Wielen Dip

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The Wielen Dip (German translation: Wielen sink ) describes in the stellar statistics a subfrequency of stars on the main sequence with an absolute visual magnitude M V between approximately 6 and 9 mag . The Wielen Dip is named after the astrophysicist Roland Wielen , who first described the infrequency in stars near the sun.

The original mass function describes the distribution of the masses of stars as an exponential function with negative coefficients. The lower the mass of the stars, the greater their number in a star system such as a star cluster , a group of motion or a star association or in the galactic field. This law applies from the most massive main sequence stars of the spectral class O to the red dwarfs and only becomes invalid for the brown dwarfs . Initially in the vicinity of the Sun and later also in open star clusters of Population I , a number of main sequence stars with an absolute visual brightness between approximately 6 and 9 mag was found that was too small compared to the original mass distribution. In this area, the number per brightness cohort corresponds more to a plateau than to the expected continuous increase.

The Wielen Dip is likely real and not caused by selection effects. It already occurs in young star clusters with an age of 50 million years and seems to be more pronounced in the core of many open star clusters such as the Hyades than in the peripheral areas. Der Wielen dip is an increase in opacity by the negative hydrogen in the photosphere of stars with about half a solar mass associated.

Individual evidence

  1. ^ A. Ernst, A. Just, P. Berczik and C. Olczak: Simulations of the Hyades . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1110.1274v1 .
  2. ^ R. Wielen: The Age Distribution and Total Lifetimes of Galactic Clusters . In: Astronomy & Astrophysics . tape 13 , 1971, p. 309-322 .
  3. ^ S. Röser, E. Schilbach, AE Piskunov, NV Kharchenko and R.-D. Scholz: A deep all-sky census of the Hyades . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1105.6093v1 .
  4. ↑ Tim Naylor, EJ Totten, RD Jeffries, M. Pozzo, CR Devey, SA Thompson: Optimal photometry for color-magnitude diagrams and its application to NGC 2547 . In: Astrophysics. Solar and Stellar Astrophysics . 2002, arxiv : astro-ph / 0205005v1 .