59 research outputs found
Molecular parentage of radical species in the comae of comets
No full textUnderstanding the chemical composition of comets is of great interest to the scientific community. In this work, an integral field unit (IFU) spectrograph is used to detect emissions of C2, C3, CH, CN, and NH2. The azimuthal average profile (line integral of the column density as a function of radial distance from the center of the nucleus) is simulated by the Haser model. The Haser model simulates the outgassing and photo-dissociate of molecular species in the coma. In this work, the lifetime of the parent molecule in the photo-dissociation chain is set as a free parameter. The best fit parent lifetimes for observations of comets 4P/Faye, 10P/Tempel 2, and C/2009 P1 Garradd are obtained. The results are compared to parent lifetimes cited in other studies. HCN as a likely dominant parent for CN is eliminated. Constraints on likely parent molecules for C3 and NH2 are discussed
Diving Beneath the Sea of Stellar Activity: Chromatic Radial Velocities of the Young AU Mic Planetary System
No full textAbstract We present updated radial-velocity (RV) analyses of the AU Mic system. AU Mic is a young (22 Myr) early-M dwarf known to host two transiting planets— P b ∼ 8.46 days, R b = 4.38 − 0.18 + 0.18 R ⊕ , P c ∼ 18.86 days, R c = 3.51 − 0.16 + 0.16 R ⊕ . With visible RVs from Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical echelle Spectrographs (CARMENES)-VIS, CHIRON, HARPS, HIRES, M inerva -Australis, and Tillinghast Reflector Echelle Spectrograph, as well as near-infrared (NIR) RVs from CARMENES-NIR, CSHELL, IRD, iSHELL, NIRSPEC, and SPIRou, we provide a 5 σ upper limit to the mass of AU Mic c of M c ≤ 20.13 M ⊕ and present a refined mass of AU Mic b of M b = 20.12 − 1.57 + 1.72 M ⊕ . Used in our analyses is a new RV modeling toolkit to exploit the wavelength dependence of stellar activity present in our RVs via wavelength-dependent Gaussian processes. By obtaining near-simultaneous visible and near-infrared RVs, we also compute the temporal evolution of RV “color” and introduce a regressional method to aid in isolating Keplerian from stellar activity signals when modeling RVs in future works. Using a multiwavelength Gaussian process model, we demonstrate the ability to recover injected planets at 5 σ significance with semi-amplitudes down to ≈10 m s −1 with a known ephemeris, more than an order of magnitude below the stellar activity amplitude. However, we find that the accuracy of the recovered semi-amplitudes is ∼50% for such signals with our model.Abstract We present updated radial-velocity (RV) analyses of the AU Mic system. AU Mic is a young (22 Myr) early-M dwarf known to host two transiting planets— P b ∼ 8.46 days, R b = 4.38 − 0.18 + 0.18 R ⊕ , P c ∼ 18.86 days, R c = 3.51 − 0.16 + 0.16 R ⊕ . With visible RVs from Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical echelle Spectrographs (CARMENES)-VIS, CHIRON, HARPS, HIRES, M inerva -Australis, and Tillinghast Reflector Echelle Spectrograph, as well as near-infrared (NIR) RVs from CARMENES-NIR, CSHELL, IRD, iSHELL, NIRSPEC, and SPIRou, we provide a 5 σ upper limit to the mass of AU Mic c of M c ≤ 20.13 M ⊕ and present a refined mass of AU Mic b of M b = 20.12 − 1.57 + 1.72 M ⊕ . Used in our analyses is a new RV modeling toolkit to exploit the wavelength dependence of stellar activity present in our RVs via wavelength-dependent Gaussian processes. By obtaining near-simultaneous visible and near-infrared RVs, we also compute the temporal evolution of RV “color” and introduce a regressional method to aid in isolating Keplerian from stellar activity signals when modeling RVs in future works. Using a multiwavelength Gaussian process model, we demonstrate the ability to recover injected planets at 5 σ significance with semi-amplitudes down to ≈10 m s −1 with a known ephemeris, more than an order of magnitude below the stellar activity amplitude. However, we find that the accuracy of the recovered semi-amplitudes is ∼50% for such signals with our model
A Survey of Nearby M-Dwarfs with Robo-AO
No full textThis thesis presents the results of a survey of 913 M-dwarf stars from the Lepine and Shara Proper Motion (LSPM) catalog within 33 parsecs. Data for these targets was collected with the Robo-AO camera on the Palomar 60” telescope. In order to determine which stars were in bound systems, the images with multiple stars, first observed in 2012, were observed again in 2014 to examine changes in separation and position angles. Stars with little change in position with respect to one another suggest they are common proper motion pairs. The Washington Double Star (WDS) catalog and other resources were used to further determine binarity. This research was conducted to improve upon the statistics of nearby multiple M-dwarf systems. Identifying and confirming multiple systems at both wide and small separations will improve our understanding of M-dwarf formation by comparing these results to existing star formation models
The hinterland: compilation of nearby brown dwarfs and ultracool stars
No full textThis work is a compilation and analysis of ultracool dwarfs (UCDs) and brown dwarfs within 25 parsecs. It supplements the work of Stauffer et al. [2010] who updated the reputable and widely relied upon Third Catalog of Nearby Stars [Gliese & Jahreiß 1991] with revised coordinates and cross-matched each object with the 2MASS point source catalog [Cutri et al. 2003]. I began by incorporating newly discovered (post 1991) cool companions to Gliese-Jahreiß stars that had been previously undetectable. I then expanded the compilation to include isolated UCDs and other nearby systems with at least one UCD component. Multiple systems are a panacea for astrophysical problems: by applying Kepler’s laws, the model-independent mass of brown dwarfs and low mass stars can be determined and hence serve to constrain theory. This work puts this data into context by exploring the history of brown dwarf theory and reviewing open questions concerning their nature
A High-Contrast Imaging Survey of<i>SIM Lite</i>Planet Search Targets
No full textWith the development of extreme high contrast ground-based adaptive optics instruments and space missions aimed at detecting and characterizing Jupiter- and terrestrial-mass planets, it is critical that each target star be thoroughly vetted to determine whether it is a viable target, given both the instrumental design and scientific goals of the program. With this in mind, we have conducted a high-contrast imaging survey of mature AFGKM stars with the PALAO/PHARO instrument on the Palomar 200 inch telescope. The survey reached sensitivities sufficient to detect brown dwarf companions at separations of >50 AU. The results of this survey will be utilized both by future direct imaging projects such as GPI, SPHERE, and P1640 and indirect detection missions such as SIM Lite. Out of 84 targets, all but one have no close-in (0.45–1″) companions and 64 (76%) have no stars at all within the 25″ field of view. The sensitivity contrasts in the K_s passband ranged from 4.5 to 10 for this set of observations. These stars were selected as the best nearby targets for habitable planet searches because of their long-lived habitable zones (>1 billion years). We report two stars, GJ 454 and GJ 1020, with previously unpublished proper motion companions. In both cases, the companions are stellar in nature and are most likely M dwarfs based on their absolute magnitudes and colors. Based on our mass sensitivities and level of completeness, we can place an upper limit of ~17% on the presence of brown dwarf companions with masses >40 M_J at separations of >1″. We also discuss the importance of including statistics on those stars with no detected companions in their field of view for the sake of future companion searches and an overall understanding of the population of low-mass objects around nearby stars
Search for Terrestrial Planets with SIM Planet Quest
No full textSIM is an astrometric mission that will be capable of 1 microarcsec relative astrometric accuracy in a single measurement of approx.1000 sec. The search for terrestrial planets in the habitable zone around nearby stars is one of the main science goals of the project. In 2001, NASA through the peer review process selected 10 key projects, two of which had as its goal, the search for terrestrial planets around nearby stars. The two teams, one led by G. Marcy (UC Berkeley) and one lead by M. Shao (JPL), have an extensive preparatory science program underway. This paper describes the status of this activity as well as the technology status of SIM's narrow angle astrometry capability, to reach 1 uas in a single epoch measure and its ability to average multiple epoch measurements to well below 1 uas
Analysis of the dynamics of a "barra brava" and how the recognition and agency of a woman belonging to this "barra brava" interpelate
No full textEste trabajo nace de las reflexiones realizadas por parte de la autora que buscan analizar desde las experiencias vividas y por medio de narrativas cómo es la configuración de una barra brava como espacio social, el cual cuenta con dinámicas y lógicas propias y esencializadas que establecen una estructura social determinada, y cómo estas dinámicas interpelan el reconocimiento y la agencia de las mujeres que hacen parte de esta organización. Así mismo se busca entender las formas en las cuales se percibe la mujer dentro de la barra y como es el desarrollo de la autonomía con todo su entramado social, basada en el concepto de Corine Pelluchon y la tensión existente entre la autonomía con la estructura heterónoma que se impone desde el liderazgo masculino, en cada una de las situaciones vividas dentro de la barra. Se escogió como método de trabajo la narrativa ya que por medio de esta se forja conocimiento que se considera un aporte hacia la bioética desde el análisis teórico realizado confrontado con las experiencias que vive una mujer en un contexto que es dominado en su totalidad por los hombres. Encontrando que es precisamente este proceso de falta de reconocimiento y de alteraciones en el agenciamiento los que promueven que la autonomía entre en un conflicto dando lugar a su invalidación y que se establezcan relaciones heterónomas por la jerarquización existente basada en masculinidades que determinan el desarrollo de la barra.Magíster en BioéticaMaestríaThis work stems from the reflections made by the author who seek to analyze from lived experiences and through narratives what the configuration of a "barra brava" is like as a social space, which has its own and essentialized dynamics and logics that establish a determined social structure, and how these dynamics challenge the recognition and agency of the women who are part of this organization. Likewise, it seeks to understand the ways in which women are perceived within the "barra brava" and how is the development of autonomy with all its social fabric, based on the concept of Corine Pelluchon and the tension between autonomy with the heteronomous structure that is imposed from the male leadership, in each of the situations experienced within the bar. The narrative was chosen as the working method since through this knowledge is forged that is considered a contribution towards bioethics from the theoretical analysis carried out confronted with the experiences that a woman lives in a context that is dominated in its entirety by men . Finding that it is precisely this process of lack of recognition and alterations in the assemblage that promote autonomy entering a conflict, leading to its invalidation and establishing heteronomous relationships due to the existing hierarchy based on masculinities that determine the development of the "barra brava"
Analysis of the dynamics of a "barra brava" and how the recognition and agency of a woman belonging to this "barra brava" interpelate
No full textEste trabajo nace de las reflexiones realizadas por parte de la autora que buscan analizar desde las experiencias vividas y por medio de narrativas cómo es la configuración de una barra brava como espacio social, el cual cuenta con dinámicas y lógicas propias y esencializadas que establecen una estructura social determinada, y cómo estas dinámicas interpelan el reconocimiento y la agencia de las mujeres que hacen parte de esta organización. Así mismo se busca entender las formas en las cuales se percibe la mujer dentro de la barra y como es el desarrollo de la autonomía con todo su entramado social, basada en el concepto de Corine Pelluchon y la tensión existente entre la autonomía con la estructura heterónoma que se impone desde el liderazgo masculino, en cada una de las situaciones vividas dentro de la barra. Se escogió como método de trabajo la narrativa ya que por medio de esta se forja conocimiento que se considera un aporte hacia la bioética desde el análisis teórico realizado confrontado con las experiencias que vive una mujer en un contexto que es dominado en su totalidad por los hombres. Encontrando que es precisamente este proceso de falta de reconocimiento y de alteraciones en el agenciamiento los que promueven que la autonomía entre en un conflicto dando lugar a su invalidación y que se establezcan relaciones heterónomas por la jerarquización existente basada en masculinidades que determinan el desarrollo de la barra.Magíster en BioéticaMaestríaThis work stems from the reflections made by the author who seek to analyze from lived experiences and through narratives what the configuration of a "barra brava" is like as a social space, which has its own and essentialized dynamics and logics that establish a determined social structure, and how these dynamics challenge the recognition and agency of the women who are part of this organization. Likewise, it seeks to understand the ways in which women are perceived within the "barra brava" and how is the development of autonomy with all its social fabric, based on the concept of Corine Pelluchon and the tension between autonomy with the heteronomous structure that is imposed from the male leadership, in each of the situations experienced within the bar. The narrative was chosen as the working method since through this knowledge is forged that is considered a contribution towards bioethics from the theoretical analysis carried out confronted with the experiences that a woman lives in a context that is dominated in its entirety by men . Finding that it is precisely this process of lack of recognition and alterations in the assemblage that promote autonomy entering a conflict, leading to its invalidation and establishing heteronomous relationships due to the existing hierarchy based on masculinities that determine the development of the "barra brava"
A Technique To Derive Improved Proper Motions For Kepler Objects Of Interest
No full textWe outline an approach yielding proper motions with higher precision than exists in present catalogs for a sample of stars in the Kepler field. To increase proper-motion precision, we combine first-moment centroids of Kepler pixel data from a single season with existing catalog positions and proper motions. We use this astrometry to produce improved reduced-proper-motion diagrams, analogous to a Hertzsprung-Russell (H-R) diagram, for stars identified as Kepler objects of interest. The more precise the relative proper motions, the better the discrimination between stellar luminosity classes. Using UCAC4 and PPMXL epoch 2000 positions (and proper motions from those catalogs as quasi-Bayesian priors), astrometry for a single test Channel (21) and Season (0) spanning 2 yr yields proper motions with an average per-coordinate proper-motion error of 1.0 mas yr(-1), which is over a factor of three better than existing catalogs. We apply a mapping between a reduced-proper-motion diagram and an H-R diagram, both constructed using Hubble Space Telescope parallaxes and proper motions, to estimate Kepler object of interest K-band absolute magnitudes. The techniques discussed apply to any future small-field astrometry as well as to the rest of the Kepler field.NASA contract NAS5-26555NASA Office of Space Science NNX13AC07GNASA NNX13AC22G, NNX12AF76GNSF Astronomy and Astrophysics grant AST-1109612W. M. Keck FoundationAstronom
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