相关论文: Calibrating models of ultralow-mass stars

We have computed a grid of high resolution synthetic spectra for cool stars (2500<Teff<6000 K) in the wavelength range 6000 -- 10200A, by employing an updated line list of atomic and molecular lines, together with state-of-the-art model…

Recent detections of thermal inversions in the dayside atmospheres of some hot Jupiters are motivating new avenues to understand the interplay between their temperature structures and other atmospheric conditions. In particular, TiO has…

Interferometric radius measurements provide a direct probe of the fundamental parameters of M dwarfs, but is within reach for only a limited sample of nearby, bright stars. We use interferometrically-measured radii, bolometric luminosities,…

We compare the structures of model atmospheres and synthetic spectra calculated using different line lists for TiO and water vapor. We discuss the effects of different line list combinations on the model strutures and spectra for both dwarf…

TiO plays an important role in determining the atmospheric structure of M-type stars and in shaping the visual part of their spectra. We compute synthetic spectra for late-type M giants and identify systematic discrepancies in the…

The spectral type is a key parameter in calibrating the temperature which is required to estimate the mass of young stars and brown dwarfs. We describe an approach developed to classify low-mass stars and brown dwarfs in the Trapezium…

We introduce a new color index consisting of two spectral band width to measure TiO absorption band strength centered at 567 nm. Based on the most up-to-date line list for TiO we regenerate a grid of synthesized spectra and investigate the…

M subdwarfs are metal poor and cool stars. They are important probes of the old galactic populations. However, they remain elusive due to their low luminosity. Observational and modeling efforts are required to fully understand the physics…

By careful searching of synthetic and observed spectra in a sample of cool giant and supergiant stars, we have updated the continuum band-passes of near-infrared Wing three filter system. This photometric system measures the strength of…

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…

Tight binaries discovered in young, nearby associations, with known distances, are ideal targets to provide dynamical mass measurements to test the physics of evolutionary models at young ages and very low masses. We report for the first…

Knowledge of late K and M dwarf metallicities can be used to guide planet searches and constrain planet formation models. However, the determination of metallicities of late-type stars is difficult because visible wavelength spectra of…

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…

(abridged) We present an analysis of high resolution optical spectra for a sample of very young, mid- to late M, low-mass stellar and substellar objects in Upper Sco and Taurus. Effective temperatures (T_eff) and surface gravities are…

We present new calibrations of stellar parameters of O stars at solar metallicity taking non-LTE, wind, and line-blanketing effects into account. Gravities and absolute visual magnitudes are derived from results of recent spectroscopic…

(Abridged) Low-mass stars have been recognised as promising targets in the search for rocky, small planets with the potential of supporting life. Doppler search programmes using high-resolution spectrographs like HARPS or HARPS-N are…

We derive the stellar parameters of a sample of Galactic early-O type stars by analysing their UV and Far-UV spectra from FUSE (905-1187A), IUE, HST-STIS and ORFEUS (1200-2000A). The data have been modeled with spherical, hydrodynamic,…

By comparing near-infrared spectra with atmosphere models, we infer the effective temperature, surface gravity, projected rotational velocity, and radial velocity for 21 very-low-mass stars and brown dwarfs. The unique sample consists of…

L-band spectroscopy is a powerful probe of cool low-gravity atmospheres: The P, Q, and R branch fundamental transitions of methane near 3.3 $\mu$m provide a sensitive probe of carbon chemistry; cloud thickness modifies the spectral slope…

Context. M subdwarfs are metal poor and cool stars. They are important probes of the old galactic populations. However, they remain elusive due to their low luminosity. Observational and modeling efforts are required to fully understand…