O debate sobre os métodos de ensino nos liceus portugueses (anos 30 a 60 do século XX)

Congresso realizado nos dias 6 a 9 de Maio de 2014, em Toluca, MéxicoA presente comunicação tem como objetivo refletir sobre os métodos de ensino, ao nível do ensino secundário, tal como são propostos e debatidos por educadores e professores em duas das grandes revistas pedagógicas consagrados a esse nível de ensino e ligadas a um importante contexto de formação de professores – o Liceu Normal de Pedro Nunes situado em Lisboa. Estamos a falar do Boletim do Liceu Normal de Lisboa Pedro Nunes (1932-1938) e de Palestra. Revista de pedagogia e cultura (1957-1973).info:eu-repo/semantics/publishedVersio

A Chandra observation of the nearby Sculptor Group Sd galaxy NGC 7793

We conducted a Chandra ACIS observation of the nearby Sculptor Group Sd galaxy NGC7793 as part of a multiwavelength study of supernova remnants (SNRs) in nearby galaxies. At the assumed distance to NGC7793 of 3.91Mpc, the limiting unabsorbed luminosity of the detected discrete X-ray sources is Lₓ (0.2-10.0 keV) ≈3 x 10³⁶ erg s⁻¹. A total of 22 discrete sources were detected at the ~3σ level or greater including one ultraluminous X-ray source (ULX). Based on multiwavelength comparisons, we identify X-ray sources coincident with one SNR, the candidate microquasar N7793-S26, one H II region, and two foreground Galactic stars. We also find that the X-ray counterpart to the candidate radio SNR R3 is time variable in its X-ray emission: we therefore rule out the possibility that this source is a single SNR. A marked asymmetry is seen in the distribution of the discrete sources with the majority lying in the eastern half of this galaxy. All of the sources were analyzed using quantiles to estimate spectral properties and spectra of the four brightest sources (including the ULX) were extracted and analyzed. We searched for time variability in the X-ray emission of the detected discrete sources using our measured fluxes along with fluxes measured from prior Einstein and Röntgensatellit observations. From this study, three discrete X-ray sources are established to be significantly variable. A spectral analysis of the galaxy's diffuse emission is characterized by a temperature of kT = 0.19-0.25 keV. The luminosity function of the discrete sources shows a slope with an absolute value of Γ = -0.65 ± 0.11 if we exclude the ULX. If the ULX is included, the luminosity function has a long tail to high Lₓ with a poor-fitting slope of Γ = -0.62 ± 0.2. The ULX-less slope is comparable to the slopes measured for the distributions of NGC6946 and NGC2403 but much shallower than the slopes measured for the distributions of IC 5332 and M83. Lastly, we comment on the multiwavelength properties of the SNR population of NGC7793

Multi-frequency observations of SNR J0453-6829 in the LMC : a composite supernova remnant with a pulsar wind nebula

The Large Magellanic Cloud (LMC) is rich in supernova remnants (SNRs), which can be investigated in detail with radio, optical, and X-ray observations. SNR J0453-6829 is an X-ray and radio-bright remnant in the LMC, within which previous studies revealed the presence of a pulsar wind nebula (PWN), making it one of the most interesting SNRs in the Local Group of galaxies. We study the emission of SNR J0453-6829 to improve our understanding of its morphology, spectrum, and thus the emission mechanisms in the shell and the PWN of the remnant. We obtained new radio data with the Australia Telescope Compact Array and analysed archival XMM-Newton observations of SNR J0453-6829. We studied the morphology of SNR J0453-6829 from radio, optical, and X-ray images and investigated the energy spectra in the different parts of the remnant. Our radio results confirm that this LMC SNR hosts a typical PWN. The prominent central core of the PWN exhibits a radio spectral index αCore of -0.04 ± 0.04, while in the rest of the SNR shell the spectral slope is somewhat steeper with αShell = -0.43 ± 0.01. We detect regions with a mean polarisation of P ≈ (12 ± 4)% at 6 cm and (9 ± 2)% at 3 cm. The full remnant is of roughly circular shape with dimensions of (31 ± 1) pc x (29 ± 1) pc. The spectral analysis of the XMM-Newton EPIC and RGS spectra allowed us to derive physical parameters for the SNR. Somewhat depending on the spectral model, we obtain for the remnant a shock temperature of around 0.2 keV and estimate the dynamical age to 12 000-15 000 years. Using a Sedov model we further derive an electron density in the X-ray emitting material of 1.56 cm-3, typical for LMC remnants, a large swept-up mass of 830 Mʘ, and an explosion energy of 7.6 x 1050 erg. These parameters indicate a well evolved SNR with an X-ray spectrum dominated by emission from the swept-up material

Multi-frequency study of supernova remnants in the Large Magellanic Cloud : the case of LMC SNR J0530-7007

Context. The supernova remnants (SNRs) known in the Large Magellanic Cloud (LMC) show a variety of morphological structures in the different wavelength bands. This variety is the product of the conditions in the surrounding medium with which the remnant interacts and the inherent circumstances of the supernova event itself. Aims. This paper performs a multi-frequency study of the LMC SNR J0530-7007 by combining Australia Telescope Compact Array (ATCA), Molonglo Observatory Synthesis Telescope (MOST), Röntgensatellit (ROSAT) and Magellanic Clouds Emission Line Survey (MCELS) observations. Methods. We analysed radio-continuum, X-ray and optical data and present a multi-wavelength morphological study of LMC SNR J0530-7007. Results. We find that this object has a shell-type morphology with a size of 215′′ × 180′′ (52 pc × 44 pc); a radio spectral index (α =-0.85 ± 0.13); with [S II]/Hα > 0.4 in the optical; and the presence of non-thermal radio and X-ray emission. Conclusions. We confirmed this object as a bona-fide shell-type SNR which is probably a result of a Type Ia supernova