Symbiotic X-ray binary star

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Symbiotic X-ray binaries (SyXB) are a subgroup of the X-ray binary stars , which consist of an accreting neutron star and a red giant . The red giant transfers matter from its extensive atmosphere to its companion by means of stellar winds or when the Roche limit is exceeded , with the X-rays mainly arising in an accretion disk around the compact star and / or when it hits the surface of the neutron star.

properties

Only a few Symbiotic X-ray binaries have been discovered and simulations of the growth of massive binary systems can be in the Milky Way only about 100 to 1,000 of these binaries expect. The X-ray spectrum of the SyXBs consists of a soft thermal component that arises near the accretor and in some cases a hard Compton component . The X-ray luminosity is usually in the range from 10 32 to 10 34 erg / s , with GX 1 + 4 reaching values ​​of up to 10 37 erg / s. The rotation times of the neutron stars derived from the X-ray light curves are between 100 seconds and up to 5 hours. The period of orbit in the binary stars is difficult to determine and is in the range of a few 100 to 1,000 days as in the symbiotic stars . The spectral energy distribution of the SyXBs suggests that jets arise with these accreting objects as with the microquasars . The X-ray luminosity is variable over several orders of magnitude, whereby the symbiotic X-ray binaries, like other X-ray binary stars, switch back and forth between a soft, luminous and a weak, hard state. This is likely caused by a change in viscosity in the accretion disk due to magnetorotational instability that regulates flow in the disk. This mechanism is also suspected in other X-ray binary stars such as the X-ray novae .

Separation into symbiotic stars

The Symbiotic X-ray Binaries are closely related to the Symbiotic Stars, which also consist of a red giant, but which has a white dwarf as a companion . In the case of nearby symbiotic stars, X-rays could also be detected, but the symbiotic stars, in contrast to the SyXBs, show a pronounced change in light in the optical. The optical spectrum of the symbiotic stars shows excited emission lines , while the spectrum of the symbiotic X-ray binaries shows only a simple spectrum of a red giant again with the exception of GX 1 + 4.

Examples

  • GX 1 + 4 (V2116 Oph)
  • GX 1954 + 31
  • IGR J16194-2810
  • 4U1700 + 24 (V934 Her)

literature

  • AA Nucita et al .: The puzzling symbiotic X-ray system 4U1700 + 24 . In: Astrophysics. Solar and Stellar Astrophysics . 2014, arxiv : 1401.2053v1 .
  • Robert I. Hynes et al .: CXOGBS J173620.2-293338: A CANDIDATE SYMBIOTIC X-RAY BINARY ASSOCIATED WITH A BULGE CARBON STAR . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1310.2597v1 .
  • Yuiko Kitamura et al .: Suzaku Observation of the Symbiotic X-Ray Binary IGR J16194-2810 . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1308.5803v1 .
  • G.-L. Lu, C.-H. Zhu, KA Postnov, LR Yungelson, AG Kuranov, N. Wang: Population Synthesis for Symbiotic X-ray Binaries . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1205.5696v1 .
  • K. Postnov et al .: Wind accretion in symbiotic X-ray binaries . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1110.1156v1 .