Eventi del Dottorato

Dottorato in Fisica

Journal Club Seminari 2022

07/04/2022   ore 14:15
AULA C - piano terra- V. della Vasca Navale n. 84

ore 14:15Vittoria Elvezia Gianolli
X-ray absorption properties in a type 1 quasar sample from the SDSS survey
Generally, optical and X-ray studies support the Unified Model, which was proposed in order to explain the variety of classes and sub-classes in which Active Galactic Nuclei (AGN) have been dived. According to it, AGNs present similar inner regions and are powered by the same central engine. While the phenomenological differences arise from geometrical effects associated with an optically-thick obscuring torus that surrounds the nuclear engine, and the relative position of the observer.
Despite the fact that the majority of AGNs classified as type 1 are unabsorbed and Type 2 AGNs are usually absorbed, the number of cases in which observations show disagreement between X-ray and optical classifications has increased.
In this context, we study a sample of optically classified as Type 1 quasars (QSO) that are obscured in the X-ray band. The main aims are to estimate the rate of QSO with obscured X-ray spectra and to investigate the physical origin of the discordant optical/X-ray properties.
ore 15:00Silvia Tosi
Characterization of evolved stars
During the AGB lifetime the stars eject into the surrounding environment gas, which on the chemical side is significantly altered with respect to the initial chemistry, and dust, formed in the cool and expanded circumstellar envelopes. Determining the mineralogy and the amount of dust is fundamental to establish their role as pollutants of the interstellar medium, and therefore the way in which they participate in the life cycle of the host galaxy. This is made difficult by the poor knowledge of some physical mechanisms however a valuable approach to infer information on the evolution of AGB stars is offered by the study of post-AGB stars. Indeed, main aspects of the evolution of these stars are well known, and the spectra of the latter sources can be more easily analyzed to derive the chemical composition and to characterize the dust in their surroundings. For this purpose, we have analyzed 10 post-AGB candidates from the LMC and the SMC. 


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