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In un intreccio di letteratura, cinema, storia, astronomia e strumenti scientifici, verranno presentati i risultati di uno studio che prende le mosse da lavori precedenti condotti in collaborazione con Donata Randazzo e di recente estesi con alcuni contributi esterni ad OAPa, che spaziano fino ad una … inattesa conclusione.

In less than two decades, the field of exoplanetary science has undergone nothing short of a revolution. We have gone from the oddball discovery of a “planetary sized object” orbiting a pulsar star (Wolszczan and Frail, 1992) to efficient and systematic all-sky surveys with one thousand confirmed exoplanets and over three thousand candidates awaiting confirmation (Batalha et al., 2013). With such wealth of systems discovered, the next step in exoplanet research is to characterise the properties of these systems. One way of doing so is by measuring the chemical and thermal make-up of their atmospheres. In this seminar I will give an overview of what we know about these foreign worlds, the current techniques used and discuss the difficulties faced when having to reach the required photometric accuracy of 10^-4 over the duration of several hours. In the figure: the 0.3 – 2.4 micron spectrum of HD-189733b including all the high-precision measurements available in the literature. If the datapoints are observed simultaneously they are plotted with the same colour. Important to stress that combining multi-epoch dataset is a risky operation: instrumental systematics and stellar activity may prevent altogether an accurate measurement of the absolute transit depth.

Galactic cosmic rays are believed to be accelerated at supernova remnant shocks. This idea is very popular but we still miss a conclusive evidence of its validity. In this talk, I will give a general review on the connections between gamma-ray astronomy and cosmic-ray physics. In particular, I will discuss how recent (and future) gamma-ray observations of supernova remnants and molecular clouds can (will) help us in understanding the origin of galactic cosmic rays.

Nel mio elaborato si presenta un’importante diagnostica che ha di recente permesso di identificare e studiare il processo di fotoevaporazione del materiale nei dischi circumstellari. La fotoevaporazione e` un processo attraverso cui il materiale, in orbita intorno ad una stella, viene espulso dopo essere stato riscaldato dalla radiazione della stella. La diagnostica si basa sullo studio della riga proibita del NE II a 12,8135 micron. Questa riga, a causa dell’alto potenziale di ionizzazione del neon, puo` essere prodotta solo se la stella e` una sorgente di radiazione ad alta energia (UV e X). Nell’elaborato si affronta questa diagnostica per le stelle T Cha e Mp Mus, due T-Tauri classiche. In entrambi i sistemi e` stata misurata la riga a 12,81 micron e si e` calcolato tramite spostamento Doppler la velocita` con cui il materiale fotoevapora dalla stella, notando che la velocita` di evaporazione e` compatibile con il processo di fotoevaporazione causato da emissione X e UV. E` stata pure misurata la FWHM della riga, utilizzata per calcolare la velocita` di rotazione del materiale intorno alla stella e da quest’ultima si e` stimata la distanza del materiale dalla stella.

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.