Calendar

Questo lavoro di tesi e` rivolto allo studio dei transiti di pianeti in bande ad alta energia. Le favorevoli condizioni di osservabilita` del transito di Venere del 5-6 Giugno 2012, fanno di questo evento una utile opportunita` per questo tipo di studi. Il transito e` stato seguito dai telescopi a bordo delle missioni spaziali SDO e Hinode, che ci hanno fornito dati con cui siamo riusciti a misurare il raggio del pianeta in tre bande diverse: ottico, EUV ed X. La seconda parte della tesi riguarda la simulazione di transiti di pianeti di diverse dimensioni su delle immagini reali della corona solare. I dati sono stati acquisiti dal telescopio XRT, della missione spaziale Hinode, nei raggi X. Trattando il sole come una stella lontana, abbiamo ricavato le curve di luce di transito, e con lo studio del curtosi di queste ultime siamo riusciti a stabilire dei limiti alle dimensioni delle regioni attive eclissate dal pianeta durante il transito. Questo studio potrebbe fornire delle utili previsioni per la pianificazione di osservazioni di transiti con i futuri satelliti per raggi X come Athena+ dell’ Agenzia Spaziale Europea.

In cold and dense interstellar regions, where temperatures can be as low as 10 K, most molecules are expected to condense onto grains, and consequently be depleted in the gas phase. CO is mostly frozen out in these environments, though it is sometimes also observed in the gas phase in a few cold molecular clouds such as IC 5146, L977 and L183. Mechanisms that were proposed to explain why CO is not fully condensed in dense clouds include UV-induced photodesorption, cosmic-ray whole grain heating, cosmic-ray spot heating, and chemical desorption of weakly bound molecules. Shen et al. (2004, A&A, 415, 203) reported a model of CO desorption from cosmic-ray-induced UV photons and showed that such a yield is almost one order of magnitude larger than that directly induced by cosmic-ray particles, while other desorption mechanisms could not explain astronomical observations. A more recent study in which pure CO ice was irradiated with an MDHL at 15-18 K showed a photodesorption yield of 2.7×10^-3 molecules photon-1 (Öberg et al. 2007, ApJ, 662, L23). In contrast, Muñ oz Caro et al. (2010, A & A, 522, A108) reported photodesorption yields for CO ice irradiated with an MDHL at 8 K and 15 K of 5.4×10^-2 and 3.5×10^-2 molecules photon^-1, respectively, which is one order of magnitude larger than the values reported by Öberg et al. (2007). In this talk, we will not only present experimental study consists in the measurement of the vacuum-UV (VUV) emission spectra of a microwave-discharge hydrogen-flow lamp (MDHL), which is commonly used in astrochemistry laboratories working on ice VUV photoprocessing, but also in the measurement of VUV absorption cross section of CO and CO2 ices in order to explain the processes induced by photons in CO ice from a broad energy range are different and more complex than the sum of individual processes induced by monochromatic sources scanning the same energy range, due to the discrepancy of absorption cross section between parent molecules and products in Ly-α and H2 molecular emission ranges.

Astronomy is in a Golden Age. Ambitious surveys such as COSMOS are possible only because we have three Great Observatories operating at once – Chandra, Hubble and Spitzer – spanning the electromagnetic spectrum. COSMOS-Legacy illustrates how tightly connected these bands are. But Golden Ages are short, or they wouldn’t be golden. Our Golden Age may end because our telescopes grow exponentially in cost and have reached the point where the next step is unaffordable. In the age of JWST, will we have to wait a decade or more to have complementary X-ray observations? I discuss 3 responses to this looming crisis (other than giving up!). The third response is generational in timescale but offers open-ended growth: the harnessing of space resources. Astronomers can help this era come about by re-starting “Applied Astronomy”. Then we will be able to surpass COSMOS-Legacy.

Brown dwarfs – objects intermediate in mass between stars and planets – are ideal benchmark objects to test theories of star and planet formation. In particular, we hope to contribute to the understanding of the Initial Mass Function, the evolution of disks, and the physics of accretion. In this talk I will present results from a variety of observational studies focused on young brown dwarfs. I will show recent findings from our brown dwarf survey SONYC (Substellar Objects in Nearby Young Cluster), from IR and submm/mm observations of brown dwarf disks, and from variability studies aimed to constrain magnetic activity and accretion.

Active star formation was originally identified by optical variability. Nonetheless constraints on telescope time and limitations in capability generally limited observations of young stars to single spectral observations and optical photometric monitoring. This has led to our current picture of star formation of rotating spotted star surrounded by a static disk. I discuss recent near and mid infrared observations which demonstrate that the disk is highly dynamic with periodic structure which appear to be related with both stellar rotation and circumstellar revolutionary times scales. In our JHK study of Orion we find periods for hundreds of Class I and Class II objects and demonstrate complex changes in disk structure. Mid-IR observations show significant variability as well. Finally I discuss the first X-ray observation of a planetary transit. We demonstrate the X-ray radius is significantly greater than the optical extent.

In questa tesi si parla di Astronomia Gamma e, in particolare, della descrizione di un simulatore che determina l’efficienza quantica del fotomoltiplicatore al Silicio (SiPM) montato sul telescopio prototipo ASTRI SST-2M. Le sorgenti VHE vengono osservate dal suolo, sfruttando il fenomeno della radiazione Cherenkov. I telescopi gia` attivi per queste osservazioni sono gli IACT, Imaging Atmospheric Cherenkov Telescopes. Di futura generazione e’, invece, il CTA, Cherenkov Telescopes Array, con il quale si prevede di raggiungere un’energia di soglia di 1 Tev. L’Italia sta collaborando alla sua costruzione con il progetto ASTRI, realizzando un prototipo per i Small Size Telescopes (SST). Il prototipo monta sul piano focale un rivelatore al Silicio per il quale e’ stata condotta una simulazione che restituisce l’efficienza quantica (PDE) del dispositivo. Dal momento che la casa costruttrice non forniva le dimensioni del fotomoltiplicatore, sono state prodotte diverse curve di PDE, al variare delle dimensioni del SiPM e dell’overvoltage a cui opera. L’aderenza con i dati sperimentali, rilevati dal laboratorio COLD dell’Osservatorio Astronomico di Catania, e’ stata verificata con il test del chi quadro.

Young stars are known to be variable sources both in optical, infrared, and X-ray. This variability is strictly correlated with their physical properties and the morphology of the circumstellar material, if any. The study of their light curves and the connection between the observed variability in the various regions of the electromagnetic spectrum provides a deep insight on the physical properties and evolutionary status of young stars, both with and without disks. This motivated the Coordinated Synoptic Investigation of the young open cluster NGC~2264 (CSI 2264, Cody et al. 2014, Stauffer et al. 2014). This project is an unique and unprecedented cooperative project involving simultaneous observations with 15 ground and space telescopes, and covering a wide part of the electromagnetic spectrum from X-ray to mid-infrared. In this talk I will compare the optical and X-ray variability of NGC 2264 candidate members using simultaneous observations taken with the Convection, Rotation and Planetary Transits satellite (CoRoT), and Chandra/ACIS-I. I will show that a significant correlation between the flux variability in optical and X-ray is observed among the stars with disk where the central star is periodically or irregularly obscured by material associated with the circumstellar disk, and that in some of these sources an increase of the hydrogen column nH is observed during the obscuration observed in optical. In more than 50\% of the disk-less objects the optical and X-ray flux variability are anticorrelated, in about 25% they are correlated, while the remainder do not show any correlation between the variability in the two bands. I will discuss how the distribution of spots in the photosphere and active regions in the stellar coronae, inclination of the rotational axis, and rotational period may influence this result.

Secondary eclipse observations allow the characterisation of the dayside of hot Jupiter exoplanet atmospheres. The standard, state of the art way of getting these observations is by using IRAC on the Spitzer Space Telescope. This instrument was not designed to reach the precision required to conduct these observations. However, it is possible to push IRAC to detect the secondary eclipse. It has been used for nearly 10 year to observe secondary eclipses of a handful of exoplanets. The data are strongly affected by systematic errors which can limit the accuracy that we can measure the depth of the eclipse, as well as other parameters that can be derived from the lightcurve. In this talk I discuss the way that the WASP group analyses these data and describe a method of signal injection that can help in determining more realistic error bars on the time of mid eclipse and the eclipse depth. The two are fundamental parameters that come out of these observations. I also describe the work I would like to conduct as a postdoctoral research assistant once I have completed my PhD.

Il restauro e la conservazione dei beni librari ed archivistici sono stati considerati per molto tempo attivita` da espletare solo in laboratorio e quasi esclusivamente a vantaggio dei pezzi piu` preziosi, importanti o rappresentativi delle collezioni. Negli ultimi anni invece si sono affermate attivita` di conservazione che beneficino un grande numero di beni. Si e`, inoltre, finalmente imposta l’idea che il conservatore-restauratore e` una figura che debba occuparsi della salvaguardia delle collezioni ad ampio spettro, prendendosi cura anche della manipolazione, della movimentazione, degli ambienti di conservazione e della musealizzazione. In quest’ottica il tirocinio pratico Corso di Laurea abilitante in Conservazione e Restauro dei Beni Culturali, ha previsto un cantiere presso la Biblioteca ed Archivio Storico dell’I.N.A.F – Osservatorio Astronomico di Palermo. Il patrimonio storico di questa istituzione conta un’importante collezione bibliografica, iniziata dal fondatore (G. Piazzi) e arricchita dai vari direttori ad esso succedutisi, un ricchissimo archivio che raccoglie la documentazione non soltanto amministrativa dell’osservatorio ed anche una preziosa raccolta fotografica di positivi e negativi ancora in parte da esplorare.