Related papers: Cool DZ white dwarfs I: Identification and spectra…
We report the identification of 89 new systems containing ultracool dwarf companions to main sequence stars and white dwarfs, using the citizen science project Backyard Worlds: Planet 9 and cross-reference between Gaia and CatWISE2020.…
We explore the spectral and atmospheric properties of brown dwarfs cooler than the latest known T dwarfs. Our focus is on the yet-to-be-discovered free-floating brown dwarfs in the \teff range from $\sim$800 K to $\sim$130 K and with masses…
Our mid-infrared survey of 124 white dwarfs with the Spitzer Space Telescope and the IRAC imager has revealed an infrared excess associated with the white dwarf WD 2115-560 naturally explained by circumstellar dust. This object is the…
We present the results of a medium resolution optical spectroscopic survey of 92 cool ($3,000 \lesssim T_{\rm eff} \lesssim 4,500\,$K) southern TESS candidate planet hosts, and describe our spectral fitting methodology used to recover…
We present a new sample of M subdwarfs compiled from the 7th data release of the Sloan Digital Sky Survey. With 3517 new subdwarfs, this new sample significantly increases the number of spectroscopically confirmed low-mass subdwarfs. This…
White dwarfs are the final remnants of low- and intermediate-mass stars. Their evolution is essentially a cooling process that lasts for $\sim 10$ Gyr. Their observed properties provide information about the history of the Galaxy, its dark…
Brown dwarf spectra are rich in information revealing of the chemical and physical processes operating in their atmospheres. We apply a recently developed atmospheric retrieval tool to an ensemble of late T-dwarf (600-800K) near infrared…
We present seven evolutionary tracks for low-mass white dwarfs with helium cores, ranging in mass from 0.179 to 0.414 Msol. We generated the pre-white dwarf models from a 1 Msol sequence extending up to the tip of its red-giant branch by…
We conducted a spectropolarimetic survey of 58 high proper-motion white dwarfs which achieved uncertainties of >2 kG in the Halpha line and >5 kG in the upper Balmer line series. The survey aimed at detecting low magnetic fields (< 100 kG)…
We identify 806 ultra-cool dwarfs from their SDSS riz photometry (of which 34 are newly discovered L dwarfs) and obtain proper motions through cross matching with UKIDSS and 2MASS. Proper motion and distance constraints show that nine of…
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…
Our ongoing spectroscopic survey of high proper motion stars is a rich source of new magnetic white dwarfs. We present a few examples among cool white dwarfs showing the effect of field strength and geometry on the observed optical…
The article covers the physical properties and evolution of single white dwarfs ranging in temperature from 20,000K to 200,000 and higher, the hottest know electron-degenerate stars. After discussing the classification of their spectra, the…
We have undertaken a detailed near-IR spectroscopic analysis of eight notable white dwarfs, predominantly of southern declination. In each case the spectrum failed to reveal compelling evidence for the presence of a spatially unresolved,…
The metal abundances in the atmospheres of hot white dwarfs (WDs) entering the cooling sequence are determined by the preceding Asymptotic Giant Branch (AGB) evolutionary phase and, subsequently, by the onset of gravitational settling and…
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…
We examine the emergent fluxes from helium-core white dwarfs following their evolution from the end of pre-white dwarf stages down to advanced cooling stages. For this purpose, we include a detailed treatment of the physics of the…
In the era of modern digital sky surveys, uncertainties in the flux of stellar standards are commonly the dominant systematic error in photometric calibration and can often affect the results of higher-level experiments. The Hubble Space…
The latest Gaia data release provides low-resolution spectra for approximately 100 000 white dwarfs. Though useful for pre-classification, they lack the resolution required for accurate spectral type and parameter determination, motivating…
We report the discovery of seven high proper motion stars with proper motions between about 0.7 and 2.2 arcsec/yr. They were detected in an archival search using multi-epoch positions in the optical SuperCOSMOS Sky Surveys and in the…