Related papers: Improved Stark Broadened Profiles for Neutral Heli…
Extreme helium stars (EHe stars) are hydrogen-deficient supergiants of spectral type A and B. They are believed to result from mergers in double degenerate systems. In this paper we present a detailed quantitative non-LTE spectral analysis…
We detect the neutral hydrogen (HI) radial brightness temperature profile in large-scale haloes by stacking 48,430 galaxies selected from the 2dFGRS catalogue onto a set of 21-cm intensity maps obtained with the Parkes radio telescope,…
We present an analysis of all single white dwarf stars known to exhibit spectroscopic signatures of neutral helium line splitting due to the presence of a strong magnetic field. Using state-of-the-art models taking into account the effects…
We study the density profile and shape of the Galactic halo using deep multicolour images from the MENeaCS and CCCP projects, over 33 fields selected to avoid overlap with the Galactic plane. Using multicolour selection and PSF…
In thermal plasma spectroscopy, Stark broadening measurement of hydrogen spectral lines is considered to be a good and reliable measurement for electron density. Unlike intensity based measurements, Stark broadening measurements can pose a…
We present an update of the grid of detailed atmosphere models and homogeneous synthetic spectra for hot, high-gravity subdwarf stars. High-resolution spectra and synthetic photometry were calculated in the wavelength range 1,000 \r{A} -…
In this paper, we present corrections to the spectroscopic parameters of DB and DBA white dwarfs with -10.0 < log(H/He) < -2.0, 7.5 < log(g) < 9.0 and 12000 K < T_eff < 34000 K, based on 282 3D atmospheric models calculated with the CO5BOLD…
Ultracool stellar atmospheres show absorption by alkali resonance lines severely broadened by collisions with neutral perturbers. In the coolest and densest atmospheres, such as those of T dwarfs, Na I and K I broadened by molecular…
We present a grid of synthetic profiles of stellar H Balmer and HeI lines at optical wavelengths with a sampling of 0.3 A. The grid spans a range of effective temperature 4000 K < Teff < 50000 K, and gravity 0.0 < log g < 5.0 at solar…
Quantitative analyses of extreme helium stars to date face the difficulty that theory fails to reproduce the observed helium lines in their entirety, wings and line cores. Here, we demonstrate how the issues can be resolved using…
For the first time, we use the Gamma-ray Burst Monitor (GBM) on-board the Fermi satellite to search for sterile neutrino decay lines in the energy range 10-25 keV corresponding to sterile neutrino mass range 20-50 keV. This energy range has…
We present Keck NIRSPEC and Keck NIRES spectroscopy of sixteen metal-poor galaxies that have pre-existing optical observations. The near-infrared (NIR) spectroscopy specifically targets the HeI 10830A emission line, due to its sensitivity…
Neutral sodium is an important tracer of the Galactic chemical evolution, a powerful diagnostic of different stellar populations, and the subject of detailed studies of exoplanet atmospheres via transmission spectroscopy. This work aims to…
The measurement of oxygen lines in metal-poor unevolved stars, in particular near-UV OH lines, can provide invaluable information on the properties of the Early Galaxy. Near-UV OH lines constitute an important tool to derive oxygen…
We model the distribution of the observed profiles of 21 cm line emission from neutral hydrogen (HI) in central galaxies selected from a statistically representative mock catalog of the local Universe in the Lambda-cold dark matter…
We present preliminary results of an experimental study exploring helium at photospheric conditions of white dwarf stars. These data were collected at Sandia National Laboratories' Z-machine, the largest x-ray source on earth. Our helium…
Stark broadened lines of the hydrogen Brackett series are computed for the conditions of stellar atmospheres and circumstellar envelopes. The computation is performed within the Model Microfield Method, which includes the ion dynamic…
Thermonuclear burning on the surface of accreting neutron stars is observed to stabilize at accretion rates almost an order of magnitude lower than theoretical models predict. One way to resolve this discrepancy is by including a base…
The main goal of this analysis is to present a new method to estimate the physical properties of diffuse cloud of atomic hydrogen observed at high Galactic latitude. This method, based on a comparison of the observations with fractional…
The photospheres of the coolest helium-atmosphere white dwarfs are characterized by fluid-like densities. Under those conditions, standard approximations used in model atmosphere codes are no longer appropriate. Unfortunately, the majority…