Related papers: Astrophysical Ionizing Radiation and the Earth: A …
The rapid time variability of gamma-ray bursts implies the sources are very compact, and the peak luminosities are so high that some matter must be ejected at ultra-relativistic speeds. The very large Lorentz factors of the bulk flow are…
The propagation of $\gamma$ rays over very large distances provides new insights on the intergalactic medium and on fundamental physics. On their path to the Earth, $\gamma$ rays can annihilate with diffuse infrared or optical photons of…
Continuous habitability of a planet is a critical condition for advanced forms of life to appear, but it can be endangered by astronomical events such as stellar encounters. The purpose of this study is to analyze close stellar encounters…
Venus' atmosphere -- specifically its clouds buoyed up 40 to 60 km above the surface -- has long been suspected to encompass a biosphere where Earth-like living organisms could grow and flourish. This idea has been recently rekindled by the…
It is known that a gamma ray burst (GRB) originating near the Earth could be devastating to life. The mechanism of ozone depletion and subsequent increased UVB exposure is the primary risk, but models also show increased nitrification…
Stellar activity can reveal itself in the form of radiation (eg, enhanced X-ray coronal emission, flares) and particles (eg, winds, coronal mass ejections). Together, these phenomena shape the space weather around (exo)planets. As stars…
We employ three-dimensional state of the art magnetohydrodynamic models of the early solar wind and heliosphere and a two-dimensional model for cosmic ray transport to investigate the cosmic ray spectrum and flux near the Archean Earth. We…
Estimates of the time at which life arose on Earth make use of two types of evidence. First, astrophysical and geophysical studies provide a timescale for the formation of Earth and the Moon, for large impact events on early Earth, and for…
Diffuse ultrahigh energy gamma-radiation can arise from a variety of astrophysical sources, including the interaction of extremely high energy cosmic rays with the 3K microwave background radiation or the collapse of topological defects…
The Gerasimova-Zatsepin effect of collisions of ultra-high-energy cosmic ray nuclei with photons emitted by the sun may cause two simultaneous air showers on Earth. This effect is simulated using the full energy spectrum of solar photons,…
The field of astrobiology has made tremendous progress in modelling galactic-scale habitable zones which offer a stable environment for life to form and evolve in complexity. Recently, this idea has been extended to cosmological scales by…
We explore if carbon-based macromolecules (such as DNA) in the environments of stars other than the Sun are able to survive the effects of photospheric stellar radiation, such as UV-C. Therefore, we focus on main-sequence stars of spectral…
The fate of ionizing radiation is vital for understanding cosmic ionization, energy budgets in the interstellar and intergalactic medium, and star formation rate indicators. The low observed escape fractions of ionizing radiation have not…
Searches for transient astrophysical sources often reveal unexpected classes of objects that are useful physical laboratories. In a recent survey for pulsars and fast transients we have uncovered four millisecond-duration radio transients…
(Abridged) We show that sizeable fractions of incident ionizing radiation from stochastic astrophysical sources can be redistributed to biologically and chemically important UV wavelengths, a significant fraction of which can reach the…
The Cosmic Background due to the integrated radiation from galaxies over the whole life of the Universe is reviewed. We find that this background is well constrained by measurements. The total power in the background is in the range 60-93…
High-energy neutrino emission has been predicted for several short-lived astrophysical transients including gamma-ray bursts (GRBs), core-collapse supernovae with choked jets and neutron star mergers. IceCube's optical and X-ray follow-up…
Following recent suggestions of a gamma-ray burst origin of large ISM holes (supershells) detected in the galaxy, we discuss the effects of the recently discovered shell GSH 238+00+09 (and other nearby extremely energetic supershells) on…
When modelling the ionisation of gas in the intergalactic medium after reionisation, it is standard practice to assume a uniform radiation background. This assumption is not always appropriate; models with radiative transfer show that…
Galactic diffuse emissions in gamma rays and neutrinos arise from interactions of cosmic rays with the interstellar medium and probe the cosmic-ray intensity away from the Solar system. Model predictions for those are influenced by the…