scholarly journals Thermal history modelling of the L chondrite parent body

2019 ◽  
Vol 628 ◽  
pp. A77
Author(s):  
Hans-Peter Gail ◽  
Mario Trieloff
Keyword(s):  
Cooling Rate ◽  
Error Bounds ◽  
Empirical Data ◽  
Thermal Evolution ◽  
Theoretical Models ◽  
Parent Body ◽  
Evolution Model ◽  
Formation Time ◽  
Rate Data ◽  
Eutectic Melting

Context. The cooling history of individual meteorites can be reconstructed if closure temperatures and closure ages of different radioisotopic chronometers are available for a couple of meteorites. If a close similarity in chemical and isotopic composition suggests a common origin from the same parent body, some basic properties of this body can be derived. Aims. The radius of the L chondrite parent body, its formation time, and its evolution history are determined by fitting theoretical models to empirical data of radioisotopic chronometers for L chondrites. Methods. A simplified evolution model for the L chondrite parent body was constructed considering sintering of the initially porous material, temperature dependent heat conductivity, and an insulating regolith layer. Such models were fitted to thermochronological data of five meteorites for which precise data for the Hf-W and U-Pb-Pb thermochronometers have been published. Results. A set of parameters for the L chondrite parent body is found that yields excellent agreement (within error bounds) between a thermal evolution model and thermochonological data of five examined L chondrites. Empirical cooling rate data also agree with the model results within error bounds such that there is no conflict between cooling rate data and the onion-shell model. Two models are found to be compatible with the presently available empirical data: one model with a radius of 115 km and a formation time of 1.89 Ma after CAI formation, and another model with 160 km radius and formation time of 1.835 Ma. The central temperature of the smaller body remains well below the Ni,Fe-FeS eutectic melting temperature and is consistent with the apparent non-existence of primitive achondrites related to the L chondrites. For the bigger model, incipient melting in the central core region is predicted, which opens the possibility that primitive achondrites related to L chondrites could be found.

scholarly journals Dynamics of nanodust particles emitted from elongated initial orbits

2018 ◽  
Vol 617 ◽  
pp. A43 ◽  
Author(s):  
A. Czechowski ◽  
I. Mann
Keyword(s):  
Solar Wind ◽  
Numerical Solutions ◽  
Equations Of Motion ◽  
Dust Cloud ◽  
Theoretical Models ◽  
Ecliptic Plane ◽  
Parent Body ◽  
The Sun ◽  
Trapping Region ◽  
Eccentric Orbits

Context. Because of high charge-to-mass ratio, the nanodust dynamics near the Sun is determined by interplay between the gravity and the electromagnetic forces. Depending on the point where it was created, a nanodust particle can either be trapped in a non-Keplerian orbit, or escape away from the Sun, reaching large velocity. The main source of nanodust is collisional fragmentation of larger dust grains, moving in approximately circular orbits inside the circumsolar dust cloud. Nanodust can also be released from cometary bodies, with highly elongated orbits. Aims. We use numerical simulations and theoretical models to study the dynamics of nanodust particles released from the parent bodies moving in elongated orbits around the Sun. We attempt to find out whether these particles can contribute to the trapped nanodust population. Methods. We use two methods: the motion of nanodust is described either by numerical solutions of full equations of motion, or by a two-dimensional (heliocentric distance vs. radial velocity) model based on the guiding-center approximation. Three models of the solar wind are employed, with different velocity profiles. Poynting–Robertson and the ion drag are included. Results. We find that the nanodust emitted from highly eccentric orbits with large aphelium distance, like those of sungrazing comets, is unlikely to be trapped. Some nanodust particles emitted from the inbound branch of such orbits can approach the Sun to within much shorter distances than the perihelium of the parent body. Unless destroyed by sublimation or other processes, these particles ultimately escape away from the Sun. Nanodust from highly eccentric orbits can be trapped if the orbits are contained within the boundary of the trapping region (for orbits close to ecliptic plane, within ~0.16 AU from the Sun). Particles that avoid trapping escape to large distances, gaining velocities comparable to that of the solar wind.

scholarly journals Thermal evolution and quiescent emission of transiently accreting neutron stars

2019 ◽  
Vol 629 ◽  
pp. A88 ◽  
Author(s):  
A. Y. Potekhin ◽  
A. I. Chugunov ◽  
G. Chabrier
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Nuclear Reactions ◽  
Thermal Evolution ◽  
Theoretical Models ◽  
Equilibrium Temperature ◽  
Theoretical Interpretation ◽  
Quasi Equilibrium ◽  
Accretion Rates

Aims. We study the long-term thermal evolution of neutron stars in soft X-ray transients (SXTs), taking the deep crustal heating into account consistently with the changes of the composition of the crust. We collect observational estimates of average accretion rates and thermal luminosities of such neutron stars and compare the theory with observations. Methods. We performed simulations of thermal evolution of accreting neutron stars, considering the gradual replacement of the original nonaccreted crust by the reprocessed accreted matter, the neutrino and photon energy losses, and the deep crustal heating due to nuclear reactions in the accreted crust. We also tested and compared results for different modern theoretical models. We updated a compilation of the observational estimates of the thermal luminosities in quiescence and average accretion rates in the SXTs and compared the observational estimates with the theoretical results. Results. The long-term thermal evolution of transiently accreting neutron stars is nonmonotonic. The quasi-equilibrium temperature in quiescence reaches a minimum and then increases toward the final steady state. The quasi-equilibrium thermal luminosity of a neutron star in an SXT can be substantially lower at the minimum than in the final state. This enlarges the range of possibilities for theoretical interpretation of observations of such neutron stars. The updates of the theory and observations leave the previous conclusions unchanged, namely that the direct Urca process operates in relatively cold neutron stars and that an accreted heat-blanketing envelope is likely present in relatively hot neutron stars in the SXTs in quiescence. The results of the comparison of theory with observations favor suppression of the triplet pairing type of nucleon superfluidity in the neutron-star matter.

scholarly journals The effect of diffusive nuclear burning in neutron star envelopes on cooling in accreting systems

2020 ◽  
Vol 493 (4) ◽  
pp. 4936-4944
Author(s):  
M J P Wijngaarden ◽  
Wynn C G Ho ◽  
Philip Chang ◽  
Dany Page ◽  
Rudy Wijnands ◽  
...  
Keyword(s):  
Neutron Star ◽  
Thermal Evolution ◽  
Theoretical Models ◽  
Light Elements ◽  
Heating Source ◽  
Total Luminosity ◽  
Deep Interior ◽  
Nuclear Burning ◽  
Short Time ◽  
Over Time

ABSTRACT Valuable information about the neutron star (NS) interior can be obtained by comparing observations of thermal radiation from a cooling NS crust with theoretical models. Nuclear burning of lighter elements that diffuse to deeper layers of the envelope can alter the relation between surface and interior temperatures and can change the chemical composition over time. We calculate new temperature relations and consider two effects of diffusive nuclear burning (DNB) for H–C envelopes. First, we consider the effect of a changing envelope composition and find that hydrogen is consumed on short time-scales and our temperature evolution simulations correspond to those of a hydrogen-poor envelope within ∼100 d. The transition from a hydrogen-rich to a hydrogen-poor envelope is potentially observable in accreting NS systems as an additional initial decline in surface temperature at early times after the outburst. Second, we find that DNB can produce a non-negligible heat flux, such that the total luminosity can be dominated by DNB in the envelope rather than heat from the deep interior. However, without continual accretion, heating by DNB in H–C envelopes is only relevant for <1–80 d after the end of an accretion outburst, as the amount of light elements is rapidly depleted. Comparison to crust cooling data shows that DNB does not remove the need for an additional shallow heating source. We conclude that solving the time-dependent equations of the burning region in the envelope self-consistently in thermal evolution models instead of using static temperature relations would be valuable in future cooling studies.

scholarly journals Two generations of exsolution lamellae in pyroxene from Asuka 09545: Clues to the thermal evolution of silicates in mesosiderite

2019 ◽  
Vol 104 (11) ◽  
pp. 1663-1672
Author(s):  
Lidia Pittarello ◽  
Seann McKibbin ◽  
Akira Yamaguchi ◽  
Gang Ji ◽  
Dominique Schryvers ◽  
...  
Keyword(s):  
Thermal Evolution ◽  
Parent Body ◽  
Cooling History ◽  
Equilibrium Conditions ◽  
Slow Cooling ◽  
Temperature Range ◽  
Fine Grained ◽  
Two Generations ◽  
Mantle Component ◽  
The Antarctic

Abstract Mesosiderite meteorites consist of a mixture of crustal basaltic or gabbroic material and metal. Their formation process is still debated due to their unexpected combination of crust and core materials, possibly derived from the same planetesimal parent body, and lacking an intervening mantle component. Mesosiderites have experienced an extremely slow cooling rate from ca. 550 °C, as recorded in the metal (0.25–0.5 °C/Ma). Here we present a detailed investigation of exsolution features in pyroxene from the Antarctic mesosiderite Asuka (A) 09545. Geothermobarometry calculations, lattice parameters, lamellae orientation, and the presence of clinoenstatite as the host were used in an attempt to constrain the evolution of pyroxene from 1150 to 570 °C and the formation of two generations of exsolution lamellae. After pigeonite crystallization at ca. 1150 °C, the first exsolution process generated the thick augite lamellae along (100) in the temperature interval 1000–900 °C. By further cooling, a second order of exsolution lamellae formed within augite along (001), consisting of monoclinic low-Ca pyroxene, equilibrated in the temperature range 900–800 °C. The last process, occurring in the 600–500 °C temperature range, was likely the inversion of high to low pigeonite in the host crystal, lacking evidence for nucleation of orthopyroxene. The formation of two generations of exsolution lamellae, as well as of likely metastable pigeonite, suggest non-equilibrium conditions. Cooling was sufficiently slow to allow the formation of the lamellae, their preservation, and the transition from high to low pigeonite. In addition, the preservation of such fine-grained lamellae limits long-lasting, impact reheating to a peak temperature lower than 570 °C. These features, including the presence of monoclinic low-Ca pyroxene as the host, are reported in only a few mesosiderites. This suggests a possibly different origin and thermal history from most mesosiderites and that the crystallography (i.e., space group) of low-Ca pyroxene could be used as parameter to distinguish mesosiderite populations based on their cooling history.

The antiretroviral rollout and drug-resistant HIV in Africa: insights from empirical data and theoretical models

AIDS ◽  
2005 ◽  
Vol 19 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Sally Blower ◽  
Erin Bodine ◽  
James Kahn ◽  
Willi McFarland
Keyword(s):  
Empirical Data ◽  
Theoretical Models ◽  
Drug Resistant

Thermal evolution model for the H chondrite asteroid-instantaneous formation versus protracted accretion

Icarus ◽  
2013 ◽  
Vol 226 (1) ◽  
pp. 212-228 ◽  
Author(s):  
S. Henke ◽  
H.-P. Gail ◽  
M. Trieloff ◽  
W.H. Schwarz
Keyword(s):  
Thermal Evolution ◽  
Evolution Model

Empirical data and theoretical models

2004 ◽  
Vol 12 (2) ◽  
pp. 375-388 ◽  
Author(s):  
Edda Weigand
Keyword(s):  
Empirical Data ◽  
Theoretical Models

scholarly journals Innovation of Thermal Evolution Model of Mantle

2010 ◽  
Vol 119 (6) ◽  
pp. 1215-1227 ◽  
Author(s):  
Hiroki SENSHU ◽  
Shigenori MARUYAMA ◽  
Shuji RINO
Keyword(s):  
Thermal Evolution ◽  
Evolution Model

scholarly journals Crack-Depth Prediction in Steel Based on Cooling Rate

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
M. Rodríguez-Martín ◽  
S. Lagüela ◽  
D. González-Aguilera ◽  
P. Rodríguez-Gonzálvez
Keyword(s):  
3D Reconstruction ◽  
Cooling Rate ◽  
Infrared Thermography ◽  
Crack Depth ◽  
Rate Data ◽  
Reconstruction Procedure ◽  
Depth Prediction ◽  
Active Infrared Thermography ◽  
Real Geometry ◽  
Steel Welds

One criterion for the evaluation of surface cracks in steel welds is to analyze the depth of the crack, because it is an effective indicator of its potential risk. This paper proposes a new methodology to obtain an accurate crack-depth prediction model based on the combination of infrared thermography and the 3D reconstruction procedure. In order to do this, a study of the cooling rate of the steel is implemented through active infrared thermography, allowing the study of the differential thermal behavior of the steel in the fissured zone with respect to the nonfissured zone. These cooling rate data are correlated with the real geometry of the crack, which is obtained with the 3D reconstruction of the welds through a macrophotogrammetric procedure. In this way, it is possible to analyze the correlation between cooling rate and depth through the different zones of the crack. The results of the study allow the establishment of an accurate predictive depth model which enables the study of the depth of the crack using only the cooling rate data. In this way, the remote measure of the depth of the surface steel crack based on thermography is possible.

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