Correlation Between Energy Spectral States and Fast Time Variability and Further Evidence for Marginally Stable Orbit in 4U 1820-30

Details Correlation Between Energy Spectral States and Fast Time Variability and Further Evidence for Marginally Stable Orbit in 4U 1820-30 Correlation Between Energy Spectral States and Fast Time Variability and Further Evidence for Marginally Stable Orbit in 4U 1820-30

May 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998aas...192.7803z&link_type=abstract

American Astronomical Society, 192nd AAS Meeting, #78.03; Bulletin of the American Astronomical Society, Vol. 30, p.932

Astronomy and Astrophysics

Astronomy

1

Scientific paper

We report results from a long-term monitoring data set obtained with the Rossi X-ray Timing Explorer (RXTE) from the bright globular cluster binary source 4U 1820-30. During this monitoring, the source intensity varied from a flux of 2.9x 10(-9) ergs\ cm(-2) s(-1) to 8.5x 10(-9) ergs\ cm(-2) s(-1) in the 2-10 keV band, which correspond to, respectively, a count rate of 1,600 cps and 4,500 cps in the nominal 2-60 keV RXTE-PCA band. Its energy spectral state was observed to encompass both the banana branches and the island state. Kilohertz QPOs were observed to exist in the upper-banana and lower-banana branches, as well as in the island state. In particular, we report that the kHz QPOs were present only when the soft-color (defined as the flux ratio of the 3.9-5.0 keV band to the 1.7-3.9 keV band) was below 0.78 without regard to the overall count rate and without regard to whether the source is in any one of the three branches or states. Their centroid frequency was well correlated with the overall count rate below 2,500 cps. When the count rate was above 2,500 cps, the QPO frequency was consistent with a constant independent of the overall count rate. We take this as further evidence that the inner edge of the accretion had reached the marginally stable orbit, and therefore the constant 1060+/- 20 Hz is the marginally stable orbit frequency.

Affiliated with

Also associated with

No associations

Rating

Correlation Between Energy Spectral States and Fast Time Variability and Further Evidence for Marginally Stable Orbit in 4U 1820-30 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Correlation Between Energy Spectral States and Fast Time Variability and Further Evidence for Marginally Stable Orbit in 4U 1820-30, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Correlation Between Energy Spectral States and Fast Time Variability and Further Evidence for Marginally Stable Orbit in 4U 1820-30 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1365908