This question has to do with binary star systems, where 'i' is the angle of inclination of the system.Calculate the mean expectation value of the factor \sin^{3} i, i.e., the mean value it would have among an ensemble of binaries with random inclinations.

Yasmin

Yasmin

Answered question

2021-08-09

This question has to do with binary star systems, where 'i' is the angle of inclination of the system.
Calculate the mean expectation value of the factor sin3 i, i.e., the mean value it would have among an ensemble of binaries with random inclinations. Find the masses of the two stars, if sin3 i has its mean value.
Hint: In spherical coordinates, (θ,ϕ), integrate over the solid angle of a sphere where the observer is in the direction of the z-axis, with each solid angle element weighted by sin3θ.
v1=100kms
v2=200kms
Orbital period =2 days
M1=5.74e33g
M2=2.87e33g

Answer & Explanation

Derrick

Derrick

Skilled2021-08-10Added 94 answers

Step 1
For a binary star system, the ratio of their velocities and their masses are related as,
m1m2=v2v1
=200kms100kms
=2
m1=2m2...(1)
Step 2
The Kepler equation for a binary star system is,
m1+m2=P2πG(v1+v2)3sin3(i)
=(2×24×3600s)2π(6.67×1011Nm2kg2} (105ms1+2×105ms1)3sin3(i)
=(1.11×1031kg)sin3(i)(M2×1030kg)
=5.556Msin3(i)
Step 3
The mean expectation value of sin3 i be given as,
sin3(i)=0π2sin3(i){sinidi}
0π2sin4(i)di
=[3i8sin(2i)4+sin(4i)32]0π2
=3π16
=0.59
Step 4
From equation (1), m1=2m2
Hence,
3m2=5.556Msin3(i)
m2=5.556M3(0.59)
=3.1389M

Do you have a similar question?

Recalculate according to your conditions!

New Questions in Linear algebra

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?