Magnetic braking of an aligned rotator during star formation - an exact, time-dependent solution

1980 ◽  
Vol 237 ◽  
pp. 877 ◽  
Author(s):  
T. Ch. Mouschovias ◽  
E. V. Paleologou
Keyword(s):  
Star Formation ◽  
Time Dependent ◽  
Exact Time ◽  
Magnetic Braking ◽  
Time Dependent Solution

Time-dependent solution of the logistic model for population growth in random environment

1980 ◽  
Vol 17 (04) ◽  
pp. 1083-1086
Author(s):  
Prajneshu
Keyword(s):  
Population Growth ◽  
Stationary Solution ◽  
Random Environment ◽  
Carrying Capacity ◽  
Logistic Model ◽  
Time Dependent ◽  
Kolmogorov Equation ◽  
Exact Time ◽  
Time Dependent Solution

The exact time-dependent solution as well as the stationary solution of the logistic model for population growth with varying carrying capacity is worked out in both the Stratonovich and Ito calculi by solving the forward Kolmogorov equation.

Ideally conducting magnetostatic equilibria and associated time dependent, resistive flows

1971 ◽  
Vol 6 (1) ◽  
pp. 125-136 ◽  
Author(s):  
John C. Stevenson
Keyword(s):  
Magnetic Field ◽  
Energy Equation ◽  
Incompressible Flows ◽  
Neutral Point ◽  
Time Dependent ◽  
Two Dimensional ◽  
Exact Time ◽  
Field Lines ◽  
Time Dependent Solution ◽  
The Magnetic Field

Several types of two-dimensional solutions for the equations of magnetohydrodynamics are described. For all these solutions the magnetic field contains at least one hyperbolic neutral point. Two new magnetostatic equilibria are introduced for the ideally conducting case. The magnetic field associated with one of these is used to construct an exact time-dependent solution of the MilD equations where the fluid is necessarily at rest. In the case where the field lines are hyperbolae, it is demonstrated that retention of the energy equation (ordinarily decoupled for incompressible flows) implies that the flow beginning at rest, remains at trest

Time-dependent solution of the logistic model for population growth in random environment

1980 ◽  
Vol 17 (4) ◽  
pp. 1083-1086 ◽  
Author(s):  
Prajneshu
Keyword(s):  
Population Growth ◽  
Stationary Solution ◽  
Random Environment ◽  
Carrying Capacity ◽  
Logistic Model ◽  
Time Dependent ◽  
Kolmogorov Equation ◽  
Exact Time ◽  
Time Dependent Solution

The exact time-dependent solution as well as the stationary solution of the logistic model for population growth with varying carrying capacity is worked out in both the Stratonovich and Ito calculi by solving the forward Kolmogorov equation.

scholarly journals The White Dwarf Mass and Orbital Period Distribution in Zero-Age Cataclysmic Binaries

1989 ◽  
Vol 114 ◽  
pp. 440-442
Author(s):  
M. Politano ◽  
R. F. Webbink
Keyword(s):  
Star Formation ◽  
White Dwarf ◽  
Galactic Disk ◽  
Orbital Energy ◽  
Orbital Parameter ◽  
Orbital Parameters ◽  
Cataclysmic Binaries ◽  
Magnetic Braking ◽  
Orbital Periods ◽  
The Individual

A zero-age cataclysmic binary (ZACB) we define as a binary system at the onset of interaction as a cataclysmic variable. We present here the results of calculations of the distributions of white dwarf masses and of orbital periods in ZACBs, due to binaries present in a stellar population which has undergone continuous, constant star formation for 1010 years.Distributions of ZACBs were calculated for binaries formed t years ago, for log t = 7.4 (the youngest age at which viable ZACBs can form) to log t = 10.0 (the assumed age of the Galactic disk), in intervals of log t = 0.1. These distributions were then integrated over time to obtain the ZACB distribution for a constant rate of star formation. To compute the individual distributions for a given t, we require the density of systems forming (number of pre-cataclysmics forming per unit volume of orbital parameter space), n£(t), and the rates at which the radii of the secondary and of its Roche lobe are changing in time, s (t) and L, s (t), respectively. In calculating nf(t), we assume that the distribution of the orbital parameters in primordial (ZAMS) binaries may be written as the product of the distribution of masses of ZAMS stars (Miller and Scalo 1979), the distribution of mass ratios in ZAMS binaries (cf. Popova, et al., 1982), and the distribution of orbital periods in ZAMS binaries (Abt 1983). In transforming the the orbital parameters from progenitor (ZAMS) to offspring (ZACB) binaries, we assume that all of the orbital energy deposited into the envelope during the common envelope phase leading to ZACB formation goes into unbinding that envelope. R.L, s (t) is determined from orbital angular momentum loss rates due to gravitational radiation (Landau and Lifshitz 1951) and magnetic braking (γ = 2 in Rappaport, Verbunt, and Joss 1983). We turn off magnetic braking if the secondary is completely convective.

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