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Questions tagged [binary-stars]

Binary stars are a system of two stars rotating around their center of mass, as opposed to single stellar systems such as our solar system.

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Extreme Mass Ratio Inspirals and GWs cycles

I was reading through the following paper GRMHD study of accreting massive black hole binaries in astrophysical environment: A review. Therein, we have the following image It is not quite clear how ...
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Do we use transit photometry to look for a black hole star binary systems?

What would a light curve look like for a black hole transiting a star? Initially I thought it would bend all light essentially blacking out a star but we would probably still detect some however the ...
Joe's user avatar
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How to relate a gravitational plane wave to the GW from a binary system?

I have two different forms of gravitational waves that I am trying to reconcile. A monochromatic GW with angular frequency $\Omega$ propagating in the $\textbf{n}$-direction can be expressed as $$ ...
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Where can I access spectra shift data on a given binary star?

I need to access spectra shift data which I can use to plot a radial velocity of a binary star vs time graph for an assignment. I have looked at SDSS and I havent had any luck being able to access ...
Zandini3's user avatar
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Where can I find spectra data and light curves of a stereoscopic binary star system?

I am trying to find a suitable source of spectra data and/or a light curve of a binary star (no exact star in particular), with which I would use to find velocity and period, and then find masses etc.....
Zandini3's user avatar
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Impact Parameter as function of orbital parameters

In the case of a binary system (pulsar+companion), the impact parameter $\textbf{b}$ is the projection of the binary separation $\textbf{r}$ on the sky plane: \begin{equation}\tag{1} \textbf{b} = \...
gravitone123's user avatar
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How close does a dwarf star have to be to remove the corona from its neighbour in an elliptic binary system?

It is possible for a larger (wider, but less massive) star to mutually orbit a heavy dwarf companion star in a binary system. If the dwarf star gets close enough it can attract the corona of the ...
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Confusion about Post-Newtonian orbital motion (Damour-Deruelle)

In their famous paper in 1985 (link), Damour&Deruelle describe the orbital motion for a binary system taking into account first-order post-Newtonian corrections (1PN). The solution is given in ...
gravitone123's user avatar
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Would there be one rainbow, a double rainbow or bisecting rainbow on a planet with two suns?

I'm just curious if binary stars are low over the horizon and the conditions are just perfect for the formation of rainbow, would I see a single rainbow, double rainbow or two rainbows intersecting ...
user6760's user avatar
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Inquiry Regarding Hypothetical Celestial Mechanics Scenario

How would the addition of a second sun, located at the other focus of the planet's elliptical orbit, impact the motion and orbit of the planet? Specifically, how would the gravitational forces from ...
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Stress-Energy Tensor for a Two Mass System

I just don't understand this tensor and would like to go through an example with you to somehow make sense of it. I consider two spheres with masses $m_1$ and $m_2$, densities $\rho_1$ and $\rho_2$ ...
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Hills Mechanism

The Hills mechanism postulates that when a stellar binary system is perturbed by a supermassive black hole (SMBH), the tidal forces at play result in the capture of one star while simultaneously ...
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Can we correctly invoke energy conservation to explain why binary systems do collapse in GR?

I've learned that binary systems emits gravitational waves, so there is energy leaving the system in the form of waves and so the radius of the binary system must decrease as to maintain the ...
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Could two rotating binary neutron stars create massive cosmic rays if their magnetic fields overlapped and acted on a volume of gas?

The so-called GZK cosmic rays sometimes have an energy equivalent to a baseball moving at 30 m/s. The source of these rays has yet to be determined. Could 2 rotating neutron stars orbiting one ...
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GENERAL RELATIVITY: gravitational time dilation outside 2 bodies [closed]

I know that gravitational time dilation near a single body is: $$T_2=T_1\sqrt{1-\frac{2GM}{rc^2}} $$ Can you give gravitational time dilation formula when in proximity to multiple bodies?
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General relativity: The metric outside of $n$ static bodies [duplicate]

I know that the space time metric outside of 1 static body is the Schwarzschild metric. can anyone tell me what is the metric outside of 2 static bodies or 3 or more static bodies? (' static ' mean ...
mr.thach's user avatar
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How line of sight is determined?

How do they calculate the line of sight of a galaxy or binary star system from an observer's point of view. the velocity of a star in a binary star system depends on the line of sight so how do they ...
starwatcher_65's user avatar
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Orbital phase and gravitational wave phase

I am trying to understand the relation between the orbital phase of binary and the phase of the gravitational wave when expressed as spin-weighted spherical harmonics. The metric perturbation can be ...
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Star with quadrupole in binary system violates Newton's 3th law?

Suppose that, in a binary system of two stars, the star A (and only the star A) has a non-zero quadrupole moment $Q_A$. Then, the star B feels the usual gravity force plus an additional force, ...
gravitone123's user avatar
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Methods for calculating the orbital speed of a star in a binary system

As I understand it, to calculate the speed of rotation of a star in a binary system that is receeding, that is in the same plane as us (inclined at 0 degrees) the method is use the Doppler formula: Δλ/...
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Problem in an ellipse circumscribed on an auxiliary circle

I was reading the book "an introduction to the evolution of single and binary stars", by Mattew Benacquista, and I couldn't understand a specific step in topic 2.1 (Time-Depedent Orbits), ...
Brício Freitas's user avatar
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Meaning of Left-Right Arrow in a Fitting Formula [duplicate]

I initially posted this question on Astronomy Stack Exchange but the site seemed rather inactive so I will try to ask it again on Physics, hopefully it doesn't go against any rules. I was reading this ...
hikari30's user avatar
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1 answer
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Temperature estimate from eclipsing binary

So assuming perfect edge on eclipsing binary, we can estimate the temperature ratio of the two stars because the "blocked area" is the same, and thus the amount of light "dimmed" ...
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3 answers
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Does a double star system have more mass than its constituents?

According to Einstein, energy is equal to mass. Consider a planet that is in gravitational attraction to two stars. Normally I would say that the gravitational attraction is proportional to the masses ...
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Closest possible orbital radius for equal masses

If you have two objects of equal mass, then what’s the closest distance that they can orbit at in terms of their schwarzschild radii? How fast would they be orbiting? What About stable orbits?
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If two black holes orbit around each other should their tidal forces cause a shrinking of the closer parts of their event horizons?

I recently asked a question about the influence of external gravitational fields on the stability of the geometry of a part or all the event horizon of a black hole. I understood the answer in a ...
Krešimir Bradvica's user avatar
2 votes
1 answer
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Approximation concerning gravitational waves from binary neutron star

I'm interested in studying two neutron stars orbiting each other and producing gravitational waves. In textbooks the calculation for the power of the radiation is done by considering the neutron stars ...
Ville Alanko's user avatar
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1 answer
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Are there any binary red supergiants?

I wonder if we ever have identified or observed a pair of binary stars (red supergiants). And I also wonder what would happen if they exploded, (theoretically) as we havent observed it. Also, would ...
schrodingerscat's user avatar
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1 answer
118 views

Does the Centre of Mass of a binary star system accelerate?

At the COM of a binary star system (where both stars has a different mass), the net force at the centre of mass is non-zero. Does this mean that the COM will be accelerating? And if so, wouldn't the ...
john's user avatar
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Can orbiting point masses precess?

In a recent Science News, it mentioned two orbiting black holes (which later combined) were precessing; i.e. their motion did not remain in a stable plane, but rather the plane itself was changing. ...
Daniel's user avatar
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Invariance of binary black hole gravitational waves

Why BBH gravitational waves can be parameterized with the mass ratio? (and is not necessary the value of the two masses explicitly)
Kirt Met's user avatar
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1 answer
66 views

Does SXS catalog for NR simulations have non-spinning, non-eccentric blackholes?

I am looking for NR waveform for two non-spinning and non-eccentric black hole binary merger for small mass ratio. Somehow, on the SXS catalog website, I don't see any such description. Thanks
johnny123's user avatar
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1 answer
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Pair of binary stars orbiting each other

Suppose we have a pair of binary stars orbiting around each other in their mutual gravitational field. My question is, is the trajectory of the combined system would be an ellipse? And, if it is an ...
Sambhav Antriksh's user avatar
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2 answers
68 views

As a binary system start producing gravitational waves even before merge should the stars start losing mass while still orbiting each other?

As a binary system start producing gravitational waves even before merge should the stars start losing mass while still orbiting each other? But is this really difficult to understand as just orbiting ...
Krešimir Bradvica's user avatar
2 votes
1 answer
40 views

Should a black holes binary system in fase of imminent merge shrink the parts of the event horizons of both black holes where they face each other?

Should a black holes binary system in fase of imminent merge shrink the inner parts of the event horizons of both black holes where they directly face each other? So the 'singularities' have the inner ...
Krešimir Bradvica's user avatar
0 votes
1 answer
73 views

How to convert from polarization modes ($h_{+}$, $h_{×}$) to obtain spin-weighted spherical harmonic $h_{lm}$ as a function of $h_{+}$, $h_{×}$?

This question arises from a discussion in the thread How to convert from plus and cross polarization modes ($h_{+}$, $h_{×}$) to spin-weighted spherical harmonic $h_{lm}$? I was looking for a ...
johnny123's user avatar
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Gravitational wave radiation power from dimensional analysis

Let us try to find a formula for the power emitted through gravitational waves (GW) from a binary system in quasi circular orbit. The relevant quantities are the Newton's constant $G_N$, speed of ...
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7 votes
1 answer
540 views

Are orbital eccentricities in a binary system always the same?

Some excercises on Kepler laws and binary system use this relation $$\frac{r_1}{r_2} = \frac{a_1}{a_2},$$ where $r$ is the distance from the center of mass to each object and $a$ is the semi-major ...
bajotupie's user avatar
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2 answers
168 views

How do astronomers calculate the mass of celestial bodies light year from Earth?

I have read in many scientific stuff that mass of this planet or that stars is about '$n$' times the mass of Sun. I have gone through many websites and videos on YouTube but didn't find the right ...
Satyam Upadhyay's user avatar
16 votes
3 answers
2k views

Time dilation effects at the center of a binary black hole system

Imagine two identical black holes in a circular orbit, and Alice is smack-dab in the middle of the system (at the barycenter). Bob is at infinity. Let's assume that Alice and Bob are stationary ...
XYZT's user avatar
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1 answer
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How would I see if there is a transit in this light curve?

I am trying to detect if some binary star systems have exoplanets orbiting them. I've been completing this project for many weeks now, and have managed to write some code that will plot light curves ...
Alice's user avatar
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1 vote
1 answer
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How likely is it that a typical pair of black holes will eventually merge?

Gravitational wave observatories have found many pairs of black holes merging. I understand that before they were working there were estimates of the rate at which they ought to be found. To me it ...
mmesser314's user avatar
5 votes
2 answers
709 views

Can two relativistic black holes' event horizons overlap and separate again?

I have read this question: What I have not seen is a purely classical argument for the non-separation of a black hole merger. One can obviously take the time reversed spacetime manifold of a merger ...
Árpád Szendrei's user avatar
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1 answer
79 views

Gauge independence of the gravitational-wave frequency and gauge dependence of the binary separation?

In the seminal paper by Cutler & Flanagan (1994), which uses multi-timescale analysis to derive waveforms in the post-Newtonian approximation without spin effects, they state that, "In Eq. (...
Daddy Kropotkin's user avatar
5 votes
2 answers
219 views

Black holes: Is merger inevitable when horizons touch?

I watched a simulation of the binary black hole merger of 2019 April 12 https://www.ligo.caltech.edu/video/ligo20200420v1 When the "apparent horizons" (their terminology; are those ...
Daniel's user avatar
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1 vote
1 answer
117 views

Dissipation caused by Gravitational Wave Emission

Two massive bodies orbiting each other can lose energy through gravitational wave emission until colliding. Can a single massive body, moving with constant velocity with respect to an observer, lose ...
rel-s's user avatar
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5 votes
1 answer
423 views

Is there an approximate expression for the force between two black holes?

Just curious: is there an approximate expression for the gravitational attraction between two Schwarzschild black holes of masses $M$ and $m$, held without relative speed at some center to center ...
user avatar
6 votes
2 answers
131 views

As of 2021 in how many binary systems has the period decrease due to gravitational waves been measured?

I am searching for data for the period decrease of binary systems due to gravitational waves. I am aware of three systems in which it was possible to measure this period decrease: The Hulse-Taylor ...
Benito McLanbeck's user avatar
2 votes
0 answers
221 views

Gravitational waves in the post-Newtonian expansion

I have spent some time trying to understand gravitational waves in the context of the post-Newtonian expansion. As far as I understand it, the general relativistic equation of motion can be ...
Benito McLanbeck's user avatar
2 votes
3 answers
335 views

Should the stars of a relativistic binary system have tangential acceleration?

Should the stars of a relativistic binary system have tangential acceleration?
Janko Bradvica's user avatar