Thèses sur le sujet « Radial velocitie »

La scoperta di pianeti che orbitano intorno ad altre stelle è uno degli eventi più importanti nell'astrofisica galattica degli ultimi due decenni. Dalla scoperta del primo esopianeta nel 1995, il numero di esopianeti scoperti è cresciuto sempre più in fretta e attualmente conosciamo più di 4,000 pianeti, molto diversi per dimensioni e distanza dalla stella ospite e anche in fattori come temperatura, massa, densità. La diversità degli esopianeti è un fattore chiave per comprendere la formazione dei sistemi planetari e in particolare la formazione del Sistema Solare e del nostro pianeta, la Terra. Questo è il motivo per cui la scienza osservativa degli esopianeti si sta concentrando su due diversi obiettivi: i) la caratterizzazione degli esopianeti, nel tentativo di determinare il raggio, la massa, la densità e la composizione degli oggetti osservati e ii) la caratterizzazione delle loro atmosfere, stabilendo gli elementi che l'atmosfera di un pianeta può supportare e i meccanismi che guidano i processi atmosferici. Caratterizzazione degli Esopianeti La fotometria, con il metodo dei transiti si è rivelato senza dubbio il metodo di scoperta di esopianeti con il maggior successo. La forza di questo metodo è il numero di parametri che possono essere ottenuti osservando il transito dei pianeti, soprattutto in combinazione con le osservazioni di velocità radiale (VR). In questo contesto, uno dei gruppi più prolifici è il Consorzio GTO di HARPS-N, che sfrutta l'alta risoluzione e l'estrema stabilità dello spettrografo HARPS-N, installato al Telescopio Nazionale Galileo, per caratterizzare e scoprire esopianeti combinando il metodo dei transiti e quello delle velocità radiali. Come collaboratore di questo gruppo, ho studiato un pianeta candidato scoperto dalla Campagna 16 della missione K2, HD 80653 b, una super-Terra che transita davanti alla sua stella con un periodo orbitale molto breve, e ho usato le VR HARPS-N per caratterizzarlo, ottenendo la sua massa e definendone la densità. Il pianeta appartiene ad una particolare classe di esopianeti: i pianeti a periodo ultra-corto, oggetti che orbitano intorno alle loro stelle con periodi estremamente brevi, più piccoli di due raggi terrestri e con composizioni simili a quella terrestre. Caratterizzazione di Atmosfere I gioviani ultra-caldi sono laboratori eccellenti per lo studio delle atmosfere esoplanetarie. Il sodio, per la sua grande sezione d'urto e per il fatto che le sue righe spettrali principali si trovano nel range spettrale della maggior parte degli spettrografi, è l'elemento più studiato, ma lo studio di nuove righe spettrali è cominciato. Righe del ferro, del titanio, del magnesio, ma anche tracce di cromo, scandio e ittrio sono state trovate negli spettri di trasmissione ad alta risoluzione dei pianeti più caldi. I due gioviani ultra-caldi KELT-9 b e KELT-20 b sono stati osservati dal programma atmosfere del gruppo italiano Global architecture of Planetary Systems (GAPS). Come membro del gruppo ho potuto esplorare più in dettaglio il metodo della spettroscopia in transito, creando due diverse routine per la caratterizzazione delle atmosfere. Il primo metodo segue approcci già utilizzati in precedenza, ma è in grado di rilevare righe spettrali deboli come quelle del magnesio, sommandole nello spazio delle velocità. Usando questo approccio ho analizzato gli spettri ad alta risoluzione di KELT-9 b e KELT-20 b e ho ottenuto i loro spettri di trasmissione, rilevando un assorbimento significativo per Na, H, Fe e Mg I. Il secondo metodo estrae gli spettri di trasmissione ad alta risoluzione e li cross-correla con modelli teorici di spettri di trasmissione. Analizzando gli spettri di KELT-20 b e utilizzando la cross-correlazione ho potuto confermare la presenza di Fe I, Fe II e Na I, trovate da analisi precedenti di altri gruppi di ricerca.
The discovery of planets orbiting around stars other than the Sun is by far the most relevant event in the galactic astrophysics of the last two decades. Since the discovery of the first exoplanet in 1995, the number of exoplanets discovered grew fast and we currently know more than 4,000 exoplanets, very diverse in dimension and distance from parent stars and also in factors as temperature, mass, density. The diversity of exoplanets is a key factor to understand more about the formation of planetary systems and in particular the formation of the Solar System and our planet, the Earth. This is the reason why observational exoplanetary science is currently focusing on two different fields: i) the characterization of exoplanets, trying to determine the radius, the mass, the density and the bulk composition of the objects observed, and ii) the characterization of their atmospheres, establishing the elements that the atmosphere of a planet supports and the mechanisms that drive the atmospheric processes. Characterization of Exoplanets Photometry with the transit method has arguably been the most successful exoplanet discovery method to date. The method’s strength is the rich set of parameters that can be obtained from transiting planets, in particular in combination with RV observations. In this framework, one of the most prolific groups is the HARPS-N Guaranteed Time Observations (GTO) Consortium, that makes use of the high resolution (R = 115,000) and extreme stability of the HARPS-N spectrograph, installed on the Telescopio Nazionale Galileo (TNG), to characterize and discover exoplanets by combining transits and RV methods. As a collaborator of this group, I studied a candidate planet discovered by K2 Campaign 16, HD 80653 b, a super-Earth planet transiting the star on a short period orbit, and used HARPS-N RV data to characterize it, finding its mass and defining its bulk density. It belongs to a peculiar class of exoplanets: the Ultra-Short Period (USP) planets, objects that orbit their stars with extremely short periods, smaller than about 2 Earth Radii and compositions similar to that of the Earth. Characterization of Atmospheres Ultra-hot Jupiters are excellent laboratories for the study of exoplanetary atmospheres. Sodium, due to its large cross-section and to the fact it is in the wavelength range of most optical spectrographs, is the most studied element, but new interesting features begin to be analyzed. Lines of iron, titanium, magnesium, but also chromium, scandium and yttrium have been found in the high resolution transmission spectra of the hottest planets. The two ultra-hot Jupiters KELT-9 b and KELT-20 b were observed in the framework of the Global architecture of Planetary Systems (GAPS) Atmosphere program. I explored more in detail the transit spectroscopy method, creating two different routines for atmosphere characterization. The first routine follows previous approaches for high-resolution spectroscopy, but is able to detect weak spectral lines such as those of magnesium, by co-adding the lines in the velocities space. Using this procedure, I analyzed the high-resolution spectra of KELT-9 b and KELT-20 b, obtaining their transmission spectra and detecting significant absorption for Na, H, Fe and Mg I. The second routine extracts the high-resolution transmission spectra of exoplanets and cross-correlates them with theoretical transmission spectra models. I analyzed the high-resolution spectra of KELT-20 b and with the cross-correlation technique I confirmed previous detections of Fe I, Fe II, and Na I.

Context. For over 12 yr, we have carried out a precise radial velocity (RV) survey of a sample of 373 G- and K-giant stars using the Hamilton Echelle Spectrograph at the Lick Observatory. There are, among others, a number of multiple planetary systems in our sample as well as several planetary candidates in stellar binaries. Aims. We aim at detecting and characterizing substellar and stellar companions to the giant star HD 59686 A (HR 2877, HIP 36616). Methods. We obtained high-precision RV measurements of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in the RVs, we can assess the nature of companions in the system. To distinguish between RV variations that are due to non-radial pulsation or stellar spots, we used infrared RVs taken with the CRIRES spectrograph at the Very Large Telescope. Additionally, to characterize the system in more detail, we obtained high-resolution images with LMIRCam at the Large Binocular Telescope. Results. We report the probable discovery of a giant planet with a mass of m(p) sin i = 6.92(-0.24)(+0.18) M-Jup orbiting at a(p) = 1.0860(-0.0007)(+0.0006) aufrom the giant star HD 59686 A. In addition to the planetary signal, we discovered an eccentric (e(B) = 0.729(-0.003)(+0.004)) binary companionwith a mass of m(B) sin i = 0.5296(-0.0008)(+0.0011) M-circle dot orbiting at a close separation from the giant primary with a semi-major axis of a(B) = 13.56(-0.14)(+0.18) au. Conclusions. The existence of the planet HD 59686 Ab in a tight eccentric binary system severely challenges standard giant planet formation theories and requires substantial improvements to such theories in tight binaries. Otherwise, alternative planet formation scenarios such as second-generation planets or dynamical interactions in an early phase of the system's lifetime need to be seriously considered to better understand the origin of this enigmatic planet.

Radial velocities measured from near-infrared (NIR) spectra are a potential tool to search for extrasolar planets around cool stars. High resolution infrared spectrographs now available reach the high precision of visible instruments, with a constant improvement over time. GIANO is an infrared echelle spectrograph and it is a powerful tool to provide high resolution spectra for accurate radial velocity measurements of exo-planets and for chemical and dynamical studies of stellar or extragalactic objects. No other IR instruments have the GIANO's capability to cover the entire NIR wavelength range. In this work we develop an ensemble of IDL procedures to measure high precision radial velocities on a few GIANO spectra acquired during the commissioning run, using the telluric lines as wevelength reference. In Section 1.1 various exoplanet search methods are described. They exploit different properties of the planetary system. In Section 1.2 we describe the exoplanet population discovered trough the different methods. In Section 1.3 we explain motivations for NIR radial velocities and the challenges related the main issue that has limited the pursuit of high-precision NIR radial velocity, that is, the lack of a suitable calibration method. We briefly describe calibration methods in the visible and the solutions for IR calibration, for instance, the use of telluric lines. The latter has advantages and problems, described in detail. In this work we use telluric lines as wavelength reference. In Section 1.4 the Cross Correlation Function (CCF) method is described. This method is widely used to measure the radial velocities.In Section 1.5 we describe GIANO and its main science targets. In Chapter 2 observational data obtained with GIANO spectrograph are presented and the choice criteria are reported. In Chapter 3 we describe the detail of the analysis and examine in depth the flow chart reported in Section 3.1. In Chapter 4 we give the radial velocities measured with our IDL procedure for all available targets. We obtain an rms scatter in radial velocities of about 7 m/s. Finally, we conclude that GIANO can be used to measure radial velocities of late type stars with an accuracy close to or better than 10 m/s, using telluric lines as wevelength reference. In 2014 September GIANO is being operative at TNG for Science Verification and more observational data will allow to further refine this analysis.

Aims. The goal of this paper is to present complete radial-velocity data for the spectroscopically selected McCormick sample of nearby K-M dwarfs and, based on these and supplementary data, to determine the space-velocity distributions of late-type stars in the solar neighborhood. Methods. We analyzed nearly 3300 measurements of radial velocities for 1049 K-M dwarfs, that we obtained during the past decade with a CORAVEL-type instrument, with a primary emphasis on detecting and eliminating from kinematic calculations the spectroscopic binaries and binary candidates. Combining radial-velocity data with HIPPARCOS/Tycho-2 astrometry we calculated the space-velocity components and parameters of the galactic orbits in a three-component model potential for the stars in the sample, that we use for kinematical analysis and for the identification of possible candidate members of nearby stellar kinematic groups. Results. We present the catalog of our observations of radial velocities for 959 stars which are not suspected of velocity variability, along with the catalog of U, V, W velocities and Galactic orbital parameters for a total of 1088 K-M stars which are used in the present kinematic analysis. Of these, 146 stars were identified as possible candidate members of the known nearby kinematic groups and suspected subgroups. The distributions of space-velocity components, orbital eccentricities, and maximum distances from the Galactic plane are consistent with the presence of young, intermediate-age and old populations of the thin disk and a small fraction (similar to 3%) of stars with the thick disk kinematics. The kinematic structure gives evidence that the bulk of K-M type stars in the immediate solar vicinity represents a dynamically relaxed stellar population. The star MCC 869 is found to be on a retrograde Galactic orbit (V = -262 km s(-1)) of low inclination (4 degrees) and can be a member of stellar stream of some dissolved structure. The Sun's velocity with respect to the Local Standard of Rest, derived from the distributions of space-velocity components, is (U-circle dot, V-circle dot, W-circle dot) = (9.0 +/- 1.4, 13.1 +/- 0.6, 7.2 +/- 0.8) km s(-1). The radial solar motion derived via the Stromberg's relation, V-circle dot = 14.2 +/- 0.8 km s(-1), agrees within the errors with the value obtained directly from the V distribution of stars on nearly circular orbits.

The GMT-Consortium Large Earth Finder (G-CLEF) is an echelle spectrograph with precision radial velocity (PRV) capability that will be a first light instrument for the Giant Magellan Telescope (GMT). G-CLEF has a PRV precision goal of 40 cm/sec (10 cm/s for multiple measurements) to enable detection of Earth-like exoplanets in the habitable zones of sun-like stars'. This precision is a primary driver of G-CLEF's structural design. Extreme stability is necessary to minimize image motions at the CCD detectors. Minute changes in temperature, pressure, and acceleration environments cause structural deformations, inducing image motions which degrade PRV precision. The instrument's structural design will ensure that the PRV goal is achieved under the environments G-CLEF will be subjected to as installed on the GMT azimuth platform, including: Millikelvin (0.001 K) thermal soaks and gradients 10 millibar changes in ambient pressure Changes in acceleration due to instrument tip/tilt and telescope slewing Carbon fiber/cyanate composite was selected for the optical bench structure in order to meet performance goals. Low coefficient of thermal expansion (C 1E) and high stiffness-to-weight are key features of the composite optical bench design. Manufacturability and serviceability of the instrument are also drivers of the design. In this paper, we discuss analyses leading to technical choices made to minimize G-CLEF's sensitivity to changing environments. Finite element analysis (FEA) and image motion sensitivity studies were conducted to determine PRV performance under operational environments. We discuss the design of the optical bench structure to optimize stiffness to -weight and minimize deformations due to inertial and pressure effects. We also discuss quasi-kinematic mounting of optical elements and assemblies, and optimization of these to ensure minimal image motion under thermal, pressure, and inertial loads expected during PRV observations.

Spectroscopic orbital elements and/or related parameters have been determined for eight binary systems, using radial-velocity measurements that have a typical precision of about 15 ms⁻¹. The orbital periods of these systems range from about 10 days to 26 years, with a median of about 6 years. Orbital solutions were determined for the seven systems with shorter periods. The measurement of the mass ratio of the longest-period system, HD217166, demonstrates that this important astrophysical quantity can be estimated in a model-free manner with less than 10% of the orbital cycle observed spectroscopically.\\ Single-lined orbital solutions have been derived for five of the binaries. Two of these systems are astrometric binaries: β Ret and ν Oct. The other SB1 systems were 94 Aqr A, θ Ant, and the 10-day system, HD159656. The preliminary spectroscopic solution for θ Ant (P~18 years), is the first one derived for this system. The improvement to the precision achieved for the elements of the other four systems was typically between 1--2 orders of magnitude. The very high precision with which the spectroscopic solution for HD159656 has been measured should allow an investigation into possible apsidal motion in the near future. In addition to the variable radial velocity owing to its orbital motion, the K-giant, ν Oct, has been found to have an additional long-term irregular periodicity, attributed, for the time being, to the rotation of a large surface feature.\\ Double-lined solutions were obtained for HD206804 (K7V+K7V), which previously had two competing astrometric solutions but no spectroscopic solution, and a newly discovered seventh-magnitude system, HD181958 (F6V+F7V). This latter system has the distinction of having components and orbital characteristics whose study should be possible with present ground-based interferometers. All eight of the binary systems have had their mass ratio and the masses of their components estimated.\\ The following comments summarize the motivation for getting these results, and the manner in which the research was carried out. \\ The majority of stars exist in binary systems rather than singly as does the Sun. These systems provide astronomers with the most reliable and proven means to determine many of the fundamental properties of stars. One of these properties is the stellar mass, which is regarded as being the most important of all, since most other stellar characteristics are very sensitive to the mass. Therefore, empirical masses, combined with measurements of other stellar properties, such as radii and luminosities, are an excellent test for competing models of stellar structure and evolution.\\ Binary stars also provide opportunities to observe and investigate many extraordinary astrophysical processes that do not occur in isolated stars. These processes often arise as a result of direct and indirect interactions between the components, when they are sufficiently close to each other. Some of the interactions are relatively passive, such as the circularization of the mutual orbits, whilst others result from much more active processes, such as mass exchange leading to intense radiation emissions. \\ A complete understanding of a binary system's orbital characteristics, as well as the measurement of the all-important stellar masses, is almost always only achieved after the binary system has been studied using two or more complementary observing techniques. Two of the suitable techniques are astrometry and spectroscopy. In favourable circumstances, astrometry can deduce the angular dimensions of the orbit, the total mass of the system, and sometimes, its distance from us. Spectroscopy, on the other hand, can determine the linear scale of the orbit and the ratio of the stellar masses, based on the changing radial velocities of both stars. When a resolved astrometric orbital solution is also available, the velocities of both stars can allow the binary system's parallax to be determined, and the velocities of one star can provide a measure of the system mass ratio.\\ Unfortunately, relatively few binary systems are suited to these complementary studies. Underlying this difficulty are the facts that, typically, astrometrically-determined orbits favour those with periods of years or decades, whereas spectroscopic orbital solutions are more often measured for systems with periods of days to months. With the development of high-resolution astrometric and spectroscopic techniques in recent years, it is hoped that many more binary systems will be amenable to these complementary strategies.\\ Several months after this thesis began, a high-resolution spectrograph, HERCULES, commenced operations at the Mt John University Observatory, to be used in conjuction with the 1-metre McLellan telescope. For late-type stars, the anticipated velocity precision was ≲10 ms⁻¹. The primary goals of this thesis were: 1.~to assess the performance of HERCULES and the related reduction software that subsequently followed, 2.~to carry out an observational programme of 20 or so binary systems, and 3.~to determine the orbital and stellar parameters which characterize some of these systems. The particular focus was on those binaries that have resolved or unresolved astrometric orbital solutions, which therefore may be suited to complementary investigations.\\ HERCULES was used to acquire spectra of the programme stars, usually every few weeks, over a timespan of about three years. High-resolution spectra were acquired for the purpose of measuring precise radial velocities of the stars. When possible, orbital solutions were derived from these velocities, using the method of differential corrections.

Spectroscopic orbital elements and/or related parameters have been determined for eight binary systems, using radial-velocity measurements that have a typical precision of about 15 ms-1. The orbital periods of these systems range from about 10 days to 26 years, with a median of about 6 years. Orbital solutions were determined for the seven systems with shorter periods. The measurement of the mass ratio of the longest-period system, HD 217166, demonstrates that this important astrophysical quantity can be estimated in a model-free manner with less than 10% of the orbital cycle observed spectroscopically. Single-lined orbital solutions have been derived for five of the binaries. Two of these systems are astrometric binaries: ß Ret and v Oct. The other SB1 systems were 94 Aqr A, θ Ant, and the 10-day system, HD 159656. The preliminary spectroscopic solution for θ Ant (P ~ 18 years), is the first one derived for this system. The improvement to the precision achieved for the elements of the other four systems was typically between 1-2 orders of magnitude. The very high precision with which the spectroscopic solution for HD 159656 has been measured should allow an investigation into possible apsidal motion in the near future. In addition to the variable radial velocity owing to its orbital motion, the K-giant, v Oct, has been found to have an additional long-term irregular periodicity, attributed, for the time being, to the rotation of a large surface feature. Double-lined solutions were obtained for HD206804 (K7V+K7V), which previously had two competing astrometric solutions but no spectroscopic solution, and a newly discovered seventh-magnitude system, HD 181958 (F6V+F7V). This latter system has the distinction of having components and orbital characteristics whose study should be possible with present ground-based interferometers. All eight of the binary systems have had their mass ratio and the masses of their components estimated. The following comments summarize the motivation for getting these results, and the manner in which the research was carried out. The majority of stars exist in binary systems rather than singly as does the Sun. These systems provide astronomers with the most reliable and proven means to determine many of the fundamental properties of stars. One of these properties is the stellar mass, which is regarded as being the most important of all, since most other stellar characteristics are very sensitive to the mass. Therefore, empirical masses, combined with measurements of other stellar properties, such as radii and luminosities, are an excellent test for competing models of stellar structure and evolution. Binary stars also provide opportunities to observe and investigate many extraordinary astrophysical processes that do not occur in isolated stars. These processes often arise as a result of direct and indirect interactions between the components, when they are sufficiently close to each other. Some of the interactions are relatively passive, such as the circularization of the mutual orbits, whilst others result from much more active processes, such as mass exchange leading to intense radiation emissions. A complete understanding of a binary system's orbital characteristics, as well as the measurement of the all-important stellar masses, is almost always only achieved after the binary system has been studied using two or more complementary observing techniques. Two of the suitable techniques are astrometry and spectroscopy. In favourable circumstances, astrometry can deduce the angular dimensions of the orbit, the total mass of the system, and sometimes, its distance from us. Spectroscopy, on the other hand, can determine the linear scale of the orbit and the ratio of the stellar masses, based on the changing radial velocities of both stars. When a resolved astrometric orbital solution is also available, the velocities of both stars can allow the binary system's parallax to be determined, and the velocities of one star can provide a measure of the system mass ratio. Unfortunately, relatively few binary systems are suited to these complementary studies. Underlying this difficulty are the facts that, typically, astrometrically-determined orbits favour those with periods of years or decades, whereas spectroscopic orbital solutions are more often measured for systems with periods of days to months. With the development of high-resolution astrometric and spectroscopic techniques in recent years, it is hoped that many more binary systems will be amenable to these complementary strategies. Several months after this thesis began, a high-resolution spectrograph, HERCULES, commenced operations at the Mt John University Observatory, to be used in conjuction with the 1-metre McLellan telescope. For late-type stars, the anticipated velocity precision was ≤ 10 m s-1. The primary goals of this thesis were: 1. to assess the performance of HERCULES and the related reduction software that subsequently followed, 2. to carry out an observational programme of 20 or so binary systems, and 3. to determine the orbital and stellar parameters which characterize some of these systems. The particular focus was on those binaries that have resolved or unresolved astrometric orbital solutions, which therefore may be suited to complementary investigations. HERCULES was used to acquire spectra of the programme stars, usually every few weeks, over a time span of about three years. High-resolution spectra were acquired for the purpose of measuring precise radial velocities of the stars. When possible, orbital solutions were derived from these velocities, using the method of differential corrections.

Since the discovery of the first planetary mass companion around a pulsar star (Wolszczan and Frail 1992) and shortly after around a star similar to our Sun (51 Peg Mayor and Queloz 1995), many steps have been done in exoplanet science. This led to a rapidly growing sample of detected planets: the minimum mass of the companions is decreasing fast, and is now close to the Earth mass. New and more precise instruments have been built and many others are planned. The final goal is the discovery of Earth twins and, ultimately, traces of extrasolar life. As learnt with the discovery of 51 Peg, about fifteen years ago, observations often open new questions about how the discovered planets can form and survive, ending in the needs of more sophisticated theories to address these items. Many statistical studies have been done using information coming from more than a decade of extensive searches for exoplanets, trying to answer questions either related to the distribution of the properties of those objects, such as the mass, orbital period and eccentricity (Lineweaver and Grether 2003; Cumming et al. 2008) as well as about the relevance of the host star characteristics (mass, metallicity) on the final frequency and distribution of planetary systems (see Fischer and Valenti 2005; Santos et al. 2004b; Johnson et al. 2007; Bonavita and Desidera 2007; Valenti and Fischer 2008; Kennedy and Kenyon 2008; Bonavita et al. 2010). Since the most successful techniques (radial velocity and transit) have focused on the inner (< 5 UA) environment of main sequence solar-type stars, most of the available informations on the frequency of planets concern this kind of targets. In this context it is useful and crucial to learn as much as possible from the available data. In addition it is also very important to determine the frequency of planets in binaries. This is an important issue in the field of extrasolar planets studies, because of its relevance for an estimate of the global planet population of our Galaxy (more than half of solar type stars are in binary or multiple systems as reported in Duquennoy and Mayor 1991) and the clues it can give to our understanding of planet formation and evolution. The study of the properties of planets in binaries, and any difference to those of the planets orbiting single stars, would shed light on the effects caused by the presence of the companions. The SARG survey (Desidera et al. 2010) searches for planets in binary stars, an environment usually excluded from the RV surveys. Another peculiarity of the survey stars is their activity level, because the sample has many stars relatively active, which makes the distinction of any signal due to a planet very tricky. In this thesis we present the results on the discovered planet, the method we used to detect it, the error analysis, the stellar activity analysis and finally the study on the frequency of planet in the binary system. In the Chapter 1 I will try to put our work in context, by summarizing the status of the art of the extrasolar planet research and knowledge, both on the theoretical and observational side, in particular in binary star systems. First I will present an overview of the techniques for detecting extrasolar planets and of the planet formation theories. Then I will summarize the properties of the exoplanets as they come from the observational results, finally focusing on the properties and formation of the planet in binary system. Chapter 2 reviews the SARG survey, the instrument used for observations, the aims of this project and the sample observed. Chapter 3 includes the description of the data reduction technique and a detailed overview on the data analysis code. In the Chapter 4 I will present a detailed description of the analysis of the survey. We started with a thorough error analysis to distinguish the “noise” contributions from the planet signal. We performed also a detailed jitter study for the whole stars sample for monitoring the most important contribution to the errors. After this analysis, I will go into detail with the presentation of the trend study on the survey and the search for planet candidates using an IDL code that I personally wrote. This code includes the study of the periodogram for each RV data set, and the Keplerian orbit modeling due to the presence of the possible companion of the observed star. Statistical tests on significativity of the periodicity and the computation of the orbital parameter error bars were performed for a more complete analysis. In the Chapter 5 the discovered planet is presented. I personally dealt with the computation of the orbital parameters of the planet, and also contributed to the jitter analysis of the stars and to obtain the contrast limit on companion masses of the A component. Chapter 6 analyzes how we investigated on a peculiar stellar activity case in the survey. I personally dealt with the computation of the activity index to prove the relation between the RV variations and the stellar activity cycle. In the Chapter 7 I will include the results on a planet which was discovered by other authors, but, that we could find with more observations. I will present the periodogram and Keplerian orbit analysis compared to the results of the other researchers group. Chapter 8 gives a brief overview of the current knowledge on the frequency of planets, and a detailed description on the results came from the Monte Carlo simulation for the SARG survey. In the Chapter 9 I finally summarizes the conclusions and future perspectives of the work.
Dalla scoperta del primo compagno di massa planetaria attorno a una stella pulsar (Wolszczan and Frail 1992) e da quella, di poco successiva, attorno ad una stella simile al nostro Sole (51 Peg Mayor and Queloz 1995), si sono compiuti numerosi progressi nella scienza che si occupa degli esopianeti. Sono stati costruiti strumenti nuovi e sempre più precisi e molti altri sono in fase di studio e realizzazione. Ciò ha portato ad un campione rapidamente crescente di pianeti rivelati, inoltre la massa minima dei pianeti extrasolari si è ridotta velocemente ed ora è vicina a quella della Terra. Lo scopo finale è quello della scoperta di pianeti il più possibilmente simili alla Terra ed, infine, di tracce di vita extrasolare. Con la scoperta di 51 Peg, circa quindici anni fa, si è imparato come le osservazioni sollevino spesso nuovi dubbi riguardo le teorie di formazione ed evoluzione, concludendosi con la necessità di sviluppare teorie più sofisticate per affrontare tali questioni. Grazie alle informazioni provenienti da più di un decennio di ricerca di pianeti extrasolari, sono stati eseguiti numerosi studi statistici per cercare di rispondere a domande correlate alla distribuzione delle proprietà di questi oggetti, come massa, periodo orbitale ed eccentricità (Lineweaver and Grether 2003; Cumming et al. 2008), come pure a quelle riguardanti le caratteristiche delle stelle ospitanti (massa, metallicità) sulla frequenza e distribuzione finale dei sistemi planetari (consultare Fischer and Valenti 2005; Santos et al. 2004b; Johnson et al. 2007; Bonavita and Desidera 2007; Valenti and Fischer 2008; Kennedy and Kenyon 2008; Bonavita et al. 2010). Poichè le tecniche di maggior successo (velocità radiali e transiti) si sono focalizzate sull’ambiente interno (< 5UA) per stelle di tipo solare di sequenza principale, gran parte delle informazioni disponibili sulla frequenza di pianeti riguardano questo tipo di target. In questo contesto è, quindi, fondamentale analizzare quanto possibile i dati osservativi. Inoltre, studiare la frequenza di pianeti in stelle binarie è di grande interesse, in quanto più della metà delle stelle di tipo solare si trova in sistemi binari o multipli (Duquennoy and Mayor 1991), e quindi una tale informazione può fornire indicazioni sulla formazione ed evoluzione dei pianeti. Lo studio delle proprietà dei pianeti in stelle binarie, confrontato con le peculiarità dei pianeti ospiti di stelle singole, può chiarire quali possano essere gli effetti causati dalla presenza dei compagni planetari. La survey SARG (Desidera et al. 2010) è dedicata a ricercare pianeti in stelle binarie, un ambiente di solito non preso in considerazione dalla maggior parte delle survey che si basano sulla misurazione delle velocità radiali delle stelle. Questo è dovuto principalmente alla difficoltà di isolare le componenti vicine nella fenditura e, quindi, ad evitare di andare incontro a problemi di contaminazione. Un’altra peculiarità delle stelle del nostro campione è il loro livello di attività. Molti oggetti sono relativamente attivi, il che rende la distinzione del segnale planetario molto delicata, ma allo stesso tempo molto interessante da analizzare. In questa tesi si presentano i risultati dell’unico pianeta scoperto, il metodo che è stato utilizzato per rilevarlo, l’analisi degli errori effettuata per l’intero campione, includendo anche la trattazione sull’attività stellare, e si conclude con uno studio sulla frequenza dei pianeti in sistemi binari che risulta dall’analisi della survey. Nel Capitolo 1 si contestualizzerà il lavoro, riassumendo lo stato dell’arte della ricerca dei pianeti extrasolari e la conoscenza in particolare, sia dal punto di vista teorico, sia osservativo, dei pianeti scoperti in sistemi stellari binari. Per prima cosa si presenterà una panoramica delle tecniche per la rilevazione di pianeti extrasolari e delle teorie della formazione dei pianeti. In seguito verranno riassunte le proprietà dei pianeti extrasolari che provengono dai risultati osservativi e, per concludere, ci si focalizzerà sulle proprietà della formazione dei pianeti in sistemi binari. Nel Capitolo 2 si presenterà la survey SARG, a partire dalla descrizione dello strumento utilizzato per le osservazioni e si proseguirà con l’esposizione degli obiettivi di questo progetto, la presentazione del campione di stelle osservato e lo stato del programma. Il Capitolo 3 descriverà la tecnica di riduzione dei dati ed include una panoramica dettagliata sul codice di analisi dei dati. Nel Capitolo 4 presenterò una descrizione dettagliata delle analisi delle stelle del campione. Illustrerò come per prima cosa sia stata effettuata un’analisi approfondita degli errori per distinguere il contributo “ rumoroso” dall’eventuale segnale planetario e, successivamente, sia stato eseguito uno studio dettagliato sul jitter per l’intero campione di stelle, in quanto il suo contributo è molto importante nell’analisi delle piccole variazioni delle velocità radiali. Dopo questa analisi entrerò in dettaglio presentando lo studio sui trend del campione e la ricerca dei pianeti candidati utilizzando un codice che ho personalmente implementato. Questo programma comprende lo studio del periodogramma per ogni set di dati e la modellizzazione dell’orbita Kepleriana dovuta all’eventuale presenza di un compagno planetario o stellare della stella osservata. Presenterò, infine, i test statistici eseguiti sulla significatività della periodicità ed il calcolo delle barre d’errore nei parametri orbitali, al fine di ottenere un’analisi solida e completa. Nel Capitolo 5 verrà presentato il pianeta rivelato. Ho contribuito personalmente al calcolo dei parametri orbitali del pianeta, utilizzando il codice descritto nel capitolo precedente e mi sono, inoltre, occupata dell’analisi del jitter delle stelle e di ricavare il limite di massa della compagna della componente primaria, dal contrasto in banda K. Nel Capitolo 6 si analizzerà un caso peculiare di attività stellare all’interno del nostro campione. Ho personalmente calcolato un indice di attività misurato su una riga degli spettri, per verificare la relazione tra le variazioni delle velocità radiali e il ciclo di attività stellare. Nel Capitolo 7 saranno presentati i risultati su un pianeta ospite di una stella del nostro campione, ma rivelato da altri autori. Riporterò l’analisi del periodogramma e l’analisi dell’orbita Kepleriana, al fine di confrontare i nostri risultati con quelli ottenuti dagli scopritori. Il Capitolo 8 fornirà una breve panoramica delle attuali conoscenze sulla frequenza dei pianeti, e una descrizione dettagliata dei risultati ottenuti dall’analisi statistica della survey SARG. Nel Capitolo 9 riassumerò, infine, le conclusioni e le prospettive future.

Late-type evolved stars include the variable red giants, like Mira and semi-regular variables, and the pulsating supergiant RV Tauri stars. Despite this, K-type giants in the past were generally believed to be constant in photometry and radial velocity, but in the last decade it has been discovered that this is not necessarily the case. This was the motivation for spectroscopic observations of 44 late-type evolved stars to be carried out over three years, in the hope of helping to determine how common K giants variable in radial velocity are and whether the variations are related to those seen for other late-type evolved stars. The observations were obtained at Mount John University Observatory and used with digital cross-correlation to achieve relative radial velocities of 50 m/s precision. At this precision all but eight of the observed stars were found to be variable in radial velocity. Thirteen stars also had broad-band photometry taken, because any one of orbital motion, rotation with starspots, pulsation and the motion of large convective cells could cause apparent radial-velocity variations. Knowledge of the relationship between light and radial-velocity variations can help distinguish between these different mechanisms. The timescales for these different mechanisms were also estimated to help determine which was responsible for the variations observed. Generally the observed K-giant radial-velocity timescales were of the order of a few hundred days, which indicates they are due to one of binary motion, rotational modulation or non-acoustic non-radial pulsation. However, for M giants and supergiants the situation was very different with both short-term and long-term radial-velocity timescales being found in most stars. In most cases the short-term timescale is due to acoustic pulsation, while the long-term timescale could be due to any one of binary motion, surface features (including the motion of large convective cells) or non-acoustic non-radial pulsation.

Insufficient instrument thermomechanical stability is one of the many roadblocks for achieving 10 cm s(-1) Doppler radial velocity precision, the precision needed to detect Earth-twins orbiting solar-type stars. Highly temperature and pressure stabilized spectrographs allow us to better calibrate out instrumental drifts, thereby helping in distinguishing instrumental noise from astrophysical stellar signals. We present the design and performance of the Environmental Control System (ECS) for the Habitable-zone Planet Finder (HPF), a high-resolution (R = 50,000) fiber-fed near-infrared (NIR) spectrograph for the 10 m Hobby-Eberly Telescope at McDonald Observatory. HPF will operate at 180 K, driven by the choice of an H2RG NIR detector array with a 1.7 mu m cutoff. This ECS has demonstrated 0.6 mK rms stability over 15 days at both 180 and 300 K, and maintained high-quality vacuum (< 10 (7) Torr) over months, during long-term stability tests conducted without a planned passive thermal enclosure surrounding the vacuum chamber. This control scheme is versatile and can be applied as a blueprint to stabilize future NIR and optical high-precision Doppler instruments over a wide temperature range from similar to 77 K to elevated room temperatures. A similar ECS is being implemented to stabilize NEID, the NASA/NSF NN-EXPLORE spectrograph for the 3.5 m WIYN telescope at Kitt Peak, operating at 300 K. A [full SolidWorks 3D-CAD model] and a comprehensive parts list of the HPF ECS are included with this manuscript to facilitate the adaptation of this versatile environmental control scheme in the broader astronomical community.

This Ph.D. Thesis has as general subject the study of extrasolar planets using the radial velocity technique from both, instrumental and observative, points of view. Two main parts compose the work: the upgrade of the spectrograph FOCES, a high resolution spectrograph that will be installed next year at the Wendelstein Observatory, and the search of giant planets around stars in the open cluster Messier-67 (M67).
Die vorliegende Dissertation behandelt die Suche von extra-solaren Planeten mit der Radialgeschwindigkeits Methode und zwar sowohl in Bezug auf die dafür notwendige Instrumentierung als auch auf die Beobachtung. Die Arbeit ist in zwei Teile gegliedert. Im ersten Teil werden die vorgenommenen Verbesserungen des hochauflösenden Spektrographen FOCES beschrieben, der im kommenden Jahr am Wendelstein Observatorium installiert werden wird. Der zweite Teil handelt von der Suche nach Gasplaneten im offenen Sternhaufen M67.

The detection of low-mass extra-solar planets through radial-velocity searches is currently limited by the intrinsic magnetic activity of the host stars. The correlated noise that arises from their natural radial-velocity variability can easily mimic or conceal the orbital signals of super-Earth and Earth-mass extra-solar planets. I developed an intuitive and robust data analysis framework in which the activity-induced variations are modelled with a Gaussian process that has the frequency structure of the photometric variations of the star, thus allowing me to determine precise and reliable planetary masses. I applied this technique to three recently discovered planetary systems: CoRoT-7, Kepler-78 and Kepler-10. I determined the masses of the transiting super-Earth CoRoT-7b and the small Neptune CoRoT-7c to be 4.73 ± 0.95 M⊕ and 13.56 ± 1.08 M⊕, respectively. The density of CoRoT-7b is 6.61 ± 1.72 g.cm⁻³, which is compatible with a rocky composition. I carried out Bayesian model selection to assess the nature of a previously identified signal at 9 days, and found that it is best interpreted as stellar activity. Despite the high levels of activity of its host star, I determined the mass of the Earth-sized planet Kepler-78b to be 1.76 ± 0.18 M⊕. With a density of 6.2(+1.8:-1.4) g.cm⁻³, it is also a rocky planet. I found the masses of Kepler-10b and Kepler-10c to be 3.31 ± 0.32 M⊕ and 16.25 ± 3.66 M⊕, respectively. Their densities, of 6.4(+1.1:-0.7) g.cm⁻³ and 8.1 ± 1.8 g.cm⁻³, imply that they are both of rocky composition – even the 2 Earth-radius planet Kepler-10c! In parallel, I deepened our understanding of the physical origin of stellar radial-velocity variability through the study of the Sun, which is the only star whose surface can be imaged at high resolution. I found that the full-disc magnetic flux is an excellent proxy for activity-induced radial-velocity variations; this result may become key to breaking the activity barrier in coming years. I also found that in the case of CoRoT-7, the suppression of convective blueshift leads to radial-velocity variations with an rms of 1.82 m.s⁻¹, while the modulation induced by the presence of dark spots on the rotating stellar disc has an rms of 0.46 m.s⁻¹. For the Sun, I found these contributions to be 2.22 m.s⁻¹ and 0.14 m.s⁻¹, respectively. These results suggest that for slowly rotating stars, the suppression of convective blueshift is the dominant contributor to the activity-modulated radial-velocity signal, rather than the rotational Doppler shift of the flux blocked by starspots.

High accuracy measurements of variations in the radial velocity of the K 1 giant star Arcturus have been obtained. The observations span 5 years and have a point-to-point repeatability of 5 m s⁻¹ and night-to-night stability of better than 20 m s⁻¹. Velocity oscillations of Arcturus were discovered during the course of this work in 1986. Extensive additional data, presented here, indicate that Arcturus is exhibiting global nonradial acoustic oscillations with characteristics similar to those occurring in the Sun. A Fabry-Perot interferometer, used in transmission, is employed to accurately tag the stellar wavelengths. The light is dispersed by a cross-dispersed echelle. About 750 points in the spectrum are monitored over 4250-4750 Å. All observations were done using the 0.9 m telescope of the University of Arizona on Kitt Peak, which is dedicated half-time for use with this instrument. A dedicated facility was crucial to this work - because of the changing nature of the oscillations, many observing runs, over several years, were required to understand the star's behavior. Continuous data sets as long as 30 days were acquired. The velocity power spectra are complicated and variable. There is substantial evidence that the variations are solar-like p-mode oscillations. At least 10 frequencies have been identified, over the range 8.3 to 1.7 days. A tell-tale spectrum of evenly spaced modes is apparent, yielding a value for Δv₀ ≈ 1.2 μHz. The average power spectrum peaks near 3 days, approximately as expected from the acoustic cut-off frequency. There is a broad envelope of power with a distribution reminiscent of that seen in the Sun. The oscillations do not maintain phase coherence and they show abrupt discontinuities, indicating that something is disrupting them, as in the Sun. Coherence of the modes is estimated to be a few weeks to a few months. Driving is likely to be due to stochastic excitation by turbulent convection. Arcturus may be one of the first analogues of solar-like oscillations and/or the first member of a new class of variable stars. Because Arcturus is an evolved star of approximately solar mass, these oscillations will provide a test for stellar evolution theory, as well as for asteroseismology and the study of driving mechanisms for stellar oscillations.

Lorqu'une étoile a des compagnons planétaires, elle décrit un mouvement quasi épicycloïdal autour du centre de masse du système. Si l'orientation du plan de l'orbite le permet, un observateur situé sur la Terre peut détecter la composante de ce mouvement sur la ligne de visée grâce à l'effet Doppler. Il mesure ainsi la ``vitesse radiale de l'étoile''. Si cette vitesse présente des variations périodiques suffisamment claires, la présence de planètes peut être inférée et leurs orbites contraintes. Une des difficultés de l'analyse de telles mesures est qu'une combinaison de signaux de plusieurs planètes et de divers bruits peut être confondue avec l'effet d'une planète en réalité inexistante. Après avoir présenté les effets à prendre en compte pour analyser des données de vitesses radiales, nous abordons ce problème. Pour limiter son occurrence, nous utilisons un algorithme de poursuite de base modifié, dont on démontre l'efficacité sur des signaux réels et simulés. Nous abordons ensuite le problème de l'estimation des paramètres orbitaux pour un système donné ainsi que leur distribution pour une population de planètes. On s'intéresse en particulier à l'excentricité, dont on montre qu'elle est d'autant plus surestimée que le modèle du signal est mauvais. Nous proposons des solutions pour une estimation robuste des paramètres orbitaux
When a star is orbited by planetary companions, it describes a nearly epicyclic motion around the center of mass of the system. When the orientation of the orbital plane is appropriate, an observer on Earth can measure the velocity of the star along the line of sight by Doppler effect. If this ``radial velocity'' presents clear enough periodic variations, the presence of planets can be inferred and their orbit can be constrained. Detection and estimation of orbits is made difficult by the photon noise, the unpredictable variations of luminosity of the star as well as instrumental faults. In particular, signals from several planets can add coherently with the noises and mimic the effect of a planet absent from the system. After listing the relevant effects to make inference on exoplanets from radial velocity data, we tackle this problem. To limit its rate of occurrence, we use a modified basis pursuit algorithm, allowing to search for several signals simultaneously. The efficiency of the method is demonstrated on real and simulated signals. We then address the problem of orbital parameters estimation for a given system, as well as the estimation of their distribution on a planet population. We look in detail at the eccentricity, and show that its overestimation increases as the model moves away from the correct one. We suggest methods for robust inference of orbital parameters

Understanding the asymmetry in core collapse supernova explosions is pointed out by various astrophysicists as it is the key factor in determining the observational properties of the pulsars. The initial kick given by the ex- plosion to the pulsar affects its spin period and space velocity. Up to now, although the observations do not show a direct relation between the observational features of the pulsar and its space velocity, they show a clear relation between the spin period and the magnetic field strength, hence its radiation processes. In this thesis, as the method, tracing the companions of progenitors if they were in close binaries, which becomes a runaway star after the supernova explosion was chosen. Over the candidates selected in Guseinov et al (2005), the spectral types of 11 runaway candidates from 7 supernova remnants determined through analyzing their spectroscopic observations. Radial velocity determination was applied to the discovered B6V type star GSC 03156-01430 inside the supernova remnant G78.2+2.1. Also by studying the proper motion data, we compared the motion of the runaway star and the related pulsar in order to determine the asymmetry in the supernova explosion. The neutron star PSR 2021+4026 is moving with a 2-D velocity of &sim
580 km/s with respect to the rest frame of its birth association Cyg OB9. &sim
550 km/s more than expected in the symmetric case. Re-constructing the pre-supernova binary shows that the asymmetry in the supernova explosion does not depend on the binarity.

The study of spectroscopic binaries is by no means a new area of study. The Doppler shifting of spectral lines as the stars orbit around each other is now able to be measured very precisely. Binary stars give a reliable means of determining stellar parameters such as the mass. A star's mass is one of the most dominant factors in determining its evolution. Stars for study in this thesis were selected from SB9 (the ninth catalogue of spectroscopic binaries). They were chosen on criteria such as apparent visual magnitude, orbital period, orbital solution grade, equatorial velocity and position. Only stars with poor to average orbital solutions were chosen as it is these orbits which need the most work done. In total 6 spectroscopic binary systems were chosen for study in this thesis. Four single lined spectroscopic binaries (HD 70958, HD 110318, HD 122223 and HD 141544) and two double line spectroscopic binaries (HD 110317 and HD 148704). Unfortunate observing conditions meant that adequate phase coverage of HD 110317 and HD 110318 was not achieved. Adequate phase coverage of the star HD 122223 was also not achieved but this is likely a result of the period being about three years and not about 207 days as quoted in the catalogue. Observations were carried out with the HERCULES spectrograph and the 1-metre McLellan telescope at the Mt John University Observatory from December 2007 until September 2008. Radial velocities were than measured from these spectra with HRSP3 and then orbital solutions were derived. Orbital solutions have been derived for the single-lined systems HD 141544 and HD 70958. The precision of HD 141544 was much better than HD 70598. This is because HD 70958 is complicated by differential rotation and possible chromospheric activity. The orbital solution of the double lined system HD 148704 was obtained by using CARTopt and not TODCOR as is common, with good results. HD 122223 is included even though only six spectra were obtained as it will be evident that the current orbital solution should be rejected in favour of the previous solution obtained in 1936 by Christie. Although the amount of data was not as large as was hoped, significant improvements of the orbital solutions were obtained. The secondary component of HD 148704 had only previously being detected in a very few spectra but now has a good orbital solution. Errors on all parameters have been decreased and tighter limits have been placed on the secondary components of the single lined systems. The mass ratio of the components of HD 148704 was also determined very accurately and calculation of the inclination from photometry may allow accurate masses to be determined.

This thesis concerns the cataloguing and characterisation of extrasolar planets, an important topic given its potential to inform theories of planet formation and evolution, and its relevance for future studies defining and assessing the habitability of other worlds. The first aspect of the study is the calculation of orbits, using radial velocity measurements coupled with Bayesian and Markov chain Monte Carlo methods, to produce a catalogue of orbital elements for a sizeable sample of planets. This constitutes a self-consistent, uniformly-derived catalogue, useful for statistical planetary population and formation studies, to be contrasted with other databases of planetary parameters, which are in general compilations of measurements from different sources and using various techniques. The orbital elements determine important star-on-planet forcings (for example ultra-violet irradiation, which has significant impacts on planetary (photo)chemistry and dynamics), and this study also looks at characterising planets explicitly in terms of their atmospheres. A 1D radiative transfer model for planetary transmission spectroscopy has been produced, and made freely-available for use by the community. This method is particularly useful since it allows the retrieval of first-order abundances of trace atmospheric molecules, which in turn can be used to estimate parameters such as the C/O ratio, potentially providing further constraints on planetary formation processes. The code in question has been validated by comparison to models in the literature, and applied to several real planetary atmospheres. It has also been extended by incorporating a method to estimate the opacity due to scattering particles in clouds and haze layers. If present in an atmosphere such phenomena can lead to the persistence of various parameter degeneracies, and limit the extent to which inferences can be drawn from spectra (leading to potentially order-of-magnitude errors in estimates of molecular abundances). Future extensions to this work could include the development of an automated inversion framework, utilising joint Bayesian/Markov chain Monte Carlo techniques to explore the parameter space of all relevant atmospheric quantities in order to retrieve a complete solution that is consistent with observations.

Radial velocity measurements are critical in finding and confirming exoplanets. To confine the parameters of the planet we naturally want to minimise the errors on the measurement. However the observed measurement error is now on the same order as the precision of the instrument. This so called jitter is related to the stellar activity (Wright 2005), i.e. the magnetic field of the star. In this paper we investigate if we can discover any correlation between the radial velocity variation and the magnetic activity of the star using HARPSpol spectra for the two stars Epsilon Eridani and GJ674.

Terzan 5 è un ammasso globulare posto nel Bulge della Via Lattea. Indagini fotometriche ad alta precisione (Ferraro et al. 2009, Origlia et al. 2013) hanno evidenziato tre distinte popolazioni stellari, con metallicità compatibili con quelle delle stelle del Bulge Galattico. La presenza di popolazioni multimetalliche differenzia Terzan 5 da tutti gli altri ammassi globulari conosciuti della Via Lattea e suggerisce una storia evolutiva molto più complessa e violenta. Questo lavoro si è concentrato sulla caratterizzazione dal punto di vista cinematico e chimico dell'alone esterno di Terzan 5 e del complesso ambiente nel quale è immerso, proseguendo e approfondendo l'indagine iniziata da Massari et al. (2014b) su circa 600 stelle del Bulge poste oltre il raggio mareale del sistema. Sono state selezionate 6042 stelle, con caratteristiche fotometriche compatibili con le componenti di Terzan 5, entro un raggio di 2° dal centro del sistema, e acquisiti 13500 spettri a media risoluzione (R=4400), nella banda I, con lo spettrografo multioggetto AAOmega dell'Australian Astronomical Observatory. In questa tesi viene descritta la riduzione dei dati, la misura di valori affidabili di velocità radiali (RV), la determinazione della metallicità facendo uso di un indice di metallicità spettrale e infine l'analisi e l'interpretazione dei cataloghi di RV e di metallicità ottenuti. Si è evidenziata l’impronta cinematica e chimica dell’alone esterno di Terzan 5; si sono caratterizzate le proprietà cinematiche e chimiche del campo circostante e di sottostrutture fino a scale di 10’; sono state confermate le proprietà chimiche delle stelle del Bulge e gli andamenti evidenziati da Massari et al. (2014b) ed è stata osservata la componente cinematica ad alta velocità scoperta da Nidever et al. (2012), a ogni latitudine galattica del campo.

L'exoplanètologie commence à s’intéresser aux naines M afin de détecter et caractériser des planètes. Ces étoiles sont les plus communes; leur petite taille facilite la détection de petites planètes; et les planètes dans la zone habitable sont plus faciles à détecter grâce à leur proximité à l'étoile. La population émergente de planètes de naines M montre des caractéristiques intrigantes par rapport à celle des étoiles FGK. Cette thèse a pour but explorer la détection de planètes de naines M par vitesses radiales visibles et proche infrarouges. J'ai aussi analysé la population de planètes de naines M au début et fin de la thèse. Dans le visible, j'ai travaillé avec le spectrographe SOPHIE (OHP), en tant que membre du consortium SOPHIE exoplanètes qui mène des programmes de recherche d'exoplanètes, dont l'un d'eux cherche des planètes autour de naines M. J'ai adapté un algorithme de calcul des vitesses radiales à ses cibles et analysé les données résultantes. J'ai confirmé la présence de signaux périodiques qui, bien que présents dans l'analyse standard, étaient partiellement noyés dans le bruit. Quatre nouvelles planètes ont été publiées. J'ai étudié des indices d'activité stellaire en identifiant les plus adaptés pour SOPHIE. Dans le proche infrarouge, j'ai travaillé avec le spectropolarimètre SPIRou (CFHT). Ce nouvel instrument est conçu pour observer des naines M, qu'irradient principalement dans l'infrarouge. J'ai travaillé sur le système de réduction des données, particulièrement sur la solution en longueur d'onde, crucial pour mesurer des vitesses radiales précises. J'ai développé et testé plusieurs méthodes pour combiner les différentes sources de calibration
Exoplanet science has begun to focus on M-dwarf stars for exoplanet detection and characterisation. They are the most common stars in the galaxy; their small size means smaller exoplanets can be detected; habitable zone planets are easier to detect as it is closer to the star. The emerging population of M dwarf planets shows intriguing characteristics compared to those hosted by FGK stars. The aim of this thesis is to explore the detection of exoplanets around M dwarfs via the radial velocity method, in both the near infra-red and visible domains. I also performed analyses of the known population of planets around M dwarfs at the start of the thesis and at its conclusion. In the visible, I worked with the SOPHIE spectrograph at the OHP, as part of the SOPHIE exoplanets consortium. This group leads several exoplanet surveys, one of which searches for planets around M dwarfs. I adapted a template-matching algorithm to its targets, and analysed the resulting radial velocities. I confirmed the significance of periodic signals that, while apparent in the standard analysis, were partially hidden by noise. Four new exoplanets have been published. I studied stellar activity indicators, identifying those most suited to SOPHIE spectra. In the near infrared, I worked with the SPIRou spectropolarimeter at the CFHT. This new instrument was conceived for observing M dwarfs, which emit most of their radiation in the infrared. I worked on the data reduction pipeline, specifically on the wavelength solution (pixel position-wavelength correspondence), crucial for measuring precise radial velocities. I developed and tested ways to combine different wavelength calibrators

A system has been developed at the Mt John University Observatory to enable relative radial velocities of solar-type stars to be obtained with a characteristic random error of 55 m/s. The high radial-velocity precision has been achieved by interfacing a single optical fibre feed between the telescope and spectrograph, which has enabled the spectrograph to be mounted in a thermally and mechanically stable configuration and has virtually eliminated guiding errors. Using this system, a programme of observation of 29 solar-type stars and 10 giant International Astronomical Union radial-velocity standard stars was carried out over 2.5 years with a view to the detection of low-mass companions to the dwarf stars. One star, HR3220, turned out to have a previously-undiscovered stellar companion but no dwarfs showed obvious radial-velocity variability suggesting the presence of sub-stellar companions, although β Hyi showed a possible variation. This is despite the programme's sensitivity to the discovery of companions of mass 20 M₄ or greater in orbits of periods less than about 8 years (and larger masses in longer period orbits). In contrast, at least half the giant 'standard' stars were variable in radial velocity. Four and possibly five of the giant standards are probably intrinsic (pulsating) red or yellow (Walker et al. 1989) variables. Two further standards, β Aqr and δ Sgr, showed long-period variability suggestive of companions of indeterminable but low mass. The lack of brown dwarfs observed in this programme is consistent with the results of other recent surveys. High-mass brown dwarfs appear to be rare as companions to stars and are probably rare in the field as well. They are unlikely to contribute significantly to the local mass density. Low-mass brown dwarfs (or high-mass planets) seem to be rare in orbits closer than 10 AU but could yet be found to abound in wider orbits or in the field.

We are developing a stable and precise spectrograph for the Large Binocular Telescope (LBT) named "iLocater." The instrument comprises three principal components: a cross-dispersed echelle spectrograph that operates in the YJ-bands (0.97-1.30 mu m), a fiber-injection acquisition camera system, and a wavelength calibration unit. iLocater will deliver high spectral resolution (R similar to 150,000-240,000) measurements that permit novel studies of stellar and substellar objects in the solar neighborhood including extrasolar planets. Unlike previous planet-finding instruments, which are seeing-limited, iLocater operates at the diffraction limit and uses single mode fibers to eliminate the effects of modal noise entirely. By receiving starlight from two 8.4m diameter telescopes that each use "extreme" adaptive optics (AO), iLocater shows promise to overcome the limitations that prevent existing instruments from generating sub-meter-per-second radial velocity (RV) precision. Although optimized for the characterization of low-mass planets using the Doppler technique, iLocater will also advance areas of research that involve crowded fields, line-blanketing, and weak absorption lines.

Large astronomical facilities usually provide data reduction pipeline designed to deliver ready-to-use scientific data, and too often as- tronomers are relying on this to avoid the most difficult part of an astronomer job Standard data reduction pipelines however are usu- ally designed and tested to have good performance on data with av- erage Signal to Noise Ratio (SNR) data, and the issues that are related with the reduction of data in the very low SNR domain are not taken int account properly. As a result, informations in data with low SNR are not optimally exploited. During the last decade our group has collected thousands of spec- tra using the GIRAFFE spectrograph at Very Large Telescope (Chile) of the European Southern Observatory (ESO) to determine the ge- ometrical distance and dynamical state of several Galactic Globular Clusters but ultimately the analysis has been hampered by system- atics in data reduction, calibration and radial velocity measurements. Moreover these data has never been exploited to get other informa- tions like temperature and metallicity of stars, because considered too noisy for these kind of analyses. In this thesis we focus our attention on data reduction and analysis of spectra with very low SNR. The dataset we analyze in this thesis comprises 7250 spectra for 2771 stars of the Globular Cluster M 4 (NGC 6121) in the wavelength region 5145 − 5360Å obtained with GIRAFFE. Stars from the upper Red Giant Branch down to the Main Sequence have been observed in very different conditions, including nights close to full moon, and reaching SNR ≃ 10 for many spectra in the dataset. We will first review the basic steps of data reduction and spec- tral extraction, adapting techniques well tested in other field (like photometry) but still under-developed in spectroscopy. We improve the wavelength dispersion solution and the correction of radial veloc- ity shift between day-time calibrations and science observations by following a completely different approach with respect to the ESO pipeline. We then analyze deeply the best way to perform sky sub- traction and continuum normalization, the most important sources respectively of noise and systematics in radial velocity determination and chemical analysis of spectra. The huge number of spectra of our dataset requires an automatic but robust approach, which we do not fail to provide. We finally determine radial velocities for the stars in the sample with unprecedented precision with respect to previous works with similar data and we recover the same stellar atmosphere parameters of other studies performed on the same cluster but on brighter stars, with higher spectral resolution and wavelength range ten times larger than our data. In the final chapter of the thesis we face a similar problem but from a completely different perspective. High resolution, high SNR data from the High Accuracy Radial Velocity Planet Searcher spectro- graph (HARPS) in La Silla (Chile) have been used to calibrate the at- mospheric stellar parameters as functions of the main characteristics of Cross-Correlation Functions, specifically built by including spec- tral lines with different sensitivity to stellar atmosphere parameters. These tools has been designed to be quick and to be easy to imple- ment in a instrument pipeline for a real-time determination, neverthe- less they provide accurate parameters even for lower SNR spectra.
Telescopi di grandi dimensioni usualmente rendono disponibili dei programmi per la riduzione dati che restituiscono all’astronomo dati già pronti per l’analisi scientifica, e sempre più spesso gli astronomi si appoggiano a questi programmi per evitare un lavoro lungo e diffi- cile. I programmi di riduzione dati standard sono però progettati per restituire buoni risultati su dati con buon Rapporto Segnale Rumore (RSR), e spesso i problemi legati alla riduzione di dati a basso RSR non sono presi in considerazione, con il risultato che le informazioni che contengono non sono adeguatamente utilizzate. Negli ultimi anni il nostro gruppo di ricerca ha collezionato migli- aia di spettri osservati con lo strumento GIRAFFE collegato al Very Large Telescope dell’Osservatorio Europeo del Sud in Cile, con lo scopo di determinare la distanza geometrica e lo stato dinamico di diversi Ammassi Globulari Galattici, ma in definitiva l’analisi è stata ostaco- lata da errori sistematici nella riduzione e calibrazione dei dati e nella misura delle velocità radiali. Inoltre questi dati non sono mai stati uti- lizzati per determinare altre informazioni come temperatura e metal- licità delle stesse, poiché considerati troppo rumorosi per questo tipo di analisi. In questa tesi concentriamo la nostra attenzione sulla riduzione dati ed analisi di spettri con bassissimo RSR. Il set di dati che analizziamo in questa tesi è composto da 7250 spettri per 2771 stelle dell’ammasso globulare M 4 (NGC 6121) ottenute con GIRAFFE nell’intervallo spet- trale 5145 − 5360Å. Stelle della parte superiore del Ramo delle Giganti Rossi fino alla Sequenza Principale sono state osservate in condizioni molto differenti, comprese notti con luna piena, fino ad raggiungere un valore limite di RSR ≃ 10 per molti spettri. La nostra analisi incomincia con i passi di base della riduzione dati ed estrazione degli spettri, adattando tecniche ben testate in altri campi (come la fotometria) ma ancora non ben sviluppate in spettroscopia. Continuiamo con il migliorare la soluzione della dispersione in lunghezza d’onda la correzione per piccoli spostamenti nelle velocità radiali di riferimento tra i dati di calibrazione presi durante il giorno e le osservazioni scientifiche seguendo un approccio completamente differente rispetto a quello ESO. Analizziamo poi la miglior maniera per effettuare la sottrazione del cielo e la normalizzazione del continuo, le due più importanti fonti rispettivamente di rumore ed errori sistematici nella misura delle velocità radiali nell’analisi chimica degli spettri. L’alto numero di spettri del nostro dataset richiede un approccio automatico ma robusto, che non manchiamo di fornire. Determiniamo infine per il nostro campione di stelle velocità radiali con una precisione mai vista in precedenza per dati di questo tipo e ritroviamo gli stessi parametri atmosferici di altri lavori svolti su stelle più brillanti, con dati a risoluzione spettrale maggiore e su intervalli di lunghezza d’onda dieci volte superiori a quello dei nostri dati. Nell’ultimo capitolo della tesi affrontiamo una problematica simile ma da una prospettiva completamente differente. Spettri ad alta risoluzione e ad alto RSR ottenuti con lo spettrografo HARPS sono stati usati per calibrare i parametri atmosferici stellari in funzione delle caratteristiche di funzioni di cross-correlazione specificatamente costruite includendo linee spettrali con diversa sensibilità ai parametri atmosferici stellari. Questi strumenti sono stati progettati per essere facilmente implementati un programma di riduzione dati, pur tuttavia senza sacrificare l’accuratezza dei parametri determinati anche per spettri a basso Rapporto Segnale Rumore.

Depuis la première détection d'une planète extrasolaire autour d'une étoile de type solaire par Mayor et Queloz (1995), plus de 1500 planètes ont été découverts. Actuellement il existe un énorme intérêt à découvrir et caractériser des planètes semblables à la Terre, en particulier celles situées dans la zone habitable de leur étoile hôte (définie comme la distance à l'étoile hôte où la température de la planète permet l'existence d'eau liquide à la surface). La détection de planètes de type terrestre, et la recherche de biomarqueurs dans leurs atmosphères sont parmi les principaux objectifs de l'astronomie du vingt et unième siècle. La méthode des vitesses radiales (VR), consistant à mesurer le mouvement réflexe de l'étoile induit par des planètes en orbite, est une remarquable technique pour atteindre cet objectif.Pour atteindre les précisions nécessaire à la detection de telles planètes il est absolument nécessaire de concevoir des spectrographes extrêmement stables, d'avoir une très bonne compréhension de l'activité stellaire (qui peut mimer l'effet d'une planète), d'effectuer un traitement soigneux de l'atmosphère terrestre (laquelle inévitablement laisse des empreintes dans les spectres acquis depuis le sol), et de disposer d'une puissante technique pour extraire, à partir des spectres, autant d'information Doppler que possible. La recherche de planètes orbitant autour des étoiles de très faible masse, plutôt qu'autour des étoiles de type solaire, permet d'aborder dès maintenant la détection de planètes de faible masse dans la zone habitable. En effet, en gardant tout les autres paramètres égaux, le mouvement réflexe (et donc l'amplitude de la variation VR) sera plus grande si l'étoile centrale est de très faible masse. De plus les naines M ont une plus faible luminosité que les étoiles de type solaire, il en resulte des périodes orbitales courtes des planètes dans la zone habitable (~50 jours pour les naines M contre ~360 jours pour des étoiles de type solaire), entraînant à nouveau en une plus grande amplitude des VR. Une précision de ~1 m/s en VR permet la détection d'une planète dans la zone habitable d'une naine M, alors que ~0.1 m/s sont nécessaire dans le cas d'une étoile de type solaire.Cette thèse vise à optimiser l'extraction de VR des spectres des naines M à haute résolution acquis avec le spectrographe HARPS (avec une possibilité d'applications futures sur d'autres instruments comme SOPHIE, HARPS-N et le prochain spectrographe infrarouge SPIRou - prochainement mis en service au CFHT). Les effets de l'activité stellaire des naines M seront également analysées, dans le contexte de la technique des VR. Divers traceurs d'activité stellaire sont utilisés pour rejeter des fausses détections ou pour étudier les relations entre l'activité magnétique et la rotation. Dans cette thèse (Chap. 3) je calibre pour la première fois le flux dans les raies H et K du Calcium en fonction de la luminosité bolométrique et je détermine la relation entre cet estimateur R'HK et la période de rotation des naines M. Dans le chapitre 4 je décris l'implémentation d'une méthode d'extraction de VR par une minimisation du Chi-deux entre un template spectral et les spectres observés. Je démontre que cette méthode est plus précise que celle classiquement utilisée. Les raies telluriques qui affectent les mesures VR sont prises en compte dans les procédures d'analyse. Ces méthodes sont testées sur des systèmes avec des candidats planétaires, je discuterais l'analyse de certains de ces systèmes
Since the first detection of an extrasolar planet orbiting a Sun-like star by Mayor and Queloz (1995), more than 1500 have been discovered. Enormous interest is currently focused on finding and characterising Earth-like planets, in particular those located in the habitable zone of their host star (defined as the distance from the host star where the planet temperature allows liquid water to flow on its surface). Both the detection of Earth-like planets, and the search for biomarkers in their atmospheres are among the main objectives of the twenty-first century's astronomy. The method known as radial velocities (RV), that consists in the measure of the star's reflex motion induced by orbiting planets, is a promising technique to achieve that quest.The main difficulties with the RV technique are the needs of an extremely stable spectrograph, a correct understanding of stellar activity (which can mimic the effect of a planet), a careful treatment of our Earth's atmosphere (which inevitable imprints spectra taken from the ground), and the need to dispose of a powerful algorithm to extract as much Doppler information as possible from the recorded spectra. Search for planets orbiting very low-mass stars (M dwarfs) can more easily reach the goal of detecting low-mass planets in the habitable zone of their parent star, compared to solar-type stars. Indeed, everything else being equal, a lower mass of the host star implies a larger reflex motion, and thus a larger RV amplitude. Moreover, the lower luminosity of M dwarfs compared to Sun-like stars, implies shorter orbital periods from planets in the habitable zone (~50 days against ~360 days, for M dwarfs compared to solar-type stars, respectively), resulting again in a larger RV amplitude. A RV precision of ~1 m/s allows a planet detection in the habitable zone of an M dwarf, whereas ~0.1 m/s is required in the case of a solar-type stars.This thesis aims to optimise the RV extraction from HARPS high-resolution spectra (and to open similar analysis on other instruments like SOPHIE, HARPS-N and the upcoming infrared spectrograph SPIRou -- to be commissioned to the 3.6-m CFH-Telescope). The effects of stellar activity will also be analysed, and contextualised in the RV technique. Stellar activity tracers are used to reject false detections or to study the relationships between the stellar magnetic activity and rotation. In this thesis (Chap.ref{chap:mag_activity}) I calibrate for the first time the ratio between the Ca textrm{small II} Htextrm{small &}K chromospheric lines and the bolometric luminosity for M dwarfs. I determine a relationship between the R^prime_{HK}-index and the rotation period of M dwarfs. In chapter~ref{chap:template_matching} I describe my algorithm to extract RVs through a chi^2-minimisation between a stellar template and the observed spectra. I demonstrate the improved accuracy of this method. Telluric spectral lines also affect the measurements of RV and are taken into account in the analysis procedures. I tested these methods on systems with planetary candidates, and for some systems, I took in charge the Keplerian analysis

Orbits of spectroscopic binary systems have been studied for more than a century. Over three thousand orbits of spectroscopic binary systems have been derived. These orbits are based on the radial velocities measured from the spectra recorded by a photographic plate to a high precision spectrum observed from a modern spectrograph. In many cases, the shape of the orbit was assumed to be circular, of hence the eccentricity is zero. This assumption is based on the fact that a small eccentricity (e < 0.1) measured from the observed data might be a result from the error of observations or from the intrinsic variation of a spectroscopic binary system. Sixteen southern spectroscopic binary systems, including twelve single-lined binaries and four double-lined binaries, were selected to study in this research program. These systems were assumed to have circular orbits or have very nearly circular orbits (e < 0.1) from their previous published solutions. The HERCULES spectrograph was used in conjunction with the 1-m McLellan telescope at Mt John University Observatory to collect the spectra of these systems. The observations, taken from October 2004 to August 2007, comprised about 2000 high-resolution spectra of spectroscopic binary systems and standard radial-velocity stars. Radial velocities of spectroscopic binary systems were measured from these spectra and orbital solutions of the systems were derived from these radial velocities. It was found that from HERCULES data, we are able to achieve high-precision orbital solutions of all the systems studied. The best-fit solutions can be improved as much as 70 times from the literature’s orbital solutions. It has been found that the precision of a system depends on the rotational velocities of the components as well as the level of their chromospheric activity. We are able to confirm the eccentricity in the orbit of only one of the selected spectroscopic binary systems, HD194215. Its eccentricity is 0.123 29 ± 0.000 78. The small eccentricities of other systems are not confirmed. There are four systems; HD22905, HD38099, HD85622 and HD197649, that have circular orbital solutions from the large errors in their measured eccentricities. Two systems, HD77258 and HD124425, have too small eccentricities, e = 0.000 85±0.000 19 and 0.002 60 ± 0.000 99 to be acceptable. An intrinsic variation is a presumed cause of the spurious eccentricities derived from the data of the other eight systems. Photometric data from Mt John University Observatory service photometry program, as well as the photometric data from the Hipparcos satellite and information of these systems from the literature, using various methods and instruments, give a wider view on the systems’ behaviour. It is possible that the spurious eccentricities derived for these systems result from the eclipsing behaviour of a system (HD50337), or from the nature of the components, such as, the distortion of their shape (HD352 and HD136905), their chromospheric activity (HD9053, HD3405, HD77137, HD101379 and HD155555), or stellar pulsation (HD30021). Models of the active chromosphere system, HD101379, have been simulated. An analysis of synthetic radial velocity data shows that spots on the star’s photosphere can cause a spurious eccentricity. The values of the spurious eccentricity and the longitude of periastron are dependent on the spot size, the spot temperature, and the position of the spots.

Extrasolar planetary surveys have discovered about 780 extrasolar planets and more than 100 multiple planetary systems to date, with the largest fraction of them being confirmed by the radial velocity detection method. Multiple planetary systems, especially those contain pairs of planets in mean-motion resonances, are particularly interesting because their current orbital architectures provide constraints for orbital evolution of planetary systems. Precisely determining the orbital and dynamical state of multiple planetary systems with radial velocity measurements is important. New results from an analysis of radial velocity data of the HD 82943 planetary system based on 10 years of measurements obtained with the Keck telescope is presented in this thesis. Previous studies have shown that the HD 82943 system has two planets that are likely in 2:1 MMR, with the orbital periods about 220 and 440 days (Lee et al. 2006). However, alternative fits that are qualitatively different have also been suggested, with the two planets in 1:1 resonance or the addition of a third planet possibly in a Laplace 4:2:1 resonance with the other two (Goździewski & Konacki 2006; Beaugé et al. 2008). Here based on the X^2 minimization method combined with parameter grid search, the orbital parameters and dynamical states of the qualitatively different types of fits have been investigated. The results support the coplanar 2:1 MMR configuration for this system and fits of the 1:1 resonance and the 3-planet Laplace resonance are ruled out according to X^2 statistic and dynamical instability. The inclination of the HD 82943 system is well constrained at about 20°C. The system contains two planets with masses of about 4.64 MJ and 4.66 MJ and orbital periods of about 219 and 442 days for the inner and outer planet, respectively. The best fit is dynamically stable with two resonance angles θ 1 = λ1 - 2λ2 + ϖ1 and θ 2 = λ1 - 2λ2 + ϖ 2 librating around 0°. Based on the best fit, the origin of the 2:1 MMR of the HD 82943 planetary system has been explored by N-body simulations with forced inward migration of the outer planet. This research has demonstrated the importance of dynamical fitting for multiple planetary systems with radial velocity measurements. It also fulfills the cases of planetary systems in mean-motion resonances such that more generic understanding of the orbital evolution of planetary systems can be obtained.
published_or_final_version
Earth Sciences
Master
Master of Philosophy

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 36) and index.
The intent of this project was to determine the relationship between the number of radial velocity observations of an Earth-twin exoplanet and the error in the mass calculated from the detected signal. If the planet's period is known through prior transit observations, the mass may be measured by radial velocity more accurately; this project tested and measured the conditions for this error reduction. Simulated sets of radial velocity data taken by HARPS (accurate to 1 m/s) for an Earth-mass planet in a circular, edge-on, 1 AU orbit around a Sun-like star were used with a least-squares fit to measure the amplitude of the sinusoidal radial velocity curve. The three conditions in which the mass fit was compared were: evenly-spaced observations with the period unknown; evenly-spaced observations with the period known; and an unevenly-spaced observation method in which observation times are chosen to be very frequent and clustered around the peaks of the radial velocity curve. For evenly-spaced observations, knowledge of the period did not reduce the error in the mass measurement compared to the period-unknown case, though it did allow for the elimination of the false-negative detection case. When observations were evenly spaced, the percent error in the detected mass had a power law relationship with the number of observations of [sigma]%error 1250=N -⁰.⁵. However, when using the knowledge of the period from transits to choose clustered observation times near the peaks of the curve, the error in the mass was reduced by about 20% for the same number of total observations, and was thus approximated by the power law [sigma]%error = 1030N-⁰.⁵. This indicates that if the period of a low-mass planet is known through transits, the use of clustered observations allows its mass to be measured more accurately with the same number of radial velocity observations than if the period were unknown.
by Allison L. Moberger.
S.B.

Molecular and cluster anions have been investigated using photoelectron velocity-map imaging spectroscopy to study the nature of electrons in radical species. We report a negative-ion photoelectron imaging study of benzonitrile and several of its hydrated, oxygenated, and homo-molecularly solvated cluster anions. The photodetachment transition from the unsolvated benzonitrile anion to the X̃¹A₁ state of the neutral peaks at 58 ± 5 meV. The electron affinity (EA) of the lowest excited electronic state of benzonitrile, ã³A₁, is determined as 3.41 ± 0.01 eV. The next excited state, the open-shell singlet ùA₁, is found about an electron-volt above the triplet, corresponding to a vertical detachment energy of 4.45 ± 0.01 eV. The step-wise and cumulative solvation energies of benzonitrile anions by several types of species were determined, including homo-molecular solvation by benzonitrile, hydration by 1–3 waters, oxygenation by 1–3 oxygen molecules, and mixed solvation by various combinations of O₂, H₂O, and benzonitrile. Ethylene has been shown to be a degradation product following the 1-e⁻ attachment to ethylene carbonate. As a solvent molecule for (O₂)^(□), our photoelectron imaging study shows a relatively small solvation energy of ≤0.24 eV for the expected 𝜋-𝜋 interaction in the ((O₂)^(□))(C₂H₄) cluster anion. The EA of the O₂(C₂H₄) cluster was measured at 0.69 ± 0.01 eV, while the 𝑋³A″ ← 𝑋²A″ photodetachment transition shows a 1400 ± 100 cm⁻¹ vibrational progression in the 1064 nm spectrum. Negative-ion photoelectron imaging was used to investigate the substituted carbene derivative of fluoroacetonitrile. We report a closed-shell singlet ground state for the cyanofluorocarbene, FCCN, with an adiabatic electron affinity EA = 2.081 ± 0.002 eV and a singlet-triplet gap of ΔEₛ₋ₜ = 0.42 ± 0.04 eV. The open-shell singlet ¹A″ state was also observed experimentally. We find that the experimentally measured ΔEₛ₋ₜ of FCCN agrees well with the general trend of similar carbenes. We report preliminary results on the photoelectron imaging of phenylcarbene, cyanophenylcarbene, and chlorophenylcarbene anions. Triplet phenylcarbene is observed to have an EA of ≤0.83 eV, considerably lower than the previously indirectly-determined value. Transitions to the singlet and triplet ground state of both cyanophenylcarbene and chlorophenylcarbene are observable, though unidentified bands make full assignment difficult. Cyanophenylcarbene is found to have a triplet ground-state, with a tentative EA of 2.04 eV. Chlorophenylcarbene is found to have a singlet ground-state. The phenyl-group is found to favor the singlet state slightly. The cyanofluoromethyl radical, FC(H)CN, was estimated to have an EA of 1.53 ± 0.08 eV, by a combination of experimental and theoretical results.. With similar methodology, we report the adiabatic electron affinity of the cyanobenzyl radical, EA(PhCHCN) = 1.90 ± 0.01 eV, and assign an upper limit of the EA for the chlorobenzyl radical, EA(PhCHCl) ≤ 1.12 eV. These values were used to estimate the C-H bond dissociation energy (BDE)s for these substituted methanes. Fluoroacetonitrile was found to have a BDE of D𝐻₁₉₈ = 90.7 ± 2.8 kcal mol^(□1). The C-H bond dissociation energies at the benzyl-α sites of the phenylmethanes are determined as 80.9 ± 2.3 kcal mol⁻¹ for benzyl nitrile and an upper limit of 84.2 kcal mol⁻¹ for benzyl chloride. These results are discussed in terms of substituent interactions in a simple MO framework and in relation to other similar molecules, including recently reported results for chloroacetonitrile. The 532 nm photoelectron spectrum of glyoxal provides the first direct spectroscopic determination of the adiabatic electron affinity, EA = 1.10(2) eV. This assignment is supported by a Franck-Condon simulation of the experimental spectrum that successfully reproduces the observed spectral features. The vertical detachment energy (VDE) of the glyoxal radical anion is determined as VDE = 1.30(4) eV. The EA of methylglyoxal is determined as ≤0.8 eV based on the signal-to-noise ratio of the 𝑋¹A′←𝑋²A″ transition, with a VDE = 1.28(4) eV. The EA of the a³A″ ← X²A″ and 𝐴¹A″ ← 𝑋²A″ transitions are determined as 3.28(3) eV and 3.614(5) eV respectively. The intrinsically short-lived ethylenedione molecule (OCCO) was observed and investigated using anion photoelectron spectroscopy. The adiabatic electron affinity of its ³Σg^(□) ground state is 1.936(8) eV. The vibrational progression with a 417(15) cm⁻¹ frequency observed within the triplet band corresponds to a trans-bending mode. Several dissociative singlet states are also observed, corresponding to two components of the ¹Δg state and the ¹Σg⁺ state. The experimental results are in agreement with the theory predictions and constitute the first spectroscopic observation and characterization of the elusive ethylenedione molecule. Two glyoxal derivatives related to the ethylenedione anion (OCCO⁻), ethynediolide (HOCCO⁻) and glyoxalide (OHCCO⁻), were studied. These anions provide access to the corresponding neutral reactive intermediates: the HOCCO and OHCCO radicals. In the HOCCO/OHCCO anion photoelectron spectrum, we identify several electronic states of this radical system and determine the adiabatic electron affinity of HOCCO as 1.763(6) eV. This result is compared to the corresponding 1.936(8) eV value for ethylenedione (OCCO). Initial attempts were made to detect and observe the dicyanoacetylene anion, NCCCCN⁻, by photoelectron imaging. While it is believed the experimental design path of H₂⁺ abstraction from fumaronitrile is sound, no spectral signature can be assigned to NCCCCN⁻. Calculations targeting the low-lying transitions from the anion indicate that the molecule should have a significantly positive electron affinity and at least the ground state should be accessible with the currently available laser sources. The cluster ion O₂(N₂O)⁻ of the same nominal mass as NCCCCN⁻ is identified as an interfering ion and ideas have been proposed for resolving this difficulty.

We report on the scrambling performance and focal-ratio-degradation (FRD) of various octagonal and rectangular fibers considered for MAROON-X. Our measurements demonstrate the detrimental effect of thin claddings on the FRD of octagonal and rectangular fibers and that stress induced at the connectors can further increase the FRD. We find that fibers with a thick, round cladding show low FRD. We further demonstrate that the scrambling behavior of non-circular fibers is often complex and introduce a new metric to fully capture non-linear scrambling performance, leading to much lower scrambling gain values than are typically reported in the literature (<1000 compared to 10,000 or more). We find that scrambling gain measurements for small-core, non-circular fibers are often speckle dominated if the fiber is not agitated.

In this work we present the development of observational techniques and data analysis for the follow-up of RV-detected exoplanet candidates and low-mass companions. We observed the exoplanet candidate systems HD 136118 and HD 33636, for which we present high-cadence radial velocity data obtained with the High Resolution Spectrograph on the Hobby-Eberly Telescope, and relative astrometry with the FGS-1r instrument on the Hubble Space Telescope. We performed a simultaneous analysis of these data in order to characterize the orbit of the companions thoroughly. This establishes the actual mass of HD 136118 b, M$_b$=63$^{+22}_{-13}$M$_J$, in contrast to the minimum mass determined from the radial velocity data only, M$_b$ sin \textit{i} $\sim$12 M$_J$. Therefore, the low-mass companion to HD 136118 is now identified as a likely brown-dwarf residing in the "brown-dwarf desert". Our results for HD 33636 are consistent with those found in the literature. For the latter object we also present experimental infrared interferometric observations with the AMBER instrument at the Very Large Telescope Interferometer. We have identified visibility variations consistent with an additional light with flux ratio of 30\%. This result is incompatible with those obtained from the other two experiments, i.e. a binary system that is composed of a GO V primary star and an M-dwarf companion.
Neste trabalho são desenvolvidas técnicas observacionais e análise de dados para o estudo de candidatos a exoplanetas e companheiras de baixa massa detectados via velocidades radiais. Foram observados os sistemas HD 136118 e HD 33636. As observações incluem medidas de alta-cadência de velocidades radiais com o espectrógrafo de alta resolução do telescópio Hobby-Eberly e medidas astrométricas com o Sensor de Guiagem Fina 1r do telescópio espacial HST. Os dados de ambos experimentos foram analisados simultaneamente para a caracterização completa da órbita das companheiras. O trabalho resultou na determinação da massa verdadeira de HD 136118 b, M$_b$=63$^{+22}_{-13}$M$_J$. Essa massa é relativamente maior que a massa mínima determinada anteriormente via velocidades radiais, M$_b$ sin \textit {i} $\sim$ 12 M$_J$. Portanto, HD 136118 b é identificada como uma provável anã-marrom que reside no "deserto das anãs-marrons". Os resultados obtidos para o sistema HD 33636 são consistentes com os encontrados na literatura. Para HD 33636, ainda foram realizadas medidas interferométricas experimentais no infravermelho com o instrumento AMBER e três telescópios do Very Large Telescope Interferometer . Foram identificadas variações na visibilidade interferométrica que são consistentes com uma luz adicional com razão de fluxos de aproximadamente 30\%. Este resultado é inconsistente com os resultados dos dois primeiros experimentos, ou seja, um sistema binário constituído por uma estrela primária do tipo GO V e uma companheira anã do tipo M.

La recherche et caractérisation de planètes extrasolaires en transit (i.e., qui passent devant leur étoile, vue depuis la Terre) est un domaine important de la planétologie car ces planètes permettent de contraindre les processus de formation, d'évolution et de migration des systèmes planétaires. Les missions spatiales CoRoT et Kepler ont permis, ces dernières années, de découvrir plusieurs milliers de candidats-planètes en transit. Cependant, ces candidats-planètes doivent être confirmés afin d'exclure tout scénario de faux-positifs pouvant imiter un transit d'une exo-planète. Pour cela, l'une des méthodes possible consiste à mener des observations complémentaires de vitesse radiale permettant de mesurer la masse et les paramètres orbitaux de l'objet qui transite et ainsi de pouvoir déterminer la nature des candidats-planètes. Au cours de ma thèse, je me suis attaché à résoudre la nature des candidats-planètes en transit issues des missions spatiales CoRoT et Kepler en menant des observations avec les spectrographes SOPHIE et HARPS, ce qui m'a permis d'identifier plusieurs nouvelles planètes extrasolaires en transit. J'ai également pu mesurer le taux de faux-positif de la mission Kepler, égal à 35% pour les candidats planètes-géantes à courte période orbitale, contredisant les précédentes estimations, beaucoup plus optimistes. J'ai également participé au développement d'un nouveau logiciel, "PASTIS", qui permet de valider statistiquement des planètes extrasolaires de faible masse, trop petites pour être caractérisées grâce aux spectrographes actuels. Ce logiciel permettra, à terme, de valider des dizaines de planètes de faible masse issues des missions CoRoT et Kepler
The search and characterization of transiting extrasolar planets (i.e. that pass in front of their host star, as seen from the Earth) is an important domain of planetology since these planets constrain the formation, evolution and migration process of planetary systems. The CoRoT (CNES) and Kepler (NASA) space missions permit, these last years, to discover several thousand of transiting-planet candidates. However, these planet candidates need to be confirmed in order to exclude all false positive scenario that can mimic a planetary transit. For that, one of the method consist on performing radial velocity follow-up observations to measure the transiting object's mass and orbital parameters and thus, to determine the nature of planet candidates.During my PhD thesis, I tried to resolve the nature of transiting planet candidates from the CoRoT and Kepler space missions. For that, I performed follow-up observations with the SOPHIE (OHP) and HARPS (ESO) spectrographs that were used to discover several new transiting extrasolar planets. I also measured the Kepler false-positive rate, equal to 35% for giant close-in exoplanet candidates, contradicting previous estimations, much more optimistic.I also participate to the development of a new software, called "PASTIS", which objective is to validate statistically low-mass transiting exoplanets out of reach for current spectrographs. This new tool will, in a near future, validate tens of low-mass planets from the CoRoT and Kepler space missions

Astronomers have been observing the night sky for many centuries to establish a better understanding for our universe and solar system. As part of their observations, astronomers characterize celestial bodies by fundamental properties such as mass, motion, and composition in order to provide further insight about the objects in question. As technology and science have evolved, the methods for measuring these properties have become more precise and accurate. One such methodology is known as spectroscopy, and it is a significant tool for observational astronomy. In this paper, we shall describe how we used astronomical spectroscopy to determine orbital and rotational velocities for various objects in our solar system. This method was implemented specifically using the facilities of the Harry D. Powell Observatory on the campus of East Tennessee State University.

Using high resolution optical spectra from Mount John University Observatory, Mount Stromlo Observatory and the Anglo-Australian Observatory, new, high accuracy radial velocity curves have been obtained for the two bright southern Cepheids l carinae (HR 3884) and beta doradus (HR 1922). An indepth investigation into period variations, cycle-to-cycle and long-term variations in the velocity curves and the reliability of the combination of velocity data from different observatories is carried out. Evidence for shock waves in the atmosphere of l car and resonance in beta dor is discussed. A grid of static model atmospheres incorporating plane-parallel geometry is compared with the observational spectra of both Cepheids, using line depth ratios, to determine the variation in effective temperature, surface gravity and microturbulence with phase. This information is used to determine the phase dependence of the surface-brightness for both Cepheids. The surface brightness variation with phase was found to follow an almost linear relationship. The distance to and radius of the Cepheids are determined using both a near-infrared version of the Barnes-Evans method and the Fourier Baade-Wesselink (BW) method. The derived radii and distances agree within the limits of the errors for both methods. The Fourier BW method was found to be very sensitive to phase shifts between the photometric and spectroscopic data and the derived distance highly dependent on the assumed reddening. An investigation into line profile variations in l car and beta dor has revealed the magnitude of these phenomena increase as the pulsational period of the Cepheid increases. It is estimated that line level variations introduce an additional uncertainty into derived radii of approximately 4 per cent for beta dor and 10 per cent in lcar. The uncertainty introduced into derived distances and radii by line profile asymmetries was estimated to be of the order of 6 per cent in beta dor and 10 per cent in l car. A comparative analysis is made of the hydrogen line radial velocity curves of l car and beta dor. A trend in the properties of these radial velocity curves with period has been revealed. In longer period Cepheids, the Halpha line seems to be forming in a region that does not partake in the pulsation as a whole, probably in a chromospheric shell. A quantitative analysis of the asymmetries in these lines reveal large redward asymmetries near maximum infall velocity. The magnitude of these asymmetries and the period for which they are present are larger in l Car than in beta dor. The blueward asymmetries in the Halpha line in l Car are comparable in magnitude to the redward asymmetries while the other lines exhibit only small blueward asymmetries. A qualitative analysis of these line profiles with phase reveal no conclusive evidence for line doubling in these Cepheids. Evidence of emission is found in the Halpha and H Beta lines of beta dor and l car. The strength and duration of the emission is found to be greater in the longer period Cepheid. Although it is likely that this emission is shock-related, theoretical work is needed to determine the exact origin of the emission. A non-LTE radiative hydrodynamic model for l Car has been created. This atmosphere will be used in further work to calculate synthetic spectral line profiles which will aid the interpretation of our observational results.

Using high resolution optical spectra from Mount John University Observatory, Mount Stromlo Observatory and the Anglo-Australian Observatory, new, high accuracy radial velocity curves have been obtained for the two bright southern Cepheids l carinae (HR 3884) and beta doradus (HR 1922). An indepth investigation into period variations, cycle-to-cycle and long-term variations in the velocity curves and the reliability of the combination of velocity data from different observatories is carried out. Evidence for shock waves in the atmosphere of l car and resonance in beta dor is discussed. A grid of static model atmospheres incorporating plane-parallel geometry is compared with the observational spectra of both Cepheids, using line depth ratios, to determine the variation in effective temperature, surface gravity and microturbulence with phase. This information is used to determine the phase dependence of the surface-brightness for both Cepheids. The surface brightness variation with phase was found to follow an almost linear relationship. The distance to and radius of the Cepheids are determined using both a near-infrared version of the Barnes-Evans method and the Fourier Baade-Wesselink (BW) method. The derived radii and distances agree within the limits of the errors for both methods. The Fourier BW method was found to be very sensitive to phase shifts between the photometric and spectroscopic data and the derived distance highly dependent on the assumed reddening. An investigation into line profile variations in l car and beta dor has revealed the magnitude of these phenomena increase as the pulsational period of the Cepheid increases. It is estimated that line level variations introduce an additional uncertainty into derived radii of approximately 4 per cent for beta dor and 10 per cent in lcar. The uncertainty introduced into derived distances and radii by line profile asymmetries was estimated to be of the order of 6 per cent in beta dor and 10 per cent in l car. A comparative analysis is made of the hydrogen line radial velocity curves of l car and beta dor. A trend in the properties of these radial velocity curves with period has been revealed. In longer period Cepheids, the Halpha line seems to be forming in a region that does not partake in the pulsation as a whole, probably in a chromospheric shell. A quantitative analysis of the asymmetries in these lines reveal large redward asymmetries near maximum infall velocity. The magnitude of these asymmetries and the period for which they are present are larger in l Car than in beta dor. The blueward asymmetries in the Halpha line in l Car are comparable in magnitude to the redward asymmetries while the other lines exhibit only small blueward asymmetries. A qualitative analysis of these line profiles with phase reveal no conclusive evidence for line doubling in these Cepheids. Evidence of emission is found in the Halpha and H Beta lines of beta dor and l car. The strength and duration of the emission is found to be greater in the longer period Cepheid. Although it is likely that this emission is shock-related, theoretical work is needed to determine the exact origin of the emission. A non-LTE radiative hydrodynamic model for l Car has been created. This atmosphere will be used in further work to calculate synthetic spectral line profiles which will aid the interpretation of our observational results.