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Speaker: Giada Genua

Titolo: Tutela, conservazione e restauro dei beni librari del fondo Piazzi, presso la Specola Universitaria di Palermo: primi risultati di un progetto di ricerca

Abstract:

Nel seminario verranno presentati i primi risultati del lavoro di conservazione e restauro attualmente in corso sui libri del fondo Piazzi, cioè la collezione libraria di proprietà del fondatore dell’Osservatorio Astronomico, lasciati in eredità all’istituto alla sua morte; la collezione costituisce dunque il nucleo originario della biblioteca dell’Osservatorio.
Verranno descritte le altre attività di ricerca svolte in parallelo: lo sviluppo di un database relazionale dettagliato sui libri del Fondo, utile per la condivisione e l’implementazione di futuri studi sull’argomento e lo studio sulle carte decorate presenti sulle legature di molti dei libri della collezione. Si discuteranno inoltre le tracce presenti in biblioteca delle interessanti relazioni di Piazzi con la Stamperia Reale, un’altra istituzione creata sul finire del ‘700 come parte del rinnovamento culturale e scientifico di Palermo.
Questa attività fa parte di un più ampio progetto mirato allo studio della fondazione e delle prime fasi di vita dell’Osservatorio Astronomico.

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Speaker: Emanuele Greco (UNIPA)

Titolo: Unveiling pure-metal ejecta X-ray emission in supernova remnants through their radiative recombination

Abstract:

Spectral analysis of X-ray emission from ejecta in supernova remnants (SNRs) is hampered by the low spectral resolution of CCD detectors, which typically creates a degeneracy between the best-fit values of chemical abundances and the plasma emission measure. The combined contribution of shocked ambient medium and ejecta to the emerging X-ray emission further complicates the determination of the ejecta mass and chemical composition. This degeneracy leads to big uncertainties in mass estimates and can introduce a bias in the comparison between the ejecta chemical composition derived from the observations and the yields predicted by explosive nucleosynthesis models. We explore the capabilities of present and future spectral instruments with the aim of identifying a spectral feature which may allow us to discriminate between metal-rich and pure-metal plasmas in X-ray spectra of SNRs. We studied the behaviour of the most common X-ray emission processes of an optically thin plasma in the high-abundance regime. We investigated spectral features of bremsstrahlung, radiative recombination continua (RRC) and line emission, by exploring a wide range of chemical abundances, plasma temperatures and ionization parameters. We then synthesized X-ray spectra from a state-of-the-art 3D hydrodynamic (HD) simulation of Cas A, by using the response matrix from the Chandra ACIS-S CCD detector and that of the XRISM/Resolve X-ray calorimeter spectrometer. We found that a bright RRC shows up when the plasma is made of pure-metal ejecta, and a high spectral resolution is needed to actually identify this ejecta signature. We tested and verified the applicability of our novel diagnostic tool and we propose a promising target for the future detection of such spectral feature: the southeastern Fe-rich clump of Cas A. We found that, while there is no way to unambiguously reveal pure-metal ejecta emission with CCD detectors, X-ray calorimeters will be able to pinpoint the presence of pure-metal RRC and to recover correctly absolute mass and the chemical composition of the ejecta, opening a new window on the link progenitor-supernova-remnant.

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Speaker: Scott Wolk (CfA)

Titolo: SEEJ: SmallSat Exosphere Explorer of hot Jupiters

Abstract:

The first detected exoplanets found were “hot Jupiters”; these are large Jupiter-like planets in close orbits with their host star. The stars in these so-called “hot Jupiter systems” can have significant X-ray emission and the X-ray flux likely changes the evolution of the overall star-planetary system in at least two ways: (1) the intense high energy flux alters the structure of the upper atmosphere of the planet – in some cases leading to significant mass loss; (2) the angular momentum and magnetic field of the planet induces even more activity on the star, enhancing its X-rays, which are then subsequently absorbed by the planet. If the alignment of the systems is appropriate, the planet will transit the host star. The resulting drop in flux from the star allows us to measure the distribution of the low-density planetary atmosphere. We describe a science mission concept for a SmallSat Exosphere Explorer of hot Jupiters (SEEJ; pronounced “siege”). SEEJ will monitor the X-ray emission of nearby X-ray bright stars with transiting hot Jupiters in order to measure the lowest density portion of exoplanet atmospheres and the coronae of the exoplanet hosts. SEEJ will use revolutionary Miniature X-ray Optics (MiXO) and CMOS X-ray detectors to obtain sufficient collecting area and high sensitivity in a low mass, small volume and low-cost package. SEEJ will observe scores of transits occurring on select systems to make detailed measurements of the transit depth and shape which can be compared to out-of-transit behavior of the target system. The depth and duration of the flux change will allow us to characterize the exospheres of multiple hot Jupiters in a single year. In addition, the long baselines (covering multiple stellar rotation periods) from the transit data will allow us to characterize the temperature, flux and flare rates of the exoplanet hosts at an unprecedented level. This, in turn, will provide valuable constraints for models of atmospheric loss. In this contribution we outline the science of SEEJ and focus on the enabling technologies Miniature X-ray Optics and CMOS X-ray detectors.