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Dissertations / Theses on the topic 'Low mass stars. Dwarf stars'

Author: Grafiati

Published: 4 June 2021

Last updated: 15 February 2022

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1

Krawchuk, Curtis A. P. "The determination of metallicity and temperature of low-mass stars using broad-band photometry." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0035/MQ27361.pdf.

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2

Riaz, Basmah. "A study of circumstellar disk properties in low-mass stars and brown dwarfs." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 129 p, 2008. http://proquest.umi.com/pqdweb?did=1597616011&sid=8&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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3

Marks, M., E. L. Martín, V. J. S. Béjar, et al. "Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes." EDP SCIENCES S A, 2017. http://hdl.handle.net/10150/625997.

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Context. One of the key questions of the star formation problem is whether brown dwarfs (BDs) form in the manner of stars directly from the gravitational collapse of a molecular cloud core (star-like) or whether BDs and some very low-mass stars (VLMSs) constitute a separate population that forms alongside stars comparable to the population of planets, for example through circumstellar disk (peripheral) fragmentation. Aims. For young stars in Taurus-Auriga the binary fraction has been shown to be large with little dependence on primary mass above approximate to 0.2 M-circle dot, while for BDs t

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4

Cardoso, Catia Vanessa Varejao. "Observational properties of brown dwarfs : the low-mass end of the mass function." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3592.

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Brown dwarfs are objects with sub-stellar masses that are unable to sustain hydrogen burning, cooling down through out their lifetimes. This thesis presents two projects, the study of the IMF of the double cluster, h & χ Persei, and the determination of the dynamical masses of the brown dwarf binary, ε Indi Ba, Bb. The study of a cluster’s population distribution gives us the opportunity to study a statistically meaningful population of objects over a wide range of masses (from massive stars to brown dwarfs), with a similar age and chemical composition providing formation and dynamical evoluti

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5

Henry, Todd Jackson. "A systematic search for low-mass companions orbiting nearby stars and the calibration of the end of the stellar main sequence." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185689.

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We have completed a search for low luminosity companions, including high mass brown dwarfs, to all M dwarfs known within eight parsecs of the sun, and north of -25°. We found six new companions orbiting the survey stars. The masses of the six new secondaries fall between 0.39 and 0.05 M(⊙). Three of the new companions, G208-44B, GL 623B and LHS 1047B, and one previously known secondary in the survey, Ross 614B, are brown dwarf candidates with masses ∼80 Jupiters (0.08 M(⊙)), the dividing line between stars and brown dwarfs. In addition, we provide infrared photometry at J, H and K for all 99 s

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6

Lew, Ben W. P., Daniel Apai, Yifan Zhou, et al. "CLOUD ATLAS: DISCOVERY OF PATCHY CLOUDS AND HIGH-AMPLITUDE ROTATIONAL MODULATIONS IN A YOUNG, EXTREMELY RED L-TYPE BROWN DWARF." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622769.

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Condensate clouds fundamentally impact the atmospheric structure and spectra of exoplanets and brown dwarfs, but the connections between surface gravity, cloud structure, dust in the upper atmosphere, and the red colors of some brown dwarfs remain poorly understood. Rotational modulations enable the study of different clouds in the same atmosphere, thereby providing a method to isolate the effects of clouds. Here, we present the discovery of high peak-to-peak amplitude (8%) rotational modulations in a low-gravity, extremely red (J-K-s = 2.55) L6 dwarf WISEP J004701.06+680352.1 (W0047). Using t

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7

Souto, D., K. Cunha, D. A. Garcia-Hernandez, et al. "Chemical Abundances of M-Dwarfs from the Apogee Survey. I. The Exoplanet Hosting Stars Kepler-138 and Kepler-186." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624381.

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We report the first detailed chemical abundance analysis of the exoplanet-hosting M-dwarf stars Kepler-138 and Kepler-186 from the analysis of high-resolution (R similar to 22,500) H-band spectra from the SDSS-IV-APOGEE survey. Chemical abundances of 13 elements-C, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, and Fe-are extracted from the APOGEE spectra of these early M-dwarfs via spectrum syntheses computed with an improved line list that takes into account H2O and FeH lines. This paper demonstrates that APOGEE spectra can be analyzed to determine detailed chemical compositions of M-dwarfs. Both

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8

Kenyon, Michael John. "Low mass stars and brown dwarfs around Ïƒ Orionis." Thesis, Keele University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409546.

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9

Cossburn, Martin R. "The study of low-mass stars and brown dwarfs." Thesis, University of Leicester, 1999. http://hdl.handle.net/2381/30616.

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This thesis describes the search for brown dwarfs in open clusters using optical and infrared photometry, optical spectroscopy and surveys using the Hubble Space Telescope (HST). It also includes an observational study of very low-mass stars (VLMS) using a filter combination (I and Z), unused previously in this field enabling the calibration of the colour (I--Z), for future survey work. Following a short introduction explaining the reasons for studying brown dwarfs this thesis reviews the theory of their formation and evolution and describes recent searches for brown dwarfs and their results.

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10

Pinfield, David J. "Low mass stars and brown dwarfs in open clusters." Thesis, University of Leicester, 1998. http://hdl.handle.net/2381/30612.

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This thesis describes several open cluster searches for very low mass stars (VLM) and brown dwarfs (BD) (M/M? < 0.08). With recent developments in charged coupled devices, it has become possible to survey open clusters to well into the BD regime. The principal aim of this work is to employ these new instruments to conduct such open cluster surveys, to investigate the properties of VLM and BD populations. The thesis begins with a short introduction, which describes the fundamental properties of brown dwarfs, relates research in this field to other areas of astronomy, and summarises the project

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11

Manjavacas, Elena, Dániel Apai, Yifan Zhou, et al. "Cloud Atlas: Discovery of Rotational Spectral Modulations in a Low-mass, L-type Brown Dwarf Companion to a Star." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/626404.

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Observations of rotational modulations of brown dwarfs and giant exoplanets allow the characterization of condensate cloud properties. As of now, rotational spectral modulations have only been seen in three L-type brown dwarfs. We report here the discovery of rotational spectral modulations in LP261-75B, an L6-type intermediate surface gravity companion to an M4.5 star. As a part of the Cloud Atlas Treasury program, we acquired time-resolved Wide Field Camera 3 grism spectroscopy (1.1-1.69 mu m) of LP261-75B. We find gray spectral variations with the relative amplitude displaying only a weak w

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12

Slesnick, Catherine Louise Brown Michael E. "1-10 Myr-old low mass stars and brown dwarfs in nearby star forming regions /." Diss., Pasadena, Calif. : Caltech, 2008. http://resolver.caltech.edu/CaltechETD:etd-08102007-161741.

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13

King, Robert R. "Low-mass stars and brown dwarfs : optical/infrared photometry and spectroscopy of low-mass stars and brown dwarfs in the Field and Young Clusters." Thesis, University of Exeter, 2009. http://hdl.handle.net/10036/97095.

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In this thesis I will present optical and near-infrared photometric and spectroscopic observations of an evolved field brown dwarf binary pair and of populations of low-mass stars in high-mass young stellar clusters and will compare them to stellar and substellar theoretical model predictions. Epsilon Indi Ba and Bb are the closest known brown dwarfs to the Earth, and, as such, make possible a concerted observational campaign to obtain a complete characterisation of two intermediate-age T dwarfs. Although some recent observations suggest substellar atmospheric and evolutionary models may be in

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14

Hambly, Nigel Charles. "Very low mass stars and brown dwarfs in galactic clusters." Thesis, University of Leicester, 1991. http://hdl.handle.net/2381/35905.

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This thesis describes searches for very low mass stars (0.3 > m/m > 0.08) and brown dwarfs (0.08 > m/m > 0.01) in the Pleiades and Carinae galactic open clusters using COSMOS automatic measures of Schmidt photographic plates. A broad introduction defines the problem and relates research in this area to other branches of astronomy; the second chapter presents a detailed review of the current observational and theoretical status of the subject; and the third chapter briefly describes the observational techniques employed. The results are presented in chapters four and five. The Pleiades results

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15

Steele, Iain A. "Photometry and spectroscopy of low mass stars and brown dwarfs." Thesis, University of Leicester, 1994. http://hdl.handle.net/2381/35798.

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This thesis describes an investigation of the faintest known proper motion members of the Pleiades star cluster. The primary aim of the work is an attempt to determine whether the lowest mass members of the cluster are brown dwarfs. A brief introduction outlines the fundamental properties of brown dwarfs and discusses the relation of research in this area to other branches of astronomy. The second chapter describes the basic principles of astronomical photometry and spectroscopy, the instruments used and the methods of data reduction. Chapter three gives a review of the current theory and obse

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16

Gallardo, José. "Physics of low mass stars, brown dwarfs and extrasolar planets." Lyon, École normale supérieure (sciences), 2007. http://www.theses.fr/2007ENSL0412.

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17

Viti, Serena. "Infrared spectrum of cool stars and sunspots." Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267576.

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18

Manjavacas, E., P. A. Miles-Paez, M. R. Zapatero-Osorio, et al. "Testing the existence of optical linear polarization in young brown dwarfs." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/624425.

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Linear polarization can be used as a probe of the existence of atmospheric condensates in ultracool dwarfs. Models predict that the observed linear polarization increases with the degree of oblateness, which is inversely proportional to the surface gravity. We aimed to test the existence of optical linear polarization in a sample of bright young brown dwarfs, with spectral types between M6 and L2, observable from the Calar Alto Observatory, and cataloged previously as low gravity objects using spectroscopy. Linear polarimetric images were collected in I and R band using CAFOS at the 2.2-m tele

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19

Yang, Hao, Dániel Apai, Mark S. Marley, et al. "EXTRASOLAR STORMS: PRESSURE-DEPENDENT CHANGES IN LIGHT-CURVE PHASE IN BROWN DWARFS FROM SIMULTANEOUS HST AND SPITZER OBSERVATIONS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621379.

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We present Spitzer/Infrared Array Camera Ch1 and Ch2 monitoring of six brown dwarfs during eight different epochs over the course of 20 months. For four brown dwarfs, we also obtained simulataneous Hubble Space Telescope (HST)/WFC3 G141 grism spectra during two epochs and derived light curves in five narrowband filters. Probing different pressure levels in the atmospheres, the multiwavelength light curves of our six targets all exhibit variations, and the shape of the light curves evolves over the timescale of a rotation period, ranging from 1.4 to 13 hr. We compare the shapes of the light cur

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20

Thompson, Simon. "Low mass stars, brown dwarfs and the initial mass function in Cepheus OB3b." Thesis, Keele University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288434.

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21

Bayo, Amelia, Viki Joergens, Yao Liu, et al. "First Millimeter Detection of the Disk around a Young, Isolated, Planetary-mass Object." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624481.

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OTS44 is one of only four free-floating planets known to have a disk. We have previously shown that it is the coolest and least massive known free-floating planet (similar to 12 M-Jup) with a substantial disk that is actively accreting. We have obtained Band 6 (233 GHz) ALMA continuum data of this very young disk-bearing object. The data show a clear unresolved detection of the source. We obtained disk-mass estimates via empirical correlations derived for young, higher-mass, central (substellar) objects. The range of values obtained are between 0.07 and 0.63 M-circle plus (dust masses). We com

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22

Gilhool, Steven H., Cullen H. Blake, Ryan C. Terrien, Chad Bender, Suvrath Mahadevan, and Rohit Deshpande. "The Rotation of M Dwarfs Observed by the Apache Point Galactic Evolution Experiment." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/626529.

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We present the results of a spectroscopic analysis of rotational velocities in 714 M-dwarf stars observed by the SDSS-III Apache Point Galactic Evolution Experiment (APOGEE) survey. We use a template-fitting technique to estimate v sin i while simultaneously estimating log g, [M/H], and T-eff. We conservatively estimate that our detection limit is 8 km s(-1). We compare our results to M-dwarf rotation studies in the literature based on both spectroscopic and photometric measurements. Like other authors, we find an increase in the fraction of rapid rotators with decreasing stellar temperature,

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23

Konopacky, Quinn Morgan. "Dynamics and multiplicity of brown dwarfs and young, low mass stars." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1997620861&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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24

Thackrah, Andrew David. "A photographic survey of very low mass stars and brown dwarfs." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/27522.

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This thesis presents a study of the very low mass stars and hypothesised brown dwarf population that straddle the end of the stellar main sequence. The current status of the physical and observational arguments for the existence of sub-stellar objects is reviewed and the most recent numerical models are assessed. The suitability of wide-field photographic plates as detectors of this type of object is investigated, a 150 square degree photographic survey is described and subsequent candidate observations are presented. It is found that for conventional survey-grade U.K. Schmidt plates, the dete

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Schmidt, Sarah J., Erika L. Wagoner, Jennifer A. Johnson, et al. "Examining the relationships between colour, T eff , and [M/H] for APOGEE K and M dwarfs." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/621724.

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We present the effective temperatures (T-eff), metallicities, and colours in Sloan Digital Sky Survey (SDSS), Two Micron All Sky Survey, and Wide-field Infrared Survey Explorer filters, of a sample of 3834 late-K and early-M dwarfs selected from the SDSS Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectroscopic survey ASPCAP (APOGEE Stellar Parameters and Chemical Abundances Pipeline) catalogue. We confirm that ASPCAP T-eff values between 3550 < T-eff < 4200 K are accurate to similar to 100 K compared to interferometric T-eff values. In that same T-eff range, ASPCAP metalli

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Miles-Paez, Paulo A., Stanimir A. Metchev, Aren Heinze, and Daniel Apai. "Weather on Other Worlds. IV. H alpha Emission and Photometric Variability Are Not Correlated in L0-T8 Dwarfs." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624337.

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Recent photometric studies have revealed that surface spots that produce flux variations are present on virtually all L and T dwarfs. Their likely magnetic or dusty nature has been a much-debated problem, the resolution to which has been hindered by paucity of diagnostic multi-wavelength observations. To test for a correlation between magnetic activity and photometric variability, we searched for Ha emission among eight L3-T2 ultra-cool dwarfs with extensive previous photometric monitoring, some of which are known to be variable at 3.6 mu m or 4.5 mu m. We detected Ha only in the non-variable

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27

Riddick, Fiona Clare. "A spectroscopic study of low-mass stars and brown dwarfs in Orion." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437013.

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28

Hendler, Nathanial P., Gijs D. Mulders, Ilaria Pascucci, et al. "Hints for Small Disks around Very Low Mass Stars and Brown Dwarfs." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624452.

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The properties of disks around brown dwarfs and very low mass stars (hereafter VLMOs) provide important boundary conditions on the process of planet formation and inform us about the numbers and masses of planets than can form in this regime. We use the Herschel Space Observatory PACS spectrometer to measure the continuum and [O I] 63 mu m line emission toward 11 VLMOs with known disks in the Taurus and Chamaeleon I star-forming regions. We fit radiative transfer models to the spectral energy distributions of these sources. Additionally, we carry out a grid of radiative transfer models run in

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Tata, Ramarao. "SEARCH, CHARACTERIZATION, AND PROPERTIES OF BROWN DWARFS." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3439.

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A trend in polarization as predicted by theoretical models was validated, and atmospheric dust grain sizes and projected rotational velocities for these objects were estimated. Comprehensive studies of UDs are proving to be crucial not only in our understanding of UDs but also for star and planet formation as brown dwarfs represent their lower and upper mass boundaries, respectively. Brown dwarfs (BD) were mere theoretical astrophysical objects for more than three decades (Kumar (1962)) till their first observational detection in 1995 (Rebolo et al. (1995), Nakajima et al. (1995)). These objec

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30

Deshpande, Rohit. "Search for gas giants around late-M dwarfs." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4640.

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The absolute radial and rotational velocities of our targets were also calculated. Values of rotational velocities indicate that M dwarfs are, in general, slow rotators. Using our result and that from literature, we extended our study of rotational velocities to L dwarfs. Our observations show an increase in rotational velocities from late M to L dwarfs. We also find that the mean periods of M dwarfs are less than 10 hours. In order to improve our precision in measuring relative radial velocity (RV), we employed the use of deconvolution method. With this method we were able to ameliorate relat

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31

Garcia, E. Victor, Thayne Currie, Olivier Guyon, et al. "SCExAO AND GPI Y JH BAND PHOTOMETRY AND INTEGRAL FIELD SPECTROSCOPY OF THE YOUNG BROWN DWARF COMPANION TO HD 1160." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623097.

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We present high signal-to-noise ratio, precise Y JH photometry and Y band (0.957-1.120 mu m) spectroscopy of HD 1160 B, a young substellar companion discovered from the Gemini NICI Planet Finding Campaign using the Subaru Coronagraphic Extreme Adaptive Optics instrument and the Gemini Planet Imager. HD 1160 B has typical mid-M dwarf-like infrared colors and a spectral type of M5.5(-0.5)(+1.0), where the blue edge of our Y band spectrum rules out earlier spectral types. Atmospheric modeling suggests HD 1160 B has an effective temperature of 3000-3100 K, a surface gravity of log g - 4-4.5, a rad

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32

Tottle, Jonathan. "Atmospheric and disk properties of young low mass stars and brown dwarfs : an infrared study." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/32111.

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We test state-of-the-art model atmospheres for young low-mass stars and brown dwarfs in the infrared, by comparing the predicted synthetic photometry over 1.2-24um to the observed photometry of M-type spectral templates in star-forming regions. In both early and late young M types, the model atmospheres imply effective temperatures (Teff) several hundred Kelvin lower than predicted by the standard Pre-Main Sequence spectral type-Teff conversion scale (where the latter is based on theoretical evolutionary models). We postulate that in the early M types this discrepancy arises from remaining unc

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33

Cook, Neil James. "M dwarfs from the SDSS, 2MASS and WISE surveys : identification, characterisation and unresolved ultracool companionship." Thesis, University of Hertfordshire, 2016. http://hdl.handle.net/2299/17244.

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The aim of this thesis is to use a cross-match between WISE, 2MASS and SDSS to identify a large sample of M dwarfs. Through the careful characterisation and quality control of these M dwarfs I aim to identify rare systems (i.e. unresolved UCD companions, young M dwarfs, late M dwarfs and M dwarfs with common proper motion companions). Locating ultracool companions to M dwarfs is important for constraining low-mass formation models, the measurement of substellar dynamical masses and radii, and for testing ultracool evolutionary models. This is done by using an optimised method for identifying M

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Zhang, ZengHua. "Discovery and characterisation of ultra-cool dwarfs in large scale surveys." Thesis, University of Hertfordshire, 2013. http://hdl.handle.net/2299/13900.

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Ultracool dwarfs including the lowest mass stars and substellar dwarfs (or brown dwarfs) is a rapidly evolving and very active field. In this thesis I present the discovery and characterization of ultracool dwarfs and their binary systems with solar and subsolar abundances and try to answer a few scientific questions related to these ultracool objects. I use different techniques based on photometric and astrometric data of modern large scale surveys to identify ultracool dwarfs and their binaries. I identify around 1000 ultracool dwarfs from SDSS, 2MASS and UKIDSS surveys, including 82 L dwarf

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35

Shan, Yutong, Jennifer C. Yee, Brendan P. Bowler, et al. "The Multiplicity of M Dwarfs in Young Moving Groups." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/627110.

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We image 104 newly identified low-mass (mostly M-dwarf) pre-main sequence (PMS) members of nearby young moving groups (YMGs) with Magellan Adaptive Optics (MagAO) and identify 27 stellar binaries with instantaneous projected separation as small as 40 mas. Fifteen were previously unknown. The total number of multiple systems in this sample including spectroscopic and visual binaries from the literature is 36, giving a raw stellar multiplicity rate of at least 35(-4)(+5)% for this population. In the separation range of roughly 1-300 au in which infrared AO imaging is most sensitive, the raw mult

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Lindgren, Sara. "Metallicity determination of M dwarfs." Doctoral thesis, Uppsala universitet, Observationell astrofysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-332102.

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M dwarfs constitute around 70% of all stars in the local Galaxy. Their multitude together with their long main-sequence lifetimes make them important for studies of global properties of the Galaxy such as the initial mass function or the structure and kinematics of stellar populations. In addition, the exoplanet community is showing an increasing interest for those small, cold stars. However, very few M dwarfs are well characterized, and in the case of exoplanetary systems the stellar parameters have a direct influence on the derived planet properties. Stellar parameters of M dwarfs are diffic

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Canty, James Ignatius. "Investigating the properties of brown dwarfs using intermediate-resolution spectroscopy." Thesis, University of Hertfordshire, 2015. http://hdl.handle.net/2299/15194.

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This thesis is an investigation into some properties of brown dwarfs using medium-resolution spectroscopy. In the first part of the thesis, I address the issue of parameter degeneracy in brown dwarfs. In the course of my analysis, I derive a gravity-sensitive spectral index which can be used, statistically at least, to differentiate populations of young objects from field dwarfs. The index is also capable of finding the difference between a population of ~1 Myr objects and a population of ~10 Myr objects and may be used to separate low-mass members from foreground and background objects in you

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Goulding, Niall Thomas. "The variability of M dwarfs." Thesis, University of Hertfordshire, 2013. http://hdl.handle.net/2299/13906.

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M dwarfs have been the subject of renewed interest as potential habitable planet hosts and have increasingly become the targets of planet detection surveys. Currently, however, the number of detections of transiting M dwarf planets remain low. The characterisation of M dwarf activity is an important consideration for such surveys, and provides constraints on the modelling of magnetically active low mass stars. Currently the spottedness of M dwarfs is not well understood owing to their intrinsic faintness and the lack of diagnostics for assessing starspot morphologies and distributions. The WFC

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Okeng'o, Geoffrey Onchong’a. "A theoretical study of stellart pulsations in young brown dwarfs." Thesis, University of the Western Cape, 2011. http://hdl.handle.net/11394/2567.

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Magister Scientiae - Msc<br>This thesis reports the results of a twofold study on the recently proposed phenomenon of ‘stellar pulsations’ in young brown dwarfs by the seminal study of Palla and Baraffe (2005) (PB05, thereafter). The PB05 study presents results of a non-adiabatic linear stability analysis showing that young brown dwarfs should become pulsationally unstable during the deuterium burning phase of their evolution.<br>South Africa

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Smith, Leigh Charles. "Near-infrared proper motion surveys." Thesis, University of Hertfordshire, 2016. http://hdl.handle.net/2299/17192.

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I present the development of two near infrared proper motion pipelines for high resolution near infrared data from UKIDSS and the VISTA VVV survey. The UKIDSS pipeline is capable of accuracies of order 5-10 mas yr⁻¹ for bright sources with the largest epoch baselines (~ 8 years). The VVV pipeline reaches 1-2 mas yr⁻¹ proper motion precision at the bright end and parallax measurements at ~ 1 mas precision. It will be possible to improve upon the VVV astrometric precision due to increases in data volume and further pipeline development. I have used the proper motion pipelines to generate three n

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Clanton, Christian Dwain. "The Demographics of Exoplanetary Companions to M Dwarfs: Synthesizing Results from Microlensing, Radial Velocity, and Direct Imaging Surveys." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1459947520.

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42

Whitehurst, R. "Mass flow in binary stars." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379895.

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Burgess, Andrew. "Exploration de la fonction de faible masse initiale dans les amas jeunes et les r ´egions de formation stellaire." Phd thesis, Université de Grenoble, 2010. http://tel.archives-ouvertes.fr/tel-00576460.

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La détermination de l'extrémité inférieure de la fonction de masse initiale (FMI) prévoit de fortes contraintes sur les théories de la formation des étoiles. IC4665 est un amas d'´étoile jeune (30Myr) et il a situe 356pc de la Terre. L'extinction est Av~ 0.59 ± 0.15 mag. WIRCam Y, J, H et K observations ont été faites par le CFHT et a comprise 10 champs (de 1.1sq.deg totale) et deux zones de contrle de 20'x20' chacun. Diagrammes couleur/magnitude et couleur/couleur ont été utilisées pour comparer les candidats sélectionnées par les modèles BT-SETTL 30 et 50Myr. Les images CH4off et CH4on ont é

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Bouy, Herve. "Fundamental Properties of very low mass star and brown dwarf binaries." Diss., lmu, 2004. http://nbn-resolving.de/urn:nbn:de:bvb:19-26541.

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Bouy, Hervé. "Fundamental properties of very low mass star and brown dwarf binaries." Université Joseph Fourier (Grenoble), 2004. http://www.theses.fr/2004GRE10096.

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Ce travail présente les résultats d'une étude détaillée des propriétés statistiques et physiques des binaires de naines brunes et ultra-froides (type spectral plus tardif que M7). Concernant les propriétés statistiques, nous constatons que la fréquence de binaires parmi les objets ultra-froids est inférieure a celle des objets de types spectraux plus precoces, avec une limite inférieure à 10-15% pour les objets du champ, et <10% dans l'amas ouvert des Pleiades. Alors que nous étions capables d'identifier les systèmes binaires jusqu'a des séparations de 100 U. A, nous n'avons trouvé aucun sy

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Pineda, John Sebastian. "Activity and kinematics of low mass stars." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61260.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2010.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 95-96).<br>We present an analysis of the magnetic activity, photometry and kinematics of approximately 70000 M dwarfs from the Sloan digital Sky Survey (SDSS) Data Release 7. This new analysis explores the spatial distribution of these M dwarf properties as a function of vertical distance from the Galactic plane (Z) and distance from the Galactic center (R). We confirm the established trends of decreasing magnetic activity, as measure

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Rainger, Paul P. "Studies of low-mass interacting binary stars." Thesis, University of St Andrews, 1990. http://hdl.handle.net/10023/14369.

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Spectroscopic and photometric observations of eight contact/near-contact binaries are presented and analysed. Spectroscopic observations were obtained at 4200 Å (radial velocity spectra) and 6563 Å (hydrogen-alpha line profiles). New photometric observations were obtained at visual and infrared wavelengths, and other previously published light curves are also re-analysed. Absolute dimensions have been obtained for five systems; TY Boo, VW Boo, BX And, SS Ari and AG Vir, and their evolutionary positions discussed. Four of the systems are found to be in marginal but poor thermal contact, exhib

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Mendes, Luiz Themystokliz Sanctos. "Evolutionary models of rotating low mass stars." Universidade Federal de Minas Gerais, 1999. http://hdl.handle.net/1843/BUOS-9GGP5S.

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We have investigated the combined effects of rotation and internal ngular momentum redistribution on the structure and evolution of low mass tars, from the pre-main sequence to the main sequence phase. As a tool for that study, the ATON stellar evolutionary code (Mazzitelli 1989; Ventura et al. 1998) has been modified in order to include those effects. Rotation as implemented according to the equipotential technique developed by Kippenhahn and Thomas (1970) and later improved by Endal and Sofia (1976). Angular momentum redistribution in radiative regions was modeled through an advection-diffus

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Miles-Páez, Paulo A., Stanimir Metchev, Kevin L. Luhman, Massimo Marengo, and Alan Hulsebus. "The Prototypical Young L/T-Transition Dwarf HD 203030B Likely Has Planetary Mass." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/627091.

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Upon its discovery in 2006, the young L7.5 companion to the solar analog HD 203030 was found to be approximate to 200 K cooler than older late-L dwarfs, which is quite unusual. HD. 203030B offered the first clear indication that the effective temperature at the L-to-T spectral type transition depends on surface gravity: now a well-known characteristic of low-gravity ultra-cool dwarfs. An initial age analysis of the G8V primary star indicated that the system was 130-400 Myr old, and so the companion would be between 12 and 31 M-Jup. Using moderate-resolution near-infrared spectra of HD. 203030B

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Pozzo, Monica. "The effect of high-mass stars on low-mass star formation." Thesis, Keele University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366445.

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