Flickering (astronomy)

Flickering describes an irregular, rapid change in brightness in variable stars . Flickering always occurs in connection with accretion , the incidence of gas or plasma on a compact object.

properties

The flickering is not periodic , but there is a time scale of changes in brightness from seconds to 10 minutes, which is characteristic of an object. This time scale can change with increased accretion, such as the outbreak of a dwarf nova.

The amplitude of the flickering ranges from just above the detection limit up to 2  magnitudes . Flickering could be detected in the ultraviolet , optical and near infrared. In general, the amplitude of the flickering increases with the shorter the wavelength; H. towards ultraviolet.

Star classes with flickering

Flickering could be detected in all star classes with accretion:

• in the pre-main sequence stars of the type T Tauri and FU Orionis , matter falls from a protoplanetary disk onto the central star .
• in cataclysmic variables with a weak magnetic field, matter flows from a companion through an accretion disk to a white dwarf .
• In the case of the cataclysmic variables with strong magnetic fields , the formation of an accretion disk is suppressed.
• the related symbiotic stars , whose mass-losing star is a red giant instead of a main sequence star as in the cataclysmic variables , can show flickering when active.
• in the case of low-mass X-ray binary stars , the accreting object is a neutron star .

Outside stars, flickering has also been described in accretive black holes in the center of galaxies ( active galactic nuclei ).

swell

The sources of flickering have been described:

• Interaction of the gas flow when it hits the accretion disc (the hot spot)
• the effect of turbulence in the accretion disk
• magnetic short circuits in the accretion disk
• the transition layer between the accretion disk and the compact star ( white dwarf , neutron star ).

In the binary star systems described above, each of these places of origin of the flickering could be assigned to certain stars on the basis of cover light changes.

See also

• Flicker (astronomy)
• Flicker star

Individual evidence

1. ^ T. Fritz, A. Bruch: Studies of the flickering in cataclysmic variables. IV. Wavelet transforms of flickering light curves . In: Astronomy and Astrophysics . tape 332 , 1998, pp. 586-604 .
2. ^ SJ Kenyon: The Symbiotic Stars (Cambridge Astrophysics) . Cambridge University Press, 2009, ISBN 978-0-521-09331-6 .
3. ↑ Scott J. Kenyon et al .: FLICKERING IN FU ORIONIS . In: The Astrophysical Journal . tape 531 , 2000, pp. 1028-1036 .
4. ^ Brian Warner: Cataclysmic Variable Stars . Cambridge University Press, 1995, ISBN 978-0-521-54209-8 .
5. ↑ JL Sokoloski, SJ Kenyon: CH CYGNI. II. OPTICAL FLICKERING FROM AN UNSTABLE DISK . In: The Astrophysical Journal . tape 584 , 2003, p. 1027-1034 .
6. ↑ JL Sokoloski, SJ Kenyon: Multicolour flickering studies of X1822 - 371 . In: Monthly Notice of the Royal Astronomical Society . tape 335 , 2002, pp. 665-672 , doi : 10.1046 / j.1365-8711.2002.05657.x .
7. ↑ Sunil Chandra, KS Baliyan, S. Ganesh, UC Joshi: Rapid optical variability in blazar S5 0716 + 71 during 2010 March . In: Astrophysics. Solar and Stellar Astrophysics . 2011, doi : 10.1088 / 0004-637X / 731/2/118 , arxiv : 1104.0514v1 .
8. ↑ Andrej Dobrotka, Shin Mineshige, Jorge Casares: Flickering study of nova like system KR Aur and UU Aqr . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1111.3744v1 .
9. ↑ A. Bruch: Flickering in cataclysmic variables - Its properties and origins . In: Astronomy and Astrophysics . tape 266 , 1992, pp. 237-265 .