Search results for "UNESCO::ASTRONOMÍA Y ASTROFÍSICA"
showing 10 items of 135 documents
The INTEGRAL IBIS/ISGRI System Point Spread Function and Source Location Accuracy
2003
The imager on board INTEGRAL (IBIS) presently provides the most detailed sky images ever obtained at energies above 30 keV. The telescope is based on a coded aperture imaging system which allows to obtain sky images in a large field of view 29deg x 29deg with an angular resolution of 12'. The System Point Spread Function of the telescope and its detailed characteristics are here described along with the specific analysis algorithms used to derive the accurate point-like source locations. The derived location accuracy is studied using the first in-flight calibration data on strong sources for the IBIS/ISGRI system. The dependence of the calibrated location accuracy with the signal to noise r…
Tomography of the SN 1987A ejecta and AGN core-shifts with high-precision astrometry
2017
Esta tesis trata dos temas muy distintos: (1) el estudio de las estructuras y movimientos propios de los chorros de los núcleos activos de galaxias (AGN) que componen la muestra S5 del casquete polar, por medio de astrometría global de alta precisión con la técnica de interferometría de muy larga base (VLBI); y (2) la reconstrucción tomográfica (i.e., 3D) de la emisión molecular de la parte interna de la supernova SN 1987A y su comparación con modelos de explosión de supernovas. En la primera parte, presentamos el análisis astrométrico diferencial llevado a cabo para todas las fuentes de la muestra S5 del casquete polar. Se consigue aplicar por primera vez a 43 GHz la técnica de astrometría…
Axisymmetric simulations of magnetorotational core collapse: approximate inclusion of general relativistic effects
2006
We continue our investigations of the magnetorotational collapse of stellar cores discussing simulations performed with a modified Newtonian gravitational potential that mimics general relativistic effects. The approximate TOV potential used in our simulations catches several features of fully relativistic simulations quite well. It is able to correctly reproduce the behavior of models which show a qualitative change both of the dynamics and the gravitational wave signal when switching from Newtonian to fully relativistic simulations. If this is not the case, the Newtonian and the approximate TOV models differ quantitatively. The collapse proceeds to higher densities with the approximate TO…
JEM–X science analysis software
2003
The science analysis of the data from JEM-X on INTEGRAL is performed through a number of levels including corrections, good time selection, imaging and source finding, spectrum and light-curve extraction. These levels consist of individual executables and the running of the complete analysis is controlled by a script where parameters for detailed settings are introduced. The end products are FITS files with a format compatible with standard analysis packages such as XSPEC. Martinez Nuñez, Silvia, Silvia.Martinez@uv.es
The kinematics of water masers in the stellar molecular outflow source, IRAS 19134+2131
2004
Using the Very Large Array (VLA) and the Very Long Baseline Array (VLBA), we have observed water maser emission in the proto-planetary nebula candidate IRAS 19134+2131, in which the water maser spectrum has two groups of emission features separated in radial velocity by ∼100 km s^−1. The blue-shifted and red-shifted clusters of maser features are clearly separated spatially by ∼150 mas, indicative of a fast collimated flow. However, not all of the maser features are aligned along the axis of the flow, as is seen in the similar high-velocity water maser source, W43A. Comparing the VLA and VLBA maps of the water maser source, we find 4 maser features that were active for 2 years. Using only V…
The REFLEX galaxy cluster survey VIII. Spectroscopic observations and optical atlas
2009
We present the final data from the spectroscopic survey of the ROSAT-ESO Flux-Limited X-ray (REFLEX) catalog of galaxy clusters. The REFLEX survey covers 4.24 steradians (34% of the entire sky) below a declination of 2.5 deg and at high Galactic latitude (|b| > 20 deg). The REFLEX catalog includes 447 entries with a median redshift of 0.08 and is better than 90% complete to a limiting flux fx = 3x10^{-12} erg s^{-1} cm^{-2} (0.1 to 2.4 keV), representing the largest statistically homogeneous sample of clusters drawn from the ROSAT All-Sky Survey (RASS) to date. Here we describe the details of the spectroscopic observations carried out at the ESO 1.5 m, 2.2 m, and 3.6 m telescopes, as wel…
Searches for cosmic neutrino sources with ANTARES, KM3NeT and IceCube and time calibration of ANTARES
2020
La astronomía con neutrinos de alta energía es una disciplina relativamente joven. Nació de la necesidad de extender la astronomía convencional más allá de los mensajeros electromagnéticos habituales para intentar responder la cuestión pendiente del origen de los rayos cósmicos de alta energía. Recientemente, el único telescopio de neutrinos del tamaño de un kilómetro cúbico actualmente en funcionamiento, IceCube, comunicó la primera observación significativa de un flujo difuso de neutrinos de alta energía de origen astrofísico junto con la primera asociación convincente de neutrinos astrofísicos con una fuente cósmica individual, abriendo una nueva era para la astronomía de neutrinos de al…
REM near-IR and optical multiband observations of PKS 2155-304 in 2005
2007
Spectral variability is the main tool for constraining emission models of BL Lac objects. By means of systematic observations of the BL Lac prototype PKS 2155-304 in the infrared-optical band, we explore variability on the scales of months, days and hours. We made our observations with the robotic 60 cm telescope REM located at La Silla, Chile. VRIJHK filters were used. PKS 2155-304 was observed from May to December 2005. The wavelength interval explored, the total number of photometric points and the short integration time render our photometry substantially superior to previous ones for this source. On the basis of the intensity and colour we distinguish three different states of the sour…
Improved Numerical Methods for Elliptic Problems in Astrophysics
2017
Les ePDEs (elliptic partial differential equations, en anglès) apareixen en una àmplia varietat d'àrees de les matemàtiques, la física i l'enginyeria. Són de particular interès en Astrofísica on apareixen, per exemple, quan es calcula el potencial gravitacional, en la solució de l'equació de Grad-Shafranov per magnetosferes lliures de forces, o d'imposar lligadures de divergència zero en la integració numèrica de les equacions MHD (magnetohydrodynamics, en anglès). En general, les ePDEs s'han de resoldre numèricament, establint una demanda cada vegada més gran d'algoritmes eficients i altament paral·lels per abordar la seua resolució computacional. El SRJ (scheduled relaxation Jacobi, en an…
Spectral classification & physical parameters of the IPHAS CBe stars in the BCD system.
2017
The INT Photometric Hα Survey (IPHAS) has detected tens of thousands of emission line objects in the Northern Galactic Plane. Spectroscopic follow-up has shown that the vast majority of them are Classical Be (CBe) stars, rapidly rotat- ing main sequence B type stars which develop an outflowing circumstellar disk by mechanisms not yet completely understood. In this work we present a study of the full catalogue of the CBe stars discovered by IPHAS. We have analyzed 805 low resolution spectra of 732 IPHAS CBe stars. With a semi-automatic proce- dure, which we evaluate at the first part of this work, we obtained the relevant physical parameters, including the effective temperature, surface grav…