Dust-to-gas ratio resurgence in circumstellar disks due to the formation of giant planets: the case of HD 163296

The amount of dust present in circumstellar disks is expected to steadily decrease with age due to the growth from micron-sized particles to planetesimals and planets. Mature circumstellar disks, however, can be observed to contain significant amounts of dust and possess high dust-to-gas ratios. Using HD 163296 as our case study, we explore how the formation of giant planets in disks can create the conditions for collisionally rejuvenating the dust population, halting or reversing the expected trend. We combine N-body simulations with statistical methods and impact scaling laws to estimate the dynamical and collisional excitation of the planetesimals due to the formation of HD 163296's giant planets. We show that this process creates a violent collisional environment across the disk that can inject collisionally produced second-generation dust into it, significantly contributing to the observed dust-to-gas ratio. The spatial distribution of the dust production can explain the observed local enrichments in HD 163296's inner regions. The results obtained for HD 163296 can be extended to any disk with embedded forming giant planets and may indicate a common evolutionary stage in the life of such circumstellar disks. Furthermore, the dynamical excitation of the planetesimals could result in the release of transient, non-equilibrium gas species like H2O, CO2, NH3 and CO in the disk due to ice sublimation during impacts and, due to the excited planetesimals being supersonic with respect to the gas, could produce bow shocks in the latter that could heat it and cause a broadening of its emission lines.Comment: 18 pages, 9 figures, 2 tables. Accepted for publication on The Astrophysical Journa

OCCUPATIONAL STRESS, DEPRESSION AND JOB SATISFACTION OF SPECIAL EDUCATION TEACHERS

Objective: The purpose of this study is to investigate occupational stress, depression and anxiety of primary education special education teachers, as well as levels of job satisfaction and how these are related to a number of demographic variables. Method: One hundred (100) special education teachers (39 males & 61 females) from the Regional Directorate of Attica took part in this study. Four self-report questionnaires were administered to the participants, i.e., the Perceived Stress Scale-14, the Depression Anxiety Stress-21, the Employee Satisfaction Inventory scale, and the Job Satisfaction Scale. A short health status questionnaire was also administered to the participants with questions related to the demographic data of the participants (gender, age, etc.), questions related to the work of the participants (level of education, years of service, etc.), as well as questions related to participants' health (e.g. "How good is your health?"). The statistical package SPSSv.21 was used for statistical analysis of the data. A variety of descriptive measures (frequency, percentages, mean, etc.) were used to describe the results. Pearson's linear correlation coefficient r was used to test the correlation between two variables. Additionally, the PROCESS macro (version 3) for SPSS was used in order to conduct moderation analysis. Results: The results showed that participants reported moderate levels of perceived stress, anxiety and depression, as well as levels of job satisfaction. Negative correlations between perceived stress and job satisfaction and between depression and job satisfaction were observed. Regarding stress and health status, elevated levels of stress were related to poorer health. Furthermore, correlations between stress, anxiety and depression with job satisfaction appeared to be influenced by gender, and in most cases the correlations had different directions between males and females. Therefore, occupational stress, depression and anxiety can be considered as predictors of the health status of special education teachers, as high levels of occupational stress and anxiety are strongly related to low levels of self-reported health-well-being, satisfaction. Conclusions: The results of this study highlight the need to explore the mental health of special education needs teachers that are associated with specific physical health issues so that measures can be taken for the development of prevention programs and personal strategies in order to cope with stress, anxiety and depression in teachers. Article visualizations

<i>Herschel</i> observations of B1-bS and B1-bN: two first hydrostatic core candidates in the Perseus star-forming cloud

We report far-infrared Herschel observations obtained between 70 μm and 500 μm of two star-forming dusty condensations, [HKM99] B1-bS and [HKM99] B1-bN, in the B1 region of the Perseus star-forming cloud. In the western part of the Perseus cloud, B1-bS is the only source detected in all six PACS and SPIRE photometric bands, but it is not visible in the Spitzer map at 24 μm. B1-bN is clearly detected between 100 μm and 250 μm. We have fitted the spectral energy distributions of these sources to derive their physical properties, and find that a simple greybody model fails to reproduce the observed spectral energy distributions. At least a two-component model is required, consisting of a central source surrounded by a dusty envelope. The properties derived from the fit, however, suggest that the central source is not a Class 0 object. We then conclude that while B1-bS and B1-bN appear to be more evolved than a pre-stellar core, the best-fit models suggest that their central objects are younger than a Class 0 source. Hence, they may be good candidates to be examples of the first hydrostatic core phase. The projected distance between B1-bS and B1-bN is a few Jeans lengths. If their physical separation is close to this value, this pair would allow studying the mutual interactions between two forming stars at a very early stage of their evolution

The Herschel view of the on-going star formation in the Vela-C molecular cloud

As part of the Herschel guaranteed time key program 'HOBYS', we present the photometric survey of the star forming region Vela-C, one of the nearest sites of low-to-high-mass star formation in the Galactic plane. Vela-C has been observed with PACS and SPIRE in parallel mode between 70 um and 500 um over an area of about 3 square degrees. A photometric catalogue has been extracted from the detections in each band, using a threshold of 5 sigma over the local background. Out of this catalogue we have selected a robust sub-sample of 268 sources, of which 75% are cloud clumps and 25% are cores. Their Spectral Energy Distributions (SEDs) have been fitted with a modified black body function. We classify 48 sources as protostellar and 218 as starless. For two further sources, we do not provide a secure classification, but suggest they are Class 0 protostars. From SED fitting we have derived key physical parameters. Protostellar sources are in general warmer and more compact than starless sources. Both these evidences can be ascribed to the presence of an internal source(s) of moderate heating, which also causes a temperature gradient and hence a more peaked intensity distribution. Moreover, the reduced dimensions of protostellar sources may indicate that they will not fragment further. A virial analysis of the starless sources gives an upper limit of 90% for the sources gravitationally bound and therefore prestellar. We fit a power law N(logM) prop M^-1.1 to the linear portion of the mass distribution of prestellar sources. This is in between that typical of CO clumps and those of cores in nearby star-forming regions. We interpret this as a result of the inhomogeneity of our sample, which is composed of comparable fractions of clumps and cores.Comment: 9 pages, 7 figures, accepted by A&

Cultural universality and specificity of student engagement in school: The results of an international study from 12 countries

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Orbital obliquity of the young planet TOI-5398 b and the evolutionary history of the system

Multi-planet systems exhibit remarkable architectural diversity. However, short-period giant planets are typically isolated. Compact systems like TOI-5398, with an outer close-orbit giant and an inner small-size planet, are rare among systems containing short-period giants. TOI-5398's unusual architecture coupled with its young age (650 +/- 150 Myr) make it a promising system for measuring the original obliquity between the orbital axis of the giant and the stellar spin axis in order to gain insight into its formation and orbital migration. We collected in-transit (plus suitable off-transit) observations of TOI-5398 b with HARPS-N at TNG on March 25, 2023, obtaining high-precision radial velocity time series that allowed us to measure the Rossiter-McLaughlin (RM) effect. By modelling the RM effect, we obtained a sky-projected obliquity of lambda = 3.0(-4.2)(+6.8) deg for TOI-5398 b, consistent with the planet being aligned. With knowledge of the stellar rotation period, we estimated the true 3D obliquity, finding psi = (13.2 +/- 8.2) deg. Based on theoretical considerations, the orientation we measure is unaffected by tidal effects, offering a direct diagnostic for understanding the formation path of this planetary system. The orbital characteristics of TOI-5398, with its compact architecture, eccentricity consistent with circular orbits, and hints of orbital alignment, appear more compatible with the disc-driven migration scenario. TOI-5398, with its relative youth (compared with similar compact systems) and exceptional suitability for transmission spectroscopy studies, presents an outstanding opportunity to establish a benchmark for exploring the disc-driven migration model

Missing Migrants in the Mediterranean : Addressing the Humanitarian Crisis Summary report

The Mediterranean Missing research project has sought to understand both the impact on families of having a relative missing in migration, and the law, policy and practice around the identification of bodies of dead migrants in Italy and Greece. Interviews with families of missing migrants from five countries confirmed the huge impact of not knowing the fate of loved ones, with families tortured by ambiguity and suffering a range of emotional and psychological consequences. In Lesbos, Greece, and Sicily, Italy, interviews with authorities, civil society and others confirm the presence of a policy vacuum around the issue of the missing, despite the duties on states imposed by human rights law. Investigation of deaths is inadequate, with effective post-mortem data collection and management challenged by the huge numbers of migrants , in some cases sufficiently to compromise future identification. In both Greece and Italy, response is characterised by a policy vacuum, with a large number of agencies with overlapping mandates lacking coordination. Whilst in Italy a dedicated Commission and its partners have demonstrated what can be done with appropriate resources, there is a need to ensure that all the dead benefit from such an approach. A constraint in both contexts remains the lack of outreach to families of the missing, who can provide ante-mortem data to enable identification, and who should anyway be at the centre of all efforts to address the issue and identify the dead