Stellar interactions in dense and sparse star clusters

Olczak, C.; Pfalzner, Susanne; Eckart, A.

doi:10.1051/0004-6361/200912641

Cited by 44 publications

(99 citation statements)

References 67 publications

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“…So the disc-destroying encounters most probably have quite low mass ratios in this environment. This is in accordance with the results of Olczak et al (2010). They found that in clusters of higher density than the ONC the lowmass stars dominate the encounter history, leading to lower encounter mass ratios.…”

Section: Appendix A: Properties Of Disc-destroying Encounterssupporting

confidence: 92%

“…Olczak et al 2010;. Before studying this effect on the disc size in an entire star cluster, we first study the influence of a fly-by on a single star-disc system.…”

Section: Resultsmentioning

confidence: 99%

“…This was achieved by performing Nbody6 simulations (Aarseth 1973(Aarseth , 2003Spurzem 1999) similar to those of Olczak et al (2008Olczak et al ( , 2010, and . In those simulations, the stellar encounters in the clusters were tracked and their effect on protoplanetary discs was analysed in the diagnostics using a previously performed parameter study.…”

Section: Methodsmentioning

confidence: 99%

“…The surface density there is much flatter with Σ ∝ r −0.5 . To obtain this flat profile after 1 Myr of simulation time, which is the assumed age of the ONC, Hillenbrand (1997) and Olczak et al (2010), for instance, used the threedimensional initial number density distribution…”

Section: Cluster Simulationsmentioning

confidence: 99%

“…Johnstone et al 1998;Störzer & Hollenbach 1999;Scally & Clarke 2002;Matsuyama et al 2003;Johnstone et al 2004;Adams et al 2006;Alexander et al 2006;Ercolano et al 2008;Gorti & Hollenbach 2009;Drake et al 2009) and stellar fly-bys or gravitational stripping (see e.g. Clarke & Pringle 1993;Scally & Clarke 2002;Pfalzner 2004;Adams et al 2006;Olczak et al 2006Olczak et al , 2010Pfalzner & Olczak 2007;Craig & Krumholz 2013;Rosotti et al 2014). From observations, the sizes of protoplanetary discs are usually determined by fitting the spectral energy distributions (SEDs) to disc models using a truncated power-law (Andrews & Williams 2007).…”

Section: Introductionmentioning

confidence: 99%

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Strong effect of the cluster environment on the size of protoplanetary discs?

Vincke

Breslau

Pfalzner

2015

A&A

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Context. Most stars are born in clusters, thus the protoplanetary discs surrounding the newly formed stars might be influenced by this environment. Isolated star-disc encounters have previously been studied, and it was shown that very close encounters are necessary to completely destroy discs. However, relatively distant encounters are still able to change the disc size considerably. Aims. We quantify the importance of disc-size reduction that is due to stellar encounters in an entire stellar population. Methods. We modelled young, massive clusters of different densities using the code Nbody6 to determine the statistics of stellar encounter parameters. In a second step, we used these parameters to investigate the effect of the environments on the disc size. For this purpose, we performed a numerical experiment with an artificial initial disc size of 10 5 AU. Results. We quantify to which degree the disc size is more sensitive to the cluster environment than to the disc mass or frequency. We show that in all investigated clusters a large portion of discs is significantly reduced in size. After 5 Myr, the fraction of discs smaller than 1000 AU in ONC-like clusters with an average number density of ρ cluster ∼ 60 pc −3 , the fraction of discs smaller than 1000 AU is 65%, while discs smaller than 100 AU make up 15%. These fractions increase to 84% and 39% for discs in denser clusters like IC 348 (ρ cluster ∼ 500 pc −3 ). Even in clusters with a density four times lower than in the ONC (ρ cluster ∼ 15 pc −3 ), about 43% of all discs are reduced to sizes below 1000 AU and roughly 9% to sizes below 100 AU. Conclusions. For any disc in the ONC that initially was larger than 1000 AU, the probability to be truncated to smaller disc sizes as a result of stellar encounters is quite high. Thus, among other effects, encounters are important in shaping discs and potentially forming planetary systems in stellar clusters.

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Section: Appendix A: Properties Of Disc-destroying Encounterssupporting

confidence: 92%

“…Olczak et al 2010;. Before studying this effect on the disc size in an entire star cluster, we first study the influence of a fly-by on a single star-disc system.…”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Cluster Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Strong effect of the cluster environment on the size of protoplanetary discs?

Vincke

Breslau

Pfalzner

2015

A&A

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Stripping a debris disk by close stellar encounters in an open stellar cluster

Lestrade

Morey

Lassus

et al. 2011

A&A

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A debris disk is a constituent of any planetary system surrounding a main sequence star. We study whether close stellar encounters can disrupt and strip a debris disk of its planetesimals in the expanding open cluster of its birth with a decreasing star number density over 100 Myr. Such stripping would affect the dust production and hence detectability of the disk. We tabulated the fractions of planetesimals stripped off during stellar flybys of miss distances between 100 and 1000 AU and for several mass ratios of the central to passing stars. We then estimated the numbers of close stellar encounters over the lifetime of several expanding open clusters characterized by their initial star densities. We found that a standard disk, with inner and outer radii of 40 and 100 AU, suffers no loss of planetesimals over 100 Myr around a star born in a common embedded cluster with star density ≤1000 pc −3 . In contrast, we found that such a disk is severely depleted of its planetesimals around a star born in an Orion-type cluster where the star density is >20 000 pc −3 . In this environment, a disk loses >97% of its planetesimals around an M-dwarf, >63% around a solar-type star, and >42% around an A-dwarf, over 100 Myr. We roughly estimate that two-thirds of the stars may be born in such high star density clusters. This might explain in part why fewer debris disks are observed around lower mass stars.

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Evolution of the binary population in young dense star clusters

Kaczmarek

Olczak

Pfalzner

2011

A&A

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Context. Field stars are not always single stars, but can often be found in bound double systems. Since binary frequencies in the birth places of stars, young embedded clusters, are sometimes even higher than on average the question arises of how binary stars form in young dense star clusters and how their properties evolve to those observed in the field population. Aims. We assess, the influence of stellar dynamical interactions on the primordial binary population in young dense cluster environments. Methods. We perform numerical N-body simulations of the Orion nebula cluster like star cluster models including primordial binary populations using the simulation code nbody6 ++ . Results. We find two remarkable results that have yet not been reported: The first is that the evolution of the binary frequency in young dense star clusters is independent predictably of its initial value. The time evolution of the normalized number of binary systems has a fundamental shape. The second main result is that the mass of the primary star is of vital importance to the evolution of the binary. The more massive a primary star, the lower the probability that the binary is destroyed by gravitational interactions. This results in a higher binary frequency for stars more massive than 2 M compared to the binary frequency of lower mass stars. The observed increase in the binary frequency with primary mass is therefore most likely not due to differences in the formation process but can be entirely explained as a dynamical effect. Conclusions. Our results allow us to draw conclusions about the past and the future number of binary systems in young dense star clusters and demonstrate that the present field stellar population has been influenced significantly by its natal environments.

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Stellar interactions in dense and sparse star clusters

Cited by 44 publications

References 67 publications

Strong effect of the cluster environment on the size of protoplanetary discs?

Strong effect of the cluster environment on the size of protoplanetary discs?

Stripping a debris disk by close stellar encounters in an open stellar cluster

Evolution of the binary population in young dense star clusters

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