Supergiant Fast X-ray Transient

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Supergiant Fast X-ray Transients are a class of X-ray binary stars with a supergiant accompanying a compact accreting star. They show X-ray luminosity in the outbreak of 10 36 to 10 37 erg / s and long phases of low activity. Although the observed properties of the companion star, the period of rotation and the orbital period of the accreting neutron star do not differ from other high-mass X-ray binary stars, the Supergiant Fast X-ray Transients (SFXT for short) are temporary objects in the X-ray sky, while the normal high-mass X-ray binary stars are permanent Sources are.

properties

Supergiant Fast X-ray Transients were first discovered by X-ray satellites that monitor the sky in search of gamma ray bursts and quickly align themselves with erupting objects. The outbreaks last 100 to 10,000 seconds and are too short and too rare to be detected by surveys . The duty cycle, the duration of outbreaks to the resting phase, is less than five percent for all SFXTs. In some SFXTs, the outbreaks repeat quasi-periodically with the period of orbit of the neutron star around the early supergiant and are completely irregular in other SFXTs. A characteristic of the Supergiant Fast X-ray Transients is that many members of this class show an accumulation of many short flares, which are then followed by a long period of low activity. The outbursts are triggered by accretion events when the rotating magnetic neutron star ingests more matter from the stellar wind of the OB star. The orbital period of the stars around the common center of gravity is between three and a few hundred days. In the resting phases, the X-ray luminosity is around 10 32 erg / s. The X-ray spectrum is hard and often shows signs of absorption in the soft X-ray region .

The characteristic outbursts of the Supergiant Fast X-ray Transients are either attributed to inhomogeneities in the stellar wind of the OB supergiant or there is a gate mechanism that controls the flow of matter into the accretion disk or onto the neutron star.

Examples

  • IGR J16479-4514
  • IGR J11215-5952
  • SAX J1818.6-1703
  • XTE J1739-302

literature

  • A. Paizis, L. Sidoli: Cumulative luminosity distributions of Supergiant Fast X-ray Transients in hard X-rays . In: Astrophysics. Solar and Stellar Astrophysics . 2014, arxiv : 1401.6861v1 .
  • P. Romano et al .: The 100-month Swift catalog of supergiant fast X-ray transients I. BAT on-board and transient monitor flares . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1312.4955v2 .
  • L. Ducci et al .: Spectral and temporal properties of the supergiant fast X-ray transient IGR J18483-0311 observed by INTEGRAL . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1310.4728v1 .
  • Lara Sidoli: Supergiant Fast X-ray Transients: a review . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1301.7574v1 .