Radiant Cooling Research Articles

輻射暖冷房設計法のための評価研究 : (1)床暖房方式の予熱特性

輻射暖冷房設計法のための評価研究 : (1)床暖房方式の予熱特性

Particle acceleration in an evolving active region by an ensemble of shock waves

view Abstract Citations (23) References (63) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Particle Acceleration in an Evolving Active Region by an Ensemble of Shock Waves Anastasiadis, Anastasios ; Vlahos, Loukas Abstract We present a model for the acceleration and transport of energetic particles (electrons and ions) inside an active region. We propose that the agent for the acceleration is an ensemble of oblique shock waves, generated inside an evolving and constantly changing active region. The acceleration is based on the 'shock drift' mechanism, using the adiabatic treatment. The high-energy particles are losing energy via Coulomb collisions and radiation. We calculate the energy distribution of the particles, their acceleration time, and their maximum energy as a function of the number of shock waves present. The high-energy particles are transported inside a chaotic magnetic field and are reflected randomly when they meet a magnetic mirror point. Finally we compare our numerical results with the observations. Publication: The Astrophysical Journal Pub Date: June 1994 DOI: 10.1086/174290 Bibcode: 1994ApJ...428..819A Keywords: Astronomical Models; Energy Distribution; Particle Acceleration; Particle Energy; Shock Waves; Solar Flares; Solar Radiation; Transportation; Adiabatic Conditions; Coulomb Collisions; Electric Fields; Magnetic Fields; Magnetohydrodynamics; Numerical Analysis; Radiant Cooling; Astronomy; ACCELERATION OF PARTICLES; SHOCK WAVES; SUN: CORONA; SUN: FLARES; SUN: MAGNETIC FIELDS full text sources ADS |

A young, glitching pulsar near the direction of W28

view Abstract Citations (68) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Young, Glitching Pulsar near the Direction of W28 Kaspi, V. M. ; Lyne, A. G. ; Manchester, R. N. ; Johnston, S. ; D'Amico, N. ; Shemar, S. L. Abstract Timing observations of PSR B1758-23 (PSR J1801-23) made over a 6 yr period using the 64-m Parkes radio telescope and the 76-m Lovell radio telescope show that this pulsar is young and is located close to the edge of the supernova remnant W28. The pulsar's characteristic age of 58,000 yr is consistent with the estimated remnant age, but the large observed dispersion of the pulsar signal is difficult to reconcile with the independently estimated remnant distance. PSR B1758-23 has glitched three times during our observations, in keeping with the trend of high glitch activity in younger pulsars. Publication: The Astrophysical Journal Pub Date: June 1993 DOI: 10.1086/186859 Bibcode: 1993ApJ...409L..57K Keywords: Pulsars; Radio Sources (Astronomy); Radio Telescopes; Supernova Remnants; Electron Energy; Energetic Particles; Radiant Cooling; Astrophysics; ISM: SUPERNOVA REMNANTS; ISM: INDIVIDUAL ALPHANUMERIC: W28; STARS: INDIVIDUAL ALPHANUMERIC: PSR B1758-23 full text sources ADS | data products SIMBAD (7)

Formation of the circumstellar shell around SN 1987A

view Abstract Citations (145) References (50) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Formation of the Circumstellar Shell around SN 1987A Blondin, John M. ; Lundqvist, Peter Abstract The nebulosity within a few arcseconds from SN 1987A has been modeled in terms of the supernova progenitor's fast wind interacting with a slow, asymmetric, previously emitted red supergiant wind. Previous models have relied on the assumption that the shocked blue supergiant wind is isobaric. We show that this approximation is unsatisfactory, and present two-dimensional time-dependent hydrodynamic calculations of the colliding winds model. From adiabatic models it is found that a ratio of equatorial to polar mass-loss rate during the red supergiant stage of at least ~20 is needed to explain the observed structure. It is shown that not only this ratio, but also the form of polar dependence on asymmetry, is important to the formation of a compact ring structure. Models are also presented in which radiative cooling of the shocked red supergiant wind is included and, at early times, also radiative cooling of the shocked blue supergiant wind. Cooling acts to lower the expansion velocity and to increase filamentation. We arrive at a viable colliding winds model for the formation of the circumstellar structure around SN 1987A consisting of a red supergiant wind with a velocity of 5 km s^-1^ and a mass-loss rate of 2 x 10^-5^ M_sun_ yr^-1^, and a blue supergiant wind with a velocity of 300 km s^-1^ and mass-loss rate of 3 x 10^-7^ M_sun_ yr^-1^. This model can explain the low expansion velocity and high density of the ring, as well as the compact ring structure and the morphology of the extended lobes. For the model to be successful, roughly 50% of the red supergiant wind mass is collimated with 10^deg^ from the equatorial plane. Such a strong collimation may indicate that the supernova progenitor had a binary companion. Finally, we discuss the implications of the hydrodynamic models in the context of the observed radio emission and high-resolution optical observations. Subject headings- circumstellar matter - hydrodynamics - stars: individual (SN 1987A) - supernovae : individual (SN 1987A) Publication: The Astrophysical Journal Pub Date: March 1993 DOI: 10.1086/172366 Bibcode: 1993ApJ...405..337B Keywords: Stellar Envelopes; Stellar Models; Stellar Winds; Supernova 1987a; Hydrodynamics; Radiant Cooling; Supergiant Stars; Astrophysics full text sources ADS | data products NED (2) SIMBAD (1)

The structure of shocks with thermal conduction and radiative cooling

view Abstract Citations (13) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Structure of Shocks with Thermal Conduction and Radiative Cooling Lacey, Cedric G. Abstract A general analysis is presented of the structure of a steady state, plane-parallel shock wave in which both thermal conduction and radiative cooling are important. The fluid is assumed to have a perfect-gas equation of state, with radiative cooling a function only of its temperature and density. Conduction in both diffusive and saturated regimes is treated. For the case of a strong shock, with conductivity and cooling function varying as power laws in temperature, approximate analytic solutions describing the shock wave are derived. For a plasma of solar composition, conduction is found to have a significant effect on the shock temperature and overall thickness of the postshock layer only for shock velocities greater than about 30,000 km/s, corresponding to shock temperatures greater than about 10 to the 10th K, but it affects the local structure of parts of the shock wave at much lower velocities. The effects of conduction are greatly enhanced if the heavy-element abundance is increased. Publication: The Astrophysical Journal Pub Date: March 1988 DOI: 10.1086/166136 Bibcode: 1988ApJ...326..769L Keywords: Conductive Heat Transfer; Cosmic Plasma; Magnetohydrodynamics; Radiant Cooling; Shock Waves; Steady Flow; Dimensionless Numbers; Heat Flux; One Dimensional Flow; Parallel Flow; Plasma Physics; HYDRODYNAMICS; SHOCK WAVES full text sources ADS |

Hydrogen molecules and the radiative cooling of pregalactic shocks

view Abstract Citations (337) References (76) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hydrogen Molecules and the Radiative Cooling of Pregalactic Shocks Shapiro, Paul R. ; Kang, Hyesung Abstract The nonequilibrium radiative cooling, recombination, and molecule formation behind steady state shock waves in a gas of primordial composition have been calculated in detail for a number of cases. The authors have solved the rate equations for these processes, together with the hydrodynamical conservation equations. Such shock waves are relevant to a wide range of theories of galaxy and pregalactic star formation. A purely atomic gas of H and He which is shock-heated to temperatures above 104K is assumed. The results indicate that formation of H2 molecules in the post-shock gas may be quite common for a significant range of shock velocities. The extra cooling resulting from H2 formation greatly reduces previous estimates of the characteristic gravitational scale length and the characteristic mass subject to gravitational instability in these postshock regions. Publication: The Astrophysical Journal Pub Date: July 1987 DOI: 10.1086/165350 Bibcode: 1987ApJ...318...32S Keywords: Cooling Flows (Astrophysics); Galactic Evolution; Hydrogen Clouds; Molecular Clouds; Radiant Cooling; Shock Waves; Boundary Value Problems; Computational Astrophysics; Intergalactic Media; Nonequilibrium Conditions; Scaling Laws; Star Formation; Astrophysics; GALAXIES: FORMATION; INTERGALACTIC MEDIUM; MOLECULAR PROCESSES; SHOCK WAVES full text sources ADS |

Cooling shells and galaxy formation in the early universe

view Abstract Citations (26) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Cooling shells and galaxy formation in the early universe Wandel, A. Abstract The expansion cooling and instability of explosions in the intergalactic medium of the early universe are investigated theoretically in the explosive-amplification model of Ostriker and Cowie (1981), taking radiative-transfer, Compton, radiative, and molecular processes into account. The importance of radiative cooling in the inverse-Compton era and the impossibility of explosions cooling to the temperature of the background radiation are demonstrated. A model is proposed in which molecular (H2) cooling produces equilibrium temperatures of about (3170/sq rt z) K, amplification and gravitational instability occur for explosions of seed masses above 10 to the 9th solar mass, and rapid cooling of supernovae precludes galactic-scale explosions at redshifts in excess of 60, but in which shells of (1-10) x 10 to the 13th solar mass can be produced at redshifts of 10 or less and fragment to galactic-scale masses. Publication: The Astrophysical Journal Pub Date: July 1985 DOI: 10.1086/163306 Bibcode: 1985ApJ...294..385W Keywords: Astronomical Models; Background Radiation; Cosmology; Galactic Evolution; Intergalactic Media; Radiant Cooling; Compton Effect; Explosions; Gravitational Collapse; Molecular Clouds; Red Shift; Shock Heating; Supernovae; Astrophysics full text sources ADS |

Black hole accretion disks - Coronal stabilization of the Lightman-Eardley instability

view Abstract Citations (35) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Black hole accretion disks - Coronal stabilization of the Lightman-Eardley instability Ionson, J. A. ; Kuperus, M. Abstract Physical processes by which the presence of a corona around a black hole can raise the threshold of onset of the Lightman-Eardley (L-E, 1976) instability are explored analytically. The L-E model predicts that an optically thick disk becomes unstable when the disk radiation pressure exceeds the disk gas pressure. The model has important implications for the validity of either the coronal disk or two-temperature disk models for accretion zones around black holes. It is shown that a corona can dissipate accreting gravitational energy through radiative cooling. Specific ratios of hard/soft X-rays are quantified for stable and unstable conditions. X-ray spectra from Cyg X-1 are cited as residing below the instability threshold value and thus are supportive of the coronal disk model. Publication: The Astrophysical Journal Pub Date: September 1984 DOI: 10.1086/162418 Bibcode: 1984ApJ...284..389I Keywords: Accretion Disks; Astronomical Models; Black Holes (Astronomy); Magnetohydrodynamic Stability; Stellar Coronas; Stellar Gravitation; Energy Dissipation; Radiant Cooling; Stellar Mass Accretion; X Ray Spectra; Astrophysics full text sources ADS |

Galactic absorption line coronae

view Abstract Citations (23) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Galactic absorption line coronae Bregman, J. N. Abstract Models are developed to determine if gaseous coronas around galaxies give rise to the absorption systems in quasar spectra. A two-dimensional hydrodynamic code with radiative cooling is used to study the dynamics and thermodynamics of a corona, and the position and rate at which clouds form. Coronal gas is found to rise from an extended gaseous disk in two models with base coronal temperatures of 10 to the 6th K and 0.50 x 10 to the 6th K. Column densities of 10 to the 19th sq cm out to a radius of 7 kcp are also achieved with a total gas mass of 2.0 x 10 to the 9th and 1.7 x 10 to the 9th solar masses, respectively. The velocity structure of the model absorption line systems may be reproduced, and clouds in pressure equilibrium with the hot coronas have densities consistent with basic observational and theoretical restrictions. Publication: The Astrophysical Journal Pub Date: November 1981 DOI: 10.1086/159343 Bibcode: 1981ApJ...250....7B Keywords: Absorption Spectra; Astronomical Models; Coronas; Galactic Structure; Quasars; Disk Galaxies; Gas Density; High Temperature Gases; Line Spectra; Radiant Cooling; Astrophysics full text sources ADS |

A class of analytic solutions for the thermally balanced magnetostatic prominence sheet

view Abstract Citations (29) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A class of analytic solutions for the thermally balanced magnetostatic prominence sheet Low, B. C. ; Wu, S. T. Abstract A theoretical study is presented for the nonlinear interplay between magnetostatic equilibrium and energy balance in a Kippenhahn-Schlueter type solar prominence sheet. A class of theoretical models is presented, expressed in closed analytic forms, thus facilitating the direct illustration of the nonlinear physical properties. The model couples the equilibrium between magnetic field, plasma pressure, and weight on the one hand, with the balance between a rho-squared T radiative loss, a rho wave heating (where rho equals plasma density, and T equals plasma temperature), and thermal conduction channeled along magnetic field lines on the other. The steady solutions are divided into three classes, and are characterized by the total wave heating in the prominence sheet which is greater than, equal to, or less than the total radiative loss. The compaction of the plasma along the field lines, under its own weight, and the energy transport effects determine which of the three basic behaviors obtains in a particular situation. A discussion is presented of the implications of the steady solutions for the formation of prominences. Publication: The Astrophysical Journal Pub Date: August 1981 DOI: 10.1086/159158 Bibcode: 1981ApJ...248..335L Keywords: Magnetohydrodynamics; Magnetostatic Fields; Plasma Layers; Plasma-Electromagnetic Interaction; Solar Prominences; Thermodynamic Equilibrium; Beta Factor; Plasma Conductivity; Plasma Heating; Plasma Pressure; Plasma Waves; Radiant Cooling; Temperature Distribution; Thermal Conductivity; Solar Physics full text sources ADS |

X-ray emission from M87 - A pressure confined cooling atmosphere surrounding a low mass galaxy

view Abstract Citations (114) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-ray emission from M87 - A pressure confined cooling atmosphere surrounding a low mass galaxy Binney, J. ; Cowie, L. L. Abstract A conventional model for the mass of the galaxy M87 (500-billion solar masses) is used to show that a radiative cooling flow agrees well with spectroscopically derived mass flow rates (10 solar masses per year) and surface brightness profiles of X-ray emission around the galaxy. A temperature of 100-million K, and a density of a few x 10 to the -4th/cu cm are obtained without the use of a massive halo. The atmosphere contains 1-trillion solar masses of gas, with a temperature profile increasing outward and gas acting as a reservoir for the flow. The present models indicate that thermal conductivity in M87 is less than 0.002 of its classical value, and does not significantly affect properties of the surrounding gas. Publication: The Astrophysical Journal Pub Date: July 1981 DOI: 10.1086/159055 Bibcode: 1981ApJ...247..464B Keywords: Cooling Flows (Astrophysics); Cosmic Gases; Galactic Radiation; Galactic Structure; X Ray Sources; Brightness; Gas Density; Gas Flow; Gas Temperature; Halos; Mass; Mass Flow Rate; Radiant Cooling; Thermal Conductivity; Astrophysics full text sources ADS | data products NED (1)

Molecular cooling and thermal balance of dense interstellar clouds

view Abstract Citations (509) References (65) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Molecular cooling and thermal balance of dense interstellar clouds. Goldsmith, P. F. ; Langer, W. D. Abstract The role of molecular cooling in establishing the temperature of the gas in dense interstellar clouds is examined. Attention is given to the cooling produced by a number of molecules, each of which is representative of different types in terms of abundances, level spacings, transition strengths, and cross sections. Molecular hydrogen densities in the range from 100 to 1 million per cu cm and kinetic temperatures between 10 and 60 K are considered, radiative transfer is calculated on the basis of the velocity-gradient model, and best estimates of the fractional abundance of species important for cooling are used to construct total cooling curves at each kinetic temperature. The contributions of several possible heating sources are evaluated, including heating by cosmic rays, H2 formation on grains, gravitational contraction, collisions with warm dust grains, and magnetic ion-neutral slip. Rates for each process are derived and equated with the cooling rate to obtain equilibrium temperature-density relations in a number of cases. The results are applied in a general discussion about the thermal properties of dense interstellar clouds without internal stellar or protostellar heat sources. Publication: The Astrophysical Journal Pub Date: June 1978 DOI: 10.1086/156206 Bibcode: 1978ApJ...222..881G Keywords: Heat Balance; Hydrogen Clouds; Interstellar Matter; Radiant Cooling; Radiative Transfer; Cosmic Rays; Gas Density; Gas Temperature; Protostars; Astrophysics; Interstellar Clouds:Cooling full text sources ADS |

Photoelectric heating of interstellar gas

view Abstract Citations (1244) References (78) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photoelectric heating of interstellar gas. Draine, B. T. Abstract Photoelectric emission from interstellar grains and its consequences for the heating and cooling of interstellar gas are reexamined. The physics of photoemission is briefly reviewed, the photoemissive properties of interstellar grains are examined, and the absorption efficiency and total geometric cross section of the grains are estimated. Some aspects of gas-grain interactions are considered, the interstellar UV energy density is discussed, and the grain potential and heating rate are evaluated for the interstellar UV background as well as for a wide range of electron densities and temperatures. Steady-state solutions for the gas are obtained, and their relevance to the interstellar medium is briefly assessed. The time-dependent cooling of a fossil H II region is analyzed, and it is suggested that fossil H II in the wakes of runaway O stars can produce significant amounts of intermediate-temperature (about 500 to 3000 K) H I. It is concluded that: (1) interstellar grains are likely to have effective photoelectric thresholds of approximately 8 eV and (2) photoemission from grains is a major contributor to the heating of the cool phase of the interstellar medium. Publication: The Astrophysical Journal Supplement Series Pub Date: April 1978 DOI: 10.1086/190513 Bibcode: 1978ApJS...36..595D Keywords: Gas Heating; Interstellar Gas; Photoelectric Emission; Radiant Cooling; Cations; Gas Ionization; Gas Temperature; H Ii Regions; Scaling Laws; Spiral Galaxies; Steady State; Time Dependence; Ultraviolet Radiation; Astrophysics; Grains:Interstellar Matter; Interstellar Gas: Heating full text sources ADS |

Gas in globular clusters. II - Time-dependent flow models

view Abstract Citations (41) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Gas in globular clusters. II. Time-dependent flow models. Vandenberg, D. A. ; Faulkner, D. J. Abstract A numerical method is described for solving the time-dependent flow equations of relevance to gas flows in globular clusters. This method involves a modification of Henyey's iteration technique as well as finite-difference approximations for mass, momentum, and energy conservation. As an initial application of the numerical method, a previous study is extended to low gas-input energies in order to determine the fate of gas in clusters of one million solar masses when radiative cooling prevents the occurrence of steady-state outflows. Evolutionary sequences of models are presented for selected values of a parameter corresponding to the energy of the gas ejected by a star itself, and the resulting unsteady winds are shown to be similar to those computed by Mathews and Baker (1971) for elliptical galaxies. The results indicate that accumulation of mostly neutral hydrogen may take place in a region of small dimensions near the center of the most tightly bound globular clusters. Publication: The Astrophysical Journal Pub Date: December 1977 DOI: 10.1086/155695 Bibcode: 1977ApJ...218..415V Keywords: Astronomical Models; Gas Flow; Globular Clusters; Interstellar Gas; Stellar Mass Ejection; Time Dependence; Boundary Value Problems; Dynamic Models; Finite Difference Theory; Hydrodynamic Equations; Iterative Solution; Radiant Cooling; Astrophysics full text sources ADS |

Time-dependent radiative cooling of a hot, diffuse cosmic gas, and the emergent X-ray spectrum

view Abstract Citations (257) References (58) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Time-dependent radiative cooling of a hot, diffuse cosmic gas, and the emergent X-ray spectrum. Shapiro, P. R. ; Moore, R. T. Abstract A new, detailed calculation is presented of the nonequilibrium radiative cooling of an optically thin low-density (n < lO cm-3) interstellar gas which is suddenly shock-heated to 106 K and cools to 1O K. Results include the ionization structure, radiative energy-loss, and X-ray spectrum from 0.5 to 70 A for the cooling gas under a variety of initial conditions. It is found that the initial condition of the gas is unimportant only if the gas is preionized. These results are relevant to the diffuse galactic soft X-ray background at 0.25 keV, the observation by Copernicus of interstellar 0 vi, and studies of the late radiative phase of supernova remnants. Subject headings: interstellar: matter - nebulae: supernova remnants - X-rays: general Publication: The Astrophysical Journal Pub Date: July 1976 DOI: 10.1086/154515 Bibcode: 1976ApJ...207..460S Keywords: Gas Cooling; Interstellar Gas; Radiant Cooling; Shock Heating; X Ray Spectra; High Temperature Plasmas; Nonequilibrium Conditions; Oxygen Spectra; Rarefied Gases; Supernova Remnants; Temperature Distribution; Astrophysics full text sources ADS |

Thermal X-rays from stellar flares - Reevaluation of scaling from solar flares

view Abstract Citations (39) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Thermal X-rays from stellar flares: reevaluation of scaling from solar flares. Mullan, D. J. Abstract A simple method of estimating the ratio of thermal X-ray luminosity to optical luminosity in stellar flares is presented which is valid at times close to and following peak flare luminosity. It is proposed that at such times, the X-ray and optical luminosities are, respectively, the energy radiated by the plasma and the energy conducted out of the plasma. If the conductive energy directed downward toward the photosphere and lower chromosphere is regarded as the energy source for optical flares, then the luminosity ratio is equal to the ratio of conductive to radiative cooling times in the hot flare plasma. A self-consistent model for red-dwarf flares is discussed in which the decay time of the optical light curve is controlled by the time scale for thermal conduction from the hot flare plasma. The condition that the two times must be approximately equal leads to estimates of electron densities in flares, provided the flare temperatures are known; it is argued that stellar flare temperatures are 1 to 4 times higher than the mean temperature of solar flares. Numerical results are given for the luminosity ratio in flares of seven UV Ceti stars. It is concluded that if the solar luminosity ratio is used in attempting to predict thermal X-ray fluxes from stellar flares, the predicted X-ray flux accompanying an optical flare of given amplitude will provide only an upper limit on the actual thermal X-ray flux. Publication: The Astrophysical Journal Pub Date: July 1976 DOI: 10.1086/154492 Bibcode: 1976ApJ...207..289M Keywords: Energy Dissipation; High Temperature Plasmas; Light Curve; Solar Flares; Solar X-Rays; Stellar Flares; Stellar Luminosity; Convective Heat Transfer; Dwarf Stars; Numerical Analysis; Radiant Cooling; Stellar Models; Stellar Radiation; Stellar Temperature; X Ray Astronomy; Space Radiation full text sources ADS |

Rapidly rotating stars with optically thin stellar winds

view Abstract Citations (33) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Rapidly rotating stars with optically thin stellar winds. Marlborough, J. M. ; Zamir, M. Abstract The analysis of Cassinelli and Castor, concerning the role of the radiation field in the heating, cooling, and transfer of momentum to the atmospheres of early-type stars, is extended to the case of rapidly rotating stars in general, and of Be stars in particular. The general equations for steady flow are presented and the solution discussed for flow in the equatorial plane and in the region near the pole under the assumptions of an optically thin wind and radially streaming radiation. Limiting values for the ratio of velocity of escape to mean thermal speed at the sonic point are obtained if transonic flow is to occur. The observational evidence presently available is considered and is shown to support the theoretical predictions. Publication: The Astrophysical Journal Pub Date: January 1975 DOI: 10.1086/153314 Bibcode: 1975ApJ...195..145M Keywords: B Stars; Early Stars; Optical Thickness; Radiation Effects; Stellar Rotation; Stellar Winds; Electron Scattering; Far Ultraviolet Radiation; Momentum Transfer; O Stars; Radiant Cooling; Transonic Flow; Ultraviolet Spectra; Astrophysics full text sources ADS |

Optically thin radiating shock waves and the formation of density inhomogeneities

view Abstract Citations (57) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Optically thin radiating shock waves and the formation of density inhomogeneities. Chevalier, R. A. ; Theys, J. C. Abstract It is found that the gas flow behind a perturbed, optically thin, radiating shock front tends to create density clumps. A two-dimensional hydrodynamic code is used to follow the shock created by an explosion. The shock is perturbed by a density fluctuation in the ambient medium. The growth of clumps is greatest near the time when radiative cooling first becomes significant. After a clump has formed, it tends to move ahead of the parent shock front due to its large momentum. The magnitude of the density enhancement is approximately proportional to the magnitude of the perturbing fluctuation. The results are discussed, with particular attention to the shock fronts in supernova remnants. Publication: The Astrophysical Journal Pub Date: January 1975 DOI: 10.1086/153303 Bibcode: 1975ApJ...195...53C Keywords: Density Distribution; Gas Flow; Optical Thickness; Shock Fronts; Supernova Remnants; Absorption Spectra; Astronomical Models; Flow Distribution; Hydrodynamic Equations; Radiant Cooling; Shock Waves; Astrophysics full text sources ADS |

Formation of molecules on small interstellar grains

view Abstract Citations (82) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Formation of molecules on small interstellar grains. Allen, M. ; Robinson, G. W. Abstract A model is proposed for the formation of molecules on small interstellar grains. It is suggested that the energy liberated when a chemical bond is formed between two atoms on a grain is transferred to the lattice vibrations of the grain, heating up the grain. The 'hot' grain, during the time that it is radiatively recooling, may then liberate its adsorbed volatiles. The time scales for molecular desorption from a grain are calculated for OH and CO for four different grain compositions. The results provide some tentative explanations of astronomical observations. Publication: The Astrophysical Journal Pub Date: January 1975 DOI: 10.1086/153306 Bibcode: 1975ApJ...195...81A Keywords: Astronomical Models; Interstellar Matter; Radiant Cooling; Carbon Monoxide; Chemical Bonds; Chemical Reactions; Desorption; Energy Dissipation; Hydroxyl Emission; Astrophysics full text sources ADS |

X-ray emission from vibrating white dwarfs

view Abstract Citations (16) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-ray emission from vibrating white dwarfs. Katz, J. I. ; Salpeter, E. E. Abstract It had been proposed previously that regularly pulsating X-ray sources (Cen X-3 and Her X-1) may be the result of vibrating white dwarfs sending shock waves into their atmospheres. We investigate the hydrodynamics and X-ray production of such objects. The relevant parameters are discussed, and detailed numerical calculations are carried out for a series of cases. The results depend very strongly on whether the parameter values are physically realizable or not. The photospheric radiation flux cools hot atmospheric material by Compton recoil. For physically reasonable amplitudes of oscillation a mismatch between the stellar oscillation and the acoustic response of the atmosphere makes energy coupling to the atmosphere very inefficient. These two effects lead to multi-keV X-ray powers many orders of magnitude too low to explain the observations, in disagreement with earlier work. Publication: The Astrophysical Journal Pub Date: October 1974 DOI: 10.1086/153178 Bibcode: 1974ApJ...193..429K Keywords: Pulsed Radiation; Radiant Cooling; Stellar Atmospheres; Thermal Radiation; White Dwarf Stars; X Ray Sources; Astronomical Models; Atmospheric Temperature; Compton Effect; Hydrodynamics; Photosphere; Radiant Flux Density; Shock Waves; Astrophysics full text sources ADS |