Very-long-baseline radio interferometry surveys of the compact structure in active galactic nuclei.

Very-long-baseline radio interferometry (VLBI) imaging surveys have been undertaken since the late 1970s. The sample sizes were initially limited to a few tens of objects but the snapshot technique has now allowed samples containing almost 200 sources to be studied. The overwhelming majority of powerful compact sources are asymmetric corejects of one form or another, most of which exhibit apparent superluminal motion. However 5-10% of powerful flat-spectrum sources are 100-parsec (pc)-scale compact symmetric objects; these appear to form a continuum with the 1-kpc-scale double-lobed compact steep-spectrum sources, which make up 15-20% of lower frequency samples. It is likely that these sub-galactic-size symmetric sources are the precursors to the large-scale classical double sources. There is a surprising peak around 90 degrees in the histogram of misalignments between the dominant source axes on parsec and kiloparsec scales; this seems to be associated with sources exhibiting a high degree of relativistic beaming. VLBI snapshot surveys have great cosmological potential via measurements of both proper motion and angular size vs. redshift as well as searches for gravitational "millilensing."

Morphology of high-luminosity compact radio sources.

High-dynamic range imaging and monitoring with very-long-baseline interferometry reveal a rich morphology of luminous flat-spectrum radio sources. One-sided core-jet structures abound, and superluminal motion is frequently measured. In a few cases, both distinct moving features and diffuse underlying jet emission can be detected. Superluminal motion seen in such sources is typically complex, on curved trajectories or ridge lines, and with variable component velocities, including stationary features. The curved trajectories seen can be modeled by helical motion within the underlying jet flow. The very-long-baseline interferometry properties of the superluminal features in the jet of 3C 345 and other similar sources can be explained by models invoking the emission from shocks, at least within the vicinity of the compact core. Inverse-Compton calculations, constrained by x-ray observations, yield realistic estimates for the physical conditions in the parsec-scale jet. There is evidence for a transition region in this source beyond which other factors (e.g., plasma interactions and nonsynchrotron radiation processes) may become prominent. Multifrequency and polarization imaging (especially at high frequencies) are emerging as critical tools in testing model predictions.

Very-long-baseline radio interferometry observations of low power radio galaxies.

The parsec scale properties of low power radio galaxies are reviewed here, using the available data on 12 Fanaroff-Riley type I galaxies. The most frequent radio structure is an asymmetric parsec-scale morphology--i.e., core and one-sided jet. It is shared by 9 (possibly 10) of the 12 mapped radio galaxies. One (possibly 2) of the other galaxies has a two-sided jet emission. Two sources are known from published data to show a proper motion; we present here evidence for proper motion in two more galaxies. Therefore, in the present sample we have 4 radio galaxies with a measured proper motion. One of these has a very symmetric structure and therefore should be in the plane of the sky. The results discussed here are in agreement with the predictions of the unified scheme models. Moreover, the present data indicate that the parsec scale structure in low and high power radio galaxies is essentially the same.

Structure and evolution of the compact radio source in NGC 1275.

Investigations of the fine-scale structure in the compact nucleus of the radio source 3C 84 in NGC 1275 (New General Catalogue number) are reported. Structural monitoring observations beginning as early as 1976, and continuing to the present, revealed subluminal motions in a jet-like relatively diffuse region extending away from a flat-spectrum core. A counterjet feature was discovered in 1993, and very recent nearly simultaneous studies have detected the same feature at five frequencies ranging from 5 to 43 GHz. The counterjet exhibits a strong low-frequency cutoff, giving this region of the source an inverted spectrum. The observations are consistent with a physical model in which the cutoff arises from free-free absorption in a volume that surrounds the core but obscures only the counterjet feature. If such a model is confirmed, very-long-baseline radio interferometry observations can then be used to probe the accretion region, outside the radio jet, on parsec scales.

The nuclear jet and counterjet region of the radio galaxy Cygnus A.

Very-long-baseline interferometry images of the nuclear region of the radio galaxy Cygnus A reveal a pronounced "core" and a knotty jet and counterjet. The knots are moving away from the core at apparent speeds which are subluminal for h = 1 [h = H0/100 km.s-1.Mpc-1;1 parsec (pc) = 3.09 x 10(16)m] and about c for h = 0.5. The jet is aligned with the outer, kiloparsec-scale jet to within 2 degrees. The counterjet has a total flux density at 5 GHz of about one-fifth of that of the jet. In the context of the twin relativistic jet model for active galactic nuclei, the jet in Cygnus A is oriented at an angle to our line of sight of 35-80 degrees and 55-85 degrees, and the intrinsic velocity of the jet fluid is 0.4-0.6c and 0.6-1c for h = 1 and h = 0.5, respectively.

Very-long-baseline radio interferometry (VLBI) observations of gamma-ray blazars: results from millimeter-VLBI observations.

VLBI observations of the extremely gamma-bright blazar PKS 0528+134 at 8, 22, 43, and 86 GHz reveal a strongly bent one-sided-core jet structure with at least three moving and two apparently stationary jet components. At the highest observing frequencies the brightest and most compact jet component (the VLBI core) is unresolved with an upper limit to its size of approximately 50 microarcsec corresponding to approximately 0.2 parsec [H0 = 100 km.s-1.Mpc-1 (megaparsec-1), q0 = 0.5, where H0 is Hubble constant and q0 is the deceleration parameter]. Two 86-GHz VLBI observations performed in 1993.3 and 1994.0 reveal a new jet component emerging with superluminal speed from the core. Linear back-extrapolation of its motion yields strong evidence that the ejection of this component is related to an outburst in the millimeter regime and a preceding intense flare of the gamma-flux density observed in early 1993. This and the radio/optical "light curves" and VLBI data for two other sources (S5 0836+710 and 3C 454.3) suggest that the observed gamma-radiation might be Doppler-boosted and perhaps is closely related to the physical processes acting near the "base" of the highly relativistic jets observed in quasars.

Possible links between BL Lacertae objects and quasars from very long baseline interferometry radio data.

Systematic differences in the very long baseline interferometry (VLBI) radio polarization structure and average VLBI component speeds of BL Lacertae objects and quasars support the view that the observational distinction between these classes, based in large part on the strength of their optical line emission, is meaningful; in other words, this distinction reflects significant differences in the physical conditions in these sources. Possible models providing a link between the optical and VLBI properties of BL Lacertae objects and quasars are discussed. Most VLBI polarization observations to date have been global observations made at 6 cm; recent results suggest that the VLBI polarization structure of some sources may change dramatically on scales smaller than those probed by these 6-cm observations.

Evolution of powerful extragalactic radio sources.

Observations of complete flux density limited samples of powerful extragalactic radio sources by very-long-baseline interferometry enable us to study the evolution of these objects over the range of linear scales from 1 parsec to 15 kiloparsees (1 parsec = 3.09 x 10(18) cm). The observations are consistent with the unifying hypothesis that compact symmetric objects evolve into compact steep-spectrum doubles, which in turn evolve into large-scale Fanaroff-Riley class II objects. It is suggested that this is the primary evolutionary track of powerful extragalactic radio sources. In this case there must be significant luminosity evolution in these objects, but little velocity evolution, as they expand from 1 parsec to several hundred kiloparsecs in overall size.

La lectura de noticias de los informativos en la radio y la televisión: análisis de la prosodia y la emisión de la voz

Como enfoque global, se ha considerado que en la realización del lenguaje cooperan simultáneamente distintos órganos del cuerpo con sus correspondientes funciones; por tanto, el lenguaje es objeto de análisis desde diversas áreas científicas. Lo que nos ha inducido a abordar en nuestro trabajo algunos detalles significativos de distintos ámbitos de estudio. El objetivo principal ha sido analizar por qué la lectura de las noticias, en los medios audiovisuales, difieren ostensiblemente del lenguaje natural. Esa diferencia es percibida no sólo por la extraña entonación y segmentación errada de unidades fonológicas o sintácticas o por la acentuación impropia de palabras átonas, sino también por las diferentes características en los parámetros de la fonación. Para ello era preciso conocer los más importantes mecanismos del lenguaje espontáneo y, a partir de ese conocimiento, examinar qué elementos sufren alteración o desaparecen en el acto de la lectura con respecto al habla natural. La lectura es un acto en el que no intervienen los mecanismos biológicos innatos del ser humano, habitualmente presentes en el habla. En el habla, el pensamiento genera la palabra. Sin embargo, en la lectura, la palabra está ya escrita y por tanto no hay un proceso simultaneo con el pensamiento. Además, el mensaje que recibe el lector a través del grafismo y de los formatos en que se inscriben, constituye un elemento diferenciador del proceso natural. Los indicadores que recibe el lector son: elemento plano del papel y elemento lineal sin curvas de la escritura; formas que se transmiten instintivamente en la fonación. Y aunque en la lectura intervienen los órganos de fonación, no así otros muchos componentes de la movilidad corporal del habla como los brazos, las manos y los músculos del rostro, que son los que dirigen el sentido de la entonación y del ritmo...

Consumo de información deportiva en radio: el caso de Radio Marca

La información deportiva en las empresas informativas de radiodifusión comercial es uno de los pilares de la programación de las cadenas de radio generalistas de ámbito estatal. Y lo es por su nivel de audiencia y por la ocupación publicitaria de sus espacios. Genera una inversión que supone entre un quince y un veinte por ciento de los ingresos totales de estas empresas. El fenómeno de los grandes programas de información deportiva nocturna en España sigue contando con un alto grado de confianza por parte de una audiencia que, si bien ha mostrado una tendencia a la baja, no abandona a la radio durante las extensas jornadas de retransmisiones de las diferentes competiciones deportivas los fines de semana. Los programas que denominamos “Tipo Carrusel”, en efecto, centro de las parrillas los sábados y domingos, también ocupan horas los martes y los miércoles de competiciones de fútbol internacional. El consumo de información deportiva, sin embargo, no es patrimonio de las radios, sino también del resto de soportes: prensa y televisión. Y, sobre todo, desde los últimos años del siglo XX, de la red: Internet. Al calor de “Marca”, periódico especializado en información deportiva, nació en 2001 Radio Marca, cadena temática deportiva y objeto de análisis de este trabajo de investigación. El contexto favorable ya en el año 2001 para poner en marcha un proyecto que se inició con una concesión de Radio Digital, los acuerdos societarios con otros grupos para implementar la cadena y el plan de negocio del medio son parte de este estudio. Esta investigación aborda la empresa informativa, la programación, las audiencias, la inversión publicitaria, la información periodística especializada y el nuevo modelo de sistema informativo y de consumo que proporcionan las nuevas tecnologías. La permanencia, desde el año 2001, de Radio Marca en el mercado de la radio permite analizar su trayectoria, su nivel de penetración, la evolución de su red, y el grado de aceptación entre los oyentes a través de las mediciones de audiencia. Eso permite, asimismo, analizar la inversión y la rentabilidad. Radio Marca ha significado un cambio en el consumo de información: las mañanas y las tardes ya no son exclusiva de los contenidos políticos, económicos o musicales. Merece especial estudio el periodo comprendido entre 2008 y 2014, años entre los que se encuentran los mayores éxitos del deporte español, de manera particular en el fútbol. España obtuvo en los años 2008 y 2012, los títulos de Campeón de Europa y, en 2010, el título mundial durante el campeonato celebrado en Sudáfrica y se movilizaron millones de aficionados en las calles para celebrar los triunfos. Habían seguido el acontecimiento a través de todos los medios...

Search for very high energy gamma radiation from the radio bright region DR4 of the SNR G78.2+2.1

Data from the HEGRA air shower array are used to set an upper limit on the emission of gamma-radiation above 25 (18) TeV from the direction of the radio bright region DR4 within the SNR G78.2 + 2.1 of 2.5 (7.1). 10^-13 cm^-2 sec^-1. The shock front of SNR G78.2 + 2.1 probably recently overtook the molecular cloud Gong 8 which then acts as a target for the cosmic rays produced within the SNR, thus leading to the expectation of enhanced gamma-radiation. Using a model of Drury, Aharonian and Völk which assumes that SNRs are the sources of galactic cosmic rays via first order Fermi acceleration, we calculated a theoretical prediction for the gamma-ray flux from the DR4 region and compared it with our experimental flux limit. Our 'best estimate' value for the predicted flux lies a factor of about 18 above the upper limit for gamma-ray energies above 25 TeV. Possible reasons for this discrepancy are discussed.

The outburst decay of the low magnetic field magnetar SGR 0418+5729

We report on the long-term X-ray monitoring of the outburst decay of the low magnetic field magnetar SGR 0418+5729 using all the available X-ray data obtained with RXTE, Swift, Chandra, and XMM-Newton observations from the discovery of the source in 2009 June up to 2012 August. The timing analysis allowed us to obtain the first measurement of the period derivative of SGR 0418+5729: ˙ P = 4(1) × 10−15 s s−1, significant at a ∼3.5σ confidence level. This leads to a surface dipolar magnetic field of Bdip 6 × 1012 G. This measurement confirms SGR 0418+5729 as the lowest magnetic field magnetar. Following the flux and spectral evolution from the beginning of the outburst up to ∼1200 days, we observe a gradual cooling of the tiny hot spot responsible for the X-ray emission, from a temperature of ∼0.9 to 0.3 keV. Simultaneously, the X-ray flux decreased by about three orders of magnitude: from about 1.4 × 10−11 to 1.2 × 10−14 erg s−1 cm−2. Deep radio, millimeter, optical, and gamma-ray observations did not detect the source counterpart, implying stringent limits on its multi-band emission, as well as constraints on the presence of a fossil disk. By modeling the magneto-thermal secular evolution of SGR 0418+5729, we infer a realistic age of ∼550 kyr, and a dipolar magnetic field at birth of ∼1014 G. The outburst characteristics suggest the presence of a thin twisted bundle with a small heated spot at its base. The bundle untwisted in the first few months following the outburst, while the hot spot decreases in temperature and size. We estimate the outburst rate of low magnetic field magnetars to be about one per year per galaxy, and we briefly discuss the consequences of such a result in several other astrophysical contexts.