The discovery of 7 and 24-28 hertz quasi-periodic oscillations in the X-ray flux of GX 17 + 2 (4U 1813-14)

Abstract

view Abstract Citations (18) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Discovery of 7 and 24--28 Hertz Quasi-periodic Oscillations in the X-Ray Flux of GX 17+2 (4U 1812-14) Stella, L. ; Parmar, A. N. ; White, N. E. Abstract The discovery of quasi-periodic oscillations (QPOs) in the X-ray flux of the bright galactic bulge source GX 17 + 2 is reported. The relation between the QPO frequency and the source intensity of GX 17 + 2 is bimodal and is similar to that previously reported from Sco X-1. On August 20-21, 1985, the QPO frequency was about 7 Hz and showed no significant change associated with about 10 percent intensity variations. In another observation 25 days later, the frequency varied between 24 Hz and 28 Hz and was strongly correlated with 5 percent variations in intensity. During an observation on August 3-4, 1983, no QPOs were observed with an upper limit to the rms strength of about 1.4 percent. A search for a possible correlation between the QPOs and spectral properties was carried out by fitting to the spectra the disk plus black-body boundary layer model suggested by White et al. (1986). The QPO frequency was larger when the black-body luminosity was minimum, contrary to that observed from Sco X-1. Publication: The Astrophysical Journal Pub Date: October 1987 DOI: 10.1086/165640 Bibcode: 1987ApJ...321..418S Keywords: Galactic Nuclei; Stellar Oscillations; X Ray Stars; Astronomical Models; Black Body Radiation; Galactic Bulge; Temporal Resolution; Astrophysics; X-RAYS: SOURCES; X-RAYS: BINARIES; STARS: PULSATION full text sources ADS | data products SIMBAD (4)