astronomy

GX 339−4

GX 339−4 is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand GX 339−4 rather than just read about it. In short: GX 339−4 is a moderately strong variable galactic low-mass X-ray binary (LMXB) source and black hole candidate that flares from time to time. From spectroscopic measurements, the mass of the black-hole was found to be at least of 5.8 solar masses.

Key takeaways

GX 339−4 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect GX 339−4 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of GX 339−4 from memory before moving on to harder problems.

Reference excerpt

GX 339−4 is a moderately strong variable galactic low-mass X-ray binary (LMXB) source and black hole candidate that flares from time to time. From spectroscopic measurements, the mass of the black-hole was found to be at least of 5.8 solar masses. Thomas Henry Markert et al. discovered GX 339−4 in 1973, in data obtained by the MIT Cosmic Ray Experiment on OSO-7. An optical counterpoint to the X-ray source was found by Jonathan E. Grindlay in 1979, and it is optically variable. For that reason it was given a variable star designation, V821 Arae, in 1981.

During the outbursts GX 339−4 shows evolution of quasi-periodic oscillations (QPOs). In the rising phase the QPO frequency monotonically increase as the CENBOL propagates closer to the black hole and in the declining phase the QPO frequency monotonically decreases since the CENBOL recedes away from the black hole after viscosity is decreased. The frequency variation is thus well modeled by the propagating and oscillating shock in the sub-Keplerian flow. The entire spectrum also fits very well using a two component advective flow solution. A strong, variable relativistic jet, emitting from radio to infrared wavelengths was observed by several studies.

References

External links http://iopscience.iop.org/1538-3881/123/3/1741: Optical Observations of the black hole candidate GX 339-4 Cowley et al. http://www.universetoday.com/89102/big-ol-black-hole-jets/: Big Ol’ Black Hole Jets

Illustrations

Worked examples

Example 1 — a first encounter with GX 339−4

Start with the simplest possible case. Write down what GX 339−4 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to GX 339−4 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about GX 339−4 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of GX 339−4

In research: GX 339−4 appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses GX 339−4 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: GX 339−4 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ara (constellation), Black hole X-ray binaries, Low-mass X-ray binaries, so understanding it makes those chapters shorter.
In everyday life: Look for GX 339−4 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study GX 339−4 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what GX 339−4 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain GX 339−4 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is GX 339−4 in simple terms?

Why does GX 339−4 matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study GX 339−4?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on GX 339−4.