47 research outputs found
Accretion and outflow-related X-rays in T Tauri stars
We report on accretion- and outflow-related X-rays from T Tauri stars, based on results from the "XMM-Newton Extended Survey of the Taurus Molecular Cloud.â X-rays potentially form in shocks of accretion streams near the stellar surface, although we hypothesize that direct interactions between the streams and magnetic coronae may occur as well. We report on the discovery of a "soft excessâ in accreting T Tauri stars supporting these scenarios. We further discuss a new type of X-ray source in jet-driving T Tauri stars. It shows a strongly absorbed coronal component and a very soft, weakly absorbed component probably related to shocks in microjets. The excessive coronal absorption points to dust-depletion in the accretion stream
Probing Episodic Accretion in Very Low Luminosity Objects
Episodic accretion has been proposed as a solution to the long-standing luminosity problem in star formation; however, the process remains poorly understood. We present observations of line emission from N2H+ and CO isotopologues using the Atacama Large Millimeter/submillimeter Array (ALMA) in the envelopes of eight very low luminosity objects (VeLLOs). In five of the sources the spatial distribution of emission from N2H+ and CO isotopologues shows a clear anticorrelation. It is proposed that this is tracing the CO snow line in the envelopes: N2H+ emission is depleted toward the center of these sources, in contrast to the CO isotopologue emission, which exhibits a peak. The positions of the CO snow lines traced by the N2H+ emission are located at much larger radii than those calculated using the current luminosities of the central sources. This implies that these five sources have experienced a recent accretion burst because the CO snow line would have been pushed outward during the burst because of the increased luminosity of the central star. The N2H+ and CO isotopologue emission from DCE161, one of the other three sources, is most likely tracing a transition disk at a later evolutionary stage. Excluding DCE161, five out of seven sources (i.e., ~70%) show signatures of a recent accretion burst. This fraction is larger than that of the Class 0/I sources studied by JĂžrgensen et al. and Frimann et al., suggesting that the interval between accretion episodes in VeLLOs is shorter than that in Class 0/I sources
Justificação pĂșblica: a função da ideia de estrutura bĂĄsica da sociedade em Rawls
A linguagem do respeito: a experiĂȘncia brasileira e o sentido da cidadania nas democracias modernas
Addressing the rise of inequalities: how relevant is Rawlsâs critique of welfare state capitalism?
Pluralisme religieux et égalité : une critique de la laïcit
Que veut dire ĂȘtre pluraliste dans le nouveau contexte religieux auquel la France est confrontĂ©e comme la plupart des ex-puissances coloniales ? Le pluralisme est une rĂ©alitĂ© complexe. Il dĂ©signe Ă la fois lâexistence dâune diversitĂ© croissante de religions et de croyances dans le contexte des sociĂ©tĂ©s « ouvertes » contemporaines, un « fait » social donc, mais aussi un idĂ©al politique de plus en plus caractĂ©ristique des dĂ©mocraties avancĂ©es, qui veille Ă ce que la diversitĂ© religieuse ne renf..
Lâautonomie doctrinale des principes de justice: force ou faiblesse de la thĂ©orie rawlsienne?
How consistent is Rawlsâs theory of justice in view of his later political turn? For some commentators, abandoning the search for a Kantian foundation of the principles of justice in favour of a purely âpoliticalâ liberalism is too high a price to pay for gaining a wide but limited consensus in democratic societies that are in effect characterized by insoluble conflicts of values. The âinconvenient truthâ that Rawls discovers is that âthere can be no overlapping consensus on a Kantian conception of persons or justice as fairness more broadlyâ writes Robert Taylor (2011, p. 276), but that without such a foundation, the moral strength of his theory would be diluted. In this paper, I answer such criticisms and show that, far from leading to relativism, the demands of the theory of justiceâs doctrinal autonomy and independence from any substantive conceptions of the Good correspond to the very meaning the democratic ideal has for Rawls: respect for the personâs moral autonomy and rejection of âthe centuries-long practice of intolerance as a condition of social order and stabilityâ (J. Rawls, Political Liberalism, xxvii). However, is not such an ideal unrealistic? Is not such a trust in citizensâs autonomy, in their capacity to isolate their allegiance to public principles of justice from that to their nonpublic moral doctrines, a source of weakness for democracies instead of stability, as Rawls claims? Is the ambition of doctrinal autonomy a strength or a weakness of the Rawlsian theory