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Susanne Pfalzner - One of the best experts on this subject based on the ideXlab platform.
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does the Mass Distribution in discs influence encounter induced losses in young star clusters
Astronomy and Astrophysics, 2014Co-Authors: M Steinhausen, Susanne PfalznerAbstract:Context. One mechanism for the external destruction of protoplanetary discs in young dense clusters is tidal disruption during the flyby of another cluster member. The degree of Mass loss in such an encounter depends, among other parameters, on the Distribution of the material within the disc. Previous work showed that this is especially so in encounters that truncate large parts of the outer disc. The expectation is that the number of completely destroyed discs in a cluster also depends on the Mass Distribution within the discs. Aims. Here we test this hypothesis by determining the influence of encounters on the disc fraction and average disc Mass in clusters of various stellar densities for di erent Mass Distributions in the discs. Methods. This is done by performing nbody6 simulations of a variety of cluster environments, where we track the encounter dynamics and determine the Mass loss due to these encounters for di erent disc-Mass Distributions. Results. We find that although the disc-Mass Distribution has a significant impact on the disc losses for specific star-disc encounters, the overall disc frequency generally remains una ected. The reason is that in single encounters the dependence on the Mass Distribution is strongest if both stars have very di erent Masses. Such encounters are rather infrequent in sparse clusters. In dense clusters these encounters are more common; however, here the disc frequency is largely determined by encounters between low-Mass stars such that the overall disc frequency does not change significantly. Conclusions. For tidal disruption the disc destruction in clusters is fairly independent of the actual Distribution of the material in the disc. The all determining factor remains the cluster density.
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does the Mass Distribution in discs influence encounter induced losses in young star clusters
arXiv: Astrophysics of Galaxies, 2014Co-Authors: M Steinhausen, Susanne PfalznerAbstract:One mechanism for the external destruction of protoplanetary discs in young dense clusters is tidal disruption during the flyby of another cluster member. The degree of Mass loss in such an encounter depends, among other parameters, on the Distribution of the material within the disc. Previous work showed that this is especially so in encounters that truncate large parts of the outer disc. The expectation is that the number of completely destroyed discs in a cluster depends also on the Mass Distribution within the discs. Here we test this hypothesis by determining the influence of encounters on the disc fraction and average disc Mass in clusters of various stellar densities for different Mass Distributions in the discs. This is done by performing Nbody6 simulation of a variety of cluster environments, where we track the encounter dynamics and determine the Mass loss due to these encounters for different disc-Mass Distributions. We find that although the disc Mass Distribution has a significant impact on the disc losses for specific star-disc encounters, the overall disc frequency generally remains rather unaffected. The reason is that in single encounters the dependence on the Mass Distribution is strongest if both stars have very different Masses. Such encounters are rather infrequent in sparse clusters. In dense clusters such encounters are more common, however, here the disc frequency is largely determined by encounters between low-Mass stars such that the overall disc frequency does not change significantly. For tidal disruption the disc destruction in clusters is fairly independent of the actual Distribution of the material in the disc. The all determining factor remains the cluster density.
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disc Mass Distribution in star disc encounters
Astronomy and Astrophysics, 2012Co-Authors: M Steinhausen, C Olczak, Susanne PfalznerAbstract:Aims. Investigations of stellar encounters in cluster environments have demonstrated their potential influence on the Mass and angular momentum of protoplanetary discs around young stars. We investigated how far the initial surface density in the disc surrounding a young star influences the outcome of an encounter. Methods. The numerical method applied here allows us to determine the Mass and angular momentum losses in an encounter for any initial disc-Mass Distribution. On the basis of a power-law ansatz for the surface density, Σ(r) ∝ r −p , we perform a parameter study of star-disc encounters with different initial disc-Mass Distributions using N-body simulations. Results. We demonstrate that the shape of the disc-Mass Distribution has a significant impact on the quantity of the disc-Mass and angular momentum losses in star-disc encounters. In particular, the results are most sensitive to how the outer parts of the disc are perturbed by high-Mass stars. In contrast, disc-penetrating encounters lead more or less independently of the disc-Mass Distribution always to large losses. However, maximum losses are generally obtained for initially flat distributed disc material. Based on a parameter study, a fit formula is derived, describing how the relative Mass and angular momentum loss depend on the initial disc-Mass Distribution index p. Encounters generally lead to a steepening of the density profile of the disc. The resulting profiles can have a r −2 -dependence or an even steeper one that is independent of the initial Distribution of the disc material. Conclusions. From observations, the initial density Distribution in discs remains unconstrained, hence the strong dependence on the initial density Distribution that we find here might require a revision of the effect of encounters in young stellar clusters. The steep surface density Distributions induced by some encounters might be a prerequisite to the formation of planetary systems similar to our own Solar System.
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Disc-Mass Distribution in star-disc encounters
Astronomy & Astrophysics, 2012Co-Authors: M Steinhausen, C Olczak, Susanne PfalznerAbstract:Investigations of stellar encounters in cluster environments have demonstrated their potential influence on the Mass and angular momentum of protoplanetary discs around young stars. In this study it is investigated in how far the initial surface density in the disc surrounding a young star influences the outcome of an encounter. Based on a power-law ansatz for the surface density, $\Sigma(r) \propto r^{-p}$, a parameter study of star-disc encounters with different initial disc-Mass Distributions has been performed using N-body simulations. It is demonstrated that the shape of the disc-Mass Distribution has a significant impact on the quantity of the disc-Mass and angular momentum losses in star-disc encounters. Most sensitive are the results where the outer parts of the disc are perturbed by high-Mass stars. By contrast, disc-penetrating encounters lead more or less independently of the disc-Mass Distribution always to large losses. However, maximum losses are generally obtained for initially flat distributed disc material. Based on the parameter study a fit formula is derived, describing the relative Mass and angular momentum loss dependent on the initial disc-Mass Distribution index p. Generally encounters lead to a steepening of the density profile of the disc. The resulting profiles can have a r^{-2}-dependence or even steeper independent of the initial Distribution of the disc material. From observations the initial density Distribution in discs remains unconstrained, so the here demonstrated strong dependence on the initial density Distribution might require a revision of the effect of encounters in young stellar clusters. The steep surface density Distributions induced by some encounters might be the prerequisite to form planetary systems similar to our own solar system.
M Steinhausen - One of the best experts on this subject based on the ideXlab platform.
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does the Mass Distribution in discs influence encounter induced losses in young star clusters
Astronomy and Astrophysics, 2014Co-Authors: M Steinhausen, Susanne PfalznerAbstract:Context. One mechanism for the external destruction of protoplanetary discs in young dense clusters is tidal disruption during the flyby of another cluster member. The degree of Mass loss in such an encounter depends, among other parameters, on the Distribution of the material within the disc. Previous work showed that this is especially so in encounters that truncate large parts of the outer disc. The expectation is that the number of completely destroyed discs in a cluster also depends on the Mass Distribution within the discs. Aims. Here we test this hypothesis by determining the influence of encounters on the disc fraction and average disc Mass in clusters of various stellar densities for di erent Mass Distributions in the discs. Methods. This is done by performing nbody6 simulations of a variety of cluster environments, where we track the encounter dynamics and determine the Mass loss due to these encounters for di erent disc-Mass Distributions. Results. We find that although the disc-Mass Distribution has a significant impact on the disc losses for specific star-disc encounters, the overall disc frequency generally remains una ected. The reason is that in single encounters the dependence on the Mass Distribution is strongest if both stars have very di erent Masses. Such encounters are rather infrequent in sparse clusters. In dense clusters these encounters are more common; however, here the disc frequency is largely determined by encounters between low-Mass stars such that the overall disc frequency does not change significantly. Conclusions. For tidal disruption the disc destruction in clusters is fairly independent of the actual Distribution of the material in the disc. The all determining factor remains the cluster density.
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does the Mass Distribution in discs influence encounter induced losses in young star clusters
arXiv: Astrophysics of Galaxies, 2014Co-Authors: M Steinhausen, Susanne PfalznerAbstract:One mechanism for the external destruction of protoplanetary discs in young dense clusters is tidal disruption during the flyby of another cluster member. The degree of Mass loss in such an encounter depends, among other parameters, on the Distribution of the material within the disc. Previous work showed that this is especially so in encounters that truncate large parts of the outer disc. The expectation is that the number of completely destroyed discs in a cluster depends also on the Mass Distribution within the discs. Here we test this hypothesis by determining the influence of encounters on the disc fraction and average disc Mass in clusters of various stellar densities for different Mass Distributions in the discs. This is done by performing Nbody6 simulation of a variety of cluster environments, where we track the encounter dynamics and determine the Mass loss due to these encounters for different disc-Mass Distributions. We find that although the disc Mass Distribution has a significant impact on the disc losses for specific star-disc encounters, the overall disc frequency generally remains rather unaffected. The reason is that in single encounters the dependence on the Mass Distribution is strongest if both stars have very different Masses. Such encounters are rather infrequent in sparse clusters. In dense clusters such encounters are more common, however, here the disc frequency is largely determined by encounters between low-Mass stars such that the overall disc frequency does not change significantly. For tidal disruption the disc destruction in clusters is fairly independent of the actual Distribution of the material in the disc. The all determining factor remains the cluster density.
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disc Mass Distribution in star disc encounters
Astronomy and Astrophysics, 2012Co-Authors: M Steinhausen, C Olczak, Susanne PfalznerAbstract:Aims. Investigations of stellar encounters in cluster environments have demonstrated their potential influence on the Mass and angular momentum of protoplanetary discs around young stars. We investigated how far the initial surface density in the disc surrounding a young star influences the outcome of an encounter. Methods. The numerical method applied here allows us to determine the Mass and angular momentum losses in an encounter for any initial disc-Mass Distribution. On the basis of a power-law ansatz for the surface density, Σ(r) ∝ r −p , we perform a parameter study of star-disc encounters with different initial disc-Mass Distributions using N-body simulations. Results. We demonstrate that the shape of the disc-Mass Distribution has a significant impact on the quantity of the disc-Mass and angular momentum losses in star-disc encounters. In particular, the results are most sensitive to how the outer parts of the disc are perturbed by high-Mass stars. In contrast, disc-penetrating encounters lead more or less independently of the disc-Mass Distribution always to large losses. However, maximum losses are generally obtained for initially flat distributed disc material. Based on a parameter study, a fit formula is derived, describing how the relative Mass and angular momentum loss depend on the initial disc-Mass Distribution index p. Encounters generally lead to a steepening of the density profile of the disc. The resulting profiles can have a r −2 -dependence or an even steeper one that is independent of the initial Distribution of the disc material. Conclusions. From observations, the initial density Distribution in discs remains unconstrained, hence the strong dependence on the initial density Distribution that we find here might require a revision of the effect of encounters in young stellar clusters. The steep surface density Distributions induced by some encounters might be a prerequisite to the formation of planetary systems similar to our own Solar System.
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Disc-Mass Distribution in star-disc encounters
Astronomy & Astrophysics, 2012Co-Authors: M Steinhausen, C Olczak, Susanne PfalznerAbstract:Investigations of stellar encounters in cluster environments have demonstrated their potential influence on the Mass and angular momentum of protoplanetary discs around young stars. In this study it is investigated in how far the initial surface density in the disc surrounding a young star influences the outcome of an encounter. Based on a power-law ansatz for the surface density, $\Sigma(r) \propto r^{-p}$, a parameter study of star-disc encounters with different initial disc-Mass Distributions has been performed using N-body simulations. It is demonstrated that the shape of the disc-Mass Distribution has a significant impact on the quantity of the disc-Mass and angular momentum losses in star-disc encounters. Most sensitive are the results where the outer parts of the disc are perturbed by high-Mass stars. By contrast, disc-penetrating encounters lead more or less independently of the disc-Mass Distribution always to large losses. However, maximum losses are generally obtained for initially flat distributed disc material. Based on the parameter study a fit formula is derived, describing the relative Mass and angular momentum loss dependent on the initial disc-Mass Distribution index p. Generally encounters lead to a steepening of the density profile of the disc. The resulting profiles can have a r^{-2}-dependence or even steeper independent of the initial Distribution of the disc material. From observations the initial density Distribution in discs remains unconstrained, so the here demonstrated strong dependence on the initial density Distribution might require a revision of the effect of encounters in young stellar clusters. The steep surface density Distributions induced by some encounters might be the prerequisite to form planetary systems similar to our own solar system.
C Olczak - One of the best experts on this subject based on the ideXlab platform.
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disc Mass Distribution in star disc encounters
Astronomy and Astrophysics, 2012Co-Authors: M Steinhausen, C Olczak, Susanne PfalznerAbstract:Aims. Investigations of stellar encounters in cluster environments have demonstrated their potential influence on the Mass and angular momentum of protoplanetary discs around young stars. We investigated how far the initial surface density in the disc surrounding a young star influences the outcome of an encounter. Methods. The numerical method applied here allows us to determine the Mass and angular momentum losses in an encounter for any initial disc-Mass Distribution. On the basis of a power-law ansatz for the surface density, Σ(r) ∝ r −p , we perform a parameter study of star-disc encounters with different initial disc-Mass Distributions using N-body simulations. Results. We demonstrate that the shape of the disc-Mass Distribution has a significant impact on the quantity of the disc-Mass and angular momentum losses in star-disc encounters. In particular, the results are most sensitive to how the outer parts of the disc are perturbed by high-Mass stars. In contrast, disc-penetrating encounters lead more or less independently of the disc-Mass Distribution always to large losses. However, maximum losses are generally obtained for initially flat distributed disc material. Based on a parameter study, a fit formula is derived, describing how the relative Mass and angular momentum loss depend on the initial disc-Mass Distribution index p. Encounters generally lead to a steepening of the density profile of the disc. The resulting profiles can have a r −2 -dependence or an even steeper one that is independent of the initial Distribution of the disc material. Conclusions. From observations, the initial density Distribution in discs remains unconstrained, hence the strong dependence on the initial density Distribution that we find here might require a revision of the effect of encounters in young stellar clusters. The steep surface density Distributions induced by some encounters might be a prerequisite to the formation of planetary systems similar to our own Solar System.
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Disc-Mass Distribution in star-disc encounters
Astronomy & Astrophysics, 2012Co-Authors: M Steinhausen, C Olczak, Susanne PfalznerAbstract:Investigations of stellar encounters in cluster environments have demonstrated their potential influence on the Mass and angular momentum of protoplanetary discs around young stars. In this study it is investigated in how far the initial surface density in the disc surrounding a young star influences the outcome of an encounter. Based on a power-law ansatz for the surface density, $\Sigma(r) \propto r^{-p}$, a parameter study of star-disc encounters with different initial disc-Mass Distributions has been performed using N-body simulations. It is demonstrated that the shape of the disc-Mass Distribution has a significant impact on the quantity of the disc-Mass and angular momentum losses in star-disc encounters. Most sensitive are the results where the outer parts of the disc are perturbed by high-Mass stars. By contrast, disc-penetrating encounters lead more or less independently of the disc-Mass Distribution always to large losses. However, maximum losses are generally obtained for initially flat distributed disc material. Based on the parameter study a fit formula is derived, describing the relative Mass and angular momentum loss dependent on the initial disc-Mass Distribution index p. Generally encounters lead to a steepening of the density profile of the disc. The resulting profiles can have a r^{-2}-dependence or even steeper independent of the initial Distribution of the disc material. From observations the initial density Distribution in discs remains unconstrained, so the here demonstrated strong dependence on the initial density Distribution might require a revision of the effect of encounters in young stellar clusters. The steep surface density Distributions induced by some encounters might be the prerequisite to form planetary systems similar to our own solar system.
Zhigang Wang - One of the best experts on this subject based on the ideXlab platform.
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another tetraquark structure in the π χc1 invariant Mass Distribution
European Physical Journal C, 2009Co-Authors: Zhigang WangAbstract:In this article, we assume that there exists a scalar hidden charm tetraquark state in the π + χ c1 invariant Mass Distribution, and we study its Mass using the QCD sum rules. The numerical result M Z =(4.36±0.18) GeV is consistent with the Mass of the Z(4250). The Z(4250) may be a tetraquark state, but other possibilities, such as a hadro-charmonium resonance and a \(D_{1}^{+}\bar{D}^{0}+D^{+}\bar{D}_{1}^{0}\) molecular state, are not excluded.
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possible tetraquark states in the π χc1 invariant Mass Distribution
European Physical Journal C, 2009Co-Authors: Zhigang WangAbstract:In this article, we assume that there exist hidden charmed tetraquark states with spin–parity JP=1−, and we calculate their Masses with the QCD sum rules. The numerical result indicates that the Masses of the vector hidden charmed tetraquark states are about MZ=(5.12±0.15) GeV or MZ=(5.16±0.16) GeV, which are inconsistent with the experimental data on the π+χc1 invariant-Mass Distribution. The hidden charmed mesons Z1, Z2 or Z may be scalar hidden charmed tetraquark states, hadro-charmonium resonances or molecular states.
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another tetraquark structure in the pi chi_ c1 invariant Mass Distribution
arXiv: High Energy Physics - Phenomenology, 2008Co-Authors: Zhigang WangAbstract:In this article, we assume that there exists a scalar hidden charm tetraquark state in the $\pi^+ \chi_{c1}$ invariant Mass Distribution, and study its Mass using the QCD sum rules. The numerical result $M_{Z}=(4.36\pm0.18) \rm{GeV}$ is consistent with the Mass of the Z(4250). The Z(4250) may be a tetraquark state, other possibilities, such as a hadro-charmonium resonance and a $D_1^+\bar{D}^0+ D^+\bar{D}_1^0$ molecular state are not excluded.
S E Thorsett - One of the best experts on this subject based on the ideXlab platform.
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the neutron star Mass Distribution
The Astrophysical Journal, 2013Co-Authors: B Kiziltan, Athanasios Kottas, Maria De Yoreo, S E ThorsettAbstract:In recent years, the number of pulsars with secure Mass measurements has increased to a level that allows us to probe the underlying neutron star (NS) Mass Distribution in detail. We critically review the radio pulsar Mass measurements. For the first time, we are able to analyze a sizable population of NSs with a flexible modeling approach that can effectively accommodate a skewed underlying Distribution and asymmetric measurement errors. We find that NSs that have evolved through different evolutionary paths reflect distinctive signatures through dissimilar Distribution peak and Mass cutoff values. NSs in double NS and NS-white dwarf (WD) systems show consistent respective peaks at 1.33 M and 1.55 M, suggesting significant Mass accretion (Δm 0.22 M) has occurred during the spin-up phase. The width of the Mass Distribution implied by double NS systems is indicative of a tight initial Mass function while the inferred Mass range is significantly wider for NSs that have gone through recycling. We find a Mass cutoff at 2.1 M for NSs with WD companions, which establishes a firm lower bound for the maximum NS Mass. This rules out the majority of strange quark and soft equation of state models as viable configurations for NS matter. The lack of truncation close to the maximum Mass cutoff along with the skewed nature of the inferred Mass Distribution both enforce the suggestion that the 2.1 M limit is set by evolutionary constraints rather than nuclear physics or general relativity, and the existence of rare superMassive NSs is possible. © 2013. The American Astronomical Society. All rights reserved..
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the neutron star Mass Distribution
arXiv: Solar and Stellar Astrophysics, 2013Co-Authors: B Kiziltan, Athanasios Kottas, S E ThorsettAbstract:In recent years, the number of pulsars with secure Mass measurements has increased to a level that allows us to probe the underlying neutron star Mass Distribution in detail. We critically review radio pulsar Mass measurements and present a detailed examination through which we are able to put stringent constraints on the underlying neutron star Mass Distribution. For the first time, we are able to analyze a sizable population of neutron star-white dwarf systems in addition to double neutron star systems with a technique that accounts for systematically different measurement errors. We find that neutron stars that have evolved through different evolutionary paths reflect distinctive signatures through dissimilar Distribution peak and Mass cutoff values. Neutron stars in double neutron star and neutron star-white dwarf systems show consistent respective peaks at 1.35 Msun and 1.50 Msun which suggest significant Mass accretion (Delta m~0.15 Msun) has occurred during the spin up phase. The width of the Mass Distribution implied by double neutron star systems is indicative of a tight initial Mass function while the inferred Mass range is significantly wider for neutron stars that have gone through recycling. We find a Mass cutoff at 2 Msun for neutron stars with white dwarf companions which establishes a firm lower bound for the maximum neutron star Mass. This rules out the majority of strange quark and soft equation of state models as viable configurations for neutron star matter. The lack of truncation close to the maximum Mass cutoff suggests that the 2 Msun limit is set by evolutionary constraints rather than nuclear physics or general relativity, and the existence of rare super-Massive neutron stars is possible.
