Related papers: Primary neutral helium in the heliosphere
The heliosphere is predominantly a partially ionized plasma that consists of electrons, ions and significant neutral atoms. Nonlinear interactions amongst these species take place through direct collision or charge exchange processes. These…
Absorption of stellar X-ray and Extreme Ultraviolet radiation in the upper atmosphere of close-in exoplanets can give rise to hydrodynamic outflows, which may lead to the gradual shedding of their primordial, light element envelopes. Excess…
Transiting exoplanets provide detailed access to their atmospheres, as the planet's signal can be effectively separated from that of its host star. For transiting exoplanets three fundamental atmospheric measurements are possible:…
Strong absorption signatures in the helium line at 1083 nm have recently been detected in transmission spectra of several close-in exoplanets. This absorption line originates from neutral helium atoms in an excited, metastable 2$^3$S state.…
We present modeled flux and linear polarisation signals of starlight that is reflected by spatially unresolved, horizontally inhomogeneous planets and discuss the effects of including horizontal inhomogeneities on the flux and polarisation…
Interstellar dust permeates our Galaxy and plays an important role in many physical processes in the diffuse and dense regions of the interstellar medium. High-resolution X-ray spectroscopy, coupled with modelling based on laboratory dust…
Interstellar dust has been detected in situ flowing through the heliosphere. However, our ability to derive the density and size distribution of the interstellar dust in the local interstellar medium from this directly detected dust…
We construct partially ionized hydrogen atmosphere models for magnetized neutron stars in radiative equilibrium with surface fields B=10^12-5 \times 10^14 G and effective temperatures T_eff \sim a few \times 10^5-10^6 K. These models are…
With more than a dozen significant detections, the helium triplet has emerged as a key tracer of evaporating exoplanet atmospheres. This near-infrared feature can be observed from the ground and holds great promise, especially with upcoming…
This is the first in a series of three papers describing a project with the Cosmic Origins Spectrograph on the Hubble Space Telescope to measure abundances of the neutral interstellar medium (ISM) in a sample of 9 nearby star-forming…
A scanning helium microscope typically utilises a thermal energy helium atom beam, with an energy and wavelength (<100 meV, ~0.05 nm) particularly sensitive to surface structure. An angular detector stage for a scanning helium microscope is…
A broad array of interstellar absorption features that appear in the ultraviolet spectra of bright sources allows us to measure the abundances and ionization states of many important heavy elements that exist as free atoms in the…
Using deep Chandra observations of the globular cluster M28, we study the quiescent X-ray emission of a neutron star in a low-mass X-ray binary in order to constrain the chemical composition of the neutron star atmosphere and the equation…
In a previous paper, we calculated numerical hydrodynamic models of the interstellar medium in the Galaxy, which suggested that hot gas (T $\ge$ 3 $\times$ 10$^5$ K) has a filling factor near 50\% in the midplane (Rosen \& Bregman 1995, ApJ…
Observations of molecular clouds, prestellar cores, and protoplanetary disks have established that the HNC/HCN ratio may be a potent diagnostic of molecular gas physical conditions. The processes that govern the relative abundances of these…
One of the most outstanding issues in exoplanet characterization is understanding the prevalence of obscuring clouds and hazes in their atmospheres. The ability to predict the presence of clouds/hazes a priori is an important goal when…
We compare predictions of large-scale cosmological hydrodynamical simulations for neutral hydrogen absorption signatures in the vicinity of 1e11 - 1e12.5 MSun haloes with observational measurements. Two different hydrodynamical techniques…
Helioscopes, such as the proposed International Axion Observatory (IAXO), have significant discovery potential for axions and axion-like particles. In this note, we argue that beyond discovery they can resolve details of the model. In…
This paper presents a statistical explanation of filament formation in the galactic atomic hydrogen. Recently developed technique allows to determine the 3D spectrum of random HI density. We claim that even in the absence of dynamical…
A two-dimensional, time-dependent numerical model is used to calculate the modulation of cosmic rays in the heliosphere. Computations are compared to spacecraft observations in the inner and outer heliosphere. It is shown that the model…