scholarly journals N-body Simulations of Star Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 187-188
Author(s):  
Peter Anders ◽  
Henny J. G. L. M. Lamers ◽  
Holger Baumgardt
Keyword(s):  
Mass Loss ◽  
Star Clusters ◽  
List Type ◽  
Type Number ◽  
Body Studies ◽  
Mass Segregation

AbstractTwo aspects of our recent N-body studies of star clusters are presented: 1)What impact does mass segregation and selective mass loss have on integrated photometry?2)How well do results compare from N-body simulations using NBODY4 and STARLAB/KIRA?

scholarly journals Dynamics and variability of winds from single Wolf-Rayet stars

1999 ◽  
Vol 193 ◽  
pp. 157-167
Author(s):  
Stanley P. Owocki ◽  
Kenneth G. Gayley
Keyword(s):  
Mass Loss ◽  
Multiple Scattering ◽  
Optical Depth ◽  
Spectral Distribution ◽  
Radiation Flux ◽  
Emission Lines ◽  
List Type ◽  
Type Number ◽  
Ob Stars ◽  
Realistic Line

We review the dynamics of winds from single Wolf-Rayet stars, with emphasis on the following specific points: (a)The classical “momentum problem” (to explain the large inferred ratio of wind to radiative momentum, η Mv∞/(L/c) ≫ 1) is in principle readily solved through multiple scattering of radiation by an opacity that is sufficiently “gray” in its spectral distribution. In this case, one simply obtains η ≃ τ, where τ is the wind optical depth;(b)Lines with a Poisson spectral distribution yield an “effectively gray” cumulative opacity, with multi-line scattering occuring when the velocity separation between thick lines Δv is less than the wind terminal speed v∞. In this case, one obtains η ≃ v∞/Δv;(c)However, realistic line lists are not gray, and leakage through gaps in the line spectral distribution tends to limit the effective scattering to η ≲ 1;(d)In WR winds, ionization stratification helps spread line-bunches and so fill in gaps, allowing for more effective global trapping of radiation, and thus η > 1;(e)However, photon thermalization can reduce the local effectiveness of line-driving near the stellar core, making it difficult for radiation alone to initiate the wind;(f)The relative complexity of WR wind initiation may be associated with the extensive turbulent structure inferred from observed variabililty in WR wind emission lines;(g)Overall, the understanding of WR winds is perhaps best viewed as an “opacity problem”, i.e., identifying the enhanced opacity that can adequately block the radiation flux throughout the wind, and thus drive a WR mass loss that is much greater than from OB stars of comparable luminosity.

scholarly journals Observations of Mass Loss from OB and Wolf-Rayet Stars

1982 ◽  
Vol 99 ◽  
pp. 149-172 ◽  
Author(s):  
M. J. Barlow
Keyword(s):  
Mass Loss ◽  
List Type ◽  
Type Number ◽  
Loss Rates

In this review, three observationally accessible parameters of the winds of OB and Wolf-Rayet stars will be discussed: (1)Terminal velocities(2)Velocity laws(3)Mass loss rates

scholarly journals On the Properties of Wolf-Rayet Stars and Their Mass Loss

1982 ◽  
Vol 99 ◽  
pp. 203-207
Author(s):  
N. Panagia ◽  
M. Felli
Keyword(s):  
Mass Loss ◽  
Multiple Scattering ◽  
Radiation Temperature ◽  
List Type ◽  
Type Number ◽  
Lyman Continuum ◽  
Stellar Radiation ◽  
Total Luminosity ◽  
Continuous Radiation ◽  
Photospheric Radius

From consideration of the observed properties of the envelopes produced by mass loss in WR stars we find that: a)The velocity at the optical photosphere is in the range 200–800 km sb)The effective photospheric radius for the continuous radiation capable to ionize helium twice (γ < 228 A) is typically 5 to 15 times the optical photospheric radius.c)The radiation temperature in the Lyman continuum (γ < 912 Å) is around 5 × 104K. Therefore, most of the stellar radiation is emitted in the far UV and the total luminosity is considerably higher than currently estimated.d)Multiple scattering (N ≃ 20) of radiation in the interval 228–504 Å can provide most of the momentum needed to accelerate the wind up to the observed terminal velocities.

scholarly journals Mass Loss from Astronomical Objects; A Summary

1983 ◽  
Vol 6 ◽  
pp. 603-606
Author(s):  
C. de Jager
Keyword(s):  
Interstellar Medium ◽  
Mass Loss ◽  
Stellar Mass ◽  
Future Research ◽  
List Type ◽  
Type Number ◽  
Loss Data

AbstractIn this summary of the Joint Discussion on mass loss I discuss successively:(1)stellar mass loss data and possible mechanisms(2)mass loss for special types of stars and suggestions for future research in the stellar case(3)interaction with the interstellar medium(4)mass loss from quasars

scholarly journals Plinian eruptions à la Eta Carinae

1989 ◽  
Vol 113 ◽  
pp. 101-108
Author(s):  
Kris Davidson
Keyword(s):  
Surface Temperature ◽  
Mass Loss ◽  
List Type ◽  
Surface Material ◽  
Type Number ◽  
Bipolar Structure ◽  
Eta Carinae ◽  
Critical Range ◽  
Loss Event ◽  
Eddington Limit

Eta Carinae is at once ourmost notableLBV but also adoubtfulLBV, because its Great Eruption observed 150 years ago was so unique. Since that event exceeded other major LBV outbursts by orders of magnitude in ejected mass and energy, we are not certain that it really was an example of S Dor, P Cyg, R127-type behavior. But even if it turns out to be a freak,ηCar has provided either the original example or one of the earliest hints for several facets of the LBV phenomenon,e.g.:--Visual-wavelength brightening with little change in luminosity during each major mass-loss event;--The idea of a modified Eddington limit causing instability in a critical range of surface temperature;--CNO-processed surface material;--Bipolar structure in the ejecta.

scholarly journals Is Coma a Young Aggregate of Old Subclusters?

1988 ◽  
Vol 130 ◽  
pp. 535-535
Author(s):  
Y. Mellier ◽  
G. Mathez ◽  
A. Mazure
Keyword(s):  
List Type ◽  
Type Number ◽  
Dynamical Friction ◽  
Stage Scheme ◽  
Gravitational Systems ◽  
Mass Segregation ◽  
Stage 1

Evolution of gravitational systems is currently believed to follow a 3-stage scheme: Stage 1: Subclusters form first ouring violent relaxationStage 2: Dynamical friction mass segregationStage 3: contraction of core, expansion of halo

scholarly journals Dynamical Evolution of Mass-Segregated Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 181-185
Author(s):  
Enrico Vesperini ◽  
Steve McMillan ◽  
Simon Portegies Zwart
Keyword(s):  
Mass Loss ◽  
Density Profile ◽  
Stellar Evolution ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Evolution ◽  
Stellar Initial Mass Function ◽  
Mass Segregation

AbstractWe present the results of a survey of N-body simulations aimed at exploring the implications of primordial mass segregation on the dynamical evolution of star clusters. We show that, in a mass-segregated cluster, the effect of early mass loss due to stellar evolution is, in general, more destructive than for an unsegregated cluster with the same density profile and leads to shorter lifetimes, a faster initial evolution toward less concentrated structure and flattening of the stellar initial mass function.

scholarly journals Evolution of single stars with mass loss

1979 ◽  
Vol 83 ◽  
pp. 312-336 ◽  
Author(s):  
C. de Loore
Keyword(s):  
Mass Loss ◽  
Indirect Evidence ◽  
List Type ◽  
Type Number ◽  
Radio Observations

A.Mass loss has been observed by means of UV, optical, IR and radio observations.B.There exists also indirect evidence that stars lose matter during their evolution.

Solar Corona Investigation by the Coronal Line Photometer at Lomnický Peak

1994 ◽  
Vol 144 ◽  
pp. 431-434
Author(s):  
M. Minarovjech ◽  
M. Rybanský
Keyword(s):  
Solar Corona ◽  
Time Resolution ◽  
Active Regions ◽  
High Time ◽  
High Time Resolution ◽  
List Type ◽  
Type Number ◽  
Coronal Line ◽  
Global Cycle

AbstractThis paper deals with a possibility to use the ground-based method of observation in order to solve basic problems connected with the solar corona research. Namely:1.heating of the solar corona2.course of the global cycle in the corona3.rotation of the solar corona and development of active regions.There is stressed a possibility of high-time resolution of the coronal line photometer at Lomnický Peak coronal station, and use of the latter to obtain crucial observations.

The LDE-Type Flare Occurrence (1969-1993)

1994 ◽  
Vol 144 ◽  
pp. 279-282
Author(s):  
A. Antalová
Keyword(s):  
Time Series ◽  
Fourier Analysis ◽  
Sunspot Cycle ◽  
List Type ◽  
Type Number ◽  
Solar Cycles ◽  
Type Iv ◽  
Long Duration ◽  
Cycle Maximum ◽  
Flare Index

AbstractThe occurrence of LDE-type flares in the last three cycles has been investigated. The Fourier analysis spectrum was calculated for the time series of the LDE-type flare occurrence during the 20-th, the 21-st and the rising part of the 22-nd cycle. LDE-type flares (Long Duration Events in SXR) are associated with the interplanetary protons (SEP and STIP as well), energized coronal archs and radio type IV emission. Generally, in all the cycles considered, LDE-type flares mainly originated during a 6-year interval of the respective cycle (2 years before and 4 years after the sunspot cycle maximum). The following significant periodicities were found:• in the 20-th cycle: 1.4, 2.1, 2.9, 4.0, 10.7 and 54.2 of month,• in the 21-st cycle: 1.2, 1.6, 2.8, 4.9, 7.8 and 44.5 of month,• in the 22-nd cycle, till March 1992: 1.4, 1.8, 2.4, 7.2, 8.7, 11.8 and 29.1 of month,• in all interval (1969-1992):a)the longer periodicities: 232.1, 121.1 (the dominant at 10.1 of year), 80.7, 61.9 and 25.6 of month,b)the shorter periodicities: 4.7, 5.0, 6.8, 7.9, 9.1, 15.8 and 20.4 of month.Fourier analysis of the LDE-type flare index (FI) yields significant peaks at 2.3 - 2.9 months and 4.2 - 4.9 months. These short periodicities correspond remarkably in the all three last solar cycles. The larger periodicities are different in respective cycles.

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