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$\times10^{-5}$ erg / cm$^{2}$ (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 $\sigma$ and 50 $\sigma$. Significant deviations are evident in 3 bursts (GRB\,081215A, GRB\,090424 and GRB\,090902B) in the time-integrated sample ($\sim$ 7%) and 5 bursts (GRB\,090323, GRB\,090424, GRB\,090820, GRB\,090902B and GRB\,090926A) in the time-resolved sample ($\sim$ 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

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