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Nomenclatura Unesco > (21) Astronomía y Astrofísica

Mostrando recursos 121 - 140 de 548

121. METAL ABUNDANCES OF RED CLUMP STARS IN OPEN CLUSTERS: I. NGC 6819 1 - Angela Bragaglia; Eugenio Carretta; Raffaele G. Gratton; Monica Tosi; Pietro Bruno; Antonio Calì; Riccardo Claudi; Rosario Cosentino; Giancarlo Farisato; Mauro Rebeschini; Salvo Scuderi
Received; accepted – 2 – We present an analysis of high dispersion spectra (R ∼ 40, 000) of three red clump stars in the old open cluster NGC 6819. The spectra were obtained with SARG, the high dispersion spectrograph of the Telescopio Nazionale Galileo. The spectra were analyzed using both equivalent widths measured with an automatic procedure, and comparisons with synthetic spectra. NGC 6819 is found to be slightly metal-rich ([Fe/H]=+0.09 ± 0.03, internal error); there are no previous high resolution studies to compare with. Most element-to-element abundance ratios are close to solar; we find a slight excess of Si,...

122. Manuscript for Revista Mexicana de Astronomía y Astrofísica (2007) KINEMATICS OF THE NEBULAR COMPLEX MH9/10/11 ASSOCIATED WITH HOIX X-1 - P. Abolmasov; A. V. Moiseev
Favor de proporcionar un resumen en español. If you are unable to translate your abstract into Spanish, the editors will do it for you. We report the results of our observations of the nebular complex MH9/10/11, associated with the ULX HoIX X-1, with scanning Fabry-Pérot Interferometer. Two regions differing by their kinematics and line ratios may be distinguished, roughly corresponding to the bubble nebula MH9/10 and fainter HII-region MH11. For MH9/10 we find the expansion rate of 20 ÷ 70 km s −1 that is different for the approaching and receding parts. MH11 is characterised by very low velocity dispersion...

123. Manuscript for Revista Mexicana de Astronomía y Astrofísica (2007) QUANTITATIVE STELLAR SPECTRAL CLASSIFICATION. IV. APPLICATION TO THE OPEN CLUSTER IC 2391 - J. García; N. Sánchez; R. Velásquez
En este trabajo realizamos la primera prueba de un método de clasificación espectral estelar (Stock & Stock 1999), aplicándolo a estrellas tempranas. La muestra contiene estrellas miembros del cúmulo abierto IC 2391, para las cuales se dispone de espectros de alta resolución del Projecto UVES del Observatorio Paranal. Mostramos que, en general, las magnitudes absolutas MV y los colores intrínsecos (B − V)0 pueden ser recuperados dentro de los errores predichos por la calibración original ( ∼ 0, 4 para las magnitudes y ∼ 0, 03 para los colores). Este tipo de precisión nos permite estimar las distancias de estrellas...

124. Classical and recurrent nova models - José Pont, Jordi; Casanova Bustamante, Jordi; García-Berro Montilla, Enrique; Hernanz Carbó, Margarita; Shore, Steven N.; Calder, A.
Remarkable progress in the understanding of nova outbursts has been achieved through combined efforts in photometry, spectroscopy and numerical simulations. According to the thermonuclear runaway model, novae are powered by thermonuclear explosions in the hydrogen-rich envelopes transferred from a low-mass stellar companion onto a close white dwarf star. Extensive numerical simulations in 1-D have shown that the accreted envelopes attain peak temperatures ranging between 108 and 4 × 108 K, for about several hundred seconds, hence allowing extensive nuclear processing which eventually shows up in the form of nucleosynthetic fingerprints in the ejecta. Indeed, it has been claimed that novae can play...

125. Classical and recurrent nova models - José Pont, Jordi; Casanova Bustamante, Jordi; García-Berro Montilla, Enrique; Hernanz Carbó, Margarita; Shore, Steven N.; Calder, A.
Remarkable progress in the understanding of nova outbursts has been achievedthrough combined efforts in photometry, spectroscopy and numerical simulations. According to the thermonuclear runaway model, novae are powered by thermonuclear explosions in the hydrogen-rich envelopes transferred from a low-mass stellar companion onto a close white dwarfstar. Extensive numerical simulations in 1-D have shown that the accreted envelopes attain peak temperatures ranging between 108 and 4 × 108 K, for about several hundred seconds, hence allowing extensive nuclear processing which eventually shows up in the form of nucleosynthetic fingerprints in the ejecta. Indeed, it has been claimed that novae can play...

126. Espectroscopia de hidrocarburos aromáticos policíclicos en núcleos activos de galaxias y galaxias con actividad estelar - Ramos Padilla, Andrés Felipe; Higuera Garzón, Mario Armando
Ramos Padilla, Andrés Felipe and Higuera Garzón, Mario Armando (2012) Espectroscopia de hidrocarburos aromáticos policíclicos en núcleos activos de galaxias y galaxias con actividad estelar. In: Congreso Colombiano de Astronomía y Astrofísica, 5-8 de Noviembre 2012, Bucaramanga. (No publicado)

127. Gamma-ray spectrum of type Ia supernovae - Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Gómez, J; García Senz, Domingo; Jean, P
The explosion mechanism associated with thermonuclear supernovae (SNia) is still a matter of debate. In this paper we examine the 'f-ray emission of the radioactive debris predicted by the different theoretícal models and, using response estimations of the SPI and IBIS instruments aboard of INTEGRAL, we evaluate the capabilities of such instruments in the study of SNia. We also discuss preliminary results obtained with 3D models.

128. Gamma-ray spectrum of type Ia supernovae - Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Gómez, J; García Senz, Domingo; Jean, P
The explosion mechanism associated with thermonuclear supernovae (SNia) isstill a matter of debate. In this paper we examine the 'f-ray emission of the radioactive debris predicted by the different theoretícal models and, using response estimations of the SPI and IBISinstruments aboard of INTEGRAL, we evaluate the capabilities of such instruments in the study of SNia. We also discuss preliminary results obtained with 3D models.

129. Exploding stars: the gamma-ray signature of type Ia supernovae - Isern Vilaboy, Jordi; Gomez, J; Bravo Guil, Eduardo
Type Ia supenovae are commonly thought to be the outcome of the thermonuclear explosion of a white dwarf in a binary system. Nevertheless, there is no agreement on the scenarios (double degenerates, symbiotics stars ...) able to produce such events nor on the mechanisms responsible of such explosions (central ignition of a carbon-oxygen mixture, off-center detonation of He...). In this paper we review the present status of the problem and we show, in the context of a CO central ignition, how γ-ray astronomy can provide useful constraints to the theoretical models.

130. A new kind of type I supernovae? - Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Domínguez, I
In this paper we examine the consequences of the propagation of a slow deflagration front through a C-0 white dwarf that leads to the formation of a marginally bound remnant. This situation corresponds to the transition between the Delayed Detonation models and the Pulsating Delayed Detonation ones. The radioactive decay of the freshly formed 56Ni not only powers the light curve but also produces an ablative front that finally disrupts the star. The light curve is characterized by its low luminosity {-16.8 m)-as compared with a normal SNia- and its broad peak (~ 100 days).

131. SIXE (Spanish Italian X-ray Experiment): a summary of the phase-A study - Giovannelli, F; Bravo Guil, Eduardo; García-Berro Montilla, Enrique
In this paper we present a summary of the SIXE (Spanish Italian X-ray Experiment) for which we successfully finished the Phase-A study under financial support of the Spanish PNIE (Plan Nacional de Investigación Espacial).

132. Exploding stars: the gamma-ray signature of type Ia supernovae - Isern Vilaboy, Jordi; Gomez, J; Bravo Guil, Eduardo
Type Ia supenovae are commonly thought to be the outcome of the thermonuclear explosion of a white dwarf in a binary system. Nevertheless, there is no agreement on the scenarios (double degenerates, symbiotics stars ...) able to produce such events nor on the mechanisms responsibleof such explosions (central ignition of a carbon-oxygen mixture, off-center detonation of He...). In this paper we review the present status of the problem and we show, in the context of a CO central ignition, how γ-ray astronomy can provide useful constraints to the theoretical models.

133. A new kind of type I supernovae? - Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Domínguez, I
In this paper we examine the consequences of the propagation of a slow deflagration front through a C-0 white dwarf that leads to the formation of a marginally bound remnant. This situation corresponds to the transition between the Delayed Detonation models and the Pulsating Delayed Detonation ones. The radioactive decay of the freshly formed 56Ni not only powers the light curve but also produces an ablative front that finally disrupts the star. The light curve is characterized by its low luminosity {-16.8 m)-as compared with a normal SNia- and its broad peak (~ 100 days).

134. SIXE (Spanish Italian X-ray Experiment): a summary of the phase-A study - Giovannelli, F; Bravo Guil, Eduardo; García-Berro Montilla, Enrique
In this paper we present a summary of the SIXE (Spanish Italian X-ray Experiment) for which we successfully finished the Phase-A study under financial support of the Spanish PNIE (Plan Nacional de Investigación Espacial).

135. SIXE (Spanish Italian X-ray Experiment): a Payload for the Spanish MINISAT-02 Satellites - Bravo Guil, Eduardo; García-Berro Montilla, Enrique; José Pont, Jordi; Giovannelli, F
SIXE (Spanish Italian X-ray Experiment) is an X-ray payload with geometric area of ~3200cm2 , formed by four identical gas-filled Multiwire Proportional Counters devoted for a long term spectroscopy of selected X-ray sources in the energy range ~3-60 KeV. The spectral resolution of ~5% for E>35 KeV and ΔE/E=60/E1/2 for E<35 KeV, the continuum sensitivity (3ơ in 105 s) of ~3•10-6ph/cm2 •KeV, the line detection sensitivity (3ơ in 105 s) of ~3.5•10-6ph /cm2 •KeV, the time accuracy of 0.1 ms, the experiment weight of ~90 Kg, the full dimensions including the electronic box of ~660x660x400 mm3, the power budget of...

136. Laue lens simulation for gamma radiation in the energy range of 1 MeV - Perengüez Lopez, James
[ANGLÈS] The study of difraction applied to Laue lenses is a very promising tool in the field of astrophysics of gamma radiation. In the present work we carried out a theoretical study and a computational simulation of a Laue lens that works in the energy range of 1 MeV. First of all, we selected a geometry consisting of a concentric ring structure made of mosaic crystals; the materials used were germanium (Ge), copper (Cu) and silver (Ag). We considered two focal lengths of 10 m and 30 m. Some important parameters such as the arrangement of rings, the crystallographic planes...

137. High-temperature combustion: Approaching equilibrium using nuclear networks - Cabezón Gómez, Rubén Martín; García Senz, Domingo; Bravo Guil, Eduardo

138. SIXE (Spanish Italian X-ray Experiment): a Payload for the Spanish MINISAT-02 Satellites - Bravo Guil, Eduardo; García-Berro Montilla, Enrique; José Pont, Jordi; Giovannelli, F
SIXE (Spanish Italian X-ray Experiment) is an X-ray payload with geometric area of ~3200 cm2 , formed by four identical gas-filled Multiwire Proportional Counters devoted for a long term spectroscopy of selected X-ray sources in the energy range ~3-60 KeV. The spectral resolution of ~5% for E>35 KeV and ΔE/E=60/E1/2 for E<35 KeV, the continuum sensitivity (3ơ in 105 s) of ~3•10-6ph/cm2 •KeV, the line detection sensitivity (3ơ in 105 s) of ~3.5•10-6ph /cm2 •KeV, the time accuracy of 0.1 ms, the experiment weight of ~90 Kg, the full dimensions including the electronic box of ~660x660x400 mm3, the power budget of...

139. Production of intermediate-mass and heavy nuclei - Thielemann, F. K.; Frölich, Carla; Hirschi, R.; Liebendörfer, M.; Dillmann, I.; Mocelj, D.; Rauscher, t.; Martínez Pinedo, Gabriel; Langanke, K; Farouqi, K; Kratz, K.L.; Pfeiffer, B.; Panov, I.; Nadyozhin, D.K.; Blinnikov, S.; Bravo Guil, Eduardo; Hix, W.R.; Höflich, P.; Zinner, Ernst
Nucleosynthesis is the science related to all astrophysical processes which are responsible for the abundances of the elements and their isotopes in the universe. The astrophysical sites are the big bang and stellar objects. The working of nucleosynthesis processes is presented in a survey of events which act as abundance sources. For intermediate-mass and heavy elements, these are stellar evolution, type Ia and core collapse supernovae as well as hypernovae. We discuss successes and failures of existing processes and possible solutions via new (hitherto unknown) processes. Finally an analysis of their role is given in the puzzle to explain the...

140. Bounds on the possible evolution of the gravitational constant from cosmological type-Ia supernovae - Gaztañaga, E; García-Berro Montilla, Enrique; Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Domínguez, I
Recent high-redshift type-Ia supernovae results can be used to set new bounds on a possible variation of the gravitational constant G. If the local value of G at the space-time location of distant supernovae is different, it would change both the kinetic energy release and the amount of 56Ni synthesized in the supernova outburst. Both effects are related to a change in the Chandrasekhar mass MCh∝G-3/2. In addition, the integrated variation of G with time would also affect the cosmic evolution and therefore the luminosity distance relation. We show that the later effect in the magnitudes of type-Ia supernovae is...

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