Related papers: Photoionization rates for helium: update
Recent observations suggest that hydrogen reionization ends late ($z \simeq 6$) and proceeds quickly. We present here a new model of the meta-galactic UV/X-ray background (UVB) that is consistent with this. It adopts the most recent…
The reionization epoch of singly ionized helium (He II) is believed to start at redshifts z~3.5--4 and be nearly complete by z~2.7. We explore the post-reionization epoch with far-ultraviolet spectra of the bright, high-redshift quasar…
The exact ionization state of Be7 in the solar core is crucial for the precise prediction of the solar B8 neutrino flux. We therefore examine the effect of pressure ionization on the ionization state of Be7 and all elements with 12 >= Z >=…
The material ejected from a binary neutron star merger produces "kilonova," a radioactively powered emission at ultraviolet, optical, and infrared wavelengths. The early-phase spectra of the kilonova AT2017gfo, following the gravitational…
Transit observations in the helium triplet around 10830 Angstrom are a successful tool to study exoplanetary atmospheres and their mass loss. Forming those lines requires ionisation and recombination of helium in the exoplanetary…
We have determined the solar modulation potential, phi, vs. time that is observed at Voyager 1 and 2 from measurements of the H and He nuclei intensities at a common energy of 250 MeVnuc. The H nuclei have a rigidity 0.7 GV, the He nuclei…
We explore the evolution of a select grid of solar metallicity stellar models from their pre-main sequence phase to near their final fates in a neutrino Hertzsprung-Russell diagram, where the neutrino luminosity replaces the traditional…
We study the production rate of ionizing photons of a sample of 588 H$\alpha$ emitters (HAEs) and 160 Lyman-$\alpha$ emitters (LAEs) at $z=2.2$ in the COSMOS field in order to assess the implied emissivity from galaxies, based on their UV…
Ion-implantation is a useful technique to study irradiation damage in nuclear materials. To study He effects in nuclear fusion conditions, He is co-implanted with damage ions to reproduce the correct He/dpa ratios in the desired or…
Ultrafast processes in matter, such as the electron emission following light absorption, can now be studied using ultrashort light pulses of attosecond duration ($10^{-18}$s) in the extreme ultraviolet spectral range. The lack of spectral…
We have reanalyzed SUMER observations of a parcel of coronal gas using new collisional ionization equilibrium (CIE) calculations. These improved CIE fractional abundances were calculated using state-of-the-art electron-ion recombination…
The solar neutrino capture rate measured by the Russian-American Gallium Experiment (SAGE) on metallic gallium during the period January 1990 through December 1997 is 67.2 (+7.2-7.0) (+3.5-3.0) SNU, where the uncertainties are statistical…
The Solar and Heliospheric Observatory (SOHO) Extreme-ultraviolet Imaging Telescope (EIT) has been taking images of the Solar disk and corona in four narrow EUV bandpasses (171\AA, 195\AA, 284\AA, and 304\AA) at a minimum cadence of once…
Recent observations of thermally emitting isolated neutron stars revealed spectral features that could be interpreted as radiative transitions of He in a magnetized neutron star atmosphere. We present Hartree-Fock calculations of the…
We investigate the loss rates of the hydrogen atmospheres of terrestrial planets with a range of masses and orbital distances by assuming a stellar extreme ultraviolet (EUV) luminosity that is 100 times stronger than that of the current…
A new collection of photodissociation and photoionisation cross sections for 102 atoms and molecules of astrochemical interest has been assembled, along with a brief review of the basic processes involved. These have been used to calculate…
Fluorescence line diagnostics of the Fe K{\alpha} line at $\sim 6.4$ keV observed in both solar and stellar flares can constrain the latitude and size of the flare loop, even in the absence of imaging observations. However, they are…
The temporal evolution of the ionizing UV background radiation field at high redshift provides a probe of the evolution of the early star formation rate. By comparing the observed levels of absorption in the highest redshift quasar spectra…
We study the ionization and thermal evolution of the intergalactic medium during the epoch of \heii reionization by means of radiation hydrodynamical cosmological simulations. We post-process baryonic density fields from a standard…
We present and analyze FUSE observations of six solar analogs. These are single, main-sequence G0-5 strs selected as proxies for the Sun at several stages of its main-sequence lifetime. The emission features in the FUSE 920-1180 A…