Detection of a Strong Excess Noise Component in the Low State of 4U 1705-44
Abstract
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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1989
- DOI:
- 10.1086/185429
- Bibcode:
- 1989ApJ...340L..21L
- Keywords:
-
- Galactic Bulge;
- Milky Way Galaxy;
- Neutron Stars;
- X Ray Binaries;
- Color-Color Diagram;
- Exosat Satellite;
- Noise Intensity;
- Power Spectra;
- Stellar Oscillations;
- Astrophysics;
- STARS: INDIVIDUAL ALPHANUMERIC: 4U 1705-44;
- STARS: NEUTRON;
- STARS: PULSATION;
- X-RAYS: BINARIES