261 research outputs found
Le soutien parental offert par les membres du réseau social : le point de vue des mères en situation de vulnérabilité
Cet article examine le soutien parental présent dans le réseau social des mères en contexte de vulnérabilité : mères ayant un enfant âgé entre 2 à 6 ans et cumulant au moins deux des facteurs de risque retenus (pauvreté, sous-scolarisation et jeune âge à la naissance du premier enfant). Les données recueillies par le biais d’entrevues semi-structurées effectuées auprès du groupe de mères considérées à risque (groupe cible, n = 49) ont été comparées à celles obtenues auprès d’un groupe de mères jugées peu à risque (groupe normatif, n = 43). Les résultats rapportent le point de vue des mères participantes concernant les membres de leur réseau social (par exemple, les personnes perçues comme étant les plus aidantes ou les plus nuisibles dans l’exercice de leur rôle parental). Les formes de soutien ou de stress attribuées à certaines figures perçues comme centrales par les mères (grands-mères maternelles, conjoints et ex-conjoints) sont également décrites. Certaines pistes d’intervention prenant appui sur les ressources du réseau informel sont suggérées.The present study focuses on informal social networks and the people who give parental support to at-risk mothers (i.e., mothers who display at least two of the following risk factors : low SES, low education, and under 21 years at the birth of their first child). A sample of 49 such mothers, who had children between the ages of 2 and 6 years, participated in semi structured interviews. The group was then matched with a group of low risk mothers (n = 43). Results present mothers’ perspectives on the people in their social network they see as being most helpful or most stressful, as far as parenting is concerned. They also describe the roles played by key members of their immediate environment (maternal grandmothers, spouse or ex-spouse). Practical guidelines towards a network-oriented approach in parental support are outlined.Este artículo examina el apoyo parental presente en la red social de madres en un contexto de vulnerabilidad: madres con un niño de entre 2 y 6 años y con al menos dos de los factores de riesgo retenidos (pobreza, poca escolaridad y juventud al nacer el primer hijo). Los datos recopilados por medio de entrevistas semiestructuradas realizadas en un grupo de madres consideradas en riesgo (grupo meta, n = 49) fueron comparados con aquellos obtenidos de un grupo de madres consideradas como en poco riesgo (grupo normativo, n = 43). Los resultados reportan el punto de vista de las madres participantes acerca de los miembros de su red social (por ejemplo, las personas percibidas como de más ayuda o las más nocivas en el ejercicio de su papel parental). También se describen las formas de apoyo o de estrés que se atribuyen a ciertas figuras percibidas como centrales por las madres (abuelas maternas, parejas y ex-parejas). Se sugieren ciertas pistas de intervención que se apoyan en los recursos de la red informal.Este artigo examina o apoio parental presente na rede social das mães em contexto de vulnerabilidade: mães que têm um filho com idade entre 2 e 6 anos e que acumulam, pelo menos, dois dos fatores de risco (pobreza, baixa escolaridade, idade jovem no nascimento do primeiro filho). Os dados recolhidos através de entrevistas semi-estruturadas realizadas junto ao grupo de mulheres consideradas a risco (grupo-alvo, n=49) foram comparadas aos obtidos junto a um grupo de mães julgadas a pouco risco (grupo normativo, n=43). Os resultados revelam o ponto de vista das mães participantes com respeito aos membros de sua rede social (por exemplo, as pessoas vistas como sendo as que mais ajudam ou as que mais atrapalham no exercício de seu papel materno). As formas de apoio ou de estresse atribuídas a algumas figuras vistas como centrais pelas mães (avós maternas, esposos, ex-maridos) são igualmente descritas. São sugeridas algumas pistas de intervenção com base nos recursos de rede informal
Anomalies in low-energy Gamma-Ray Burst spectra with the Fermi Gamma-Ray Burst Monitor
A Band function has become the standard spectral function used to describe
the prompt emission spectra of gamma-ray bursts (GRBs). However, deviations
from this function have previously been observed in GRBs detected by BATSE and
in individual GRBs from the \textit{Fermi} era. We present a systematic and
rigorous search for spectral deviations from a Band function at low energies in
a sample of the first two years of high fluence, long bursts detected by the
\textit{Fermi} Gamma-Ray Burst Monitor (GBM). The sample contains 45 bursts
with a fluence greater than 2 erg / cm (10 - 1000 keV). An
extrapolated fit method is used to search for low-energy spectral anomalies,
whereby a Band function is fit above a variable low-energy threshold and then
the best fit function is extrapolated to lower energy data. Deviations are
quantified by examining residuals derived from the extrapolated function and
the data and their significance is determined via comprehensive simulations
which account for the instrument response. This method was employed for both
time-integrated burst spectra and time-resolved bins defined by a signal to
noise ratio of 25 and 50 . Significant deviations are evident
in 3 bursts (GRB\,081215A, GRB\,090424 and GRB\,090902B) in the time-integrated
sample ( 7%) and 5 bursts (GRB\,090323, GRB\,090424, GRB\,090820,
GRB\,090902B and GRB\,090926A) in the time-resolved sample ( 11%).} The
advantage of the systematic, blind search analysis is that it can demonstrate
the requirement for an additional spectral component without any prior
knowledge of the nature of that extra component. Deviations are found in a
large fraction of high fluence GRBs; fainter GRBs may not have sufficient
statistics for deviations to be found using this method
Detection of a Thermal Spectral Component in the Prompt Emission of GRB 100724B
Observations of GRB 100724B with the Fermi Gamma-Ray Burst Monitor (GBM) find
that the spectrum is dominated by the typical Band functional form, which is
usually taken to represent a non-thermal emission component, but also includes
a statistically highly significant thermal spectral contribution. The
simultaneous observation of the thermal and non-thermal components allows us to
confidently identify the two emission components. The fact that these seem to
vary independently favors the idea that the thermal component is of
photospheric origin while the dominant non-thermal emission occurs at larger
radii. Our results imply either a very high efficiency for the non-thermal
process, or a very small size of the region at the base of the flow, both quite
challenging for the standard fireball model. These problems are resolved if the
jet is initially highly magnetized and has a substantial Poynting flux.Comment: 6 pages, 3 figures, 1 table, Accepted for publication in the
Astrophysical Journal Letters November, 23 2010 (Submitted October, 20 2010
Temporal Deconvolution study of Long and Short Gamma-Ray Burst Light curves
The light curves of Gamma-Ray Bursts (GRBs) are believed to result from
internal shocks reflecting the activity of the GRB central engine. Their
temporal deconvolution can reveal potential differences in the properties of
the central engines in the two populations of GRBs which are believed to
originate from the deaths of massive stars (long) and from mergers of compact
objects (short). We present here the results of the temporal analysis of 42
GRBs detected with the Gamma-ray Burst Monitor onboard the Fermi Gamma-ray
Space Telescope. We deconvolved the profiles into pulses, which we fit with
lognormal functions. The distributions of the pulse shape parameters and
intervals between neighboring pulses are distinct for both burst types and also
fit with lognormal functions. We have studied the evolution of these parameters
in different energy bands and found that they differ between long and short
bursts. We discuss the implications of the differences in the temporal
properties of long and short bursts within the framework of the internal shock
model for GRB prompt emission.Comment: 38 pages, 11 figure
The Fermi GBM Gamma-Ray Burst Spectral Catalog: Four Years Of Data
In this catalog we present the updated set of spectral analyses of GRBs
detected by the Fermi Gamma-Ray Burst Monitor (GBM) during its first four years
of operation. It contains two types of spectra, time-integrated spectral fits
and spectral fits at the brightest time bin, from 943 triggered GRBs. Four
different spectral models were fitted to the data, resulting in a compendium of
more than 7500 spectra. The analysis was performed similarly, but not
identically to Goldstein et al. 2012. All 487 GRBs from the first two years
have been re-fitted using the same methodology as that of the 456 GRBs in years
three and four. We describe, in detail, our procedure and criteria for the
analysis, and present the results in the form of parameter distributions both
for the observer-frame and rest-frame quantities. The data files containing the
complete results are available from the High-Energy Astrophysics Science
Archive Research Center (HEASARC).Comment: Accepted for publication in ApJ
First-year Results of Broadband Spectroscopy of the Brightest Fermi-GBM Gamma-Ray Bursts
We present here our results of the temporal and spectral analysis of a sample
of 52 bright and hard gamma-ray bursts (GRBs) observed with the Fermi Gamma-ray
Burst Monitor (GBM) during its first year of operation (July 2008-July 2009).
Our sample was selected from a total of 253 GBM GRBs based on each event peak
count rate measured between 0.2 and 40MeV. The final sample comprised 34 long
and 18 short GRBs. These numbers show that the GBM sample contains a much
larger fraction of short GRBs, than the CGRO/BATSE data set, which we explain
as the result of our (different) selection criteria and the improved GBM
trigger algorithms, which favor collection of short, bright GRBs over BATSE. A
first by-product of our selection methodology is the determination of a
detection threshold from the GBM data alone, above which GRBs most likely will
be detected in the MeV/GeV range with the Large Area Telescope (LAT) onboard
Fermi. This predictor will be very useful for future multiwavelength GRB follow
ups with ground and space based observatories. Further we have estimated the
burst durations up to 10MeV and for the first time expanded the duration-energy
relationship in the GRB light curves to high energies. We confirm that GRB
durations decline with energy as a power law with index approximately -0.4, as
was found earlier with the BATSE data and we also notice evidence of a possible
cutoff or break at higher energies. Finally, we performed time-integrated
spectral analysis of all 52 bursts and compared their spectral parameters with
those obtained with the larger data sample of the BATSE data. We find that the
two parameter data sets are similar and confirm that short GRBs are in general
harder than longer ones.Comment: 40 pages, 11 figures, 3 tables, Submitted to Ap
Time-Resolved Spectroscopy of the 3 Brightest and Hardest Short Gamma-Ray Bursts Observed with the FGST Gamma-Ray Burst Monitor
From July 2008 to October 2009, the Gamma-ray Burst Monitor (GBM) on board
the Fermi Gamma-ray Space Telescope (FGST) has detected 320 Gamma-Ray Bursts
(GRBs). About 20% of these events are classified as short based on their T90
duration below 2 s. We present here for the first time time-resolved
spectroscopy at timescales as short as 2 ms for the three brightest short GRBs
observed with GBM. The time-integrated spectra of the events deviate from the
Band function, indicating the existence of an additional spectral component,
which can be fit by a power-law with index ~-1.5. The time-integrated Epeak
values exceed 2 MeV for two of the bursts, and are well above the values
observed in the brightest long GRBs. Their Epeak values and their low-energy
power-law indices ({\alpha}) confirm that short GRBs are harder than long ones.
We find that short GRBs are very similar to long ones, but with light curves
contracted in time and with harder spectra stretched towards higher energies.
In our time-resolved spectroscopy analysis, we find that the Epeak values range
from a few tens of keV up to more than 6 MeV. In general, the hardness
evolutions during the bursts follows their flux/intensity variations, similar
to long bursts. However, we do not always see the Epeak leading the light-curve
rises, and we confirm the zero/short average light-curve spectral lag below 1
MeV, already established for short GRBs. We also find that the time-resolved
low-energy power-law indices of the Band function mostly violate the limits
imposed by the synchrotron models for both slow and fast electron cooling and
may require additional emission processes to explain the data. Finally, we
interpreted these observations in the context of the current existing models
and emission mechanisms for the prompt emission of GRBs.Comment: 14 pages, 10 figures, 9 tables, Accepted for publication in the
Astrophysical Journal September, 23 2010 (Submitted May, 16 2010)
Corrections: 1 reference updated, figure 10 captio
Identifications of Five INTEGRAL Sources via Optical Spectroscopy
The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) is discovering
hundreds of new hard X-ray sources, many of which remain unidentified. We
report on optical spectroscopy of five such sources for which X-ray
observations at lower energies (~0.5-10 keV) and higher angular resolutions
than INTEGRAL have allowed for unique optical counterparts to be located. We
find that IGR J16426+6536 and IGR J22292+6647 are Type 1 Seyfert active
galactic nuclei (with IGR J16426+6536 further classified as a Seyfert 1.5)
which have redshifts of z=0.323 and z=0.113, respectively. IGR J18308-1232 is
identified as a cataclysmic variable (CV), and we confirm a previous
identification of IGR J19267+1325 as a magnetic CV. IGR J18214-1318 is
identified as an obscured high mass X-ray binary (HMXB), which are systems
thought to have a compact object embedded in the stellar wind of a massive
star. We combine Chandra fluxes with distances based on the optical
observations to calculate X-ray luminosities of the HMXB and CVs, finding
L_(0.3-10 keV)=5e36 erg s^-1 for IGR J18214-1318, L_(0.3-10 keV)=1.3e32 erg
s^-1 for IGR J18308-1232, and L_(0.3-10 keV)=6.7e32 erg s^-1 for IGR
J19267+1325.Comment: 8 pages, 5 figures, accepted for publication by Ap
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