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Letteratura scientifica selezionata sul tema "Brown dwarfs stars"

Autore: Grafiati

Pubblicato: 16 settembre 2023

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Articoli di riviste sul tema "Brown dwarfs stars"

Majidi, Dorsa, John C. Forbes e Abraham Loeb. "Where to Find Overmassive Brown Dwarfs: New Benchmark Systems for Binary Evolution". Astrophysical Journal 932, n. 2 (1 giugno 2022): 91. http://dx.doi.org/10.3847/1538-4357/ac6501.

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Abstract Under the right conditions, brown dwarfs that gain enough mass late in their lives to cross the hydrogen-burning limit will not turn into low-mass stars, but rather remain essentially brown dwarf–like. While these objects, called either beige dwarfs or overmassive brown dwarfs, may exist in principle, it remains unclear exactly how they would form astrophysically. We show that accretion from AGB winds, aided by the wind Roche lobe overflow mechanism, is likely to produce a substantial population of observable overmassive brown dwarfs, though other mechanisms are still plausible. Specifically, we predict that Sun-like stars born with a massive brown dwarf companion on an orbit with a semimajor axis of order 10 au will likely produce overmassive brown dwarfs, which may be found today as companions to the donor star's remnant white dwarf. The identification and characterization of such an object would produce unique constraints on binary evolution, because there is a solid upper limit on the brown dwarf's initial mass.

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Martín, Eduardo L., Mike Connelley, Dan Potter e Hervé Bouy. "Brown Dwarf Companions to Solar-Type Stars and other Brown Dwarfs". Symposium - International Astronomical Union 213 (2004): 111–14. http://dx.doi.org/10.1017/s007418090019309x.

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We report on our ongoing imaging efforts to detect brown dwarfs orbiting solar-type stars and other brown dwarfs. We study the properties of brown dwarf companions as a function of primary mass. Our results indicate that the frequency of brown dwarf companions around solar-type stars for separations larger than about 40 AU is non-negligible. The frequency of brown dwarf binaries is about 20%. There is a dearth of brown dwarf binaries with separations larger than ∼20 AU. We propose that brown dwarf systems are a scaled down version of stellar systems, which probably form via triggered collapse of small molecular cores.

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Gizis, John E. "Wide Brown Dwarf Companions to Main-Sequence Stars". Symposium - International Astronomical Union 211 (2003): 281–86. http://dx.doi.org/10.1017/s0074180900210759.

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Many widely separated companions to main-sequence stars have been found using 2MASS. These companions include both stars and brown dwarfs. I discuss a number of systems of particular interest. Present indications are that a few percent of G dwarfs have brown dwarf companions.

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Liebert, James. "Searches for Brown Dwarfs". International Astronomical Union Colloquium 147 (1994): 463–80. http://dx.doi.org/10.1017/s025292110002649x.

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AbstractThis review attempts a brief summary of the numerous and diverse searches for the so-called brown dwarfs, substellar objects having masses between giant planets and the lowest mass M dwarf stars.

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Bate, Matthew R. "Stellar and brown dwarf properties from numerical simulations". Proceedings of the International Astronomical Union 5, H15 (novembre 2009): 769–70. http://dx.doi.org/10.1017/s174392131001152x.

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AbstractWe review the statistical properties of stars and brown dwarfs obtained from the first hydrodynamical simulation of star cluster formation to produce more than a thousand stars and brown dwarfs while simultaneously resolving the lowest mass brown dwarfs (those with masses set by the opacity limit for fragmentation), binaries with separations down to ~ 1 AU, and discs with radii greater than ~ 10 AU. In particular, we present the eccentricity distribution of the calculation's very-low-mass and brown dwarf binaries which has not been previously published.

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Wolk, Scott J. "X-Ray Detection of Brown Dwarfs with Chandra". Symposium - International Astronomical Union 211 (2003): 447–50. http://dx.doi.org/10.1017/s0074180900211108.

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I review recent observations of brown dwarfs by the Chandra X-ray Observatory. These observations fall in 2 categories, young stellar clusters which contain brown dwarfs and brown dwarf candidates and directed pointings at brown dwarfs and very low mass stars. Surprisingly, there are already over 60 published detections of brown dwarfs by Chandra. A review of the X–ray characteristics shows these objects are subject to flaring and their temperatures and luminosities have a vast range which is related to age.

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Stamatellos, Dimitris, e Anthony Whitworth. "The formation of brown dwarfs in discs: Physics, numerics, and observations". Proceedings of the International Astronomical Union 6, S270 (maggio 2010): 223–26. http://dx.doi.org/10.1017/s174392131100041x.

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AbstractA large fraction of brown dwarfs and low-mass stars may form by gravitational fragmentation of relatively massive (a few 0.1 M⊙) and extended (a few hundred AU) discs around Sun-like stars. We present an ensemble of radiative hydrodynamic simulations that examine the conditions for disc fragmentation. We demonstrate that this model can explain the low-mass IMF, the brown dwarf desert, and the binary properties of low-mass stars and brown dwarfs. Observing discs that are undergoing fragmentation is possible but very improbable, as the process of disc fragmentation is short lived (discs fragment within a few thousand years).

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Persson, Carina M., Szilárd Csizmadia, Alexander J. Mustill, Malcolm Fridlund, Artie P. Hatzes, Grzegorz Nowak, Iskra Georgieva et al. "Greening of the brown-dwarf desert". Astronomy & Astrophysics 628 (agosto 2019): A64. http://dx.doi.org/10.1051/0004-6361/201935505.

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Context. Although more than 2000 brown dwarfs have been detected to date, mainly from direct imaging, their characterisation is difficult due to their faintness and model-dependent results. In the case of transiting brown dwarfs, however, it is possible to make direct high-precision observations. Aims. Our aim is to investigate the nature and formation of brown dwarfs by adding a new well-characterised object, in terms of its mass, radius and bulk density, to the currently small sample of less than 20 transiting brown dwarfs. Methods. One brown dwarf candidate was found by the KESPRINT consortium when searching for exoplanets in the K2 space mission Campaign 16 field. We combined the K2 photometric data with a series of multicolour photometric observations, imaging, and radial velocity measurements to rule out false positive scenarios and to determine the fundamental properties of the system. Results. We report the discovery and characterisation of a transiting brown dwarf in a 5.17-day eccentric orbit around the slightly evolved F7 V star EPIC 212036875. We find a stellar mass of 1.15 ± 0.08 M⊙, a stellar radius of 1.41 ± 0.05 R⊙, and an age of 5.1 ± 0.9 Gyr. The mass and radius of the companion brown dwarf are 51 ± 2 MJ and 0.83 ± 0.03 RJ, respectively, corresponding to a mean density of 108−13+15 g cm−3. Conclusions. EPIC 212036875 b is a rare object that resides in the brown-dwarf desert. In the mass-density diagram for planets, brown dwarfs, and stars, we find that all giant planets and brown dwarfs follow the same trend from ~0.3 MJ to the turn-over to hydrogen burning stars at ~ 73 MJ. EPIC 212036875 b falls close to the theoretical model for mature H/He dominated objects in this diagram as determined by interior structure models. We argue that EPIC 212036875 b formed via gravitational disc instabilities in the outer part of the disc, followed by a quick migration. Orbital tidal circularisation may have started early in its history for a brief period when the brown dwarf’s radius was larger. The lack of spin–orbit synchronisation points to a weak stellar dissipation parameter (Q⋆′ ≳ 108), which implies a circularisation timescale of ≳23 Gyr, or suggests an interaction between the magnetic and tidal forces of the star and the brown dwarf.

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Pearson, Samuel, Aleks Scholz, Paula S. Teixeira, Koraljka Mužić e Víctor Almendros-Abad. "The first spectroscopically confirmed brown dwarfs in NGC 2264". Monthly Notices of the Royal Astronomical Society 507, n. 3 (23 agosto 2021): 4074–85. http://dx.doi.org/10.1093/mnras/stab2394.

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ABSTRACT We present spectroscopic follow-up observations of 68 red, faint candidates from our multi-epoch, multiwavelength, previously published survey of NGC 2264. Using near-infrared spectra from VLT/KMOS, we measure spectral types and extinction for 32 young low-mass sources. We confirm 13 as brown dwarfs in NGC 2264, with spectral types between M6 and M8, corresponding to masses between 0.02 and 0.08 M⊙. These are the first spectroscopically confirmed brown dwarfs in this benchmark cluster. 19 more objects are found to be young M-type stars of NGC 2264 with masses of 0.08–0.3 M⊙. 7 of the confirmed brown dwarfs as well as 15 of the M-stars have IR excess caused by a disc. Comparing with isochrones, the typical age of the confirmed brown dwarfs is <0.5–5 Myr. More than half of the newly identified brown dwarfs and very low-mass stars have ages <0.5 Myr, significantly younger than the bulk of the known cluster population. Based on the success rate of our spectroscopic follow-up, we estimate that NGC 2264 hosts 200–600 brown dwarfs in total (in the given mass range). This would correspond to a star-to-brown dwarf ratio between 2.5:1 and 7.5:1. We determine the slope of the substellar mass function as $\alpha = 0.43^{+0.41}_{-0.56}$; these values are consistent with those measured for other young clusters. This points to a uniform substellar mass function across all star-forming environments.

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Baraffe, I., e F. Allard. "Atmosphere models for very low mass stars, brown dwarfs and exoplanets". Symposium - International Astronomical Union 189 (1997): 227–33. http://dx.doi.org/10.1017/s0074180900116729.

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Over the past decade considerable effort, both observational and theoretical, has been directed towards a more accurate determination of the stellar lower main sequence and of the sub-stellar domain covered by Brown Dwarfs and Planets. Astronomers have been looking for brown dwarfs for more than a decade, either with standard astronomical technics or with microlensing experiments. A breakthrough in the search for brown dwarfs was very recently achieved with the discovery of the first cool brown dwarf GL 229B (Nakajima et al. 1995). At the same epoch, the search for planets blossomed with the discovery of a Jupiter - mass companion of the star 51 Pegasi (Mayor and Queloz 199,5). Now, the number of faint, cool stars and substellar objects is rising rapidly.

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Più fonti

Tesi sul tema "Brown dwarfs stars"

Day-Jones, A. C. "Searching for brown dwarf companions". Thesis, University of Hertfordshire, 2009. http://hdl.handle.net/2299/3475.

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In this thesis I present the search for ultracool dwarf companions to main sequence stars, subgiants and white dwarfs. The ultracool dwarfs identified here are benchmark objects, with known ages and distances. The online data archives, the two micron all sky survey (2MASS) and SuperCOSMOS were searched for ultracool companions to white dwarfs, where one M9 1 companion to a DA white dwarf is spectroscopically confirmed as the widest separated system of its kind known to date. The age of the M9 1 is constrained to a minium age of 1.94Gyrs, based on the estimated age of the white dwarf from a spectroscopically derived Teff and log g and an initial-final mass relation. This search was extended using the next generation surveys, the sloan digital sky survey (SDSS) and the UK infrared deep sky survey (UKIDSS), where potential white dwarf + ultracool dwarf binary systems from this search are presented. A handful of these candidate systems were followed-up with second epoch near infrared (NIR) imaging. A new white dwarf with a spectroscopic M4 companion and a possible wide tertiary ultracool component is here confirmed. Also undertaken was a pilot imaging survey in the NIR, to search for ultracool companions to subgiants in the southern hemisphere using the Anglo-Australian telescope. The candidates from that search, as well as the subsequent follow-up of systems through second epoch NIR/optical imaging and methane imaging are presented. No systems are confirmed from the current data but a number of good candidates remain to be followed-up and look encouraging. A search for widely separated ultracool objects selected from 2MASS as companions to Hipparcos main-sequence stars was also undertaken. 16 candidate systems were revealed, five of which had been previously identified and two new L0 2 companions are here confirmed, as companions to the F5V spectroscopic system HD120005 and the M dwarf GD 605. The properties of HD120005C were calculated using the DUSTY and COND models from the Lyon group, and the age of the systems were inferred from the primary members. For GD 605B no age constraint could be placed due to the lack of information available about the primary, but HD120005C has an estimated age of 2-4Gyr. In the final part of this thesis I investigate correlations with NIR broadband colours (J - H, H - K and J - K) with respect to properties, Teff , log g and [Fe/H] for the benchmark ultracool dwarfs, both confirmed from the searches undertaken in this work and those available from the literature. This resulted in an observed correlation with NIR colour and Teff, which is presented here. I find no correlation however with NIR colours and log g or [Fe/H], due in part to a lack of suitable benchmarks. I show that despite the current lack of good benchmark objects, this work has the potential to allow UCD properties to be measured from observable characteristics, and suggest that expanding this study should reveal many more benchmarks where true correlation between properties and observables can be better investigated.

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Samaddar, Debasmita. "Photometric variability of three brown dwarfs". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 2.24 Mb., 65 p, 2006. http://proquest.umi.com/pqdlink?did=1075713471&Fmt=7&clientId=8331&RQT=309&VName=PQD.

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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 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. 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.
Ph.D.
Department of Physics
Sciences
Physics PhD

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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. Modern CCD technology has led to larger and larger area cluster surveys and so chapter 3 reviews this technology and the data reduction software and techniques necessary for analysis. Chapters 4, 5, 6 and 7 present the observational results. Chapter 4 presents an essentially null result of a deep HST survey in the Pleiades. Chapter 5 presents the d ata used to calibrate the I--Z colour and chapter 6 describes the discovery of PIZ 1, a brown dwarf in the Pleiades of mass 0.048 M⊙ and effective temperature ~2200K. Chapter 7 presents the infrared follow-up results of a number of recent large area optical surveys. Chapters 8 and 9 use the results from the latest surveys to determine the mass and luminosity functions of both Praesepe and the Pleiades. In Praesepe the mass function is calculated down to the brown dwarf limit in the cluster and shows no sign of turning down. In the Pleiades the mass function appears to be flattening across the stellar sub-stellar boundary. Finally in Chapter 10 I summarise the important conclusions from each chapter and identify areas of future work.

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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 aims and thesis structure. The second chapter gives a review of the current theoretical and observational status of the field, and the third chapter describes the principles and methods used to carry out the photometry presented in this thesis. The results are presented in chapters (4), (5), (6) and (7). An RIZ survey of Praesepe produces a sample of 26 candidate VLM and BDs. K band photometric follow up of 11 of these highlights one as a binary system that almost certainly contains at least one brown dwarf. K photometry is still needed for the remaining 15. The RIZ survey also finds a possible steepening of Praesepe's mass function into the BD regime. The Praesepe infrared sequence compares very well with the latest non gray model predictions, and the binary fraction in Praesepe is found to be essentially the same as for The Pleiades. A catalogue of Pleiades stars is used to model the cluster. King profiles are plotted for 4 mass bins and these profiles suggest that the cluster is relaxed. Virial analysis is then used to show that the cluster contains not more than 131M of dark matter (BDs) to add to the observed mass of 735M. Further deep surveys in The Pleiades, Praesepe and the Hyades result in 88 new Pleiades BD candidates, 141 Praesepe VLM candidates and 33 Hyades BD candidates. These new candidate lists, as well as finder charts are given in the appendices.

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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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Manjavacas, E., P. A. Miles-Paez, M. R. Zapatero-Osorio, B. Goldman, E. Buenzli, T. Henning, E. Palle e M. Fang. "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 telescope in Calar Alto Observatory (Spain). The flux ratio method was employed to determine the linear polarization degrees. With a confidence of 3 sigma, our data indicate that all targets have a linear polarimetry degree in average below 0.69 per cent in the I band, and below 1.0 per cent in the R band, at the time they were observed. We detected significant (i.e. P/sigma >= 3) linear polarization for the young M6 dwarf 2MASS J04221413+1530525 in the R band, with a degree of p* = 0.81 +/- 0.17 per cent.

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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 inconsistent with observations, there have been few conclusive tests to date. I will present high angular resolution optical, near-infrared, and thermal-infrared imaging and medium-resolution (up to R~5000) spectroscopy of these two T dwarfs. Using these data I have derived luminosities of log L/Lsun = -4.699 +/- 0.017 and -5.232 +/- 0.020 for Epsilon Indi Ba, Bb, respectively, and I will show that the predictions of substellar evolutionary models using luminosity and mass constraints are inconsistent with the effective temperatures and surface gravities derived from fitting atmospheric models to observed spectra. Furthermore, I will show that, even where estimates of the effective temperature, surface gravity, and luminosity are available, estimates of the mass of cool brown dwarfs can be up to a factor of two lower than the measured dynamical mass. Considering the difficulty in assigning accurate ages to any system and the mass-luminosity-age degeneracy of brown dwarfs, I would caution against the over-analysis of predicted brown dwarf masses at this time. I have also used Chandra X-ray observations to identify near-complete and relatively unbiased samples of pre-main-sequence stars in the young stellar clusters NGC 2244 and Trumpler 14. Using optical photometric and spectroscopic observations, I will characterise the apparent age spreads seen in the cluster pre-main-sequences. Mass estimates will then be derived for their stellar populations and used to construct the initial mass function for each cluster. It is found that NGC 2244 appears to have a Salpeter-like IMF for stars in the mass range 0.5--2.0 Msun if a likely age of 2 Myr is adopted, while Tr 14 may have a top-heavy IMF at a similar age. However, I will show that because the observed slopes of the cluster pre-main-sequences are not well-matched by the predicted slope in colour-magnitude space, such determinations are heavily dependent on the assumed age of the cluster and complicated due to the large spreads in isochronal ages.

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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 observations of brown dwarfs. The results are presented in chapters four, five and six. RIJHK photometry for a sample of 62 objects is presented. The 1,1 - K diagram is shown to be a good discriminant of binary status for low mass cluster objects and using this diagram two single brown dwarf candidates and seven potential brown dwarf containing binaries are identified. FOS optical spectroscopy of 31 objects is used in an investigation of temperature indicators for cool stars. In addition gravity sensitive features indicate that the surface gravity of the Pleiades objects is lower than equivalent main sequence objects. Also discussed are the chromospheric and coronal activity of cluster members, and evidence is presented showing a turnover in both at ~ 0.3M⊕, where the objects become fully convective. CGS4 1-2.5 micron spectra are used in a futher investigation of methods of determining effective temperature and in searching for evidence of low mass companions. One object shows evidence for a low mass companion of ~ 0.035M⊕. Chapter seven discusses the evidence from these results that the faintest members observed are brown dwarfs and evidence from other workers that they are not. This chapter also gives suggestions for future work. Appendices compile the theoretical models and data used in the project.

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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 indicate the presence of significant numbers of very low mass stars and possible brown dwarfs with the distinct possibility of discovering more in the near future; two techniques for extracting Pleiades member stars from the field (star counts and proper motions) are described and the cluster luminosity function is found to be strikingly similar in shape to that found for the field stars near the sun. A list of probable Pleiades members, the faintest of which may be brown dwarfs, is presented in the appendix. The derived mass function, although uncertain, indicates that brown dwarfs are present in the cluster. The preliminary analysis of the field around the Carinae cluster highlights the problems of crowded field astronomy using these techniques. Although this cluster does not appear to be as rich as the Pleiades, the results obtained so far indicate possible very low mass main sequence membership that could be investigated further with more plate material. Finally, these and other results are discussed in chapter six and suggestions for further work are presented. Appendices at the end compile data on the least luminous objects known, present photoelectric calibration sequences for the plate material and reproduce reprints of two papers derived from this work.

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Più fonti

Libri sul tema "Brown dwarfs stars"

R, Rebolo, Zapatero Osorio Maria Rosa e "Three-Islands" Euroconference on "Stellar Clusters and Associations" (1st : 1998 : Palma, Canary Islands), a cura di. Very low-mass stars and brown dwarfs. Cambridge: Cambridge University Press, 2000.

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Reid, I. Neill. New light on dark stars: Red dwarfs, low-mass stars, brown dwarfs. New York: Springer, 2000.

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Black, David C. Possible observational criteria for distinguishing brown dwarfs from planets. [Washington, DC: National Aeronautics and Space Administration, 1997.

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United States. National Aeronautics and Space Administration., a cura di. Possible observational criteria for distinguishing brown dwarfs from planets. [Washington, DC: National Aeronautics and Space Administration, 1997.

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1945-, Kafatos Menas, Harrington Robert S e Maran Stephen P, a cura di. Astrophysics of brown dwarfs: Proceedings of a workshop held at George Mason University, Fairfax, Virginia, October 14-15, 1985. Cambridge: Cambridge University Press, 1986.

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L, Martin Eduardo, a cura di. Brown dwarfs: Proceedings of the 211th Symposium of the International Astronomical Union held at the Outrigger Waikoloa Beach Hotel, Waikoloa, Hawaii̓, USA, 20-24 May 2002. San Francisco, Calif: Published on behalf of IAU by the Astronomical Society of the Pacific, 2003.

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R, Rebolo, Martin Eduardo L e Zapatero Osorio Maria Rosa, a cura di. Brown dwarfs and extrasolar planets: Proceedings of a workshop held in Puerto de la Cruz, Tenerife, Spain, 17-21 March 1997. San Francisco, Calif: Astronomical Society of the Pacific, 1998.

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A, Griffith Caitlin, e Marley Mark S. 1962-, a cura di. From giant planets to cool stars: Proceedings of a workshop held at Northern Arizona University, Flagstaff, Arizona, USA, 8-11 June 1999. San Francisco, Calif: Astronomical Society of the Pacific, 2000.

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Howell, Steve B. On the existence of low-luminosity cataclysmic variables beyond the orbital period minimum. [Washington, DC: National Aeronautics and Space Administration, 1997.

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Howell, Steve B. On the existence of low-luminosity cataclysmic variables beyond the orbital period minimum. [Washington, DC: National Aeronautics and Space Administration, 1997.

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Capitoli di libri sul tema "Brown dwarfs stars"

Reid, I. Neill. "Brown Dwarfs". In Planets, Stars and Stellar Systems, 337–95. Dordrecht: Springer Netherlands, 2013. http://dx.doi.org/10.1007/978-94-007-5615-1_7.

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Reid, I. Neill, e Suzanne L. Hawley. "Brown dwarfs". In New Light on Dark Stars, 341–89. London: Springer London, 2000. http://dx.doi.org/10.1007/978-1-4471-3663-7_9.

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Nelson, Lorne A. "Low-Mass Stars and Brown Dwarfs". In Baryonic Dark Matter, 67–85. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-0565-8_4.

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Reipurth, Bo. "The Formation of Brown Dwarfs". In The Origin of Stars and Planets: The VLT View, 114–20. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/10856518_14.

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Reipurth, Bo. "The Formation of Brown Dwarfs". In The Origins of Stars and Planets: The VLT View, 114–19. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/978-3-662-40277-1_14.

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Oppenheimer, Ben R. "Companions of Stars: From Other Stars to Brown Dwarfs to Planets and the Discovery of the First Methane Brown Dwarf". In 50 Years of Brown Dwarfs, 81–111. Cham: Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-319-01162-2_6.

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Rebolo, Rafael. "From Cores to Stars, Brown Dwarfs and Planets". In Magnetic Fields and Star Formation, 207–9. Dordrecht: Springer Netherlands, 2004. http://dx.doi.org/10.1007/978-94-017-0491-5_21.

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Bate, Matthew R. "From Molecular Cores to Stars and Brown Dwarfs". In Magnetic Fields and Star Formation, 211–21. Dordrecht: Springer Netherlands, 2004. http://dx.doi.org/10.1007/978-94-017-0491-5_22.

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Joergens, Viki, Eike Guenther, Ralph Neuhäuser, Fernando Comerón, Nuria Huélamo, João Alves e Wolfgang Brandner. "Multiplicity of Young Brown Dwarfs in Cha I". In The Origins of Stars and Planets: The VLT View, 127–32. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/978-3-662-40277-1_16.

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Stamatellos, Dimitris. "The Formation of Low-Mass Stars and Brown Dwarfs". In The Labyrinth of Star Formation, 17–24. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-03041-8_3.

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Atti di convegni sul tema "Brown dwarfs stars"

Mokler, Felicitas, Christiane Helling, Moira Jardine e Eric Stempels. "Lightning In Brown Dwarfs?" In COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP, 2009. http://dx.doi.org/10.1063/1.3099166.

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Lin, Douglas N. C. "Formation of low mass stars and brown dwarfs". In The seventh astrophysical conference: Star formation, near and far. AIP, 1997. http://dx.doi.org/10.1063/1.52786.

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Reylé, C., P. Delorme, X. Delfosse, T. Forveille, C. Willott, L. Albert, E. Artigau e Eric Stempels. "The ultracool field dwarfs luminosity function from the Canada-France Brown Dwarf Survey". In COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP, 2009. http://dx.doi.org/10.1063/1.3099171.

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Liu, Michael C., Keivan G. Stassun, France Allard, Cullen H. Blake, M. Bonnefoy, Ann Marie Cody, A. C. Day-Jones et al. "Fundamental Properties of Low-Mass Stars and Brown Dwarfs". In COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP, 2009. http://dx.doi.org/10.1063/1.3099100.

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Herczeg, Gregory J., Kelle Cruz, Lynne A. Hillenbrand e Eric Stempels. "Measuring tiny mass accretion rates onto young brown dwarfs". In COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP, 2009. http://dx.doi.org/10.1063/1.3099165.

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Hallinan, Gregg, Gerry Doyle, Antoaneta Antonova, Stephen Bourke, Moira Jardine, J. F. Donati, Julien Morin, Aaron Golden e Eric Stempels. "Mapping the Radio Coronae of Cool Stars and Brown Dwarfs". In COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP, 2009. http://dx.doi.org/10.1063/1.3099085.

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Ryan, P. T., J. R. P. Angel, D. W. McCarthy, L. M. Close, S. Mohanty, R. Fugate e D. G. Sandler. "Halo Properties and Their Influence on Companion Searches at the Starfire Optical Range". In Adaptive Optics. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/adop.1996.atub.3.

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Abstract (sommario):

One of the questions which has endured for as long as man has looked at the heavens is ”Are we alone?”. Are there beings on other planets who are also looking into the heavens? The first requirement for alien life similar to our own is that there be planets orbiting other stars. The early stages of planet formation as dictated by theory appear to be robust and several large planets have recently been detected by indirect means[1][2]. Direct imaging is currently being used to search for less ambitious, yet still scientifically interesting faint objects called Brown Dwarfs. The most convincing evidence of a Brown Dwarf, a cross between a star and a planet, was discovered by direct imaging with the aid of a 7.7 arcsecond separation from a companion star[3].

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Freytag, Bernd, France Allard, Hans-Günter Ludwig, Derek Homeier, Matthias Steffen, Christopher Sharp e Eric Stempels. "Convective mixing and dust clouds in the atmospheres of brown dwarfs". In COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP, 2009. http://dx.doi.org/10.1063/1.3099155.

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Geiβler, K., M. R. Sterzik, G. Chauvin, E. Pantin e Eric Stempels. "Mid-infrared imaging of brown dwarfs: Is HD 130948 BC variable?" In COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP, 2009. http://dx.doi.org/10.1063/1.3099163.

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Nakano, Takenori. "Prof. Hayashi’s work on the pre-main sequence evolution and brown dwarfs". In FIRST STARS IV – FROM HAYASHI TO THE FUTURE –. AIP, 2012. http://dx.doi.org/10.1063/1.4754322.

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