2,054 results match your criteria Astrophysical Journal[Journal]

Nitrogen Fixation at Early Mars.

Astrobiology 2021 Jul 30. Epub 2021 Jul 30.

Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA.

The Mars Science Laboratory (MSL) recently discovered nitrates in Gale Crater (, Stern , 2015; Sutter , 2017). One possible mechanism for ancient nitrate deposition on Mars is through HNOx formation and rain out in the atmosphere, for which lightning-induced NO is likely the fundamental source. This study investigates nitrogen (N) fixation in early Mars' atmosphere, with implications for early Mars' habitability. Read More

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Ultrasonic Propagation in Liquid and Ice Water Drops. Effect of Porosity.

Sensors (Basel) 2021 Jul 13;21(14). Epub 2021 Jul 13.

Faculty of Aerospace Engineering, Delft University of Technology, 2629 HS Delft, The Netherlands.

This work studies ultrasonic propagation in liquid and ice water drops. The effect of porosity on attenuation of ultrasonic waves in the drops is also explored. The motivation of this research was the possible application of ultrasonic techniques to the study of interstellar and cometary ice analogs. Read More

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Atom-Diatom Reactive Scattering Collisions in Protonated Rare Gas Systems.

Molecules 2021 Jul 11;26(14). Epub 2021 Jul 11.

Department of Chemistry, Indian Institute of Technology Guwahati, Assam 781039, India.

The study of the dynamics of atom-diatom reactions involving two rare gas (Rg) atoms and protons is of crucial importance given the astrophysical relevance of these processes. In a series of previous studies, we have been investigating a number of such Rg(1)+ Rg(2)H+→ Rg(2)+ Rg(1)H+ reactions by means of different numerical approaches. These investigations comprised the construction of accurate potential energy surfaces by means of ab initio calculations. Read More

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Pressure-Induced Superionicity of H in Hypervalent Sodium Silicon Hydrides.

J Phys Chem Lett 2021 Jul 23:7166-7172. Epub 2021 Jul 23.

Asian School of the Environment, Nanyang Technological University, Singapore 639798.

Superionic states simultaneously exhibit properties of a fluid and a solid. Proton (H) superionicity in ice, HO, He-HO, and He-NH compounds is well-studied. However, hydride (H) superionicity in H-rich compounds is rare, being associated with instability and strongly reducing conditions. Read More

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Nonresonant Diffusion in Alpha Channeling.

Phys Rev Lett 2021 Jul;127(2):025003

Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08540, USA.

The gradient of fusion-born alpha particles that arises in a fusion reactor can be exploited to amplify waves, which cool the alpha particles while diffusively extracting them from the reactor. The corresponding extraction of the resonant alpha particle charge has been suggested as a mechanism to drive rotation. By deriving a coupled linear-quasilinear theory of alpha channeling, we show that, for a time-growing wave with a purely poloidal wave vector, a current in the nonresonant ions cancels the resonant alpha particle current, preventing the rotation drive but fueling the fusion reaction. Read More

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Solar UV-B/A radiation is highly effective in inactivating SARS-CoV-2.

Sci Rep 2021 07 20;11(1):14805. Epub 2021 Jul 20.

Department of Pathophysiology and Transplantation, University of Milano, Don C. Gnocchi Foundation, IRCCS, Milan, Italy.

Solar UV-C photons do not reach Earth's surface, but are known to be endowed with germicidal properties that are also effective on viruses. The effect of softer UV-B and UV-A photons, which copiously reach the Earth's surface, on viruses are instead little studied, particularly on single-stranded RNA viruses. Here we combine our measurements of the action spectrum of Covid-19 in response to UV light, Solar irradiation measurements on Earth during the SARS-CoV-2 pandemics, worldwide recorded Covid-19 mortality data and our "Solar-Pump" diffusive model of epidemics to show that (a) UV-B/A photons have a powerful virucidal effect on the single-stranded RNA virus Covid-19 and that (b) the Solar radiation that reaches temperate regions of the Earth at noon during summers, is sufficient to inactivate 63% of virions in open-space concentrations (1. Read More

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Memory in three-dimensional cyclically driven granular material.

Phys Rev E 2021 Jun;103(6-1):062906

Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742-2431, USA.

We perform experimental and numerical studies of a granular system under cyclic compression to investigate reversibility and memory effects. We focus on the quasistatic forcing of dense systems, which is most relevant to a wide range of geophysical, industrial, and astrophysical problems. We find that soft-sphere simulations with proper stiffness and friction quantitatively reproduce both the translational and rotational displacements of the grains. Read More

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Spectrum of kinetic plasma turbulence at 0.3-0.9 astronomical units from the Sun.

Phys Rev E 2021 Jun;103(6-1):063202

LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, F-92195 Meudon, France.

We investigate spectral properties of turbulence in the solar wind that is a weakly collisional astrophysical plasma, accessible to in situ observations. Using the Helios search coil magnetometer measurements in the fast solar wind, in the inner heliosphere, we focus on properties of the turbulent magnetic fluctuations at scales smaller than the ion characteristic scales, the so-called kinetic plasma turbulence. At such small scales, we show that magnetic power spectra between 0. Read More

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Collisions in a gas-rich white dwarf planetary debris disc.

Mon Not R Astron Soc 2021 Sep 21;506(1):432-440. Epub 2021 Jun 21.

Department of Physical Sciences, Embry-Riddle Aeronautical University, Daytona Beach, FL 32114, USA.

WD 0145+234 is a white dwarf that is accreting metals from a circumstellar disc of planetary material. It has exhibited a substantial and sustained increase in 3-5 [Formula: see text]m flux since 2018. Follow-up photometry reveals that emission from the disc had begun to decrease by late 2019. Read More

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September 2021

Revealing the source of Jupiter's x-ray auroral flares.

Sci Adv 2021 Jul 9;7(28). Epub 2021 Jul 9.

Space Science and Engineering Division, Southwest Research Institute, San Antonio, TX, USA.

Jupiter's rapidly rotating, strong magnetic field provides a natural laboratory that is key to understanding the dynamics of high-energy plasmas. Spectacular auroral x-ray flares are diagnostic of the most energetic processes governing magnetospheres but seemingly unique to Jupiter. Since their discovery 40 years ago, the processes that produce Jupiter's x-ray flares have remained unknown. Read More

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Measurements of electron temperature in high-energy-density plasmas using gated x-ray pinhole imaging.

Rev Sci Instrum 2021 Apr;92(4):043524

Lawrence Livermore National Laboratory, Livermore, California 94550, USA.

We present measurements of spatially and temporally resolved electron temperature in high-energy-density plasmas using gated x-ray pinhole imagers. A 2D image of bremsstrahlung x-ray self-emission from laser-driven plasma plumes is detected at the same time through two pinholes covered with different filter materials. By comparing the attenuated signal through each filter, a spatially resolved electron temperature as low as 0. Read More

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Automated source of squeezed vacuum states driven by finite state machine based software.

Rev Sci Instrum 2021 May;92(5):054504

INFN, Sezione di Genova, I-16146 Genova, Italy.

In the last few decades, much effort has been made for the production of squeezed vacuum states in order to reduce quantum noise in the audio-frequency band. This technique has been implemented in all running gravitational-wave interferometric detectors and helped to improve their sensitivity. While the detectors are acquiring data for astrophysical observations, they must be kept in the operating condition, also called "science mode," that is, a state that requires the highest possible duty-cycle for all the instrumental parts and controls. Read More

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Electric quadrupole transitions in carbon dioxide.

J Chem Phys 2021 Jun;154(21):211104

Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom.

Recent advances in high sensitivity spectroscopy have made it possible, in combination with accurate theoretical predictions, to observe, for the first time, very weak electric quadrupole transitions in a polar polyatomic molecule of water. Here, we present accurate theoretical predictions of the complete quadrupole rovibrational spectrum of a non-polar molecule CO, important in atmospheric and astrophysical applications. Our predictions are validated by recent cavity enhanced absorption spectroscopy measurements and are used to assign few weak features in the recent ExoMars Atmospheric Chemistry Suite mid-infrared spectroscopic observations of the Martian atmosphere. Read More

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Prompt Response of the Dayside Magnetosphere to Discrete Structures Within the Sheath Region of a Coronal Mass Ejection.

Geophys Res Lett 2021 Jun 1;48(11):e2021GL092700. Epub 2021 Jun 1.

Department of Physics and Astronomy University of Iowa Iowa City IA USA.

A sequence of discrete solar wind structures within the sheath region of an interplanetary coronal mass ejection on November 6, 2015, caused a series of compressions and releases of the dayside magnetosphere. Each compression resulted in a brief adiabatic enhancement of ions (electrons) driving bursts of electromagnetic ion cyclotron (EMIC; whistler mode chorus) wave growth across the dayside magnetosphere. Fine-structured rising tones were observed in the EMIC wave bursts, resulting in nonlinear scattering of relativistic electrons in the outer radiation belt. Read More

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Astrochemical Pathways to Complex Organic and Prebiotic Molecules: Experimental Perspectives for In Situ Solid-State Studies.

Life (Basel) 2021 Jun 17;11(6). Epub 2021 Jun 17.

Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany.

A deep understanding of the origin of life requires the physical, chemical, and biological study of prebiotic systems and the comprehension of the mechanisms underlying their evolutionary steps. In this context, great attention is paid to the class of interstellar molecules known as "Complex Organic Molecules" (COMs), considered as possible precursors of prebiotic species. Although COMs have already been detected in different astrophysical environments (such as interstellar clouds, protostars, and protoplanetary disks) and in comets, the physical-chemical mechanisms underlying their formation are not yet fully understood. Read More

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Topological phases and bulk-edge correspondence of magnetized cold plasmas.

Yichen Fu Hong Qin

Nat Commun 2021 Jun 24;12(1):3924. Epub 2021 Jun 24.

Princeton Plasma Physics Laboratory, Princeton, NJ, USA.

Plasmas have been recently studied as topological materials. However, a comprehensive picture of topological phases and topological phase transitions in cold magnetized plasmas is still missing. Here we systematically map out all the topological phases and establish the bulk-edge correspondence in cold magnetized plasmas. Read More

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Inclusion of ionizing radiation in a mathematical model for photosynthesis.

Radiat Environ Biophys 2021 Aug 23;60(3):431-435. Epub 2021 Jun 23.

Institute of Biochemistry and Microbiology, Austral University of Chile, Valdivia, Chile.

Ionizing radiation of astrophysical origin might have played an important role in biological evolution during the long course of Earth's evolution. Several phenomena might have induced intense fluctuations in background ionizing radiation, such as highly energetic stellar explosions. There might also be anthropogenic causes for environmental radiation fluctuations, resulting from nuclear industry activities. Read More

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Anomalous formation of trihydrogen cations from water on nanoparticles.

Nat Commun 2021 Jun 22;12(1):3839. Epub 2021 Jun 22.

Department of Physics, American University of Sharjah, Sharjah, UAE.

Regarded as the most important ion in interstellar chemistry, the trihydrogen cation, [Formula: see text], plays a vital role in the formation of water and many complex organic molecules believed to be responsible for life in our universe. Apart from traditional plasma discharges, recent laboratory studies have focused on forming the trihydrogen cation from large organic molecules during their interactions with intense radiation and charged particles. In contrast, we present results on forming [Formula: see text] from bimolecular reactions that involve only an inorganic molecule, namely water, without the presence of any organic molecules to facilitate its formation. Read More

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Isomerization Dynamics in the Symmetric and Asymmetric Fragmentation of Ethane Dications.

J Phys Chem Lett 2021 Jun 17;12(24):5789-5795. Epub 2021 Jun 17.

Institute of Modern Physics, Key Laboratory of Nuclear Physics and Ion-Beam Application (MOE), Fudan University, Shanghai 200433, China.

Hydrogen- or proton-migration-induced isomerization has recently been of concern for its critical role in the dissociation of organic molecules of astrophysical or biological relevance. Herein we present a combined experimental and theoretical study of the two-body C-C bond breakdown dissociation of ethane dication. For the asymmetric fragmentation channel CH + CH, the kinetic energy release measurements and quantum chemical calculations demonstrate that the reaction pathway involving hydrogen-migration-induced isomerization of [CH-CH] to [CH-CH] can be accessed the lowest triplet state rather than the ground singlet state of ethane dication. Read More

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Hydrogenation of C Carbon Clusters: Structural Diversity and Energetic Properties.

J Phys Chem A 2021 Jun 16. Epub 2021 Jun 16.

Laboratoire de Chimie et Physique Quantiques (LCPQ), Fédération FeRMI, Université Toulouse UT3 and CNRS, UMR5626, 118 Route Narbonne, F-31062 Toulouse, France.

This work aims at exploring the potential energy surfaces of CH using the genetic algorithm in combination with the density functional based tight binding potential. The structural diversity was analyzed using order parameters, in particular the sum of the numbers of 5- and 6-carbon rings . The most abundant and lowest energy population was designated as the flake population (isomers of variable shapes, large values), characterized by an increasing number of spherical isomers when / increases. Read More

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Exploring the electronic states of the hydroxyl dication OH: thermodynamic (meta)stability, bound-free emission spectra, and charge transfer processes.

Phys Chem Chem Phys 2021 Jun;23(24):13672-13679

Universidade de São Paulo, Instituto de Química, Departamento de Química Fundamental, Av. Prof. Lineu Prestes, 748, São Paulo, São Paulo, 05508-000, Brazil.

Accurate potential energy curves were constructed for a manifold of electronic states of the hydroxyl dication using a highly correlated electronic structure approach (SA-CASSCF/MRCI+Q/aug-cc-pV5Z). The existence of a bound (meta)stable ground state and bound low-lying states for OH2+ are ruled out, but do not exclude the possibility of its transient formation and dissociation along the repulsive ground state potential energy curve. Our results do not support the conclusion reported for the observation of OH2+ by electron ionization from ground state OH+. Read More

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Electromagnetic power of lightning superbolts from Earth to space.

Nat Commun 2021 Jun 11;12(1):3553. Epub 2021 Jun 11.

Météorage, Pau, France.

Lightning superbolts are the most powerful and rare lightning events with intense optical emission, first identified from space. Superbolt events occurred in 2010-2018 could be localized by extracting the high energy tail of the lightning stroke signals measured by the very low frequency ground stations of the World-Wide Lightning Location Network. Here, we report electromagnetic observations of superbolts from space using Van Allen Probes satellite measurements, and ground measurements, and with two events measured both from ground and space. Read More

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Magnetic Field Amplification by a Nonlinear Electron Streaming Instability.

Phys Rev Lett 2021 May;126(21):215101

SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.

Magnetic field amplification by relativistic streaming plasma instabilities is central to a wide variety of high-energy astrophysical environments as well as to laboratory scenarios associated with intense lasers and electron beams. We report on a new secondary nonlinear instability that arises for relativistic dilute electron beams after the saturation of the linear Weibel instability. This instability grows due to the transverse magnetic pressure associated with the beam current filaments, which cannot be quickly neutralized due to the inertia of background ions. Read More

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The first 5 years of gravitational-wave astrophysics.

Salvatore Vitale

Science 2021 06;372(6546)

Laser Interferometer Gravitational-Wave Observatory Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

Gravitational waves are ripples in spacetime generated by the acceleration of astrophysical objects; a direct consequence of general relativity, they were first directly observed in 2015. Here, I review the first 5 years of gravitational-wave detections. More than 50 gravitational-wave events have been found, emitted by pairs of merging compact objects such as neutron stars and black holes. Read More

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Photon bubble turbulence in cold atom gases.

Nat Commun 2021 May 28;12(1):3240. Epub 2021 May 28.

Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.

Turbulent radiation flow is commonplace in systems with strong, incoherent, light-matter interactions. In astrophysical contexts, photon bubble turbulence is considered a key mechanism behind enhanced radiation transport, and its importance has been widely asserted for a variety of high energy objects such as accretion disks and massive stars. Here, we show that analogous conditions to those of dense astrophysical objects can be obtained in large clouds of cold atoms, prepared in a laser-cooling experiment, driven close to a sharp electronic resonance. Read More

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Active Galactic Nuclei Jets as the Origin of Ultrahigh-Energy Cosmic Rays and Perspectives for the Detection of Astrophysical Source Neutrinos at EeV Energies.

Phys Rev Lett 2021 May;126(19):191101

DESY, Platanenallee 6, 15738 Zeuthen, Germany.

We demonstrate that a population of active galactic nuclei (AGN) can describe the observed spectrum of ultra-high-energy cosmic rays (UHECRs) at and above the ankle, and that the dominant contribution comes from low-luminosity BL Lacertae objects. An additional, subdominant contribution from high-luminosity AGN is needed to improve the description of the composition observables, leading to a substantial neutrino flux that peaks at exaelectronvolt (EeV) energies. We also find that different properties for the low- and high-luminosity AGN populations are required; a possibly similar baryonic loading can already be excluded from current IceCube Neutrino Observatory observations. Read More

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Searching for Axionlike Particles under Strong Gravitational Lenses.

Phys Rev Lett 2021 May;126(19):191102

Fakultät für Physik, Universität Bielefeld, Postfach 100131, 33501 Bielefeld, Germany.

We establish strong gravitational lens systems as robust probes of axionlike particles (ALPs)-a candidate for dark matter. A tiny interaction of photons with ALPs induces birefringence. Multiple images of gravitationally lensed polarized objects allow measurement of differential birefringence, alleviating systematics and astrophysical dependencies. Read More

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Evolution of Primordial Neutrino Helicities in Astrophysical Magnetic Fields and Implications for Their Detection.

Phys Rev Lett 2021 May;126(19):191803

Illinois Center for Advanced Studies of the Universe and Department of Physics, University of Illinois, 1110 West Green Street, Urbana, Illinois 61801, USA.

Since decoupling in the early Universe in helicity states, primordial neutrinos propagating in astrophysical magnetic fields precess and undergo helicity changes. In view of various experimental bounds allowing a large magnetic moment of neutrinos, we estimate the helicity flipping for relic neutrinos in both cosmic and galactic magnetic fields. The flipping probability is sensitive both to the neutrino magnetic moment and the structure of the magnetic fields and is a potential probe of the fields. Read More

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Computational Characterization of Astrophysical Species: The Case of Noble Gas Hydride Cations.

Front Chem 2021 11;9:664693. Epub 2021 May 11.

Department of Atomic, Molecular and Surface Processes (PAMS), Institute of Fundamental Physics (IFF-CSIC), CSIC, Madrid, Spain.

Theoretical-computational studies together with recent astronomical observations have shown that under extreme conditions in the interstellar medium (ISM), complexes of noble gases may be formed. Such observations have generated a wide range of possibilities. In order to identify new species containing such atoms, the present study gathers spectroscopic data for noble gas hydride cations, NgH (Ng = He, Ne, Ar) from high-level quantum chemistry computations, aiming to contribute in understanding the chemical bonding and electron sharing in these systems. Read More

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Conceptual Analogies Between Multi-Scale Feeding and Feedback Cycles in Supermassive Black Hole and Cancer Environments.

Front Oncol 2021 11;11:634818. Epub 2021 May 11.

Department of Specialistic Clinical and Odontostomatological Sciences, Polytechnic University of Marche, Ancona, Italy.

Adopting three physically-motivated scales ("micro" - "meso" - "macro", which refer to mpc - kpc - Mpc, respectively) is paramount for achieving a unified theory of multiphase active galactic nuclei feeding and feedback, and it represents a keystone for astrophysical simulations and observations in the upcoming years. In order to promote this multi-scale idea, we have decided to adopt an interdisciplinary approach, exploring the possible conceptual similarities between supermassive black hole feeding and feedback cycles and the dynamics occurring in human cancer microenvironment. Read More

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