2003A&A...410..217G


Query : 2003A&A...410..217G

2003A&A...410..217G - Astronomy and Astrophysics, volume 410, 217-230 (2003/10-4)

Boundary layer, accretion disk and X-ray variability in the luminous LMXBs.

GILFANOV M., REVNIVTSEV M. and MOLKOV S.

Abstract (from CDS):

Using Fourier frequency resolved X-ray spectroscopy we study short term spectral variability in luminous LMXBs. With RXTE/PCA observations of 4U 1608-52 and GX 340+0 on the horizontal/normal branch of the color-intensity diagram we show that aperiodic and quasiperiodic variability on ∼second-millisecond time scales is caused primarily by variations of the luminosity of the boundary layer. The emission of the accretion disk is less variable on these time scales and its power density spectrum follows P_ disk_(f)∝f–1 law, contributing to observed flux variation at low frequencies and low energies only. The kHz QPOs have the same origin as variability at lower frequencies, i.e. independent of the nature of the ``clock'', the actual luminosity modulation takes place on the neutron star surface. The boundary layer spectrum remains nearly constant in the course of the luminosity variations and is represented to certain accuracy by the Fourier frequency resolved spectrum. In the considered range {dot}(M)~(0.1-1){dot}(M)Edd it depends weakly on the global mass accretion rate and in the limit {dot}(M)~{dot}(M)Edd is close to Wien spectrum with kT∼2.4keV (in the distant observer's frame). The spectrum of the accretion disk emission is significantly softer and in the 3-20keV range is reasonably well described by a relativistic disk model with a mass accretion rate consistent with the value inferred from the observed X-ray flux.

Abstract Copyright:

Journal keyword(s): accretion, accretion disks - instabilities - stars: binaries: general - stars: fundamental parameters - X-rays: general - X-rays: stars

Simbad objects: 6

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Number of rows : 6
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 V* V1055 Ori LXB 06 17 07.3565603963 +09 08 13.515857360   18.80 18.5     ~ 557 1
2 V* QX Nor LXB 16 12 43.0 -52 25 23           ~ 901 1
3 V* V818 Sco LXB 16 19 55.0692669024 -15 38 25.017666540 11.60 12.40 11.1     Oev 1631 0
4 4U 1642-45 LXB 16 45 47.7 -45 36 40     14.30     ~ 414 1
5 4U 1758-25 LXB 18 01 09.7308060816 -25 04 44.120221284     11.08     ~ 652 1
6 HD 226868 HXB 19 58 21.6757355952 +35 12 05.784512688 9.38 9.72 8.91 8.42   O9.7Iabpvar 4304 0

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