67 research outputs found
A constru??o discursiva da mineiridade a partir de jornais marianenses.
Programa de P?s-Gradua??o em Letras. Departamento de Letras, Instituto de Ci?ncias Humanas e Sociais, Universidade Federal de Ouro Preto.No contexto social, lingu?stico e cultural do Brasil, variados tra?os culturais t?m seu papel nas
diferentes regi?es do pa?s. No estado de Minas Gerais, o fen?meno da mineiridade ? um desses
tra?os que merecem ser pensados especialmente se levarmos em considera??o suas
manifesta??es discursivas. Sendo assim, o que chamaremos de imagin?rio s?cio-discursivo de
mineiridade pode ser depreendido de diferentes tipos de m?dia impressa, como ? o caso dos
jornais marianenses. Neste trabalho, procuraremos destacar elementos do imagin?rio s?ciodiscursivo
de mineiridade identific?veis nos jornais que circula(ra)m na cidade de Mariana ?
MG, a saber Voz de Marianna, O Germinal e O Cruzeiro. Assim, ao utilizarmos categorias
oriundas das teorias do discurso, procuraremos identificar formas dessa representa??o na m?dia
marianense. Porque a pesquisa aborda o tema do imagin?rio de mineiridade, julgamos
necess?rio tratar de tal fen?meno com o objetivo de suplementar a an?lise pretendida com
reflex?es que a auxiliar?o e igualmente trar?o contribui??es importantes. Procuraremos tamb?m
trazer exemplos de diferentes g?neros textuais/discursivos recorrentes nos jornais estudados
que refor?am o(s) discurso(s) de mineiridade e pautaremos nosso trabalho em um modelo de
an?lise discursiva representado por categorias como nome pr?prio como designador de
mem?ria, f?rmulas discursivas e destacabilidade nas formas de aforiza??o, sobreassevera??o e
particita??o, elementos bastante recorrentes nos jornais de Mariana ? MG analisados. Este
trabalho se inscreve em categorias de an?lise discursiva contribuindo, com isso, com estudos
dessa ?rea do conhecimento e sendo tamb?m uma possibilidade de reflex?o sobre a mem?ria,
compreens?o das representa??es de regionalismos, como ? o caso do imagin?rio s?ciodiscursivo
de mineiridade, e an?lise de como esse imagin?rio se faz presente nos jornais
marianenses, permanecendo como elemento caracter?stico da sociedade mineira.In Brazilian social, linguistic and cultural context, it is widely accepted that varied cultural traits
have their role/place in different regions of the country. In the Southeast region and, more
specifically, in the state of Minas Gerais, the phenomenon of ?mineiridade? (which are the
social traits usually attributed to people from Minas Gerais) is one of those Brazilian
characteristics that deserves special attention discursively speaking. Therefore, what we will
call in this thesis socio-discursive imaginary of ?mineiridade? can be captured from different
types of newspapers from Mariana-MG/Brazil and their recurrent genres. In this thesis, we will
look for elements of the socio-discursive imaginary of ?mineiridade? that can be identified in
the discursive construction of three newspapers from Mariana-MG/Brazil, named Voz de
Marianna, O Germinal and O Cruzeiro, that form part of the collection of UFOP/ICHS
managed by GEDEM - Group of Studies on Speech and Memory. Thus, when using categories
derived from discourse theories, we will try to identify types of this representation in Marian
media. As the research approaches the subject of the imaginary of ?mineiridade?, we consider
necessary to deal with such phenomenon with the purpose of supplementing the intended
analysis with reflections that will help it and bring to it important contributions. We will also
try to bring examples of discursive genres in the studied newspapers that reinforce the
discourse(s) of ?mineiridade?. We will guide our research to a discursive analysis model
represented by categories such as names and surnames as memory designators, discursive
formulas and detachability in the ways of aphorizing, surassertion, etc., elements that are
recurrent in the discursive construction of the newspapers analyzed. This thesis is part of
discursive analysis categories, contributing with studies of this area of knowledge and being a
possible meditation on the memory. It also is a kind of understanding of regionalisms
representations like the socio-discursive imaginary of ?mineiridade?, and it is an analysis of
how this imaginary is present in the Marian newspapers, remaining as a characteristic element
of Brazilian society
No disks around low-mass stars and brown dwarfs in the young sigma Orionis cluster?
We report on the analysis of 2MASS near-infrared data of a sample of low-mass
stars and brown dwarfs in the sigma Orionis cluster. Youth and cluster
membership have been spectroscopically confirmed using the Li I spectral line.
We find little evidence in the JHKs colour-colour diagram for near-infrared
excess emission for these cluster members. By comparison with model
expectations, at most 2 out of 34 stars show (H-K) colour consistent with a
near-infrared excess. This scarcity of near-infrared signatures of
circumstellar disks in the lower-mass and substellar regimes of this cluster
contrasts with findings in younger clusters, hinting at an age dependence of
the disk frequency. Taking into account the apparent cluster age, our result
supports the idea of a relatively fast (few Myr) disk dissipation and extends
this conclusion to the substellar regime. We also find some evidence that, in
this cluster, the disk frequency as measured by the Ks-band excess may be mass
dependent.Comment: 4 pages, 2 eps figures, accepted by Astronomy and Astrophysics
Letter
Accretion in Brown Dwarfs: an Infrared View
This paper presents a study of the accretion properties of 19 very low mass
objects (Mstar .01-0.1 Msun) in the regions Chamaeleon I and rho-Oph For 8
objects we obtained high resolution Halpha profiles and determined mass
accretion rate Macc and accretion luminosity Lacc. Pabeta is detected in
emission in 7 of the 10 rho-Oph objects, but only in one in Cha I. Using
objects for which we have both a determination of Lacc from Halpha and a Pabeta
detection, we show that the correlation between the Pabeta luminosity and
luminosity Lacc, found by Muzerolle et al. (1998) for T Tauri stars in Taurus,
extends to objects with mass approx 0.03 Msun; L(Pab) can be used to measure
Lacc also in the substellar regime. The results were less conclusive for
Brgamma, which was detected only in 2 objects, neither of which had an Halpha
estimate of Macc. Using the relation between L(Pab) and Lacc we determined the
accretion rate for all the objects in our sample (including those with no
Halpha spectrum), more than doubling the number of substellar objects with
known Macc. When plotted as a function of the mass of the central object
together with data from the literature, our results confirm the trend of lower
Macc for lower Mstar, although with a large spread. Some of the spread is
probably due to an age effect; our very young objects in rho-Oph have on
average an accretion rate at least one order of magnitude higher than objects
of similar mass in older regions. As a side product, we found that the width of
Halpha measured at 10% peak intensity is not only a qualitative indicator of
accretion, but can be used to obtain a quantitative estimate of Macc over a
large mass range, from T Tauri stars to brown dwarfs. Finally, we found that
some of our objects show evidence of mass-loss.Comment: 11 pages, 8 figures, A&A in pres
A multi-wavelength census of star formation activity in the young embedded cluster around Serpens/G3-G6
Aims. The aim of this paper is to characterise the star formation activity in
the poorly studied embedded cluster Serpens/G3-G6, located ~ 45' (3 pc) to the
south of the Serpens Cloud Core, and to determine the luminosity and mass
functions of its population of Young Stellar Objects (YSOs).
Methods. Multi-wavelength broadband photometry was obtained to sample the
near and mid-IR spectral energy distributions to separate YSOs from field stars
and classify the YSO evolutionary stage. ISOCAM mapping in the two filters LW2
(5-8.5 um) and LW3 (12-18 um) of a 19' x 16' field was combined with JHKs data
from 2MASS, Ks data from Arnica/NOT, and L' data from SIRCA/NOT. Continuum
emission at 1.3 mm (IRAM) and 3.6 cm (VLA) was mapped to study the cloud
structure and the coldest/youngest sources. Deep narrow band imaging at the
2.12 um S(1) line of H2 from NOTCam/NOT was obtained to search for signs of
bipolar outflows.
Results. We have strong evidence for a stellar population of 31 Class II
sources, 5 flat-spectrum sources, 5 Class I sources, and two Class 0 sources.
Our method does not sample the Class III sources. The cloud is composed of two
main dense clumps aligned along a ridge over ~ 0.5 pc plus a starless core
coinciding with absorption features seen in the ISOCAM maps. We find two
S-shaped bipolar collimated flows embedded in the NE clump, and propose the two
driving sources to be a Class 0 candidate (MMS3) and a double Class I (MMS2).
For the Class II population we find a best age of ~ 2 Myr and compatibility
with recent Initial Mass Functions (IMFs) by comparing the observed Class II
luminosity function (LF), which is complete to 0.08 L_sun, to various model LFs
with different star formation scenarios and input IMFs.Comment: 18 pages, 16 figures, 3 online tables, accepted by A&
Accretion properties of T Tauri stars in sigma Ori
Accretion disks around young stars evolve in time with time scales of few
million years. We present here a study of the accretion properties of a sample
of 35 stars in the ~3 million year old star-forming region sigma Ori. Of these,
31 are objects with evidence of disks, based on their IR excess emission. We
use near-IR hydrogen recombination lines (Pa_gamma) to measure their mass
accretion rate. We find that the accretion rates are significantly lower in
sigma Ori than in younger regions, such as rho-Oph, consistently with viscous
disk evolution. The He I 1.083 micron line is detected (either in absorption or
in emission) in 72% of the stars with disks, providing evidence of
accretion-powered activity also in very low accretors, where other accretion
indicators dissapear.Comment: Astronomy and Astrophysics, accepte
um instrumento para captar como a pandemia da COVID-19 afeta as pessoas que vivem com paralisia cerebral
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Tracing the origins of permitted emission lines in RU Lupi down to AU scales
Most of the observed emission lines and continuum excess from young accreting
low mass stars (Classical T Tauri stars -- CTTSs) take place in the star-disk
or inner disk region. These regions have a complex emission topology still
largely unknown. In this paper the magnetospheric accretion and inner wind
contributions to the observed permitted He and H near infrared (NIR) lines of
the bright southern CTTS RU Lupi are investigated for the first time. Previous
optical observations of RU Lupi showed a large H-alpha profile, due to the
emission from a wind in the line wings, and a micro-jet detected in forbidden
lines. We extend this analysis to NIR lines through seeing-limited high
spectral resolution spectra taken with VLT/ISAAC, and adaptive optics (AO)
aided narrow-band imaging and low spectral resolution spectroscopy with
VLT/NACO. Using spectro-astrometric analysis we investigate the presence of
extended emission down to very low spatial scales (a few AU). The HeI 10830
line presents a P Cygni profile whose absorption feature indicates the presence
of an inner stellar wind. Moreover the spectro-astrometric analysis evidences
the presence of an extended emission superimposed to the absorption feature and
likely coming from the micro-jet detected in the optical. On the contrary, the
origin of the Hydrogen Paschen and Brackett lines is difficult to address. We
tried tentatively to explain the observed line profiles and flux ratios with
both accretion and wind models showing the limits of both approaches. The lack
of spectro-astrometric signal indicates that the HI emission is either compact
or symmetric. Our analysis confirms the sensitivity of the HeI line to the
presence of faint extended emission regions in the close proximity of the star.Comment: 11 pages, 4 figures, accepted for publication on A&
Accretion and ejection properties of embedded protostars: the case of HH26, HH34 and HH46 IRS
We present the results of a near-IR spectroscopic analysis on 3 young
embedded sources (HH26IRS, HH34IRS and HH46IRS) belonging to different
star-forming regions and displaying well developed jet structures. The aim is
to investigate the source accretion and ejection properties and their
connection. We used VLT-ISAAC spectra (R~9000, H and K bands) to derive in a
self-consistent way parameters like the star luminosity, the accretion
luminosity and the mass accretion rate. Mass loss rates have also been
estimated from the analysis of different emission features. The spectra present
several emission lines but no photospheric features in absorption, indicating a
large veiling in H and K. We detected features commonly observed in jet-driving
sources (HI,[FeII],H_2,CO) and also a number of emission lines due to permitted
atomic transitions, like NaI and TiI. The NaI 2.2um doublet is observed along
with CO(2-0) band-head emission, indicating a common origin in an inner gaseous
disc heated by accretion. We find that accretion provides ~50% and ~80% of the
bolometric luminosity in HH26IRS and HH34IRS, as expected for accreting young
objects.Mass accretion and loss rates spanning 10^-8 - 10^-6 Msun/yr have been
measured. The derived Mloss/Macc is ~0.01 for HH26IRS and HH34IRS, and >0.1 for
HH46IRS, numbers that are in the range of values predicted by MHD jet-launching
models and found in the most active classical T Tauri stars. Comparison with
other similar studies seems to indicate that Class Is actually having
accretion- dominated luminosities are a limited number. Although the analysed
sample is small, we tentatively present some criteria to characterise such
sources. Studies like the one presented here but on larger samples of
candidates should be performed in order to test and refine these criteria.Comment: Accepted for A&A - 13 pages, 7 figure
Direct evidence of a sub-stellar companion around CT Cha
In our ongoing search for close and faint companions around T Tauri stars, we
found a very faint (Ks=14.9mag, Ks_0=14.4mag) object, just ~2.67" northwest of
the Chamaeleon star-forming region member CT Cha corresponding to a projected
separation of ~440AU at 165+/-30 pc. We show that CT Cha A and this faint
object form a common proper motion pair from data of the VLT Adaptive Optics
(AO) instrument NACO taken in February 2006 and March 2007 and that the
companion is by >=4 sigma significance not a stationary background object. Our
AO integral field spectroscopy with SINFONI in J, and H+K bands yields a
temperature of 2600+/-250K for the companion and an optical extinction of
A_V=5.2+/-0.8mag, when compared to spectra calculated from Drift-Phoenix model
atmospheres. We demonstrate the validity of the model fits by comparison to
several other well-known young sub-stellar objects. Relative flux calibration
of the bands was achieved using photometry from the NACO imaging data. We
conclude that the CT Cha companion is a very low-mass member of Chamaeleon and
very likely a physical companion to CT Cha, as the probability for a by chance
alignment is <=0.01. Due to a prominent Pa-Beta emission in the J-band,
accretion is probably still ongoing onto the CT Cha companion. From temperature
and luminosity (log(Lbol/Lsun)= -2.68+/-0.21), we derive a radius of
R=2.20+0.81-0.60 R_Jup. We find a consistent mass of M=17+/-6 MJup for the CT
Cha companion from both its luminosity and temperature when placed on
evolutionary tracks. Hence, the CT Cha companion is most likely a wide brown
dwarf companion or possibly even a planetary mass object.Comment: 10 pages, 11 figures, accepted for publication in A&
Accretion in rho-Ophiuchi brown dwarfs: infrared hydrogen line ratios
Mass accretion rate determinations are fundamental for an understanding of
the evolution of pre-main sequence star circumstellar disks. Magnetospheric
accretion models are used to derive values of the mass accretion rates in
objects of very different properties, from brown dwarfs to intermediate-mass
stars; we test the validity of these models in the brown dwarf regime, where
the stellar mass and luminosity, as well as the mass accretion rate, are much
lower than in T Tauri stars. We have measured simultaneously two infrared
hydrogen lines, Pab and Brg, in a sample of 16 objects in the star-forming
region rho-Oph. The sample inc ludes 7 very low mass objects and brown dwarfs
and 9 T Tauri stars. Brown dwarfs where both lines are detected have a ratio
Pab/Brg of ~2. Larger values, >=3.5, are only found among the T Tauri stars.
The low line ratios in brown dwarfs indicate that the lines cannot originate in
the column of gas accreting from the disk onto the star along the magnetic
field lines, and we suggest that they form instead in the shocked photosphere,
heated to temperatures of ~3500 K. If so, in analogy to veiling estimates in T
Tauri stars, the hydrogen infrared line fluxes may provide a reliable measure
of the accretion rate in brown dwarfs.Comment: 11 pages, 9 figures, accepted by A&
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