相关论文: Brown Dwarfs as Galactic Chronometers

White dwarf planetary science is a rapidly growing field of research featuring a diverse set of observations and theoretical explorations. Giant planets, minor planets, and debris discs have all been detected orbiting white dwarfs. The…

Radial velocity measurements are presented for 85 late M- and L-type very low mass stars and brown dwarfs obtained with the Magellan Echellette (MagE) spectrograph. Targets primarily have distances within 20 pc of the Sun, with more distant…

Brown dwarfs are massive, giant exoplanet analogues subject to variability and colour changes, known as the L/T transition, fundamental for their thermal evolution. The drivers of the L/T transition remain elusive, with atmospheric…

We make use of a previous well tested Galactic model, but describing the observational behavior of the various stellar components in terms of suitable assumptions on their evolutionary status. In this way we are able to predict the expected…

Using modern isochrones with customized physics and carefully considered statistical techniques, we recompute the age distribution for a sample of 91 micro-lensed dwarfs in the Galactic bulge presented by Bensby et al. (2017) and do not…

I will start by discussing the evolutionary status of the white dwarf *progenitors*, the hot UV bright stars. Observations of UIT-selected UV bright stars in globular clusters suggest that a high percentage of them manage to evolve from the…

With the first observations of debris disks as well as proposed planets around white dwarfs, the question of how rocky planets around such stellar remnants can be characterized and probed for signs of life becomes tangible. White dwarfs are…

We report multi-epoch radial velocities, rotational velocities, and atmospheric parameters for 37 T-type brown dwarfs observed with Keck/NIRSPEC. Using a Markov Chain Monte Carlo forward-modeling method, we achieve median precisions of 0.5…

A simple cooling model of white dwarf stars is re-analyzed in Palatini $f(R)$ gravity. Modified gravity affects the white dwarf structures and consequently their ages. We find that the resulting super-Chandrasekhar white dwarfs need more…

Recent studies revealed viewing-angle-dependent color and spectral trends in brown dwarfs, as well as long-term photometric variability (~100 hr). The origins of these trends are yet unexplained. Here, we propose that these seemingly…

We present narrow band photometry of 91 dwarf ellipticals in the Coma and Fornax clusters taken through the Stromgren (uvby) filter system. Dividing the sample by dwarf morphology into nucleated (dEN) and non-nucleated (dE) dwarfs reveals…

The recently discovered brown dwarf WISE 0855 presents our first opportunity to directly study an object outside the Solar System that is nearly as cold as our own gas giant planets. However the traditional methodology for characterizing…

M dwarfs remain active over longer timescales than their Sunlike counterparts, with potentially devastating implications for the atmospheres of their planets. However, the age at which fully-convective M dwarfs transition from active and…

A variety of observations provide evidence for vigorous motion in the atmospheres of brown dwarfs and directly imaged giant planets. Motivated by these observations, we examine the dynamical regime of the circulation in the atmospheres and…

Radio observations of ultracool dwarfs, objects comprising brown dwarfs and the very lowest mass stars, have mainly focused on analyzing their light-curve and spectral energy distributions providing valuable insights into their magnetic…

Globular clusters contain vast repositories of metal-poor stars that represent some of the oldest stellar generations in the Universe. The archaeological footprint of early Galactic evolution may be retained in the measurable properties of…

This chapter reviews our current knowledge of metal-poor ultracool dwarfs with spectral types later than M7. The current census of M, L, and T subdwarfs is explored. The main colour trends of subdwarfs from the optical to the mid-infrared…

Clouds and hazes are important throughout our solar system and in the atmospheres of brown dwarfs and extrasolar giant planets. Among the brown dwarfs, clouds control the colors and spectra of the L-dwarfs; the disappearance of clouds helps…

The brown dwarf desert describes a range of orbital periods (<5 years) in which fewer brown dwarf-mass companions have been observed around Sun-like stars, when compared to planets and low mass stellar companions. It is therefore theorised…

A detailed analysis of 32 of the 38 halo white dwarf candidates identified by Oppenheimer et al. is presented, based on model atmosphere fits to observed energy distributions built from optical BVRI and infrared JHK CCD photometry.…