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Now showing items 31-40 of 96
How do stars gain their mass? : A JCMT/SCUBA-2 Transient Survey of Protostars in Nearby Star Forming Regions
(2017-10-27)
Most protostars have luminosities that are fainter than expected from steady accretion over the protostellar lifetime. The solution to this problem may lie in episodic mass accretion -- prolonged periods of very low accretion ...
Uniform Atmospheric Retrieval Analysis of Ultracool Dwarfs II : Properties of 11 T-dwarfs
(2017-10-20)
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) ...
Surprisingly different starspot distributions on the near equal-mass equal-rotation-rate stars in the M dwarf binary GJ 65 AB
(2017-10-11)
We aim to understand how stellar parameters such as mass and rotation impact the distribution of starspots on the stellar surface. To this purpose, we have used Doppler imaging to reconstruct the surface brightness ...
Ultracool dwarf benchmarks with \emph{Gaia} primaries
(2017-10-01)
We explore the potential of \emph{Gaia} for the field of benchmark ultracool/brown dwarf companions, and present the results of an initial search for metal-rich/metal-poor systems. A simulated population of resolved ultracool ...
Retrieval of atmospheric properties of cloudy L dwarfs
(2017-09-01)
We present the first results from applying the spectral inversion technique in the cloudy L dwarf regime. Our new framework provides a flexible approach to modelling cloud opacity which can be built incrementally as the ...
Uncertainties in s-process nucleosynthesis in massive stars determined by Monte Carlo variations
(2017-08-01)
The $s$-process in massive stars produces the weak component of the $s$-process (nuclei up to $A \sim 90$), in amounts that match solar abundances. For heavier isotopes, such as barium, production through neutron capture ...
A Tale of Three Cities : OmegaCAM discovers multiple sequences in the color-magnitude diagram of the Orion Nebula Cluster
(2017-07-27)
As part of the Accretion Discs in H$\alpha$ with OmegaCAM (ADHOC) survey, we imaged in r, i and H-alpha a region of 12x8 square degrees around the Orion Nebula Cluster. Thanks to the high-quality photometry obtained, we ...
The Gaia Ultracool Dwarf Sample. I. Known L and T dwarfs and the first Gaia data release
(2017-07-01)
We identify and investigate known ultracool stars and brown dwarfs that are being observed or indirectly constrained by the Gaia mission. These objects will be the core of the Gaia ultracool dwarf sample composed of all ...
The metal rich abundance pattern - spectroscopic properties and abundances for 107 main-sequence stars
(2017-07-01)
We report results from the high resolution spectral analysis of the 107 metal rich (mostly [Fe/H]$\ge$7.67 dex) target stars from the Calan-Hertfordshire Extrasolar Planet Search program observed with HARPS. Using our ...
Low-resolution near-infrared spectroscopic signatures of unresolved ultracool companions to M dwarfs
(2017-06-01)
We develop a method to identify the spectroscopic signature of unresolved L-dwarf ultracool companions, which compares the spectra of candidates and their associated control stars using spectral ratio differences and ...