains type Cn and CnH (n=2,4,6) focused to the understanding of anion abundances. We use highly correlated ab initio methods. We performed spectroscopic studies of various isomers that can play important roles as intermediates5-8. In previous papers9-10, we compared C2H and C2H- collisional rates responsible for observed line intensities. Actually, we study hydrogen attachment (Cn +H → CnH and Cn- +H → CnH-) and associative detachment processes (Cn- +H → CnH +e-) for 2, 4 and 6 carbon atom chains11. [1] M.C.McCarthy, C.A.Gottlieb, H.Gupta, P.Thaddeus, Astrophys.J, 652, L141 (2006) [2] V.M.Bierbaum, J.Cernicharo, R.Bachiller, eds., 2011, pp 383-389. [3] A. Dalgarno, R.A. Mc Cray, Astrophys.J,, 181, 95 (1973) [4] E. Herbst E., Nature, 289, 656 (1981); [5] H.Massó, M.L.Senent, P.Rosmus, M.Hochlaf, J.Chem.Phys., 124, 234304 (2006) [6] M.L.Senent, M.Hochlaf, Astrophys. J. , 708, 1452(2010) [7] H.Massó, M.L.Senent, J.Phys.Chem.A, 113, 12404 (2009) [8] D. Hammoutene, M.Hochlaf, M.L.Senent, submitted. [9] A. Spielfiedel, N. Feautrier, F. Najar, D. ben Abdallah, F. Dayou, M.L. Senent, F. Lique, Mon.Not.R.Astron.Soc., 421, 1891 (2012) [10] F.Dumouchel, A, Spielfieldel , M

Two new pulsating low-mass pre-white dwarfs or SX Phoenicis stars?

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Corti, M. A.; Kanaan, A.; Córsico, A. H.; Kepler, S. O.; Althaus, L. G.; Koester, D.; Sánchez Arias, J. P.

2016-03-01

Context. The discovery of pulsations in low-mass stars opens an opportunity to probe their interiors and determine their evolution by employing the tools of asteroseismology. Aims: We aim to analyse high-speed photometry of SDSS J145847.02+070754.46 and SDSS J173001.94+070600.25 and discover brightness variabilities. In order to locate these stars in the Teff - log g diagram, we fit optical spectra (SDSS) with synthetic non-magnetic spectra derived from model atmospheres. Methods: To carry out this study, we used the photometric data we obtained for these stars with the 2.15 m telescope at CASLEO, Argentina. We analysed their light curves and applied the discrete Fourier transform (FT) to determine the pulsation frequencies. Finally, we compare both stars in the Teff - log g diagram, with two known pre-white dwarfs and seven pulsating pre-ELM white dwarf stars, δ Scuti, and SX Phe stars Results: We report the discovery of pulsations in SDSS J145847.02+070754.46 and SDSS J173001.94+070600.25. We determine their effective temperature and surface gravity to be Teff = 7972 ± 200 K, log g = 4.25 ± 0.5 and Teff = 7925 ± 200 K, log g = 4.25 ± 0.5, respectively. With these parameters, these new pulsating low-mass stars can be identified with either ELM white dwarfs (with ~0.17 M⊙) or more massive SX Phe stars. We identified pulsation periods of 3278.7 and 1633.9 s for SDSS J145847.02+070754.46 and a pulsation period of 3367.1 s for SDSS J173001.94+070600.25. These two new objects, together with those of Maxted et al. (2013, 2014), indicate the possible existence of a new instability domain towards the late stages of evolution of low-mass white dwarf stars, although their identification with SX Phe stars cannot be discarded. Visiting Astronomer, Complejo Astronómico El Leoncito operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.

Deep multi-frequency rotation measure tomography of the galaxy cluster A2255

Science.gov (United States)

Pizzo, R. F.; de Bruyn, A. G.; Bernardi, G.; Brentjens, M. A.

2011-01-01

available in electronic form at http://www.aanda.org. To request the RM cubes in FITS format, please contact R. F. Pizzo at: pizzo@astron.nl

Questões mais freqüentes na área de astronomia

Science.gov (United States)

Segundo, H. A. S.; Garcia, G. C.; Caretta, C. A.; Lima, F. P.

2003-08-01

É amplamente reconhecido que as pessoas em geral têm grande fascínio e interesse pela Astronomia. Por outro lado, o conteúdo dessa área incluído no ensino formal está longe de ser abrangente e suficiente para suprir a demanda. Esse interesse permite otimizar a divulgação e o ensino não formal de Astronomia aliando a adequação do conteúdo à expectativa das pessoas. Nesse intuito, nosso trabalho busca mapear que assuntos da Astronomia despertam mais a atenção e o interesse das pessoas e o quanto disso é estimulado pela mídia, que freqüentemente aproveita-se desse interesse de forma sensacionalista, trazendo contribuições positivas e negativas. Para esta avaliação, utilizamos as pesquisas específicas e de caracterização do público que freqüentou o MAst nos anos de 2001 a 2003, pesquisa das matérias de Astronomia veiculadas na mídia escrita da cidade do Rio de Janeiro no mesmo período, além da base de dados do programa Pergunte a um astrônomo, realizado no Observatório Nacional nos anos de 1997 a 1999. Para a análise dos dados, dividimos as perguntas em dez categorias, cada uma com suas subcategorias, tomando como referência as divisões, comissões e grupos de trabalho da IAU. Apresentamos neste trabalho os resultados dessa pesquisa, que incluem, entre outros, a predominância de questões nas categorias Observação do Céu e Sistemas Planetários enquanto nos jornais dominam as notícias de Sistemas Planetários e Espaço & Astronáutica. Outro resultado interessante indicou que as dúvidas de crianças do ensino fundamental se concentram em algumas categorias enquanto as questões de adultos são mais distribuídas por todas as categorias. Os resultados dessa pesquisa serão aplicados diretamente no aperfeiçoamento das atividades do Programa de Observação de Céu, bem como na elaboração de novos projetos e eventos realizados no MAst.

On the Generation of Hydrodynamic Shocks by Mixed Beams and Occurrence of Sunquakes in Flares

Science.gov (United States)

Zharkova, Valentina; Zharkov, Sergei

2015-11-01

Observations of solar flares with sunquakes by space- and ground-based instruments reveal essentially different dynamics of seismic events in different flares. Some sunquakes are found to be closely associated with the locations of hard X-ray (HXR) and white-light (WL) emission, while others are located outside either of them. In this article we investigate possible sources causing a seismic response in a form of hydrodynamic shocks produced by the injection of mixed (electron plus proton) beams, discuss the velocities of these shocks, and the depths where they deposit the bulk of their energy and momentum. The simulation of hydrodynamic shocks in flaring atmospheres induced by electron-rich and proton-rich beams reveals that the linear depth of the shock termination is shifted beneath the level of the quiet solar photosphere on a distance from 200 to 5000 km. The parameters of these atmospheric hydrodynamic shocks are used as initial condition for another hydrodynamic model developed for acoustic-wave propagation in the solar interior (Zharkov, Mon. Not. Roy. Astron. Soc. 431, 3414, 2013). The model reveals that the depth of energy and momentum deposition by the atmospheric shocks strongly affects the propagation velocity of the acoustic-wave packet in the interior. The locations of the first bounces from the photosphere of acoustic waves generated in the vicinity of a flare are seen as ripples on the solar surface, or sunquakes. Mixed proton-dominated beams are found to produce a strong supersonic shock at depths 200 - 300 km under the level of the quiet-Sun photosphere and in this way produce well-observable acoustic waves, while electron-dominated beams create a slightly supersonic shock propagating down to 5000 km under the photosphere. This shock can only generate acoustic waves at the top layers beneath the photosphere since the shock velocity very quickly drops below the local sound speed. The distance Δ of the first bounce of the generated acoustic waves

Search for a Variation of Fundamental Constants

Science.gov (United States)

Ubachs, W.

2013-06-01

Since the days of Dirac scientists have speculated about the possibility that the laws of nature, and the fundamental constants appearing in those laws, are not rock-solid and eternal but may be subject to change in time or space. Such a scenario of evolving constants might provide an answer to the deepest puzzle of contemporary science, namely why the conditions in our local Universe allow for extreme complexity: the fine-tuning problem. In the past decade it has been established that spectral lines of atoms and molecules, which can currently be measured at ever-higher accuracies, form an ideal test ground for probing drifting constants. This has brought this subject from the realm of metaphysics to that of experimental science. In particular the spectra of molecules are sensitive for probing a variation of the proton-electron mass ratio μ, either on a cosmological time scale, or on a laboratory time scale. A comparison can be made between spectra of molecular hydrogen observed in the laboratory and at a high redshift (z=2-3), using the Very Large Telescope (Paranal, Chile) and the Keck telescope (Hawaii). This puts a constraint on a varying mass ratio Δμ/μ at the 10^{-5} level. The optical work can also be extended to include CO molecules. Further a novel direction will be discussed: it was discovered that molecules exhibiting hindered internal rotation have spectral lines in the radio-spectrum that are extremely sensitive to a varying proton-electron mass ratio. Such lines in the spectrum of methanol were recently observed with the radio-telescope in Effelsberg (Germany). F. van Weerdenburg, M.T. Murphy, A.L. Malec, L. Kaper, W. Ubachs, Phys. Rev. Lett. 106, 180802 (2011). A. Malec, R. Buning, M.T. Murphy, N. Milutinovic, S.L. Ellison, J.X. Prochaska, L. Kaper, J. Tumlinson, R.F. Carswell, W. Ubachs, Mon. Not. Roy. Astron. Soc. 403, 1541 (2010). E.J. Salumbides, M.L. Niu, J. Bagdonaite, N. de Oliveira, D. Joyeux, L. Nahon, W. Ubachs, Phys. Rev. A 86, 022510

Estudo da região HII galática NGC 2579

Science.gov (United States)

Riffel, R.; Copetti, M. V. F.

2003-08-01

Desde a descoberta dos gradientes de abundância química em galáxias espirais, as regiões HII galáticas têm sido intensamente estudadas com o objetivo de determinar a forma do gradiente de abundância química na Via-Láctea. Entretanto, a forma do gradiente galático continua controversa e existem muitas regiões HII que continuam inexploradas. A região HII galática NGC 2579 é um objeto que aparece em imagens Ha, como uma pequena mancha brilhante de aproximadamente 2 segundos de arco de diâmetro a 20 segundos de arco ao leste de RCW 20, sendo NGC 2579 muitas vezes confundida com esta última. Apesar de seu alto brilho superficial, NGC 2579 é um objeto pouco estudado provavelmente por problemas de identificação deste objeto. Como parte de um projeto de reavaliação dos gradientes de abundância química das regiões HII na Via-Láctea, estamos realizando um estudo extensivo das propriedades físicas básicas como temperatura eletrônica, densidade eletrônica e composição química da região HII galática NGC 2579. Analisamos dados espectrofotométricos de fenda longa na faixa de 3700Å a 7750Å obtidos com o telescópio de 1.52 m do ESO, Chile, em 2002. Determinamos a temperatura eletrônica usando a razão entre as linhas do [OIII] (l4959+l5007/l4363) e a densidade eletrônica pela razão entre as linhas do [SII] (l6716/l6731). As abundâncias químicas do O, N, Cl, S, Ne e He foram determinadas. Realizamos um estudo de imagens fotométricas nas bandas UBVRI obtidas em 2000 no observatório astronômico San Pedro Mártir, México, para identificar e classificar as estrelas ionizantes de NGC 2579 e determinar a distância deste objeto.

Poluição atmosférica e atendimentos por pneumonia e gripe em São Paulo, Brasil

Directory of Open Access Journals (Sweden)

Martins Lourdes Conceição

2002-01-01

Full Text Available OBJETIVO: Investigar os efeitos causados pela poluição atmosférica na morbidade por pneumonia e por gripe em idosos entre 1996 e 1998. MÉTODOS: Foram obtidos dados diários de atendimentos por pneumonia e gripe para idosos em pronto-socorro médico de um hospital-escola de referência no Município de São Paulo, SP, Brasil. Os níveis diários de CO, O3, SO2, NO2 e PM10 foram obtidos na Companhia de Tecnologia de Saneamento Ambiental, e os dados diários de temperatura e umidade relativa do ar foram obtidos no Instituto Astronômico e Geofísico da USP. Para verificar a relação existente entre pneumonia e gripe e poluição atmosférica, utilizou-se o modelo aditivo generalizado de regressão de Poisson, tendo como variável dependente o número diário de atendimentos por pneumonia e gripe e como variáveis independentes as concentrações médias diárias dos poluentes atmosféricos. A análise foi ajustada para sazonalidade de longa duração (número de dias transcorridos, sazonalidade de curta duração (dias da semana, temperatura mínima, umidade média, períodos de rodízio e os atendimentos por doenças não-respiratórias em idosos. RESULTADOS: O3 e SO2 estão diretamente associados à pneumonia e à gripe, independentemente das variáveis de controle. Porém, na análise conjunta, eles perdem sua significância estatística. Pôde-se observar que um aumento interquartil (25%-75% para o O3 (38,80 mig/m³ e SO2 (15,05 mig/m³ levaram a um acréscimo de 8,07% e 14,51%, respectivamente, no número de atendimentos por pneumonia e gripe em idosos. CONCLUSÕES: Os resultados sugerem que a poluição atmosférica promove efeitos adversos para a saúde de idosos.

Conhecimento Científico e Cotidiano em Astronomia: Uma Investigação com Alunos da Educação Básica

Science.gov (United States)

Vieira, J. B.; Longhini, M. D.

2011-12-01

Este texto apresenta resultados de uma investigação que teve como objetivo, investigar como os conhecimentos científicos e do cotidiano relacionados a essa área de conhecimento apresentam na escola de Educação Básica, especialmente, em alunos do Ensino Médio prestes a deixar Educação Básica. Para realização da pesquisa, utilizamos como recurso metodológico a aplicação de um questionário estruturado contendo 47 questões, organizadas em duas categorias: Conhecimento Cotidiano e Conhecimento Científico. As questões da categoria “Conhecimento Cotidiano” possuíam afirmações relacionadas a crendices, contos populares, especulações e temáticas do gênero, as quais, geralmente, estão fora do círculo de discussão da comunidade científica, talvez por não serem consideradas como objeto de estudo da ciência. As questões da categoria “Conhecimento Científico” são relacionadas a conteúdos específicos de Astronomia, as quais são compartilhadas pela comunidade científica e aceitas, pelo menos provisoriamente, como possuindo fundamentação científica. Concluímos que, possuem ainda concepções de temas Astronômicos persistentes à mudança, por exemplo, fases da Lua relacionadas à melhor período para corte de cabelo e também para plantio; estrela cadente e ocasião perfeita para se fazer um pedido. Entretanto, podemos observar no que diz respeito a mitos e superstições, que quase não existe influência destes entre os alunos. Portanto, ao trabalharmos com os alunos determinados conceitos científicos, é importante lembrarmos que o professor não opera no vazio; os alunos são sujeitos de saberes, práticas e, dessa forma constroem e reconstroem saberes. Cabe ao professor ouvir os estudantes reconstruindo junto deles conceitos científicos. Acreditamos que o ensino de Ciências na Educação Básica deve lidar criticamente com o conhecimento cotidiano e científico e, assim, efetivar a Ciência como disciplina educativa

Positron astrophysics and areas of relation to low-energy positron physics

International Nuclear Information System (INIS)

Guessoum, N.

2014-01-01

I briefly review our general knowledge of positron astrophysics, focusing mostly on the theoretical and modelling aspects. The experimental/observational aspects of the topic have recently been reviewed elsewhere [E. Churazov et al., Mon. Nat. R. Astron. Soc. 411, 1727 (2011); N. Prantazos et al., Rev. Mod. Phys. 83, 1001 (2011)]. In particular, I highlight the interactions and cross sections of the reactions that the positrons undergo in various cosmic media. Indeed, these must be of high interest to both the positron astrophysics community and the low-energy positron physics community in trying to find common areas of potential collaboration for the future or areas of research that will help the astrophysics community make further progress on the problem. The processes undergone by positrons from the moments of their birth to their annihilation (in the interstellar medium or other locations) are thus examined. The physics of the positron interactions with gases and solids (dust grains) and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation take place, are briefly reviewed. An explanation is given about how all the relevant physical information is taken into account in order to calculate annihilation rates and spectra of the 511 keV emission in the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. In particular, an attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of low-energy positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place

Desenvolvimento das câmeras de raios-X duros do satélite MIRAX

Science.gov (United States)

Braga, J.; Rothschild, R.; Staubert, R.; Heise, J.; Remillard, R.; D'Amico, F.; Jablonski, F.; Mejía, J.; Carvalho, H.; Heindl, B.; Matteson, J.; Kendziorra, E.; Wilms, J.; in't Zand, J.; Kuulkers, E.

2003-08-01

O MIRAX (Monitor e Imageador de RAios-X) é um projeto de desenvolvimento de um pequeno satélite astronômico de raios-X (~200 kg, ~240 W). A estratégia básica da missão será observar continuamente (~9 meses por ano) a região central (~1000 graus2) do plano Galáctico e realizar estudos espectroscópicos de banda larga (2-200 keV) e alta sensibilidade de um grande conjunto de fontes através de imagens com resolução de ~6'. Isso proporcionará uma cobertura inédita do "espaço de descobertas" através da detecção, localização, identificação e estudo detalhado de fenômenos imprevisíveis, tais como transientes fracos de raios-X, novas rápidas de raios-X e bursts de raios gama, assim como o estudo de fontes com emissão persistente. Neste trabalho apresentamos o projeto das duas câmeras de raios-X duros (CXDs) do MIRAX, que irão operar na faixa de 10 a 200 keV. Cada CXD consistirá de um plano de detectores CZT (Cd0,9Zn0,1Te) de 0,5 mm de resolução espacial e 370 cm2 de área total, e de uma máscara codificada com elementos quadrados de 1,3 mm de lado e 0,5 cm de espessura. A máscara terá dimensões de 315 cm ´ 275 cm e será montada a 700 cm de distância dos detectores. Com essa configuração as CXDs terão 6' de resolução angular e, quando colocadas a um ângulo de 29° entre si, as duas câmeras propiciam um campo totalmente codificado de 39° ´ 6°12' e um campo total de 76° ´ 44°. Serão apresentadas simulações de observações da região do plano Galáctico com o conjunto formado pelas duas CXDs.

Variaciones seculares de período en las RR Lyrae de ω~Centauri

Science.gov (United States)

Marraco, H. G.; Milesi, G. E.

Utilizando 689 observaciones de 35 estrellas RR Lyrae del cúmulo globular ω Centauri hemos obtenido nuevas determinaciones de sus períodos y sus correspondientes variaciones seculares. Las observaciones fueron obtenidas de la literatura con la excepción de un grupo 66 determinaciones que se presentan por vez primera aquí. Utilizando el parámetro testigo σ descripto en Marraco & Muzzio (Publ. Astron. Soc. Pacific 92, 700, 1980), hemos realizado un ajuste bidimensional en P y β (donde β es la variación secular del período). Con este fin la totalidad de las 689 observaciones fueron llevadas a un sistema fotométrico común. Para esto se realizó un cuidadoso análisis de los numerosos errores en la identificación de las estrellas de las series de comparación. Los resultados de los ajustes bidimensionales fueron analizados utilizando técnicas de procesamiento de imágenes. Con este fin el parámetro de ajuste σ fue representado como función de P y β. En las imágenes resultantes se buscaron los mínimos y al menor de ellos se lo aceptó como período instantáneo verdadero y su variación secular β. La determinación precisa de cada parámetro se realizó mediante ajuste de gaussianas y se determinaron sus errores. A modo de ejemplo la variable #8 fue analizada en una matriz de 501 × 501 elementos representando el parámetro σ para valores comprendidos entre 0,521034 son P = 0,5212859±0,0000001 días y β 14,012±,010×10-10 días/día respectivamente. Con estos valores el parámetro testigo resulta σ= 0,127 . Si no se tiene en cuenta la variación secular del período y se busca aquél de mejor ajuste para β = 0, se obtiene P = 0,5212960 días, pero entonces el parámetro de ajuste resulta tan alto como σ = 0,23 .

Evolution of the Astronomy Concepts Along Basic Education Cycle. (Breton Title: Evolução dos Conceitos de Astronomia no Decorrer da Educação Básica.) La Evolución de los Conceptos de Astronomía Durante la Educación Básica

Science.gov (United States)

Darroz, Luiz Marcelo; da Rosa, Cleci Werner; Becker da Rosa, Álvaro; Samudio Pèrez, Carlos Ariel

2014-07-01

learning of astronomy in basic education. Embora a astronomia seja considerada uma das ciências mais antigas da humanidade e ainda que a compreensão de seus conceitos tenha trazido enormes avanços para a Ciência e, consequentemente, para a sociedade, observa-se que uma parcela significativa de pessoas encontra-se à margem desses conhecimentos. De acordo com os Parâmetros Curriculares Nacionais para a Educação Básica, cabe à escola a difusão dos conceitos cientificamente corretos, entre eles os relacionados à área de astronomia. Pertinente a essa questão, apresenta-se uma pesquisa realizada com 140 estudantes do nono ano do ensino fundamental e com 120 estudantes da terceira série do ensino médio de quatro escolas da região de Passo Fundo/RS. Buscou-se averiguar, por meio de um questionário composto de questões abertas e de múltipla escolha, o conhecimento desse grupo de estudantes acerca de termos e fenômenos astronômicos básicos e, também, verificar se o índice de acertos cresce à medida que eles avançam nas diferentes e gradativas séries dos ensinos fundamental e médio. De modo geral, os resultados apresentados demonstram que o ensino de astronomia na educação básica enfrenta deficiências. Das 20 questões investigadas, em 17 os índices de acertos são semelhantes nas respostas dadas por estudantes de nível fundamental e médio, revelando que muitas concepções equivocadas permanecem ao longo da educação básica. Isso evidencia que tais temas não são - ou são pouco - abordados durante esses dois níveis de escolarização. Assim, conclui-se que a discussão dos conceitos relacionados com a astronomia deve receber maior ênfase na abordagem dos diferentes conteúdos, sendo necessária uma ação nacional em prol do seu ensino. Acredita-se que essa ação nacional deve estar apoiada em um pilar triplo de atores coletivos: comunidade científica, comunidade astronômica semiprofissional e comunidade escolar. Por fim, esse pilar seria

Development of Educational Resources to Include the Teaching of Astronomy in the First Years of the Basic Education. (Spanish Title: Desarrollo de Recursos Pedagógicos Para Incluir la Enseñanza de la Astronomía en los Primeros Años de la Educación Básica.) Desenvolvimento de Recursos Pedagógicos Para Inserir o Ensino de Astronomia nas Séries Iniciais do Ensino Fundamental

Science.gov (United States)

da Silva Morett, Samara; de Oliveira Souza, Marcelo

2010-07-01

ía y la vida cotidiana de los estudiantes. La inclusión de la astronomía en la escuela primaria es una manera de demostrar a los estudiantes cómo este campo está presente de forma activa en su vida cotidiana. Las clases que participan en el proyecto participaron en un estudio con el objetivo de proporcionar información a los conocimientos previos que tenían sobre los temas de la astronomía que se examinaron durante el proyecto. Con los experimentos realizados, y la ayuda de las nuevas tecnologías, conceptos astronómicos fueron presentados a los estudiantes de 4to y 5to año de la educación básica de una escuela municipal de Campos dos Goytacazes (RJ). Después de las presentaciones nuevos datos fueran colectados y se han llevado a cabo con el fin de verificar el nivel de aprendizaje alcanzado y se observó que el método utilizado fue una herramienta importante para ayudar al proceso de enseñanza y aprendizaje. El proyecto logró resultados satisfactorios. Neste trabalho será apresentado o desenvolvimento de recursos pedagógicos para a apresentação de conceitos de astronomia nas séries iniciais do ensino fundamental. Este material é composto por apresentações realizadas com o uso de novos recursos tecnológicos, pela fabricação de experimentos e a discussão de curiosidades relativas a esta área de conhecimento. Os experimentos foram construídos com material de baixo custo com o objetivo de permitir que os alunos envolvidos pudessem refazê-los em outras ocasiões. O material apresentado busca enfatizar a relação entre a astronomia e o cotidiano dos alunos. A inclusão da astronomia no ensino fundamental e uma forma de demonstrar aoestudante como esta área está presente de forma ativa em seu cotidiano. As turmas envolvidas no projeto participaram de uma pesquisa com o objetivo de obter dados relativos ao conhecimento prévio que possuíam sobre os tópicos de astronomia que foram considerados no decorrer do projeto. Com os experimentos

Exoplanets -New Results from Space and Ground-based Surveys

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Udry, Stephane

). TandEM: Titan and Enceladus mission. Experimenta( Astron-omy, 23, 893-946. 3. Coustenis, A., Hirtzig, M., 2009. Cassini-Huygens results on Titan's surface. Research in Astronomy and Astrophysics 9, 249-268. 4. Coustenis et al., 2010, Titan trace gaseous composition from CIRS at the end of the Cassini-Huygens prime mission Icarus, in press. 5. Flasar, F. M., et al., 2005. Titan's atmospheric temperatures, winds, and composition. Science, 308, 975-978. 6. Fulchignoni, M., et al, 2005. In situ measurements of the physical characteristics of Titan's environment. Nature, 438, 785-791, doi:10.1038/nature04126. 7. Lebreton, J-P., Coustenis, A., et al., 2009. Results from the Huygens probe on Titan. Astron. Astrophys. Rev. 17, 149-179. 8. Tomasko, M. G., et al., 2005. Rain, winds and haze during the Huygens probe's descent to Titan's surface. Nature, 438, 765-778, doi: 10. 1038/nature04126.

The Exploration of Titan and the Saturnian System

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Coustenis, Athena

). TandEM: Titan and Enceladus mission. Experimenta( Astron-omy, 23, 893-946. 3. Coustenis, A., Hirtzig, M., 2009. Cassini-Huygens results on Titan's surface. Research in Astronomy and Astrophysics 9, 249-268. 4. Coustenis et al., 2010, Titan trace gaseous composition from CIRS at the end of the Cassini-Huygens prime mission Icarus, in press. 5. Flasar, F. M., et al., 2005. Titan's atmospheric temperatures, winds, and composition. Science, 308, 975-978. 6. Fulchignoni, M., et al, 2005. In situ measurements of the physical characteristics of Titan's environment. Nature, 438, 785-791, doi:10.1038/nature04126. 7. Lebreton, J-P., Coustenis, A., et al., 2009. Results from the Huygens probe on Titan. Astron. Astrophys. Rev. 17, 149-179. 8. Tomasko, M. G., et al., 2005. Rain, winds and haze during the Huygens probe's descent to Titan's surface. Nature, 438, 765-778, doi: 10. 1038/nature04126.

Sistemas Correctores de Campo Para EL Telescopio Cassegrain IAC80

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Galan, M. J.; Cobos, F. J.

1987-05-01

El proyecto de instrumentación de mayor importancia que ha tenido el Instituto de Astrofisica de Canarias en los últimos afios ha sido el diseflo y construcción del te1escopio IAC8O. Este requería del esfuerzo con junto en mec´nica, óptica y electrónica, lo que facilitó la estructuración y el crecimiento de los respectivos grupos de trabajo, que posteriormente se integraron en departamentos En su origen (1977), el telescopio IAC80 fue concebido como un sistema clásico tipo Cassegrain, con una razón focal F/i 1.3 para el sistema Casse grain y una razón focal F/20 para el sistema Coudé. Posteriormente, aunque se mantuvo la filosofia de que el sistema básico fuera el F/11.3, se consideró conveniente el diseño de secundarios para razones focales F/16 y F/32, y se eliminó el de F/20. Sin embargo, dada la importancia relativa que un foco estrictamente fotográfico tiene en un telescopio moderno, diseñado básicamente para fotometría fotoeléctrica y con un campo util mínimamente de 40 minutos de arco, se decídió Ilevar a cabo el diseño de un secundario F/8 con un sistema corrector de campo, pero que estuviera formado únicamente por lentes con superficies esféricas para que asl su construcción fuera posible en España ó en México. La creciente utilización de detectores bidimensionales para fines de investigación astron6mica y la viabilidad de que en un futuro cercano éstos tengan un área sensible cada vez mayor, hicieron atractiva la idea de tener diseñado un sistema corrector de campo para el foco primario (F/3), con un campo útil mínimo de un grado, y también con la limitante de que sus componentes tuvieron sólamente supérficies esféricas. Ambos diseños de los sis-temas correctores de campo se llevaron a cabo, en gran medida, como parte de un proyecto de colaboración e intercambio en el área de diseño y evaluación de sistemas ópticos.

A proof of the cancellation of the redistribution tidal potential effects on the rotation of an elastic Earth model

Science.gov (United States)

Baenas, Tomás; Escapa, Alberto; Ferrándiz, Jose Manuel

2014-05-01

2010-22039-C02-02, and Universidad de Alicante project GRE11-08. Escapa, A., Getino, J., & Ferrándiz, J. M. 2004, Proc. Journées Sys. Ref., Ed. N. Capitaine, Paris, 70 Ferrándiz, J. M., Baenas, T., & Escapa, A. 2012, Geophys. Res. Abs., 14, EGU2012-6175 Krasinsky, G. A. 1999, Celest. Mech. Dyn. Astron., 75, 39 Lambert, S. & Mathews, P. M. 2006, A&A, 453, 363

Variability in Abundances of Meteorites in the Ordovician

Science.gov (United States)

Heck, P. R.; Schmitz, B.; Kita, N.

2017-12-01

not generate a supply of fragments that was long-lived enough to be still important today. Our results imply that the composition of the flux of meteorites to Earth is biased by discrete collisional events in the asteroid belt. [1] Schmitz B (2013) Chem Erde 73, 117; [2] Heck PR et al (2016) GCA 177, 120; [3] Heck PR et al (2017) Nat Astron 1, 35, DOI: 10.1038/s41550-016-0035.

Properties of optically selected BL Lacertae candidates from the SDSS

Science.gov (United States)

Kügler, S. D.; Nilsson, K.; Heidt, J.; Esser, J.; Schultz, T.

2014-09-01

Context. Deep optical surveys open the avenue for finding large numbers of BL Lac objects that are hard to identify because they lack the unique properties classifying them as such. While radio or X-ray surveys typically reveal dozens of sources, recent compilations based on optical criteria alone have increased the number of BL Lac candidates considerably. However, these compilations are subject to biases and may contain a substantial number of contaminating sources. Aims: In this paper we extend our analysis of 182 optically selected BL Lac object candidates from the SDSS with respect to an earlier study. The main goal is to determine the number of bona fide BL Lac objects in this sample. Methods: We examine their variability characteristics, determine their broad-band radio-UV spectral energy distributions (SEDs), and search for the presence of a host galaxy. In addition we present new optical spectra for 27 targets with improved signal-to-noise ratio with respect to the SDSS spectra. Results: At least 59% of our targets have shown variability between SDSS DR2 and our observations by more than 0.1-0.27 mag depending on the telescope used. A host galaxy was detected in 36% of our targets. The host galaxy type and luminosities are consistent with earlier studies of BL Lac host galaxies. Simple fits to broad-band SEDs for 104 targets of our sample derived synchrotron peak frequencies between 13.5 ≤ log 10(νpeak) ≤ 16 with a peak at log 10 ~ 14.5. Our new optical spectra do not reveal any new redshift for any of our objects. Thus the sample contains a large number of bona fide BL Lac objects and seems to contain a substantial fraction of intermediate-frequency peaked BL Lacs. Based on observations collected with the NTT on La Silla (Chile) operated by the European Southern Observatory under proposal 082.B-0133.Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA), operated jointly by the Max-Planck-Institut für Astronomie and the

Space weathering of small Koronis family members

Science.gov (United States)

Thomas, Cristina A.; Rivkin, Andrew S.; Trilling, David E.; Enga, Marie-therese; Grier, Jennifer A.

2011-03-01

The space weathering process and its implications for the relationships between S- and Q-type asteroids and ordinary chondrite meteorites is an often debated topic in asteroid science. Q-type asteroids have been shown to display the best spectral match to ordinary chondrites (McFadden, L.A., Gaffey, M.J., McCord, T.B. [1985]. Science 229, 160-163). While the Q-types and ordinary chondrites share some spectral features with S-type asteroids, the S-types have significantly redder spectral slopes than the Q-types in visible and near-infrared wavelengths. This reddening of spectral slope is attributed to the effects of space weathering on the observed surface composition. The analysis by Binzel et al. (Binzel, R.P., Rivkin, A.S., Stuart, J.S., Harris, A.W., Bus, S.J., Burbine, T.H. [2004]. Icarus 170, 259-294) provided a missing link between the Q- and S-type bodies in near-Earth space by showing a reddening of spectral slope in objects from 0.1 to 5 km that corresponded to a transition from Q-type to S-type asteroid spectra, implying that size, and therefore surface age, is related to the relationship between S- and Q-types. The existence of Q-type asteroids in the main-belt was not confirmed until Mothé-Diniz and Nesvorny (Mothé-Diniz, T., Nesvorny, D. [2008]. Astron. Astrophys. 486, L9-L12) found them in young S-type clusters. The young age of these families suggest that the unweathered surface could date to the formation of the family. This leads to the question of whether older S-type main-belt families can contain Q-type objects and display evidence of a transition from Q- to S-type. To answer this question we have carried out a photometric survey of the Koronis family using the Kitt Peak 2.1 m telescope. This provides a unique opportunity to compare the effects of the space weathering process on potentially ordinary chondrite-like bodies within a population of identical initial conditions. We find a trend in spectral slope for objects 1-5 km that shows the

NGC 4622:. A clear example of spiral density wave star formation unused in textbooks.

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Byrd, Gene G.

2018-06-01

Refer to the poster HST images or to http://heritage.stsci.edu/2002/03/index.html. The top northeastern (NE) arm of NGC 4622 winds outward clockwise (CW) showing beautiful “ beads on a string” blue stellar associations on the CONCAVE SIDE of the arm. These are nicely offset CW in position from the density concentration of old yellow stars in the arms. The displacement would result from aggregation of gas clouds as they orbit CW into a more slowly turning stellar disk arm pattern. There is a time delay until the associations form and light up on the concave side. Farther inward along the top NE arm, the lit-up associations occur in the MIDDLE of the stellar arm. This is characteristic of the co-rotation (CR) radius where the CW orbital angular rate of the gas clouds and the arm CW pattern speeds match. Just within CR, the association displacement from the stellar arm is opposite (CCW) onto the CONVEX SIDE of the arm. A similar displacement sequence from concave (outside CR), middle (at CR) to convex (inside CR) is seen along the lower southwestern arm. Why isn’t NGC 4622 featured in textbooks? A rather puzzling single stellar arm winds outward CCW from the center, opposite to the outer pair. The eastern edge of the disk (marked by dust cloud silhouettes) is the nearer edge. The NE portion radial velocity is away relative to the nucleus so the disk orbital motion is CW. The outer pair of arms thus winds outward to LEAD in the same direction as the CW orbital motion, contrary to typical arm winding. Actually, the leading pair of arms and single inner arm would make NGC 4622 even better for use in introductory astronomy texts. Students can debate the origin of this galaxy's strange arm pattern which, ironically, matches density wave predictions so well. This is better than simply reading a textbook and thinking that all is explained. See G. G. Byrd; T. Freeman; S. Howard; R. J. Buta (2008). Astron. J., 135, p. 408–413 and references there for observations and

Uma grade de perfis teóricos para estrelas massivas em transição

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Nascimento, C. M. P.; Machado, M. A.

2003-08-01

Na XXVIII Reunião Anual da Sociedade Astronômica Brasileira (2002) apresentamos uma grade de perfis calculados de acordo com os pontos da trajetória evolutiva de metalicidade solar, Z = 0.02 e taxa de perda de massa () padrão, para estrelas com massa inicial de 25, 40, 60, 85 e 120 massas solares. Estes perfis foram calculados com o auxílio de um código numérico adequado para descrever os ventos de objetos massivos, supondo simetria esférica, estacionaridade e homogeneidade. No presente trabalho, apresentamos a complementação da grade com os perfis teóricos relativos às trajetórias de Z = 0.02 com taxa de perda de massa dobrada em relação a padrão (2´), e de metalicidade Z = 0.008. Para cada ponto das três trajetórias obtemos os perfis teóricos de Ha, Hb, Hg e Hd, e como esperado eles se apresentam em pura emissão, pura absorção ou em P-Cygni. Para valores de taxa de perda de massa muito baixos (~10-7) não há formação de linhas, o que é visto nos primeiros pontos em todas as trajetórias. Em geral, para um mesmo ponto a componente de emissão diminui e a absorção aumenta de Ha para Hd. É verificado que as trajetórias com Z = 0.02 e padrão possuem menos circuitos (loops) do que as com metalicidade Z = 0.02 e 2´ padrão, e seus perfis são, em geral, menos intensos. Em relação a trajetória de Z = 0.008, verifica-se menos circuitos e maior variação em luminosidade, e seus perfis mostram-se em, algumas trajetórias, mais intensos. Verificamos também que, pontos distintos em uma mesma trajetória, apresentam perfis diferentes para valores similares de luminosidade e temperatura efetiva. Sendo assim, uma grade de perfis teóricos parece ser útil para fornecer uma informação preliminar sobre o estágio evolutivo de uma estrela massiva.

Modelagem numérica de ressacas na plataforma sudeste do Brasil a partir de cartas sinóticas de pressão atmosférica na superfície Numerical modeling of storm surges in the brazilian southeastern shelf using synopitc charts of atmospheric pressure at the surface

Directory of Open Access Journals (Sweden)

Ricardo de Camargo

1994-12-01

Full Text Available Um modelo numérico tri-dimensional, linear, barotrópico e de meso-escala, é usado para a plataforma sudeste brasileira, de maneira a representar a composição das principais componentes astronômicas de maré, sobrepostas a efeitos meteorológicos extremos, para períodos específicos de interesse. No entanto, como dados meteorológicos relativos a esta área são muito escassos e esparsos, foi utilizada uma metodologia de fornecimento de condições meteorológicas para o modelo de circulação oceânica, baseada somente em cartas sinóticas de pressão atmosférica na superfície. O campo de pressão foi bem representado, mas as intensidades calculadas para os ventos foram bem maiores do que as observadas na costa. Os resultados do modelo indicam que é possível associar o centro de alta pressão do Atlântico Sul e as correspondentes elevações de superfície paralelas à linha da costa a um sistema geostrófico de circulação oceânica. Por outro lado, a passagem de frentes frias na área induz sistemas transientes que modificam o padrão geostrófico, também mudando a configuração das isolinhas de elevação de superfície.A three-dimensional, linear, barotropic and meso-scale numerical model is used for the southeastern Brazilian shelf, in order to represent the composition of the main astronomical tidal constituents, superimposed to extreme meteorological effects, for specific periods of interest. However, meteorological data relative to this area are very few and sparse, so that a methodology to provide meteorological conditions to the oceanic circulation model was used, based only on atmospheric pressure charts at the surface. The pressure field was well represented, while the calculated wind speeds were much larger than the observed winds at the coast. The model results indicate that it is possible to associate the predominant high pressure center in the South Atlantic and the correspondent surface elevations parallel to the

Positron astrophysics and areas of relation to low-energy positron physics

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Guessoum, Nidhal

2014-05-01

I briefly review our general knowledge of positron astrophysics, focusing mostly on the theoretical and modelling aspects. The experimental/observational aspects of the topic have recently been reviewed elsewhere [E. Churazov et al., Mon. Nat. R. Astron. Soc. 411, 1727 (2011); N. Prantazos et al., Rev. Mod. Phys. 83, 1001 (2011)]. In particular, I highlight the interactions and cross sections of the reactions that the positrons undergo in various cosmic media. Indeed, these must be of high interest to both the positron astrophysics community and the low-energy positron physics community in trying to find common areas of potential collaboration for the future or areas of research that will help the astrophysics community make further progress on the problem. The processes undergone by positrons from the moments of their birth to their annihilation (in the interstellar medium or other locations) are thus examined. The physics of the positron interactions with gases and solids (dust grains) and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation take place, are briefly reviewed. An explanation is given about how all the relevant physical information is taken into account in order to calculate annihilation rates and spectra of the 511 keV emission in the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. In particular, an attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of low-energy positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place

Comportamiento del Helio en estrellas químicamente peculiares

Science.gov (United States)

Malaroda, S. M.; López García, Z.; Leone, F.; Catalano, F.

Las estrellas químicamente peculiares (CP) se caracterizan por tener deficiencias y sobreabundancias de algunos elementos químicos de hasta 106 veces la abundancia solar. Además presentan variaciones en las líneas espectrales. Se piensa que ello se debe a que los campos magnéticos presentes en este tipo de estrellas son principalmente dipolares, con un eje de simetría diferente del eje de rotación. La distribución de los elementos sobreabundantes y deficientes no es homogénea sobre la superficie estelar y las variaciones observadas serían una consecuencia directa de la rotación estelar. Entre los elementos con abundancia anómala se encuentra el Helio, cuyas líneas tienen intensidades que no son consistentes con una abundancia normal, que no puede ser determinada del modo usual, o sea, considerando una atmósfera con composición solar. Con el fin de determinar la abundancia de este elemento, se inició un estudio de estrellas anómalas de Helio, Hew y He strong. Además se determinarán las abundancias de otros elementos anómalos como ser el Si, Cr, Mg, Mn y Fe. Las mismas se determinan del modo tradicional, o sea: a) medida de los anchos equivalentes de las líneas de los distintos elementos analizados; b) adopción de la temperatura efectiva, gravedad y abundancia del Helio; c) cálculo del modelo de atmósfera d) comparación con las observaciones y reinicio de un proceso iterativo hasta lograr un acuerdo entre todos los parámetros analizados. Las observaciones se llevaron a cabo en el Complejo Astronómico El Leoncito. Se observaron setenta y ocho estrellas anómalas de Helio. En este momento se está procediendo a calcular las abundancias correspondientes a los distintos elementos químicos. Para ello se hace uso de los modelos de Kurucz, ATLAS9. Los cálculos NLTE de las líneas de Helio se llevan a cabo con el programa MULTI y se compararán con los realizados con el programa WIDTH9 de Kurucz (LTE), con el objeto de resaltar la importancia de

Macroclumping as solution of the discrepancy between Hα and P v mass loss diagnostics for O-type stars

Science.gov (United States)

Šurlan, B.; Hamann, W.-R.; Aret, A.; Kubát, J.; Oskinova, L. M.; Torres, A. F.

2013-11-01

observations collected with the Perek 2-m Telescope of the Ondřejov Observatory, Czech Republic.Based on observations taken at the Complejo Astronómico El Leoncito (CASLEO), operated under an agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, the Secretaría de Ciencia y Tecnología de la Nación, and the National Universities of La Plata, Córdoba, and San Juan.Appendix A is available in electronic form at http://www.aanda.org

Observational constraints for the circumstellar disk of the B[e] star CPD-52 9243

Science.gov (United States)

Cidale, L. S.; Borges Fernandes, M.; Andruchow, I.; Arias, M. L.; Kraus, M.; Chesneau, O.; Kanaan, S.; Curé, M.; de Wit, W. J.; Muratore, M. F.

2012-12-01

interferometric data are necessary to determine a possible binary nature of the star. Based on observations taken with: 1) Telescopes at Paranal ESO Observatory under the program 085.D-0454 and 385.D-0513A; 2) Gemini South/Phoenix instrument, science program GS-2010A-Q-41; 3) J. Sahade Telescope at Complejo Astronómico El Leoncito (CASLEO), operated under an agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, the Secretaría de Ciencia y Tecnología de la Nación and the National Universities of La Plata, Córdoba and San Juan.

Observational hints of radial migration in disc galaxies from CALIFA

Science.gov (United States)

Ruiz-Lara, T.; Pérez, I.; Florido, E.; Sánchez-Blázquez, P.; Méndez-Abreu, J.; Sánchez-Menguiano, L.; Sánchez, S. F.; Lyubenova, M.; Falcón-Barroso, J.; van de Ven, G.; Marino, R. A.; de Lorenzo-Cáceres, A.; Catalán-Torrecilla, C.; Costantin, L.; Bland-Hawthorn, J.; Galbany, L.; García-Benito, R.; Husemann, B.; Kehrig, C.; Márquez, I.; Mast, D.; Walcher, C. J.; Zibetti, S.; Ziegler, B.; Califa Team

2017-07-01

, in light of these results we cannot further quantify the importance of radial migration in shaping spiral galaxies, and other processes, such as recent star formation or satellite accretion, might play a role. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/604/A4

The Identification of Z-dropouts in Pan-STARRS1: Three Quasars at 6.5< z< 6.7

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Venemans, B. P.; Bañados, E.; Decarli, R.; Farina, E. P.; Walter, F.; Chambers, K. C.; Fan, X.; Rix, H.-W.; Schlafly, E.; McMahon, R. G.; Simcoe, R.; Stern, D.; Burgett, W. S.; Draper, P. W.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Magnier, E. A.; Metcalfe, N.; Morgan, J. S.; Price, P. A.; Tonry, J. L.; Waters, C.; AlSayyad, Y.; Banerji, M.; Chen, S. S.; González-Solares, E. A.; Greiner, J.; Mazzucchelli, C.; McGreer, I.; Miller, D. R.; Reed, S.; Sullivan, P. W.

2015-03-01

Luminous distant quasars are unique probes of the high-redshift intergalactic medium (IGM) and of the growth of massive galaxies and black holes in the early universe. Absorption due to neutral hydrogen in the IGM makes quasars beyond a redshift of z≃ 6.5 very faint in the optical z band, thus locating quasars at higher redshifts requires large surveys that are sensitive above 1 micron. We report the discovery of three new z\\gt 6.5 quasars, corresponding to an age of the universe of \\lt 850 Myr, selected as z-band dropouts in the Pan-STARRS1 survey. This increases the number of known z\\gt 6.5 quasars from four to seven. The quasars have redshifts of z = 6.50, 6.52, and 6.66, and include the brightest z-dropout quasar reported to date, PSO J036.5078 + 03.0498 with {{M}1450}=-27.4. We obtained near-infrared spectroscopy for the quasars, and from the Mg ii line, we estimate that the central black holes have masses between 5 × 108 and 4 × 109 {{M}⊙ } and are accreting close to the Eddington limit ({{L}Bol}/{{L}Edd}=0.13-1.2). We investigate the ionized regions around the quasars and find near-zone radii of {{R}NZ}=1.5-5.2 proper Mpc, confirming the trend of decreasing near-zone sizes with increasing redshift found for quasars at 5.7\\lt z\\lt 6.4. By combining RNZ of the PS1 quasars with those of 5.7\\lt z\\lt 7.1 quasars in the literature, we derive a luminosity-corrected redshift evolution of {{R}NZ,corrected}=(7.2+/- 0.2)-(6.1+/- 0.7)× (z-6) Mpc. However, the large spread in RNZ in the new quasars implies a wide range in quasar ages and/or a large variation in the neutral hydrogen fraction along different lines of sight. Based in part on observations collected at the European Southern Observatory, Chile, programs 179.A-2010, 092.A-0150, 093.A-0863, and 093.A-0574, and at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC). This paper

Estado Vital de la Materia. Su origen, su evolución y su futuro.

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J. Hernando Ordoñez

2001-04-01

Full Text Available

En este artlculo se hacen algunas observaciones sobre un estado de la materia (estado vital, propuesto para reemplazar el de materia viva, que se usa habitualmente.

La materia en estado vital se organiza por una fuerza interna, que podríamos calificar como inteligente, que hace que los átomos se orienten y se organicen con determinada finalidad para fabricar células, para modelar órganos y, éstos, para culminar su obra integrándose con la armonía más admirable, para constituirse en organismos ya sea vegetales o animales.

Los planetas no tienen materia en estado vital; son masas que giran y giran, aparentemente sin finalidad conocida. En cambio, en nuestro planeta una buena parte de su masa adquirió vida, lo que llamamos biomasa, que abarca todos los organismos vivos, tanto vegetales como animales, en una proporción tal que si se pudiera calcular su peso nos daría cifras astronómicas.

Sobre el futuro de nuestro sol los científicos predicen que en los próximos 1.100 millones de años aumentará su luminosidad en un 10%. Esto sobre calentará a la Tierra como consecuencia de un severo efecto de invernadero. El agua de los mares y océanos hervirá y la vida en el planeta se extinguirá.

El universo está constituido por energía y materia, que pueden transformarse la una en la otra. La energía se presenta en varias fases, entre ellas, en la energía eléctrica, la luz y el calor, cuya naturaleza íntima nos es tan desconocida. La materia también está en varios estados: sólido, líquido, gaseoso, iónico, molecular y coloidal.

En el presente estudio intento hacer algunas observaciones sobre otro estado de la materia, que he denominado estado vital, nombre que propongo para reemplazar el de materia viva, que se usa habitualmente. Par hacerlo me baso en una consideración elemental: los átomos que integran la biomasa terrestre son los mismos que constituyen la materia inerte, no están vivos. En

A fast parallel code for calculating energies and oscillator strengths of many-electron atoms at neutron star magnetic field strengths in adiabatic approximation

Science.gov (United States)

Engel, D.; Klews, M.; Wunner, G.

2009-02-01

equations for the expansion coefficients, which is solved numerically, and, since the direct and exchange interaction potential terms depend on the wave functions, in a self consistent way. The iteration procedure is initialized by distributing the electrons on magnetic sublevels according to the level scheme of the hydrogen atom in intense magnetic fields. To speed up the calculations, the code is parallelized. The parallelization strategy is: a) each processor calculates one or several electrons, depending on the total number of processors, b) single-particle wave functions are broadcast from each processor to every other processor. As the coefficient vectors in the B-spline basis are small (dim≈20-25), there is only little communication between the nodes. Typical speedups by a factor of 20 are obtained on a 26-processor cluster of HP Compaq dc57750. Running time: The test runs provided only require a few seconds using 2 processors. References: [1] K. Werner, S. Dreizler, The classical stellar atmosphere problem, in: H. Riffert, K. Werner (Eds.), Computational Astrophysics, Computational and Applied Mathematics, Elsevier, 1998. [2] H. Ruder, G. Wunner, H. Herold, F. Geyer, Atoms in Strong Magnetic Fields, Springer, Heidelberg, 1994. [3] P.B. Jones, Mon. Not. R. Astron. Soc. 216 (1985) 503. [4] D. Neuhauser, K. Langanke, S.E. Koonin, Phys. Rev. A 33 (1986) 2084. [5] M.C. Miller, D. Neuhauser, Mon. Not. R. Astron. Soc. 253 (1991) 107. [6] M. Rajagopal, R.W. Romani, M.C. Miller, Astrophys. J. 479 (1997) 347. [7] K. Mori, C.J. Hailey, Astrophys. J. 564 (2002) 914. [8] M. Klews, Discretization methods for the investigation of atoms in time dependent electric fields, and in extremely strong magnetic fields (in German), Doctoral Thesis, University of Tübingen, 2003, http://www.theo1.physik.unistuttgart. de/forschung/sfb382a15/klews2003.ps.gz.

Twenty-four-week effects of liraglutide on body composition, adherence to appetite, and lipid profile in overweight and obese patients with type 2 diabetes mellitus

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Rondanelli M

2016-03-01

Full Text Available Mariangela Rondanelli,1 Simone Perna,1 Paolo Astrone,2 Annalisa Grugnetti,2 Sebastiano Bruno Solerte,2 Davide Guido3,4 1Endocrinology and Nutrition Unit, Section of Human Nutrition, Department of Public Health, Experimental and Forensic Medicine, Agency for Elderly People Services, Santa Margherita Hospital, University of Pavia, Pavia, Italy; 2Section of Geriatrics and Gerontology, Department of Internal Medicine, Agency for Elderly People Services, Santa Margherita Hospital, University of Pavia, Pavia, Italy; 3Medical and Genomics Statistics Unit, Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy; 4Biostatistics and Clinical Epidemiology Unit, Department of Public Health, Experimental and Forensic Medicine, University of Pavia, Pavia, Italy Background: Liraglutide has well-known effects on glucose patterns. However, its several other metabolic properties are still controversial. Given this background, the aims of the present study are to evaluate the effects of 24-week liraglutide treatment on body composition, appetite, and lipid profile in overweight and obese type 2 diabetes mellitus (T2DM patients. Methods: A cohort study was carried out on overweight and obese T2DM patients with glycosylated hemoglobin A1c equal to 6% (42 mmol/mol-10% (86 mmol/mol, under a 3-month treatment (at least with maximal dose of metformin as stable regime, by adding liraglutide at doses up to 3 mg/d. Body composition markers were measured by dual-energy X-ray densitometry at baseline and after 24 weeks of liraglutide treatment. Glucose control was monitored by glucose, glycosylated hemoglobin A1c, insulin, and homeostasis model assessment. Finally, the appetite sensation and plasma lipids were also evaluated. Results: Twenty-eight subjects (male/female: 16/12, mean age: 58.75±9.33 years, body mass index: 34.13±5.46 kg/m2 were evaluated. Accounting for the adjustment for age, sex, and duration of diabetes, we noted significant

Possible Habitability of Ocean Worlds

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Noack, Lena; Höning, Dennis; Bredehöft, Jan H.; Lammer, Helmut

2014-05-01

of mass-radius relationships for silicate-rich and ice-rich planets up to 100 Earth masses. The Astrophysical Journal 693, 722-733. Wagner, F.W., Sohl, F., Hussmann, H., Grott, M., and Rauer, H. (2011). Interior structure models of solid exoplanets using material laws in the infinite pressure limit. Icarus 214, 366-376. Lammer, H., Bredehöft, J.H., Coustenis, A., Khodachenko, M.L., Kaltenegger, L., Grasset, O., Prieur, D., Raulin, F., Ehrenfreund, P., Yamauchi, M., Wahlund, J.-E., Grießmeier, J.-M., Stangl, G., Cockell, C.S., Kulikov, Yu.N., Grenfell, J.L., and Rauer, H. (2009). What makes a planet habitable? Astron Astrophys Rev 17, 181-249.

Thermal model of water and CO activity of Comet C/1995 O1 (Hale-Bopp)

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Gortsas, N.; Kührt, E.; Motschmann, U.; Keller, H. U.

2011-04-01

An investigation of the activity of Comet C/1995 O1 (Hale-Bopp) with a thermophysical nucleus model that does not rely on the existence of amorphous ice is presented. Our approach incorporates recent observations allowing to constrain important parameters that control cometary activity. The model accounts for heat conduction, heat advection, gas diffusion, sublimation, and condensation in a porous ice-dust matrix with moving boundaries. Erosion due to surface sublimation of water ice leads to a moving boundary. The movement of the boundary is modeled by applying a temperature remapping technique which allows us to account for the loss in the internal energy of the eroded surface material. These kind of problems are commonly referred to as Stefan problems. The model takes into account the diurnal rotation of the nucleus and seasonal effects due to the strong obliquity of Hale-Bopp as reported by Jorda et al. (Jorda, L., Rembor, K., Lecacheux, J., Colom, P., Colas, F., Frappa, E., Lara, L.M. [1997]. Earth Moon Planets 77, 167-180). Only bulk sublimation of water and CO ice are considered without further assumptions such as amorphous ices with certain amount of occluded CO gas. Confined and localized activity patterns are investigated following the reports of Lederer and Campins (Lederer, S.M., Campins, H. [2002]. Earth Moon Planets 90, 381-389) about the chemical heterogeneity of Hale-Bopp and of Bockelée-Morvan et al. (Bockelée-Morvan, D., Henry, F., Biver, N., Boissier, J., Colom, P., Crovisier, J., Despois, D., Moreno, R., Wink, J. [2009]. Astron. Astrophys. 505, 825-843) about a strong CO source at a latitude of 20°. The best fit to the observations of Biver et al. (Biver, N. et al. [2002]. Earth Moon Planets 90, 5-14) is obtained with a low thermal conductivity of 0.01 W m -1 K -1. This is in agreement with recent results of the Deep Impact mission to 9P/Tempel 1 (Groussin, O., A'Hearn, M.F., Li, J.-Y., Thomas, P.C., Sunshine, J.M., Lisse, C.M., Meech, K

Photometric and spectroscopic evidence for a dense ring system around Centaur Chariklo

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Duffard, R.; Pinilla-Alonso, N.; Ortiz, J. L.; Alvarez-Candal, A.; Sicardy, B.; Santos-Sanz, P.; Morales, N.; Colazo, C.; Fernández-Valenzuela, E.; Braga-Ribas, F.

2014-08-01

carbon, 30% of silicates and 10% of organics; no water ice was found on the surface. The ring, on the other hand, contains 20% of water ice, 40-70% of silicates, and 10-30% of tholins and small quantities of amorphous carbon. Partially based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile. DDT 291.C-5035(A). Based on observations carried out at the Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.

Resolving stellar populations with crowded field 3D spectroscopy

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Kamann, S.; Wisotzki, L.; Roth, M. M.

2013-01-01

effects of PSF mismatch and other systematics. We close with an outlook by applying our method to a simulated globular cluster observation with the upcoming MUSE instrument at the ESO-VLT. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).Based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA), and the Canadian Astronomy Data Centre (CADC/NRC/CSA).

Emergence of Habitable Environments in Icy World Interiors

Science.gov (United States)

Neveu, Marc

2016-07-01

separation method that takes advantage of the density contrast between cells and sediment and preserves cellular elemental contents [11]. Using this method, I showed that in spite of the tremendous physical, chemical, and taxonomic diversity of Yellowstone hot springs, the composition of microorganisms there is surprisingly ordinary [12]. This suggests the existence of a stoichiometric envelope common to all life as we know it. Thus, future planetary investigations could use elemental fingerprints to assess the astrobiological potential of hydrothermal settings beyond Earth. References: [1] US National Research Council (2011)Vision & Voyages in the Decade 2013-2022. [2] Hussmann et al. (2006) Icarus 185, 258-273. [3] Desch et al. (2009) Icarus 202, 694-714. [4] Neveu et al. (2015) JGR 120, 123-154. [5] Neveu & Rhoden, in prep. [6] De Sanctis et al. (2015) Nature 528, 241-244. [7] Hsu et al. (2015) Nature 519, 207-210. [8] Wasson & Kallemeyn (1988) Phil Trans R Soc London A 325, 535-544. [9] Mumma & Charnley (2011) Annu Rev Astron Astrophys 49, 471. [10] Neveu et al., in revision. [11] Neveu et al. (2014) Limn Oceanogr 12, 519-529. [12] Neveu et al. (2016) Geobiology 14, 33-53.

On the Discovery of CO Nighttime Emissions on Titan by Cassini/VIMS: Derived Stratospheric Abundances and Geological Implications

Science.gov (United States)

Bainesa, Kevin H.; Drossart, Pierre; Lopez-Valverde, Miguel A.; Atreya, Sushil K.; Sotin, Christophe; Momary, Thomas W.; Brown, Robert H.; Buratti, Bonnie J.; Clark, Roger N.; Nicholson, Philip D.

2006-01-01

atmosphere and ionosphere. J. Geophys. Res. 109, E06002 Doi: 10.1029/2003JE002181]. This low CO/CH4 ratio is much lower than expected for the sub-nebular formation region of Titan and supports the hypothesis [e.g., Atreya et al., 2005. Methane on Titan: photochemical-meteorological-hydrogeochemical cycle. Bull. Am. Astron. Soc. 37, 735] that the conversion of primordial CO and other carbon-bearing materials into CH4-enriched clathrate-hydrates occurs within the deep interior of Titan via the release of hydrogen through the serpentinization process followed by Fischer-Tropsch catalysis. The time-averaged predicted emission rate of methane-rich surface materials is approximately 0.02 km(exp 3) yr (exp -1), a value significantly lower than the rate of silicate lava production for the Earth and Venus, but nonetheless indicative of significant geological processes reshaping the surface of Titan.

Formation and growth of embryos of the Earth-Moon system

Science.gov (United States)

Ipatov, Sergei I.

2016-07-01

radius of a considered embryo), and at the growth of the mass of the Earth's embryo by 10 times, the mass of the Moon's embryo increased by a factor of 1.43 and 1.31 at the ratio k_d of the density of the growing Moon to that of the growing Earth equal to its present value (k_d=0.6) and for equal densities (k_d=1), respectively. For the case of small relative velocities of planetesimals, effective radii of the embryos are proportional to r^2, and at the growth of the Earth's embryo mass by 10 times, the Moon's embryo mass increased by a factor of 1.051 and 1.044 at k_d=0.6 and k_d=1, respectively. [1] Galimov E.M., Krivtsov A.M.: Origin of the Moon. New concept. / De Gruyter. Berlin. 2012. 168 p. [2] Ipatov S.I.: Mon. Not. R. Astron. Soc., 2010, vol. 403, pp. 405-414.

The spectroscopic orbits and physical parameters of GG Carinae

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Marchiano, P.; Brandi, E.; Muratore, M. F.; Quiroga, C.; Ferrer, O. E.; García, L. G.

2012-04-01

GG Car, we obtain Teff = 23 000 K and log g = 3. The central star is surrounded by a spherical envelope consisting of a layer of 3.5 stellar radii composed of ionized gas and other outermost dust layers with EB - V = 0.39. These calculations are not strongly modified if we consider two similar B-type stars instead of a central star, provided our model suggests that the second star might contribute less than 10% of the primary flux. The calculated effective temperature is consistent with an spectral type B0-B2 and a distance to the object of 5 ± 1 kpc was determined. Based on observations taken at Complejo Astronómico EL LEONCITO, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.

Quantitative spectroscopy of Galactic BA-type supergiants. I. Atmospheric parameters

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Firnstein, M.; Przybilla, N.

2012-07-01

reference relations from the literature, the stars are significantly bluer than usually assumed, and bolometric corrections differ significantly from established literature values. Photometric Teff-determinations based on the reddening-free Q-index are found to be of limited use for studies of BA-type supergiants because of large errors of typically ±5% (1σ statistical) ±3% (1σ systematic), compared to a spectroscopically achieved precision of 1-2% (combined statistical and systematic uncertainty with our methodology). The reddening-free [c1] -index and β on the other hand are found to provide useful starting values for high-precision/accuracy analyses, with uncertainties of ±1% ± 2.5% in Teff, and ±0.04 ± 0.13 dex in log g (1σ-statistical, 1σ-systematic, respectively). Based on observations collected at the Centro Astronómico Hispano Alemán at Calar Alto (CAHA), operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC), proposals H2001-2.2-011 and H2005-2.2-016.Based on observations obtained at the European Southern Observatory, proposals 62.H-0176 and 079.B-0856(A). Additional data were adopted from the UVES Paranal Observatory Project (ESO DDT Program ID 266.D-5655).

Scientific and synergistic lessons learned from the Cassini-Huygens mission

Science.gov (United States)

Coustenis, Athena

exploration of Titan and the Saturnian System with TSSM, a mission studied jointly by ESA and NASA in 2008 and prioritized second for a launch around 2023-2025. References 1. Coustenis, A., Hirtzig, M., 2009. Cassini-Huygens results on Titan's surface. Research in Astronomy and Astrophysics 9, 249-268. 2. Coustenis et al., 2010, Titan trace gaseous composition from CIRS at the end of the Cassini-Huygens prime mission Icarus, in press. 3. Flasar, F. M., et al., 2005. Titan's atmospheric temperatures, winds, and composition. Science, 308, 975-978. 4. Fulchignoni, M., et al, 2005. In situ measurements of the physical characteristics of Titan's environment. Nature, 438, 785-791, doi:10.1038/nature04126. 5. Lebreton, J-P., Coustenis, A., et al., 2009. Results from the Huygens probe on Titan. Astron. & Astrophys. Rev. 17, 149-179. 6. Tomasko, M. G., et al., 2005. Rain, winds and haze during the Huygens probe's descent to Titan's surface. Nature, 438, 765-778, doi:10.1038/nature04126.

Aqueous processing of organic compounds in carbonaceous asteroids

Science.gov (United States)

Trigo-Rodríguez, Josep Maria; Rimola, Albert; Martins, Zita

2015-04-01

A (2002) Clay mineral-organic matter relationships in the early solar system. Meteorit Planet Sci 37:1829-1833. Rimola A, Costa D, Sodupe M, Lambert JF, Ugliengo P (2013) Silica surface features and their role in the adsorption of biomolecules: computational modeling and experiments. Chem Rev 113:4216-4313. Rimola A, Sodupe M, Ugliengo P (2007) Aluminosilicate as promoters for peptide bond formation: an assessment of Bernal's hypothesis by ab initio methods. J Am Chem soc 129:8333-8344 Trigo-Rodríguez JM, Moyano-Cambero CE, Llorca J, Formasier S, Barucci MA, Belskaya I, Martins Z, Rivkin AS, Dotto E, Madiedo JM, Alonso-Azcárate J (2014) UV to far-IR reflectance spectra of carbonaceous chondrites - I. Implications for remote characterization of dark primitive asteroids targeted by sample-return missions. Mon Not R Astron Soc 437:227-240. Trigo-Rodríguez JM, Alonso-Azcárate J, Abad MM, Lee MR (2015) Ultra high resolution Transmission Electron Microscopy of matrix mineral grains in CM chondrites: preaccretionary or parent body aqueous processing? LPI constribution, 46th LPSC, abstract #1198.

Comparison of Regression and Neural Networks Models to Estimate Solar Radiation Comparación de Regresión y Modelos de Redes Neuronales para Estimar la Radiación Solar

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Mónica Bocco

2010-09-01

ón multicapa, para estimar la radiación solar global diaria y comparar la eficiencia de los mismos en su aplicación para una región de la Provincia de Salta, Argentina. Se utilizaron datos de heliofanía relativa, temperaturas máxima y mínima, precipitación, precipitación binaria y radiación solar astronómica provistos por la Estación Experimental Salta, Instituto Nacional de Tecnología Agropecuaria (INTA, Argentina, correspondientes al período 1996-2002. Tanto para los modelos de redes neuronales como para las regresiones lineales se consideraron tres alternativas de combinaciones de los parámetros meteorológicos, obteniéndose buenos resultados con ambas metodologías de predicción, con valores de la raíz del error cuadrático medio variando desde 1.99 a 1.66 MJ m-2 d-1 y coeficientes de correlación de 0.88 a 0.92. Se concluye que ambos, los modelos de redes neuronales y las regresiones lineales, pueden ser usados para predecir en forma adecuada la radiación solar global diaria; si bien las redes neuronales produjeron mejores resultados.

On the universal stellar law

Science.gov (United States)

Krot, Alexander

stars. In this connection, comparison with estimations of temperatures using of the regression dependences for multi-planet extrasolar systems [8] testifies the obtained results entirely. References 1. Krot, A.M.:2009, A statistical approach to investigate the formation of the solar system. Chaos, Solitons and Fractals41(3), 1481-1500. 2. Krot, A.M.:2012, A models of forming planets and distribution of planetary distances and orbits in the solar system based on the statistical theory of spheroidal bodies. In:Solar System: Structure, Formation and Exploration, ch.9 (Ed. by Matteo de Rossi). New York, Nova Science Publishers, pp. 201-264. - ISBN: 978-1-62100-057-0. 3. Krot, A. M.:2012, A statistical theory of formation of gravitating cosmogonicbodies. Minsk,Bel. Navuka, 4. 448 p. - ISBN 978-985-08-1442-5 [monograph in Russian]. 5. Eddington, A.S.: 1916,On the radiative equilibrium of the stars.Mon. Not. Roy. Astron. Soc.84 (7), 525-528. 6. Jeans, J.: 1929, Astronomy and cosmogony. Cambridge, University Press. 7. Chandrasekhar, S.:1939, An introduction to the study of stellar structure.Cambridge, University Press. 8. Pintr, P., Peřinová, V., Lukš, A., Pathak, A.:2013, Statistical and regression analyses of detected extrasolar systems. Planetary and Space Science, 75(1), 37-45.

Mal tiempo, tiempo maligno, tiempo de subversión ritual. La temposensitividad agrofestiva invernal

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Del Campo Tejedor, Alberto

2006-06-01

Full Text Available In the light of a number of festive, ritual, poetico-musical and literary expresions, from Andalusia and elsewhere, the author discusses time as lived by agrarian cultures: a syncretic time, resulting from the superposition of civico-political, religious and peasant calendars; a cyclic time, given the effects of astronomico-meteorological time on nature and the subsequent cultural response on both the instrumental dimension (the work in the fields and the expresive dimension (the rituals and the festivals; and, finally, an ages-old bipolar time, experienced as the succession of two alternating seasons —wintertime and summertime—which also underlies a dichotomous agrofestive time-sensitiveness analyzed here under the following hypothesis: during the months of «good weather,» especially May and June, the rituals have a propitiatory and positively extolling sense; they mimetically dramatize the union between earth, vegetation, animals and humans by means of prototypes and archetypes that symbolically recreate the natural order of things. By contrast, the wintertime rituals and festivals—from 1st November till Carnival, and particularly around Christmas—all have in common a grotesque character and a sense of inverted order, symbolically signifying, with a logic at once serio-comic and ambiguous, the dark side of existence, while ritually conjuring up the fears of bad weather, of fateful and pernicious time, the time of cold nights, hunger and death.

A la luz de algunas expresiones festivas, rituales, poético-musicales y literarias, de Andalucía y otros contextos, el artículo aborda el tiempo vivido por las culturas agroganaderas: un tiempo sincrético, como consecuencia de la superposición de los calendarios civil-político, religioso y campesino; un tiempo cíclico, fruto de la incidencia del tiempo astronómico-meteorológico en la naturaleza y la consiguiente respuesta cultural en el plano instrumental (los trabajos agr

Obituary -- Salvador González Bedolla

Science.gov (United States)

Peña, H. José

1997-04-01

It is with great sadness that I must communicate the passing of our colleague Salvador Félix González Bedolla. The observational astronomers of the Observatorio Astronómico Nacional owe much to his pioneering effort at San Pedro Mártir, work that formed him as an astronomer, and helped him become one of the best photometric observers in México and, at the Instituto de Astronomóa of the UNAM, the academic technician with the highest productivity of articles derived from observations at the OAN. Salvador was an excellent student. He obtained the highest achievement award (Gabino Barreda) in high school, studied physics at the Universidad Nacional Autónoma de México (UNAM) and also finished the credits for his Master's degree in Physics with only his thesis separating him from his degree, an act which was constantly put off until his death. He began his career in Astronomy in 1973 under Dr. Eugenio Mendoza. Later he worked with Josef Warman in the observation of short period stars in the Observatorio `José Arbol y Bonilla'' in Zacatecas, México. I then began working continuously with him in this field of research which, thanks to his great work capacity, produced very good results. He continued in these fields of research not only within the Institute of Astronomy, but also in other research facilities, especially two: With the variable group from the Observatory at Nice, France, beginning in 1985, specializing in the pulsation of early stars. His main interest was in the β Cep stars and in the possibility of relating these stars to the new types of variables (such as the OB stars, the `53 Per' variables, the `ultrashort' period and the ``slow'' and Be variables) discovered near this zone. Hence, in view of this, his efforts were aimed at monitoring the stars that belong to these new groups in order to discover if they are really different from the classical β Cep stars. Moreover, beginning in 1984, Salvador began working with a group of astronomers from

The Earth's Interaction With the Sun Over the Millennia From Analyses of Historical Sunspot, Auroral and Climate Records

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Yau, K.

2001-12-01

A prolonged decrease in the Sun's irradiance during the Maunder Minimum has been proposed as a cause of the Little Ice Age ({ca} 1600-1800). Eddy [{Science} {192}, 1976, 1189] made this suggestion after noting that very few sunspots were observed from 1645 to 1715, indicative of a weakened Sun. Pre-telescopic Oriental sunspot records go back over 2200 years. Periods when no sunspots were seen have been documented by, {eg}, Clark [{Astron} {7}, 2/1979, 50]. Abundances of C 14 in tree rings and Be10 in ice cores are also good indicators of past solar activity. These isotopes are produced by cosmic rays high in the atmosphere. When the Sun is less active more of them are made and deposited at ground level. There is thus a strong {negative} correlation between their abundances and sunspot counts. Minima of solar activity in tree rings and a south polar ice core have been collated by, {eg}, Bard [{Earth Planet Sci Lett} {150} 1997, 453]; and show striking correspondence with periods when no sunspots were seen, centered at {ca} 900, 1050, 1500, 1700. Pang and Yau [{Eos} {79}, #45, 1998, F149] investigated the Medieval Minimum at 700, using in addition the frequency of auroral sighting7s, a good indicator of solar activity too [Yau, PhD thesis, 1988]; and found that the progression of minima in solar activity goes back to 700. Auroral frequency, C 14 and Be 10 concentrations are also affected by variations in the geomagnetic field. Deposition changes can also influence C 14 and Be 10 abundances. Sunspot counts are thus the only true indicator of solar activity. The Sun's bolometric variations (-0.3% for the Maunder Minimum) can contribute to climatic changes (\\0.5° C for the Little Ice Age)[{eg}, Lean, {GRL} {22}, 1995, 3195]. For times with no thermometer data, temperature can be estimated from, {eg}, Oxygen 18 isotopic abundance in ice cores, which in turn depends on the temperature of the ocean water it evaporated from. We have linked the Medieval Minimum to the cold

Magnetic Properties of Three Impact Structures in Canada

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Scott, R. G.; Pilkington, M.; Tanczyk, E. I.; Grieve, R. A. F.

1995-09-01

. The Clearwater Lakes impact structures are two complex craters formed in Archean retrograde granulite facies rocks [4]. Clearwater West, at 36 km diameter, has an annular ring of islands and a shallowly submerged central uplift. Clearwater East, at 26 km diameter, has a more deeply submerged central uplift. The structures are characterised by highly oxidized melt rock and melt- breccia lenses exposed at the surface. Shocked crystalline basement rocks and minor amounts of breccia and melt rock occur in the central uplifts [5]. Despite relatively little alteration at depth, these rocks exhibit both susceptibilities and remanent magnetizations well below the regionally high values. The Clearwater rocks also contain a thermoremanent reversed magnetization, acquired at the time of impact, and characteristic of the Permo-Carboniferous Reversed Polarity Superchron. The magnetization is carried by titanomagnetite in Clearwater West, and both magnetite and pyrrhotite in Clearwater East. This reversed magnetization contributes to the magnetic low, but cannot account for all of it. The intense airborne magnetic low (> 500 nT) requires a significant contribution from the shocked basement at depth, produced by either alteration of magnetic phases along fractures, or reduction in magnetic properties by lower shock levels away from the point of impact [6]. References: [1] Pilkington M. and Grieve R. A. F. (1992) Rev. Geophys., 30, 161-181. [2] Innes M. J. S. et al. (1964) Publ. Dom. Obs. Ottawa, 31, 19-52. [3] Halliday I. and Griffin A. A. (1967) J. Roy. Astron. Soc. Can., 61, 1-8. [4] Simonds C. H. et al. (1978) LPS IX, 2633-2658. [5] Hische R. (1994) Unpublished Ph.D. thesis, Munster. [6] Pohl J. (1994) 3rd Intl. Wkshp., ESF Network Impact Cratering and Evol. of Planet Earth, Shockwave Behavior in Nature and Expt., Progr. Abstr., 51.

Direito à Educação no Brasil e dívida educacional: e se o povo cobrasse? Right to education in Brazil and the educational debt: what if the people actually demanded it?

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Alceu Ravanello Ferraro

2008-08-01

Full Text Available Inicia-se tratando do direito à Educação no quadro dos direitos fundamentais da pessoa humana e do conceito de dívida educacional que decorre da não-realização do direito público subjetivo de cada cidadão e cidadã à Educação Fundamental completa, conforme estabelecido na Constituição de 1988. Utilizando como parâmetro a informação censitária sobre o número de anos de estudo concluídos com aprovação levantados no Censo 2000, estima-se que, nesse ano, o Estado brasileiro devia, aos 119,6 milhões de pessoas de 15 anos ou mais, a astronômica cifra de 325,5 milhões de anos de estudo não realizados na idade própria - uma média de quase três anos por pessoa. São projetados também os investimentos necessários em termos de professores e salas de aula/turno-ano para o resgate da dívida. Mostra-se ainda que a dívida estimada com base na Pesquisa Nacional por Amostra de Domicílios 2005 (316,4 milhões de anos de estudo devidos representa uma diminuição muito pequena em relação ao Censo 2000. Por fim, aborda-se a questão dos atores ou agentes da efetividade do direito à Educação e dos instrumentos de exigibilidade que a legislação põe à disposição desses mesmos agentes. Conclui-se afirmando que está posto aí, para a sociedade em geral e para educadores e educadoras em particular, o grande desafio de despertar nas pessoas humildes a consciência de que elas efetivamente têm direito à Educação e de que dispõem de meios para cobrar do Estado esse direito.We start by considering the right to Education within the framework of the fundamental human rights, and the ensuing concept of educational debt, which follows from the failure to enforce the subjective public right of each citizen to a complete Fundamental Education as established by the 1988 Brazilian Constitution. Based on the 2000 census information on the number of years of schooling successfully concluded, we estimate that in that year the Brazilian

El lugar del Iṣlāḥ al-Maŷisṭī de Ŷābir b. Aflaḥ en la llamada «rebelión andalusí contra la astronomía ptolemaica»

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Bellver Martínez, José

2009-06-01

principal, IIṣlāḥ al-Maŷisṭī, traducida al latín y al hebreo. Con el IIṣlāḥ al-Maŷisṭī, su autor pretende reescribir el Almagesto a la vez que introduce algunas correcciones. En 1984, A.I. Sabra, en su importante artículo «The Andalusian revolt against Ptolemaic astronomy» llama la atención sobre un grupo de filósofo andalusíes, contemporáneos de Ŷābir b. Aflaḥ o que florecieron poco después que él —como Ibn Baŷŷa (m. 537/1138, Ibn Ṭufayl (m. 581/1185, Ibn Rušd (m. 595/1198, Maimónides (m. 601/1204 y al-Biṭrūŷī (fl. 596/1200—, quienes criticaron, desde un punto de vista cosmológico, los modelos astronómicos descritos en el Almagesto al no ser coherentes con la física aristotélica. La finalidad de este artículo es describir el tipo de críticas que hace Ŷābir b. Aflaḥ a Ptolomeo con el objeto de dilucidar si cabe considerarlo uno de los miembros de la rebelión andalusí contra la astronomía ptolemaica. La conclusión final es que las críticas de Ŷābir b. Aflaḥ no son de carácter cosmológico —si bien puedan tener consecuencias cosmológicas—, sino que son de carácter matemático y técnico. Así pues, no cabe considerarlo un miembro de la rebelión andalusí contra la astronomía ptolemaica.

Nuclear planetology: understanding habitable planets as Galactic bulge stellar remnants (black dwarfs) in a Hertzsprung-Russell (HR) diagram

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Roller, Goetz

2016-04-01

model constraining the evolution of a rocky planet like Earth or Mercury from a stellar precursor of the oldest population to a Fe-C BLD, shifting through different spectral classes in a HR diagram after massive decompression and tremendous energy losses. In the light of WD/BLD cosmochronology [1], solar system bodies like Earth, Mercury and Moon are regarded as captured interlopers from the Galactic bulge, Earth and Moon possibly representing remnants of an old binary system. Such a preliminary scenario is supported by similar ages obtained from WD's for the Galactic halo [1] and, independently, by means of 187Re-232Th-238U nuclear geochronometry [2, 4, 5], together with recent observations extremely metal-poor stars from the cosmic dawn in the bulge of the Milky Way [6]. This might be further elucidated in the near future by Th/U cosmochronometry based upon a nuclear production ratio Th/U = 0.96 [5] and additionally by means of a newly developed nucleogeochronometric age dating method for stellar spectroscopy, which will be presented in a forthcoming paper. The model shall stimulate geochemical data interpretation from a different perspective to constrain the (thermal) evolution of a habitable planet as to its geo-, bio-, hydro- and atmosphere. [1] Fontaine et al. (2001), Public. Astron. Soc. of the Pacific 113, 409-435. [2] Roller (2015), Abstract T34B-0407, AGU Spring Meeting 2015. [3] Arevalo et al. (2010), Chem. Geol. 271, 70-85. [4] Roller (2015), Geophys. Res. Abstr. 17, EGU2015-2399. [5] Roller (2015), 78th Annu. Meeting Met. Soc., Abstract #5041. [6] Howes et al. (2015), Nature 527, 484-487.

A Cocoon Found Inside the Black Widow's Web

Science.gov (United States)

2003-02-01

NASA's Chandra X-ray Observatory image of the mysterious "Black Widow" pulsar reveals the first direct evidence of an elongated cocoon of high-energy particles. This discovery shows that this billion-year-old rejuvenated pulsar is an extremely efficient generator of a high-speed flow of matter and antimatter particles. Known officially as pulsar B1957+20, the Black Widow received its nickname because it is emitting intense high-energy radiation that is destroying its companion through evaporation. B1957+20, which completes one rotation every 1.6-thousandths of a second, belongs to a class of extremely rapidly rotating neutron stars called millisecond pulsars. The motion of B1957+20 through the galaxy -- at a high speed of almost a million kilometers per hour -- creates a bow shock wave visible to optical telescopes. The Chandra observation shows what cannot be seen in visible light: a second shock wave. This secondary shock wave is created from pressure that sweeps the wind back from the pulsar to form the cocoon of high-energy particles, visible for the first time in the Chandra data. "This is the first detection of a double-shock structure around a pulsar," said Benjamin Stappers, of the Dutch Organization for Research in Astronomy (ASTRON), lead author on a paper describing the research that will appear in the Feb. 28, 2003, issue of Science magazine. "It should enable astronomers to test theories of the dynamics of pulsar winds and their interaction with their environment." B1957+20 X-ray-only image of B1957+20 Scientists believe millisecond pulsars are very old neutron stars that have been spun up by accreting material from their companions. The steady push of the infalling matter on the neutron star spins it up in much the same way as pushing on a merry-go-round makes it rotate faster. The result is an object about 1.5 times as massive as the Sun and ten miles in diameter that rotates hundreds of times per second. The advanced age, very rapid rotation rate

Vesta and low gravity impact mixing

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Hoffmann, Martin; Nathues, Andreas; Vincent, Jean-Baptiste; Sierks, Holger

2013-04-01

impacts into granular material lead to anything but a simple crater morphology. Unusual scaling laws (Uehara et al. 2003) and much more diverse phase patterns than in ordinary solid media have to be taken into account, if a consistent interpretation of the formation of a crater in very deep regolith is attempted (e.g. Opsomer et al. 2011). Additional effects are due to the low gravity environment on a small planetary body like Vesta (Tancredi et al. 2012). On Vesta many apparent counterparts to the results of the experiments can be found, as demonstrated by some examples. On a global scale, the multitude of small, unresolved primary and secondary impacts into the granular regolith contributes to the observed maturity on Vesta even after short time scales. References Cook, M. A., Mortensen, K. S. 1967. Impact cratering in granular materials. J. Appl. Phys. 38, 5125-5128. Daniels, K. E., Coppock, J. E., Behringer, R. P. 2004. Dynamics of meteor impacts. Chaos 14, 84. Daraio, C., Nesterenko, V. F., Herbold, E. B., Jin S. 2006. Energy trapping and shock desintegration in a composite granular medium. Phys. Rev. Lett. 96, 058002, 1-4. Opsomer, E., Ludewig, F., Vandewalle, N. 2011. Phase transitions in vibrated granular systems in microgravity. Phys. Rev. E84, 051306, 1-5. Rivas, N., Ponce, S., Gellet, B., Risso, D., Soto, R., Cordero, P. 2011. Sudden chain energy transfer events in vibrated granular media. Phys. Rev. Lett. 106, 088001, 1-4. Tancredi, G., Maciel, A., Heredia, L., Richeri, P., Nesmachnow, S. 2012. Granular physics in low-gravity environments using discrete element method. Monthly Not. Royal Astron. Soc. 420, 3368-3380. Uehara, J. S., Ambroso, M. A., Ojha, R. J., Durian, D. J. 2003. Low-speed impact craters in loose granular media. Phys. Rev. Lett. 90, 194301, 1-4.

Mixed-Methods Study that Examines Nine Science Teachers' Perceptions of Slooh Robotic Telescope for Teaching Astronomy. (Breton Title: Métodos Mistos de Estudo que Examinam a Percepção de Nove Professores de Ciências sobre o Telescópio Robótico Slooh Para Ensino de Astronomia.) Métodos Mixtos de Estudio que Examinan la Percepcion de Nueve Profesores de Ciencias sobre EL Telescopio Robótico Slooh Para la Enseñanza de la Astronomía

Science.gov (United States)

Gershun, Daniel C.; Slater, Timothy F.; Berryhill, Katie J.

2014-07-01

ção em sala de aula", "Impacto no Instrutor" e "Questões logísticas". A análise desses temas sugere que Slooh pode proporcionar um ambiente de aprendizagem interativo e social com capacidade de incorporar temas interdisciplinares. Aunque estudios previos muostraron que los telescopios robóticos tienen el potencial de mejorar el aprendizaje del estudiante, hay relativamente poca investigación centrada en las percepciones de lós profesores respecto de esta tecnología. Este estudio investiga: "¿cuál es el mérito académico de la utilización de telescopios robóticos SLOOH para enseñar astronomía según la percepción de los profesores de ciências?" Nuestra muestra está formada por nueve profesores de ciencias de estudiantes entre 13 a 18 años pre-y post-tests, entrevistas, y. encuestas se recogieron durante dos semanas de un curso on-line de verano sobre los telescopios robóticos. Si bien lós tests antes y después de las pruebas no revelaron un aumento estadísticamente significativo en el conocimiento de contenido astronómico, el análisis de lós datos cualitativos reveló cinco temas que describen los aspectos más importantes de la utilización de SLOOH de acuerdo con los participantes:. "Imágenes", "Interface", "aplicación en el aula", "Impacto en el Instructor" y "problemas logísticos" . El análisis de estos temas sugiere que SLOOH puede proporcionar un ambiente de aprendizaje interactivo y social, con capacidad para incorporar temas transversales.

A New Clue in the Mystery of Fast Radio Bursts

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Kohler, Susanna

2017-06-01

The origin of the mysterious fast radio bursts has eluded us for more than a decade. With the help of a particularly cooperative burst, however, scientists may finally be homing in on the answer to this puzzle.A Burst RepeatsThe host of FRB 121102 is placed in context in this Gemini image. [Gemini Observatory/AURA/NSF/NRC]More than 20 fast radio bursts rare and highly energetic millisecond-duration radio pulses have been observed since the first was discovered in 2007. FRB 121102, however, is unique in its behavior: its the only one of these bursts to repeat. The many flashes observed from FRB 121102 allowed us for the first time to follow up on the burst and hunt for its location.Earlier this year, this work led to the announcement that FRB 121102s host galaxy has been identified: a dwarf galaxy located at a redshift of z = 0.193 (roughly 3 billion light-years away). Now a team of scientists led by Cees Bassa (ASTRON, the Netherlands Institute for Radio Astronomy) has performed additional follow-up to learn more about this host and what might be causing the mysterious flashes.Hubble observation of the host galaxy. The object at the bottom right is a reference star. The blue ellipse marks the extended diffuse emission of the galaxy, the red circle marks the centroid of the star-forming knot, and the white cross denotes the location of FRB 121102 ad the associated persistent radio source. [Adapted from Bassa et al. 2017]Host ObservationsBassa and collaborators used the Hubble Space Telescope, the Spitzer Space Telecsope, and the Gemini North telecsope in Hawaii to obtain optical, near-infrared, and mid-infrared observations of FRB 121102s host galaxy.The authors determined that the galaxy is a dim, irregular, low-metallicity dwarf galaxy. Its resolved, revealing a bright star-forming region roughly 4,000 light-years across in the galaxys outskirts. Intriguingly, the persistent radio source associated with FRB 121102 falls directly within that star-forming knot

Brennand: resonancia y universalidad de las formas Brennand: resonance and the univesality of the forms

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G. CECILIA TORO

2001-03-01

Full Text Available Este trabajo propone la búsqueda y exposición de patrones de formas, tanto de algunas obras producidas por la naturaleza como de algunas de las obras producidas por la mano del hombre, quien como un microcosmos, que forma parte de la naturaleza recrea el macrocosmos. En una cultura en que el hombre ha perdido contacto con la naturaleza, con sus semejantes y con sus orígenes, otro objetivo de este trabajo es re emparentar al hombre con la naturaleza de la que forma parte. Se pretende mostrar al hombre, como un fractal del Universo, que es capaz de recrear, independientemente del tiempo, del espacio y de la escala de magnitudes, las mismas formas que crea el Universo, con la fuerza de la belleza en toda su pureza y en todo lo terrible con que a veces se nos presenta su aspecto. La belleza, así como la religión o como la pureza, tiene un poder redentor y el hombre anhela los paraísos perdidos. Cuando se amplia nuestra capacidad para percibir la belleza ya estamos en camino cierto, ya estamos en un camino que nos cambia desde un estado de conciencia a otro, ya estamos en un camino de regreso a la unidad. En el presente estudio se exponen algunas formas durante la diferenciación de un platelminto, Mesocestoides corti, obtenidas mediante microscopía de barrido y se exponen algunas obras de un hombre, Francisco Brennand, ganador del premio Gabriela Mistral 1993, el mayor premio dado en artes plásticas en América. Brennand, como un holograma, con un único referencial: el Universo ha recreado un Universo biológico y de increíble belleza desde su interior. En este trabajo, se pretende además exponer como, a través de la historia de nuestra cultura, el hombre justificó el anhelo y la certeza de universalidad, generando explicaciones filosóficas, psicológicas, biológicas, físicas, matemáticas, astronómicas y artísticasThis work proposes for the search and exposition of patterns of forms as they appear in nature as well as those

Nuclear planetology: understanding planetary mantle and crust formation in the light of nuclear and particle physics

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Roller, Goetz

2017-04-01

conceptual model constraining the evolution of a rocky planet like Earth or Mercury from a stellar precursor of the oldest population to a Fe-C BLD, shifting through different spectral classes in a HR diagram after massive decompression and tremendous energy losses. In the light of WD/BLD cosmochronology [1], solar system bodies like Earth, Mercury and Moon are regarded as captured interlopers from the Galactic bulge, Earth and Moon possibly representing remnants of an old binary system. Such a preliminary scenario is supported by similar ages obtained from WD's for the Galactic halo [1] and, independently, by means of 187Re-232Th-238U nuclear geochronometry [3, 4], together with recent observations extremely metal-poor stars from the cosmic dawn in the bulge of the Milky Way [8]. This might be further elucidated in the near future by Th/U cosmochronometry based upon a nuclear production ratio Th/U = 0.96 [9] and additionally by means of a newly developed nucleogeochronometric age dating method for stellar spectroscopy [9-11]. The model shall stimulate geochemical data interpretation from a different perspective, to constrain the evolution and differentiation of planetary or lunar crusts and mantles in general. [1] Fontaine et al. (2001), Public. Astron. Soc. of the Pacific 113, 409-435. [2] Roller (2015), Abstract T34B-0407, AGU Spring Meeting 2015. [3] Roller (2016), Goldschmidt Conf. Abstr. 26, 2642. [4] Roller (2015), Goldschmidt Conf. Abstr. 25, 2672. [5] Roller (2015), Geophys. Res. Abstr. 18, EGU2016-33. [6] Arevalo et al. (2010), Chem. Geol. 271, 70-85. [7] Roller (2015), Geophys. Res. Abstr. 17, EGU2015-2399. [8] Howes et al. (2015), Nature 527, 484-487. [9] Roller (2016), JPS Conf. Proc., Nuclei in the Cosmos (NIC XIV), Niigata, Japan, subm. (NICXIV-001); NICXIV Abstr. #1570244284. [10] Roller (2016), JPS Conf. Proc., Nuclei in the Cosmos (NIC XIV), Niigata, Japan, subm. (NICXIV-002); NICXIV Abstr. #1570244285. [11] Roller (2016), JPS Conf. Proc., Nuclei in the

Efectos difusivos en la formación de enanas blancas de Helio de baja masa en sistemas binarios cerrados

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De Vito, M. A.; Benvenuto, O. G.

In the last years, and thanks to advances in observational techniques, many astronomers have discovered in a great number of binary radio-pulsars the presence of a helium white dwarf resulting from a previous evolutionary state in which the progenitor of this star experienced one or more episodes of mass transfer to the compact component in the pair. That is the case for PSR B1855+09 (van Kerkwijk, M. H., Bell, J. F, Kaspi, V. M., & Kulkarni, S. R. 2000, ApJ 530, L37), where the mass for the white dwarf is known accurately from measurements of the Shapiro delay of the pulsar signal, MWD = 0.258+0.028-0.016 M⊙; for PSR J02018 + 4232 (Bassa, C. G., van Kerkwijk, M. H., & Kulkarni, S. R. 2003, A&A, 403, 1067), the spectra confirm that the companion is a helium-core white dwarf of ≈ 0.2 M⊙. On the other hand, there are several authors (Ferraro, F., Possenti, A., Sabbi, E., & D'Amico, N. 2003, ApJ, 596, L211; Bassa et al. 2003) that have identified the optical binary companion to the BMSP PSR J1911 - 5958A, located in the halo of the Galactic globular cluster NGC 6752, like a blue star whose position in the color-magnitude diagram is consistent with the cooling sequence of a low-mass, ≈ 0.17 - 0.20 M⊙, low metallicity helium white dwarf at the cluster distance. Finally, the color and magnitude of the stellar companion for B 1620-26 indicate that is a white dwarf of 0.34 ± 0.04 M⊙ (Sigurdson, S., Richer, H. B., Hansen, B. M., Stairs, I. H. & Thorset, S. E. 2003, Science, 301, 193S). This has motivated us to study the formation of low mass helium white dwarfs in the context of binary evolution. For that purpose, using the code of binary evolution, entirely developed in the Facultad de Ciencias Astronómicas y Geofísicas of the Universidad Nacional de La Plata, Argentina, we have investigated the effects of diffusive processes on the evolution of a star member of a close binary system. A similar study was performed for Althaus, L. G., Serenelli, A. M

Inhomogeneous molecular ring around the B[e] supergiant LHA 120-S 73

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Kraus, M.; Cidale, L. S.; Arias, M. L.; Maravelias, G.; Nickeler, D. H.; Torres, A. F.; Borges Fernandes, M.; Aret, A.; Curé, M.; Vallverdú, R.; Barbá, R. H.

2016-10-01

line profile is strongly variable in both width and shape and resembles of those seen in non-radially pulsating stars. A proper determination of the real underlying stellar rotation velocity is hence not possible. Conclusions: The existence of multiple stable and clumpy rings of alternating density recalls ring structures around planets. Although there is currently insufficient observational evidence, it is tempting to propose a scenario with one (or more) minor bodies or planets revolving around LHA 120-S 73 and stabilizing the ring system, in analogy to the shepherd moons in planetary systems. Based on observations: (1) with the 1.52-m and 2.2-m telescopes at the European Southern Observatory (La Silla, Chile), under the programme 076.D-0609(A) and under the agreement with the Observatório Nacional-MCT (Brazil); (2) at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), under the programmes GS-2004B-Q-54, GS-2010B-Q-31, and GS-2012B-Q-90; (3) at Complejo Astronómico El Leoncito operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan (Visiting Astronomer: A.F.T.); and (4) with the du Pont Telescope at Las Campanas Observatory, Chile, under the programme CNTAC 2008-02 (Visiting Astronomer: R.B. and A.F.T.).Presented spectroscopic data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http

ASPECTOS RELEVANTES DA APROXIMAÇÃO ENTRE BRASIL E CHINA: UMA ABORDAGEM ANALÍTICA [doi: 10.5329/RECADM.20050401009

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Silvio Aparecido Crepaldi

2005-05-01

Full Text Available Normal 0 21 false false false PT-BR X-NONE X-NONE MicrosoftInternetExplorer4 RESUMO Nos últimos anos, cresceu notavelmente o interesse mútuo entre o Brasil e a China. Na década de 1990 ambos os países se esforçaram para promover a multi-polarização do poder mundial e fortalecer a cooperação entre países em desenvolvimento. Brasil e China trabalham com vistas à consolidação de uma parceria estratégica, o que tem impulsionado as relações bilaterais; mas há ainda desafios a serem superados. Com esta realidade surge uma lacuna na bibliografia sobre os aspectos relevantes da aproximação Brasil e China. Assim, a carência de bibliografias voltadas ao assunto que incluam o estudo desta aproximação e seus reflexos, motiva à pesquisa visando sanar essas deficiências. Pretende-se analisar as relações comerciais sino-brasileiras de 1984 a 2002 e explorar o significado do conceito de parceria estratégica no relacionamento dos dois países. Antes disso, contudo, são indispensáveis algumas ponderações extraídas da sua análise global, permitindo a melhor reflexão e apontamento de conclusões sobre as relevantes matérias tratadas na referida aproximação Brasil e China. Em conseqüência do cenário exposto, a problemática pode ser sintetizada na seguinte questão: "como Brasil e China deveriam interagir entre si para obter uma inserção mutuamente vantajosa no mundo globalizado?". As informações referentes ao tema aproximação entre Brasil e China foram obtidas mediante pesquisa bibliográfica. O volume das transações comerciais entre Brasil e China vem evoluindo rapidamente e a China tornou-se recentemente o maior parceiro comercial do Brasil na Ásia. Há ainda enormes potencialidades comerciais a serem exploradas. Ao mesmo tempo, a economia chinesa consegue gerar empregos urbanos em escala astronômica. Somente nos primeiros 9 (nove meses deste ano, foram criados cerca de 8 milhões de postos de trabalho nas cidades

El boto y los geoglifos de Nasca: una contribución de la investigación estética en la arqueología

Directory of Open Access Journals (Sweden)

1974-01-01

rito con la forma plástica del mismo y que se enlazan en un misterioso pero igualmente elocuente propósito. El arte como excedente de energías encuentra la posibilidad de llevar a cabo mediante este residuo de 'energía cultural', la forma que el mito exige para su significado. Esta manifestación no necesariamente ha de ser plástica puede ejercerse con otras formas de arte, bailes, cantos o lances deportivos, de competencia (al igual que el 'agón' griego que también pueden incluirse en este caso como expresión estética, en espacios rigurosamente señalados y consagrados en cumplimiento de esos ritos. Estos son los fundamentos de juicio crítico-estético que apoyan la tesis del autor La astrología (o religiosidad, puesto que hay armonía entre el astro solar y la existencia humana conjuga con el arte y desarrolla su actividad en los múltiples y complejos trazos-rectilíneos juntamente con oíros dibujos totémicos entrelazados y relacionados con estos trazos, algunos largos de kilómetros. Hace una memoria de su señalamiento y analiza el 'Informe Hawkins' como el más reciente y científico paso de investigación y que determina una fecha para la ejecución de estos trazos entre los años 390 a 500 de la era cristiana. Hawkins declara que estos trazos 'no parecen tener significado astronómico' por lo mismo cabe inclinarse hacia la hipótesis lúdicra del autor de este ensayo, como expresiones sociales en las que interviene un determinado sentido de juego, del deporte religioso. Entre los muchos glifos totémicos figura lo del cetáceo Boto (Orea gladiator que aparece ya en la cerámica del primer período cultural, el 'naturalista', que florece en los tiempos del sub-estilo 'nasca' de Lumbreras (100-300 d.C.. Comenta la posibilidad de errores en su trazo y señala el ejemplo como prueba de un rito que no es de una simple gratificación estética. Y deduce, de acuerdo con opiniones autorizadas, el desarrollo socio-político del 'genio' nasquense hasta su

The Orbital Distribution of Earth-crossing Asteroids and Meteoroids

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Benoit, P. H.; Sears, D. W. G.

1993-07-01

meteorites have different orbital distributions [8]. References: [1] Steel D. I. et al. (1991) Mon. R. Astron. Soc., 251, 632-648. [2] Wolf S. F. and Lipschutz M. E. (1992) Meteoritics, 27, 308. [3] Benoit P. H. et al. (1991) Icarus, 94, 311-325. [4] Benoit P. H. and Sears D. W. G. (1993) LPS XXIV, 95- 96. [5] Wetherill G. W. and ReVelle D. O. (1981) Icarus, 48, 308- 328. [6] Williams J. G. (1975) JGR, 80, 2914-2916. [7] Galibina I. V. and Terent'eva A. K. (1987) Solar Sys. Res., 21, 160-166. [8] Graf Th. and Marti K. (1991) LPS XXII, 473-474.

On the roto-translatory internal motions of a three layer non-isobarycentric Earth model: a Lagrangian system approach

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Escapa, Alberto; Fukushima, Toshio

2010-05-01

simply a kinematical correction on the degenerate mode of a non-rotating model. Namely, the relative errors in the periods of the equatorial modes are reduced from 11.69% to 3.79% and from -6.04% to -1.91%, respectively. Acknowledgement.- AE's contribution was carried out thanks to a sabbatical leave from the University of Alicante at the National Astronomical Observatory of Japan (NAOJ), supported by the Spanish Ministerio de Educación, project PR2009-0379, within the Programa Nacional de Movilidad de Recursos Humanos I-D+i 2008-2011. The generous hospitality of the NAOJ staff is gratefully acknowledged. References Busse, F.H., J. Geophys. Res. 79, 753, 1974 Getino, J. and Ferrándiz, J. M., Mon. Not. R. Astron. Soc. 322, 785, 2001 Moritz, H., Bull. Géod., 56, 364, 1982 Rieutord, M., Phys. Earth Planet. Int., 131, 269, 2002

A proposed contents astronomy for basic education

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Albrecht, E.; Voelzke, M. R.

2014-08-01

A Astronomia é um tema que sempre exerceu fascínio sobre as pessoas de um modo geral. Conhecer e estudar o que há nos “céus”, além de nossos olhos, continua sendo instigador e de grande interesse. Baseado nestas justificativas desenvolveu-se uma pesquisa de Doutorado, na qual, o objetivo principal foi investigar sobre a presença dos conteúdos de Astronomia nas Propostas Curriculares da região Sul do Brasil, a saber, os estados de Paraná, Rio Grande do Sul e Santa Catarina e, posterior comparação com os Parâmetros Curriculares Nacionais (PCN) que trazem propostas de conteúdos para toda a Educação Básica brasileira. Tal investigação pautou-se na abordagem de caráter qualitativo e utilizouse para tal da Análise de Conteúdos (Bardin, 2011), que possibilitou a construção de quatro categorias, nas quais os conteúdos astronômicos foram agrupados: Terra, Sistema Solar, Via Láctea e Universo. Após a leitura, coleta de dados, construção de categorias, observou-se a dicotomia na apresentação destes conteúdos. As propostas curriculares analisadas foram as de Geografia, Ciências e Física dos estados do Paraná (2008), Rio Grande do Sul (2009) e de Santa Catarina (1998), responsáveis pelo trabalho com Astronomia nestes estados. No Ensino Fundamental, a proposta curricular do estado do Paraná apresenta conteúdos ligados à Astronomia desde o sexto ano até o nono ano, como conteúdo do primeiro bimestre, o que também é apresentado na proposta curricular do estado do Rio Grande do Sul, porém, este, não divide os conteúdos por bimestre e nem por ano, mas por ciclos, sexto e sétimo anos como primeiro ciclo e oitavo e nono anos como segundo ciclo, deixando livre para o professor estruturar sua sequência de conteúdos. A proposta curricular de Santa Catarina não apresenta estes conteúdos de maneira explícita, não divide dos conteúdos nem por ano, nem por série, traz uma sequência de conteúdos para serem trabalhados ao longo dos

Chemical composition of the semi-volatile grains of comet 67P/Churyumov-Gerasimenko

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Wurz, Peter; Altwegg, Kathrin; Balsiger, Hans; Berthelier, Jean-Jacques; Bieler, André; Calmonte, Ursina; De Keyser, Johan; Fiethe, Björn; Fuselier, Stefan; Gasc, Sébastien; Gombosi, Tamas; Jäckel, Annette; Korth, Axel; Le Roy, Lena; Mall, Urs; Rème, Henri; Rubin, Martin; Tzou, Chia-Yu

2017-04-01

Neutral Analysis, Space Science Review 128 (2007), 745-801. K.-H Glassmeier, H. Boehnhardt, D. Koschny, E. Kührt, and I. Richter, The Rosetta Mission: Flying To-wards the Origin of the Solar System, Space Science Reviews 128 (2007), 1-21. S. Scherer, K. Altwegg, H. Balsiger, J. Fischer, A. Jäckel, A. Korth, M. Mildner, D. Piazza, H. Rème, and P. Wurz, A novel principle for an ion mirror design in time-of-flight mass spectrometry, Int. Jou. Mass Spectr. 251 (2006) 73-81. P. Wurz, M. Rubin, K. Altwegg, H. Balsiger, S. Gasc, A. Galli, A. Jäckel, L. Le Roy, U. Calmonte, C. Tzou, U.A. Mall, B. Fiethe, J. De Keyser, J.J. Berthelier, H. Rème, A. Bieler, V. Tenishev, T.I. Gombosi, and S.A. Fuselier, Solar Wind Sputtering of Dust on the Surface of 67P/Churyumov-Gerasimenko, Astron. Astrophys. 583, A22 (2015) 1-9, DOI: 10.1051/0004-6361/201525980.

A Look into the Hellish Cradles of Suns and Solar Systems

Science.gov (United States)

2009-09-01

Rose, T.L. Bourke, R.A. Gutermuth and S.J. Wolk (Harvard-Smithsonian Center for Astrophysics, Cambridge, USA), S.T. Megeath (Department of Physics and Astronomy, The University of Toledo, USA), J. Alves (Centro Astronómico Hispano Alemán, Almeria, Spain), and D. Nürnberger (ESO). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Book Reviews

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Peter Metcalf

1990-10-01

age in motion; Popular radicalism in Java, 1912-1926, Ithaca/London: Cornell University Press, 1990. xxiv + 365 pp. - Rob de Ridder, Willem F.H. Adelaar, Het boek van Huarochirí. Mythen en riten van het Oude Peru, Amsterdam: Meulenhoff, 1988, 150 pp., - Marie-Odette Scalliet, Peter Carey, A.A.J. Payen: Journal de mon voyage à Jogja Karta en 1825. The outbreak of the Java War (1825-30 as seen by a painter, Cahier d’Archipel 17, Paris 1988. XIV + 183 pp., 17 ill., 3 maps. - Matthew Schoffeleers, Marion Melk-Koch, Auf der Suche nach der menschlichen Gesellschaft: Richard Thurnwald, Berlin: Dietrich Reimer, 1989. 352 pp., maps, photographs and Thurnwald bibliography. - Matthew Schoffeleers, Peter Metcalf, Where are you / Spirits? Style and theme in Berawan prayer, Washington and London: Smithsonian Institution Press, 1989, 345 pp. - J.W. Schoorl, J.F.L.M. Cornelissen, Pater en Papoea; Ontmoeting van de Missionarissen van het Heileg Hart met de cultuur der Papoea’s van Nederlands Zuid-Nieuw-Guinea (1905-1963, Kampen: Kok, 1988, XIV + 256 pp. - Alex van Stipriaan, Jo Derkx, Suriname; A bibliography, 1980-1989, Leiden: KITLV (Royal Institute of Linguistics and Anthropology, Department of Caribbean studies, 1990, 297 pp., Irene Rolfes (eds. - A.A. Trouwborst, Th. Schweizer (Hg, Netzwerkanalyse; Ethnologische perspektiven, Berlin: Dietrich Reimerverlag, 1989, VIII, 229 pp. - Hans Vermeulen, Brian Juan O’Neill, Social inequality in a Portugese hamlet; Land, late marriage and bastardy, 1870-1978, Cambridge: Cambridge University Press. 431 pp. 1987. - C.W. Watson, Hendrick M.J. Maier, In the center of authority. The Malay Hikayat Merong Mahawangsa, Ithaca: Southeast Asia program, Studies on Southeast Asia , 1988. 210 pp. - Neil Lancelot Whitehead, Edmundo Magaña, Orión y la mujer Pléyades. Simbolismo astronómico de los indios kaliña de Surinam, Dordrecht/Providence: Foris, 1988. [CEDLA Latin American studies series 44.] 373 pp. - J.J. de Wolf, Meyer Fortes, Religion

Hot subdwarf stars in close-up view. I. Rotational properties of subdwarf B stars in close binary systems and nature of their unseen companions

Science.gov (United States)

Geier, S.; Heber, U.; Podsiadlowski, Ph.; Edelmann, H.; Napiwotzki, R.; Kupfer, T.; Müller, S.

2010-09-01

used in this work were obtained at the Hobby-Eberly Telescope (HET), which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen, for programmes number UT07-2-004 and UT07-3-005. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC). Some of the data presented here were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. Some of the data used in this work were obtained at the Palomar Observatory, owned and operated by the California Institute of Technology. Based on observations with the William Herschel Telescope operated by the Isaac Newton Group at the Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias on the island of La Palma, Spain.

Book Review:

Science.gov (United States)

Wainwright, John

2007-04-01

spatially homogeneous solution of Bianchi type I with pressure-free matter, the Lemaitre-Tolman solutions, the Szekeres solutions and the Kerr solution (the original derivation using the Kerr-Schild metric, and Carter's derivation using separability of the Klein-Gordon equation). Readers may wish to compare the above-mentioned derivation of the Bianchi type I solutions, which uses metric components and coordinates, with the derivation given in [3] (see section 5.3), using the orthonormal frame formalism. In summary, this book is an interesting and informative introduction to general relativity and cosmology. The unconventional choice of topics and emphasis may, however, lead some readers to conclude that it may be more suitable as a reference work than as the text for a course. References [1] Celerier M N 2000 Do we really see a cosmological constant in the supernovae data? Astron. Astrophys. 353 63 [2] Celerier M N and Schneider J 1998 A solution to the horizon problem: a delayed big bang singularity Phys. Lett. A 249 37 [3] Ellis G F R and van Elst H 1999 Cosmological models Theoretical and Observational Cosmology ed M Lachieze-Rey (Dordrecht: Kluwer) [4] Krasinski A 1997 Inhomogeneous Cosmological Models (Cambridge: Cambridge University Press) [5] Kurki-Suonio H and Liang E 1992 Relation of redshift surveys to matter distribution in spherically symmetric dust Universes Astrophys. J. 390 5

Ideas de Vida y Muerte en Culturas Orientales

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Adolfo de Francisco Zea

1994-12-01

Full Text Available

Señor Presidente: Es muy placentero para mí en la tarde de hoy entregar a la Academia por su digno conducto, el retrato del Dr. Luis Zea Uribe, mi abuelo, quien fuera miembro de la Corporación por largo tiempo y presidiera sus destinos de 1928 a 1930.y es especialmente significativo para mí por ser usted, mi compañero de estudios y amigo de siempre, quien ocupa hoy con lujo y distinción la Presidencia de la Academia.

Este retrato es copia del que fuera pintado por el célebre miniaturista y retratista bogotano Luis Felipe Uzcátegui hace varias décadas y hace justicia a las inmensas calidades de su espíritu: la frente amplia que traduce una inteligencia prodigiosamente lúcida, rápida y penetrante hasta lo maravilloso, como lo señalara Armando Solano en el prólogo del libro que recogió sus Producciones Escogidas.

Las líneas delgadas de su boca y el mentón recio del estudioso que además de adquirir amplios conocimientos médicos, incursionó con su microscopio monocular en el mundo de lo infinitamente pequeño y apreció con su telescopio el mundo de lo infinitamente grande, lo que lo condujo a ser miembro de la Sociedad Astronómica de Francia presidida en ese entonces por su amigo cercano Camilo Flammarion. Quizás fue el estudio de las maravillas del universo lo que lo llevó un paso adelante a investigar en el campo de los fenómenos espiritualistas que hoy caen dentro de la órbita de la psicología y la para psicología, para lo cual estaba admirablemente dotado. Allí adquirió la certeza absoluta de la existencia del más allá y de un Dios inefable pleno de bondad y ordenó su vida entera a adquirir el Conocimiento, a impregnar todos sus actos con un alto sentido de la ética y a buscar el perfeccionamiento personal en la existencia terrena, que en su sentir, habría de permitirle en sucesivas encarnaciones acercarse cada vez más a la perfección.

Sus experiencias en el campo espiritualista y sus

Most Efficient Spectrograph to Shoot the Southern Skies

Science.gov (United States)

2009-05-01

CNRS; in Italy the Osservatorio di Brera, Trieste, Palermo and Catania; and in the Netherlands, the University of Amsterdam, the University of Nijmegen and ASTRON. Beside the participating institutes and ESO, the project was supported by the National Agencies of Italy (INAF), the Italian Ministry for Education, University and Research (MIUR), the Netherlands (NOVA and NWO) and by the Carlsberg Foundation in Denmark. The project was also supported in Denmark and the Netherlands with funds from the EU Descartes prize, the highest European prize for science, awarded in 2002 to the European collaboration on gamma-ray burst research headed by Professor Ed van den Heuvel. ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in the Atacama Desert region of Chile: La Silla, Paranal and Chajnantor.

New Vistas Open with MIDI at the VLT Interferometer

Science.gov (United States)

2002-12-01

and at low temperatures (MPIA in Heidelberg, Germany), designing and manufacturing optics for the extreme cryogenic environment (ASTRON in Dwingeloo, The Netherlands), designing and creating the complex software needed to run the instrument in a user-friendly way (NEVEC in Leiden, The Netherlands, and MPIA), as well as other specialised contributions from the Kiepenheuer-Institut für Sonnenphysik in Freiburg (Germany), Observatoire de Paris-Meudon and Observatoire de la Côte d'Azur in Nice (France), and Thüringer Landessternwarte in Tautenburg (Germany). This wide collaboration was carried out in close cooperation with and profiting from the professional experience of ESO that has built and now operates the Paranal Observatory, ensuring the proper interfacing between MIDI and the VLTI needed for high-performance interferometric measurements. Brief history of the MIDI project Work on the mid-infraredinterferometric instrument MIDI started in 1997 when MPIA proposed to ESO to build such a facility that would conform with ESO's plans for interferometric observations with the VLT telescopes and which would most probably become the first of its kind worldwide. Soon thereafter, the Netherlands Science Organization NOVA with ASTRON and NEVEC and the other partner institutes in France, the Netherlands and Germany joined the project. With Christoph Leinert and Uwe Graser from MPIA teaming up to lead the project, more than two dozen engineers, astronomers and students worked intensively for three and a half years on the planning, design and production, before the integration of this highly complex instrument could start at the Max-Planck-Institut für Astronomie in Heidelberg. This took place in September 2001 and was followed by a period of extensive instrumental tests. Much preparatory work had to be done at Paranal in parallel, to be ready for a smooth installation of MIDI [3]. After a positive, concluding status review of MIDI by ESO in September 2002, the many parts of

The applications of Complexity Theory and Tsallis Non-extensive Statistics at Solar Plasma Dynamics

Science.gov (United States)

Pavlos, George

2015-04-01

-345. 8. A.V. Milovanov, Stochastic dynamics from the fractional Fokker-Planck-Kolmogorov equation: large-scale behavior of the turbulent transport coefficient, Phys. Rev. E 63 (2001) 047301. 9. G.P. Pavlos, et al., Universality of non-extensive Tsallis statistics and time series analysis: Theory and applications, Physica A 395 (2014) 58-95. 10. G.P. Pavlos, et al., Tsallis non-extensive statistics and solar wind plasma complexity, Physica A 422 (2015) 113-135. 11. A.A. Ruzmaikin, et al., Spectral properties of solar convection and diffusion, ApJ 471 (1996) 1022. 12. V.E. Tarasov, Review of some promising fractional physical models, Internat. J. Modern Phys. B 27 (9) (2013) 1330005. 13. C. Tsallis, Possible generalization of BG statistics, J. Stat. Phys. J 52 (1-2) (1988) 479-487. 14. C. Tsallis, Nonextensive statistical mechanics: construction and physical interpretation, in: G.M. Murray, C. Tsallis (Eds.), Nonextensive Entropy-Interdisciplinary Applications, Oxford Univ. Press, 2004, pp. 1-53. 15. C. Tsallis, Introduction to Non-Extensive Statistical Mechanics, Springer, 2009. 16. G.M. Zaslavsky, Chaos, fractional kinetics, and anomalous transport, Physics Reports 371 (2002) 461-580. 17. L.M. Zelenyi, A.V. Milovanov, Fractal properties of sunspots, Sov. Astron. Lett. 17 (6) (1991) 425. 18. L.M. Zelenyi, A.V. Milovanov, Fractal topology and strange kinetics: from percolation theory to problems in cosmic electrodynamics, Phys.-Usp. 47 (8), (2004) 749-788.

Astronomers Make First Images With Space Radio Telescope

Science.gov (United States)

1997-07-01

part of the VLBA instrument, was modified over the past four years to allow it to incorporate data from the satellite. Correlation of the observational data was completed successfully on June 12, after the exact timing of the satellite recording was established. Further computer processing produced an image of PKS 1519-273 -- the first image ever produced using a radio telescope in space. For Jim Ulvestad, the NRAO astronomer who made the first image, the success ended a long quest for this new capability. Ulvestad was involved in an experiment more than a decade ago in which a NASA communications satellite, TDRSS, was used to test the idea of doing radio astronomical imaging by combining data from space and ground radio telescopes. That experiment showed that an orbiting antenna could, in fact, work in conjunction with ground-based radio observatories, and paved the way for HALCA and a planned Russian radio astronomy satellite called RadioAstron. "This first image is an important technical milestone, and demonstrates the feasibility of a much more advanced mission, ARISE, currently being considered by NASA," Ulvestad said. The first image showed no structure in the object, even at the extremely fine level of detail achievable with HALCA; it is what astronomers call a "point source." This object also appears as a point source in all-ground-based observations. In addition, the 1986 TDRSS experiment observed the object, and, while this experiment did not produce an image, it indicated that PKS 1519-273 should be a point source. "This simple point image may not appear very impressive, but its beauty to us is that it shows our entire, complex system is functioning correctly. The system includes not only the orbiting and ground-based antennas, but also the orbit determination, tracking stations, the correlator, and the image-processing software," said Jonathan Romney, the NRAO astronomer who led the development of the VLBA correlator, and its enhancement to process data

S-N secular ocean tide: explanation of observably coastal velocities of increase of a global mean sea level and mean sea levels in northern and southern hemispheres and prediction of erroneous altimetry velocities

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Barkin, Yury

2010-05-01

levels have been obtained at set of simplifying assumptions concerning of a direction of drift of the centre of mass of the Earth and character of redistribution of atmospheric and oceanic masses and, naturally, in future will be specified. The work was accepted by grants of RFBR: N 07-05-00939. References [1] Barkin Yu.V. (1995) Motion of the Earth's center of mass induced by global changes in its dynamic structure and by tidal deformations. Mosc. Univ. Phys. Bull., 1995, 50(5), 92-94. English translation of Vestni. Mosk. Univ. 3, Fiz., Astron. (Russia). 1995, 50(5), 99-101. [2] Barkin Yu.V. (2009) About possible polar drifts of centers of mass of the Earth and Mars. Abstract Book (CD) of European Planetary Science Congress (Potsdam, Germany, 13 - 18 September 2009), Vol.4, EPSC 2009-118. [3] Zotov L.V., Barkin Yu.V., Lubushin A.A. (2008) Geocenter motion and its geodynamical contenst. 'Space Geodynamics and Modeling of the Global Geodynamic Processes'. International scientific conference in the frames of the 'Asian-Pacific Space Geodynamics' Project (APSG 2008). (22-26 September 2008, Novosibirsk, Russian Federation). Abstract book. P. 28 [4] Barkin Yu.V. (2008) Secular polar drift of the core in present epoch: geodynamical and geophysical consequences and confirmations. General and regional problems of tectonics and geodynamics. Materials of XLI Tectonic Conference. V. 1. -M.:GEOS. p. 55-59. In Russian. [5] Barkin Yu.V. (2005) Oscillations of the Earth core, new oceanic tides and dynamical consequences. Materials of XI International Scientific Conference 'Structure, geodynamics and mineral genetic processes in lithosphere' (September, 20-22 2005, Syktyvkar, Russia). Publisher of Geology Institute of Komi SC of Ural Section of RAS, Syktyvkar, pp. 26-28. In Russian. [6] Barkin Yu.V. (2009) An explanation of secular variations of a gravity at stations Ny-Alesund, Medicine, Churchill and Syowa. Materials of the International Conference: «Yu.P. Bulashevich's fifth

SINFONI Opens with Upbeat Chords

Science.gov (United States)

2004-08-01

Dutch Institutes and ESO who have worked on the development of SINFONI for nearly 7 years. The work on SINFONI at Paranal included successful commissioning in June 2004 of the Adaptive Optics Module built by ESO, during which exceptional test images were obtained of the main-belt asteroid (22) Kalliope and its moon. Moreover, the ability was demonstrated to correct the atmospheric turbulence by means of even very faint "guide" objects (magnitude 17.5), crucial for the observation of astronomical objects in many parts of the sky. SPIFFI - SPectrometer for Infrared Faint Field Imaging - was developed at the Max Planck Institute for Extraterrestrische Physik (MPE) in Garching (Germany), in a collaboration with the Nederlandse Onderzoekschool Voor Astronomie (NOVA) in Leiden and the Netherlands Foundation for Research in Astronomy (ASTRON), and ESO. PR Photo 24a/04: SINFONI Adaptive Optics Module at VLT Yepun (June 2004) PR Photo 24b/04: SINFONI at VLT Yepun, now fully assembled (July 2004) PR Photo 24c/04: "First Light" image from the SINFONI Adaptive Optics Module PR Photo 24d/04: AO-corrected Image of a 17.5-magnitude Star PR Photo 24e/04: SINFONI undergoing Balancing and Flexure Tests at VLT Yepun PR Photo 24f/04: SINFONI "First Light" Spectrum of HD 130163 PR Photo 24g/04: Members of the SINFONI Adaptive Optics Module Commissioning Team PR Photo 24h/04: Members of the SPIFFI Commissioning Team PR Photo 24i/04: The Principle of Integral Field Spectroscopy (IFS) PR Photo 24j/04: The Orbital Motion of Linus around (22) Kalliope PR Photo 24k/04: SINFONI Observations of the Galactic Centre Region PR Photo 24l/04: SINFONI Observations of the Circinus Galaxy PR Photo 24m/04: SINFONI Observations of the AGN Galaxy NGC 7469 PR Photo 24n/04: SINFONI Observations of NGC 6240 PR Photo 24o/04: SINFONI Observations of the Young Starforming Galaxies BX 404/405 PR Video Clip 07/04: The Orbital Motion of Linus around (22) Kalliope SINFONI: A powerful and complex instrument ESO PR Photo

Lyapunov analysis: from dynamical systems theory to applications

Science.gov (United States)

Cencini, Massimo; Ginelli, Francesco

2013-06-01

structures playing a prominent role in the studies, both theoretical and applied, of transport, stirring and mixing properties in fluid flows. This section contains two contributions, one more theoretical in nature and a second with biological applications, where Lagrangian coherent structures and their effect on transport and mixing are analyzed through finite-size Lyapunov exponents. While this special issue, in its very nature, cannot be fully exhaustive, we hope that it will provide a clear and up-to-date picture of the theory and applications of Lyapunov analysis, further stimulating fruitful debate across a number of related research fields. Acknowledgments We would like to acknowledge the Journal of Physics A editorial staff, in particular A Haywood, R Gillan and E O'Callaghan for their continuous assistance which made this special issue possible. References [1] Lorenz E 1993 The Essence of Chaos (Seattle, WA: University of Washington) [2] Poincaré H 1890 Acta Math. 13 1 [3] Poincaré H 1892 Les méthods nouvelles de la mécanique céleste vol 1 (Paris: Gauthier-Villars) Poincaré H 1893 Les méthods nouvelles de la mécanique céleste vol 2 (Paris: Gauthier-Villars) Poincaré H 1899 Les méthods nouvelles de la mécanique céleste vol 3 (Paris: Gauthier-Villars) Poincaré H 1992 New Methods of Celestial Mechanics (New York: American Institute of Physics) (Engl. transl.) [4] Hadamard J 1898 J. Math. Pures Appl. 4 27 [5] van der Pol B 1927 Phil. Mag. 3 65 [6] Fermi E, Pasta J and Ulam S 1955 Studies of nonlinear problems Technical Report LA-1940 (Los Alamos, NM: Los Alamos Scientific Laboratory) [7] Lorenz E N 1963 J. Atmos. Sci. 20 130 [8] Hénon M and Heiles C 1964 Astron. J. 69 73 [9] Kolmogorov A N 1958 Dokl. Akad. Nauk SSSR 119 861 [10] Kolmogorov A 1959 Dokl. Akad. Nauk SSSR 124 754 [11] Chirikov B 1959 At. Energ. 6 630 [12] Smale S 1967 Bull. Am. Math. Soc. 73 747 [13] Ruelle D and Takens F 1971 Commun. Math. Phys. 20 167 [14] Li T Y and Yorke J A 1975 Am. Math

Feeling the Heat

Science.gov (United States)

2004-05-01

, shown in ESO PR Photo 16d/04. The technical details are similar to ESO PR Photo 16g/04. The total integration time was 120 sec. The photos above resulted from some of the first observational tests with VISIR. PR Photo 16c/04 shows the scientific "First Light" image, obtained one day later on April 30th, of a visually obscured star forming region nearly 10,000 light-years away in our galaxy, the Milky Way. The picture shown here is a false-colour image made by combining three digital images of the intensity of the infrared emission from this region at wavelengths of 11.3 μm (one of the Polycyclic Aromatic Hydrocarbon - PAH - features), 12.8 μm (an emission line of ionised neon) and 19 μm (cool dust emission). Ten times sharper Until now, an elegant way to avoid the problems caused by the emission and absorption of the atmosphere was to fly infrared telescopes on satellites as was done in the highly successful IRAS and ISO missions and currently the Spitzer observatory. For both technical and cost reasons, however, such telescopes have so far been limited to only 60-85 cm in diameter. While very sensitive therefore, the spatial resolution (sharpness) delivered by these telescopes is 10 times worse than that of the 8.2-m diameter VLT telescopes. They have also not been equipped with the very high spectral resolution capability, a feature of the VISIR instrument, which is thus expected to remain the instrument of choice for a wide range of studies for many years to come despite the competition from space. More information A corresponding [1]: The consortium of institutes responsible for building the VISIR instrument under contract to ESO comprises the CEA/DSM/DAPNIA, Saclay, France - led by the Principal Investigator (PI), Pierre-Olivier Lagage and the Netherlands Foundation for Research in Astronomy/ASTRON - (Dwingeloo, The Netherlands) with Jan-Willem Pel from Groningen University as Co-PI for the spectrometer. [2]: Stellar radiation on its way to the observer is also

Programa de Pós-Graduação em Geologia - Teses Defendidas 1998 - Doutorado - Instituto de Geociências - Universidade Federal do Rio de Janeiro

Directory of Open Access Journals (Sweden)

1998-01-01

distância, no Morro da Fome. No estado do Rio de Janeiro, temos o sítio arqueológico de Itaboraí, no município do mesmo nome. O sítio está inserido em uma rampa de colúvio situada nos bordos da Bacia Calcária de São José de Itaboraí. 123 Anuário do Instituto de Geociências - UFRJ Volume 21 / 1998 A partir da década de 70 foram utilizados os métodos da relação silte-argila, ferro (Fe livre - ferro (Fe cristalizado, estratigráfico, tipológico e o da correlação geomorfológica (manchas climáticas. O método tipológico revelou uma cadeia tecnológica na confecção dos artefatos cobrindo as técnicas usadas em outras partes do mundo, indo do Pleistoceno Inferior ao Superior, reforçando os resultados obtidos pelos outros métodos relativos. O método absoluto do C14 foi usado à superfície do sítio. Apresentaram-se, também, as vantagens do estudo das manchas climáticas sobre os artefatos para avaliação cronológica. Finalmente, procurou-se através da apresentação dos três casos acima expostos, evidenciar a contribuição do arqueólogo aos estudos do Quaternário. Quanto às pinturas rupestres, sublinhou-se sua validade na interpretação paleoambiental a partir de representações pictóricas de animais pleistocênicos, especialmente em canhões. Utilizou-se o método etnológico-etnográfico para o reconhecimento - a partir de pinturas sobre rochas - de antigas migrações, tomando-se por base mitos, planos cosmológicos, uso de alucinógenos, etc., próprios do grupo lingüístico Tukâno. Essas conclusões foram reforçadas por registros históricos e por estudos no campo da Paleontologia Humana. Finalmente, apresentaram-se dois casos em que o homem préhistórico utilizou extensamente rochas para deixar registrado seu conhecimento astronômico e sua maneira particular de tentar uma integração com o cosmos. Nome: Claudia Guterres Vilela Título: Foraminíferos Quaternários da Plataforma Continental Norte Brasileira e do Leque do