1997/05/30 by M. Mendez, Mariano Méndez, M. van der Klis +17
Environmental Science · Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #Methane Hydrates and Related Phenomena #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9705250
To appear in ApJL. AAS LaTex v4.0 (10 pages, 4 ps-figures)
arxiv created 1997/05/30 · openalex publication_date 1997/05/30 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We report three RXTE/PCA observations of the low-mass X-ray binary 4U 0614+09. They show strong (~ 30% rms) band-limited noise with a cut-off frequency varying between 0.7 and 15 Hz in correlation with the X-ray flux. We observe two non-simultaneous 11-15% (rms) kHz peaks near 728 and 629 Hz in the power spectra of two of our observations when the X-ray flux is ~ 10-9 erg cm-2 s-1 (2-10 keV), but find no QPO (< 6% rms) when the X-ray flux is half that. We suggest that count rate may not be a good measure for M even in sources as intrinsically weak as 4U 0614+09, and that QPO frequency and noise cutoff frequency track M more closely than count rate. The QPO increases in rms amplitude from (11 ± 1.3) % at 3 keV to (37 ± 12) % at 23 keV; the fractional amplitude of the band-limited noise is energy-independent. This suggests different sites of origin for these two phenomena. The spectrum of the oscillating flux roughly corresponds to a black body with temperature (1.56 ± 0.2) keV and radius ( 500 ± 200) m (other models fit as well), which might indicate the oscillations originate at a small region on the neutron star surface.