Regular phantom black hole gravitational lensing

We study regular and asymptotically flat phantom black holes as gravitational lenses. We obtain the deflection angle in both the weak and the strong deflection limits, from which we calculate the positions, magnifications, and time delays of the images. We compare our results with those corresponding to the Schwarzschild solution and to the vacuum Brans-Dicke black hole.Comment: 14 pages, 4 figures; v2: improved and extended version, new references added. Accepted for publication in Phys. Rev.

Strong deflection lensing by charged black holes in scalar-tensor gravity

We examine a class of charged black holes in scalar-tensor gravity as gravitational lenses. We find the deflection angle in the strong deflection limit, from which we obtain the positions and the magnifications of the relativistic images. We compare our results with those corresponding to the Reissner-Norstrom spacetime and we analyze the observational aspects in the case of the Galactic supermassive black hole.Comment: 12 pages, 3 figures; v2: improved version, new references adde

Distribution of the 3.1 micron feature in Cepheus A

Near-IR absorption features produced by core-mantle dust grains are observed in many protostellar objects. The high spatial resolution observations (less or equal to 3 in.) could be helpful to monitor the expected changes of the features. Cep A/IRS 6 is a suitable candidate to carry out such a kind of study. It is located in an active star formation region and consists of a young object associated with an extended reflection nebula. The ice feature was observed in four positions of Cep A/IRS 6 with a 2.7 in. aperture. The observations were carried out at the IRTF using the cooled grating array spectrometer CGAS. The 2.4 to 3.8 micron spectra of two positions are presented

Shadow cast by rotating braneworld black holes with a cosmological constant

In this article, we study the shadow produced by rotating black holes with a tidal charge in a Randall-Sundrum braneworld model, with a  cosmological constant. We obtain the apparent shape and the  corresponding observables for different values of the tidal charge and the rotation parameter, and we analyze the influence of the presence of the cosmological constant. We also discuss the observational prospects for this optical effect.Fil: Eiroa, Ernesto Fabian. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Sendra, Carlos Maximiliano. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

High resolution molecular line observations of the Serpens Nebula

The Serpens Molecular cloud is a nearby low/intermediate mass star forming region that is in the final stages of forming a densely packed cluster of stars. Spectra and high angular resolution maps of the CO, 13CO, C18O and C17O J=2-1 and CO J=4-3 transitions were obtained to study the distribution of molecular gas near the cluster. These are supplemented with data on the J=4-3 HCO+ line (to probe the denser gas), and 3P1 - 3P0 line of atomic carbon. The mass of the region is estimated to be ~1450Msun, implying that the star formation efficiency in the region to date has been ~2.5percent. Several molecular outflows are visible in the maps; some are associated with compact objects visible in millimetre and submillimetre wave continuum maps, as well as more widespread diffuse high velocity gas that extends over much of the nebula. The mass and energy of material in the high velocity gas are relatively small, ~0.3Msun and 3 x 1045 erg s-1, consistent with the characteristics of outflows seen towards low mass star-formation regions. The directions of the overlapping outflow lobes do not however show a clear alignment with the cloud's large scale magnetic field as has been reported towards some other regions. The gas temperatures in the central part of the molecular cloud are warmer (~30-40K) than typical for dark clouds, suggesting that the Serpens cluster has interacted with, and heated this gas. Estimates of the CO isotopomeric abundance ratios from these data may be strongly affected by opacity and radiative transfer effects. In a comparison of the LTE and LVG techniques, the disagreement between the derived column densities is discussed - with particular relevance to the higher rotationa

Spectroscopic properties of stars with debris discs

The question of the origin and evolution of planetary systems is of fundamental importance for astrophysics. Dusty debris discs are signatures of planetary systems and, therefore, constitute valuable tools to provide new light in our understanding of how planetary systems form and evolve. We present the first results of a spectroscopic programme of a sample of stars with debris discs. High-resolution echelle spectra are used to determine metallicities and abundances. Properties of stars with debris discs, are compared with those of stars hosting planets, as well as 'normal' starsThis work was supported by the Spanish Ministerio de Ciencia e Innovación (MICINN), Plan Nacional de Astronomía y Astrofísica, under grant AYA2008-0172

A Herschel view of IC 1396 A: Unveiling the different sequences of star formation

The IC1396A globule in the young cluster Tr37, hosting many young stars and protostars, is assumed to be a site of triggered star formation. We mapped IC1396A with Herschel/PACS at 70 and 160 micron. The Herschel maps trace in great detail the very embedded protostellar objects and the structure of the cloud. PACS data reveal a previously unknown Class 0 object (IC1396A-PACS-1) located behind the ionization front. IC1396A-PACS-1 is not detectable with Spitzer, but shows marginal X-ray emission. The data also allowed to study three of the Class I intermediate-mass objects within the cloud. We derived approximate cloud temperatures to study the effect and potential interactions between the protostars and the cloud. The Class 0 object is associated with the densest and colder part of IC1396A. Heating in the cloud is dominated by the winds and radiation of the O6.5 star HD 206267 and, to a lesser extent, by the effects of the Herbig Ae star V 390 Cep. The surroundings of the Class I and Class II objects embedded in the cloud also appear warmer than the sourceless areas, although most of the low-mass objects cannot be individually extracted due to distance and beam dilution. The observations suggest that at least two episodes of star formation have occurred in IC1396A. One would have originated the known, ~1 Myr-old Class I and II objects in the cloud, and a new wave of star formation would have produced the Class 0 source at the tip of the brigth-rimmed cloud. From its location and properties, IC1396A-PACS-1 is consistent with triggering via radiative driven implosion (RDI) induced by HD 206267. The mechanisms behind the formation of the more evolved population of Class I/II/III objects in the cloud are uncertain. Heating of most of the remaining cloud by Class I/Class II objects and by HD 206267 itself may preclude further star formation in the region.Comment: Accepted by A&A, 9 pages, 5 figure

The Spanish model of New Journalism in a European context

This work deals with the study of the evolution and the historical experience of Spanish journalism in the context of decades of transition between the nineteenth and twentieth centuries. From the selection of the most relevant cases and the examination of tracking, or not, of models and European patterns of the reference press, singularities and analogies of the historical evolution of the Spanish journalism model may be seen - an evolutionary model fully registered within the framework of Western Europe and in one of its most fruitful phases: the origins and first development of the mass media. Therefore, the following trilogy of reference media is selected covering specified time periods: El Imparcial, Madrid, 1867-1933; La Vanguardia, Barcelona, 1881; and ABC, Madrid, 1903