A Rapidly Spinning Black Hole Powers the Einstein Cross

Observations over the past 20 years have revealed a strong relationship between the properties of the supermassive black hole (SMBH) lying at the center of a galaxy and the host galaxy itself. The magnitude of the spin of the black hole will play a key role in determining the nature of this relationship. To date, direct estimates of black hole spin have been restricted to the local Universe. Herein, we present the results of an analysis of $\sim$ 0.5 Ms of archival Chandra observations of the gravitationally lensed quasar Q 2237+305 (aka the "Einstein-cross"), lying at a redshift of z = 1.695. The boost in flux provided by the gravitational lens allows constraints to be placed on the spin of a black hole at such high redshift for the first time. Utilizing state of the art relativistic disk reflection models, the black hole is found to have a spin of $a_* = 0.74^{+0.06}_{-0.03}$ at the 90% confidence level. Placing a lower limit on the spin, we find $a_* \geq 0.65$ (4$\sigma$). The high value of the spin for the $\rm \sim 10^9~M_{\odot}$ black hole in Q 2237+305 lends further support to the coherent accretion scenario for black hole growth. This is the most distant black hole for which the spin has been directly constrained to date.Comment: 5 pages, 3 figures, 1 table, formatted using emulateapj.cls. Accepted for publication in ApJ

A “nova” nova Praça Roosevelt

Entrevista conduzida por Ramón Stock Bonzi.Entrevista conduzida por Ramón Stock Bonzi

The Quiescent X-ray Spectrum of Accreting Black Holes

The quiescent state is the dominant accretion mode for black holes on all mass scales. Our knowledge of the X-ray spectrum is limited due to the characteristic low luminosity in this state. Herein, we present an analysis of the sample of dynamically-confirmed stellar-mass black holes observed in quiescence in the \textit{Chandra/XMM-Newton/Suzaku} era resulting in a sample of 8 black holes with $\sim$ 570 ks of observations. In contrast to the majority of AGN where observations are limited by contamination from diffuse gas, the stellar-mass systems allow for a clean study of the X-ray spectrum resulting from the accretion flow alone. The data are characterized using simple models. We find a model consisting of a power-law or thermal bremsstrahlung to both provide excellent descriptions of the data, where we measure $\rm \Gamma = 2.06 \pm 0.03$ and $\rm kT = 5.03^{+0.33}_{-0.31} keV$ respectively in the 0.3 -- 10 keV bandpass, at a median luminosity of $\rm L_x \sim 5.5\times10^{-7} L_{Edd}$. This result in discussed in the context of our understanding of the accretion flow onto stellar and supermassive black holes at low luminosities.Comment: 12 pages, 5 figures, 2 tables, MNRAS accepte

A comparison of broad iron emission lines in archival data of neutron star low-mass X-ray binaries

Relativistic X-ray disk-lines have been found in multiple neutron star low-mass X-ray binaries, in close analogy with black holes across the mass-scale. These lines have tremendous diagnostic power and have been used to constrain stellar radii and magnetic fields, often finding values that are consistent with independent timing techniques. Here, we compare CCD-based data from Suzaku with Fe K line profiles from archival data taken with gas-based spectrometers. In general, we find good consistency between the gas-based line profiles from EXOSAT, BeppoSAX and RXTE and the CCD data from Suzaku, demonstrating that the broad profiles seen are intrinsic to the line and not broad due to instrumental issues. However, we do find that when fitting with a Gaussian line profile, the width of the Gaussian can depend on the continuum model in instruments with low spectral resolution, though when the different models fit equally well the line widths generally agree. We also demonstrate that three BeppoSAX observations show evidence for asymmetric lines, with a relativistic disk-line model providing a significantly better fit than a Gaussian. We test this by using the posterior predictive p-value method, and bootstrapping of the spectra to show that such deviations from a Gaussian are unlikely to be observed by chance.Comment: 13 pages, 9 figures, accepted to Ap

Sonority effects in the production of the triconsonantal sequences Ct/d]σC by Brazilian learners of L2 English

This study investigates the production of a variable pattern in English by Brazilian L2 learners, i.e. triconsonantal sequences containing coronal plosives flanked by heterosyllabic consonants. Thus, the interlanguage of 24 learners from the city of Campina Grande in the state of Paraíba, Brazil, is analyzed to achieve the following objectives: (1) verify the phonological processes whereby the sequences Ct/d]σC are simplified in the participants’ interlanguage; and (2) examine the role of sonority in the surface phonetic representations of these sequences. 1,071 tokens were audio-recorded, coded and subjected to multivariate analysis using Rbrul (JOHNSON, 2015). The results indicate that sonority-based principles play an important role in the application of repair strategies on the surface forms of these complex structures

DISTRIBUIÇÃO REGIONAL DAS INSTITUIÇÕES DE ENSINO SUPERIOR GRATUITO NO ESTADO DE SANTA CATARINA: A LACUNA NA MESORREGIÃO DO VALE DO ITAJAÍ E AS CONTRADIÇÕES DAS POLÍTICAS PÚBLICAS DE EXPANSÃO DE VAGAS

O debate sobre democratização do Ensino Superior no Brasil é um tema recorrente, sendo que a garantia do acesso é uma das questões centrais destas discussões. Tratar da “democratização do ensino superior” implica no enfrentamento de questões ligadas ao acesso de um maior número de estudantes a esse grau de ensino. O presente artigo tem como objeto central analisar as políticas públicas de acesso com base no mapeamento das Instituições de Ensino Superior públicas gratuitas no Estado de Santa Catarina, considerando para o mapeamento a divisão geopolítica mesorregional do IBGE. Trata-se de uma pesquisa de cunho qualitativo interpretativo. O corpus da pesquisa foi constituído por dados do IBGE e informações disponibilizadas pelas instituições. Após a análise dos dados, se pode dizer que 37,5% das IES públicas gratuitas que oferta mais de três cursos superiores estão concentradas na mesorregião da Grande Florianópolis, em detrimento de outras regiões do território catarinense. Verifica-se que apenas 3,39% dos municípios do Estado possuem IES pública gratuita que oferta mais de três cursos superiores

O princípio da Teoria da Agência em movimentos ciberativistas

Analisar o processo histórico no que tange a constituição de movimentos sociais é analisar a forma de organização humana e de comunicação neles existentes. O objetivo deste estudo é mostrar que perspectivas recentes de organização humana dadas através de redes de internet, mesmo em redes sociais virtuais (RSVs), também cabem em análises já consolidadas, como é o caso da teoria da agência descrita por Sztompka (2005). Trata-se de um estudo qualitativo, predominantemente teórico. Como resultado deste ensaio, destaca-se que em qualquer mobilização social existe uma essência comum que está por detrás de sua organização, inclusive naquelas ciberativistas: o agente humano, que por sua vez, unido a demais agentes, podem buscar mudanças sociais.