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Dissertations / Theses on the topic 'Astronomia X'

Author: Grafiati
Published: 9 March 2023
Last updated: 31 July 2025

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1

Camero, Arranz Ascension. "Accreting X-Ray pulsars. The high energy picture." Doctoral thesis, Universitat de València, 2007. http://hdl.handle.net/10803/9484.

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El objetivo principal de esta tesis ha sido el estudio del comportamiento transitorio durante estallidos de distinto tipo, de una selección de pulsares acretores en rayos X, localizados en el plano galáctico.Con ello se pretende haber avanzado hacia una explicación más clara de la naturaleza de estas objetos binarios de alta masa (con estrella de neutrones como objeto compacto), así como de los mecanismos físicos que operan en este escenario. Para todo esto se han analizado datos de dos misiones espaciales:INTEGRA Y RXTE.El segundo objetivo ha sido el estudio de la zona del brazo galactico de
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2

Munar, i. Adrover Pere. "High energy processes in young stellar objects and high-mass X-ray binaries." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/144509.

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The high energy astrophysics, specifically the gamma-ray astrophysics, studies the processes that cannot be caused by hot matter but by other mechanisms colled non thermaland processes, which involve matter with energies above ~ 1 MeV. There are currently a number of instruments able to detect this radiation, such as AGILE and Fermi satellites or Cherenkov telescopes like MAGIC at the Earth's surface. In this thesis we studied two main types of systems that, as it has been observed or theoretically predicted, can produce gamma radiation : young stellar objects and high-mass X-ray binarie
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3

Parisi, Pietro <1982&gt. "Multiwavelength studies of hard X-ray selected sources." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3775/1/Parisi_Pietro_tesi.pdf.

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4

Parisi, Pietro <1982&gt. "Multiwavelength studies of hard X-ray selected sources." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3775/.

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5

Donnarumma, Annamaria <1981&gt. "X-ray and lensing mass estimates in galaxy clusters." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2955/1/donnarumma_annamaria_tesi.pdf.

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In this Thesis we have presented our work on the analysis of galaxy clusters through their X-ray emission and the gravitational lensing effect that they induce. Our research work was mainly finalised to verify and possibly explain the observed mismatch between the galaxy cluster mass distributions estimated through two of the most promising techniques, i.e. the X-ray and the gravitational lensing analyses. Moreover, it is an established evidence that combined, multi-wavelength analyses are extremely effective in addressing and explaining the open issues in astronomy: however, in order
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6

Donnarumma, Annamaria <1981&gt. "X-ray and lensing mass estimates in galaxy clusters." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2955/.

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In this Thesis we have presented our work on the analysis of galaxy clusters through their X-ray emission and the gravitational lensing effect that they induce. Our research work was mainly finalised to verify and possibly explain the observed mismatch between the galaxy cluster mass distributions estimated through two of the most promising techniques, i.e. the X-ray and the gravitational lensing analyses. Moreover, it is an established evidence that combined, multi-wavelength analyses are extremely effective in addressing and explaining the open issues in astronomy: however, in order
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7

GIANNI', SILVIA. "X-ray overview of INTEGRAL Blazars." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2010. http://hdl.handle.net/2108/1218.

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I quasars Radio Loud (RL) fanno parte di una piccola percentuale (~10%) di Nuclei Galattici Attivi (AGN) e sono caratterizzati da una forte emissione nella banda radio. Lo scopo del nostro lavoro e’ lo studio dell’emissione nella banda dell’X e dell’hard-X di una sotto-classe di questi oggetti: i Blazars. Gli oggetti di tipo Blazar sono AGN aventi un getto di particelle relativistiche (per lo piu’ elettroni e protoni) orientato a piccoli angoli rispetto alla linea di vista. Questa particolare classe di AGN include oggetti di tipo BL Lacerate (BL Lac) e Flat Spectrum Radio Quasar (FSRQ), che si
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8

Martocchia, Andrea. "X-ray Spectral Signatures of Accreting Black Holes." Doctoral thesis, SISSA, 2000. http://hdl.handle.net/20.500.11767/3963.

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9

Oss, Valerio. "Telescopi ottici, radio, X: principi e differenze." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amslaurea.unibo.it/25282/.

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In questo elaborato si vuole descrivere il funzionamento generale di telescopi, in banda ottica, radio e X, con un approfondimento sui principi di funzionamento e sulle relative differenze. In generale si può definire un telescopio come uno strumento capace di raccogliere la radiazione elettromagnetica per concentrarla grazie a lenti, specchi o antenne paraboliche, in un’area ristretta, un punto focale in cui si trova un rivelatore, che può essere l’occhio umano, un CCD, un illuminatore ecc. Questi, grazie anche a software dedicati, elaborano la radiazione raccolta fornendo un’immagine della s
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10

Santucci, Giulia. "Telescopi ottici, radio, X: principi e differenze." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7200/.

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Per telescopio intendiamo qualsiasi strumento finalizzato alla misura della radiazione proveniente dallo spazio. Tipicamente questo nome viene riservato agli strumenti ottici; tuttavia è utile utilizzare un singolo nome per caratterizzare tutta la classe di strumenti per le osservazioni astronomiche. Un telescopio è uno strumento capace di raccogliere radiazione da una grande superficie, concentrandola in un punto. La luce viene in genere raccolta da uno specchio o antenna, quindi elaborata da vari strumenti, come per esempio un filtro o uno spettrografo, e infine indirizzata
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11

Fioretti, Valentina <1982&gt. "Background minimization issues for next generation hard X-ray focusing telescopes." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3858/1/Fioretti_Valentina_Tesi.pdf.

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The hard X-ray band (10 - 100 keV) has been only observed so far by collimated and coded aperture mask instruments, with a sensitivity and an angular resolution lower than two orders of magnitude as respects the current X-ray focusing telescopes operating below 10 - 15 keV. The technological advance in X-ray mirrors and detection systems is now able to extend the X-ray focusing technique to the hard X-ray domain, filling the gap in terms of observational performances and providing a totally new deep view on some of the most energetic phenomena of the Universe. In order to reach a sensitivity
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12

Fioretti, Valentina <1982&gt. "Background minimization issues for next generation hard X-ray focusing telescopes." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3858/.

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The hard X-ray band (10 - 100 keV) has been only observed so far by collimated and coded aperture mask instruments, with a sensitivity and an angular resolution lower than two orders of magnitude as respects the current X-ray focusing telescopes operating below 10 - 15 keV. The technological advance in X-ray mirrors and detection systems is now able to extend the X-ray focusing technique to the hard X-ray domain, filling the gap in terms of observational performances and providing a totally new deep view on some of the most energetic phenomena of the Universe. In order to reach a sensitivity
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13

Giustini, Margherita <1983&gt. "Accretion disk winds in active galactic nuclei: an X-ray view." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3892/1/giustini_margherita_tesi.pdf.

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This Thesis focuses on the X-ray study of the inner regions of Active Galactic Nuclei, in particular on the formation of high velocity winds by the accretion disk itself. Constraining AGN winds physical parameters is of paramount importance both for understanding the physics of the accretion/ejection flow onto supermassive black holes, and for quantifying the amount of feedback between the SMBH and its environment across the cosmic time. The sources selected for the present study are BAL, mini-BAL, and NAL QSOs, known to host high-velocity winds associated to the AGN nuclear regions.
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14

Giustini, Margherita <1983&gt. "Accretion disk winds in active galactic nuclei: an X-ray view." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3892/.

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This Thesis focuses on the X-ray study of the inner regions of Active Galactic Nuclei, in particular on the formation of high velocity winds by the accretion disk itself. Constraining AGN winds physical parameters is of paramount importance both for understanding the physics of the accretion/ejection flow onto supermassive black holes, and for quantifying the amount of feedback between the SMBH and its environment across the cosmic time. The sources selected for the present study are BAL, mini-BAL, and NAL QSOs, known to host high-velocity winds associated to the AGN nuclear regions.
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15

Masini, Alberto <1990&gt. "Obscured and Compton-thick AGN in NuSTAR hard X-ray surveys." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amsdottorato.unibo.it/8361/1/Masini_Thesis_online2.pdf.

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This Thesis focuses on NuSTAR hard X-ray surveys of Active Galactic Nuclei (AGN). One of the major goals of the NuSTAR mission is to study with unprecedented detail the obscured and heavily obscured (Compton-thick, CT) populations of AGN, significantly contributing to the diffuse cosmic X-ray background (CXB),and major actors within the evolutionary cycle of galaxies. In the first part, a survey of a small sample (∼ a dozen) of local (z < 0.03) heavily obscured AGN, selected by their water megamaser emission at ∼22.23 GHz, is presented. Thanks to the NuSTAR hard X-ray spectral coverage (exten
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16

SALVAGGIO, CHIARA. "BLACK HOLE OR NEUTRON STAR? THIS IS (ONE OF) THE QUESTION(S) A VARIABILITY STUDY OF ULXs TOWARDS A BETTER COMPREHENSION OF THEIR PHYSICS." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/375598.

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Le sorgenti ultraluminose in banda X (ULX) sono binarie X extragalattiche con luminosità maggiore del limite di Eddington per un buco nero (BH) di 10 Msun (L>10^39 erg/s). Si pensa siano alimentate nella maggior parte dei casi da un accrescimento super-Eddington su BH stellari o stelle di neutroni (NS). Solo in pochi casi siamo a conoscenza della natura dell'oggetto compatto, identificata grazie alla rilevazione di pulsazioni, che possono essere emesse solo da una NS. La frazione relativa di BH e NS nelle ULX e i dettagli dell'accrescimento super-Eddington sono ancora sconosciuti. In questa te
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17

Marchetto, Alina. "Telescopi ottici, radio, X: principi e differenze." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18486/.

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Lo scopo di questo elaborato è di descrivere il funzionamento dei telescopi che lavorano nelle bande ottico, radio e X, sottolineandone i principi di funzionamento e le loro differenze. Nella stesura dell'elaborato ho cercato di seguire la linea storica degli eventi, partendo dalla descrizione dei telescopi ottici -i primi che sono stati costruiti- per poi passare ai radiotelescopi e ai più "giovani" telescopi X. Ho dedicato un ultimo capitolo all'approfondimento dell'evento GW170817 che ritengo un esempio utile a mostrare le diverse funzionalità di questi telescopi e allo stesso tempo l
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18

MULERI, FABIO. "Expectations and perspectives of X-ray photoelectric polarimetry." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2009. http://hdl.handle.net/2108/816.

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La polarimetria è l'ultima branca dell'Astronomia nella banda dei raggi X ancora inesplorata. Nonostante un vasto interesse testimoniato da un'estesa letteratura, il suo sviluppo è stato impedito dalla mancanza di dispositivi la cui sensibilità giustificasse l'inserimento di polarimetri X a bordo delle missioni spaziali moderne. Ciononostante nuovi strumenti basati sull'effetto fotoelettrico, capaci di risolvere le tracce dei fotoelettroni in un gas, offrono oggi la possibilità di colmare il divario tra aspettative teoriche e gli scarsi risultati ad oggi raggiunti: in questo ambito, uno dei pr
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19

Ponti, Gabriele <1977&gt. "Probing the innermost regions around supermassive black holes through X–ray spectral variability." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/364/1/gpthesis.pdf.

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20

Ponti, Gabriele <1977&gt. "Probing the innermost regions around supermassive black holes through X–ray spectral variability." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/364/.

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21

Morandi, Andrea <1979&gt. "Properties of gas and dark matter in X-ray galaxy clusters with Sunyaev Zel'dovich measurements." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/633/1/Tesi_Morandi_Andrea.pdf.

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I have studied entropy profiles obtained in a sample of 24 X-ray objects at high redshift retrieved from the Chandra archive. I have discussed the scaling properties of the entropy S, the correlation between metallicity Z and S, the profiles of the temperature of the gas, Tgas, and performed a comparison between the dark matter 'temperature' and Tgas in order to constrain the non-gravitational processes which affect the thermal history of the gas. Furthermore I have studied the scaling relations between the X-ray quantities and Sunyaev Zel'dovich measurements. I have observed that X-ray
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22

Morandi, Andrea <1979&gt. "Properties of gas and dark matter in X-ray galaxy clusters with Sunyaev Zel'dovich measurements." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/633/.

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I have studied entropy profiles obtained in a sample of 24 X-ray objects at high redshift retrieved from the Chandra archive. I have discussed the scaling properties of the entropy S, the correlation between metallicity Z and S, the profiles of the temperature of the gas, Tgas, and performed a comparison between the dark matter 'temperature' and Tgas in order to constrain the non-gravitational processes which affect the thermal history of the gas. Furthermore I have studied the scaling relations between the X-ray quantities and Sunyaev Zel'dovich measurements. I have observed that X-ray
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23

Torresi, Eleonora <1981&gt. "The gaseous environment of radio galaxies: a new perspective from high-resolution x-ray spectroscopy." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3820/1/Torresi_Eleonora_tesi.pdf.

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It is known that massive black holes have a profound effect on the evolution of galaxies, and possibly on their formation by regulating the amount of gas available for the star formation. However, how black hole and galaxies communicate is still an open problem, depending on how much of the energy released interacts with the circumnuclear matter. In the last years, most studies of feedback have primarily focused on AGN jet/cavity systems in the most massive galaxy clusters. This thesis intends to investigate the feedback phenomena in radio--loud AGNs from a different perspective studying
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Torresi, Eleonora <1981&gt. "The gaseous environment of radio galaxies: a new perspective from high-resolution x-ray spectroscopy." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3820/.

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It is known that massive black holes have a profound effect on the evolution of galaxies, and possibly on their formation by regulating the amount of gas available for the star formation. However, how black hole and galaxies communicate is still an open problem, depending on how much of the energy released interacts with the circumnuclear matter. In the last years, most studies of feedback have primarily focused on AGN jet/cavity systems in the most massive galaxy clusters. This thesis intends to investigate the feedback phenomena in radio--loud AGNs from a different perspective studying
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25

Perna, Michele <1987&gt. "Starbursting to Quenching: the Role of X-Ray Emission in Active Galactic Nuclei Feedback Processes." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7767/1/perna_michele_tesi.pdf.

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One of the most debated topics of modern extragalactic astrophysics is the co-evolution between the SMBHs sitting in the nuclei of the galaxies and their hosts. According to the most popular models of AGN and galaxies co-evolution, starburst galaxies, unobscured quasars and inactive (and quenched) galaxies represent the different phases of an evolutionary sequence reproducing the most massive galaxies observed in the Universe. In this context, gas flows in the form of energetic outflows are postulated to play a pivotal role in this process, given that they regulate both accretion and eject
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26

Vito, Fabio <1986&gt. "X-ray properties and evolution of high-redshift AGN, and the gas content of host galaxies." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6729/1/Vito_Fabio_Tesi.pdf.

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In this thesis, I have investigated the evolution of the high-redshift (z > 3) AGN population by collecting data from some of the major Chandra and XMM-Newton surveys. The final sample (141 sources) is one of the largest selected at z> 3 in the X- rays and it is characterised by a very high redshift completeness (98%). I derived the spectral slopes and obscurations through a spectral anaysis and I assessed the high-z evolution by deriving the luminosity function and the number counts of the sample. The best representation of the AGN evolution is a pure density evolution (PDE) model: the AGN sp
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27

Vito, Fabio <1986&gt. "X-ray properties and evolution of high-redshift AGN, and the gas content of host galaxies." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6729/.

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In this thesis, I have investigated the evolution of the high-redshift (z > 3) AGN population by collecting data from some of the major Chandra and XMM-Newton surveys. The final sample (141 sources) is one of the largest selected at z> 3 in the X- rays and it is characterised by a very high redshift completeness (98%). I derived the spectral slopes and obscurations through a spectral anaysis and I assessed the high-z evolution by deriving the luminosity function and the number counts of the sample. The best representation of the AGN evolution is a pure density evolution (PDE) model: the AGN sp
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28

Dadina, Mauro <1969&gt. "X-Ray studies of the physics of matter around super-massive black-holes in nearby Seyfert galaxies." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1465/1/Dadina_Mauro_tesi.pdf.

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Seyfert galaxies are the closest active galactic nuclei. As such, we can use them to test the physical properties of the entire class of objects. To investigate their general properties, I took advantage of different methods of data analysis. In particular I used three different samples of objects, that, despite frequent overlaps, have been chosen to best tackle different topics: the heterogeneous BeppoS AX sample was thought to be optimized to test the average hard X-ray (E above 10 keV) properties of nearby Seyfert galaxies; the X-CfA was thought the be optimized to compare the proper
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Dadina, Mauro <1969&gt. "X-Ray studies of the physics of matter around super-massive black-holes in nearby Seyfert galaxies." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1465/.

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Seyfert galaxies are the closest active galactic nuclei. As such, we can use them to test the physical properties of the entire class of objects. To investigate their general properties, I took advantage of different methods of data analysis. In particular I used three different samples of objects, that, despite frequent overlaps, have been chosen to best tackle different topics: the heterogeneous BeppoS AX sample was thought to be optimized to test the average hard X-ray (E above 10 keV) properties of nearby Seyfert galaxies; the X-CfA was thought the be optimized to compare the proper
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30

Tombesi, Francesco <1982&gt. "An X-ray absorption line spectroscopy study of ultra-fast outflows from the innermost regions of AGNs." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2548/1/tombesi_francesco_tesi.pdf.

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31

Tombesi, Francesco <1982&gt. "An X-ray absorption line spectroscopy study of ultra-fast outflows from the innermost regions of AGNs." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2548/.

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32

SCARANO, FABIANA. "Multiband studies of Neutron Stars in Low Mass X-ray Binary systems & the HERMES project." Doctoral thesis, Università degli Studi di Cagliari, 2018. http://hdl.handle.net/11584/288442.

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The study of the X-ray spectra of accreting compact objects such as neutron stars, and in particular the emission and absorption features common in the X-ray systems, provides a powerful tool to investigate the innermost parts of the accretion disc and the regions close to the compact object. The first part of my work concerned the analysis of the spectra, of two bright, persistent accreting low-mass X-binaries classified as atoll sources: GX 3+1 and GX 9+9. Broad emission features are shown in the spectrum of the first source; on the contrary, the second one shows the total absence of the re
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33

Nardini, Marco. "Optical versus X–ray afterglows of GRBs: towards understanding the emission processes." Doctoral thesis, SISSA, 2009. http://hdl.handle.net/20.500.11767/4269.

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Gamma–Ray Bursts (GRBs) are the most distant objects ever detected after the recombination epoch. They consist of a short intense emission episode of gammarays (10 keV–2 MeV) with typical duration between 10−2 and 103 seconds. This is called the “prompt” emission phase. GRBs are classified, according to their observed duration, into short GRBs (lasting less than 2s) and long GRBs (lasting more than 2 s). During the prompt phase GRBs are the brightest objects in the gamma–ray sky. The gamma–ray prompt emission is accompanied by a long lasting emission, called “afterglow”, covering the w
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Peracaula, i. Bosch Marta. "The radio emitting X-ray binary systems LS 1+61°303 and Cygnus X-3." Doctoral thesis, Universitat de Barcelona, 1997. http://hdl.handle.net/10803/757.

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The purpose of this work has been the study of Radio Emitting X-Ray Binaries (REXRBs) both from the observational and theoretical approaches. <br/><br/>We have mainly concentrated in the analysis of their properties inferred from their emission in radio and X-ray wavelengths. Our observational contribution has been done specially at different centimetric and millimetric wavelengths, although contrast with other bands of the electromagnetic spectrum has been always considered. <br/><br/>From the about 25 REXRBs detected, we have directly observed and analyzed the sources LS 1+61 °303 and Cygnus
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MARINO, ALESSIO. "Imperfect accretion: ejecting matter in X-ray binaries." Doctoral thesis, Università degli Studi di Palermo, 2021. http://hdl.handle.net/10447/479017.

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X-ray binaries are binary stars composed of a compact object (a black hole, a neutron star) accreting matter from a companion star. These sources can be considered perfect astrophysical laboratories to test our knowledge of, e.g., General Relativity and Magneto-Hydrodynamics. Accretion is the key phenomenon characterizing these systems, but it is not always completely efficient. In many systems, ejections of matter are also observed, e.g. in the form of jets and winds, or also suggested, e.g. to explain the observed strong orbital expansion of a number of systems. Furthermore accretion and eje
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Moldón, Vara Francisco Javier. "Structure and nature of gamma-ray binaries by means of VLBI observations." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/96996.

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Gamma-ray binaries are extreme systems that produce non-thermal emission from radio to very-high-energy (above TeV) gamma rays, with the energy output in the spectral energy distribution (SED) dominated by the MeV–GeV photons. Their broadband emission is usually modulated by the orbital cycle of the system, which suggests that the physical conditions are also periodic and reproducible. The diversity of systems, together with the reproducibility of the conditions within each system, makes gamma-ray binaries excellent physical laboratories in which high energy particle acceleration, diffusion, a
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Giulietti, Marika. "Telescopi ottici, radio, X: principi e differenze." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12353/.

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Lo scopo di questo elaborato è la descrizione dei principi su cui si basano i telescopi ottici, radio e x nell'osservazione dei corpi celesti, la loro meccanica di funzionamento e le relative differenze. Un telescopio è uno strumento fisico volto a raccogliere radiazione proveniente da oggetti molto distanti in una grande regione di cielo facendola convogliare su un'area ristretta. Questo avviene tramite l'utilizzo ad esempio di specchi, lenti o antenne, in modo da ottenere la massima risoluzione possibile. I fotoni raccolti vengono poi fatti convogliare in dei rilevatori come un obietti
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MARCHESE, ELENA. "X-ray absorption in Active Galactic Nuclei." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2015. http://hdl.handle.net/10281/89114.

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I Nuclei Galattici Attivi (AGN) sono tra le sorgenti più luminose dell’Universo e sono osservati in circa 10-20% delle galassie nell’Universo locale. Il meccanismo di generazione dell’energia di queste sorgenti è l’accrescimento di materia su un buco nero supermassivo (SMBH). Secondo il paradigma del Modello Unificato (UM) il SMBH è circondato da un assorbitore uniforme e anisotropo di gas e polveri, con geometria toroidale, che si estende da 1pc a 100pc. Anche se a livello generale l’UM è corretto, lavori recenti hanno evidenziato la necessità di formulare modelli alternativi per spiegare ad
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Ameglio, Silvia. "Using hydrodynamical simulations to combine Sunyaev-Zeldovich and X-ray studies of galaxy clusters." Doctoral thesis, Università degli studi di Trieste, 2008. http://hdl.handle.net/10077/2561.

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2006/2007<br>The main focus of the work presented in this Thesis is the study of the potentiality and possible systematics in combining observations of the thermal Sunyaev-Zeldovich effect (tSZ) and of the X–ray emission in galaxy clusters. The great advantage of the combination of this two types of observations is that they have a different dependence on the properties (density and temperature) of the Intra Cluster Medium (ICM). Also the behavior with redshift is completely different: X–rays provide very bright images of nearby clusters, but decline rapidly with redshift, while the tSZ signa
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EGRON, ELISE MARIE JEANNE. "Spectral Comparisons of Neutron Star Low-Mass X-Ray Binaries with Black Hole X-Ray Binaries." Doctoral thesis, Università degli Studi di Cagliari, 2013. http://hdl.handle.net/11584/266223.

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The study of high-resolution X-ray spectra of neutron star low-mass X-ray binaries (LMXBs) allows the investigation of the innermost parts of the accretion disk and immediate surroundings of the compact object. The weak magnetic eld of old neutron stars present in such systems allows the accretion disk to approach very close to the compact object, like in black hole X-ray binaries. Using data from X-ray satellites such as XMM-Newton, RXTE, and BeppoSAX, I studied the reection component in two neutron star LMXBs: MXB 1728-34 and 4U 1735-44. I showed that the iron line at 6:4
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AMATO, Roberta. "CONTRIBUTION OF PSEUDO-FOCUSED SOFT PROTONS TO THE BACKGROUND OF ATHENA." Doctoral thesis, Università degli Studi di Palermo, 2021. http://hdl.handle.net/10447/479011.

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This PhD thesis explores the role of low energy protons, the so-called ‘soft protons’, as a component of the background in view of the future ESA’s X-ray mission Athena. As a matter of fact, a high level of soft proton flux at the focal plane of Athena can adversely affect the scientific goals of the mission. To prevent this, a correct estimate of the soft proton flux expected at the focal plane of the satellite is fundamental. Such an estimate can be achieved only if the reflectivity of soft protons from the optics is well understood, with efforts on both the experimental and the theoretical
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Zaninoni, Elena. "Gamma-ray bursts and their X-ray and optical afterglow." Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3422978.

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The aim of this PhD thesis is to study and characterize the optical and X-ray emission of the afterglows of gamma-ray bursts (GRBs). GRBs are the most powerful sources of electromagnetic radiation in the universe, with an isotropic luminosity that can reach values of $10^{54}$ erg/s. The Swift satellite, launched in November 2004, opened a new era for the study and understanding of the phenomenon of GRBs, thanks to the rapid response of its narrow FOV instruments that allows the accurate localization of most GRBs and the more complete coverage of the GRB evolution. In the first part of m
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FERRUGGIA, BONURA Salvatore. "X-Ray microcalorimeter detectors - Technology developments for high energy astrophysics space missions." Doctoral thesis, Università degli Studi di Palermo, 2020. http://hdl.handle.net/10447/395401.

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Improvements in the design, fabrication, and performance of astronomical detectors has ushered in the so-called era of multi messenger astrophysics, in which several different signals (electromagnetic waves, gravitational waves, neutrinos, cosmic rays) are processed to obtain detailed descriptions of their sources. Soft x-ray instrumentation has been developed in the last decades and used on board numerous space missions. This has allowed a deep understanding of several physical phenomena taking place in astrophysical sources of different scales from normal stars to galaxy clusters and huge
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NARDINI, MARCO. "Optical versus X–ray afterglows of GRBs: towards understanding the emission processes." Doctoral thesis, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 2009. http://hdl.handle.net/10281/23600.

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Gamma–Ray Bursts (GRBs) are the most distant objects ever detected after the recombination epoch. They consist of a short intense emission episode of gammarays (10 keV–2 MeV) with typical duration between 10−2 and 103 seconds. This is called the “prompt” emission phase. GRBs are classified, according to their observed duration, into short GRBs (lasting less than 2s) and long GRBs (lasting more than 2 s). During the prompt phase GRBs are the brightest objects in the gamma–ray sky. The gamma–ray prompt emission is accompanied by a long lasting emission, called “afterglow”, covering the w
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Torres, i. Albà Núria. "High Energy Processes in Active Galaxies." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668158.

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This thesis has as an objective the study of very energetic phenomena in the central regions of active galaxies. Intense star formation is triggered by mergers of galaxies, and the funneling of large quantities of gas toward the inner regions is thought to also cause accretion onto the central black hole. Whether the two processes necessarily take place together as a step of galaxy evolution is still debated. Regardless of the origin of their connection, star formation and strong AGN activity often coexist in the nuclei of galaxies. Even after star formation is no longer ongoing, the nuclea
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DEL, MONTE ETTORE. "SuperAGILE: an X-Ray monitor for a gamma mission." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2006. http://hdl.handle.net/2108/206.

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La Tesi di Dottorato di Ricerca, svolta all’IASF CNR/INAF di Roma sotto la supervisione del dott. Enrico Costa, contiene lo studio delle prestazioni scientifiche dello strumento SuperAGILE. SuperAGILE è il monitor a raggi X di AGILE, missione su satellite dell’ASI composta da due strumenti, sensibili rispettivamente nelle bande di energia 15-40 keV e 30 MeV-50 GeV, il cui lancio è previsto per la fine del 2005. SuperAGILE è uno strumento a maschera codificata, con rivelatore a microstrip di silicio e maschera di tungsteno. Oggetto della mia Tesi di Dottorato è lo studio delle prestazioni s
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Albano, Alessandra. "Spectral and timing properties of transient anomalous x-ray pulsars." Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3427009.

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In the last years, thanks to new generation satellites (mostly Chandra and XMM-Newton), an increasing number of high resolution spectral and timing observations of X-ray emitting isolated neutron stars (INS)has become available. Several new classes of X-ray emitting INSs have been discovered, all of them radio silent or with radio properties much at variance with those of Pulsar Radio (PSRs): X-ray Dim Isolated Neutron Stars (XDINSs), Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs), Central Compact Objects (CCOs), Rotating Radio Transient (RRATs, in one case). AXPs and SG
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Zemko, Polina. "Mass transfer and hydrogen burning in white dwarf binaries." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3422892.

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The thesis is devoted to a study of mass transfer, non-explosive hydrogen burning and the effects of the magnetic field in cataclysmic variables (CVs) in the context of their evolution and possible paths to Supernovae type Ia. I focused on the observational properties of CVs hosting massive white dwarfs (WDs) and/or accreting at high rate. My aims were to detect signatures of quiescent hydrogen burning, follow novae as they settle into quiescence and to assess whether the WD magnetic field alters secular evolution and the outcome of the nova explosions. The thesis consists of three chapters. T
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MARGUTTI, RAFFAELLA. "Toward new insights on the gamma ray bursts physics: from x-ray spectroscopy to the identification of characteristic time scale." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2009. http://hdl.handle.net/10281/7465.

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The PhD project is aimed at studying Gamma-Ray Burst (GRB) sources discovered by Swift from both the observational and theoretical point of view. It is basically divided into three parts: the first is dedicated to the development of a software able to automatically reduce Swift X-ray data; the second part contains the analysis and interpretation of three particularly interesting GRBs in the context of different theoretical models: the problems and the failure of most of them is shown. Finally, a third part is dedicated to the development of a temporal analysis alternative to the Fouri
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Ambrosi, Elena. "Modelling Multiwavelength Emission of Ultra-luminous X-ray sources: theory versus observations." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3424991.

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The main goal of my PhD Thesis was to investigate the nature of ULXs using their multiwave-length emission properties and to extend the treatment of the evolution of their binary systems including the effects of super-Eddington accretion. In this way we constrain the masses of the black holes and donor stars in these systems, and their accretion regime. To this end, we developed a code that enables us to constrain the properties of ULXs binaries from their position on the Color-Magnitude Diagram, from their multiwavelength SED and from additional information available on the systems (such as
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