Energy-dependent time lags in QPO from Cygnus X-2.
Abstract
New features of quasi-periodic oscillations (QPO) from Cyg X-2 with a mean centroid frequency of 5.3 + or - 0.2 Hz are obtained from the observations with the Ginga satellite. The ratio of the QPO amplitude to the average X-ray intensity increases with increasing X-ray energy in the range 5-18 keV. Below 5 keV, however, the relative QPO amplitude increases again slightly toward lower energies. This turnover of the relative amplitude seems to be related to the phase shifts of the QPO. No significant phase difference is found between the QPO in the two lowest energy bands, 1-2.3 and 2.3-4.6 keV. However, the QPO in the higher energy bands have phase lags relative to the QPO in the two lowest energy bands. The amount of lag increases up to 80 ms with increasing energy.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- 1989
- Bibcode:
- 1989PASJ...41..557M
- Keywords:
-
- Cygnus Constellation;
- Neutron Stars;
- Stellar Oscillations;
- Time Lag;
- X Ray Binaries;
- Japanese Space Program;
- Phase Shift;
- Satellite Observation;
- Astrophysics