期刊
ASTRONOMY & ASTROPHYSICS
卷 519, 期 -, 页码 -出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361/200913981
关键词
accretion, accretion disks; X-rays: binaries; X-rays: individuals: Vela X-1; methods: statistical
资金
- Bundesministerium fur Wirtschaft und Technologie [50 OR0808]
- DAAD
- European Commission [ITN215212]
- ESA
We investigate the structure of the wind in the neutron star X-ray binary system Vela X-1 by analyzing its flaring behavior. Vela X-1 shows constant flaring, with some flares reaching fluxes of more than 3.0 Crab between 20-60 keV for several 100 s, while the average flux is around 250 mCrab. We analyzed all archival INTEGRAL data, calculating the brightness distribution in the 20-60 keV band, which, as we show, closely follows a log-normal distribution. Orbital resolved analysis shows that the structure is strongly variable, explainable by shocks and a fluctuating accretion wake. Analysis of RXTE ASM data suggests a strong orbital change of N-H. Accreted clump masses derived from the INTEGRAL data are on the order of 5x10(19) - 10(21) g. We show that the lightcurve can be described with a model of multiplicative random numbers. In the course of the simulation we calculate the power spectral density of the system in the 20-100 keV energy band and show that it follows a red-noise power law. We suggest that a mixture of a clumpy wind, shocks, and turbulence can explain the measured mass distribution. As the recently discovered class of supergiant fast X-ray transients (SFXT) seems to show the same parameters for the wind, the link between persistent HMXB like Vela X-1 and SFXT is further strengthened.
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