A spectroscopic and photometric study of MSP companions in Galactic Globular Clusters

This Thesis is devoted to the study of the optical companions of Millisecond Pulsars in Galactic Globular Clusters (GCs) as a part of a large project started at the Department of Astronomy of the Bologna University, in collaboration with other institutions (Astronomical Observatory of Cagliari and Bologna, University of Virginia), specifically dedicated to the study of the environmental effects on passive stellar evolution in galactic GCs. Globular Clusters are very efficient “Kilns” for generating exotic object, such as Millisecond Pulsars (MSP), low mass X-ray binaries(LMXB) or Blue Straggler Stars (BSS). In particular MSPs are formed in binary systems containing a Neutron Star which is spun up through mass accretion from the evolving companion (e.g. Bhattacharia & van den Heuvel 1991). The final stage of this recycling process is either the core of a peeled star (generally an Helium white dwarf) or a very light almos exhausted star, orbiting a very fast rotating Neutron Star (a MSP). Despite the large difference in total mass between the disk of the Galaxy and the Galactic GC system (up a factor 103), the percentage of fast rotating pulsar in binary systems found in the latter is very higher. MSPs in GCs show spin periods in the range 1.3 ÷ 30ms, slowdown rates ˙P 1019 s/s and a lower magnetic field, respect to ”normal” radio pulsars, B 108 gauss . The high probability of disruption of a binary systems after a supernova explosion, explain why we expect only a low percentage of recycled millisecond pulsars respect to the whole pulsar population. In fact only the 10% of the known 1800 radio pulsars are radio MSPs. Is not surprising, that MSP are overabundant in GCs respect to Galactic field, since in the Galactic Disk, MSPs can only form through the evolution of primordial binaries, and only if the binary survives to the supernova explosion which lead to the neutron star formation. On the other hand, the extremely high stellar density in the core of GCs, relative to most of the rest of the Galaxy, favors the formation of several different binary systems, suitable for the recycling of NSs (Davies at al. 1998). In this thesis we will present the properties two millisecond pulsars companions discovered in two globular clusters, the Helium white dwarf orbiting the MSP PSR 1911-5958A in NGC 6752 and the second case of a tidally deformed star orbiting an eclipsing millisecond pulsar, PSR J1701-3006B in NGC6266

X-Ray studies of the physics of matter around super-massive black-holes in nearby Seyfert galaxies

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 properties of low-luminosity sources to the ones of higher luminosity and, thus, it was also used to test the emission mechanism models; finally, the XMM–Newton sample was extracted from the X-CfA sample so as to ensure a truly unbiased and well defined sample of objects to define the average properties of Seyfert galaxies. Taking advantage of the broad-band coverage of the BeppoS AX MECS and PDS instruments (between ~2-100 keV), I infer the average X-ray spectral propertiesof nearby Seyfert galaxies and in particular the photon index (~1.8), the high-energy cut-off (~290 keV), and the relative amount of cold reflection (~1.0). Moreover the unified scheme for active galactic nuclei was positively tested. The distribution of isotropic indicators used here (photon index, relative amount of reflection, high-energy cut-off and narrow FeK energy centroid) are similar in type I and type II objects while the absorbing column and the iron line equivalent width significantly differ between the two classes of sources with type II objects displaying larger absorbing columns. Taking advantage of the XMM–Newton and X–CfA samples I also deduced from measurements that 30 to 50% of type II Seyfert galaxies are Compton thick. Confirming previous results, the narrow FeK line is consistent, in Seyfert 2 galaxies, with being produced in the same matter responsible for the observed obscuration. These results support the basic picture of the unified model. Moreover, the presence of a X-ray Baldwin effect in type I sources has been measured using for the first time the 20-100 keV luminosity (EW proportional to L(20-100)^(−0.22±0.05)). This finding suggests that the torus covering factor may be a function of source luminosity, thereby suggesting a refinement of the baseline version of the unifed model itself. Using the BeppoSAX sample, it has been also recorded a possible correlation between the photon index and the amount of cold reflection in both type I and II sources. At a first glance this confirms the thermal Comptonization as the most likely origin of the high energy emission for the active galactic nuclei. This relation, in fact, naturally emerges supposing that the accretion disk penetrates, depending to the accretion rate, the central corona at different depths (Merloni et al. 2006): the higher accreting systems hosting disks down to the last stable orbit while the lower accreting systems hosting truncated disks. On the contrary, the study of the well defined X–C f A sample of Seyfert galaxies has proved that the intrinsic X-ray luminosity of nearby Seyfert galaxies can span values between 10^(38−43) erg s^−1, i.e. covering a huge range of accretion rates. The less efficient systems have been supposed to host ADAF systems without accretion disk. However, the study of the X–CfA sample has also proved the existence of correlations between optical emission lines and X-ray luminosity in the entire range of L_(X) covered by the sample. These relations are similar to the ones obtained if high-L objects are considered. Thus the emission mechanism must be similar in luminous and weak systems. A possible scenario to reconcile these somehow opposite indications is assuming that the ADAF and the two phase mechanism co-exist with different relative importance moving from low-to-high accretion systems (as suggested by the Gamma vs. R relation). The present data require that no abrupt transition between the two regimes is present. As mentioned above, the possible presence of an accretion disk has been tested using samples of nearby Seyfert galaxies. Here, to deeply investigate the flow patterns close to super-massive black-holes, three case study objects for which enough counts statistics is available have been analysed using deep X-ray observations taken with XMM–Newton. The obtained results have shown that the accretion flow can significantly differ between the objects when it is analyzed with the appropriate detail. For instance the accretion disk is well established down to the last stable orbit in a Kerr system for IRAS 13197-1627 where strong light bending effect have been measured. The accretion disk seems to be formed spiraling in the inner ~10-30 gravitational radii in NGC 3783 where time dependent and recursive modulation have been measured both in the continuum emission and in the broad emission line component. Finally, the accretion disk seems to be only weakly detectable in rk 509, with its weak broad emission line component. Finally, blueshifted resonant absorption lines have been detected in all three objects. This seems to demonstrate that, around super-massive black-holes, there is matter which is not confined in the accretion disk and moves along the line of sight with velocities as large as v~0.01-0.4c (whre c is the speed of light). Wether this matter forms winds or blobs is still matter of debate together with the assessment of the real statistical significance of the measured absorption lines. Nonetheless, if confirmed, these phenomena are of outstanding interest because they offer new potential probes for the dynamics of the innermost regions of accretion flows, to tackle the formation of ejecta/jets and to place constraints on the rate of kinetic energy injected by AGNs into the ISM and IGM. Future high energy missions (such as the planned Simbol-X and IXO) will likely allow an exciting step forward in our understanding of the flow dynamics around black holes and the formation of the highest velocity outflows.

A panchromatic study of stellar populations in Galactic Globular Clusters

The aim of this Thesis is to investigate (i) how common the bimodal Blue Straggler Stars (BSS) radial distribution is in stellar clusters and (ii) which are the physical processes that can produce this bimodality. We discuss possible relations between the properties of the BSS radial distribution and the dynamical state of the hosting clusters by making use of dynamical models and simulations. When relevant, we also discuss the possible links with some cluster "anomalies" and the effects of a massive object (like Imtermediate Mass Black Hole) in the cluster center. To this purpose we present the observational multiwavelength studies of the BSS populations and their radial distributions in 5 GGCs: M5, M55, M2, NGC 2419 and NGC 6388.

Emissions of volatile organic compounds from tropical savanna vegetation and biomass burning

This dissertation focuses on characterizing the emissions of volatile organic compounds (VOCs) from grasses and young trees, and the burning of biomass mainly from Africa and Indonesia. The measurements were performed with a proton-transfer-reaction mass spectrometer (PTR-MS). The biogenic emissions of tropical savanna vegetation were studied in Calabozo (Venezuela). Two field campaigns were carried out, the first during the wet season (1999) and the second during the dry season (2000). Three grass species were studied: T. plumosus, H. rufa and A. canescens, and the tree species B. crassifolia, C. americana and C. vitifolium. The emission rates were determined with a dynamic plant enclosure system. In general, the emissions increased exponentially with increasing temperature and solar radiation. Therefore, the emission rates showed high variability. Consequently, the data were normalized to a standard temperature of 30°C, and standard emission rates thus determined allowed for interspecific and seasonal comparisons. The range of average daytime (10:00-16:00) emission rates of total VOCs measured from green (mature and young) grasses was between 510-960 ngC/g/h. Methanol was the primary emission (140-360 ngC/g/h), followed by acetaldehyde, butene and butanol and acetone with emission rates between 70-200 ngC/g/h. The emissions of propene and methyl ethyl ketone (MEK) were <80 ngC/g/h, and those of isoprene and C5-alcohols were between 10-130 ngC/g/h. The oxygenated species represented 70-75% of the total. The emission of VOCs was found to vary by up to a factor of three between plants of the same species, and by up to a factor of two between the different species. The annual source of methanol from savanna grasses worldwide estimated in this work was 3 to 4.4 TgC, which could represent up to 12% of the current estimated global emission from terrestrial vegetation. Two of the studied tree species, were isoprene emitters, and isoprene was also their primary emission (which accounted for 70-94% of the total carbon emitted) followed by methanol and butene + butanol. The daytime average emission rate of isoprene measured in the wet season was 27 mgC/g/h for B. crassifolia, and 123 mgC/g/h for C. vitifolium. The daytime emissions of methanol and butene + butanol were between 0.3 and 2 mgC/g/h. The total sum of VOCs emission measured during the day in the wet season was between 30 and 130 mgC/g/h. In the dry season, in contrast, the methanol emissions from C. vitifolium saplings –whose leaves were still developing– were an order of magnitude higher than in the wet season (15 mgC/g/h). The isoprene emission from B. crassifolia in the dry season was comparable to the emission in the wet season, whereas isoprene emission from C. vitifolium was about a factor of three lower (~43 mgC/g/h). Biogenic emission inventories show that isoprenoids are the most prominent and best-studied compounds. The standard emission rates of isoprene and monoterpenes of the measured savanna trees were in the lower end of the range found in the literature. The emission of other biogenic VOCs has been sparsely investigated, but in general, the standard emissions from trees studied here were within the range observed in previous investigations. The biomass burning study comprised the measurement of VOCs and other trace-gas emissions of 44 fires from 15 different fuel types, primarily from Africa and Indonesia, in a combustion laboratory. The average sum of emissions (excluding CO2, CO and NO) from African fuels was ~18 g(VOC)/kg. Six of the ten most important emissions were oxygenated VOCs. Acetic acid was the major emission, followed by methanol and formaldehyde. The emission of methane was of the same order as the methanol emission (~5 g/kg), and that of nitrogen-containing compounds was ~1 g/kg. An estimate of the VOC source from biomass burning of savannas and grasslands worldwide suggests that the sum of emissions is about 56 Tg/yr, of which 34 Tg correspond to oxygenated VOCs, 14 Tg to unsaturated and aromatic compounds, 5 Tg to methane and 3 Tg to N-compounds. The estimated emissions of CO, CO2 and NO are 216, 5117 and 9.4 Tg/yr, respectively. The emission factors reported here for Indonesian fuels are the first results of laboratory fires using Indonesian fuels. Acetic acid was the highest organic emission, followed by acetol, a compound not previously reported in smoke, methane, mass 97 (tentatively identified as furfural, dimethylfuran and ethylfuran), and methanol. The sum of total emissions of Indonesian fuels was 91 g/kg, which is 5 times higher than the emissions from African fuels. The results of this study reinforces the importance of oxygenated compounds. Due to the vast area covered by tropical savannas worldwide, the biogenic and biomass burning emission of methanol and other oxygenated compounds may be important for the regional and even global tropospheric chemistry.

Chemical and kinematical properties of Blue Straggler stars in Galactic globular clusters

Blue straggler stars (BSSs) are brighter and bluer (hotter) than the main-sequence (MS) turnoff and they are known to be more massive than MS stars.Two main scenarios for their formation have been proposed:collision-induced stellar mergers (COL-BSSs),or mass-transfer in binary systems (MT-BSSs).Depleted surface abundances of C and O are expected for MT-BSSs,whereas no chemical anomalies are predicted for COL-BSSs.Both MT- and COL-BSSs should rotate fast, but braking mechanisms may intervene with efficiencies and time-scales not well known yet,thus preventing a clear prediction of the expected rotational velocities.Within this context,an extensive survey is ongoing by using the multi-object spectrograph FLAMES@VLT,with the aim to obtain abundance patterns and rotational velocities for representative samples of BSSs in several Galactic GCs.A sub-population of CO-depleted BSSs has been identified in 47 Tuc,with only one fast rotating star detected.For this PhD Thesis work I analyzed FLAMES spectra of more than 130 BSSs in four GCs:M4,NGC 6397,M30 and ω Centauri.This is the largest sample of BSSs spectroscopically investigated so far.Hints of CO depletion have been observed in only 4-5 cases (in M30 and ω Centauri),suggesting either that the majority of BSSs have a collisional origin,or that the CO-depletion is a transient phenomenon.Unfortunately,no conclusions in terms of formation mechanism could be drawn in a large number of cases,because of the effects of radiative levitation. Remarkably,however,this is the first time that evidence of radiative levitation is found in BSSs hotter than 8200 K.Finally, we also discovered the largest fractions of fast rotating BSSs ever observed in any GCs:40% in M4 and 30% in ω Centauri.While not solving the problem of BSS formation,these results provide invaluable information about the BSS physical properties,which is crucial to build realistic models of their evolution.

Cosmic-Lab: Optical companions to binary Millisecond Pulsars

Millisecond Pulsars (MSPs) are fast rotating, highly magnetized neutron stars. According to the "canonical recycling scenario", MSPs form in binary systems containing a neutron star which is spun up through mass accretion from the evolving companion. Therefore, the final stage consists of a binary made of a MSP and the core of the deeply peeled companion. In the last years, however an increasing number of systems deviating from these expectations has been discovered, thus strongly indicating that our understanding of MSPs is far to be complete. The identification of the optical companions to binary MSPs is crucial to constrain the formation and evolution of these objects. In dense environments such as Globular Clusters (GCs), it also allows us to get insights on the cluster internal dynamics. By using deep photometric data, acquired both from space and ground-based telescopes, we identified 5 new companions to MSPs. Three of them being located in GCs and two in the Galactic Field. The three new identifications in GCs increased by 50% the number of such objects known before this Thesis. They all are non-degenerate stars, at odds with the expectations of the "canonical recycling scenario". These results therefore suggest either that transitory phases should also be taken into account, or that dynamical processes, as exchange interactions, play a crucial role in the evolution of MSPs. We also performed a spectroscopic follow-up of the companion to PSRJ1740-5340A in the GC NGC 6397, confirming that it is a deeply peeled star descending from a ~0.8Msun progenitor. This nicely confirms the theoretical expectations about the formation and evolution of MSPs.

Ricerca dell'emissione alle alte energie da parte delle radio galassie fri e frii

Lo scenario di unificazione degli AGN caratterizza le molteplici proprietà di questi oggetti in termini del differente angolo di vista rispetto ad un sistema costituito da un toro oscurante, un disco di accrescimento che alimenta il SMBH e nubi di gas che circondano il buco nero. Circa il 10% degli AGN sono forti sorgenti radio. Questi oggetti, detti AGN Radio-Loud, sono caratterizzati da getti relativistici emessi trasversalmente rispetto al disco di accrescimento e comprendono le radio galassie e i blazar. In accordo con il modello unificato, le radio galassie (MAGN), rappresentano i blazar visti a grandi angoli di inclinazione del getto rispetto alla linea di vista. Nei blazar la radiazione emessa dai getti su scale del pc viene amplificata da effetti relativistici dando origine a spettri piatti con elevata polarizzazione ottica e forte variabilità. Questi oggetti rappresentano le sorgenti più brillanti identificate nel cielo gamma extragalattico. I MAGN, a differenza dei blazar, mostrano spettri ripidi e strutture radio quasi simmetriche. In queste sorgenti, l'effetto del Doppler boosting è meno evidente a causa del grande angolo di inclinazione del getto. In soli 3 mesi di osservazioni scientifiche effettuate con il satellite Fermi è stata rivelata emissione gamma da parte delle radio galassie NGC 1275 e Cen A. I MAGN rappresentano una nuova classe di sorgenti gamma. Tuttavia, il numero di radio galassie rivelate è sorprendentemente piccolo ponendo degli interrogativi sui meccanismi di emissione alle alte energie di questi oggetti. Nel presente lavoro di tesi, si analizzeranno i dati gamma raccolti dal LAT durante i primi 5 anni di osservazioni scientifiche per un campione di 10 radio galassie più brillanti selezionate dai cataloghi B2 e BCS. L'obiettivo principale sarà migliorare la statistica e cercare di comprendere la natura dell'emissione alle alte energie da parte delle radio galassie.

Progetto di un nodo sensore wireless ultra low-power per applicazioni di energy harvesting

Progetto di un nodo wireless, alimentato attraverso l'Energy Harvesting, in grado di misurare la temperatura ambiente ed inviarla ad un sistema ricevente che la visualizzerà su uno schermo LCD.

Oswald Mathias Ungers: Belvederestraße 60. Zu einer neuen Archtektur.

La presente Tesi di Dottorato intende affrontare una lettura critica della Casa in Belvederestraße 60, realizzata dall’architetto Oswald Mathias Ungers (Kaisersesch, 12 luglio 1926 – Köln, 30 settembre 2007), nel 1958-’59 a Köln-Müngersdorf, come studio per sé ed abitazione per la propria famiglia. Questo primo oggetto della ricerca viene considerato evidente espressione delle convinzioni formali e compositive dell’architetto, negli anni Cinquanta e Sessanta. A differenza di altri progetti residenziali coevi ed antecedenti, frutto di un’elaborazione autonoma, la prima casa che costruisce per sé riflette una maggiore libertà di pensiero, dettata dalla coincidenza delle figure di progettista e committente; a ciò si aggiunge anche una precisa volontà dichiarativa ed ideologica. Proprio quest’ultimo aspetto permette di introdurre il secondo oggetto della Tesi: il manifesto “ideologico”, Zu einer neuen Architektur, scritto dallo stesso Oswald Mathias Ungers e da Reinhard Gieselmann, alla fine del 1960; un breve testo che espone, con toni perentori ed inappellabili, il punto di vista dei due architetti nei confronti di un panorama architettonico e critico, caratterizzato da una sterilità di pensiero dilagante, a causa dell’egemonia costruttiva funzionalista. La ricerca indaga quindi le forti reciprocità delle due opere: casa e testo, viste in chiave di “manifesto scritto e manifesto costruito”. Il primo legame tra i due soggetti è senza dubbio la concomitanza temporale, (tra il 1958 ed il 1960) associata ad un rapporto causa-effetto, tale per cui il manifesto viene redatto a difesa delle aspre critiche scaturite dalla pubblicazione della casa sulla rivista Bauwelt. Il secondo nesso è la possibilità di comprendere le accezioni effettive dei termini impiegati nella redazione del testo, attraverso le forme di una delle opere maggiormente personali dell’architetto, estraendone il senso e conferendogli un’immagine architettonica. Si vuole creare così un rapporto biunivoco di traducibilità, dell’architettura nello scritto e della semantica ungersiana in azioni compositive.

Preliminary Evaluation of a Guideline Classification System

In a previous paper, we presented a proposed expansion of the National Guideline Clearing-house (NGC) classification1. We performed a preliminary evaluation of the classification based on 100 guidelines randomly selected from the NGC collection. We found that 89 of the 100 guidelines could be assigned to a single guideline category. To test inter-observer agreement, twenty guidelines were also categorized by a second investigator. Agreement was found to be 40-90% depending on the axis, which compares favorably with agreement among MeSH indexers (30-60%)2. We conclude that categorization is feasible. Further research is needed to clarify axes with poor inter-observer agreement.

Sēfer Yōsîppôn : bi-lešôn askenaz

ḥibbērô ... Yôsēf Ben-Gōryôn hak-kōhēn

Plan de negocios de un bar-restaurante temático musical

El objetivo principal de este trabajo es plantear, analizar y desarrollar un plan de negocios que contenga todos los aspectos operativos,financieros, legales, y de marketing referentes a la empresa: Bar–Restaurante Temático Musical Johnny B. Good. Sus objetivos específicos son: plasmar las bases del negocio para conseguir un crecimiento más sólido a lo largo del tiempo; brindarle a la empresa los conocimientos para actuar adecuadamente en las diferentes situaciones de mercado; posibilitar que la empresa, a través de un análisis económico y financiero, pueda saber cuándo quedarse en el negocio e invertir más, o cuándo retirarse si la situación es desfavorable y presentar el plan de negocios a inversores potenciales.

Espejos, diálogos y reflexiones sobrecomportamientos y determinaciones en la consulta de mediación intercultural con población inmigrante latinoamericana, desde una perspectiva de géneros

El propósito de este documento es llevar a la reflexión y al análisis la experiencia de mediaciónintercultural en el ámbito sanitario en la ciudad de Valencia, España, con usuarios/as migrantesprovenientes de países latinoamericanos. Los principales problemas de salud de esta poblaciónmigrante registrados en los centros sanitarios de atención primaria se concentran en lasáreas de salud sexual y reproductiva, dentro de los que se destacan una alta frecuencia del“madresolterismo”, incremento de las interrupciones voluntarias de embarazos (IVE); difícil usoy baja aceptación de métodos anticonceptivos, tanto por parte de las mujeres como de los varones,y por último, la identificación de relaciones asimétricas en las parejas. Estas circunstancias sonanalizadas desde una perspectiva de géneros para tener un mejor acercamiento a la realidad social.