NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
X-Ray Variation Statistics and Wind Clumping in Vela X-1We 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 seconds, 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. Accreted clump masses derived from the INTEGRAL data are on the order of 5 x 10(exp 19)-10(exp 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.
Document ID
20100024533
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Furst, Felix
(Erlangen-Nuernberg Univ. Bamberg, Germany)
Kreykenbohm, Ingo
(Erlangen-Nuernberg Univ. Bamberg, Germany)
Pottschmidt, Katja
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Wilms, Joern
(Erlangen-Nuernberg Univ. Bamberg, Germany)
Hanke, Manfred
(Erlangen-Nuernberg Univ. Bamberg, Germany)
Rothschild, Richard E.
(California Univ., San Diego La Jolla, CA, United States)
Kretschmar, Peter
(European Space Astronomy Center (ESAC) Madrid, Spain)
Schulz, Norbert S.
(Massachusetts Inst. of Tech. Cambridge, MA, United States)
Huenemoerder, David P.
(Massachusetts Inst. of Tech. Cambridge, MA, United States)
Klochkov, Dmitry
(Institute for Astronomy and Astrophysics Germany)
Staubert, Rudiger
(Institute for Astronomy and Astrophysics Germany)
Date Acquired
August 24, 2013
Publication Date
May 21, 2010
Subject Category
Astrophysics
Funding Number(s)
CONTRACT_GRANT: DLR 50 OR 0808
CONTRACT_GRANT: ITN 215212
CONTRACT_GRANT: NNG06EO90A
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available