Dissertations / Theses: 'Astronomical spectroscopy'

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Lee, David. "New techniques in astronomical spectroscopy for 8-m telescopes." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/4847/.

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The purpose of this thesis is to investigate new instrument technology to enhance the capabilities of 8-m telescopes. This thesis first describes the theory, design, construction, and testing of an immersed grating. Immersed gratings can be used to provide R≥ 10(^4) with a multi-object and/or integral field spectrograph on an 8-m telescope. Immersed gratings allow high resolution to be achieved whilst maintaining the required pupil size at a level similar to that on 4-m telescopes. This thesis describes laboratory tests which verify that immersed gratings provide high resolution. The throughput penalty in using an immersed grating is shown to be small with losses due to air-glass reflections, which can be eliminated with antireflection coatings, and metal-dielectric losses. This work demonstrates that immersed gratings provide a good method to reach R=10(^4) (and above) with a multi-aperture spectrograph on an 8-m telescope. The second part of this thesis describes the construction of a microlens-fibre based integral field unit (IFU): the SMIRFS-IFU. This instrument provides a unique J and H-band integral field capability for use with the CGS4 spectrograph at UKIRT. The optical design, assembly, laboratory testing, and telescope commissioning of the SMIRFS-IFU are described. The microlens arrays for use with SMIRFS-IFU were tested in detail and found to provide excellent image quality but with some scattered light. The assembly of the SMIRFS-IFU was achieved with high precision. The overall performance of the SMIRFS-IFU was found to be high and close to theoretical expectations. This instrument demonstrates that the technology of microlenses linked to fibres does provide a means of constructing high performance (i.e. high throughput, high spatial and spectral resolution) IFUs. Integral field spectroscopy is even more important for 8-m telescopes to take advantage of their enormous fight gathering power. The SMIRFS-IFU is an important upgrade to CGS4 to perform high spatial resolution integral field spectroscopy.

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Clampin, Mark. "Investigation of a resistive anode detector for astronomical spectroscopy." Thesis, University of St Andrews, 1986. http://hdl.handle.net/10023/7110.

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A large format two dimensional photon counting detector has been evaluated as a detector for astronomical spectroscopy. The design comprises an 320 photocathode, a tandem MCP gain stage and a circular arc terminated resisitive anode to provide pOSitional coordinates of detected events. The system is run from an LSI 11/23 computer operating under FORTH control. The micro-channel plate operating characteristics and the detector's resolution, quantum efficiency and imaging performance have been studied. The principal areas requiring design improvement are found to be the micro-channel plate gain, processing and photocathode quality. electronic signal The detector has been employed in a observing program on a 0.5 m telescope. Spectra of IAU faint radial velocity standards and the eclipsing binary system s-l Cam have been obtained and analysed to assess the system's performance.

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Oates, Anthony Patrick. "A technique for astronomical spectroscopy with a multi-aperture telescope." Thesis, University of Central Lancashire, 1985. http://clok.uclan.ac.uk/19078/.

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A technique for acquiring spectral line data using a multi-aperture telescope is described. The multi-aperture principle and the criteria which led to the selection of a dispersive spectrometer are discussed. The problem of linking telescope and spectrometer has been solved by incorporating low loss optical fibres and this is also discussed. The problems of automatic data collection, its manipulation, display and storage presented a major research effort which were largely overcome by the use of cheap, digital micro-computers. To achieve rapid and flexible data handling the i.E.E.E. bus was used as the communication medium between control and data collecting micro-computers. In particular a non-standard approach was adopted when implementing specialised interrupt handling routines to deal with data communication, an aspect which forms the central theme of this thesis and is described in chapters three to five inclusive. A discussion relating to data obtained using the system in single fibre mode and to RPCS data obtained at intermediate resolution is presented in chapters six and seven respectively. The former permitted a preliminary determination to be made of both system resolution and the approximate integration times required to undertake a program of stellar emission line work. This is complimentary to that described in the final chapter which discusses the spectra of emission line stars, some of which are accompanied by circumstellar 'shells'. For pre-main sequence stars these shells may ultimately provide conditions favourable for the formation of planetary systems. There are examples of these types of stars to be found in the Northern hemisphere and which are within the detection limit of the system described in this thesis.

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Bounissou, Sophie. "”On-chip” astronomical instrumentation : bringing polarimetric and spectroscopic capabilities to the detector level." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS400.

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Cette thèse étudie la possibilité d'intégrer plusieurs fonctions instrumentales au sein de la matrice de bolomètres pour les observations dans le domaine du sub-millimétrique. Ceci est désormais envisageable grâce aux progrès des micro-technologies.Dans un premier temps, nous avons optimisé le design des pixels polarimétriques inventés pour l'instrument B-BOP du futur observatoire spatial SPICA. Ce travail a notamment permis de quantifier la cross-polarisation (1/1000) et de repenser la géométrie des pixels afin d'obtenir des détecteurs mieux adaptés au rayonnement incident.Cette thèse a également été l'occasion, et ce de manière indépendante à la polarimétrie, de réfléchir à l'intégration de la spectroscopie au sein du plan focal. Pour cela, nous nous sommes orientés vers de l'interférométrie de type Fabry Pérot (FP). Un FP dans un faisceau collimaté présente l'avantage d'être très facilement compatible avec l'imagerie. Toutefois, nous avons choisi d'intégrer le spectromètre au plus près du détecteur (et donc dans le faisceau convergent). Nous avons également initié le développement de FP tout silicium (Si) à haute résistivité afin de réduire les pertes dûes aux miroirs métalliques, conventionnellement utilisés dans nos gammes de longueurs d'onde. Afin d'améliorer les performances spectrales du FP, les miroirs sont fabriqués via un empilement de couches de silicium interposés de vide tels des miroirs de Bragg. Cela permet d'augmenter rapidement le coefficient de réflexion des miroirs sans toutefois en augmenter trop la complexité: une finesse de 215 est, par exemple, attendue à 320 µm pour un FP utilisant des miroirs Si/vide/Si. Ensuite, nous avons étudié le couplage détecteur/FP qui se voit renforcé par la résonance des deux cavités optiques formées par le système complet. Enfin, des calculs ont montré qu'un FP avec une finesse raisonnable (150) mis dans le plan focal ne dégrade que très peu l'imagerie et la spectroscopie.A la fin de cette thèse, plusieurs étalons FP ont été réalisés et ont déjà démontré des propriétés intéressantes: une résolution spectrale de 180 a notamment été obtenue. En plus de cela, les mesures ont montré que le silicium avait une absorption négligeable à 77 K This thesis assesses the potential of gathering several instrumental functions into a bolometer array for sub-millimetric astronomical observations. This possibility is now conceivable thanks to the recent progress made in micro-technologies.First, we optimized the design of polarimetric pixels invented for the B-BOP instrument of the future space observatory SPICA. This work enabled the quantification of the cross-polarization (1/1000) and to rethink the geometry of the pixels in order to obtain detectors better matched to incident radiation.This thesis has also been an opportunity to deal with the integration of spectroscopy within the focal plane, independently from the polarimetry aspect. We accordingly focused on Fabry-Pérot (FP) interferometry, as an FP in a collimated beam can well-suited for imaging. Nonetheless, we chose to integrate the spectrometer closer to the detector (and thus in the convergent beam). We also initiated the development of an FP made from high-resistivity silicon in order to lower the losses due to metallic mirrors, generally used in this range of wavelengths. With the objective to enhance the spectral capabilities of the FP, mirrors are built as a stack of silicon layers, separated by vacuum (Bragg mirrors). This increases the reflectivity of the mirrors while keeping the complexity to a reasonable level : a finesse of 215, for instance, is expected at 320 µm for a FP using Si/vacuum/Si mirrors. As a next step, we studied the detector/FP coupling which is enhanced by the resonance of two optical cavities formed by the whole system. Eventually, calculations showed that an FP with a moderate finesse (150) put in the focal plane barely deteriorates imaging or spectroscopy.By the end of this thesis, several FP etalons have been built and have already demonstrated favorable properties: we obtained a spectral resolution of 180. Moreover, measurements showed that silicon has a negligible absorption at a temperature of 77 K

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Gilbert, James Michael. "New developments in robotic fibre positioning for astronomical multi-object spectroscopy." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:ca88e3e2-cd47-422e-96a7-d644a88176d0.

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This thesis presents two bodies of work, both related to automated optical fibre positioning in highly-multiplexed astronomical instrumentation. Part one concerns the development and prototyping of a pick-and-place fibre positioner for WEAVE, a new 1000-fibre spectrograph for the 4.2 m William Herschel Telescope. This research has helped shape the positioner's final design and has included development of three novel techniques to enhance predicted performance: i) a scheme for automatically calibrating the fibre measurement system; ii) an algorithm for finding the centre of an imaged fibre with superior accuracy and speed; and iii) a robot motion control scheme to greatly reduce field reconfiguration time. Following these developments, and with rigorous testing of the proposed industrial robotic components, it is found that the performance of the positioner is likely to meet WEAVE's scientific requirements. Part two of this thesis presents a new design of piezoelectric motor for 'tilting spine' fibre positioners. Tilting spine technology already allows simultaneous positioning of fibres in high-density fields, but has two significant drawbacks: i) fibres are tilted, resulting in optical losses; and ii) actuators require signal amplitudes of > 100 V, placing performance-degrading limitations on the control system. The new motor has a more efficient mechanism and a drive voltage of just ± 9 V, allowing new control approaches that vastly improve the technology's capabilities. Prototyping has shown a closed-loop positioning accuracy of < 2.8 μm, lower than any other published technique. A 50% reduction in optical loss is shown to be feasible by trading some accuracy for a spine length increase. It follows that any survey using this motor would have a higher signal-to-noise ratio and/or would complete faster than with the existing technology.

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McGee, P. K. "Optical studies in high-energy astrophysics /." Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phm14485.pdf.

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Keller, Luke David. "New devices and techniques for high resolution astronomical spectroscopy and a new study of old stars /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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Welsh, Frederick V. "Scientific application of the Santa Barbara instrument group self-guided spectrograph." Virtual Press, 2004. http://liblink.bsu.edu/uhtbin/catkey/1295146.

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The Santa Barbara Instrument Group self-guided spectrograph is aimed primarily at the advanced amateur astronomer. This study has determined that this instrument is capable of being used for scientific research. A comparison lamp box was built to be used in conjunction with the spectrograph. A test was conducted to determine the accuracy of the grating positioning micrometer. A chart was created to allow the conversion of the micrometer readings to correlate with the position of the low-dispersion grating. To determine the scientific applicability of the spectrograph, it was used to: (1) measure the expansion rate of Nova Sagittarius 2004, (2) look for a 13.9-minute periodicity in the width and position of the H-alpha line of the binary star system X Persei, and (3) to measure the Doppler shift of X Persei. The instrument proved to be capable of being used to determine radial velocities and Doppler shifts. Department of Physics and Astronomy

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Waltham, Nicholas Richard. "The development of a detector system for faint object spectroscopy on the Isaac Newton Telescope." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/6656/.

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The work reported in this thesis describes the development of the CCD instrumentation for the Faint Object Spectrograph on the 2.5m Isaac Newton Telescope at the Observatorio del Roque de los Muchachos, more commonly known as the La Palma Observatory. The Faint Object Spectrograph is a highly efficient, fixed-format CCD spectrograph aimed at low resolution spectrophotometry (15-20 A FWHM) over a wide spectral range (400-1050 nm). Its high throughput, compared with that of more conventional spectrographs, is due to the small number of optical surfaces, and the minimum vignetting which results from, locating the CCD inside the spectrograph camera. A CCD camera system is described which was developed primarily to test and commission the Faint Object Spectrograph, but also to assess the characteristics of the GEC P8603 CCD used In the spectrograph, and optimize its performance for this application. The use of CCDs in astronomy is now commonplace but there still remains some uncertainty as to which aspects of their performance need to be most critically assessed when choosing a device for a particular application. It is argued that it is important to consider not only the obvious characteristics such as quantum efficiency, spectral coverage, readout noise and geometrical format, but also, and particularly at astronomically relevant low-light levels, the consequences of the more subtle properties such as charge transfer efficiency, threshold effects and chip defects. The CCD detector in the Faint Object Spectrograph is located inside the spectrograph camera and needs to be positioned to high accuracy within the optical path. A microprocessor system is described which enables the CCD detector to be aligned remotely from the observer's control console. Finally, the commissioning of the Faint Object Spectrograph on the Isaac Newton Telescope is described, and some of the first results obtained during commissioning are presented in order to illustrate its potential in the field of faint object spectroscopy.

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BECHTOLD, JILL ELEANOR. "HIGH RESOLUTION SPECTROSCOPY OF QUASAR ABSORPTION LINES (INTERGALACTIC MEDIUM, EXTRAGALACTIC, GALAXIES)." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188085.

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This dissertation investigates the properties of the metal-containing absorption lines seen in quasar spectra which have Z(abs) < < Z(em). These systems, which probably originate in the halos of galaxies at high redshift, are then compared to observations of the halo and interstellar medium of the Milky Way. We obtained echelle spectra at the Multiple Mirror Telescope (MMT) of the Z = 1.79 absorption system of the quasar B2 1225+317. The velocity profiles showed complex structure which varied from ion to ion, with ionization and column densities varying from component to component. The relative colums were consistent with the expectations for approximately interstellar abundance, low density material, in equilibrium with the ultraviolet radiation field of a spiral galaxy for λ > 912 A, and the integrated light from QSOs at Z = 1.79 for λ < 912 A. The aggregate C IV profile has a width of about 450 km/sec, larger than that expected for a single galaxy halo, however. With the MMT spectrograph and echellette grating, and MMT echelle, we studied the properties of three other redshift systems of B2 1225+317, which are optically thin at the Lyman limit, but have saturated Lyman alpha, and unlike material in the Milky Way, have strong C IV and no detectable C II. In some cases Si III and Si IV are weakly detected. Constructing photoionization models, we derive low total densities, cloud diameters on the order of a few kiloparsecs, and abundances which are consistent with the interstellar values. We calculated the contribution of quasars to the UV radiation field as a function of redshift. The calculated field depends on a number of uncertain assumptions, which were varied in order to estimate their effect on the result. Finally, we discuss an important input into these calculations, the continuum spectral energy distribution for quasars, with particular attention to the extreme ultraviolet.

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Rojas, Randall R. "Photometric and spectroscopic properties of void galaxies in the Sloan Digital Sky Survey /." Click for resource, 2004. http://dspace.library.drexel.edu/handle/1860/270.

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MacQueen, Phillip J. "Solid-state image detector development : a linear diode array for astronomical spectroscopy." Thesis, University of Canterbury. Astronomy, 1986. http://hdl.handle.net/10092/8071.

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Future spectroscopic observational programmes at Mount John University Observatory require the ability to acquire spectra with significantly higher spectrophotometric accuracy and geometrical stability than can currently be achieved. Therefore a solid-state linear-diode-array image detector system has been designed and developed for use with the MJUO échelle spectrograph. A review of those electromechanical design techniques of significance to astronomical instrumentation is presented. Their application is exemplified with a complete electromechanical design for the detector, which is found to allow each electronic sub-system implemented within that design to achieve its theoretical level of performance. The requirements for the video processing electronics of a solid-state image detector are explicitly developed, and are used to design the electronics for this detector. Subtle sources of electronic instability which can appear as noise or base-line shifts are identified and controlled in this design. In particular, differential non-linearity is identified in an existing preamplifier design, and so an alternative design is implemented. The readout noise of the entire detector system is measured to be 200 e-/h pairs for a noiseless signal source of zero impedance to ground. This increases to 350 e-/h pairs when the impedance of this source is equal to that of the diode array, due to an additional noise contribution of 290 e-/h pairs. The net readout noise with the RL936F/30 diode array is 450 e-/h pairs, which is the quadratic sum of the detector system noise with the two 210 e-/h pair samples of diode capacitance thermodynamic noise. Thus the diode array is not found to contribute any noise in excess of its theoretical thermodynamic noise. A temperature controller is developed for use with sensors which are cooled in cryogenic dewars. A short term control precision of 1.6 mK r.m.s. is achieved which is entirely due to the theoretical noise of the temperature sensor. The long term precision over all operating conditions is ±20 mK, which is dependent on the design of the dewar. The hardware and software which provide interactive instrument control and data reduction are described. In particular, they provide for flexible control of the detector sub-systems during data acquisition and testing, and enable a high level of data reduction to be undertaken while the detector is integrating. An observational programme has been carried out with this detector sys tern on the southern RS CVn sys tern HR4492. Radial velocity measurements with a precision of ±0.5 km s-¹ have enabled a new ephemeris for the binary motion to be determined, namely HJD = 2446317.5 ± 21.82E. It is used to interpret Hα line profile variations in terms of probable mass transfer within the system.

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Ren, Deqing. "New techniques of multiple integral field spectroscopy." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/3800/.

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The work of this thesis is to investigate new techniques for Integral Field Spectroscopy (IPS) to make the most efficient use of modem large telescopes. Most of the work described is aimed at the FMOS for the SUBARU 8m telescope. Although this is primarily a system for Multiple Object Spectroscopy (MOS) employing single fibres, there is an option to include a multiple-IFS (MIPS) system. Much of this thesis is therefore aimed at the design and prototyping of critical systems for both the IPS and MOS modes of this instrument. The basic theory of IFU design is discussed first. Some particular problems are described and their soludons presented. The design of the MIPS system is described together with the construction and testing of a prototype deployable IFU. The assembly of the pickoff/fore-optics, microlens array and fibre bundle and their testing are described in detail. The estimated performance of the complete module is presented together with suggestions for improving the system efficiency which is currently limited by the performance of the microlens array. The prototyping of the MIPS system is supported by an extensive programme of testing of candidate microlens arrays. Another critical aspect of the instrument is the ability to disconnect the (IPS and MOS) fibre input which is installed on a removable prime focus top-end ring from the spectrographs which are mounted elsewhere on the telescope. This requires high-performance multiple fibre connectors. The designs of connectors for the MOS and IPS modes are described. Results from the testing of a prototype for the MOS mode are presented. This work is supported by a mathematical model of the coupling efficiency which takes into account optical aberrations and alignment errors. The final critical aspect of FMOS which has been investigated is the design of the spectrographs. The baseline system operates in the near-infrared (NIR) but an additional visible channel is an option. Efficient designs for both the visible and NIR systems are presented. The design of the NIR spectrograph presents challenges in the choice of materials for the doublet and triplet lenses employed. The choice of material and the combinations in which they can be used are described. This thesis shows that all these critical aspects of FMOS have good solutions that will result in good performance of the whole instrument. For the multiple IFU system, the prototype demonstrates acceptable performance which can be made excellent by the use of a better microlens array. The multiple fibre connector prototype already indicates excellent performance. Finally, the spectrograph designs presented should result in high efficiency and good image quality.

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Chan, Yat-ping Carl, and 陳一平. "Installation of direct-vision prism spectroscopy into a 32CM cassegrain telescope." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31220472.

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Chan, Yat-ping Carl. "Installation of direct-vision prism spectroscopy into a 32CM cassegrain telescope /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20357680.

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Jones, Scott Curtis, and University of Lethbridge Faculty of Arts and Science. "Astronomical submillimetre Fourier transform spectroscopy from the Herschel Space Observatory and the JCMT." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Physics & Astronomy, c2010, 2010. http://hdl.handle.net/10133/2486.

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Fourier transform spectroscopy (FTS) is one of the premier ways to collect source information through emitted radiation. It is so named because the principal measurement technique involves the analysis of spectra determined from the Fourier transform of a time-domain interference pattern. Given options in the field, many space- and ground-based instruments have selected Fourier transform spectrometers for their measurements. The Herschel Space Observatory, launched on May 14, 2009, has three on-board instruments. One, SPIRE, comprises a FTS paired with bolometer detector arrays. SCUBA-2 (Submillimetre Common User Bolometer Array) and FTS-2 have recently been commissioned and will be mounted within the collecting dish of the James Clerk Maxwell Telescope by Fall, 2010. The use of FTS in these two observatories will be examined. While work towards each project is independently useful, the thesis is bound by the commonality between the two, as each seeks similar answers from vastly different viewpoints. xvii, 123 leaves : ill. (some col.) ; 29 cm

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Larson, Ana Marie. "A study of high quality, near-infrared spectra of eight spectral type of K stars: precise radial velocities, chromospheric emission, and fundamental stellar parameters." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21938.pdf.

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Ogden, Chad E. "A prototype visible to near-infrared spectrograph for the CHARA array a long-baseline stellar interferometer /." unrestricted, 2005. http://etd.gsu.edu/theses/available/etd-11282005-121433/.

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Thesis (Ph. D.)--Georgia State University, 2005. Theo A. ten Brummelaar, committee chair; Brian D. Thoms, Todd J. Henry, William G. Bagnuolo, Douglas R. Gies, Harold A. McAlister, committee members. Author's name from thesis t.p. Electronic text (548 p. : ill.) : digital, PDF file. Description based on contents viewed June 27, 2007; title from title screen. Includes bibliographical references (p. 539-548).

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Faloon, Ashley J. 1983. "A spectroscopic survey of the supercluster RCS2319+00 /." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111567.

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This thesis presents the results of a spectroscopic survey of the RCS2319+00 supercluster field using the VIMOS instrument on the 8-meter Very Large Telescope. This system is a rare and massive high-redshift structure, comprising at least three galaxy clusters at z = 0.9, separated by less than 3 Mpc, and is one of the few examples of the progenitors of present-day massive galaxy clusters. We measure 638 new redshifts from a sample of 1134 target sources, 49 of which are consistent with the supercluster redshift. Redshifts are also obtained for 24 radio galaxies within the field, with 6 of these identified as cluster members. We combine the VIMOS redshift catalogue with the data analyzed by Gilbank et al. (2008) from the IMACS spectrograph on the 6-meter Magellan telescope for a total of 1051 redshifts over an area of &sim; 30 x 30 square arcminutes, with 94 spectroscopically confirmed supercluster members. From this combined data set the mean spectroscopic redshifts of the three galaxy clusters were refined and found to be zspec = 0.9056, 0.9041, and 0.9047 for clusters A, B, and C respectively. A new velocity dispersion of sigmav = (1300 +/- 410) km S-1 was calculated for the largest component cluster, A, and was used to estimate a new cluster membership redshift range of 0.8857 ≤ z ≤ 0.9239. These data will facilitate further scientific study of RCS2319+00 and will shed light on the evolution of massive clusters, hierarchical structure formation, and galaxy evolution. In combination with other spectroscopy this data will allow: the full extent of the supercluster and its substructure in redshift space to be traced; a determination of the dynamical masses of the individual sub-clusters; and a study of the galaxy population within the structure, in particular the star-forming galaxies and active galactic nuclei as traced by radio and infrared emission.

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O'Donnell, D. V. (Daniel V. ). 1983. "An infrared survey of galaxy clusters with the Spitzer Space Telescope /." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111564.

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We present the observations, reduction and preliminary analysis of a sample of 45 mid-to-high redshift galaxy clusters imaged with the Spitzer Space Telescope's MIPS camera at 24 ~m and selected from the Red Sequence Cluster Survey. The purpose of the data set is motivated by a broad review of studies into the evolutionary trends of galaxy clusters and their constituent galaxy populations, focusing specifically on recent results that indicate clusters are environmental drivers of dusty starburst and active galactic nuclei activity. To accommodate the large amount of data in hand, we have constructed an extensive data reduction pipeline for the MIPS data and describe its development and output in detail. Using the resulting catalogues for introductory analysis, we find strong evidence for an excess luminous infrared galaxy population in galaxy clusters at high redshift and discuss the implications of this discovery in terms of cluster evolution and motivate future work.

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Mu, Bo. "Unsupervised spectral classification of astronomical X-ray sources based on independent component analysis /." Online version of thesis, 2007. http://hdl.handle.net/1850/5870.

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PENNING, WILLIAM ROY. "INVESTIGATIONS OF LONG-PERIOD DQ HERCULIS STARS." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/188161.

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The magnetic rotator model has long been the favored explanation for coherent photometric modulations in the DQ Herculis class of cataclysmic variables. However, to date, all evidence supporting this model has been of the indirect variety. Unlike their synchronously rotating cousins, the AM Herculis objects, DQ Herculis stars have not yet been discovered to emit polarized radiation. Therefore, in light of this crucial lack, the evidence used to place these objects in the magnetic cataclysmic variable category has been strictly circumstantial, based primarily on the coherence of the photometric periodicities. In this work, time-resolved spectroscopy of four long-period DQ Herculis stars is performed. In addition, two of the same objects are observed with a new, sensitive circular polarimeter. Chapters II and III describe these observations and the results of each. To summarize, coherent variations in the wavelength of emission lines were found with the spectroscopic observations. A model is put forth, explaining this phenomenon as being due to varying illumination from a bright spot on the primary. This, of course, adds strength to the magnetic rotator model. Secondly, circular polarization was definitely found in one object studied, and possibly in a second. Therefore, for the first time, there is direct evidence of the magnetic nature of these binaries. In Chapter IV, the model of the rotating bright spot illuminating the disk is explored in further detail, including modeling with a minicomputer. Afterward, a problem brought out by the low polarization coupled with large amplitude photometric variations and a cool spectrum is investigated, namely, is it possible to produce large amounts of cyclotron radiation without producing large amounts of circular polarization? The results tend to show that, for a large emitting area, the answer is yes. Chapter V is a summary of the rest of the work.

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Jeffers, Sandra Victoria. "Surface brightness distributions of late-type stars." Thesis, University of St Andrews, 2005. http://hdl.handle.net/10023/12941.

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The aim of this work has been to increase our understanding of the surface brightness distributions of late-type stars through Doppler imaging and eclipse mapping techniques. Combining spectroscopic and photometric observations with the technique of Doppler Imaging, I have reconstructed surface images of the G2V star He 699 (for 08 October 2000), which show high latitude and polar structures. In the case of the KOV star AB Dor, the Doppler images for January 1992 and November 1993 show a large polar cap with small dark features also present at intermediate to high latitudes. As the phase sampling of the observations was insufficient to apply the sheared-image method it was not possible to detect any differential rotation. In the second part of my thesis I determine the surface brightness distribution of the primary component of the RS CVn eclipsing binary SV Cam. I have used extrapolated size distributions of sunspots to an active star to synthesize images of stellar photospheres with high spot filling factors. The resulting surface images, reconstructed with the Maximum Entropy eclipse mapping technique, show large spurious spot features at the quadrature points. It is concluded that two-spot modelling or chi-squared minimisation techniques are more susceptible to spurious structures being generated by systematic errors, arising from incorrect assumptions about photospheric surface brightness, than simple Fourier analysis of the light-curves. Spectrophotometric data from 9 HST orbits, observed in November 2001, have been used to eclipse-map the primary component of SV Cam. In combination with its HIPPAR- COS parallax it is found that the surface flux in the eclipsed low-latitude region is about 30% lower than computed from the best fitting PHOENIX model atmosphere. This flux deficit can only be accounted for if about a third of the primary's surface is covered with unresolved spots. However, when the spottedness from the eclipsed region is applied to the entire surface of the primary star, there still remains an unaccounted flux deficit. The remaining flux deficit is explained by the presence of a large polar spot extending down to latitude 48+/-6 deg. When the Maximum Entropy eclipse mapping technique is used to fit SV Cam's lightcurve, the observed minus computed residuals show strong spurious peaks at the quadrature points. It is only possible to reduce these peaks with the addition of a polar cap and the reduction of the primary star's temperature, to account for the star being peppered with unresolvable spots. Motivated by this result we investigate the limb darkening of the primary component of SV Cam. The wavelength dependence of the limb darkening is analysed by sub-dividing the HST lightcurve into 10 bands of equal emission flux. Flux variations between the first and fourth contact of the primary eclipse indicate that the limb darkening decreases towards longer wavelengths, in accordance with published limb darkening laws. Comparing fits of ATLAS and PHOENIX model atmospheres we find a wavelength dependence of the best fitting model. Due to its smooth cutoff at the stellar limb, the spherical geometry of the PHOENIX model atmosphere gives the best fit during partial eclipse. Between the second and third contact the difference between spherical and plane-parallel geometry is less important.

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Hernandez, Eloy [Verfasser], Martin M. [Akademischer Betreuer] Roth, Klaus [Akademischer Betreuer] Petermann, and Andreas [Akademischer Betreuer] Kelz. "Numerical simulations in multimode fibres for astronomical spectroscopy / Eloy Luis Hernandez Anguizola ; Martin M. Roth, Klaus Petermann, Andreas Kelz." Potsdam : Universität Potsdam, 2020. http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-472363.

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Hernandez, Eloy [Verfasser], Martin M. Akademischer Betreuer] Roth, Klaus [Akademischer Betreuer] [Petermann, and Andreas [Akademischer Betreuer] Kelz. "Numerical simulations in multimode fibres for astronomical spectroscopy / Eloy Luis Hernandez Anguizola ; Martin M. Roth, Klaus Petermann, Andreas Kelz." Potsdam : Universität Potsdam, 2020. http://d-nb.info/1219579300/34.

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Hernandez, Anguizola Eloy Luis [Verfasser], Martin M. [Akademischer Betreuer] Roth, Klaus [Akademischer Betreuer] Petermann, and Andreas [Akademischer Betreuer] Kelz. "Numerical simulations in multimode fibres for astronomical spectroscopy / Eloy Luis Hernandez Anguizola ; Martin M. Roth, Klaus Petermann, Andreas Kelz." Potsdam : Universität Potsdam, 2020. http://d-nb.info/1219579300/34.

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Chantzos, Johanna [Verfasser], and Paola [Akademischer Betreuer] Caselli. "High resolution spectroscopy of molecules of astrophysical interest and radio astronomical observations of star forming regions / Johanna Chantzos ; Betreuer: Paola Caselli." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1209472864/34.

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34

Leigh, Christopher. "The detection and characterisation of extrasolar planets." Thesis, University of St Andrews, 2004. http://hdl.handle.net/10023/12943.

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Since the discovery of 51 Pegasi b in 1995, continued observations have indirectly identified over 110 planetary objects. These Jupiter-mass objects cause their host star to "wobble" slightly about the common centre-of-mass of the system, which is detectable as radial motion in high-precision Doppler spectroscopy. Of the known planets, approximately 20% are found to orbit within 0.1 AU of the star, whilst the transit of HD209458 has inferred the gas-giant nature of these close-in extrasolar giant planets (CEGPs). The discovery of CEGPs has produced a wave of speculative theory as to the exact nature of these objects, and how they came to exist so close to their parent star. Our spectroscopic technique provides a method of achieving the direct detection of a CEGP atmosphere, the results of which will allow us to test emerging models that aim to predict the atmospheric nature of CEGPs and may provide additional information on the orbital inclination and mass of the planet. We start with a historical review of the field of extrasolar planets, followed by an introduction to the fundamental concepts which underpin the reflection of starlight from a planet's surface. We then investigate the prospects of detecting such a reflection, before detailing the technique we have devised and applied here to two known CEGP hosts. In the first instance, r Bootis, we combined observations at the 4.2-m William Herschel telescope in 1998, 1999 and 2000. The dataset comprised 893 high-resolution échelle spectra with a total integration time of 75hr 32min spanning 17 nights. We establish an upper limit on the planet's geometric albedo p < 0.39 (at the 99.9% significance level) at the most probable orbital inclination i ~ 36 deg, assuming a grey albedo, a Venus-like phase function and a planetary radius Rp - 1.2RJup. Although a weak candidate signal appears near to the most probable radial velocity amplitude, its statistical significance is insufficient for us to claim a detection with any confidence. In the second instance, HD75289, 4 nights of VLT(UT2)/UVES observations were secured in 2003 Jan, yielding 684 high-resolution spectra with a total integration time of 26 hours. We establish an upper limit on the planet's geometric albedo p < 0.12 (to the 99.9% significance level) at the most probable orbital inclination i ~/= 60 deg, assuming a grey albedo, a Venus-like phase function and a planetary radius Rp = 1.6RJup. In both cases, we are able to rule out some combinations of the predicted planetary radius and atmospheric albedo models with high, reflective cloud decks.

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Neyskens, Pieter. "Exploring S stars: stellar parameters, abundances and constraints on the s-process from a new grid of model atmospheres." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209358.

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More than 80% of the stars in the Universe are expected to have initial masses below eight to ten times the mass of our sun. These low mass stars, including our sun, become cool red giants during one of the final evolutionary stages of their life: the Asymptotic Giant Branch (or AGB) phase. AGB stars are among the main producers of carbon and heavy (s-process) elements in the Universe. These elements are synthesized inside the star and mixed to the stellar atmosphere where stellar winds are responsible for the loss of more than 50% of the stellar mass, hence, AGB stars are strong polluters of the interstellar medium. The ejected material can clump together into dusty particles which may serve as ingredients for the birth of new stars and planets. When most of the AGB stellar envelope is lost, the AGB star stops releasing nuclear energy from interior processes and swaps its giant face for a planetary nebulae look, whereafter it fades away as a white dwarf.The dredge-up of carbon and s-process elements into the AGB atmosphere causes an important chemical anomaly among them: initial oxygen-rich stars (M stars) are transformed into carbon-rich stars (C stars). As a consequence, a group of oxygen-rich AGB stars exists which makes the transition between M and C stars. These transition stars are classified as S.Although AGB stars are identified as producers of heavy elements, their nucleosynthesis and mixing processes are weakly constrained due to large uncertainties on their estimated temperature, gravity and chemical composition. Stronger constraints on the atmospheric parameter space, hence interior processes, of AGB stars can be obtained by investigating the atmosphere of S stars. Since they are transition objects on the AGB, they trace the rise of the s-process. S stars are less numerous than C stars, but their optical spectra are brighter making it easier to identify atomic and molecular lines. Therefore, S stars belong to the most interesting objects along the AGB to perform this task.From a practical point of view, the spectra of S stars are extremely difficult to study since they are dominated by different, overlapping molecular bands, and the spectral shape may vary strongly from star to star due to their transition status. Therefore, tailored model atmospheres for S stars are of utmost importance to understand the spectroscopic, and even photometric, changes in terms of variations in the atmospheric parameters. A comparison between the models and observations aims not only at constraining the atmospheric parameter space of S stars, it will also test the reliability of 1D state-of-the-art model atmospheres for such complex stars.From an evolutionary point of view, the S-star family is contaminated with stars who gained their atmospheric enrichment in heavy elements from a companion star. Evidences were found that these binary S stars are not at all located on the AGB, hence, they are labelled as extrinsic S stars while S stars on the AGB are labelled as intrinsic. The difference in evolutionary stages between intrinsic and extrinsic S stars was already found 20 years ago, however, a separation in terms of surface temperature, gravity and chemical composition is not well-established due to the lack of S-star model atmospheres. Such a distinction in atmospheric parameters will facilitate the discovery of these intruders and even help to calibrate stellar evolutionary models of single and binary stars.To achieve these goals, the first step consists in the construction of a grid of model atmospheres for S stars. The grid will be used to quantify the influence of atmospheric parameters on the model structure and emergent flux. These results will be analyzed to derive precise atmospheric parameters of observed S stars, using a set of well-defined photometric and spectroscopic indices. Once the best model atmosphere has been selected for all observed S stars, their atmospheric parameters will be discussed in view of their evolutionary stage. The best-fitting model atmosphere will also be used to derive abundances from spectral syntheses. The abundance profiles are compared with stellar evolution model prediction to constrain nucleosynthesis and mixing processes inside S stars. Derived abundances of unstable elements will be used to estimate, for the first time, the age of AGB stars. Finally, their abundance profile will be discussed as a function of their time spent on the AGB. Doctorat en Sciences info:eu-repo/semantics/nonPublished

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Spencer, Locke Dean, and University of Lethbridge Faculty of Arts and Science. "Spectral characterization of the Herschel SPIRE photometer." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2005, 2005. http://hdl.handle.net/10133/291.

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The European Space Agency's Herschel Space Observatory is comprised of three cryogenically cooled instruments commissioned to explore the far infrared/submillimetre universe. The Spectral and Photometric Imaging REceiver (SPIRE) is one of Herschel's instruments and consists of a three band imaging photometer and a two band imaging spectrometer. Canada is involved in the SPIRE project through provision of instrument development hardware and software, mission flight software, and support personnel. This thesis discusses Fourier transform spectroscopy (FTS) and FTS data processing. A detailed discussion is included on FTS phase correction, with results presented from the optimization of an enhanced Forman phase correction routine developed for this work. This thesis discusses the design, verification, and use of the hardware and software provided by Dr. Naylor's group as it relates to SPIRE verification testing. Results of the photometer characterization are presented. The current status of SPIRE and its future schedule is also discussed. xvii, 239 leaves : ill. (some col.) ; 28 cm.

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Tyas, Luke Martin Graham. "The SALT HRS Spectrograph." Thesis, Durham University, 2012. http://etheses.dur.ac.uk/3492/.

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SALT HRS (Southern African Large Telescope High Resolution Échelle Spectrograph) is a high-resolution, high-efficiency spectrograph for the 11m SALT telescope in Sutherland, South Africa. The initial optical design work was performed at the University of Canterbury, New Zealand. Revisions to the concept, the mechanical design, manufacture, assembly and testing have been handled by the Centre for Advanced Instrumentation, at Durham University in the United Kingdom. SALT HRS is a fibre-fed echelle grating spectrograph with four operational modes: low-, medium- and high-resolution and high-stability modes, having spectral resolutions of R ≈16000, 37000, 67000 and 67000 respectively over a wavelength range of 370-890nm. The instrument is of a dual channel, ‘white pupil’ design, in which the primary mirror acts to collimate light onto a single R4 echelle grating, and also to focus dispersed light to an intermediate focus. A dichroic beam-splitter separates the dispersed light into two separate spectral channels. Spherical pupil mirrors transfer the separated beams via a fold mirror to two wavelength-specific volume-phase holographic gratings (VPHGs) used as cross-dispersers. Cross-dispersed spectra are then imaged by two fully dioptric camera systems onto optimized CCD detectors. This thesis presents the results of the laboratory testing and specification of several critical sub-systems of SALT HRS, as well as the development of key software tools for the design verification and operation at the telescope. In Chapter 1 we first review the technical development of high-resolution spectroscopy and its specific implementation in SALT HRS. In Chapter 2 we develop a comprehensive throughput model of the entire system based on a combination of as-built performance and specific throughput measurements in the laboratory. This is used to make some specific predictions for the on-sky performance of SALT HRS and the magnitude limits for science targets. We also present a graphical exposure time calculator based on these measurements which can be used by an astronomer to plan their observations with SALT HRS. Chapter 3 contains a detailed treatise on the optical fibre system of SALT HRS. Considerations for the use of optical fibres in astronomy are provided, as are details of an optional double scrambler, and the various instrument fibre modes. Extensive measurements of focal ratio degradation (FRD) are also presented, with testing of input beam speed; wavelength; fibre bending; variable pupil mirror illumination; and vacuum tank pressure dependency. The systems for fibre management are reviewed, as is the fibre bundle assembly process. Testing of two further sub-systems is described in Chapter 4. Firstly the long-term stability of the mirror mounting mechanisms is determined. The advantages of cross-dispersion of echelle spectra using volume-phase holographic gratings are then discussed, and the results of diffraction efficiency measurements are given for both red and blue channel gratings. Modern CCD technologies are examined in Chapter 5, and the blue detector is experimentally characterized using photon transfer and quantum efficiency curves. It is also used for an investigation into cosmic ray events in CCDs. Results from shielding the detector using lead are described, as is an attempt to distinguish the source of the events based on their morphology. Finally, Chapter 6 deals with the handling of data produced by SALT HRS. Methods of wavelength calibration of the spectra are discussed, including the use of Thorium-Argon lamps and an iodine absorption cell. The implementation of a Python based quick-look data reduction pipeline is reviewed, with a description of the processes performed. A summary of the thesis is given in Chapter 7.

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Marchi, Magali Conceição de Barros de. "A contribuição de Annie Jump Cannon para a Classificação Espectral de Harvard." Pontifícia Universidade Católica de São Paulo, 2017. https://tede2.pucsp.br/handle/handle/20080.

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Submitted by Filipe dos Santos (fsantos@pucsp.br) on 2017-05-12T13:15:30Z No. of bitstreams: 1 Magali Conceição de Barros de Marchi.pdf: 3776158 bytes, checksum: 69bb899a4464db6873c96be97e829f2e (MD5) Made available in DSpace on 2017-05-12T13:15:30Z (GMT). No. of bitstreams: 1 Magali Conceição de Barros de Marchi.pdf: 3776158 bytes, checksum: 69bb899a4464db6873c96be97e829f2e (MD5) Previous issue date: 2017-03-13 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES Fundação São Paulo - FUNDASP At the end of the 19thand beginning of the 20th there was a technological advance regarding the use of the telescope: the introduction of the photograph to record the images that were observed facilitated the access of the women in an environment previously considered predominantly masculine, the observatory. This study has as its main axis the Spectral Classification developed by Annie Jump Cannon and the importance of spectroscopy in the astronomical studies. The Harvard Spectral Classification, as it became known, is still used today. To understand this period will be shown the main points of the technological evolution of telescopes, the introduction of photography in astronomy, spectroscopy as a tool for astronomical studies and an example of the beginning of the spectral classification of a star made by Cannon No final do séc. XIX e início do séc. XX, houve um avanço tecnológico no que diz respeito ao uso do telescópio: a introdução da fotografia para registro das imagens que eram observadas facilitou o acesso das mulheres em um ambiente até então considerado predominantemente masculino, o observatório. Este estudo tem como eixo principal a Classificação Espectral desenvolvidapor Annie Jump Cannon e a importância da espectroscopia nos estudos astronômicos. A Classificação Espectral de Harvard, como ficou conhecida, ainda é utilizada atualmente. Para compreender esse período serão mostrados os pontos principais da evolução tecnológica dos telescópios, a introdução da fotografia na astronomia, a espectroscopia como ferramenta para estudos astronômicos e um exemplo do início da classificação espectral de uma estrela feita por Cannon

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Casamiquela, Floriach Laia. "Chemical and dynamical analysis of Open Clusters in the context of the Milky Way disc." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/459148.

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This thesis has as a main purpose the determination of the chemical composition of Open Clusters for the study of the chemical gradients in the Galactic disc with: Galactocentric radius, position above the plane, and age. In 3 years and a half we have acquired high-resolution spectra of stars in 18 Open Clusters as a part of the OCCASO survey. We have used three fiber fed high-resolution spectrographs in the Observatorio del Roque de los Muchachos (La Palma, Spain) and the CAHA observatory (Almería, Spain). After a very accurate data reduction we have determined radial velocities, atmospheric parameters (effective temperature, surface gravity) and chemical abundances. Using the derived radial velocities and proper motions from the literature we have done a kinematic study of these clusters in the context of the Galactic disc and the position near the spiral arms. We have obtained radial velocities for OC never studied before with high-resolution spectroscopy: NGC 1907 (vr=2.3+- 0.5 km/s), NGC 6991 (vr=-12.3+-0.6 km/s) and NGC 7245 (vr=-74.0+-1.4km/s). We have computed the possible orbits that the clusters have followed using two models of the Galactic potential: an axysimmetric one, and a model with a bar and spiral arms featuring those of the Milky Way. With this, we have recovered the position of the clusters at birth. We have calculated temperatures, gravities and iron abundances using two different methodologies widely used in the literature. We have made an exhaustive comparison of the behaviour of both methods and the differences obtained among them. We obtained no systematics in effective temperature and surface gravity within the quoted errors, though with a large dispersion in surface gravity. As a sanity check we derived atmospheric parameters from BVI Johnson photometry for the stars from NGC 2420 and NGC 6791. We found systematic differences between spectroscopic and photometric determinations which change with slight variations of the assumed reddening, distance, age and metallicity to compute photometric parameters. Mean uncertainties in the final adopted in temperature and gravity are around 40 K and 0.1 dex. The comparison with literature values gives mean offsets well within uncertainties and dispersions. All these checks provide a study of the precision and accuracy of the obtained results. We have measured abundances of iron-peak elements (Fe, Ni, Cr) and the so-called α-elements (Si, Ca, Ti, Mg, O). From member stars we derive mean Fe cluster abundances with the two methods. We do an extensive star-by-star comparison with literature, showing good agreement. We also derived mean cluster Ni, Cr, Si, Ca and Ti abundances, and its abundance ratios respect to Fe. We see that all the clusters present small dispersions in abundance. The larger ones are 0.03 ([Ni/Fe]), 0.06 ([Cr/Fe]), 0.05 ([Si/Fe]), 0.07 ([Ca/Fe]), 0.05 ([Ti/Fe]) dex, excluding NGC~6791 (for which we have larger errors) We have compared the Galactocentric trend seen with OCCASO clusters with different theoretical models obtaining that the results for the oldest clusters favour a chemo-dynamical model instead of a pure chemical evolution model. Using OCCASO and two complementary samples (40 clusters in total), we have determined new values for the Galactocentric Fe gradient in three age bins, and the age-metallicity relation in four ranges of Galactocentric distance. In particular we have studied NGC 6705 in detail. We have seen that this cluster presents an unexpected α- enhancement for its location in the disc and its young age. We have derived the birth location of this cluster computing the possible orbits that it could have followed in the disc using different models. It seems that its α-enhancement cannot be explained by a very different place of birth of this cluster (i.e. the inner Galaxy), which from our calculations would be at most from a radii of 6.5 kpc. La present tesi té com a objectiu principal la determinació de la composició química de cúmuls oberts per l'estudi del gradient químic en el disc galàctic, tant amb la distancia al centre galàctic, com amb la posició sobre el disc, com amb l'edat. Durant 3 anys i mig s'han adquirit espectres d'alta resolució d'estrelles en 18 cúmuls oberts dins del projecte OCCASO. Així, després d'una acurada reducció de dades, s'han pogut determinar velocitats radials, paràmetres físics (temperatura efectiva, gravetat superficial) i abundàncies químiques. Amb les velocitats obtingudes i moviments propis de la literatura s'ha realitzat un estudi cinemàtic d'aquests cúmuls en relació amb el disc galàctic segons la seva posició a prop dels braços espirals. En concret s'han computat les possibles òrbites que han tingut els cúmuls a partir de dos models del potencial galàctic. S'han calculat temperatures, gravetats i abundàncies de ferro a partir de dues metodologies àmpliament usades a la literatura. S'ha fet una exhaustiva comparació del comportament dels dos mètodes i de les diferències obtingudes, aportant així un estudi de la precisió dels resultats obtinguts. S'han mesurat abundàncies químiques d'elements del pic del ferro (Fe, Ni, Cr) i d'elements anomenats α (Si, Ca, Ti, Mg, O). S'ha comparat la tendència dels cúmuls OCCASO amb diferents models teòrics i s'ha vist que els resultats dels cúmuls vells afavoreixen el model d'evolució químic-dinàmic front d'un model on només es contempli l'evolució química. Amb aquests resultats d'OCCASO i dues mostres complementaries (en total 40 cúmuls), s'han determinat nous valors pel gradient galactocèntric de Fe en tres rangs d'edat, i la relació edat-metal·licitat en quatre rangs de distancia galactocèntrica. En especial, s'ha estudiat en detall el cúmul NGC 6705. Aquest presenta una sobreabundància d'elements α inesperada per la seva localització en el disc i per ser tant jove. S'ha fet una investigació del lloc de procedència d'aquest cúmul computant les òrbites que podria haver seguit el cúmul en el disc amb diferents models. S'ha descartat que provingui d'un lloc intern de la galàxia que pugui explicar aquesta anomalia en els patrons químics. La presente tesis tiene como objetivo principal la determinación de la composición química de cúmulos abiertos para el estudio del gradiente químico en el disco galáctico, tanto con la distancia al centro galáctico, como con la posición sobre el disco, como con la edad. Durante 3 años y medio se han adquirido espectros de alta resolución de estrellas en 18 cúmulos abiertos dentro del proyecto OCCASO. Así, después de una acurada reducción de datos, se ha podido determinar velocidades radiales, parámetros físicos (temperatura efectiva, gravedad superficial) y abundancias químicas. Con los resultados de velocidades radiales y los movimientos propios de la literatura se ha realizado un estudio cinemático de dichos cúmulos según su posición en los brazos espirales. En particular se han computado las órbitas a partir de dos modelos del potencial galáctico. Se han calculado temperaturas, gravedades y abundancias de hierro a partir de dos metodologías. Se ha hecho una exhaustiva comparación del comportamiento de los dos métodos y las diferencias que se obtienen, aportando así un estudio de la precisión de los resultados obtenidos. Se han medido abundancias químicas de elementos del pico del hierro (Fe, Ni, Cr) y elementos llamados α (Si, Ca, Ti, Mg, O). Se ha comparado la tendencia de los cúmulos de OCCASO con diferentes modelos teóricos y se ha visto que los resultados de los cúmulos más viejos favorecen el modelo de evolución químico-dinámico frente a un modelo dónde solo se contemple la evolución química. Con estos resultados de OCCASO y dos muestras complementarias (40 cúmulos en total) se han determinado nuevos valores para el gradiente galactocéntrico de Fe en tres rangos de edad, y la relación edad-metalicidad en cuatro rangos de distancia galactocéntrica. En concreto, se ha estudiado con detalle el cúmulo NGC 6705. Éste presenta una sobreabundancia de elementos α inesperada por su localización en el disco y su joven edad. Se ha hecho una investigación del lugar de procedencia de éste cúmulo mediante diferentes modelos. Se ha descartado que provenga de un sitio interno de la Galaxia que pueda explicar esta anomalía en los patrones químicos.

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Daigle, Olivier. "Spectro-imagerie optique à faible flux et comparaison de la cinématique Hα et HI d'un échantillon de galaxies proches". Aix-Marseille 1, 2010. http://www.theses.fr/2010AIX10141.

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Un nouveau contrôleur de EMCCD (Electron multiplying Charge Coupled Device) est présenté. Il permet de diminuer significativement le bruit qui domine lorsque la puce EMCCD est utilisé pour du comptage de photons: le bruit d'injection de charge. À l'aide de ce contrôleur, une caméra EMCCD scientifique a été construite, caractérisée en laboratoire et testée à l'observatoire du mont Mégantic. Cette nouvelle caméra permet, entre autres, de réaliser des observations de la cinématique des galaxies par spectroscopie de champ intégral par interférométrie de Fabry-Perot en lumière Ha beaucoup plus rapidement, ou de galaxies de plus faible luminosité, que les caméras à comptage de photon basées sur des tubes amplificateurs. Le temps d'intégration nécessaire à l'obtention d'un rapport signal sur bruit donné est environ 4 fois moindre qu'avec les anciennes caméras. Les applications d'un tel appareil d'imagerie sont nombreuses: photométrie rapide et faible flux, spectroscopie à haute résolution spectrale et temporelle, imagerie limitée par la diffraction à partir de télescopes terrestres (lucky imaging), etc. D'un point de vue technique, la caméra est dominée par le bruit de Poisson pour les flux lumineux supérieurs à 0. 002 photon/pixel/image. D'un autre côté, la raie d'hydrogène neutre (HI) à 21 cm a souvent été utilisée pour étudier la cinématique des galaxies. L'hydrogène neutre a l'avantage de se retrouver en quantité détectable au-delà du disque optique des galaxies. Cependant, la résolution spatiale de ces observations est moindre que leurs équivalents réalisés en lumière visible. Lors de la comparaison des données HI, avec des données à plus haute résolution, certaines différences étaient simplement attribuées à la faible résolution des observations HI. Le projet THINGS (The HI Nearby Galaxy Survey a observé plusieurs galaxies de l'échantillon SINGS (Spitzer Infrared Nearby Galaxies Survey). Les données cinématiques du projet THIGNS seront comparées aux données cinématiques obtenues en lumière Ha, afin de déterminer si la seule différence de résolution spatiale peut expliquer les différences observées. Les résultats montrent que des différences intrinsèques aux traceurs utilisées (hydrogène neutre ou ionisé), sont responsables de dissemblances importantes. La compréhension de ces particularités est importante: la distribution de la matière sombre, dérivée de la rotation des galaxies, est un test de certains modèles cosmologiques A new EMCCD (Electron multiplying Charge Coupled Device) controller is presented. It allows the EMCCD to be used for photon counting by drastically taking down its dominating source of noise : the clock induced charges. A new EMCCD camera was built using this controller. It has been characterized in laboratory and tested at the observatoire du mont Mégantic. When compared to the previous generation of photon counting cameras based on intensifier tubes, this new camera renders the observation of the galaxies kinematics with an integral field spectrometer with a Fabry-Perot interferometer in Ha light much faster, and allows fainter galaxies to be observed. The integration time required to reach a given signal-to-noise ratio is about 4 times less than with the intensifier tubes. Many applications could benefit of such a camera: fast, faint flux photometry, high spectral and temporal resolution spectroscopy, earth-based diffraction limited imagery (lucky imaging), etc. Technically, the camera is dominated by the shot noise for flux higher than 0. 002 photon/pixel/image. The 21 cm emission line of the neutral hydrogen (HI) is often used to map the galaxies kinematics. The extent of the distribution of the neutral hydrogen in galaxies, which goes well beyond the optical disk, is one of the reasons this line is used so often. However, the spatial resolution of such observations is limited when compared to their optical equivalents. When comparing the HI data to higher resolution ones, some differences were simply attributed to the beam smearing of the HI caused by its lower resolution. The THINGS (The HI Nearby Galaxy Survey) project observed many galaxies of the SINGS (Spitzer Infrared Nearby Galaxies Survey) project. The kinematics of THINGS will be compared to the kinematic data of the galaxies obtained in Ha light. The comparison will try to determine whether the sole beam smearing is responsible of the differences observed. The results shows that intrinsic dissimilarities between the kinematical tracers used are responsible of some of the observed disagreements. The understanding of theses differences is of a high importance as the dark matter distribution, inferred from the rotation of the galaxies, is a test to some cosmological models

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Fanelli, Cristiano <1991&gt. "Unveiling the unknown of cool stars with high-resolution spectroscopy." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10440/1/CristianoFanelli_tesi.pdf.

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Cool giant and supergiant stars are among the brightest populations in any stellar system and they are easily observable out to large distances, especially at infrared wavelengths. These stars also dominate the integrated light of star clusters in a wide range of ages, making them powerful tracers of stellar populations in more distant galaxies. High-resolution near-IR spectroscopy is a key tool for quantitatively investigating their kinematic, evolutionary and chemical properties. However, the systematic exploration and calibration of the NIR spectral diagnostics to study these cool stellar populations based on high-resolution spectroscopy is still in its pioneering stage. Any effort to make progress in the field is innovative and of impact on stellar archaeology and stellar evolution. This PhD project takes the challenge of exploring that new parameter space and characterizing the physical properties, the chemical content and the kinematics of cool giants and supergiants in selected disc fields and clusters of our Galaxy, with the ultimate goal of tracing their past and recent star formation and chemical enrichment history. By using optical HARPS-N and near-infrared GIANO-B high-resolution stellar spectra in the context of the large program SPA-Stellar Population Astrophysics: the detailed, age-resolved chemistry of the Milky Way disk” (PI L. Origlia), an extensive study of Arcturus, a standard calibrator for red giant stars, has been performed. New diagnostics of stellar parameters as well as optimal linelists for chemical analysis have been provided. Then, such diagnostics have been used to determine evolutionary properties, detailed chemical abundances of almost 30 different elements and mixing processes of a homogeneous sample of red supergiant stars in the Perseus complex.

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42

Lardo, Carmela <1984&gt. "Multiple stellar populations in globular clusters with photometry and low resolution spectroscopy." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5204/1/carmela_lardo_tesi.pdf.

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Our view of Globular Clusters has deeply changed in the last decade. Modern spectroscopic and photometric data have conclusively established that globulars are neither coeval nor monometallic, reopening the issue of the formation of such systems. Their formation is now schematized as a two-step process, during which the polluted matter from the more massive stars of a first generation gives birth, in the cluster innermost regions, to a second generation of stars with the characteristic signature of fully CNO-processed matter. To date, star-to-star variations in abundances of the light elements (C, N, O, Na) have been observed in stars of all evolutionary phases in all properly studied Galactic globular clusters. Multiple or broad evolutionary sequences have also been observed in nearly all the clusters that have been observed with good signal-to-noise in the appropriate photometric bands. The body of evidence suggests that spreads in light-element abundances can be fairly well traced by photometric indices including near ultraviolet passbands, as CNO abundance variations affect mainly wavelengths shorter than ~400 nm owing to the rise of some NH and CN molecular absorption bands. Here, we exploit this property of near ultraviolet photometry to trace internal chemical variations and combined it with low resolution spectroscopy aimed to derive carbon and nitrogen abundances in order to maximize the information on the multiple populations. This approach has been proven to be very effective in (i) detecting multiple population, (ii) characterizing their global properties (i.e., relative fraction of stars, location in the color-magnitude diagram, spatial distribution, and trends with cluster parameters) and (iii) precisely tagging their chemical properties (i.e., extension of the C-N anticorrelation, bimodalities in the N content).

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43

Lardo, Carmela <1984&gt. "Multiple stellar populations in globular clusters with photometry and low resolution spectroscopy." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5204/.

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Our view of Globular Clusters has deeply changed in the last decade. Modern spectroscopic and photometric data have conclusively established that globulars are neither coeval nor monometallic, reopening the issue of the formation of such systems. Their formation is now schematized as a two-step process, during which the polluted matter from the more massive stars of a first generation gives birth, in the cluster innermost regions, to a second generation of stars with the characteristic signature of fully CNO-processed matter. To date, star-to-star variations in abundances of the light elements (C, N, O, Na) have been observed in stars of all evolutionary phases in all properly studied Galactic globular clusters. Multiple or broad evolutionary sequences have also been observed in nearly all the clusters that have been observed with good signal-to-noise in the appropriate photometric bands. The body of evidence suggests that spreads in light-element abundances can be fairly well traced by photometric indices including near ultraviolet passbands, as CNO abundance variations affect mainly wavelengths shorter than ~400 nm owing to the rise of some NH and CN molecular absorption bands. Here, we exploit this property of near ultraviolet photometry to trace internal chemical variations and combined it with low resolution spectroscopy aimed to derive carbon and nitrogen abundances in order to maximize the information on the multiple populations. This approach has been proven to be very effective in (i) detecting multiple population, (ii) characterizing their global properties (i.e., relative fraction of stars, location in the color-magnitude diagram, spatial distribution, and trends with cluster parameters) and (iii) precisely tagging their chemical properties (i.e., extension of the C-N anticorrelation, bimodalities in the N content).

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44

Mingozzi, Matilde <1992&gt. "Exploring interstellar medium conditions in AGN and star forming galaxies with integral field spectroscopy." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amsdottorato.unibo.it/9461/1/thesis_final_mingozzi.pdf.

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The interstellar medium (ISM), made up of ionised, neutral and molecular gas, and interstellar dust, is a fundamental ingredient of galaxy evolution. It is the “primary repository” of galaxies, where star formation (SF) takes place, depositing energy, momentum and chemical enriched material via stellar evolution events (e.g. stellar winds, supernova explosions). ISM properties can be largely influenced also by Active Galactic Nuclei (AGN) activity, that through outflows and jets is capable of heating, compressing and/or removing the gas (feedback). SF and AGN activities are part of the so-called galaxy baryon cycle, that encloses a variety of physical processes, driving and shaping galaxy formation and evolution. This Thesis aims at probing and interpreting ISM properties in different galaxy types, including star forming galaxies and AGN hosts, and in different conditions within a galaxy, through the use of integral field spectroscopy (IFS) and the comparison of the observed data with ionisation models. The use of ISM tracers from optical to submillimeter wavelengths allowed to explore the different processes that affect ISM conditions across both AGN and star forming galaxies, and to assess their impact on the evolution of their hosts. The results obtained represent also a unique test bench for the new generation of photoionisation models, given the unprecedented detail of the analysed data as well as some limitations of current models highlighted in this work.

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45

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 isolated radio galaxies, through high-resolution spectroscopy. In particular one NLRG and three BLRG are studied, searching for warm gas, both in emission and absorption, in the soft X-ray band. I show that the soft spectrum of 3C33 originates from gas photoionized by the central engine. I found for the first time WA in 3C382 and 3C390.3. I show that the observed warm emitter/absorbers is not uniform and probably located in the NLR. The detected WA is slow implying a mass outflow rate and kinetic luminosity always well below 1% the L(acc) as well as the P(jet). Finally the radio--loud properties are compared with those of type 1 RQ AGNs. A positive correlation is found between the mass outflow rate/kinetic luminosity, and the radio loudness. This seems to suggest that the presence of a radio source (the jet?) affects the distribution of the absorbing gas. Alternatively, if the gas distribution is similar in Seyferts and radio galaxies, the M(out) vs rl relation could simply indicate a major ejection of matter in the form of wind in powerful radio AGNs.

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46

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 isolated radio galaxies, through high-resolution spectroscopy. In particular one NLRG and three BLRG are studied, searching for warm gas, both in emission and absorption, in the soft X-ray band. I show that the soft spectrum of 3C33 originates from gas photoionized by the central engine. I found for the first time WA in 3C382 and 3C390.3. I show that the observed warm emitter/absorbers is not uniform and probably located in the NLR. The detected WA is slow implying a mass outflow rate and kinetic luminosity always well below 1% the L(acc) as well as the P(jet). Finally the radio--loud properties are compared with those of type 1 RQ AGNs. A positive correlation is found between the mass outflow rate/kinetic luminosity, and the radio loudness. This seems to suggest that the presence of a radio source (the jet?) affects the distribution of the absorbing gas. Alternatively, if the gas distribution is similar in Seyferts and radio galaxies, the M(out) vs rl relation could simply indicate a major ejection of matter in the form of wind in powerful radio AGNs.

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47

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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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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49

Cocozza, Gabriele <1974&gt. "A spectroscopic and photometric study of MSP companions in Galactic Globular Clusters." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/631/1/Tesi_Cocozza_Gabriele.pdf.

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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

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50

Cocozza, Gabriele <1974&gt. "A spectroscopic and photometric study of MSP companions in Galactic Globular Clusters." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/631/.

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Abstract:

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

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Dissertations / Theses on the topic 'Astronomical spectroscopy'

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