Detection of a strong excess noise component in the low state of 4U 1705-44

Journal Article · Mon May 01 04:00:00 EDT 1989 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/185429· OSTI ID:5727124

Langmeier, A; Hasinger, G; Truemper, J

The timing analysis of four Exosat observations of the bright Galactic burst source 4U 1705-44 is presented. A correlation is found between the aperiodic noise components and the spectral variability. 4U 1705-44 shows in its low-intensity state a strong variability of the X-ray flux in the frequency range 1-64 Hz, corresponding to an rms modulation of 20 percent. During this low-intensity state, where the spectrum is hardest and type I bursts are most frequent, the hardness of the energy spectrum shows a negative correlation with intensity. In the high-intensity state, the shape of the power spectrum is best described by a power law. In this state, no significant signal at frequencies greater than 1 Hz is measured and the spectral hardness shows no clear correlation with intensity. 17 refs.

• Research Organization: Max-Planck-Institut fuer extraterrestrische Physik, Garching (Germany, F.R.); Messerschmitt-Boelkow-Blohm GmbH, Munich (Germany, F.R.); Max-Planck-Institut fuer extraterrestrische Physik, Garching (Germany, F.R.)
• OSTI ID: 5727124
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 340; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BINARY STARS
COSMIC RAY SOURCES
COSMIC X-RAY BURSTS
COSMIC X-RAY SOURCES
ENERGY SPECTRA
GALAXIES
MILKY WAY
NEUTRON STARS
NOISE
OSCILLATIONS
RADIATION FLUX
SATELLITES
SPECTRA
STARS
VARIATIONS