X-ray spectral variability of seven LINER nuclei with XMM-Newton and Chandra data

One of the most important features in active galactic nuclei (AGN) is the variability of their emission. Variability has been discovered at X-ray, UV, and radio frequencies on time scales from hours to years. Among the AGN family and according to theoretical studies, Low-Ionization Nuclear Emission Line Region (LINER) nuclei would be variable objects on long time scales. Our purpose is to investigate spectral X-ray variability in LINERs and to understand the nature of these kinds of objects, as well as their accretion mechanism. Chandra and XMM-Newton public archives were used to compile X-ray spectra of seven LINER nuclei at different epochs with time scales of years. To search for variability we fit all the spectra from the same object with a set of models, in order to identify the parameters responsible for the variability pattern. We also analyzed the light curves in order to search for short time scale (from hours to days) variability. Whenever possible, UV variability was also studied. We found spectral variability in four objects, with variations mostly related to hard energies (2-10 keV). These variations are due to changes in the soft excess, and/or changes in the absorber, and/or intrinsic variations of the source. Another two galaxies seem not to vary. Short time scale variations during individual observations were not found. Our analysis confirms the previously reported anticorrelation between the X-ray spectral index and the Eddington ratio, and also the correlation between the X-ray to UV flux ratio and the Eddington ratio. These results support an Advection Dominated Accretion Flow (ADAF) as the accretion mechanism in LINERs.Comment: 35 pages, 53 figures, recently accepted pape

X-ray spectral variability of Seyfert 2 galaxies

Variability across the electromagnetic spectrum is a property of AGN that can help constraining the physical properties of these galaxies. This is the third of a serie of papers with the aim of studying the X-ray variability of different families of AGN. The main purpose of this work is to investigate the variability pattern in a sample of optically selected type 2 Seyfert galaxies. We use the 26 Seyferts in the Veron-Cetty and Veron catalogue with data available from Chandra and/or XMM-Newton public archives at different epochs, with timescales ranging from a few hours to years. All the spectra of the same source are simultaneously fitted and we let different parameters to vary in the model. Whenever possible, short-term variations and/or long-term UV flux variations are studied. We divide the sample in Compton-thick, Compton-thin, and changing-look candidates. Short-term variability at X-rays is not found. From the 25 analyzed sources, 11 show long-term variations; eight (out of 11) are Compton-thin, one (out of 12) is Compton-thick, and the two changing-look candidates are also variable. The main driver for the X-ray changes is related to the nuclear power (nine cases), while variations at soft energies or related with absorbers at hard X-rays are less common, and in many cases these variations are accompained with variations of the nuclear continuum. At UV frequencies nuclear variations are nor found. We report for the first time two changing-look candidates, MARK273 and NGC7319. A constant reflection component located far away from the nucleus plus a variable nuclear continuum are able to explain most of our results; the Compton-thick candidates are dominated by reflection, which supresses their continuum making them seem fainter, and not showing variations, while the Compton-thin and changing-look candidates show variations.Comment: Accepted for publication in A&

X-ray spectral variability of LINERs selected from the Palomar sample

Variability is a general property of active galactic nuclei (AGN). At X-rays, the way in which these changes occur is not yet clear. In the particular case of low ionisation nuclear emission line region (LINER) nuclei, variations on months/years timescales have been found for some objects, but the main driver of these changes is still an open question. The main purpose of this work is to investigate the X-ray variability in LINERs, including the main driver of such variations, and to search for eventual differences between type 1 and 2 objects. We use the 18 LINERs in the Palomar sample with data retrieved from Chandra and/or XMM-Newton archives corresponding to observations gathered at different epochs. All the spectra for the same object are simultaneously fitted in order to study long term variations. The nature of the variability patterns are studied allowing different parameters to vary during the spectral fit. Whenever possible, short term variations from the analysis of the light curves and UV variability are studied.Comment: 49 pages, accepted. arXiv admin note: text overlap with arXiv:1305.222

An infinite family of magnetized Morgan-Morgan relativistic thin disks

Applying the Horsk\'y-Mitskievitch conjecture to the empty space solutions of Morgan and Morgan due to the gravitational field of a finite disk, we have obtained the corresponding solutions of the Einstein-Maxwell equations. The resulting expressions are simply written in terms of oblate spheroidal coordinates and the solutions represent fields due to magnetized static thin disk of finite extension. Now, although the solutions are not asymptotically flat, the masses of the disks are finite and the energy-momentum tensor agrees with the energy conditions. Furthermore, the magnetic field and the circular velocity show an acceptable physical behavior.Comment: Submitted to IJTP. This paper is a revised and extended version of a paper that was presented at arXiv:1006.203

Psocoptera (Insecta: Psocodea) from the National Natural Park Gorgona, Cauca, Colombia

The Psocoptera fauna of Gorgona National Natural Park, Colombian pacific, consists of 75 species in 42 genera and 21 families. 1 730 specimens were collected in the period November 2007-June 2011. Five families, 20 genera and nine species are new records for Colombia, and two genera and ten species are new to science. The psocid fauna of the island constitutes an extension of the continental fauna

Three new species of Loneura (Psocodea:’Psocoptera’:Ptiloneuridae) from Gorgona Island, Cauca, Colombia, with a new infrageneric classification

Three related species of Loneura Navás, from Gorgona Island (Cauca, Colombia), are here described and illustrated. The types are deposited in the Entomological Museum of the Universidad del Valle (MUSENUV). A set of infrageneric groups within Loneura is proposed based on the structure of the male hypandrium and phallosome. The species of the genus are assigned to the groups recognized in this classification

Scaling Analysis of Improved Actions for Pure SU(3) Gauge Theory

We have explored the behaviour of some improved actions based on a nonperturbative renormalization group (RG) analysis in coupling space. We calculate the RG flow in two-coupling space (\boneone,\bonetwo) and examine the restoration of rotational invariance and the scaling of physical quantities $(T_c/\sqrt{\sigma})$.Comment: LATTICE98(improvement

Decision making and skill development In youth football players

Este artículo presenta como se desarrolla la toma de decisiones y la habilidad técnica en jugadores con alto nivel de pericia desde los 6-7 a 13-14 años. El marco teórico está basado en la perspectiva de los sistemas dinámicos y la enseñanza comprensiva de los deportes. Se tomó como muestra a 57 jugadores del primer equipo de cada categoría de edad del Albacete Balompié: prebenjamín, benjamín, alevín e infantil. El instrumento usado fue la Herramienta de Evaluación del Rendimiento de Juego (HERJ), que mide la toma de decisiones y la ejecución, incluyendo el análisis ecológico atendiendo a principios tácticos (Bayer, 1992), comparando la situación en el juego con la decisión aplicada. Los resultados se basan en el análisis inferencial y correlacional. La evolución del rendimiento de juego se orienta desde el ataque hasta la defensa. Se han encontrado diferencias significativas en las variables entre las cuatro categorías de formación estudiadas, especialmente en el principio táctico de progresar hacia la portería contraria y en el desmarque, así como en el marcaje y la ayuda en defensa.This paper presents how decision-making and skills are developed in high level of expertise players from 6-7 to 13-14 years. The framework is based on the dynamical systems and teaching games for understanding approaches. Participants were 57 first team players of each age (n = 13 to 16) of Albacete Balompié: U-8, U-10, U-12 and U-14. The Game Performance Assessment Tool (GPET) was the instrument used for assessment, which measures decision-making and execution from an ecological view in relation to tactical principles (Bayer, 1992), comparing the game situation with the decision applied. The results are based on inferential and correlation analysis. The evolution of knowledge evolves attack to defensive. We have found significant differences in variables between the four age categories studied. These differences have been shown in attack: the progress toward goal tactical principle and shake off; on defence: marking and cover (off-ball defenders)

A survey of the genera Sarcodictyon Forbes, 1847, and rolandia Lacaze-Duthiers, 1900, (anthozoa: octocorallia) in the North-eastern Atlantic and the Mediterranean

Sarcodictyon catenatum Forbes, 1847, is a common species in the Atlantic and the Mediterranean. However, often it has been mistaken for Rolandia coralloides Lacaze-Duthiers, 1900. On the basis of British and Mediterranean material we studied the main characters for distinguishing S. catenatum. We consider Rolandia coralloides Lacaze-Duthiers, 1900, to be a valid species and we assign to it all the material named Rolandia rosea by S. Weinberg (1978). Furthermore, a histological study confirmed that R. coralloides typically forms groups of polyps embedded in a common coenenchyme. Therefore, the possibility of transferring R. coralloides from Stolonifera to Alcyonacea is discussed. Evagorgia rosea Philippi, 1842, is here considered to be a nomen dubium