The nature of X-ray spectral variability in MCG-6-30-15

The flux-flux plot (FFP) method can provide model-independent clues regarding the X-ray variability of active galactic nuclei. To use it properly, the bin size of the light curves should be as short as possible, provided the average counts in the light curve bins are larger than $\sim 200$. We apply the FFP method to the 2013, simultaneous XMM-Newton and NuSTAR observations of the Seyfert galaxy MCG$-$6-30-15, in the 0.3-40 keV range. The FFPs above $\sim 1.6$ keV are well-described by a straight line. This result rules out spectral slope variations and the hypothesis of absorption driven variability. Our results are fully consistent with a power-law component varying in normalization only, with a spectral slope of $\sim 2$, plus a variable, relativistic reflection arising from the inner accretion disc around a rotating black hole. We also detect spectral components which remain constant over $\sim 4.5$ days (at least). At energies above $\sim 1.5$ keV, the stable component is consistent with reflection from distant, neutral material. The constant component at low energies is consistent with a blackbody spectrum of $kT_{\rm BB} \sim 100$ eV. The fluxes of these components are $\sim 10-20\%$ of the average continuum flux (in the respective bands). They should always be included in the models that are used to fit the spectrum of the source. The FFPs below 1.6 keV are non-linear, which could be due to the variable warm absorber in this source.Comment: 18 pages, 12 figures, 6 tables. Accepted for publication in MNRA

Testing the accuracy of reflection-based supermassive black hole spin measurements in AGN

X-ray reflection is a very powerful method to assess the spin of supermassive black holes (SMBHs) in active galactic nuclei (AGN), yet this technique is not universally accepted. Indeed, complex reprocessing (absorption, scattering) of the intrinsic spectra along the line of sight can mimic the relativistic effects on which the spin measure is based. In this work, we test the reliability of SMBH spin measurements that can currently be achieved through the simulations of high-quality XMM-Newton and NuSTAR spectra. Each member of our group simulated ten spectra with multiple components that are typically seen in AGN, such as warm and (partial-covering) neutral absorbers, relativistic and distant reflection, and thermal emission. The resulting spectra were blindly analysed by the other two members. Out of the 60 fits, 42 turn out to be physically accurate when compared to the input model. The SMBH spin is retrieved with success in 31 cases, some of which (9) are even found among formally inaccurate fits (although with looser constraints). We show that, at the high signal-to-noise ratio assumed in our simulations, neither the complexity of the multi-layer, partial-covering absorber nor the input value of the spin are the major drivers of our results. The height of the X-ray source (in a lamp-post geometry) instead plays a crucial role in recovering the spin. In particular, a success rate of 16 out of 16 is found among the accurate fits for a dimensionless spin parameter larger than 0.8 and a lamp-post height lower than five gravitational radii.Comment: 20 pages, 9 figures, 4 tables. Accepted for publication in A&

Variability of the soft X-ray excess in IRAS 13224-3809

We study the soft excess variability of the narrow line Seyfert 1 galaxy IRAS 13224-3809. We considered all five archival XMM-Newton observations, and we applied the 'flux-flux plot' (FFP) method. We found that the flux-flux plots were highly affected by the choice of the light curves' time bin size, most probably because of the fast and large amplitude variations, and the intrinsic non-linear flux--flux relations in this source. Therefore, we recommend that the smallest bin-size should be used in such cases. Hence, We constructed FFPs in 11 energy bands below 1.7 keV, and we considered the 1.7-3 keV band, as being representative of the primary emission. The FFPs are reasonably well fitted by a 'power-law plus a constant' model. We detected significant positive constants in three out of five observations. The best-fit slopes are flatter than unity at energies below $\sim 0.9$ keV, where the soft excess is strongest. This suggests the presence of intrinsic spectral variability. A power-law-like primary component, which is variable in flux and spectral slope (as $\Gamma\propto N_{\rm PL}^{0.1}$) and a soft-excess component, which varies with the primary continuum (as $F_{\rm excess}\propto F_{\rm primary}^{0.46}$), can broadly explain the FFPs. In fact, this can create positive `constants', even when a stable spectral component does not exist. Nevertheless, the possibility of a stable, soft--band constant component cannot be ruled out, but its contribution to the observed 0.2-1 keV band flux should be less than $\sim 15$ %. The model constants in the FFPs were consistent with zero in one observation, and negative at energies below 1 keV in another. It is hard to explain these results in the context of any spectral variability scenario, but they may signify the presence of a variable, warm absorber in the source.Comment: Accepted for publication in A&A, 10 pages, 7 figure

Étude Longitudinale de la Santé Mentale chez les Étudiants Primo-Inscrits de l’Université de Sfax

Intérêt et objectif de l’étude : Notre étude vise à évaluer la santé psychologique chez les étudiants primo-inscrits de l’université de Sfax et d’identifier certains facteurs psychosociaux qui peuvent impacter leur santé. Méthodes : Il s’agit d’une étude longitudinale qui s’est déroulée sur deux temps. Notre échantillon est composé de 344 étudiants primo-inscrits dans des filières scientifiques et littéraires qui ont été sollicités au début et à la fin de l’année universitaire 2017-2018. Seulement 252 étudiants ont participé à la deuxième étape de la recherche. Des échelles ont été traduites en arabe pour répondre aux objectifs de la recherche. Résultats : Les données indiquent que 42.7% des étudiants interrogés présentent des signes de détresse psychologique. Nos résultats révèlent que plusieurs facteurs sont associés à cette détresse d’une manière statistiquement significative, à savoir la satisfaction des conditions socio-économiques, le choix de la filière (subi ou délibéré) et la satisfaction du soutien social et des conditions de l’hébergement au campus universitaire. Certains facteurs transactionnels sont corrélés d’une manière significative à notre variable dépendante «la santé psychologique », à savoir le stress perçu et les stratégies d’ajustement et avec certains facteurs de personnalité comme l’estime de soi, le névrosisme et l’espoir. L’analyse de régression multiple indique que l’estime de soi et le névrosisme expliquent, respectivement à 31% et à 7%, la variance santé psychologique. Les résultats de l’étude longitudinale montrent l’amélioration générale de l’état de santé des étudiants interrogés lors du deuxième moment de l’étude avec un impact statistiquement significatif des facteurs de l’estime de soi et du coping centré sur la résolution des problèmes et l’espoir Conclusion :Un travail d’accompagnement psychologique centré sur les facteurs de protection s’avère plus que nécessaire pour éviter le basculement de cette détresse dans des troubles psychiatriques.   Interest and objective of the study: Our study aims to assess the psychological health of first-time students enrolled at the University of Sfax and to identify certain psychosocial factors that can impact their health. Methods: This is a longitudinal study that took place over two periods. Our sample is made up of 344 first-time students enrolled in science and literature courses who were contacted at the beginning and end of the 2017-2018 academic year. Only 252 students participated in the second stage of the research. Scales were translated into Arabic to meet the research objectives. Results: The data indicate that 42.7% of the students surveyed show signs of psychological distress. Our results reveal that several factors are associated with this distress in a statistically significant way, namely the satisfaction of socio-economic conditions, the choice of the sector (submitted or deliberate) and the satisfaction of social support and the conditions of the school. accommodation at the university campus. Some transactional factors are significantly correlated with our dependent variable “psychological health”, namely perceived stress and coping strategies and with some personality factors such as self-esteem, neuroticism and hope. . Multiple regression analysis indicates that self-esteem and neuroticism explain, respectively, 31% and 7%, of the psychological health variance. The results of the longitudinal study show the general improvement in the state of health of the students questioned during the second moment of the study with a statistically significant impact of the factors of self-esteem and coping centered on the resolution of problems. problems and hope. Conclusion: Psychological support work centered on protective factors is more than necessary to avoid the tipping of this distress into psychiatric disorders

Étude Longitudinale de la Santé Mentale chez les Étudiants Primo-Inscrits de l’Université de Sfax

Intérêt et objectif de l’étude : Notre étude vise à évaluer la santé psychologique chez les étudiants primo-inscrits de l’université de Sfax et d’identifier certains facteurs psychosociaux qui peuvent impacter leur santé. Méthodes : Il s’agit d’une étude longitudinale qui s’est déroulée sur deux temps. Notre échantillon est composé de 344 étudiants primo-inscrits dans des filières scientifiques et littéraires qui ont été sollicités au début et à la fin de l’année universitaire 2017-2018. Seulement 252 étudiants ont participé à la deuxième étape de la recherche. Des échelles ont été traduites en arabe pour répondre aux objectifs de la recherche. Résultats : Les données indiquent que 42.7% des étudiants interrogés présentent des signes de détresse psychologique. Nos résultats révèlent que plusieurs facteurs sont associés à cette détresse d’une manière statistiquement significative, à savoir la satisfaction des conditions socio-économiques, le choix de la filière (subi ou délibéré) et la satisfaction du soutien social et des conditions de l’hébergement au campus universitaire. Certains facteurs transactionnels sont corrélés d’une manière significative à notre variable dépendante «la santé psychologique », à savoir le stress perçu et les stratégies d’ajustement et avec certains facteurs de personnalité comme l’estime de soi, le névrosisme et l’espoir. L’analyse de régression multiple indique que l’estime de soi et le névrosisme expliquent, respectivement à 31% et à 7%, la variance santé psychologique. Les résultats de l’étude longitudinale montrent l’amélioration générale de l’état de santé des étudiants interrogés lors du deuxième moment de l’étude avec un impact statistiquement significatif des facteurs de l’estime de soi et du coping centré sur la résolution des problèmes et l’espoir Conclusion :Un travail d’accompagnement psychologique centré sur les facteurs de protection s’avère plus que nécessaire pour éviter le basculement de cette détresse dans des troubles psychiatriques.   Interest and objective of the study: Our study aims to assess the psychological health of first-time students enrolled at the University of Sfax and to identify certain psychosocial factors that can impact their health. Methods: This is a longitudinal study that took place over two periods. Our sample is made up of 344 first-time students enrolled in science and literature courses who were contacted at the beginning and end of the 2017-2018 academic year. Only 252 students participated in the second stage of the research. Scales were translated into Arabic to meet the research objectives. Results: The data indicate that 42.7% of the students surveyed show signs of psychological distress. Our results reveal that several factors are associated with this distress in a statistically significant way, namely the satisfaction of socio-economic conditions, the choice of the sector (submitted or deliberate) and the satisfaction of social support and the conditions of the school. accommodation at the university campus. Some transactional factors are significantly correlated with our dependent variable “psychological health”, namely perceived stress and coping strategies and with some personality factors such as self-esteem, neuroticism and hope. . Multiple regression analysis indicates that self-esteem and neuroticism explain, respectively, 31% and 7%, of the psychological health variance. The results of the longitudinal study show the general improvement in the state of health of the students questioned during the second moment of the study with a statistically significant impact of the factors of self-esteem and coping centered on the resolution of problems. problems and hope. Conclusion: Psychological support work centered on protective factors is more than necessary to avoid the tipping of this distress into psychiatric disorders