A search for microquasar candidates at low galactic latitudes

Recent studies of relativistic jet sources in the Galaxy, also known as microquasars, have been very useful in trying to understand the accretion/ejection processes that take place near compact objects. However, the number of sources involved in such studies is still small. In an attempt to increase the number of known microquasars we have carried out a search for new Radio Emitting X-ray Binaries (REXBs). These sources are the ones to be observed later with VLBI techniques to unveil their possible microquasar nature. To this end, we have performed a cross-identification between the X-ray ROSAT all sky survey Bright Source Catalog (RBSC) and the radio NRAO VLA Sky Survey (NVSS) catalogs under very restrictive selection criteria for sources with |b|<5 degrees. We have also conducted a deep observational radio and optical study for six of the selected candidates. At the end of this process two of the candidates appear to be promising, and deserve additional observations aimed to confirm their proposed microquasar nature

X-ray and radio observations of RX J1826.2-1450/LS 5039

RX J1826.2-1450/LS 5039 has been recently proposed to be a radio emitting high mass X-ray binary. In this paper, we present an analysis of its X-ray timing and spectroscopic properties using different instruments on board the RXTE satellite. The timing analysis indicates the absence of pulsed or periodic emission on time scales of 0.02-2000 s and 2-200 d, respectively. The source spectrum is well represented by a power-law model, plus a Gaussian component describing a strong iron line at 6.6 keV. Significant emission is seen up to 30 keV, and no exponential cut-off at high energy is required. We also study the radio properties of the system according to the GBI-NASA Monitoring Program. RX J1826.2-1450/LS 5039 continues to display moderate radio variability with a clearly non-thermal spectral index. No strong radio outbursts have been detected after several months

The changing milliarcsecond radio morphology of the gamma-ray binary LS 5039

LS 5039 is one of the few TeV emitting X-ray binaries detected so far. The powering source of its multiwavelength emission can be accretion in a microquasar scenario or wind interaction in a young nonaccreting pulsar scenario. Aims.To present new high-resolution radio images and compare them with the expected behavior in the different scenarios. Methods.We analyze Very Long Baseline Array (VLBA) radio observations that provide morphological and astrometric information at milliarcsecond scales. Results.We detect a changing morphology between two images obtained five days apart. In both runs there is a core component with a constant flux density, and an elongated emission with a position angle (PA) that changes by 12 $\pm$ 3\degr between both runs. The source is nearly symmetric in the first run and asymmetric in the second one. The astrometric results are not conclusive. Conclusions.A simple and shockless microquasar scenario cannot easily explain the observed changes in morphology. An interpretation within the young nonaccreting pulsar scenario requires the inclination of the binary system to be very close to the upper limit imposed by the absence of X-ray eclipses

Monografies del Montseny - 37

Antoni Pladevall Font va fer possible el naixement de la col.lecció completa de les Monografies del Montseny, n’ha estat el director durant molts anys, ha publicat més de seixanta treballs d’investigació històrica, i ha estat el mestre que ha mostrat el camí a seguir en la tasca d’aprofundiment de la història del Montseny i el seu entorn més proper. En el pròleg del volum 37 de les Monografies del Montseny es glosa la figura d’Antoni Pladevall Font, qui l’any 1966 inicià la col·laboració en el Servei de Conservació i Catalogació de Monuments Històrics a la Diputació de Barcelona; dos anys més tard, passà a exercir com a professor d’història medieval a la Facultat de Teologia de Barcelona. Obtingué el títol d’Arxiver Municipal de Vic l’any 1979, mentre treballa a la Diputació, i al 1981començà a treballar en el Departament de Cultura de la Generalitat fins a la seva jubilació l’any 1999. L’aleshores conseller de Cultura de la Generalitat Max Cahner li va encarregar d’organitzar el Servei de Conservació i Restauració de Monuments Arquitectònics on se li va assignar la secció d’inventari i la de cap de servei en funcions. Dos anys després hi va exercir com a director general del Patrimoni Arquitectònic. En aquesta etapa va col·laborar amb la Fundació i Editorial de la Gran Enciclopèdia Catalana, en la qual va exercir la direcció d’obres tan importants com la “Catalunya Romànica” i “L’Art Gòtic de Catalunya”, i va assessorar la “Gran Geografia Comarcal de Catalunya”.Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesObjectius de Desenvolupament Sostenible::4 - Educació de QualitatPostprint (published version

All-cause mortality in the cohorts of the Spanish AIDS Research Network (RIS) compared with the general population: 1997Ł2010

Abstract Background: Combination antiretroviral therapy (cART) has produced significant changes in mortality of HIVinfected persons. Our objective was to estimate mortality rates, standardized mortality ratios and excess mortality rates of cohorts of the AIDS Research Network (RIS) (CoRIS-MD and CoRIS) compared to the general population. Methods: We analysed data of CoRIS-MD and CoRIS cohorts from 1997 to 2010. We calculated: (i) all-cause mortality rates, (ii) standardized mortality ratio (SMR) and (iii) excess mortality rates for both cohort for 100 personyears (py) of follow-up, comparing all-cause mortality with that of the general population of similar age and gender. Results: Between 1997 and 2010, 8,214 HIV positive subjects were included, 2,453 (29.9%) in CoRIS-MD and 5,761 (70.1%) in CoRIS and 294 deaths were registered. All-cause mortality rate was 1.02 (95% CI 0.91-1.15) per 100 py, SMR was 6.8 (95% CI 5.9-7.9) and excess mortality rate was 0.8 (95% CI 0.7-0.9) per 100 py. Mortality was higher in patients with AIDS, hepatitis C virus (HCV) co-infection, and those from CoRIS-MD cohort (1997. Conclusion: Mortality among HIV-positive persons remains higher than that of the general population of similar age and sex, with significant differences depending on the history of AIDS or HCV coinfection

Microquasars in the galaxy

[eng] Microquasars are X-ray binary stars capable of generating relativistic jets. Galactic microquasars are one of the most recent additions to the field of high energy astrophysics and have attracted increasing interest over the last decade. They are now primary targets for all space-based observatories working in the X-ray and γ-ray domains. The hope is that their study will enable us to understand some of the analogous phenomena observed in distant quasars and active galactic nuclei, which have practically the same scaled-up physics as microquasars. Microquasars are also believed to be among the sources responsible for the violent and everchanging appearance of the γ-ray sky. This paper provides a general review of the field of microquasars, including their identification and study, and discusses the recent observational and theoretical discoveries which we regard as being of most relevance.[cat] Els microquàsars a la galàxia constitueixen, sense cap mena de dubte, una de les més recents aportacions en astrofísica d’altes energies. L’estudi d’aquests objectes nous, estels binaris de raigs X amb ejeccions de plasma relativista, s’ha estès amb rapidesa en la darrera dècada i representa un objectiu de primera magnitud per a la generació actual d’observatoris espacials de raigs X i raigs γ. Darrere d’aquest insòlit interés, existeix l’esperança fundada que el fet d’estudiar-los pugui contribuir a comprendre millor fenòmens anàlegs en quàsars i altres nuclis de galàxies actives que comparteixen una física comuna, salvant les diferències d’escala. Es creu també que els microquàsars es troben entre els responsables del caràcter violent i mutable del firmament de raigs γ, el qual gairebé comencem a percebre. En aquest article passem revista a l’estat general sobre el tema dels microquàsars, la seva identificació i estudi, a la vegada que exposem quines han estat les troballes observacionals i teòriques recents més rellevants en la nostra opinió

Chinese astronomy as an indicator of technological development

Este artículo ilustra la cerrada relación entre el desarrollo tecnológico y el progreso científico. Ejemplos de estas conexiones se pueden ver en el caso de estudio de la astronomía china. Aspectos remarcables en el historial de las contribuciones al conocimiento de los cuerpos celestes, el papel de China en la moderna astronomía y el papel de los astrónomos en tiempos recientes. Únicamente en las últimas décadas China ha iniciado su desarrollo en proyectos astronómicos (telescopios ópticos, estaciones de radio…). Estos avances, y su uso, permiten excelentes capacidades para estudiar la astronomía a través de diferentes ventanas. Además, los astrónomos chinos son miembros activos a través de diversas colaboraciones internacionales.Palabras clave: China, astronomía, tecnología, telescopios._______________________Abstract:This paper illustrated the close relationship between technology development and progress in science. Examples of this connection are discussed using Chinese Astronomy as a study case. Despite remarkable historical contributions to the knowledge of celestial bodies, the role of China in modern Astronomy and Astrophysics did not start until relatively recent times. Only in the last decades has China started to develop impressive astronomical projects (optical telescopes, interferometric radio networks, Cherenkov detector arrays, etc.) in parallel with the country's growth.These facilities provide, or will soon provide, excellent capabilities for observational astronomy in different windows of the electromagnetic spectrum. In addition, Chinese astronomers are currently active members of the major international astronomical collaborations.Keywords: China, astronomy, technology, telescopes.</div

Discovery of a High-Energy Gamma-Ray-Emitting Persistent Microquasar

Microquasars are stellar x-ray binaries that behave as a scaled down version of extragalactic quasars. The star LS 5039 is a new microquasar system with apparent persistent ejection of relativistic plasma at a 3 kiloparsec distance from the sun. It may also be associated with a gamma-ray source discovered by the Energetic Gamma Ray Experiment Telescope (EGRET) on board the COMPTON-Gamma Ray Observatory satellite. Before the discovery of LS 5039, merely a handful of microquasars had been identified in the Galaxy, and none of them was detected in high-energy gamma-rays

Chorros relativistas de origen estelar: los microcuasares

Galactic microquasars are certainly one of the most recent additions to the field of high energy Astrophysics. These new objects are just X-ray binaries with the ability to generate relativistic jets and their interest has been growing during the last decade. Today, they represent primary targets for all space based observatories working in the X-ray and [gamma]-ray domains. Behind such interest, there is hope that their study will assist us to understand some of the analog phenomena observed in distant quasars and active galactic nuclei, wich share with microquasars practically the same scaled-up physics. Microquasars are also believed to be among the different kind of sources responsible for the violent and ever changing appearance of the [gamma]-ray ski. In this paper we review the general situation of the microquasar topic, their identification and study, including comments on the recent observational and theoretical discoveries most relevant in our opinion

Chorros relativistas de origen estelar: los microcuasares

Galactic microquasars are certainly one of the most recent additions to the field of high energy Astrophysics. These new objects are just X-ray binaries with the ability to generate relativistic jets and their interest has been growing during the last decade. Today, they represent primary targets for all space based observatories working in the X-ray and [gamma]-ray domains. Behind such interest, there is hope that their study will assist us to understand some of the analog phenomena observed in distant quasars and active galactic nuclei, wich share with microquasars practically the same scaled-up physics. Microquasars are also believed to be among the different kind of sources responsible for the violent and ever changing appearance of the [gamma]-ray ski. In this paper we review the general situation of the microquasar topic, their identification and study, including comments on the recent observational and theoretical discoveries most relevant in our opinion