2,226 results match your criteria Astrophysical Bulletin[Journal]

Destructive Processing of Silicon Carbide Grains: Experimental Insights into the Formation of Interstellar Fullerenes and Carbon Nanotubes.

J Phys Chem A 2022 Jun 27. Epub 2022 Jun 27.

Departments of Astronomy and Chemistry, University of Arizona, Tucson, Arizona 85721, United States.

The detection of the fullerenes C and C in the interstellar medium (ISM) has transformed our understanding of chemical complexity in space. These discoveries also raise the possibility for the presence of even larger molecules in astrophysical environments. Here we report in situ heating of analog silicon carbide (SiC) presolar grains using transmission electron microscopy (TEM). Read More

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Adiabatic Waveforms from Extreme-Mass-Ratio Inspirals: An Analytical Approach.

Phys Rev Lett 2022 Jun;128(23):231101

Department of Physics, Kyoto University, Kyoto 606-8502, Japan.

Scientific analysis for the gravitational wave detector LISA will require theoretical waveforms from extreme-mass-ratio inspirals (EMRIs) that extensively cover all possible orbital and spin configurations around astrophysical Kerr black holes. However, on-the-fly calculations of these waveforms have not yet overcome the high dimensionality of the parameter space. To confront this challenge, we present a user-ready EMRI waveform model for generic (eccentric and inclined) orbits in Kerr spacetime, using an analytical self-force approach. Read More

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Supernovae and the Arrow of Time.

Entropy (Basel) 2022 Jun 14;24(6). Epub 2022 Jun 14.

Faculty of Engineering and Mathematical Sciences, Mathematics and Statistics, The University of Western Australia AUS, Perth 6907, Australia.

Supernovae are explosions of stars and are a central problem in astrophysics. Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities develop during the star's explosion and lead to intense interfacial RT/RM mixing of the star materials. We handle the mathematical challenges of the RT/RM problem based on the group theory approach. Read More

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Intrinsic disorder, extraterrestrial peptides, and prebiotic life on the earth.

J Biomol Struct Dyn 2022 Jun 20:1-5. Epub 2022 Jun 20.

Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, USA.

The discovery of mechanisms for the synthesis of homo-polymeric oligopeptides, such as polyglycine under conditions relevant to the astrophysical environment as well as in scenarios resembling primordial conditions that prevailed soon after Earth was formed, raises hopes in the search of extraterrestrial life. It also raises the possibility of extraterrestrial contribution to origin of life on Earth in the form of simple polypeptides. Bioinformatics analyses strongly predict such homo-polymeric peptides to be intrinsically disordered underscoring the potential involvement of IDPs in the origin of life which, even in its simplest form, could emerge spontaneously by autocatalysis of the primordial IDPs in self-organizing systems that evolved over time following natural selection. Read More

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Big Bang Nucleosynthesis Limits and Relic Gravitational-Wave Detection Prospects.

Phys Rev Lett 2022 Jun;128(22):221301

McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.

We revisit the big bang nucleosynthesis limits on primordial magnetic fields and/or turbulent motions accounting for the decaying nature of turbulent sources between the time of generation and big bang nucleosynthesis. This leads to larger estimates for the gravitational wave signal than previously expected. We address the detection prospects through space-based interferometers and pulsar timing arrays or astrometric missions for gravitational waves generated around the electroweak and quantum chromodynamics energy scale, respectively. Read More

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Time-dependent wave packet dynamics study of the resonances in the H + LiH( = 0, = 0) → Li + H reaction at low collision energies.

Phys Chem Chem Phys 2022 Jun 29;24(25):15532-15539. Epub 2022 Jun 29.

Key Laboratory of Materials Modification by Laser, Electron, and Ion Beams (Ministry of Education), School of Physics, Dalian University of Technology, Dalian 116024, P. R. China.

The depletion process of LiH by H collision plays an important role in the evolution of the early universe and astrophysical processes, including the eventual charge-states, abundances of atomic and molecular species and ensuing astrochemistry. Here, a quantum dynamics study on the H + LiH( = 0, = 0) → Li + H reaction is performed at the low collision energy range from 0.1 meV to 10 meV using the time-dependent wave packet method. Read More

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Exact law for compressible pressure-anisotropic magnetohydrodynamic turbulence: Toward linking energy cascade and instabilities.

P Simon F Sahraoui

Phys Rev E 2022 May;105(5-2):055111

Laboratoire de Physique des Plasmas (LPP), CNRS, Observatoire de Paris, Sorbonne Université, Université Paris-Saclay, École polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau, France.

We derive an exact law for compressible pressure-anisotropic magnetohydrodynamic turbulence. For a gyrotropic pressure tensor, we study the double-adiabatic case and show the presence of new flux and source terms in the exact law, reminiscent of the plasma instability conditions due to pressure anisotropy. The Hall term is shown to bring ion-scale corrections to the exact law without affecting explicitly the pressure terms. Read More

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Adsorption of C2-C5 alcohols on ice: A grand canonical Monte Carlo simulation study.

J Chem Phys 2022 Jun;156(22):224702

Department of Chemistry, Eszterházy Károly University, Leányka u. 6, H-3300 Eger, Hungary.

In this paper, we report grand canonical Monte Carlo simulations performed to characterize the adsorption of four linear alcohol molecules, comprising between two and five carbon atoms (namely, ethanol, n-propanol, n-butanol, and n-pentanol) on crystalline ice in a temperature range typical of the Earth's troposphere. The adsorption details analyzed at 228 K show that, at low coverage of the ice surface, the polar head of the adsorbed molecules tends to optimize its hydrogen bonding with the surrounding water, whereas the aliphatic chain lies more or less parallel to the ice surface. With increasing coverage, the lateral interactions between the adsorbed alcohol molecules lead to the reorientation of the aliphatic chains that tend to become perpendicular to the surface; the adsorbed molecules pointing thus their terminal methyl group up to the gas phase. Read More

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Three-dimensional network of filamentary currents and super-thermal electrons during magnetotail magnetic reconnection.

Nat Commun 2022 Jun 10;13(1):3241. Epub 2022 Jun 10.

CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Science, University of Science and Technology of China, Hefei, 230026, China.

Magnetic reconnection is a fundamental plasma process by which magnetic field lines on two sides of the current sheet flow inward to yield an X-line topology. It is responsible for producing energetic electrons in explosive phenomena in space, astrophysical, and laboratorial plasmas. The X-line region is supposed to be the important place for generating energetic electrons. Read More

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Constraining neutron-star matter with microscopic and macroscopic collisions.

Nature 2022 06 8;606(7913):276-280. Epub 2022 Jun 8.

Nikhef, Amsterdam, The Netherlands.

Interpreting high-energy, astrophysical phenomena, such as supernova explosions or neutron-star collisions, requires a robust understanding of matter at supranuclear densities. However, our knowledge about dense matter explored in the cores of neutron stars remains limited. Fortunately, dense matter is not probed only in astrophysical observations, but also in terrestrial heavy-ion collision experiments. Read More

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The Heliosphere and Local Interstellar Medium from Neutral Atom Observations at Energies Below 10 keV.

Space Sci Rev 2022 23;218(4):31. Epub 2022 May 23.

Department of Astrophysical Sciences, Princeton University, Princeton, NJ USA.

As the heliosphere moves through the surrounding interstellar medium, a fraction of the interstellar neutral helium, hydrogen, and heavier species crossing the heliopause make it to the inner heliosphere as neutral atoms with energies ranging from few eV to several hundred eV. In addition, energetic neutral hydrogen atoms originating from solar wind protons and from pick-up ions are created through charge-exchange with interstellar atoms. This review summarizes all observations of heliospheric energetic neutral atoms and interstellar neutrals at energies below 10 keV. Read More

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Water Attachment onto Size-Selected Cationic Pyrene Clusters.

J Phys Chem A 2022 Jun 7;126(23):3696-3707. Epub 2022 Jun 7.

Institut de Recherche en Astrophysique et Planétologie (IRAP), UMR5277, Université de Toulouse III - Paul Sabatier, CNRS, CNES, 9 avenue du Colonel Roche, F-31028 Toulouse, France.

We report measurements of the attachment rates of water molecules onto mass-selected cationic pyrene clusters for size from = 4 to 13 pyrene units and for different collision energies. Comparison of the attachment rates with the collision rates measured in collision-induced dissociation experiments provides access to the values of the sticking coefficient. The strong dependence of the attachment rates on size and collision energy is rationalized through a model in which we use a Langevin-type collision rate and adjust on experimental data the statistical dissociation rate of the water molecule from the cluster after attachment. Read More

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How Perturbative QCD Constrains the Equation of State at Neutron-Star Densities.

Phys Rev Lett 2022 May;128(20):202701

Faculty of Science and Technology, University of Stavanger, 4036 Stavanger, Norway.

We demonstrate in a general and analytic way how high-density information about the equation of state (EOS) of strongly interacting matter obtained using perturbative quantum chromodynamics constrains the same EOS at densities reachable in physical neutron stars. Our approach is based on utilizing the full information of the thermodynamic potentials at the high-density limit together with thermodynamic stability and causality. This requires considering the pressure as a function of chemical potential p(μ) instead of the commonly used pressure as a function of energy density p(ε). Read More

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Defining the temperature of an isolated molecule.

Mario Barbatti

J Chem Phys 2022 May;156(20):204304

Aix Marseille University, CNRS, ICR, Marseille, France and Institut Universitaire de France, 75231 Paris, France.

The microcanonical temperature of an isolated molecule is derived in terms of Boltzmann and Gibbs volume entropies within the quantum harmonic vibrational and equivalent degenerated model approximations. The effects of the entropy functional choice and various approximations are examined. The difference between Boltzmann and Gibbs volume temperatures is negligible for molecules bigger than ten atoms. Read More

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Unsaturated Dinitriles Formation Routes in Extraterrestrial Environments: A Combined Experimental and Theoretical Investigation of the Reaction between Cyano Radicals and Cyanoethene (CHCN).

J Phys Chem A 2022 Jun 31;126(22):3569-3582. Epub 2022 May 31.

Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy.

The reaction between cyano radicals (CN, XΣ) and cyanoethene (CHCN) has been investigated by a combined approach coupling crossed molecular beam (CMB) experiments with mass spectrometric detection and time-of-flight analysis at a collision energy of 44.6 kJ mol and electronic structure calculations to determine the relevant potential energy surface. The experimental results can be interpreted by assuming the occurrence of a dominant reaction pathway leading to the two but-2-enedinitrile (1,2-dicyanothene) isomers (- and -NC-CH═CH-CN) in a H-displacement channel and, to a much minor extent, to 1,1-dicyanoethene, CHC(CN). Read More

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Space Weathering: Processing Velocities in Organic Materials as a Function of Electron Beam Energies-Solar Electron Erosion Rate Application.

Astrobiology 2022 May 27. Epub 2022 May 27.

Van de Graaff Laboratory, Department of Physics, Pontifícia Universidade Católica do Rio de Janeiro (PUC-RIO), Rio de Janeiro, Brazil.

Samples of α-glycine (α-GLY; 230-350 nm) were irradiated in laboratory as a function of electron beam energies (0.25, 0.50, and 1. Read More

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Direct observations of anomalous resistivity and diffusion in collisionless plasma.

Nat Commun 2022 May 26;13(1):2954. Epub 2022 May 26.

Southwest Research Institute, San Antonio, TX, USA.

Coulomb collisions provide plasma resistivity and diffusion but in many low-density astrophysical plasmas such collisions between particles are extremely rare. Scattering of particles by electromagnetic waves can lower the plasma conductivity. Such anomalous resistivity due to wave-particle interactions could be crucial to many processes, including magnetic reconnection. Read More

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Super-resonant four-photon collinear laser frequency multiplication in plasma.

Phys Rev E 2022 Apr;105(4-2):045207

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

Resonant four-photon scattering could nearly double frequencies of intense laser pulses in plasma. However, transverse slippage between pulses presents a technological challenge, while collinear four-photon scattering is forbidden for classical light dispersion in plasma. Nonlinear renormalization of intense laser pulses can enable collinear four-photon resonance. Read More

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A trail of dark-matter-free galaxies from a bullet-dwarf collision.

Nature 2022 05 18;605(7910):435-439. Epub 2022 May 18.

Department of Physics and Astronomy, San José State University, San Jose, CA, USA.

The ultra-diffuse galaxies DF2 and DF4 in the NGC 1052 group share several unusual properties: they both have large sizes, rich populations of overluminous and large globular clusters, and very low velocity dispersions that indicate little or no dark matter. It has been suggested that these galaxies were formed in the aftermath of high-velocity collisions of gas-rich galaxies, events that resemble the collision that created the bullet cluster but on much smaller scales. The gas separates from the dark matter in the collision and subsequent star formation leads to the formation of one or more dark-matter-free galaxies. Read More

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Weakly Bound Complex Formation between HCN and CHCl: A Matrix-Isolation and Computational Study.

J Phys Chem A 2022 May 18;126(20):3110-3123. Epub 2022 May 18.

Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States.

The matrix-isolated infrared spectrum of a hydrogen cyanide-methyl chloride complex was investigated in a solid argon matrix. HCN and CHCl were co-condensed onto a substrate held at 10 K with an excess of argon gas, and the infrared spectrum was measured using Fourier-transform infrared spectroscopy. Quantum chemical geometry optimization, harmonic frequency, and natural bonding orbital calculations indicate stabilized hydrogen- and halogen-bonded structures. Read More

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In Situ Observations of Interstellar Pickup Ions from 1 au to the Outer Heliosphere.

Space Sci Rev 2022 9;218(4):28. Epub 2022 May 9.

Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 USA.

Interstellar pickup ions are an ubiquitous and thermodynamically important component of the solar wind plasma in the heliosphere. These PUIs are born from the ionization of the interstellar neutral gas, consisting of hydrogen, helium, and trace amounts of heavier elements, in the solar wind as the heliosphere moves through the local interstellar medium. As cold interstellar neutral atoms become ionized, they form an energetic ring beam distribution comoving with the solar wind. Read More

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Collision excitation of c-CH(XA) by He.

J Chem Phys 2022 May;156(18):184302

Departamento de Química y Física Teóricas, Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, Unidad Asociada GIFMAN, CSIC-UHU, Madrid 28006, Spain.

Accurate modeling of anionic abundances in the interstellar and circumstellar media requires calculations of collisional data with the most abundant species that are usually He atoms and H molecules. In this paper, we focus on smaller cyclic molecular anion, c-CH, an astrophysical candidate, following the detection of larger CH carbon chains. From a new three-dimensional potential energy surface, the rotational (de-)excitation of the c-CH(XA) anion by collision with He is investigated. Read More

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Rotational and Vibrational Spectra of the Pyridyl Radicals: A Coupled-Cluster Study.

J Phys Chem A 2022 May 13;126(20):3185-3197. Epub 2022 May 13.

Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States.

Pyridyl is a prototypical nitrogen-containing aromatic radical that may be a key intermediate in the formation of nitrogen-containing aromatic molecules under astrophysical conditions. On meteorites, a variety of complex molecules with nitrogen-containing rings have been detected with nonterrestrial isotopic abundances, and larger nitrogen-containing polycyclic aromatic hydrocarbons (PANHs) have been proposed to be responsible for certain unidentified infrared emission bands in the interstellar medium. In this work, the three isomers of pyridyl (2-, 3-, and 4-pyridyl) have been investigated with coupled cluster methods. Read More

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Laboratory IR Spectra of the Ionic Oxidized Fullerenes CO and COH.

J Phys Chem A 2022 May 9;126(19):2928-2935. Epub 2022 May 9.

Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525ED Nijmegen, The Netherlands.

We present the first experimental vibrational spectra of gaseous oxidized derivatives of C in protonated and radical cation forms, obtained through infrared multiple-photon dissociation spectroscopy using the FELIX free-electron laser. Neutral CO has two nearly iso-energetic isomers: the epoxide isomer in which the O atom bridges a CC bond that connects two six-membered rings and the annulene isomer in which the O atom inserts into a CC bond connecting a five- and a six-membered ring. To determine the isomer formed for CO in our experiment─a question that cannot be confidently answered on the basis of the DFT-computed stabilities alone─we compare our experimental IR spectra to vibrational spectra predicted by DFT calculations. Read More

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Measurement of Low-Energy Resonance Strengths in the ^{18}O(α,γ)^{22}Ne Reaction.

Phys Rev Lett 2022 Apr;128(16):162701

Department of Physics and The Joint Institute for Nuclear Astrophysics, University of Notre Dame, Notre Dame, Indiana 46556-5670, USA.

The ^{18}O(α,γ)^{22}Ne reaction is an essential part of a reaction chain that produces the ^{22}Ne(α,n)^{25}Mg neutron source for both the weak and main components of the slow neutron-capture process. At temperatures of stellar helium burning, the astrophysically relevant resonances in the ^{18}O(α,γ)^{22}Ne reaction that dominate the reaction rate occur at α particle energies E_{lab} of 472 and 569 keV. However, previous experiments have shown the strengths of these two resonances to be very weak, and only upper limits or partial resonance strengths could be obtained. Read More

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Spontaneous magnetization of collisionless plasma.

Proc Natl Acad Sci U S A 2022 May 5;119(19):e2119831119. Epub 2022 May 5.

Center for Integrated Plasma Studies, Physics Department, University of Colorado, Boulder, CO 80309.

SignificanceAstronomical observations indicate that dynamically important magnetic fields are ubiquitous in the Universe, while their origin remains a profound mystery. This work provides a paradigm for understanding the origin of cosmic magnetism by taking into account the effects of the microphysics of collisionless plasmas on macroscopic astrophysical processes. We demonstrate that the first magnetic fields can be spontaneously generated in the Universe by generic motions of astrophysical turbulence through kinetic plasma physics, and cosmic plasmas are thereby ubiquitously magnetized. Read More

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Collisional energy transfer in the CO-CO system.

Phys Chem Chem Phys 2022 May 18;24(19):11910-11918. Epub 2022 May 18.

LOMC - UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP 1123, F-76063 Le Havre, France.

An accurate determination of the physical conditions in astrophysical environments relies on the modeling of molecular spectra. In such environments, densities can be so low ( ≪ 10 cm) that local thermodynamical equilibrium conditions cannot be maintained. Hence, radiative and collisional properties of molecules are needed to correctly model molecular spectra. Read More

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Anomalous Cosmic Rays and Heliospheric Energetic Particles.

Space Sci Rev 2022 28;218(4):22. Epub 2022 Apr 28.

Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08540 USA.

We present a review of Anomalous Cosmic Rays (ACRs), including the history of their discovery and recent insights into their acceleration and transport in the heliosphere. We focus on a few selected topics including a discussion of mechanisms of their acceleration, escape from the heliosphere, their effects on the dynamics of the heliosheath, transport in the inner heliosphere, and their solar cycle dependence. A discussion concerning their name is also presented towards the end of the review. Read More

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Early Solar System instability triggered by dispersal of the gaseous disk.

Nature 2022 04 27;604(7907):643-646. Epub 2022 Apr 27.

Department of Earth and Environmental Sciences, Michigan State University, East Lansing, MI, USA.

The Solar System's orbital structure is thought to have been sculpted by an episode of dynamical instability among the giant planets. However, the instability trigger and timing have not been clearly established. Hydrodynamical modelling has shown that while the Sun's gaseous protoplanetary disk was present the giant planets migrated into a compact orbital configuration in a chain of resonances. Read More

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Super-strong magnetic field-dominated ion beam dynamics in focusing plasma devices.

Sci Rep 2022 Apr 27;12(1):6876. Epub 2022 Apr 27.

Institute of Laser Engineering, Osaka University, Suita, Japan.

High energy density physics is the field of physics dedicated to the study of matter and plasmas in extreme conditions of temperature, densities and pressures. It encompasses multiple disciplines such as material science, planetary science, laboratory and astrophysical plasma science. For the latter, high energy density states can be accompanied by extreme radiation environments and super-strong magnetic fields. Read More

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