1997/06/10 by Eric C. Ford, Philip Kaaret, Kaiyou Chen +7
Physics and Astronomy · #astro-ph
paper · pdf · doi:10.1086/310827
9 pages, 3 figures, submitted to ApJL, for more information on this and other QPO papers see http://www.astro.columbia.edu/~eric/qpos.html
arxiv created 1997/06/10 · arxiv updated 2009/12/01
We investigate the behavior of the high frequency quasi-periodic oscillations (QPOs) in 4U 0614+091, combining timing and spectral analysis of RXTE observations. The energy spectra of the source can be described by a power law (alpha ~ 2.8) and a blackbody (kT ~ 1.5), with the blackbody accounting for 10 - 20% of the total energy flux. We find a robust correlation of the frequency, nu, of the higher frequency QPO near 1 kHz with the flux of the blackbody, FBB. The slope of this correlation, dlog(nu)/dlog(FBB), is 0.27 to 0.37. The source follows the same relation even in observations separated by several months. The QPO frequency does not have a similarly unique correlation with the total flux or the flux of the power law component. The RMS fraction of the higher frequency QPO rises with energy from 6.8 +- 1.5 % (3-5 keV) to 21.3 +- 4.0 % (10-12 keV). For the lower frequency QPO, however, it is consistent with a constant value of 5.4 +- 0.9 %. The results may be interpreted in terms of a beat frequency model for the production of the high frequency QPOs.