相关论文: An accurate mass and radius measurement for an ult…

We present parallax observations and a detailed model atmosphere analysis of 54 cool and ultracool ($T_{\rm eff}$ < 4000 K) white dwarfs (WDs) in the solar neighbourhood. For the first time, a large number of cool and ultracool WDs have…

We report on Keck and {\em Hubble Space Telescope} observations of the binary millisecond pulsar PSR B1855+09. We detect its white-dwarf companion and measure $\mv=25.90\pm0.12$ and $\mi=24.19\pm0.11$ (Vega system). From the…

Observational tests of stellar and Galactic chemical evolution call for the joint knowledge of a star's physical parameters, detailed element abundances, and precise age. For cool main-sequence (MS) stars the abundances of many elements can…

We present high precision, model independent, mass and radius measurements for 16 white dwarfs in detached eclipsing binaries and combine these with previously published data to test the theoretical white dwarf mass-radius relationship. We…

Ultra-cool white dwarfs are among the oldest stellar remnants in the Universe. Their efficient gravitational settling and low effective temperatures are responsible for the smooth spectra they exhibit. For that reason, it is not possible to…

Deriving precise stellar ages is a challenging task. Consequently, age-dependent relations - such as the age-metallicity and age-velocity dispersion relations of the Milky Way, or the age-rotation-activity relation of low-mass stars - are…

We use 156 044 white dwarf candidates with $\geq5\sigma$ significant parallax measurements from the Gaia mission to measure the velocity dispersion of the Galactic disc; $(\sigma_U,\sigma_V,\sigma_W) = (30.8, 23.9, 20.0)$ km s$^{-1}$. We…

White dwarf (WD) stars evolve simply and predictably, making them reliable age indicators. However, self-consistent validation of the methods for determining WD total ages has yet to be widely performed. This work uses 1565 wide ( > 100 au)…

We carried out a spectroscopic investigation of single lined white dwarfs (WDs) in double degenerate (DD) systems and discuss their binary evolution. Simulated spectra of the Halpha region are used to derive upper limits on the temperature…

We present a grid of evolutionary tracks for low-mass white dwarfs with helium cores in the mass range from 0.179 to 0.414 M_sun. The lower mass limit is well suited for comparison with white dwarf companions of millisecond pulsars (MSP).…

We present detailed evolutionary calculations for carbon - oxygen - and helium - core white dwarf (WD) models with masses ranging from M= 0.1 to M= 1.2 solar masses and for metallicities Z= 0.001 and Z= 0. The sequences cover a wide range…

Cooling ages of white dwarfs are routinely determined by mapping effective temperatures and masses to ages using evolutionary models. Typically, the reported uncertainties on cooling ages only consider the error propagation of the…

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…

Astrometric observations of resolved binaries provide estimates of orbital periods and will eventually lead to measurement of dynamical masses. Only a few very low mass star and brown dwarf masses have been measured to date, and the…

We present the initial-final mass relation derived from 10 white dwarfs in wide binaries that consist of a main sequence star and a white dwarf. The temperature and gravity of each white dwarf was measured by fitting theoretical model…

Cool subdwarfs are metal-poor low-mass stars that formed during the early stages of the evolution of our Galaxy. Because they are relatively rare in the vicinity of the Sun, we know of few cool subdwarfs in the solar neighbourhood, and none…

We present optical spectroscopy and near-infrared photometry of 57 faint ($g= 19-22$) high proper motion white dwarfs identified through repeat imaging of $\approx3100$ square degrees of the Sloan Digital Sky Survey footprint by Munn et al.…

We report the discovery of a wide pair (93 arcsec angular separation) of extremely cool ($T_{eff}<4000$ K) white dwarfs with a very large common proper motion ($\sim1.9$ arcsec/yr). The objects were discovered in a high proper motion survey…

Juvenile ultracool dwarfs are late spectral type objects (later than ~M6) with ages between 10 Myr and several 100 Myr. Their age-related properties lie intermediate between very low mass objects in nearby star-forming regions (ages 1-5…

We provide a fine and homogeneous grid of evolutionary sequences for He-core white dwarfs with masses 0.15-0.45 Msun, including the mass range for ELM white dwarfs (<0.20Msun). The grid is appropriate for mass and age determination, and to…