Stars/X-rays/Quiz

X-ray stars is a lecture in the X-ray astronomy of stars. It is part of the X-ray astronomy/Course.

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Quiz
{Which of the following is not a characteristic of the diffuse X-ray background? + a higher intensity than the CMB - isotropic X-ray flux - a wide range of energies - a general increase in intensity from the Galactic plane to the poles - a thermal emission at the lowest energies
 * type=""}

{True or False, Whenever "X-ray" is used in a sentence where the context refers to X-radiation, the "X" is always supposed to be capitalized. + TRUE - FALSE
 * type=""}

{Which of the following are X-radiation astronomy phenomena associated with stellar surface fusion? + luminosities below ~3 x 1038 erg/s + a few SSS with luminosities ≥1039 erg/s + synchrotron radiation - a photosphere - a polar diameter that exceeds ever so slightly the equatorial diameter at solar cycle minimum + super soft X-rays + hot active regions with temperatures hot enough to fuse hydrogen - sunspots at the feet of coronal loops
 * type="[]"}

{True or False, To emit X-rays a source must have some small amount of plasma near or above 106 K. + TRUE - FALSE
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{Intragalactic super soft X-ray sources may be heavily reddened by { interstellar material|interstellar matter (i) }
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{Yes or No, Only a plasma may be luminous. - Yes + No
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{Which of the following are X-radiation astronomy phenomena associated with the Sun? - a core which emits neutrinos - a solar wind which emanates out the polar coronal holes - gravity - the barycenter for the solar system - polar coronal holes + coronal clouds - its position + temperatures at or above 1 MK
 * type="[]"}

{True or False, Any object forming on a dynamical timescale, by gravitational instability, may be a star. + TRUE - FALSE
 * type=""}

{Complete the text: Both { fusion|fusion- (i) } and { accretion|accretion- (i) } powered cataclysmic { variables (i) } have been observed to be X-ray sources.
 * type="{}"}

{Yes or No, X-rays span approximately three decades in wavelength, frequency, and energy. + Yes - No
 * type=""}

{The darker regions in X-rays at the North and South poles of the Sun are coronal holes, where the magnetic field lines are { open (i) }.
 * type="{}"}

{True or False, All gaseous bodies may be a star. - TRUE + FALSE
 * type=""}

{Complete the text: Most { stellar flares|solar flares|flares (i) } and { coronal mass ejections|CMEs (i) } originate in magnetically { active regions (i) } around visible { sunspot|starspot (i) } groupings.
 * type="{}"}

{True or False, An O class star is not hot enough on the surface of its photosphere to emit X-rays. + TRUE - FALSE
 * type=""}

{The population of coronal loops can be directly linked with the { solar cycle (i) }.
 * type="{}"}

{True or False, Super soft X-ray sources are in most cases only detected below 0.5 keV. + TRUE - FALSE
 * type=""}

{Which of the following are theoretical X-ray astronomy phenomena associated with astrophysics? + a thermal plasma mechanism + idea of a close binary + synchrotron radiation + high-density wind extinction - a polar diameter that exceeds ever so slightly the equatorial diameter at solar cycle minimum - super soft X-rays - hot active regions with temperatures hot enough to fuse hydrogen - sunspots at the feet of coronal loops
 * type="[]"}

{True or False, Coronal loops project into the coronal cloud, through the transition region and the chromosphere. + TRUE - FALSE
 * type=""}

{Active regions are the result of enhanced { magnetic fields (i) }.
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{Complete the text: X-ray emission dividing lines may be explained by changes in a { magnetic (i) } field { structure (i) } to that of an { open (i) } topology, leading to a decrease of magnetically confined { plasma (i) }.
 * type="{}"}

{Phenomena associated with nanoflares? + 1017 Joules + very high X-ray emission from happening every 20 s - flickerings - brightenings - mass eruptions + active regions
 * type="[]"}

{True or False, The photosphere of a star may be the result of omnidirectional incoming electrons. + TRUE - FALSE
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{About one third of ejecta observed by satellites at Earth is composed of { magnetic clouds (i) }.
 * type="{}"}

{True or False, The Ca XV emission line is a yellow coronal line at 569.4 nm. + TRUE - FALSE
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{Which stars of the alpha Centauri system are known to have stellar active regions? + Proxima Centauri + Alpha Centauri B - Barnard's star - Alpha Centauri A + Rigel Kent + Alpha Centauri C - Alpha Centauri D
 * type="[]"}

{True or False, "75% of the naked sunspots represented the return of large dominant f spots which had been part of large active regions during previous rotations." - TRUE + FALSE
 * type=""}

{Complete the text: Ultraluminous X-ray sources (ULXs) are { pointlike|point-like (i) }, nonnuclear X-ray sources with { luminosities (i) } above the { Eddington (i) } limit.
 * type="{}"}

{True or False, T Tauri stars are likely to have large areas of starspot coverage. + TRUE - FALSE
 * type=""}

{Complete the text: The X-ray luminosity of the { dominant (i) } group is an order of { magnitude (i) } fainter than that of the X-ray { jet (i) }.
 * type="{}"}

Hypotheses

 * 1) Stars that are in different classes based on their photosphere temperatures may be in the same class based on their X-ray spectra.