Double period variable

from Wikipedia, the free encyclopedia

Double Periodic variable ( English double periodic variable ) are binary systems , show the two periodic light change. One period is that of the orbit and can be detected as an eclipse variability or an elliptical change in light . The second period is about 33 times longer than the primary period and modulates the overall brightness of the binary star system.

properties

Double Period Variables (DPV) were discovered in photometric surveys of Magellanic Clouds in 2003. Their properties were subsequently found in stars in the galactic field of the Milky Way .

The properties of DPVs are:

  • They are semi-separated double stars with an orbital period between one and 16 days
  • The period of the orbital period is stable over a period of decades
  • A second period, which modulates the total brightness of the binary star system over all phases, is 33.1 times longer than the period of revolution
  • The spectrum corresponds to that of an early star with a spectral class B.
  • The line appears in emission and its intensity fluctuates with the period of the long light change
  • The color index also changes with the period of the long light change
  • An infrared excess as a sign of circumstellar matter around the binary star system
  • The Hel-line shows a strong Doppler spread and as an indication of accretion disk interpreted

interpretation

The double-period variables (DPV) belong to the interacting binary stars and show signs of a strong exchange of matter. The companion has already left the main row because its core hydrogen supply has been partially or completely used up. It then fills its Roche volume and, with further expansion, parts of its atmosphere overflow onto the second star. For reasons of conservation of angular momentum , matter cannot fall directly onto the second star, but an accretion disk forms around it. Due to previous interactions, the mass-receiving star is already rotating at the rotation limit and can therefore no longer absorb matter from the accretion disk. The disk grows until there is a resonance between the period of orbit of the binary star system and the period of orbit in the outer orbit of the accretion disk. The result is an ejection of matter into a torus around the binary star system, which is the cause of the infrared excess . The growth and shrinkage of the optically thick accretion disc leads to the observed long-period light change in the DPVs. This interpretation is not supported by a detailed investigation on V393 Sco. The accretion disk then remains constant over the entire long cycle. In contrast, the matter flows out perpendicular to the orbital plane in a variable bipolar stellar wind and this matter scatters the electromagnetic radiation from the binary star system in the direction of the earth, depending on the strength of the stellar wind. The wind is created by the interaction of the gas flow to the B star and the accretion disk around the primary star, whereby a magnetic activity of the companion can also play a role.

According to this interpretation, the DPVs are a link between the W serpentis stars with a very strong exchange of matter and the Algol stars with a weaker mass exchange than the double-period variables.

Examples

AU Mon, V356 Sgr, V393 Sco

literature

  • RE Mennickent, Z. Kolaczkowski: The class of interacting binaries Double Periodic Variables . In: Astrophysics. Solar and Stellar Astrophysics . 2009, arxiv : 0908.3900v1 (English).
  • RE Mennickent, Z. Kolaczkowski: Unveiling the phenomenon of Double Periodic Variables . In: Astrophysics. Solar and Stellar Astrophysics . 2009, arxiv : 0903.4819v1 (English).
  • R. Poleski et al: The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. X. Enigmatic Class of Double Periodic Variables in the Large Magellanic Cloud . tape 60 , no. 3 , 2010, p. 179-196 (English).
  • RE Mennickent, G. Djurasevic, Z. Kołaczkowski, G. Michalska: The evolution stage and massive disc of the interacting binary V393 Scorpii . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1112.2668v1 (English).
  • RE Mennickent, Z. Kołaczkowski, G. Djurasevic, E. Niemczura, M. Diaz, M. Cure, I. Araya, GJ Peters: A cyclic bipolar wind in the interacting binary V393 Scorpii . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1205.6848 (English).