Download or read book The Formation of Brown Dwarfs as Revealed by the Mass Function of IC 2391 written by Steve Boudreault and published by . This book was released on 2008 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book New Light on Dark Stars written by Neill I. Reid and published by Springer Science & Business Media. This book was released on 2013-11-27 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: Perhaps the most common question that a child asks when he or she sees the night sky from a dark site for the first time is: 'How many stars are there?' This happens to be a question which has exercised the intellectual skills of many astronomers over the course of most of the last century, including, for the last two decades, one of the authors of this text. Until recently, the most accurate answer was 'We are not certain, but there is a good chance that almost all of them are M dwarfs. ' Within the last three years, results from new sky-surveys - particularly the first deep surveys at near infrared wavelengths - have provided a breakthrough in this subject, solidifying our census of the lowest-mass stars and identifying large numbers of the hitherto almost mythical substellar-mass brown dwarfs. These extremely low-luminosity objects are the central subjects of this book, and the subtitle should be interpreted accordingly. The expression 'low-mass stars' carries a wide range of meanings in the astronomical literature, but is most frequently taken to refer to objects with masses comparable with that of the Sun - F and G dwarfs, and their red giant descendants. While this definition is eminently reasonable for the average extragalactic astronomer, our discussion centres on M dwarfs, with masses of no more than 60% that of the Sun, and extends to 'failed stars' - objects with insufficient mass to ignite central hydrogen fusion.
Download or read book Very Low Mass Stars and Brown Dwarfs written by Rafael Rebolo and published by Cambridge University Press. This book was released on 2000-11-27 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume provides a state-of-the-art review of our current knowledge of brown dwarfs and very low-mass stars. The hunt for and study of these elusive objects is currently one of the most dynamic areas of research in astronomy for two reasons. Brown dwarfs bridge the gap between stars and planets, and they may constitute an important part of the 'dark matter' of the Universe. This volume presents review articles from a team of international authorities who gathered at a conference in La Palma to assess the spectacular progress that has been made in this field in the last few years.
Download or read book 50 Years of Brown Dwarfs written by Viki Joergens and published by Springer Science & Business Media. This book was released on 2013-11-27 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: The years 2012/2013 mark the 50th anniversary of the theoretical prediction that Brown Dwarfs, i.e. degenerate objects which are just not massive enough to sustain stable hydrogen fusion, exist. Some 20 years after their discovery, how Brown Dwarfs form is still one of the main open questions in the theory of star formation. In this volume, the pioneers of Brown Dwarf research review the history of the theoretical prediction and the subsequent discovery of Brown Dwarfs. After an introduction, written by Viki Joergens, reviewing Shiv Kumar's theoretical prediction of the existence of brown dwarfs, Takenori Nakano reviews his and Hayashi's calculation of the Hydrogen Burning Minimum Mass. Both predictions happened in the early 1960s. Jill Tarter then writes on the introduction of the term 'Brown Dwarf', before Ben Oppenheimer, Rafael Rebolo and Gibor Basri describe their first discovery of Brown Dwarfs in the 1990s. Lastly, Michael Cushing and Isabelle Baraffe describe the development of the field to the current state of the art. While the book is mainly aimed at the Brown Dwarf research community, the description of the pioneering period in a scientific field will attract general readers interested in astronomy as well.
Download or read book Literature 1991 Part 2 written by Astronomisches Rechen-Institut and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 1592 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Astronomy and Astrophysics Abstracts" appearing twice a year has become oneof the fundamental publications in the fields of astronomy, astrophysics andneighbouring sciences. It is the most important English-language abstracting journal in the mentioned branches. The abstrats are classified under more than a hundred subject categories, thus permitting a quick survey of the whole extended material. The AAA is a valuable and important publication for all students and scientists working in the fields of astronomy and related sciences. As such it represents a necessary ingredient of any astronomical library all over the world.
Download or read book New Light on Dark Stars written by Neil Reid and published by Springer. This book was released on 2009-09-02 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt: There has been very considerable progress in research into low-mass stars, brown dwarfs and extrasolar planets during the past few years, particularly since the fist edtion of this book was published in 2000. In this new edtion the authors present a comprehensive review of both the astrophysical nature of individual red dwarf and brown dwarf stars and their collective statistical properties as an important Galactic stellar population. Chapters dealing with the observational properies of low-mass dwarfs, the stellar mass function and extrasolar planets have been completely revised. Other chapters have been significantly revised and updated as appropriate, including important new material on observational techniques, stellar acivity, the Galactic halo and field star surveys. The authors detail the many discoveries of new brown dwarfs and extrasolar planets made since publication of the first edition of the book and provide a state-of-the-art review of our current knowledge of very low-mass stars, brown dwarfs and extrasolar planets, including both the latest observational results and theoretical work.
Download or read book Search Characterization and Properties of Brown Dwarfs written by Ramarao Tata and published by . This book was released on 2009 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 objects are intermediate in mass between stars and planets. Since their observational discovery these objects have been studied thoroughly and holistically. Various methods for searching and characterizing these objects in different regions of the sky have been put forward and tested with great success. Theoretical models describing their physical, atmospheric and chemical processes and properties have been proposed and have been validated with a large number of observational results. The work presented in this dissertation is a compilation of synoptic studies of ultracool dwarfs(UDs)1. [Footnote 1:]. [bullet] A search for wide binaries around solar type stars in upper scorpio OB association(Upper Sco) do indicate (the survey is not yet complete) a deficit of BD binaries at these large separations ([less than] 5AU). [bullet] Twenty six new UDs were discovered at low galactic latitudes in our survey from archival data and a novel technique using reduced proper motion. [bullet] Six field UDs were discovered by spectroscopic follow-up of the candidates selected from a deep survey. [bullet] Optical interferometry was used to independently determine the orbit of the companion of HD33636 which was initially determined using Hubble Space Telescope(HST)astrometry and radial velocity found. Some inconsistency in the HST determined orbit and mass. [bullet] Optical linear polarization in UDs was used to investigate the dust propertied in their atmospheres. 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. Footnote 1: We use the term "ultracool dwarfs" as the mass of most of the objects mentioned is unknown, which is required to classify an object as a brown dwarf. We define objects later than M7 as ultra cool dwarfs.
Download or read book Brown Dwarfs and UKIDSS written by David Edwin Alexander Baker and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis I present the work of two studies into the population of low-mass stars and brown dwarfs within the open galactic clusters of Praesepe and Blanco 1 using optical and infrared photometry. Observing these objects within clusters is of great importance as their known ages and distances allow for comparisons to be made between the observed results and those predicted from theoretical formation and evolutionary models, whilst expanding our understanding of the initial mass function. Following an introduction to the formation, evolution and observational history of brown dwarfs in Chapter 2 an overview of the principle data reduction processes and instruments used in this thesis is given in Chapter 3. Chapter 4 presents the result of the survey carried out in Praesepe using archival 2MASS, SDSS and UKIDSS data in a range of filters. Proper motion information is combined with colour magnitude cuts to select out and classify objects that are considered to be cluster members. Over 280 members have been identified with a cluster mass function that is consistent with the values presented for other clusters found. This mass function is in disagreement with previous values found for Praesepe. Chapter 5 presents the results of a follow up J band survey using WFCAM to theCFHT12k I and z survey of Moraux et al. (2007). The data reduction and membership selection procedure are discussed with 27 low-mass objects found to be members. Chapter 6 in contrast to the previous chapters presents a study not of brown dwarfs but of a suspected main-sequence, magnetic white-dwarf binary system found during an archival search of the UKIDSS DR3 database for objects with unusual Y band colours. The evidence for this system being a Polar is presented along with a discussion as to the assumed system properties. Follow up observations using the IAC-80 telescope, UKIRT and the SWIFT satellite are also presented. Finally in Chapter 7 I summarise the results from each chapter and identify areas of future work.
Download or read book The Theory of the Formation of Brown Dwarfs written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We investigate the dynamical decay of non-hierarchical accreting triple systems and its implications on the ejection model as Brown Dwarf formation scenario. A modified chain-regularization scheme is used to integrate the equations of motion, that also allows for mass changes over time as well as for momentum transfer from the accreted gas mass onto the bodies. We integrate an ensemble of triple systems within a certain volume with different accretion rates, assuming several prescriptions of how momentum is transferred onto the bodies. We follow their evolution until the systems have decayed. We find that the formation probability of Brown Dwarfs depends strongly on the assumed momentum transfer which is related to the motion of the gas. Due to ongoing accretion and consequent shrinkage of the systems, the median escape velocity is increased by a factor of 2 and the binary separations are decreased by a factor of 5 compared with non-accreting systems. Furthermore, the obtained semi-major axis distribution drops off sharply to either side of the median, which is also supported by observations. However, the disks around the ejected Brown Dwarfs seem to have too low accretion rates and masses to account for many of the observed disks in typical low-mass star-forming regions. We conclude that accretion of gas and the kinematic properties of the accreted gas during dynamical interactions strongly influence the abundance as well as the dynamical properties of Brown Dwarfs and, that the ejection scenario seems to be a promising scenario to produce both, very close Brown Dwarf binaries as well as single Brown Dwarfs, whereas it seems less likely to find very long-lived accretion disks around them.
Download or read book Brown Dwarfs and Extrasolar Planets written by R. Rebolo and published by . This book was released on 1998 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of a March 1997 workshop, with theoretical and observational papers in sections on free floating brown dwarfs, substellar objects as companions to stars, atmospheres and interiors, and the mass function. Subjects include rotation of field M dwarfs, the formation of eccentric superplanets, extrasolar comets in young stellar systems, extrasolar giant planets, spectroscopic properties of ultra-cool dwarfs and brown dwarfs, the stellar mass function, and the mass of the Pleiades. Annotation copyrighted by Book News, Inc., Portland, OR
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2005 with total page 842 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Observational Properties of Brown Dwarfs written by Catia Vanessa Varejao Cardoso and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigating Low mass Binary Stars and Brown Dwarfs with Near infrared Spectroscopy written by Gregory Nathan Mace and published by . This book was released on 2014 with total page 323 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mass of a star at formation determines its subsequent evolution and demise. Low-mass stars are the most common products of star formation and their long main-sequence lifetimes cause them to accumulate over time. Star formation also produces many substellar-mass objects known as brown dwarfs, which emerge from their natal molecular clouds and continually cool as they age, pervading the Milky Way. Low-mass stars and brown dwarfs exhibit a wide range of physical characteristics and their abundance make them ideal subjects for testing formation and evolution models. I have examined a pair of pre-main sequence spectroscopic binaries and used radial velocity variations to determine orbital solutions and mass ratios. Additionally, I have employed synthetic spectra to estimate their effective temperatures and place them on theoretical Hertzsprung-Russell diagrams. From this analysis I discuss the formation and evolution of young binary systems and place bounds on absolute masses and radii. I have also studied the late-type T dwarfs revealed by the Wide-field Infrared Survey Explorer (WISE). This includes the exemplar T8 subdwarf Wolf 1130C, which has the lowest inferred metallicity in the literature and spectroscopic traits consistent with old age. Comparison to synthetic spectra implies that the dispersion in near-infrared colors of late-type T dwarfs is a result of age and/or thin sulfide clouds. With the updated census of the L, T, and Y dwarfs we can now study specific brown dwarf subpopulations. Finally, I present a number of future studies that would develop our understanding of the physical qualities of T dwarf color outliers and disentangle the tracers of age and atmospheric properties.
Download or read book Literature 1992 Part 1 written by Astronomisches Recheninstitut and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 1456 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Astronomy and Astrophysics Abstracts" appearing twice a year has become oneof the fundamental publications in the fields of astronomy, astrophysics andneighbouring sciences. It is the most important English-language abstracting journal in the mentioned branches. The abstracts are classified under more than a hundred subject categories, thus permitting a quick survey of the whole extended material. The AAA is a valuable and important publication for all students and scientists working in the fields of astronomy and related sciences. As such it represents a necessary ingredient of any astronomical library all over the world.
Download or read book Handbook of Exoplanets written by Hans J. Deeg and published by Springer. This book was released on 2018-06-15 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This state-of-the-art reference work includes over 15 sections dealing with all aspects of exoplanets and exobiology research, including historic aspects, the Solar System as a template, objects at the planet-to-star transition, exoplanet detection and characterization with related instrumentation, technology and software tools, planet and planet-system statistics with recent and planned surveys, their atmosphere and formation and evolution processes, habitability and exobiology implications, and outlooks for future exploration and science development, including visionary contributions. Each section has 10-20 contributions written by the top experts in their subject, including both senior researchers as well as young, smart researchers who represent the future of the discipline. All in all, this handbook comprehensively tackles one of the most challenging and dynamic fields of modern astronomy and astrophysics.
Download or read book Referativny zhurnal written by and published by . This book was released on 1998 with total page 604 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Sun in Time written by Charles Philip Sonett and published by University of Arizona Press. This book was released on 1991 with total page 1040 pages. Available in PDF, EPUB and Kindle. Book excerpt: An interdisciplinary approach to solar physics, as eighty-nine contributors trace the evolution of the Sun and provide a review of our current understanding of both its structure and its role in the origin and evolution of the solar system.
