33 research outputs found
The awakening of BL Lacertae: observations by Fermi, Swift and the GASP-WEBT
No full textSince the launch of the Fermi satellite, BL Lacertae has been moderately active at ?-rays and optical frequencies until 2011 May, when the source started a series of strong flares. The exceptional optical sampling achieved by the GLAST–AGILE Support Program of the Whole Earth Blazar Telescope in collaboration with the Steward Observatory allows us to perform a detailed comparison with the daily γ-ray observations by Fermi. Discrete correlation analysis between the optical and γ-ray emission reveals correlation with a time lag of 0 ± 1 d, which suggests cospatiality of the corresponding jet emitting regions. A better definition of the time lag is hindered by the daily gaps in the sampling of the extremely fast flux variations. In general, optical flares present more structure and develop on longer time-scales than corresponding γ-ray flares. Observations at X-rays and at millimetre wavelengths reveal a common trend, which suggests that the region producing the mm and X-ray radiation is located downstream from the optical and γ-ray-emitting zone in the jet. The mean optical degree of polarization slightly decreases over the considered period and in general it is higher when the flux is lower. The optical electric vector polarization angle (EVPA) shows a preferred orientation of about 15°, nearly aligned with the radio core EVPA and mean jet direction. Oscillations around it increase during the 2011–2012 outburst. We investigate the effects of a geometrical interpretation of the long-term flux variability on the polarization. A helical magnetic field model predicts an evolution of the mean polarization that is in reasonable agreement with the observations. These can be fully explained by introducing slight variations in the compression factor in a transverse shock waves model
The XMM-Newton long look of NGC 1365: uncovering of the obscured X-ray source
No full textWe present an analysis of the extreme obscuration variability observed during an XMM–Newton 5-d continuous monitoring of the active galactic nuclei (AGN) in NGC 1365. The source was in a reflection-dominated state in the first ∼1.5 d, then a strong increase in the 7–10 keV emission was observed in ∼10 h, followed by a symmetric decrease. The spectral analysis of the different states clearly shows that this variation is due to an uncovering of the X-ray source. From this observation, we estimate a size of the X-ray source DS < 1013 cm, a distance of the obscuring clouds R∼ 1016 cm and a density n∼ 1011 cm−3. These values suggest that the X-ray absorption/reflection originates from the broad-line region clouds. This is also supported by the resolved width of the iron narrow Kα emission line, consistent with the width of the broad Hβ line
Comunicación familiar prevalente en estudiantes de una institución educativa nacional, Nuevo Chimbote, 2018
No full textEl presente estudio tuvo como objetivo describir la comunicación familiar en estudiantes de una institución educativa nacional, Nuevo Chimbote, 2018. Su tipo de estudio observacional, prospectivo, transversal y descriptivo. Asimismo, el nivel de investigación fue descriptivo, así como su diseño fue epidemiológico. Su universo estaba conformado por estudiantes de nivel secundario. A su vez, la población estuvo constituida por los estudiantes de la institución educativa nacional “Fe y Alegría” Nº 14, el número total de alumnos fue de N= 673, realizando un muestreo no probabilístico, de tipo por conveniencia, en donde se buscó alcanzar un número de participantes n=277, con un cálculo estadístico para lograr las metas de la evaluación. El instrumento empleado en el informe fue la Escala de Comunicación Familiar (FCS), El resultado obtenido en el estudio de la comunicación familiar en la institución educativa nacional, Nuevo Chimbote, 2018, se halló que la población estudiada la más alta se encuentra en una comunicación familiar media.Tesi
Gamma-ray performance study of the HERD payload
No full textThe High Energy cosmic-Radiation Detection (HERD) facility has been proposed as a space astronomy payload onboard the future China's Space Station. HERD is planned for operation starting around 2027 for about 10 years In addition to the unprecedented sensitivity for dark matter searches and cosmic-ray measurements up to the knee energy, it should perform gamma-ray monitoring and full sky survey from few hundred MeV up to tens of TeV. We present the first study of the HERD gamma-ray performance obtained with full simulations of the whole detector geometry. HERD will be a cubic detector composed with 5 active faces. We present a study conducted inside the HERD analysis software package, which includes a detailed description of the detector materials. In this work we present the HERD effective area, the point spread function and the resulting gamma-ray sensitivity. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0
Polarimetry of the transient relativistic jet of GRB 110328/Swift J164449.3+573451
No full textWe present deep infrared (Ks-band) imaging polarimetry and radio (1.4- and 4.8-GHz) polarimetry of the enigmatic transient Swift J164449.3+573451. This source appears to be a short-lived jet phenomenon in a galaxy at redshift z= 0.354, activated by a sudden mass accretion on to the central massive black hole, possibly caused by the tidal disruption of a star. We aim to find evidence for this scenario through linear polarimetry, as linear polarization is a sensitive probe of jet physics, source geometry and the various mechanisms giving rise to the observed radiation. We find a formal Ks-band polarization measurement of Plin= 7.4 ± 3.5 per cent (including systematic errors). Our radio observations show continuing brightening of the source, which allows sensitive searches for linear polarization as a function of time. We find no evidence of linear polarization at radio wavelengths of 1.4 and 4.8 GHz at any epoch, with the most sensitive 3σ limits as deep as 2.1 per cent. These upper limits are in agreement with expectations from scenarios in which the radio emission is produced by the interaction of a relativistic jet with a dense circumsource medium. We further demonstrate how polarization properties can be used to derive properties of the jet in Swift J164449.3+573451, exploiting the similarities between this source and the afterglows of gamma-ray bursts
Wavefront improvement in an injection-seeded soft x-ray laser based on a solid-target plasma amplifier
No full textInternational audienceThe wavefront of an injection-seeded soft x-ray laser beam generated by amplification of high-harmonic pulses in a lambda = 18.9 nm molybdenum plasma amplifier was measured by a Hartmann wavefront sensor with an accuracy of lambda/32 root mean square (rms). A significant improvement in wavefront aberrations of 0.51 +/- 0.03 lambda rms to 0.23 +/- 0.01 lambda rms was observed as a function of plasma column length. The variation of wavefront characteristic as a function time delay between the injection of the seed and peak of soft x-ray amplifier pump was studied. The measurements were used to reconstruct the soft x-ray source and confirm its high peak brightness. (C) 2013 Optical Society of Americ
Femtosecond soft x-ray lasing in dense collisionaly-pumped plasma
No full textInternational audienceWe report the first experimental measurement of a strong pulse shortening of a seeded plasma-based soft x-ray laser at high electron densities. As a consequence of the gain gating caused by subsequent collisional ionization, the duration drops from 1.4 ps to an unprecedented value of 520 fs RMS when the electron density increases from 4 to 7.6×1019cm-3. These measurements, performed with an original single-shot method, are in good agreement with results from 3D Maxwell-Bloch simulations. © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DO
The Plastic Scintillator Detector of the HERD space mission
No full textThe High Energy cosmic-Radiation (HERD) detector is one of the prominent space-borne instruments to be installed on-board the Chinese Space Station (CSS), around 2027. Primary scientific goals regarding this initiative include: precise measurements of cosmic ray (CR) energy spectra and mass composition, at energies up to the PeV range; contributions to high energy gamma-ray astronomy and transient studies; as well as indirect searches for Dark Matter (DM) particles via their possible annihilation/decay to detectable products. HERD is configured to accept incident particles from both its top and four lateral sides. Owing to its pioneering design, an order of magnitude increase in acceptance is foreseen, with respect to previous and ongoing experiments. The Plastic Scintillator Detector (PSD) constitutes an important sub-detector of HERD, particularly aimed towards anti-coincidence (discriminating incident photons from charged particles), while providing precise charge measurement of incoming cosmic-ray nuclei in a range of Z = 1-26. Main requirements concerning its design, include: high detection efficiency, broad dynamic range and good energy resolution. In order to select the optimal layout, two geometries are currently under investigation: one based on long scintillator bars and the other on square tiles, with both layouts being readout by Silicon Photomultipliers (SiPMs). Ongoing activities and future plans regarding the HERD PSD will be presented in this work. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0
Test adaptativos informatizados, pruebas computarizadas y pruebas en aplicaciones móviles: comparación de su disponibilidad actual en Latinoamérica, Estados Unidos y Canadá
No full textPsychometric tests have changed their pencil and paper format into computerized evaluations progressively in the last 40 years, since the computerized format offers several advantages over the classic one. In this study we compared the production and availability of computerized adaptive tests (CAT), computerized tests (CT) and tests in mobile applications (TMA), between the United States/Canada and Latin America. We conducted a narrative review, exploring databases such as PsycInfo, Scopus, Web of Science, Pubmed, and Scielo. To complement the findings, we conducted a search on Google and the Play Store. The results showed that the United States/Canada records the highest production and availability of CAT/CT/TMA. In both regions, most of CAT/CT are designed to evaluate adults, while TMA are designed for any age. In the United States/Canada, CAT/CT are mostly original, and their use requires a previous payment, while in Latin America, CAT/CT/TMA are usually adapted and freely available versions. Finally, there is a huge difference in the availability of CAT/CT/TMA between both regions. The United States/Canada has at its disposal more than thirteen times the amount of CAT, more than double the amount of CT and more than five times the amount of TMA than Latin America. We concluded that there is a large gap in production and access to high-tech psychometric instruments that Latin America needs to overcome. Finally, we provide a list of all CAT/CT/TMA currently available, free or paid access.Las pruebas psicométricas han cambiado su formato de lápiz y papel a evaluaciones informatizadas progresivamente en los últimos 40 años, debido a que el formato informatizado ofrece varias ventajas sobre el clásico. En este estudio comparamos la producción y disponibilidad de los test adaptativos informatizados (TAI), las pruebas computarizadas (PC) y las pruebas en aplicativos móviles (PAM) entre Estados Unidos, Canadá y Latinoamérica. Realizamos una revisión narrativa, explorando bases de datos como PsycINFO, Scopus, Web of Science, PubMed y SciELO. Para complementar los hallazgos, realizamos una búsqueda en Google y Play Store. Los resultados mostraron que Estados Unidos y Canadá registran la mayor producción y disponibilidad de TAI, PC y PAM. En ambas regiones, la mayor parte de los TAI y las PC está diseñada para evaluar a los adultos, mientras que las PAM están diseñadas para cualquier edad. En Estados Unidos y Canadá, los TAI y las PC son en gran parte originales y su uso requiere de un pago previo, mientras que en Latinoamérica los TAI, las PC y las PAM suelen ser versiones adaptadas y de acceso libre. Finalmente, existe una brecha amplia en la disponibilidad de TAI, PC y PAM en ambas regiones. Estados Unidos y Canadá tienen a su disposición más de trece veces la cantidad de TAI, más del doble de cantidad de PC y más del quíntuple de cantidad de PAM que en Latinoamérica. Concluimos que existe una gran brecha en cuanto a la producción y el acceso a instrumentos psicométricos de alta tecnología que Latinoamérica necesita superar. Finalmente, proveemos un listado de todos los TAI, las PC y las PAM disponibles actualmente, de acceso gratuito y de pago
Design and expected performances of the large acceptance calorimeter for the HERD space mission
No full textThe High Energy cosmic-Radiation Detection (HERD) is a future space experiment which will be installed on the China’s Space Station around 2027. The main goal of the experiment is the measurement of cosmic rays up to energies which are not explored by the instruments currently operating in space, in particular protons with energies up to PeV, nuclei up to hundreds of TeV per nucleon and electrons up to tens of TeV. HERD will consist of silicon charge detectors, anti-coincidence scintillators, scintillating fiber trackers, a transition radiation detector and a calorimeter. The latter is a homogeneous, deep, 3D segmented calorimeter made of about 7500 LYSO cubic crystals: thanks to this innovative design, it will achieve large acceptance, good energy resolution and excellent electron/proton discrimination. In order to increase both energy calibration capabilities and redundancy of the instrument, the LYSO scintillation light will be read-out by two independent systems: the first is made of wave-length shifting fibers coupled with imaged intensified CMOS cameras, and the second one consists of photodiodes with different active areas connected to a custom front-end electronics. Both read-out systems are designed to have a large dynamic range, up to 107, and a low power consumption. The design of the calorimeter is validated by several Monte Carlo simulations and beam test results obtained with detector prototypes. In this paper we describe the anticipated performances of the calorimeter and the current status of the double read-out system, and we discuss the recent developments of both the HERD prototype and the flight model design. © Copyright owned by the author(s)
