相关论文: Brown Dwarfs as Galactic Chronometers
White dwarfs can be used as galactic chronometers and, therefore, provide important information about galactic evolution if good theoretical models of their cooling are available. Consequently, it is natural to wonder if all the sources or…
In recent years brown dwarfs have been extended to a new Y-dwarf class with effective temperatures colder than 500K and masses in the range 5-30 Jupiter masses. They fill a crucial gap in observable atmospheric properties between the much…
We have been using Keck laser guide star adaptive optics to monitor the orbits of ultracool binaries, providing dynamical masses at lower luminosities and temperatures than previously available and enabling strong tests of theoretical…
The spectra of brown dwarfs are key to exploring the chemistry and physics that take place in their atmospheres. Late-T dwarf spectra are particularly diagnostic due to their relatively cloud-free atmospheres and deep molecular bands. With…
After a discussion of the physical processes in brown dwarfs, we present a complete, precise definition of brown dwarfs and of planets inspired by the internal physics of objects between 0.1 and 0.001 M_sun. We discuss observational…
As the oldest building blocks of our Galaxy, globular clusters retain the archaeological footprint of the early stellar environments. Accurate absolute ages of globular clusters are required to interpret this ancient record. Existing dating…
White dwarfs are almost completely degenerate objects that cannot obtain energy from the thermonuclear sources and their evolution is just a gravothermal process of cooling. The simplicity of these objects, the fact that the physical inputs…
Age is a fundamental stellar property, yet for many stars it is difficult to reliably determine. For M dwarfs it has been notoriously so. Due to their lower masses, core hydrogen fusion proceeds at a much slower rate in M dwarfs than it…
A number of so-called ultra-cool white dwarfs have been detected in different surveys so far. However, based on anecdotal evidence it is believed that most or all of these ultra-cool white dwarfs are low-mass products of binary evolution…
Three brown dwarfs in different evolutionary stages have been observed with the Chandra X-ray Observatory. Combining the new observations with previous studies presented in the literature yields a brown dwarf sample that reaches well down…
A new method is presented to compute age estimates from theoretical isochrones using temperature, luminosity and metallicity data for individual stars. Based on Bayesian probability theory, this method avoids the systematic biases affecting…
Due to magnitude limits, the Gaia survey will not delve as deeply into the local population of brown dwarfs as it will other stellar populations. While hundreds or thousands of brown dwarfs will be measured by Gaia, we propose a different,…
Brown dwarfs are commonly regarded as easily-observed templates for exoplanet studies, with comparable masses, physical sizes and atmospheric properties. There is indeed considerable overlap in the photospheric temperatures of the coldest…
We calculate the expected white dwarf luminosity functions and discovery functions in photometric passbands, if these stellar remnants provide a substantial fraction of the sought Galactic dark matter, as suggested on various observational…
In order to understand the atmospheres as well as the formation mechanism of giant planets formed outside our solar system, the next decade will require an investment in studies of isolated young brown dwarfs. In this white paper we…
We present an update of our on-going effort to improve the precision of white dwarf cosmochronology via careful analyses of white dwarf photometry in open clusters. To improve the precision of white dwarf and main sequence age analysis, we…
Given the importance of white dwarfs (WDs) in many fields of modern astrophysics, the precise knowledge of the actual degree of accuracy of the associated theoretical predictions is a primary task. In the first paper of a series dedicated…
We present the full results of our decade-long astrometric monitoring programs targeting 31 ultracool binaries with component spectral types M7-T5. Joint analysis of resolved imaging from Keck Observatory and Hubble Space Telescope and…
The white dwarf luminosity function of a stellar cluster will have a sharp truncation at a luminosity which is determined by the time since formation of the first white dwarfs in that cluster. Calculation of the dependence of this limiting…
Precise measurements of the fundamental properties of low-mass stars and brown dwarfs are key to understanding the physics underlying their formation and evolution. While there has been great progress over the last decade in studying the…