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Stars/X-rays/Quiz

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This is a Chandra X-ray Observatory image of LP 944-20 before flare and during flare. Credit: CXO/NASA.

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

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1 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

2 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

3 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

4 True or False, To emit X-rays a source must have some small amount of plasma near or above 106 K.

TRUE
FALSE

5 Intragalactic super soft X-ray sources may be heavily reddened by

6 Yes or No, Only a plasma may be luminous.

Yes
No

7 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

8 True or False, Any object forming on a dynamical timescale, by gravitational instability, may be a star.

TRUE
FALSE

9 Complete the text:

Both

and

powered cataclysmic

have been observed to be X-ray sources.

10 Yes or No, X-rays span approximately three decades in wavelength, frequency, and energy.

Yes
No

11 The darker regions in X-rays at the North and South poles of the Sun are coronal holes, where the magnetic field lines are

.

12 True or False, All gaseous bodies may be a star.

TRUE
FALSE

13 Complete the text:

Most

and

originate in magnetically

around visible

groupings.

14 True or False, An O class star is not hot enough on the surface of its photosphere to emit X-rays.

TRUE
FALSE

15 The population of coronal loops can be directly linked with the

.

16 True or False, Super soft X-ray sources are in most cases only detected below 0.5 keV.

TRUE
FALSE

17 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

18 True or False, Coronal loops project into the coronal cloud, through the transition region and the chromosphere.

TRUE
FALSE

19 Active regions are the result of enhanced

.

20 Complete the text:

X-ray emission dividing lines may be explained by changes in a

field

to that of an

topology, leading to a decrease of magnetically confined

.

21 Phenomena associated with nanoflares?

1017 Joules
very high X-ray emission from happening every 20 s
flickerings
brightenings
mass eruptions
active regions

22 True or False, The photosphere of a star may be the result of omnidirectional incoming electrons.

TRUE
FALSE

23 About one third of ejecta observed by satellites at Earth is composed of

.

24 True or False, The Ca XV emission line is a yellow coronal line at 569.4 nm.

TRUE
FALSE

25 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

26 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

27 Complete the text:

Ultraluminous X-ray sources (ULXs) are

, nonnuclear X-ray sources with

above the

limit.

28 True or False, T Tauri stars are likely to have large areas of starspot coverage.

TRUE
FALSE

29 Complete the text:

The X-ray luminosity of the

group is an order of

fainter than that of the X-ray

.


Hypotheses

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Main resource: 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.

See also

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{{Radiation astronomy resources}}

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