相关论文: A Comparative L-dwarf Sample Exploring the Interpl…

The spectroscopic features of white dwarfs are formed in the thin upper layer of their stellar photosphere. These features carry information about the white dwarf's surface temperature, surface gravity, and chemical composition (hereafter…

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…

M-dwarf stars are the most numerous stars in the Universe; they span a wide range in mass and are in the focus of ongoing and planned exoplanet surveys. To investigate and understand their physical nature, detailed spectral information and…

The metal content of a galaxy's interstellar medium reflects the interplay between different evolutionary processes such as feedback from massive stars and the accretion of gas from the intergalactic medium. Despite the expected abundance…

Cassini's observations of Titan's atmosphere are exemplary benchmarks for exoplanet atmospheric studies owing to (1) their precision and (2) our independent knowledge of Titan. Leveraging these observations, we perform retrievals (i.e.,…

We design a convolutional neural network (CNN) incorporating channel attention and spatial attention mechanisms to predict atmospheric parameters of hot subdwarfs. The experimental dataset comprises spectra at nine distinct signal-to-noise…

Brown dwarfs are compact objects that do not reach temperatures high enough to produce sustained hydrogen fusion. Consequently, they cool over time, gradually evolving through later spectral types. In fact, three new spectral types (L, T,…

A sophisticated approach to condensate opacity is required to properly model the atmospheres of L and T dwarfs. Here we review different models for the treatment of condensates in brown dwarf atmospheres. We conclude that models which…

We present the discovery of 11 new T dwarfs, found during the course of a photometric survey for mid-to-late T dwarfs in the 2MASS Point Source Catalog and from a proper motion selected sample of ultracool dwarfs in the 2MASS Working…

We present analyses of high resolution and medium resolution spectra of early L dwarfs. We used our latest set of model atmospheres to reproduce and analyze the observed features. We can model the optical flux and the atomic line profiles…

We report the discovery of 47 new T dwarfs in the Fourth Data Release (DR4) from the Large Area Survey (LAS) of the UKIRT Infrared Deep Sky Survey with spectral types ranging from T0 to T8.5. These bring the total sample of LAS T dwarfs to…

The evolution of brown dwarfs from L to T spectral types is one of the least understood aspects of the ultracool population, partly for lack of a large, well-defined, and well-characterized sample in the L/T transition. To improve the…

A test case comparison is presented for different dust cloud model approaches applied in brown dwarfs and giant gas planets. We aim to achieve more transparency in evaluating the uncertainty inherent to theoretical modelling. We show in how…

Recent JWST measurements allow access to the near-infrared spectrum of the sub-Neptune TOI-270 d, for which two different interpretations, a high-metallicity miscible envelope and a lower metallicity hycean world, are currently in conflict.…

We present a catalog of uniformly determined stellar properties and abundances for 1626 F, G, and K stars using an automated spectral synthesis modeling procedure. All stars were observed using the HIRES spectrograph at Keck Observatory.…

We present JHKs photometry, far red spectra, and spectral classifications for an additional 67 L dwarfs discovered by the Two Micron All Sky Survey. One of the goals of this new search was to locate more examples of the latest L dwarfs. Of…

M dwarfs are key targets for high-resolution spectroscopic analyses due to a high incidence of these stars in the solar neighbourhood and their importance as exoplanetary hosts. Several methodological challenges make such analyses…

I present the results of a program to spectrophotometrically monitor the L1.5 dwarf 2MASSW J1145572+231730 to identify the cause of photospheric variability in ultra cool dwarfs. Plausible candidates are magnetically-induced star spots and…

Model atmospheres have been computed for M dwarfs that are strongly irradiated by nearby hot companions. A variety of primary and secondary spectral types are explored in addition to models specific to four known systems: GD 245, NN Ser, AA…

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…