Results 41 to 50 of about 1,217 (186)

Towards a Measurement of the Primordial Helium Isotope Ratio

The Astrophysical Journal
We report the discovery of two metastable neutral helium (He I *) absorbers in the Milky Way, and use the upgraded CRyogenic InfraRed Echelle Spectrograph (or CRIRES) on the Very Large Telescope to determine the helium isotope ratio, ^3 He/ ^4 He, along ...
Ryan J. Cooke, James W. Johnson, Pasquier Noterdaeme, Max Pettini, Louise Welsh, Aldric Wong, Céline Péroux   +6 more
doaj   +1 more source

Near‐Earth Cosmic Ray Modulation Index ϕ and Neutron Monitor Cutoff Rigidities at Hourly Cadence: Toward an Improved Monitoring of Solar‐Terrestrial Radiation Environment, Space Weather, and Space Climate

Journal of Geophysical Research: Space Physics, Volume 131, Issue 8, August 2026.
Abstract Cosmic rays (CRs) are energetic particles originating from galactic and extragalactic sources. When arriving into the solar system and the Sun's heliosphere, they are diverted and modulated by the magnetic activity of the Sun. This modulation can be quantified by the modulation parameter ϕ $\phi $ determined with the Force‐field approximation (
Pauli Väisänen, Nicholas Larsen, Sergey Koldobskiy, Markus Similä, David Pelosi, Miguel Orcinha   +5 more
wiley   +1 more source

Spatially Resolved Comparison of SFRs from UV and Hα in GASP Gas-stripped Galaxies

The Astrophysical Journal
Star formation rates (SFRs) in galaxies offer a view of various physical processes across them, and are measured using various tracers, such as H α and ultraviolet (UV).
Neven Tomičić, Ariel Werle, Benedetta Vulcani, Alessandro Ignesti, Alessia Moretti, Anna Wolter, Koshy George, Bianca M. Poggianti, Marco Gullieuszik   +8 more
doaj   +1 more source

Absorption-line Observations of and CO in Sight Lines Toward the Vela and W28 Supernova Remnants

The Astrophysical Journal, 2023
Supernova remnants act as particle accelerators, providing the cosmic-ray protons that permeate the interstellar medium and initiate the ion–molecule reactions that drive interstellar chemistry. Enhanced fluxes of cosmic-ray protons in close proximity to
Nick Indriolo
doaj   +1 more source

Jovian Auroral Proton Precipitation

Journal of Geophysical Research: Space Physics, Volume 131, Issue 8, August 2026.
Abstract The total power of the Jovian aurora is about 1013–1014 W with ultraviolet emission observed in the Lyman and Werner bands of molecular hydrogen. X‐ray, radio, and infrared emissions have also been observed. The Jovian Auroral Distributions Experiment and the Jovian Energetic Particle Detector Instrument onboard the Juno spacecraft, orbiting ...
S. J. Houston, T. E. Cravens, O. Q. Hamil, J. H. Waite, D. R. Schultz   +4 more
wiley   +1 more source

Sloan Digital Sky Survey IV MaStar: Quantification and Abatement of Interstellar Absorption in the Largest Empirical Stellar Spectral Library

The Astrophysical Journal
We assess the impact of Ca ii λ λ 3934, 3969 and Na i λ λ 5891, 5897 absorption arising in the interstellar medium (ISM) on the Sloan Digital Sky Survey-IV MaNGA Stellar Library (MaStar) and produce corrected spectroscopy for 80% of the 24,162-star ...
Kate H. R. Rubin, Kyle B. Westfall, Claudia Maraston, Daniel Thomas, Renbin Yan, J. Christopher Howk, Erick Aguirre, Kaelee S. Parker, David R. Law   +8 more
doaj   +1 more source

Abundances of interstellar atoms from ultaviolet absorption lines

The Astrophysical Journal, 1986
The equivalent widths of interstellar absorption lines of Mg II, P II, Cl I and II, Mn II, Fe II, Cu II, and Ni II, obtained in a Copernicus survey of Bohlin et al (1983) have been analyzed to yield column densities along the lines of sight. The measured depletions are clearly correlated with n sub H, the mean hydrogen column density along the line of ...
E. B. Jenkins, B. D. Savage, L., Jr. Spitzer   +2 more
openaire   +1 more source

Deterministic Propagation of Suprathermal Ions Through the Heliosphere

Journal of Geophysical Research: Space Physics, Volume 131, Issue 7, July 2026.
Abstract The PEPSSI instrument onboard New Horizons is sampling the energy range that bridges pickup and suprathermal He+ ${\mathrm{H}\mathrm{e}}^{+}$ ions for the first time in the outer heliosphere. New Horizons repeatedly encountered structures beyond 30 au that we interpret as the spiral of a corotating interaction region (CIR) for an extended ...
P. Kollmann, E. C. Roelof, M. E. Hill, R. B. Decker, P. Brandt, R. L. McNutt Jr., P. S. Mostafavi, R. Nikoukar, J. W. Parker, K. N. Singer, J. Spencer, A. Stern, A. J. Verbiscer   +12 more
wiley   +1 more source

The Nature of Interstellar Gas toward the Pleiades Revealed in Absorption Lines [PDF]

The Astrophysical Journal, 2006
We present high-resolution, high signal to noise absorption-line observations of CN, Ca II, Ca I, CH^+, and CH along twenty lines of sight toward members of the Pleiades. The acquired data enable the most detailed study to date of the interaction between cluster stars and the surrounding interstellar gas.
Ritchey, A. M., Martinez, M., Pan, K., Federman, S. R., Lambert, D. L.   +4 more
openaire   +2 more sources

Aircraft Ionizing Radiation Exposure for Solar Cycle 24/25 From ARMAS and NAIRAS

Space Weather, Volume 24, Issue 7, July 2026.
Abstract Exposure to ionizing radiation from galactic cosmic rays and solar energetic particles at aviation flight altitudes can have an adverse effect on human health. Although airline crews are classified as radiation workers by the International Commission on Radiological Protection (ICRP), in most countries, their level of exposure is unquantified ...
Daniel B. Phoenix, Christopher J. Mertens, Guillaume P. Gronoff, W. Kent Tobiska   +3 more
wiley   +1 more source